Control Strategy of Combined PWM Rectifier/Inverter for a High Speed Generator Power System

Recently more attention has been paid to the distributed power systems due to their high flexibility and reliability. The high speed permanent magnet (PM) 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. The normal AC/DC conversion through diode rectifier will generate harmonic currents in the generator winding which will cause additional losses and increase temperature rise of the generator. To reduce the current harmonics of high speed generator, the structure and control strategy of a combined PWM rectifier/inverter 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 a PWM rectifier during the normal power conversion. The double closed loops (current loop and voltage loop) are adopted. The simulation and experimental results show the feasibility of the proposed design structure and control strategy.