Phase-shifted space vector PWM and on-time correction DC voltage balancing scheme for cascaded H-Bridge STATCOM

This paper presents a phase-shifted space vector pulse-width modulation (PSSVPWM) scheme for cascaded H-Bridge (CHB) multilevel static synchronous compensator (STATCOM). It can be implemented in the distributed control system (DCS), which makes modularization easier. This scheme is based on single H-Bridge space vector pulse-width (SHB-SVPWM) algorithm. It can be easily extended to n-level CHB converters without additional complex computation like conventional multilevel SVPWM methods. And the equivalent switching frequency of converter output voltage is high, yet the switching frequency of each cell is low. At the same time, an on-time correction is introduced to the PSSVPWM scheme. By this means, the dc voltages in CHB STATCOM can be balanced. Compared with the conventional redundant space vectors selection method, this method is very simple in high-level converter. The validity of PSSVPWM scheme and dc voltage balancing method is verified by the simulation and experimental results.