Fundamental frequency optimal PWM control for high-powered STATCOM employing cascaded multilevel inverters

Reactive power compensation of a 50 Mvar STATCOM employing cascaded multilevel inverters was realized using fundamental frequency optimal PWM control. This paper describes the PWM strategy, its performance and the dc capacitors voltage balancing scheme of the pulse cycle transposition. A scale model experiment using a STATCOM (±18 kvar) was used to study the optimal PWM control and pulse cycle transposition to balance the dc capacitors voltages. The experiment results show that the fundamental frequency optimal PWM control system provides good performance including the total harmonic degree and switching losses, and that the performance of the balancing dc capacitors voltages during the pulsecycle transposition meets the needs of the ±50 Mvar STATCOM.