Space Vector Sequence Investigation and Synchronization Methods for PWM Modulation of a High Power Current Source Rectifier

Space vector PWM (SVPWM) schemes for high power current source rectifier (CSR) normally produce low order harmonics and sub-order harmonics due to the low switching frequency and the drifting of synchronization between the PWM waveform and the CSR input frequency. To provide a synchronized PWM and achieve best harmonic performance, different space vector sequences suitable for a current source converter (CSC) are investigated in this paper. Details on how to achieve the waveform symmetries with minimum switching frequency for each sequence are discussed. A thorough comparison of the harmonic performance of different space vector sequences is carried out. In addition, two synchronization methods, namely a PWM frame regulation method and a direct digital phase-locked loop (DPLL) synchronization method are proposed. Both methods are equally effective in providing tight synchronization of the PWM waveform with the CSR input frequency. The space vector sequence investigation and the developed synchronization methods are verified in simulation and experimentally using a 10 kVA GCT based CSR prototype.