A Novel Capacitor-Voltage Balancing Strategy for Double-Y STATCOM Under Unbalanced Operations

Journal article, 2021

This paper proposes a novel capacitor-voltage balancing strategy for the double-Y MMC STATCOM operated under unbalanced current conditions of the system. The proposed method, based on zero-sequence voltage injection, manipulates the current distribution between the converter arms to minimize the converter ratings. The proposed balancing strategy is compared with the classical approach, based on controlling the circulating dc currents. For the same unbalanced conditions, the proposed strategy leads to lower energy rating for the converter as compared with the classical one, while the semiconductor ratings remain the same in both strategies. Theoretical findings are verified through experimental results.