Nonlinearity estimation and compensation of PWM VSI for PMSM under resistance and flux linkage uncertainty

Generally, there exists a voltage distortion or nonlinear voltage gain between the reference and output voltages in a pulsewidth-modulation (PWM) voltage source inverter (VSI). Nonlinearity varies with operating conditions, such as the temperature, direct current (dc) bus voltage, and phase current level. Also, the nonlinearity affects the machine current distortion, torque pulsations, and degradation of control performance. In this paper, the nonlinearity in a PWM VSI is analyzed and a new online estimation method based on the model reference adaptive system is proposed to compensate the time varying voltage distortion, considering the parameter uncertainty caused by the temperature variation for a permanent magnet synchronous motor. The simulation and experimental results show the effectiveness of the proposed voltage difference estimator.

I. Introduction

Recently, a permanent magnet synchronous motor (PMSM) has been receiving much attention because of the inherent advantages of high-power density, high efficiency, large torque to inertia ratio, high starting torque, and free maintenance. These advantages make it preferable to be employed for high-performance home appliance applications, i.e., laundry machines, refrigerators, and air conditioners. In order to decrease the fabric damage in washing machines and increase the heat exchange efficiency in refrigerators and air conditioners, the operating speed of the motor tends to decrease to a low-speed region.