Negative-Sequence Reactive-Power Control by a PWM STATCOM Based on a Modular Multilevel Cascade Converter (MMCC-SDBC)

This paper presents the application of a modular multilevel cascade converter based on single-delta bridge cells (SDBCs) to a STATic synchronous COMpensator (STATCOM), particularly for negative-sequence reactive-power control. The SDBC is characterized by cascade connection of multiple single-phase H-bridge (or full bridge) converter cells per leg, thus facilitating flexible circuit design, low-voltage steps, and low-electromagnetic-interference emissions. This paper designs, constructs, and tests a 100-V 5-kVA pulsewidth-modulated STATCOM based on the SDBC, with focus on the operating principle and performance. Experimental results verify that it can control not only positive-sequence reactive power but also negative-sequence reactive power and low-frequency active power intended for flicker compensation of arc furnaces.