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

This paper describes a STATCOM based on diode-clamped multilevel converters. The current rating is increased by parallel connections of multiple converter modules, The gate-turn-off thyristor (GTO) switching angles of the fundamental switching strategy are exploited in the design to accomplish three objectives: I) 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 (P-I) feedback loops are employed for the purposes of: 1) regulating the total de 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 de capacitor voltages in all the levels.