Fine Current Harmonics Reduction Method for Electrolytic Capacitor-Less and Inductor-Less Inverter Based on Motor Torque Control and Fast Voltage Feedforward Control for IPMSM

In an electrolytic capacitor-less and inductor-less single-phase-to-three-phase inverter, the inverter controls not only the motor but also the input power factor. If the motor has large spatial harmonics, the harmonics flow into the input current at the source side. This paper proposes two new power factor correction methods to improve the input current response of a fundamental frequency and to reduce the input current harmonics. The first method realizes high-power-factor operation by adopting a motor torque control strategy that focuses on the relationship between the input power and the motor torque. The motor torque control allows for designing the gain of the controller to realize a high power factor and enhances the robustness against motor parameter variations. The second method improves the inverter output power response by using a fast voltage feedforward control (FVFFC) that controls the inverter output power directly by focusing on the average dc-link current. The FVFFC reduces the input current harmonics owing to the spatial harmonics of an interior permanent-magnet synchronous motor, and the input current harmonics satisfy the recommendations of guideline JIS 61000-3-2. The effectiveness of the proposed methods is verified through experiments.