Research On Control Strategy Of Negative-Saliency Permanent Magnet Synchronous In-wheel Motor

Negative-saliency permanent magnet synchronous motor(NSPMSM) has broad application prospect in Electric Vehicle Drives(EVDs) for its wide speed range because its Ld is greater than Lq. This paper analyzes the control strategies of NSPMSM both in constant torque region and constant power region. The parameters of NSPMSMs used in EVDs change much becaus e of the work environment, which directly affects the performance of the control system. Thus an adaptive control based on online parameter identification is proposed to overcome this problem. The main contents are as follows:Firstly, the differences of the control system under different operation region of NSPMSM and Positive-saliency PMSM(PSPMSM) are compared theoretically. Adaptive control strategies have been selected both in constant torque region and constant power region. An experiment system has been built to verify the rationality and correctness of the proposed control strategies.Secondly, a step recursive least square(STEP-RLS) method has been proposed to solve the rank-deficient problem of parameters identification. Factors affecting the parameter identification error and speed have been analyzed theoretically, which is verified by experiments.Thirdly, the effect of parameters variation of NSPMSM on Maximum Torque per Amp(MTPA) control have been analyzed theoretically, then adaptive MTPA control is realized based on online parameter identification in constant torque region. The program of STEP-RLS has been called periodically to adjust the parameters of MTPA online. Simulations and experiments have been done to verify the proposed adaptive MTPA control.Finally, in constant power region, adaptive Flux Weakening(FW) based on a PI regulator is proposed. The states of current PI regulator under voltage limit have been analyzed theoretically, and then a PI regulator has been used to control the voltage reference to the DC-link voltage limit. Simulations and experiments under different operations have been done to verify the proposed adaptive FW control.