TMS320F240 BPRA077 TLE2141 IRGPC40F EVMF240 SPRU160A SPRU161A BPRA044 BPRA043 - Datasheet Archive

 

using a single line resistor on the TMS320F240 Literature Number: BPRA077 Texas Instruments Europe May 1998 IMPORTANT NOTICE

 

Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 Literature Number: BPRA077 BPRA077 Texas Instruments Europe May 1998 IMPORTANT NOTICE Texas Instruments (TI) reserves the right to make changes to its products or to discontinue any semiconductor product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. TI warrants performance of its semiconductor products and related software to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Certain applications using semiconductor products may involve potential risks of death, personal injury, or severe property or environmental damage ("Critical Applications"). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED, OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT APPLICATIONS, DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. Inclusion of TI products in such applications is understood to be fully at the risk of the customer. Use of TI products in such applications requires the written approval of an appropriate TI officer. Questions concerning potential risk applications should be directed to TI through a local SC sales office. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards should be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or services described herein. Nor does TI warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. Copyright © 1998, Texas Instruments Incorporated Contents Contents 1. Introduction. 1 2. Measurement Process. 1 2.1 Measurement process . 2 2.2 Hardware considerations . 4 2.3 Hardware limitations . 5 2.4 Solution to circumvent the hardware limitations. 5 2.5 Enhanced algorithm. 8 3. Hardware sensor . 10 3.1 Schematic . 10 3.2 Cost comparison. 11 3.2.1 Three shunts on each inverter leg . 11 3.2.2 Isolated phase sensors. 12 4. Software Implementation . 12 4.1 Implementation of the first solution . 12 4.2 Implementation of the advanced method . 16 5. Other solutions found in the literature . 18 5.1 Principle . 18 5.2 Performance comparison. 19 6. Results. 20 6.1 Hardware configuration. 20 6.2 First method. 20 6.3 Second method tested . 22 6.4 Closed loop control with the second method . 23 6.5 Speed limitation . 24 7. Conclusion. 26 References . 27 Appendix A: Linker command file . 28 Appendix B: User interface Quick Basic program. 29 Appendix C: Software program describing the first method. 32 Appendix D: Software program describing the second method . 49 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 iii Contents List of Figures Figure 1: Schematic of a system including power, control and load. 1 Figure 2: Schematic diagram of the inverter module. 2 Figure 3: Inverter supplying a net of three star windings. 3 Figure 4: Signals controlling the upper transistors . 4 Figure 5: Plot1,2,3: PWM signals - Plot4: Idc current. 5 Figure 6: 3 Symmetrical PWMs with & without addition of weight. 6 Figure 7: Line current, only one current is detectable . 7 Figure 8: 2 currents detectable on the DC line. 8 Figure 9: Phase current detectable when needed. 9 Figure 10: Three bridges inverter with Idc measurement . 10 Figure 11: Basic schematic for Idc current measurement . 11 Figure 12: Current measurement using three shunts. 12 Figure 13: PWM generation related to the time in the case of a symmetric PWM . 13 Figure 14: V/f control and Idc current measurement block diagram. 16 Figure 15: Synchronisation diagram of the control. 16 Figure 16: Flowchart of the Period interrupt: PR_int . 17 Figure 17: Meas_pattern function flowchart . 18 Figure 18: 11 % sensed an built current comparison . 21 Figure 19: 15 % sensed an built current comparison . 22 Figure 20: The perturbation of the measurement process decreased by five . 23 Figure 21: FOC with shunt measurement . 24 Figure 22: FOC with shunt measurement at high speed . 25 Figure 23: FOC with shunt measurement at very low speed. 26 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 iv BPRA077 BPRA077 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 ABSTRACT Most inverter control systems require a knowledge of the phase currents. The simplest method of obtaining these currents is to measure them directly. Depending on the motor winding connections, this requires at least two sensors to be applied directly to the motor phases. Usually, these types of sensors are expensive due to their need to be isolated. There is a second method of measuring these phase currents using a simple, cheap resistor. However, under certain conditions, the measurement becomes difficult and even impossible due to hardware limitations. In this paper, a solution is described for circumventing this problem and results are given following its implementation on a Digital Signal Processor, the TMS320F240 TMS320F240 from Texas Instruments. 1. Introduction Most three phase motor control algorithms require that the motor phase currents be known in order to deliver high motor performance. The following system recombines the three phase currents of the motor using only one simple resistive sensor. Ia 220V Inverter Ib Ic 6 Idc motor Switching states DSP Figure 1: Schematic of a system including power, control and load 2. Measurement Process In order to control most inverter systems it is necessary to know all the phase currents. The most basic method of obtaining these currents is to measure each of them directly but, depending on the motor winding connections, this requires at least two sensors to be applied directly to the individual motor phases. These types of sensors are usually sophisticated and expensive, as they need to be isolated. A second, but more complex, Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 1 BPRA077 BPRA077 method is to measure only the DC line current and then recombine the 3 phase currents using the inverter switching states. This second method requires only a simple cheap, resistive sensor. As the inverter's switching state is controlled by the Digital Signal Processor, it is possible to know the exact electrical route taken by the input current through the inverter. We can thus directly relate the phase currents to the line current, as shown in the following schematic diagram. Sa Sb Sc Ia Udc Ib Motor Ic Sa Sb Sc Idc Figure 2: Schematic diagram of the inverter module The phase currents we obtain are due to a real measurement of the current and are not the result of a simulation requiring a model of the output circuit. The estimator presented here is independent of the output load of the inverter. It may be used to control a motor but can also be part of a UPS system or any other system requiring the control of phase currents. 2.1 Measurement process For a better understanding of the measurement process, and to represent the switching state of the inverter, we define a switching function Sa for phase A as follows: Sa = 1 when the upper transistor of phase A is on, and Sa = 0 when the lower transistor of phase A is on. Similar definitions can be made for phases B and C. Note: 1. The explanation of the process is based on the assumption that the inverter is fed in complementary mode. In this mode, the signals Sa, Sb, Sc controlling the lower transistors, are the opposite of Sa, Sb, Sc controlling the upper transistor. A similar current measurement could be applied to a non- complementary control. 2. Dead-band is the name given to the time difference between the commutations of the upper and lower transistors of one phase. These two transistors must never conduct at Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 2 BPRA077 BPRA077 the same time. The aim of the dead-band is to protect the power devices during commutation by avoiding conduction overlap which would result in a high current transient. In the notation, the dead-band is not present, the power devices are considered perfect. During implementation phase this time must be taken into account. The stator currents can then be expressed as follows depending on the switching states: idc = ia idc = -ia idc = ib idc = -ib idc = ic idc = -ic idc = 0 idc = 0 when (Sa, Sb, Sc) = (1,0,0) when (Sa, Sb, Sc) = (0,1,1) when (Sa, Sb, Sc) = (0,1,0) when (Sa, Sb, Sc) = (1,0,1) when (Sa, Sb, Sc) = (0,0,1) when (Sa, Sb, Sc) = (1,1,0) when (Sa, Sb, Sc) = (1,1,1) when (Sa, Sb, Sc) = (0,0,0) The following figure gives an example of the switching state: (Sa, Sb, Sc) = (0,0,1) where idc = + ic. 1 Udc 3 U 2 5 V 4 W 6 Shunt IDCOUT ~UDCOUT Figure 3: Inverter supplying a net of three star windings Based on the above equations, one phase current (Ic) can be related directly to the dc line current. Therefore, all three-phase currents can be measured by looking only at the dc line. If the Pulse Width Modulation period frequency is high enough, the phase current will only vary slightly over one or two PWM periods. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 3 BPRA077 BPRA077 2.2 Hardware consideratio ns Two times are defined as follows. u1 is the time gap between the transistor commutation on the first phase and the commutation of the equivalent transistor in the next phase within the first half of the PWM period. Similarly u2 is the time difference between the commutations on the second and third phases. Figure 4: Signals controlling the upper transistors In the case of symmetrical PWM generation, the first half period of the PWM starts with the state (0,0,0), followed by two states (u1 and u2) where at least one of the upper transistors is on, and finishes with the state (1,1,1). The second half of the PWM period consists of the same state sequence in reverse order . 1. It is not possible to make any measurement during the states (0,0,0) and (1,1,1) as no current is flowing in the dc line. A maximum of two different phase measurements can be made during any one PWM period. 2. Thus line current measurements made during times u1 and u2 will generate two different phases. The third current is deduced using the formula: ia+ib+ic=0, in the case of a star or a triangle winding structure. In the previous example, during time u1 the inverter state is (0,0,1) and so the measured phase current is ic=idc . Similarly during time u2, the inverter state is (1,0,1) and so ib =-idc . Since ib and ic have been calculated it follows that ia=-(ib+ic). Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 4 BPRA077 BPRA077 Figure 5: Plot1,2,3: PWM signals - Plot4: Idc current 2.3 Hardware limitations Under certain conditions the periods u1 or u2 are very short. In this case, due to the transistor commutation times, dead-bands and response delays of the processing electronics, the actual phase current is invisible on the line current. As a result it is not possible to estimate the phase currents from the line current under these circumstances. The method described in the next paragraph provides a solution which circumvents this hardware limitation and allows more accurate measurement of the phase currents than previous methods do. This improvement enables the motor to operate over a wider range of speeds and motor loads. 2.4 Solution to circumven t the hardware limitations To help explain the solution of the problem, an artificial PWM pattern signal is generated. This signal is shown in the next graph and is the result of the addition of the three weighted upper transistor switching signals (PWM). The three PWM signals are indexed with 1, 2 and 4 respectively. At any one instance the switching state of the six transistors can be deducted from the PWM pattern. The Figure 6 shows: · Plot2-3-4: 3 symmetrical PWMs, · Plot1: the 3 PWMs are added with addition of weight Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 5 BPRA077 BPRA077 PWM Period Figure 6: 3 Symmetrical PWMs with & without addition of weight The problem is that it is not possible to measure the phase currents during a short u1 and u2 (in the range of few hundreds of nanoseconds to a few micro-seconds). The Figure 7 shows: · Plot 1: 3 PWM patterns, u1 = 12µs, u2 = 1.5µs · Plot 2: Line current, only one current is detectable Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 6 BPRA077 BPRA077 u2 u1 Figure 7: Line current, only one current is detectable One of the methods to solve this problem and allow both measurements is to force the short period ( here u2 ) to the minimum measurement time1 imposed by the chosen hardware. In this case u2 is changed to u2measure = 4µs. The solution is to lengthen the required section of the pattern for one PWM period in order to make the measurement possible and compensate for it by generating shorter patterns during the PWM periods where no measurements are made. Let us consider the example of a controller with a cycle time of 80µs. The PWM has also a carrier frequency of 12.5kHz (80µs). Therefore during one control cycle, one PWM pattern is generated. In our example, the hardware imposes a minimum time of 4µs between two consecutive switching states in order to make an accurate measurement. The problem can be illustrated in the situation where, for a given speed and load, the control algorithm calculates, at a time t, time differences between PWM commutations of u1 = 12us and u2 = 1.5us respectively. The first time difference will allow a valid current measurement but the second one will not. The Figure 8 shows: · Plot 1: 3 PWM patterns, u1 = 12µs, u2measure = 4µs · Plot 2: Line current 1 TI-patent pending Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 7 BPRA077 BPRA077 Figure 8: 2 currents detectable on the DC line On the above plot the two phase currents are detectable and can be measured. 2.5 Enhanced algorithm This simple modification algorithm described above may be used in most systems. However, this artificial modification of the PWMs will result in modified currents being applied to the motor, giving poor control of the stator flux. This poor control of the flux will result in more power being applied to the motor than is required thus reducing its efficiency as well as leading to more torque ripple. For systems that often work at these limit conditions or where the best current shape for torque ripple control is required, an enhanced solution is proposed. In most controllers the main control cycle frequency is lower than the PWM frequency. The control will then generate several identical PWM patterns for every control cycle phase current update. The enhanced algorithm overcomes the drawbacks of the simple modification method described above and can apply the theoretical phase signals calculated by the controller to the motor. It works by adapting the PWM patterns as required in order to meet any minimum periods required to make a measurement. During the measurement period, the PWM patterns signals will be adapted to correspond to the hardware's minimum time criteria. Similarly, during the remaining PWM periods when no measurements are made the PWM patterns will be compensated2 throughout the controller cycle time to generate the correct mean phase currents in the motor. 2 TI-patent pending Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 8 BPRA077 BPRA077 If we refer back to our example and extend the control cycle time from 80µs to 500µs (but not the PWM period), five PWM patterns of 80µs will be calculated by a single controller cycle. During the measurement period, u2 is modified to u2measure = 4µs and u1 remains equal to 12µs. The four other PWM patterns are then modified to compensate for the extra energy generated by this measurement pattern, by having a time delay u2compensate equivalent to: 4u2 compensate + u2 measure = 5u2 u2 compensate = 5 × 1.5 - u2 measure 4 = 875ns u1 remains the same. The following graph illustrates this example, when (u1, u2measure) is generated, a peak appears on the line current, this is the desired current. During (u1, u2compensate) no measurement is possible as the time between two switching states is too low for the hardware used in the application. The Figure 9 shows: · Plot 1: PWM pattern, u1 = 12µs, u2meas = 4µs, u2comp = 875ns · Plot 2: Line current u2measure u2compensate Figure 9: Phase current detectable when needed In the above plot the two phase currents are detectable only when needed. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 9 BPRA077 BPRA077 3. Hardware sensor 3.1 Schematic The inverter considered in the application note has three legs. The load is modelled by an AC motor with the assumption that Ia+Ib+Ic = 0. The shunt is placed in the circuit so that the current going into and out of the inverter flows across it. An Operational Amplifier scales the shunt terminal voltage to fit the input voltage of the 'F240 Analogue Digital converter which has a maximum range of 0-5V. AC ~ Vdc T1 T3 T5 T4 T6 T2 Shunt resistor Feedback gain ADC Module Figure 10: Three bridges inverter with Idc measurement The additional circuitry required to sample the current from the DC line consists of: 2 · a shunt resistor whose value depends on two factors. A low dissipated power RI and a voltage Vshunt high enough to get a reasonable ADC scaling gain. For instance, a phase current range of [-10,10] Amps with an AOP gain of 10 requires a shunt of 25 m to get an AD input in the range of [0,5] Volts. This shunt will have to dissipate a maximum of 2.5 Watt. · an operational amplifier with a bandwidth high enough to see the Idc current transitions. As an indication, the AOP bandwidth used in the example described previously to detect an Idc current lasting 4µs was 1MHz, · An other requirement is to create an offset voltage of 2.5V for the A/D converter input in order to scale the AD input in the range 0-5V, Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 10 BPRA077 BPRA077 · If the AOP supply is 15V, a clamp diode has to be added to limit AD input voltage to 5V. The following schematic gives an example of a basic circuit to scale the current from the shunt resistor, where: R ADinput = 2 (Vshunt ) + 2.5 R1 V Shunt R2 R1 - + R1 4148 5v 15v AD input TLE2141 TLE2141 330 15v 6R2 2.5v 6R2 5 Figure 11: Basic schematic for Idc current measurement The precision of the resistors will determine the accuracy of the conversion. 3.2 Cost comparison Other solutions may be considered to measure the phase currents. The costs ratio of other solutions are compared below. 3.2.1 Three shunts on each inverter leg This method consists of using three shunts to measure the currents flowing in each of the three inverter legs. The measurement is then possible at any time, except during free wheeling. This solution requires three circuits comparable to the solution described in the previous paragraph. The cost will be three times higher. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 11 BPRA077 BPRA077 AC ~ T1 T3 T5 T4 T6 T2 Figure 12: Current measurement using three shunts A solution with two shunts could also be used, the third current being deduced from the two current samples. 3.2.2 Isolated phase sensor s Another solution commonly found in industry today is to sense the phase currents directly. 1. two shunts are used on the phases. This requires two isolated AOPs and twice the scaling circuit for AD input, 2. two isolated Hall Effect sensors are placed on the motor phase currents. Again, the cost of two scaling circuits must be added on top of the cost of the isolated sensors. The ratio between the prices of the two implementations is greater than four. This ratio grows as the power increases. 4. Software Implementation 4.1 Implementation of the first solution The software implemented on the TMS320F240 TMS320F240 evaluation module may use any kind of control and load with the condition that ia+ib+ic = 0. For demonstration purposes, the effects of the algorithm are best seen when simply observing the phase currents on an open-loop system. Consequently if any disturbance occurs on the current due to the current measurement process it will not be corrected by the control. For this reason a voltage/frequency open-loop control is considered with an AC induction drive as a load. As a conclusion, an example of a closed-loop control using the sampled currents will be demonstrated. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 12 BPRA077 BPRA077 The software ensures that all the time gaps u1 and u2 reach a minimum time called Mingap. Two current conversions will be done during each PWM period in order to calculate the three currents flowing in the inverter phases. The solution uses minimal CPU time. Most of the functions required to get the phase currents from a single shunt resistor are performed asynchronously from the DSP core, as a result of an optimum use of the 'F240 Event Manager. The implemented solution uses · 1 timer and 6 PWM from the full compare for the control. · 1 A/D channel. · 1 PWM from a second timer for the synchronisation of the ADC conversions which are done automatically on the timer compare match. · 1 interrupt on the full compare period underflow event to synchronise the control. · All registers are reloaded synchronously with the control cycle. To generate the PWM, the timer T1 is used and counts successively in Up and Down modes (symmetric mode). An interrupt, called PR_int, occurs at the end of every Down mode. Timer underflow mode PR_int Timer Overflow mode Up_mode Down_mode Measurement Measurement PR_int Timer Sa Sb Sc 000 100 110 111 111 110 100 000 Load New values for PWMs u1 u2 PWM Period Figure 13: PWM generation related to the time in the case of a symmetric PWM The register T1PER contains the period of the PWM. The measurements are made using the Analogue to Digital converters. Only one channel is used in the software: Channel 2 (ADC1CHSEL = 001). It is connected to IDC channel. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 13 BPRA077 BPRA077 The starts of conversions are synchronised with the PWMs, on the compare register match. It does not require any CPU load due to the TMS320C24x event manager. For more flexibility the conversions are started on the PWM compare of Timer 3. Its period is the same as T1, but its time base is shifted by a time called `delay' (T1CNT = T3CNT + delay). This adjustment is made to compensate for the response time between the PWM command and the moment Idc current actually switches. This software delay is implemented for ease of adaptation to any hardware and avoids the use of any glue logic. The `delay' can be adjusted at start up through the user interface. The process for adapting it is to visualise T3PWM together with the DC current while modifying the variable. When they are synchronised the value of delay can be set as default value. This parameter is dependent on the hardware and once determined, it doesn't need to be changed. N.B. `Delay' is taken into account only during the software initialisation at start-up. Consequently, each time the variable `delay' is modified through the user interface, the DSP must be reset while running so that the change can be operative. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 14 BPRA077 BPRA077 PR_int Save context Get samples converted from previous period store them in i_remote1 and i_remote2 scale the currents buffer previous sector into sectorold sort the currents into i1 & i2 calculate open loop voltage Valfa & Vbeta axis transformation to Va, Vb, Vc calculation of sector calculation of t1 & t2 t1 & t2 increased to the minimum value of Tonmax saturation of t1+t2 to PWMPR-2*Tonmax software space vector, calculation of taon, tbon, tcon output sent to Full compare registers (CMPR) update T3CMP to synchronize ADC conversions for next period start Idc conversions output DAC1 to DAC4 restore context Return to main Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 15 BPRA077 BPRA077 Figure 14: V/f control and Idc current measurement block diagram 4.2 Implementation of the advanced method The control in this example is performed once every five PWM periods. Then only two Idc measurements are required to get the phase currents every five PWM periods. To enable the synchronisation of the control, PR_int sets a flag every five PWM periods to implement the controller. At the end of the control cycle time, PR_int calculates the measurement pattern defined by u1measure and u2measure (u1meas and u2meas in the flowcharts). The current measurement is taken during the period preceding the control. One control cycle time PR_int0 PR_int1 PR_int2 PR_int3 PR_int4 PR_int0 t Process new currents Measurement Process new currents Measurement Control Algorithm Control Algorithm Measurement Figure 15: Synchronisation diagram of the control Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 16 BPRA077 BPRA077 PR_int Save context 0 Period interrupt Occurs in timer We are inside an interrupt, context must be saved Synchro 4 3 Get current send measurement pattern for next PWM send compensated pattern for next PWM send_to_PWM send_to_PWM Control V/f send compensated pattern for next PWM send_to_PWM Increment Synchro by 1 [modulo 5] Restore context Return main program Figure 16: Flowchart of the Period interrupt: PR_int Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 17 BPRA077 BPRA077 Meas_pattern Mingap is the minimum time yes no u1 < Mingap u1comp = max[(5u1-Mingap)/4,0] u1meas = Mingap u1comp = u1 u1meas = u1 no no u2 < Mingap u1meas+u2 > Period/2 Check if after increase u1meas u1meas + u2 < (PWM period)/2 yes yes u2comp = u2 u2meas = u2 u1comp compensates u1meas | 4u1comp = 5u1 - Mingap | u1comp > 0 u2comp = max[(5u2-Mingap)/4,0)] u2meas = Mingap u2meas = Period - Mingap u2comp = u2 If u1meas + u2 is not in the PWM range then u2meas is decreased u1+u2meas > Period/2 u1meas = Period - Mingap u1comp = u1 Return Figure 17: Meas_pattern function flowchart 5. Other solutions found in the literature 5.1 Principle Another method found in the literature consists of generating one pattern during one control cycle time (in the example: 250µs). The line current is then continuously sampled (every 15.6µs) and sorted according to the inverter state to update a stack containing the measured phase currents. With all the samples obtained, averages are taken to give each phase current. As the sampling is performed at fixed-time, some small patterns (less than 30µs) may not be detected. To circumvent these undetectable signals, a zero duty cycle will be used for the first PWM and the theoretical PWM will be accumulated to the next period duty cycle Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 18 BPRA077 BPRA077 of the same vector. This process continues until the accumulated duty cycle exceeds 30µs. As the samples are not synchronised to the inverter states, ensuring the line currents match the correct states requires a large minimum duty cycle (here: 30µs). 5.2 Performance compari son Let us compare the performances of the above two methods for a 450W, two pair poles, asynchronous motor at a speed of 150rpm with an empty drum as a load and a voltage supply of 270V. This speed and load represent the worst case for our defined hardware. The maximum PWM (time gap between two switching states) we can detect, due to our hardware limitations is 2.8µs. Let us now consider that we have to generate an energy inside the motor corresponding to un with n [1,2] , equal to 2.8µs over 400µs. The second method described in this application report is called the `compensated solution'. It will be possible to measure the current during every control cycle, by generating one pattern with un_measure=2.8µs and four others with un_compensate=0. To keep the same ratio for both methods (they have different control cycle times), the energy corresponding to 2.8µs over 400µs is 1.75µs over 250µs. The sampling rates for these two methods for this low speed and low load condition are given below. To acquire a sample, the standard method requires a minimum duty cycle of 30µs. To get the performance described above, the register has to accumulate (abs(30/1.75)+1=) 18 times the energy over 250µs. The control will then acquire a sample every 18x250=4.5ms. In the same conditions the `compensated solution' will get a sample every 400µs. The sampling rate is then 10 times higher in our solution. The hardware used in this case has a dead-band of 1.2µs but already some higher speed range inverters are able to switch off in less than 150ns and have drivers able to generate a dead-band of few hundreds of nanoseconds. Therefore, it is possible that existing devices will reach a PWM equals to less than 500ns. The performance of the `compensated solution' over the classic solution is increased by the same ratio. All these calculations have been performed for a specific application. The above figures and ratios may be very different for another application, but in every case the results of our measurement will remain more accurate than that of the classic solution. Advantages of the `compensated' solution: · This is a synchronous method, therefore all the algorithms can be used with a constant time base and this is the basis for all control algorithms · It provides a smooth control for low speed and low load and therefore a better efficiency · As the exact current sampling time is known it is necessary to take only one sample. To obtain the final measured current it is not necessary either to calculate an average of the samples or to make a filter to reduce the effects of wrong state Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 19 BPRA077 BPRA077 · latching. Therefore, there is a saving of calculation time needed to measure the currents. It is possible to control a motor over a very wide range of speeds and loads with performance 10 times higher than usual methods. 6. Results 6.1 Hardware configuratio n The results are given on a board using an inverter from International Rectifier. The inverter is made of six IGBT IRGPC40F IRGPC40F with · max. continuous collector current of 27A · turn-on delay time of 25ns · rise time of 37ns · max. turn-off delay time of 410ns · max. fall timer of 420ns The driver, an IR 2130, has a dead-band of 2µs. The minimum time during which it's possible to make the measurement is 3.5µs. 6.2 First method This method gives good results for most of the cases. The best results are achieved with currents close to their nominal values. In the application, the maximum value for sampling current is in the range of +/-10 Amps. The following results are obtained for a phase current equal to 11% of the detectable current, the next plot is made for a ratio of 17%. These plots are obtained without any software filter, only a smoothing filter from the oscilloscope has been used to suppress the measurement noise from the probe. The Figure 18 shows: · Plot 1: 11% phase current calculated with control · Plot 2: measured phase current through Hall effect sensor Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 20 BPRA077 BPRA077 Figure 18: 11 % sensed an built current comparison Plot1 is output through a digital to analogue converter included in the EVMF240 EVMF240. Comparing its maximum re-scaled value to the real phase current from the Hall Effect sensor, they are both equal. Looking more into details, some non-linearities appear on the plots. Most of them are due to the measurement process that forces some PWM patterns to minimum values as explained in chapter "Solution to circumvent the hardware limitations". On the other hand, the spikes present on both the rebuilt current and the measured phase currents illustrate the dynamic of the process and the lack of filtering. The Figure 19 shows: · Plot 1: 15% phase current calculated with control 1 · Plot 2: measured phase current through Hall effect sensor Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 21 BPRA077 BPRA077 Figure 19: 15 % sensed an built current comparison It can be observed that for a higher current the measured phase current is more sinusoidal. The ratio of current for which the current may be considered as sinusoidal varies depending on the inverter used. If lower ratios of current detected are needed, more advanced inverters may be considered. 6.3 Second method tested The following plot illustrates the process described in the chapter "2.5 Enhanced algorithm". Its comparison with the previous plots from the first method shows that for the a current ratio of 14% non-linearities due to the minimum pattern imposed can hardly be detected. The Figure 20 shows: · Plot 1: 14% phase current calculated with control 2 · Plot 2: measured phase current through Hall effect sensor Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 22 BPRA077 BPRA077 Figure 20: The perturbation of the measurement process decreased by five One measurement is performed every five PWM. The perturbation of the measurement process is then decreased by five. 6.4 Closed loop control w ith the second method The previous plots were taken with a V/f control. As the voltage is maintained constant, the perturbations are observed on the current, and therefore on the torque. If a current control is applied, it is possible to get a perfect sinusoidal current together with the `reduced current sensor' algorithm. The next plot has been measured with the same hardware but the AC induction motor is controlled with a Field Orientated Control Algorithm. The Figure 21 shows: · Plot 1: measured phase current through Hall Effect sensor · Plot 2: calculated phase current at 300rpm (nominal speed: 1500rpm) Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 23 BPRA077 BPRA077 Figure 21: FOC with shunt measurement The measured current is obtained here without any filtering or interpolation. 6.5 Speed limitation The measurement method presented in the application note doesn't impose any constraint of speed range. The only magnitude that limits the use of the idc current measurement is the ratio between the actual current and the nominal current. The speed range is limited only by the controller capability. The Figure 22 shows: · Plot 1: calculated current / 4700rpm · Plot 2: phase current sensed 10mA1A Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 24 BPRA077 BPRA077 Figure 22: FOC with shunt measurement at high speed The above plot shows the effect of the controller cycle time on the current. The current samples perfectly match the real phase current. The Figure 23 shows: · Plot 1: calculated current / 2.2 rpm · Plot 2: phase current sensed 10mA1A Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 25 BPRA077 BPRA077 Figure 23: FOC with shunt measurement at very low speed Low speed is also not a limitation to the current measurement as soon as the current is high enough. 7. Conclusion The algorithm and its high performance have increased the utility of the DSP in motor control. The performance can increase in terms of torque and speed control by using efficient control algorithms with current feedback at a similar price to that of existing lower performance solutions. This method is applicable to most synchronous and asynchronous motor drives, or, more generally, to three phase inverters. This technique is useful in the White Goods, inverter and machine tools market. Texas Instruments has a U.S. patent pending on some of the topics described in this application note. Serial number: 08/903,110. Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 26 References References 1. TMS320C24x DSP Controllers, Reference sets 1997 Texas Instruments ref. SPRU160A SPRU160A & SPRU161A SPRU161A 2. Current detection method for DC to three-phase converters using a single DC sensor, U.S. patent application 5,309,349, K.S. Kwan, 1992 3. Current estimator for a three phase inverter, U.S. Patent application 08/903,110, Texas Instruments, M. Platnic, 1997 4. A stator Flux-Oriented Voltage Source Variable-Speed Drive Based on dc Link Measurement, Xue, Xu, Habetler, Divan, 1991 IEEE 5. A Low Cost Stator Flux Oriented Voltage Source Variable Speed Drive, Xue, Xu, Habetler, Divan, University of Wisconsin-Madison, 1990 IEEE 6. DSP Solution for Permanent Magnet Synchronous Motor, Texas Instruments, Application report 1996 ref. BPRA044 BPRA044 7. DSP Solution for AC Induction Motor, Texas Instruments, Application report 1996, ref. BPRA043 BPRA043 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 27 Appendix A: Linker command file Appendix A: Linker command file /*/ /* TEXAS INSTRUMENTS */ /*/ /* File Name: link.cmd */ /* Originator: Michel Platnic */ /* */ /* Description:Link command file */ /* MEMORY SPECIFICATION FOR THE EVMF240 EVMF240 FROM TEXAS INSTRUMENTS */ /* Block B0 is configured as data memory (CNFD) and MP/MC- = 1 */ /* (microprocessor mode). Note that data memory locations 6h-5Fh*/ /* and 80h-1FFh are not configured. */ /* */ /* Target: TMS320F240 TMS320F240, EVMF240 EVMF240 */ /* status: Working */ /* */ /* History: Completed on 28 November 97 */ /*/ MEMORY { PAGE 0: FLASH_VEC FLASH PAGE 1: REGS BLK_B22 BLK_B0 BLK_B1 EXT_DATA : origin = : origin = : : : : : origin origin origin origin origin = = = = = 0h, length = 040h, length = 0h, 60h, 200h, 300h, 8000h, length length length length length = = = = = 40h 03FC0h 60h 20h 100h 100h 1000h } /*-*/ /* SECTIONS ALLOCATION */ /*-*/ SECTIONS { vectors : { } > FLASH_VEC PAGE 0 /* INTERRUPT VECTOR TABLE */ .text : { } > FLASH PAGE 0 /* CODE */ blockb2 : { } > BLK_B22 PAGE 1 /* CONTEXT SAVE */ .bss : { } > EXT_DATA PAGE 1 /* GLOBAL VARS, STACK, HEAP*/ .data : { } > EXT_DATA PAGE 1 /* VARIABLES */ table : { } > EXT_DATA PAGE 1 /* SINE TABLE */ } Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 28 Appendix B: User interface Quick Basic program Appendix B: User interface Quick Basic program REM REM REM REM REM REM REM REM REM REM REM REM * * TEXAS INSTRUMENTS * * * File Name: open_spe.bas * * Originator: Michel Platnic * * Description:User Interface on Quick Basic * * * * Function list: No function, linear software * * Target: TMS320F240 TMS320F240, EVMF240 EVMF240 with 4 DAC use * * * * History: Completed on 28 November 97 * * OPEN "COM1: 9600,N,8,1,CD0,CS0,DS0,OP0,RS,TB1,RB1" FOR OUTPUT AS #1 PRINT #1, "1"; CHR$(0); CHR$(0); : REM speed reference initialization to 0 PRINT #1, "2"; CHR$(0); CHR$(1); CHR$(2); CHR$(3); : REM DAC initialization delay = 10 Mingap = 80 est = 0 speedref = 0 init = 0 VDC = 310 da1 = 0: da2 = 1 da3 = 18: da4 = 24 speedpu = 1500: REM base speed DIM daout$(200) daout$(0) = "i1" daout$(1) = "i2" daout$(2) = "i3" daout$(3) = "i_remote1" daout$(4) = "i_remote2" daout$(5) = "i_remote3" daout$(6) = "u1" daout$(7) = "u2" daout$(8) = "seno1" daout$(9) = "coseno" daout$(10) = "Va" daout$(11) = "Vb" daout$(12) = "Vc" daout$(13) = "VDC" daout$(14) = "taon" daout$(15) = "tbon" daout$(16) = "tcon" daout$(17) = "teta" daout$(18) = "Valfar" daout$(19) = "Vbetar" daout$(20) = "speedr" daout$(21) = "X" daout$(22) = "Y" daout$(23) = "Z" daout$(24) = "sector" daout$(25) = "sectorold/synchro" nDA = 8 1 CLS Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 29 Appendix B: User interface Quick Basic program FOR i = 0 TO nDA COLOR 11 LOCATE (15 + i), 2: PRINT "("; : PRINT USING "##"; i; : PRINT ") "; daout$(i) LOCATE (15 + i), 29: PRINT "("; : PRINT USING "##"; i + nDA + 1; : PRINT ") "; daout$(i + nDA + 1) LOCATE (15 + i), 56: PRINT "("; : PRINT USING "##"; i + 2 * nDA + 2; : PRINT ") "; daout$(i + 2 * nDA + 2) NEXT i LOCATE 2, 11 COLOR 12: PRINT " Digital Control of an AC Induction Motor using V/f" LOCATE 3, 7 COLOR 12: PRINT "Demo for 3 phase currents measurement with one shunt resistor" PRINT PRINT COLOR 10: PRINT " "; : COLOR 2: PRINT " Speed_reference ("; speedref; "rpm )" COLOR 10: PRINT " "; : COLOR 2: PRINT " DAC_Outputs DAC1: ("; daout$(da1); ")" LOCATE 7, 48: PRINT "DAC2: ("; daout$(da2); ")" PRINT " DAC3: ("; daout$(da3); ")" LOCATE 8, 48: PRINT "DAC4: ("; daout$(da4); ")" COLOR 10: PRINT " "; : COLOR 2: PRINT " Delay (*50ns) ("; delay; ")" COLOR 10: PRINT " "; : COLOR 2: PRINT " Mingap (*50ns) ("; Mingap; ")" COLOR 10: LOCATE 12, 14: PRINT "Choice : "; DO a$ = INKEY$ LOOP UNTIL (a$ = "1") OR (a$ = "r") OR (a$ = "R") SELECT CASE a$ CASE "1" REM 4.12 format PRINT a$; ") "; PRINT "Speed_Reference ("; speedref; "rpm ) : "; INPUT speedref$ IF speedref$ = "" THEN 1 speedrpu = VAL(speedref$) / speedpu IF (ABS(speedrpu) > 1.2) THEN speedrpu = 1.2 * SGN(speedrpu) IF (speedrpu >= 7.999755859#) THEN speedrpu = 7.999755859# IF (speedrpu Tc=2*896*50ns=89.6us (50ns resolution) Mingap .word 80 ;minimum PWM duty cycle ;the MAXDUTY is calculated as PWMPRD-2*Mingap ;it is the maximum utilisation of the inverter delay .word 10 ;delay for Idc measurement zero .word 0h MAX .set 736 .bss .bss .bss .bss .bss tmp,1 option,1 daout,1 daouttmp,1 tetaad,1 ;temporary variable (to use in ISR only !!!) ;virtual menu option number ;address of the variable to send to the DACs ;value to send to the DACs ;teta openloop variable * DAC displaying table starts here .bss i1,1 ;phase current i1 .bss i2,1 ;phase current i2 .bss i3,1 ;phase current i3 .bss i_remote1,1 ;first of the 2 idc currents .bss i_remote2,1 ;second of the 2 idc currents .bss i_remote3,1 ;sum of the 2 idc currents negated .bss u1,1 ;SVPWM T1 (see SV PWM references for details) .bss u2,1 ;SVPWM T2 (see SV PWM references for details) .bss seno1,1 ;generated sine wave value .bss coseno,1 ;generated cosine wave value .bss Va,1 ;Phase 1 voltage .bss Vb,1 ;Phase 2 voltage .bss Vc,1 ;Phase 3 voltage .bss VDC,1 ;DC Bus Voltage .bss taon,1 ;PWM commutation instant phase 1 .bss tbon,1 ;PWM commutation instant phase 2 .bss tcon,1 ;PWM commutation instant phase 3 .bss teta,1 ;rotor electrical position in the range [0;1000h] ;4.12 format = [0;360] degrees .bss Valfar,1 ;alfa-axis reference voltage .bss Vbetar,1 ;beta-axis reference voltage .bss speedr,1 ;speed reference .bss X,1 ;SVPWM variable .bss Y,1 ;SVPWM variable .bss Z,1 ;SVPWM variable .bss sectordisp,1 ;SVPWM sector for display Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 33 Appendix C: Software program describing the first method .bss sectorold,1 ;SVPWM sector buffer for current measurement * END DAC displaying table .bss sector,1 ;SVPWM sector .bss serialtmp,1 ;serial communication temporary variable .bss da1,1 ;DAC displaying table offset for DAC1 .bss da2,1 ;DAC displaying table offset for DAC2 .bss da3,1 ;DAC displaying table offset for DAC3 .bss da4,1 ;DAC displaying table offset for DAC4 .bss VDCinv,1 ;1/VDC 4.12 format .bss VDCinvTc,1 ;VDCinv*(Tc/2) (used in SVPWM) .bss tetaincr,1 ;V/f open loop tetaincr (1pu speed) .bss Vamplitude,1 ;V/f open loop Vamplitude .bss indice1,1 ;pointer used to access sine look-up table .bss tmp1,1 ;tmp word to convert to C24 .bss accb,2 ;2 words to replace ACCB in C24 .bss acc_tmp,2 ;2 words to allow swapping of ACC in C24 .bss tetaref,1 * END Variables and constants initializations .text ;link in "text section * * _PR_int ISR * * synchronisation of the control algorithm with the PWM * * underflow interrupt * * _PR_int: larp ar4 ;context save mar *sst #1,*;status register 1 sst #0,*;status register 0 sach *;Accu. low saved for context save sacl *;Accu. high saved ldp #IFRA>>7 splk #07FFh,IFRA ;Clear all flags, may be change with only T1 underflow int. mar *,ar5 ;used later for DACs output * * Current Remote measurement - AD conversions * * N.B. we will have to take only 10 bit (LSB) * * clrc SXM ldp #DP_PF1 lacc ADC_FIFO2 ;empty stack lacc ADC_FIFO2 ; lacc ADC_FIFO1,10 ;10.6 format ldp #i_remote1 sach i_remote1 ;sampled current, f 4.12 ldp #DP_PF1 lacc ADC_FIFO1,10 ;10.6 format ldp #i_remote1 sach i_remote2 ;sampled current, f 4.12 setc SXM ldp bldd bldd ldp splk #tbon tbon,#T1CMP tbon,#T3CMP #DP_PF1 #1803h,ADC_CNTL1;Channel 2 ADC2 selected for idc Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 34 Appendix C: Software program describing the first method ;ADC2 disable ;start spm ldp lacl and sub 3 #i1 i_remote1 #3ffh #512 sacl lt mpy pac sfr sfr sub sacl tmp tmp Kcurrent lacl and sub i_remote2 #3ffh #512 sacl lt mpy pac sfr sfr sub neg sacl spm add neg sacl tmp tmp Kcurrent #00h i_remote1 #00h i_remote2 0 i_remote1 i_remote3 ;then we have to subtract the offset (2.5V) to have ;positive and negative values of the sampled current ;then we subtract a DC offset (that should be zero, but it isn't ;sampled current f 4.12 ;then we have to subtract the offset (2.5V) to have ;positive and negative values of the sampled current ;then we subtract a DC offset (that should be zero, but it isn't ;second current always negative with the convention ;sampled current f 4.12 ;third current calculated * * Current Remote measurement * * determination of current measured depending on sector * * lacc sub bcnd sub bcnd bldd bldd b sector45 bldd add bcnd bldd b sector4 bldd b sectorold #3 sector123,LEQ #3 sector45,NEQ i_remote3,#i1 i_remote2,#i2 end_remote ;sector 4,5 or 6 ;sector 6 i_remote2,#i1 #1 sector4,NEQ i_remote1,#i2 end_remote i_remote3,#i2 end_remote sector123 add bcnd bldd ;sector 4 or 5 ;sector 4 #2 sector23,NEQ i_remote1,#i2 ;sector 1,2 or 3 ;sector 5 ;sector 1 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 35 Appendix C: Software program describing the first method bldd b sector23 bldd sub bcnd bldd b sector3 bldd i_remote3,#i1 end_remote i_remote1,#i1 #1 sector3,NEQ i_remote2,#i2 end_remote ;sector 2 or 3 i_remote3,#i2 ;sector 3 ;sector 2 end_remote lacc sector sacl sectorold * * creating reference voltage for induction motor * * mar *,AR5 ldp #tetaref lacc speedr abs sacl Vamplitude lt speedr mpy #126h pac sach tetaincr,4 lacc tetaref add tetaincr sacl tetaref rpt #3 sfr sacl teta rpt #3 sfr and #0ffh ;now ACC contains the pointer to access the table sacl indice1 ; add #sintab ; sacl tmp ; lar ar5,tmp nop nop ; mar *,ar5 lacl * ; nop sacl seno1 ;now we have sine value lacl add and sacl add sacl lar lacc sacl indice1 #040h #0ffh indice1 #sintab tmp ar5,tmp * coseno lt mpy pac coseno Vamplitude sach lt Valfar,4 seno1 ;the same thing for cosine . cos(teta) = sin(teta+90°) ;90 degrees = 40h elements of the table ; ;we use the same pointer (we don't care) ; ; ; ; ;now we have cosine value ;format 4.12 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 36 Appendix C: Software program describing the first method mpy pac sach Vamplitude Vbetar,4 * * Phase 1(=a) 2(=b) 3(=c) Voltage calculation * * (alfa,beta) -> (a,b,c) axis transformation * * modified exchanging alfa axis with beta axis * * for a correct sector calculation in SVPWM * * Va = Vbetar * * Vb = (-Vbetar + sqrt(3) * Valfar) / 2 * * Vc = (-Vbetar - sqrt(3) * Valfar) / 2 * * lt Valfar ;TREG0=Valfar mpy SQRT32 SQRT32 ;PREG=Valfar*(SQRT(3)/2) pac ;ACC=PREG sub Vbetar,11 ;ACC-=Vbetar*2^11 sach Vb,4 ;shift by 12 to reformat pac ;ACC=PREG neg ;ACC=-ACC sub Vbetar,11 ;ACC-=Vbetar*2^11 sach Vc,4 ;shift by 12 to reformat lacl Vbetar ;ACC=Vbetar sacl Va ;Va=ACCL * END Phase 1(=a) 2(=b) 3(=c) Voltage calculation * * SPACE VECTOR Pulse Width Modulation * * (see SVPWM references) * * lt VDCinvTc mpy SQRT32 SQRT32 ;change to dma pac sach tmp,4 ;implement bsar 12 and sacl lt tmp mpy Vbetar pac sach X,4 lacc X ;ACC = Vbetar*K1 sach accb ; sacl accb+1 ;ACCB = Vbetar*K1 sacl X,1 ;X=2*Vbetar*K1 lt VDCinvTc splk #1800h,tmp mpy tmp ;implement mpy #01800h pac sach tmp,4 ;shift by 12 to reformat lt tmp mpy Valfar pac sach tmp,4 lacc tmp ;reload ACC with Valfar*K2 add accb+1 add accb,16 sacl Y ;Y = K1 * Vbetar + K2 * Valfar sub tmp,1 sacl Z ;Z = K1 * Vbetar - K2 * Valfar * 60 degrees sector determination lacl #0 sacl sector lacc Va bcnd Va_neg,LEQ ;If Va2*Mingap we have to saturate u1 and u2 u2 ; tmp ; Mingap,1 ; #PWMPRD nosaturation,LT,EQ * u1 and u2 saturation, lacc #PWMPRD,14 ;divide PERIOD-2MINGAP by (u1+u2) sub Mingap,15 sfl rpt #15 ; subc tmp ; sacl tmp ; lt tmp ;calculate saturate values of u1 and u2 mpy u1 ;u1 (saturated)=u1*(PERIOD-2MINGAP/(u1+u2) pac ; sach u1,1 ; mpy u2 ;u2 (saturated)=u2*(PERIOD-2MINGAP/(u1+u2) pac ; sach u2,1 ; * END u1 and u2 saturation nosaturation * taon,tbon and tcon calculation lacc #PWMPRD ;calculate the commutation instants taon, tbon and tcon sub u1 ;of the 3 PWM channels sub u2 ;taon=(PWMPRD-u1-u2)/2 sfr ; sacl taon ; add u1 ;tbon=taon+u1 sacl tbon ; add u2 ;tcon=tbon+u2 sacl tcon ; * END taon,tbon and tcon calculation * sector switching lacl sector sub #1 bcnd nosect1,NEQ ;depending on the sector number we have ;to switch the calculated taon, tbon and tcon ;to the correct PWM channel ;(see SPACE VECTOR Modulation references for details) Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 39 Appendix C: Software program describing the first method bldd tbon,#CMPR1 ;sector 1 bldd taon,#CMPR2 bldd tcon,#CMPR3 b dacout nosect1 lacl sector sub #2 bcnd nosect2,NEQ bldd taon,#CMPR1 ;sector 2 bldd tcon,#CMPR2 ; bldd tbon,#CMPR3 ; b dacout nosect2 lacl sector sub #3 bcnd nosect3,NEQ bldd taon,#CMPR1 ;sector 3 bldd tbon,#CMPR2 ; bldd tcon,#CMPR3 ; b dacout nosect3 lacl sector sub #4 bcnd nosect4,NEQ bldd tcon,#CMPR1 ;sector 4 bldd tbon,#CMPR2 ; bldd taon,#CMPR3 ; b dacout nosect4 lacl sector sub #5 bcnd nosect5,NEQ bldd tcon,#CMPR1 ;sector 5 bldd taon,#CMPR2 ; bldd tbon,#CMPR3 ; b dacout nosect5 bldd tbon,#CMPR1 ;sector 6 bldd tcon,#CMPR2 ; bldd taon,#CMPR3 ; * END sector switching * END * SPACE VECTOR Pulse Width Modulation dacout * * DAC output of channels 'da1' and 'da2' * * Output on 12 bit Digital analog Converter * * 5V equivalent to FFFh * * lacc sector,7 ;scale sector by 2^7 to have good displaying sacl sectordisp ;only for display purposes * DAC out lacc add sacl lar lacc channel 'da1' #i1 da1 daout ar5,daout * the DAC resolution sfr ;get the address of the first elements ;add the selected output variable offset 'da1' sent by the terminal ;now daout contains the address of the variable to send to DAC1 ;store it in AR5 ;indirect addressing, load the value to send out ;the following 3 instructions are required to adapt the numeric format to ;on a 12 bit DAC, the number 2000h = 5 Volt Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 40 Appendix C: Software program describing the first method sfr add sacl out * END DAC ;-2000h is 0 Volt #800h ;0 is 2.5 Volt. daouttmp ;to prepare the triggering of DAC1 buffer daouttmp,DAC0_VAL out channel 'da1' * DAC out lacc add sacl lar channel 'da2' #i1 da2 daout ar5,daout lacc * ;get the address of the first elements ;add the selected output variable offset 'da1' sent by the terminal ;now daout contains the address of the variable to send to DAC1 ;store it in AR5 ;indirect addressing, load the value to send out ;the following 3 instructions are required to adapt the numeric format to the DAC resolution sfr ;we have 10 bit DAC, we want to have the number 2000h = 5 Volt sfr add #800h ; sacl daouttmp ;to prepare the triggering of DAC1 buffer out daouttmp,DAC1_VAL * END DAC out channel 'da2' * DAC out lacc add sacl lar lacc channel 'da3' #i1 da3 daout ar5,daout * ;get the address of the first elements ;add the selected output variable offset 'da1' sent by the terminal ;now daout contains the address of the variable to send to DAC1 ;store it in AR5 ;indirect addressing, load the value to send out ;the following 3 instructions are required to adapt the numeric format to the DAC resolution sfr ;we have 10 bit DAC, we want to have the number 2000h = 5 Volt sfr add #800h sacl daouttmp ;to prepare the triggering of DAC1 buffer out daouttmp,DAC2_VAL * END DAC out channel 'da3' * DAC out lacc add sacl lar lacc channel 'da4' #i1 da4 daout ar5,daout * ;get the address of the first elements ;add the selected output variable offset 'da1' sent by the terminal ;now daout contains the address of the variable to send to DAC1 ;store it in AR5 ;indirect addressing, load the value to send out ;the following 3 instructions are required to adapt the numeric format to the DAC resolution sfr ;we have 10 bit DAC, we want to have the number 2000h = 5 Volt sfr add #800h sacl daouttmp ;to prepare the triggering of DAC1 buffer out daouttmp,DAC3_VAL * END DAC out channel 'da4' OUT tmp,DAC_VAL * Context larp mar lacl add restore ar4 *+ *+ *+,16 ;start conversion ;Accu. restored for context restore Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 41 Appendix C: Software program describing the first method lst #0,*+ lst #1,*+ * End Context restore clrc INTM ret * END _PR_int ISR _c_int0: * * Board general settings * * clrc CNF setc SXM clrc XF * * Function to disable the watchdog timer * * ldp #DP_PF1 splk #006Fh, WD_CNTL splk #05555h, WD_KEY splk #0AAAAh, WD_KEY splk #006Fh, WD_CNTL * * Function to initialise the Event Manager * * GPTimer 1 => Full PWM * * Enable Timer 1=0 interrupt on INT2 and CAP1 on INT4 * * Capture 1 reads tacho input * * All other pins are IO * * ; Set up SYSCLK and PLL for C24 EVM with 10MHz External Clk ldp #DP_PF1 splk #00000010b,CKCR0 ; PLL disabled ; LPM0 ; ACLK enabled ; SYSCLK 5MHz splk #10110001b,CKCR1 ; 10MHz clk in for ACLK ; Do not divide PLL ; PLL ratio x2 splk #10000011b,CKCR0 ; PLL enabled ; LPM0 ; ACLK enabled ; SYSCLK 10MHz PLL x2 ; Set up CLKOUT to be SYSCLK splk #40C0h,SYSCR ; Clear lacc and sacl all reset variables SYSSR #69FFh SYSSR ; Set up zero wait states for external memory lacc #0004h sacl * out *,WSGR ; Clear All EV Registers zac Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 42 Appendix C: Software program describing the first method ldp sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl sacl * * #DP_EV GPTCON T1CNT T1CMP T1PER T1CON T2CNT T2CMP T2PER T2CON T3CNT T3CMP T3PER T3CON COMCON ACTR SACTR DBTCON CMPR1 CMPR2 CMPR3 SCMPR1 SCMPR2 SCMPR3 CAPCON CAPFIFO FIFO1 FIFO2 FIFO3 FIFO4 T1 is time base for PWMs T3 starts conversions, T3 + delay = T1 ;Initialise PWM ; No software dead-band splk #666h,ACTR ; Bits 15-12 not used, no space vector ; PWM compare actions ; PWM6/PWM5 - Active Low/Active High ; PWM4/PWM3 - Active Low/Active High ; PWM2/PWM1 - Active Low/Active High splk #100,CMPR1 splk #200,CMPR2 splk #300,CMPR3 splk #0207h,COMCON; FIRST enable PWM operation ; Reload Full Compare when T1CNT=0 ; Disable Space Vector ; Reload Full Compare Action when T1CNT=0 ; Enable Full Compare Outputs ; Disable Simple Compare Outputs ; Full Compare Units in PWM Mode splk #8207h,COMCON; THEN enable Compare operation splk splk ldp bldd LDP splk #PWMPRD,T1PER; Set T1 period #PWMPRD/2,T1CMP; Set T1 compare #delay delay,#T1CNT; configure counter register #DP_EV #0A802h,T1CON; Ignore Emulation suspend ; Cont Up/Down Mode ; x/1 prescalar ; Use own TENABLE ; Disable Timer,enable later Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 43 Appendix C: Software program describing the first method ; Internal Clock Source ; Reload Compare Register Immediately ; Enable Timer Compare operation * * current remote measurement * * T3 starts the AD conversions * * ldp #DP_EV splk #PWMPRD,T3PER ; configure period register splk #PWMPRD/2,T3CMP ; Set T3 compare splk #0000,T3CNT splk #0A88Ah,T3CON ; configure ; use TENABLE of T1CON splk #1822h,GPTCON ; bit 11-12: Start conversion on T3 compare match splk #1862h,GPTCON ; bit 11-12: Start conversion on T3 compare match ; Enable compare outputs ; T1 and T3 are Active high ; Enable Timer 1 and Timer 3 lacc T1CON or #40h sacl T1CON splk #1802h,ADC_CNTL1; Channel 2, ADC1 selected for idc * * Part dedicated to the Hardware board used * * PWM Channel enable for Driver * * 74HC541 74HC541 chip enable connected to IOPC3 of Digital i/o * * ; Configure IO\function MUXing of pins ldp #DP_PF2 ; Enable Power Security Function splk #280Fh,OPCRA ; Ports A/B all IO except ADCs, T1PWM and T3PWM splk #00F9h,OPCRB ; Port C as non IO function except IOPC2&3 splk #0FF08h,PCDATDIR ; bit IOPC3 * END: PWM enable * * Initialize ar4 as the stack for context save * * space reserved: DARAM B2 60h-80h (page 0) * * lar ar4,#79h * * A/D initialization * * ldp #DP_PF1 splk #0403h,ADC_CNTL2 ; prescaler set for a 10MHz oscillator ; enable conversion start by EV * END A/D initialization * * Variables initialization * * ldp #speedr lacc #500h sacl speedr Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 44 Appendix C: Software program describing the first method zac sacl sacl sacl sacl sacl splk splk splk splk tetaref indice1 Va Vb Vc #0,da1 #1,da2 #18,da1 #24,da1 ;default ;default ;default ;default i1 i2 Valfar sector spm 0 ;no shift after multiplication setc OVM setc SXM ;sign extension * END Variables initialization * * VDC initialization * * splk #1000h,VDC ; The DC voltage is 310V ; Vdc in 4.12 with a Vbase=310V splk #1000h,VDCinv ; 1/Vdc splk #380h,VDCinvTc ; Tc/Vdc/2 or PWMPRD/VDC rescaled by 4.12 * * Serial communication initialization * * ldp #DP_PF1 splk #00010111b,SCICCR ;one stop bit, no parity, 8bits splk #0013h,SCICTL1 ;enable RX, TX, clk splk #0000h,SCICTL2 ;disable SCI interrupts splk #0000h,SCIHBAUD ;MSB | splk #0082h,SCILBAUD ;LSB |9600 Baud for sysclk 10MHz splk #0022h,SCIPC2 ;I/O setting splk #0033h,SCICTL1 ;end initialization * * Enable Interrupts * * ; Clear EV IFR and IMR regs ldp #DP_EV splk #07FFh,IFRA splk #00FFh,IFRB splk #000Fh,IFRC ; Enable T1 Underflow Int splk #0200h,IMRA splk #0000h,IMRB splk #0000h,IMRC ;Set IMR for INT2 and INT4 and clear any Flags ;INT2 (PWM interrupt) is used for motor control synchronization ;INT4 () is used for capture 3 ldp #0h lacc #0FFh sacl IFR lacc #0000010b sacl IMR ldp clrc #i1 INTM ;set the right control variable page ;enable all interrupts, now we may serve ;interrupts Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 45 Appendix C: Software program describing the first method * END Enable Interrupts * * Virtual Menu * * menu clrc XF ;default mode (will be saved as context) ldp #DP_PF1 bit SCIRXST,BIT6 ;is there any character available ? bcnd menu,ntc ;if not repeat the cycle (polling) lacc SCIRXBUF and #0ffh ;only 8 bits !!! ldp #option ;if yes, get it and store it in option sacl option ;now in option we have the option number ;of the virtual menu sub #031h ;is it option 1 ? bcnd notone,neq ;if not branch to notone * * Option 1): Speed reference * navail11 ldp #DP_PF1 bit SCIRXST,BIT6 ;is there any character available (8 LSB)? bcnd navail11,ntc ;if not repeat the cycle (polling) lacc SCIRXBUF and #0FFh ;take the 8 LSB ldp #serialtmp sacl serialtmp ;if yes, get it and store it in serialtmp navail12 ldp #DP_PF1 bit SCIRXST,BIT6 ;8 MSB available ? bcnd navail12,ntc ;if not repeat the cycle (polling) lacc SCIRXBUF,8 ;load ACC the upper byte ldp #serialtmp add serialtmp ;add ACC with lower byte sacl speedr ;store it b menu ;return to the main polling cycle * END Option 1): speed reference notone lacc sub bcnd option #032h nottwo,neq * * Option 2): DAC update * navail21 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail21,ntc lacc SCIRXBUF and #0FFh ldp #da1 sacl da1 navail22 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail22,ntc lacc SCIRXBUF ;is it option 2 ? ;if not branch to nottwo ;is there any character available (8 LSB)? ;if not repeat the cycle (polling) ;take the 8 LSB ;if yes, get it and store it in da1 ;is there any character available (8 LSB)? ;if not repeat the cycle (polling) Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 46 Appendix C: Software program describing the first method and #0FFh ldp #da1 sacl da2 navail23 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail23,ntc lacc SCIRXBUF and #0FFh ldp #da1 sacl da3 navail24 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail24,ntc lacc SCIRXBUF and #0FFh ldp #da1 sacl da4 b menu * END Option 2): DAC update nottwo lacc sub bcnd option #033h notthree,neq * * Option 3): delay * navail31 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail31,ntc lacc SCIRXBUF and #0FFh ldp #serialtmp sacl serialtmp navail32 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail32,ntc lacc SCIRXBUF,8 ldp #serialtmp add serialtmp sacl delay b menu * END Option 3): delay notthree lacc sub bcnd option #034h notfour,neq ;take the 8 LSB ;if yes, get it and store it in da2 ;is there any character available (8 LSB)? ;if not repeat the cycle (polling) ;take the 8 LSB ;if yes, get it and store it in da3 ;is there any character available (8 LSB)? ;if not repeat the cycle (polling) ;take the 8 LSB ;if yes, get it and store it in da4 ;return to the main polling cycle ;is it option 2 ? ;if not branch to nottwo ;is there any character available (8 LSB)? ;if not repeat the cycle (polling) ;take the 8 LSB ;if yes, get it and store it in serialtmp ;8 MSB available ? ;if not repeat the cycle (polling) ;load ACC the upper byte ;add ACC with lower byte ;store it ;return to the main polling cycle ;is it option 2 ? ;if not branch to nottwo * * Option 4): Mingap * navail41 ldp #DP_PF1 bit SCIRXST,BIT6 ;is there any character available (8 LSB)? bcnd navail41,ntc ;if not repeat the cycle (polling) lacc SCIRXBUF Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 47 Appendix C: Software program describing the first method and #0FFh ldp #serialtmp sacl serialtmp navail42 ldp #DP_PF1 bit SCIRXST,BIT6 bcnd navail42,ntc lacc SCIRXBUF,8 ldp #serialtmp add serialtmp sacl Mingap b menu * END Option 4): Mingap notfour b ;take the 8 LSB ;if yes, get it and store it in serialtmp ;8 MSB available ? ;if not repeat the cycle (polling) ;load ACC the upper byte ;add ACC with lower byte ;store it ;return to the main polling cycle menu Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 48 Appendix D: Software program describing the second method Appendix D: Software program describing the second method * * TEXAS INSTRUMENTS * * * File Name: open_spe.asm * * Originator: Michel Platnic * * Description:The software includes * * -Induction motor open loop control * * -current measurement with shunt resistor * * 2 current samples taken every 5 PWM period* * -V/f control * * -User Interface * * * * Function list: -PR_int * * -control_Vf * * -meas_pattern * * -get_current * * -send_to_PWM * * * * Target: TMS320F240 TMS320F240, EVMF240 EVMF240 if DAC use * * status: Working * * * * History: Completed on 28 November 97 * * .include ".\c240app.h" .mmregs * * Start * * .globl _c_int0 ;set _c_int0 as global symbol _c_int1 _c_int3 _c_int4 _c_int5 _c_int6 .sect "vectors" b _c_int0 ;reset interrupt handler b _c_int1 ;RTI,SPI,SCI,Xint interrupt handler b _PR_int ;PWM interrupt handler b _c_int3 ; b _c_int4 ; b _c_int5 ; b _c_int6 ;capture/ encoder Interrupts .space 16*6 ;reserve 6 words in interrupt table * * Auxiliary Register used * * ar4 pointer for context save stack * * ar5 used in the interruption PR_int for control calculation* * ar6 for main program * * stack .usect "blockb2",15 ;space for Status Register context save in Page 0 * Motor ERCOLE MARELLI, Nr D 50525/s MW * * Numeric formats: all 4.12 fixed point format twos complement for negative values (4 integer & sign + 12 fractional) except otherwise specified * - Currents: 1000h (4.12)= 1A * - Voltages: 1000h (4.12)= 311 V * - Angles : [0;ffffh] = [0;360] degrees Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 49 Appendix D: Software program describing the second method * - Speed : [0;1000h] (4.12= = [0;1500] rpm * END Numeric formats Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 50 Appendix D: Software program describing the second method * * Look-up tables .includes * * N.B. all tables include 256 elements * * .sect "table" sintab .include sine.tab ;sine wave look-up table for sine and cosine waves generation ;4.12 format * END look-up table .includes * * Variables and constants initializations * * .data * current sampling constants Kcurrent .word 019b5h ;8.8 format (25.71) sampled currents normalization constant * axis transformation constants SQRT3inv .word 093dh ;1/SQRT(3) 4.12 format SQRT32 SQRT32 .word 0ddbh ;SQRT(3)/2 4.12 format * PWM modulation constants PWMPRD .set 0896 ;PWM Period=2*896 -> Tc=2*896*50ns=89.6us (50ns resolution) Mingap .word 80 ;minimum PWM duty cycle ;the MAXDUTY is calculated as PWMPRD-2*Mingap ;it is the maximum utilization of the inverter delay .word 10 ;delay for Idc measurement zero .word 0h MAX .set 736 .bss .bss .bss .bss .bss tmp,1 option,1 daout,1 daouttmp,1 tetaad,1 ;temporary variable (to use in ISR only !!!) ;virtual menu option number ;address of the variable to send to the DACs ;value to send to the DACs ;teta openloop variable * DAC displaying table starts here .bss i1,1 ;phase current i1 .bss i2,1 ;phase current i2 .bss i3,1 ;phase current i3 .bss i_remote1,1 ;first of the 2 idc currents .bss i_remote2,1 ;second of the 2 idc currents .bss i_remote3,1 ;sum of the 2 idc currents negated .bss u1,1 ;SVPWM T1 (see SV PWM references for details) .bss u2,1 ;SVPWM T2 (see SV PWM references for details) .bss seno1,1 ;generated sine wave value .bss coseno,1 ;generated cosine wave value .bss Va,1 ;Phase 1 voltage .bss Vb,1 ;Phase 2 voltage .bss Vc,1 ;Phase 3 voltage .bss VDC,1 ;DC Bus Voltage .bss taon,1 ;PWM commutation instant phase 1 .bss tbon,1 ;PWM commutation instant phase 2 .bss tcon,1 ;PWM commutation instant phase 3 .bss teta,1 ;rotor electrical position in the range [0;1000h] ;4.12 format = [0;360] degrees .bss Valfar,1 ;alfa-axis reference voltage .bss Vbetar,1 ;beta-axis reference voltage .bss speedr,1 ;speed reference .bss X,1 ;SVPWM variable Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 51 Appendix D: Software program describing the second method .bss .bss .bss .bss * END DAC Y,1 ;SVPWM variable Z,1 ;SVPWM variable sectordisp,1 ;SVPWM sector for diplay synchrodisp,1 ;Synchronization of PWM, shifted for display displaying table Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 52 Appendix D: Software program describing the second method .bss sector,1 ;SVPWM sector .bss synchro,1 ;Synchronization signal .bss serialtmp,1 ;serial communication temporary variable .bss u1_meas,1 ;u1 calculated for measurement .bss u2_meas,1 ;u2 calculated for measurement .bss u1_comp,1 ;u1 calculated to compensate the measurement .bss u2_comp,1 ;u2 calculated to compensate the measurement .bss da1,1 ;DAC displaying table offset for DAC1 .bss da2,1 ;DAC displaying table offset for DAC2 .bss da3,1 ;DAC displaying table offset for DAC3 .bss da4,1 ;DAC displaying table offset for DAC4 .bss VDCinv,1 ;1/VDC 4.12 format .bss VDCinvTc,1 ;VDCinv*(Tc/2) (used in SVPWM) .bss tetaincr,1 ;V/f open loop tetaincr (1pu speed) .bss Vamplitude,1 ;V/f open loop Vamplitude .bss indice1,1 ;pointer used to access sine look-up table .bss tmp1,1 ;tmp word to convert to C24 .bss accb,2 ;2 words to replace ACCB in C24 .bss acc_tmp,2 ;2 words to allow swapping of ACC in C24 .bss tetaref,1 * END Variables and constants initializations .text ;link in "text section * * _PR_int ISR * * synchronization of the control algorithm with the PWM * * underflow interrupt * * _PR_int larp ar4 ;context save mar *sst #1,*;status register 1 sst #0,*;status register 0 sach *;Accu. low saved for context save sacl *;Accu. high saved ldp #IFRA>>7 splk #07FFh,IFRA ;Clear all flags, may be change with only T1 underflow int. mar *,ar5 ldp lacc bcnd lacc sub bcnd sub bcnd b #i1 synchro synchro0,EQ synchro #3 synchro3,EQ #1 synchro4,EQ synchro_incr synchro0 call call call bldd bldd call b get_current control_Vf meas_pattern u1_comp,#u1 u2_comp,#u2 send_to_PWM synchro_incr ;used later for DACs output ;from previous period ;start control ;calculate u1 and u2 for measurement ;send new compensated PWM pattern for next period ;send new compensated PWM pattern for next period synchro3 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 53 Appendix D: Software program describing the second method bldd bldd call b synchro4 bldd bldd call ldp zac sacl b u1_meas,#u1 u2_meas,#u2 send_to_PWM synchro_incr ;send measurement PWM pattern for next period ;send measurement PWM pattern for next period u1_comp,#u1 u2_comp,#u2 send_to_PWM #i1 ;send compensated PWM pattern for next period ;send compensated PWM pattern for next period ;one control every 5 PWM synchro context synchro_incr ldp #i1 lacc synchro,9 sacl synchrodisp lacc synchro add #1 sacl synchro context * Context restore larp ar4 mar *+ lacl *+ add *+,16 lst #0,*+ lst #1,*+ * End Context restore clrc INTM ret ;shift by 9 for better display ;variable for visualization on DAC ;Accu. restored for context restore * END _PR_int ISR * * Get the current from A/D * * Input var: A/D FIFO * * Output var: i1, i2 the phase current * * Current Remote measurement - AD conversions * * N.B. we will have to take only 10 bit (LSB) * * get_current clrc SXM ldp #DP_PF1 lacc ADC_FIFO1,10 ;10.6 format ldp #i_remote1 sach i_remote1 ;sampled current, f 4.12 ldp #DP_PF1 lacc ADC_FIFO1,10 ;10.6 format ldp #i_remote1 sach i_remote2 ;sampled current, f 4.12 setc SXM spm 3 ldp #i1 lacl i_remote1 add #00h zero, but it isn't and #3ffh ;then we subtract a DC offset (that should be Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 54 Appendix D: Software program describing the second method sub #512 ;then we have to subtract the offset (2.5V) to have ;positive and negative values of the sampled current sacl tmp lt tmp mpy Kcurrent pac sfr sfr sacl i_remote1 lacl add and sub i_remote2 #00h #3ffh #512 sacl lt mpy pac sfr sfr neg sacl spm add neg sacl ;sampled current f 4.12 tmp tmp Kcurrent i_remote2 0 i_remote1 i_remote3 ;then we subtract a DC offset (that should be zero, but it isn't ;then we have to subtract the offset (2.5V) to have ;positive and negative values of the sampled current ;second current always negative with the convention ;sampled current f 4.12 ;third current calculated * * Current Remote measurement * * determination of current measured depending on sector * * lacc sub bcnd sub bcnd bldd bldd b sector45 bldd add bcnd bldd b sector4 bldd b sector #3 sector123,LEQ #3 sector45,NEQ i_remote3,#i1 i_remote2,#i2 end_remote ;sector 4,5 or 6 ;sector 6 i_remote2,#i1 #1 sector4,NEQ i_remote1,#i2 end_remote i_remote3,#i2 end_remote sector123 add bcnd bldd bldd b sector23 bldd sub ;sector 4 or 5 ;sector 4 #2 sector23,NEQ i_remote1,#i2 i_remote3,#i1 end_remote ;sector 1,2 or 3 i_remote1,#i1 #1 ;sector 2 or 3 ;sector 5 ;sector 1 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 55 Appendix D: Software program describing the second method bcnd bldd b sector3 bldd sector3,NEQ i_remote2,#i2 end_remote ;sector 2 i_remote3,#i2 ;sector 3 end_remote ret * end function get_current Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 56 Appendix D: Software program describing the second method * * function control_Vf provides a Vf control * * input: i1, i2, speedr * * output: u1, u2 * * creating reference voltage for induction motor * * control_Vf mar *,AR5 ldp #i1 lacc speedr abs sacl Vamplitude lt speedr mpy #5beh ;tetainc calculated for 5PWM pac sach tetaincr,4 lacc tetaref add tetaincr sacl tetaref rpt #3 sfr sacl teta rpt #3 sfr and #0ffh ;now ACC contains the pointer to access the table sacl indice1 ; add #sintab ; sacl tmp ; lar ar5,tmp nop nop ; mar *,ar5 lacl * ; nop sacl seno1 ;now we have sine value lacl add and sacl add sacl lar lacc sacl indice1 #040h #0ffh indice1 #sintab tmp ar5,tmp * coseno lt mpy pac coseno Vamplitude sach lt mpy pac sach Valfar,4 seno1 Vamplitude ;the same thing for cosine . cos(teta) = sin(teta+90°) ;90 degrees = 40h elements of the table ; ;we use the same pointer (we don't care) ; ; ; ; ;now we have cosine value ;format 4.12 Vbetar,4 * * Phase 1(=a) 2(=b) 3(=c) Voltage calculation * * (alfa,beta) -> (a,b,c) axis transformation * * modified exchanging alfa axis with beta axis * * for a correct sector calculation in SVPWM * * Va = Vbetar * Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 57 Appendix D: Software program describing the second method * Vb = (-Vbetar + sqrt(3) * Valfar) / 2 * * Vc = (-Vbetar - sqrt(3) * Valfar) / 2 * * lt Valfar ;TREG0=Valfar mpy SQRT32 SQRT32 ;PREG=Valfar*(SQRT(3)/2) pac ;ACC=PREG sub Vbetar,11 ;ACC-=Vbetar*2^11 sach Vb,4 ;shift by 12 to reformat pac ;ACC=PREG neg ;ACC=-ACC sub Vbetar,11 ;ACC-=Vbetar*2^11 sach Vc,4 ;shift by 12 to reformat lacl Vbetar ;ACC=Vbetar sacl Va ;Va=ACCL * END Phase 1(=a) 2(=b) 3(=c) Voltage calculation * * SPACE VECTOR Pulse Width Modulation * * (see SVPWM references) * * lt VDCinvTc mpy SQRT32 SQRT32 ;change to dma pac sach tmp,4 ;implement bsar 12 and sacl lt tmp mpy Vbetar pac sach X,4 lacc X ;ACC = Vbetar*K1 sach accb sacl accb+1 ;ACCB = Vbetar*K1 sacl X,1 ;X=2*Vbetar*K1 lt VDCinvTc splk #1800h,tmp mpy tmp ;implement mpy #01800h pac sach tmp,4 ;shift by 12 to reformat lt tmp mpy Valfar pac sach tmp,4 lacc tmp ;reload ACC with Valfar*K2 add accb+1 add accb,16 sacl Y ;Y = K1 * Vbetar + K2 * Valfar sub tmp,1 sacl Z ;Z = K1 * Vbetar - K2 * Valfar * 60 degrees sector determination lacl #0 sacl sector lacc Va bcnd Va_neg,LEQ ;If Va2*Mingap we have to saturate u1 and u2 add u2 ; sacl tmp ; add Mingap,1 ; sub #PWMPRD bcnd nosaturation,LT,EQ * u1 and u2 saturation, Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 60 Appendix D: Software program describing the second method lacc #PWMPRD,14 ;divide PERIOD-2MINGAP by (u1+u2) sub Mingap,15 sfl rpt #15 ; subc tmp ; sacl tmp ; lt tmp ;calculate saturate values of u1 and u2 mpy u1 ;u1 (saturated)=u1*(PERIOD-2MINGAP/(u1+u2) pac ; sach u1,1 ; mpy u2 ;u2 (saturated)=u2*(PERIOD-2MINGAP/(u1+u2) pac ; sach u2,1 ; * END u1 and u2 saturation nosaturation * taon,tbon and tcon calculation lacc #PWMPRD ;calculate the commutation instants taon, tbon and tcon sub u1 ;of the 3 PWM channels sub u2 ;taon=(PWMPRD-u1-u2)/2 sfr ; sacl taon ; add u1 ;tbon=taon+u1 sacl tbon ; add u2 ;tcon=tbon+u2 sacl tcon ; * END taon,tbon and tcon calculation * ADC synchronization bldd tbon,#T1CMP bldd tbon,#T3CMP ;Event Manager synchronization for start ;of AD conversion * End ADC synchronization * sector switching lacl sector sub #1 bcnd nosect1,NEQ bldd bldd bldd b nosect1 lacl sub bcnd bldd bldd bldd b nosect2 lacl sub bcnd bldd bldd bldd b nosect3 lacl sub tbon,#CMPR1 taon,#CMPR2 tcon,#CMPR3 dacout sector #2 nosect2,NEQ taon,#CMPR1 tcon,#CMPR2 tbon,#CMPR3 dacout sector #3 nosect3,NEQ taon,#CMPR1 tbon,#CMPR2 tcon,#CMPR3 dacout ;depending on the sector number we have ;to switch the calculated taon, tbon and tcon ;to the correct PWM channel ;(see SPACE VECTOR Modulation references for details) ;sector 1 ;sector 2 ; ; ;sector 3 ; ; sector #4 Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 61 Appendix D: Software program describing the second method bcnd nosect4,NEQ bldd tcon,#CMPR1 ;sector 4 bldd tbon,#CMPR2 ; bldd taon,#CMPR3 ; b dacout nosect4 lacl sector sub #5 bcnd nosect5,NEQ bldd tcon,#CMPR1 ;sector 5 bldd taon,#CMPR2 ; bldd tbon,#CMPR3 ; b dacout nosect5 bldd tbon,#CMPR1 ;sector 6 bldd tcon,#CMPR2 ; bldd taon,#CMPR3 ; * END sector switching * END * SPACE VECTOR Pulse Width Modulation Three phase current measurements using a single line resistor on the TMS320F240 TMS320F240 62 Appendix D: Software program describing the second method dacout * * DAC output of channels 'da1' and 'da2' * * Output on 12 bit Digital analog Converter * * 5V equivalent to FFFh * * lacc sector,9 ;scale sector by 2^7 to have good displaying sacl sectordisp ;only for display purposes * DAC out lacc add sacl lar lacc channel 'da1' #i1 da1 daout ar5,daout * ;get the address of the first elements ;add the selected output variable offset 'da1' sent by the terminal ;now d