A SHEPWM modulation strategy of APF to reduce current harmonics for high speed PM generator

High speed permanent magnet generator driven by micro-turbine has been widely investigated since it has small size, high efficiency and power density. The output high frequency AC power of the high speed PM generator needs to be converted into the AC power with constant frequency and voltage using AC/DC/AC converter. In order to reduce the current harmonics of high speed generator produced by the AC/DC rectifier, the structure and control strategy of a combined PWM inverter/active power filter (APF) are introduced in this paper. The converter is first utilized as a PWM inverter to drive the generator for the micro-turbine starting, and then operates as an APF during the normal power conversion. The special harmonic elimination PWM (SHEPWM) strategy is adopted due to the maximum switching frequency limitation. The simulation results show the feasibility of the proposed design structure and control strategy.