Control of cascaded multi-level STATCOM using line voltage total harmonic distortion minimization technique

In this paper, a new switching strategy is proposed for a multi-level STATCOM system. An efficient approach in reducing the harmonic contents of the inverter´s output voltage is total harmonic distortion (THD) minimization. In multilevel inverters with fundamental frequency switching strategy (each switch turning on and off once per output cycle), the switching angles can be selected such that the output THD is minimized. In three phase multilevel inverters, the optimization algorithm is commonly applied to the phase voltage of the inverter. This results in the minimum THD in phase voltage, but not necessarily in the line to line minimum THD. In this paper, THD minimization process is directly applied to the line to line voltage of the inverter, and a new control strategy of multilevel STATCOM is proposed. The proposed method will be implemented, in RTDS and the closed loop operation of multi-level STATCOM will be explored.