Control Strategy to Improve Control Stability in Transient states of PMSM for xEV

Abstract

In this paper, a current control strategy to improve control stability under transient states of Permanent Magnet Synchronous Motor(PMSM) for xEV driving is described. PMSM for Electric Vehicle(EV) generally stores and uses the optimal current control command based on magnetic flux through a look-up table(LUT) to control torque. However, in transient states where the speed and torque of the motor change rapidly, such as during rapid acceleration or sudden braking, there is a problem in which the voltage momentarily applied to the motor exceeds the inverter output voltage limit. Therefore, there are problems with control stability, such as overshoot of the inverter DC input current. Therefore, to solve this problem, this paper proposes a control strategy that adjusts the change rate of the d-axis current command according to the difference between the inverter output voltage and voltage limit. This strategy secures the maximum voltage margin even in the momentary transient section of PMSM, enabling stable control performance. In addition, to verify the operation of the proposed control method, an experiment using a dynamometer was performed on a 38kW motor and inverter for HEV.