Based on rational assumptions

current compensation balancing equations and power balancing equations are established. The conditions for negative sequence compensation static synchronous compensator (STATCOM) in △-type and Y-type H-bridge cascade topologies are analyzed. The conclusion that control of zero sequence components is the key to unbalanced current compensation for STATCOM in cascade topologies is proved by simulations with MATLAB/Simulink. The analysis method presented can be generalized to STATCOMs under different working conditions in other topologies. This work is supported by Jiangsu Provincial Natural Science Foundation of China (No. BK20140118) and State Grid Corporation of China (No. GWKJ20140087).