Negative-sequence reactive-power control by a PWM STATCOM based on a modular multilevel cascade converter (MMCC-SDBC)

This paper presents an application of a modular multilevel cascade converter based on single-delta bridge-cells (MMCC-SDBC) 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 leading to flexible circuit design, low voltage steps, and low EMI emissions. However, no paper has been published on such a STATCOM with experimental verification. This paper designs, constructs, and tests a 100-V 5-kVA PWM STATCOM based on the SDBC with focus on 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.