Control Strategy of Cascade STATCOM Under Unbalanced Grid Conditions

Power network imbalance has become an increasingly serious problem, particularly in coal mines. This study presents an improved control strategy of cascade STATCOM under unbalanced grid conditions. This study investigates the balance and control of all DC capacitor voltages, from global balancing control, clustered balancing control and individual balancing control. In addition, a dual current control closed loop is presented to achieve complete compensation of reactive and negative sequence currents. Simulation results and industrial prototype tests show that the improved control strategy of cascade STATCOM not only solves the balance control problem of all DC capacitor voltages under an unbalanced grid condition, but also improves the ability to reject unbalanced disturbance.