ThreephasecurrentmeasurementsusingasinglelineresistorontheTMS320F240(pdf 75)英文

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
Contents
Three phase current measurements using a single line resistor on the TMS320F240 iv
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
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