Research On AC Variable Frequency Speed Regulation Experimental Platform Based On SVM Direct Torque Control

Several control strategies of AC motor have been developed since AC motorbecame speed-adjustable. Following field oriented control, direct torque control, as anew high performance control technology, which has simple control structure, quickresponse, good robustness, has been paid much attention. As research continues, thedisadvantages of direct torque control caused scholars’ attention, including thepresence of torque ripple, unfixed switching frequency. So plenty of solutions havebeen proposed. Direct torque control based on space vector modulation is one of theimprovement solution. It has fundamentally overcome the disadvantages of Bang-Bang control, using PI aduster or other intelligent controller instead of hysteresisregulator, and space vector modulation to obtain any voltage space vector. Thissolution has improve the performance of direct torque control to some extent.In view of lack of AC variable frequency speed regulation experimental systemin present university lab, this paper developed a set of experimental platform, and hasthe system hardware and the interactive software designed. Based on thisexperimental platform, the DTC control algorithm using space vector modulation isdeveloped.Firstly, on the basis of the mathematical model of system, the DTC controlstrategy based on space vector modulation is discussed, and the structure of which isconfirmed. Based on the design requirements of AC variable frequency speedregulation experimental platform, the system hardware is designed, including themain circuit and the control circuit. Since inverter circuit using discrete switchingdevice is of large volume, complex circuit structure, and poor reliability, the invertercircuit based on intelligent power module(IPM) is designed, so is the protectioncircuit and the DSP interface circuit. The control circuit is designed as a motioncontrol card based on TMS320F2812, and the system test and protection circuit iscompleted.Different from industrial applications, the software system of experimentalplatform not only need to complete control functions, but aslo has to be bothconvenient, reliable, transparent to the user, and has better openness. Therefore, anexperimental platform interactive software is developed based on Visual C++. Withits convenient application programming function, the software realizes thepredetermined functions such as the selecting of different motor control strategiesand the modifying of parameters related, and also realizes waveform monitoringduring system operating. After theoretical analysis and Matlab simulation, DTCbased on space vector modulation algorithm is completed in this interactive software environment, and the implement method of this algorithm is analyzed.Finally, the experimental platform is built, and the algorithm DTC based onspace vector modulation is debugged, then the overall system performance is tested,including dynamic properties test of no-load starting, dynamic speed regulating, loadmutation experiment, and static properties test of no-load operation, loadcharacteristic testing. Expriments have verified that the DTC algorithm based onspace vector modulation has good dynamic and static performance; the performanceof DTC algorithm based on space vector modulation and the conventional DTC basedon hysteresis comparator-switching table is compared, and come to a conclusion thatthe performance of direct torque control is improved.