A High Dynamic Performance SHEPWM Controller for PMSM at Low Switching Frequency

The switching frequency of high power motor drives is usually restrained to less than 1kHz due to high switching loss. Low switching frequency causes control instability and current distortion. In this paper, a simple synchronous optimal pulse-width modulation controller for field-oriented control (FOC) of permanent magnet synchronous motor (PMSM), based on Regular-Sampled selective harmonic elimination PWM (RS-SHEPWM) is proposed. It combines traditional FOC with SHEPWM through a voltage tracking controller, allowing torque and flux decoupling while eliminating the low order current harmonics when operating at the very low switching frequency. Moreover, the switching angles of RS-SHEPWM are calculated online by several simple algebraic equations at each switching cycle, which improves the controller bandwidth and dynamic performance. The dynamic response and harmonic elimination performance of the controller are verified by the simulation and experimental results.