Discrete-Time Low-Frequency-Ratio Synchronous-Frame Full-Order Observer for Position Sensorless IPMSM Drives

This paper proposes a complex-vector based discrete-time synchronous-frame full-order observer for position sensorless interior permanent magnet synchronous motor (IPMSM) drives with a low-pulsewidth modulation (PWM) to operating fundamental frequency ratio, a situation common for middle- and high-power applications as well as high-frequency permanent magnet synchronous motor drives. A complex-vector based discrete-time domain zero-order hold equivalent model of IPMSM is developed explicitly incorporating with the stationary frame voltage latch effect of a PWM voltage source inverter. Whereby, a full-order observer is designed and implemented using direct pole assignment in the discrete-time domain to guarantee the stability and dynamic performance with low-frequency ratios. The proposed scheme was verified on a sensorless IPMSM drive. Experimental results confirm both the design methodology and the expected performance attained by the proposed control strategy with low-frequency ratios.