Development and Verification Test of the 6.6-kV 200-kVA Transformerless SDBC-Based STATCOM Using SiC-MOSFET Modules

This article discusses development and verification test results of the 6.6-kV 200-kVA transformerless static synchronous compensator (STATCOM). This STATCOM is characterized by the use of a modular multilevel single-delta bridge-cell (SDBC) converter and silicon carbide metal-oxide-semiconductor field-effect transistor (MOSFET) modules. The article discusses a control method for the 6.6-kV system with focus on dc-capacitor voltage control. The voltage control presented in this article is different from the ones presented earlier. It consists of intercluster balancing control and intracluster balancing control. The former, also known as cluster balancing control, eliminates the requirement of the separate overall dc-voltage control present in conventional methods, whereas the latter, also known as individual balancing control, is replaced with a new technique based on the control of a dead time of each bridge cell. The article makes a detailed description of the latter. Experimental results obtained from the 6.6-kV 200-kVA verification test equipment validate the effectiveness of the control method. Moreover, successful test results confirm the efficacy of the system for grid-voltage regulation and load compensation.