An improved DC capacitor voltage balancing strategy for PWM cascaded H-bridge converter-based STATCOM

This paper presents an improved balancing strategy for the cascaded H-bridge converter-based static synchronous compensator (STATCOM), in which the pulse width modulation (PWM) technique is adopted. The control scheme consists of the direct modulation index modification (DMIM) method and a reactive voltage compensation component. Given that the imbalance occurs among the H-bridges is caused by the different accumulation of tiny losses, the vector analysis method is introduced to analyze the control scheme proposed in this paper. Moreover, the available control area of the proposed method is compared with that of the DMIM method in detail. Finally, the proposed control method is verified by a simulation model in Matlab/Simulink and a prototype experiment, respectively.