Improvement of the digital control of a high speed PMSM for vehicle application

The digital control of high speed Permanent Magnet Synchronous Motor (PMSM) is carried out as part of mass reduction for embedded systems. This paper focuses on improving the stability of high speed PMSM digital control. A study of the stability of the closed-loop system shows the importance of taking into account the constraints of digital control (delay and discrete characteristics) in the calculation of decoupling terms and inverse Park transformation. The proposed decoupling is done using the discrete model of the system and a prediction of the evolution of the currents during the delay. The voltage, calculated by vector control, is applied to the machine by a three-phase voltage-source Power Width Modulation PWM converter. This voltage is modified because the rotor reference d-q frame turns during the delay and the switching period. The voltage error caused by this rotation can be significant at high speeds and more generally when the ratio of the switching frequency over the electrical output frequency becomes too high. To stabilize the system, we suggest predicting the average electric angle that the motor will have during the application of the voltage vector. The efficiency is shown through a time simulation.