Reactive current control of a multi-DC-voltage Cascade STATCOM

This paper presents the reactive power control by a multi-DC-voltage Cascade Static Synchronous Compensator (STATCOM). In order to suppress the harmonics of the output arm voltage, the DC voltages of the series three module in one arm are designed as the voltage ratio of 1.2 : 2 : 6. As a result, 19 voltage levels in the output arm voltage waveform are obtained. The authors propose the voltage control of all the module capacitors based on the stored energy. The effectiveness of the proposed control of the Cascade STATCOM has been verified by experiments.