STATCOM based on multimodules of multilevel converters under multiple regulation feedback control

This paper describes a STATCOM based on diode-damped multilevel power converters. The current rating is increased by parallel connections of multiple power converter modules. The gate-turn-off thyristor (GTO) switching angles of the fundamental switching strategy are exploited in the design to accomplish three objectives: (1) low total harmonic distortion (THD) in voltages and currents; (2) equal sharing of the currents in the individual modules; and (3) direct control of AC voltage magnitude. Three proportional-integral (PI) feedback loops are employed for the purposes of: (1) regulating the total DC voltages and ensuring the quadrature relationship of the AC currents and voltages; (2) regulating the reactive power drawn by the STATCOM; and (3) equalizing the DC capacitor voltages in all the levels.