Average power balancing control of a STATCOM based on the cascaded H-bridge PWM converter with star configuration

This paper presents the average power balancing (APB) control method for the modular multilevel cascaded converter (MMCC) based on single-star bridge cells (SSBC) in the static synchronous compensator (STATCOM) applications. The proposed APB control accomplishes both the reactive power injection and all the dc voltage balancing control at the same time. These functionalities also work even as grid voltage sag occurs. The control algorithm is verified with a 220-V 1kVA STATCOM based on MMCC-SSBC, and the test results show that all the dc voltages are still regulated at the commanded value even in the unbalanced grid voltages.