Development and Verification Test of a 6.6-kV 200-kVA Transformerless STATCOM Based on MMCC-SDBC Using SiC MOSFETs

Abstract

This paper discusses development and verification test results of a 6.6-kV 200-kVA transformerless STATCOM (static synchronous compensator). The STATCOM is characterized by the use of MMCC-SDBC (modular multilevel cascade converter – single-delta bridge-cells) topology and SiC (silicon carbide) MOSFETs (metal-oxide-semiconductor field-effect transistors). The paper also briefly discusses a control method for the 6.6-kV system with emphasis on a dc-capacitor voltage control. The dc-capacitor voltage control, which consists of an inter-phase balancing control and an intra-phase balancing control, is different from the ones presented earlier. Successful test results confirm the efficacy of the system for the control of positive- as well as negative-sequence reactive powers.