Individual Phase Control Strategy of a Cascade STATCOM with Star Configuration

Aiming at the problem that the DC voltage of star-connected cascade static synchronous compensator (STATCOM) is unbalanced under the unbalanced grid and unbalanced load, a new individual phase control strategy based on neutral point voltage decoupling control is proposed. The control strategy decouples the star-connected three-phase circuit into three separate single-phase circuits through the neutral point voltage, and carries out DC capacitor voltage stabilization, current tracking and individual voltage equalization control respectively. Compared with the traditional control, the control strategy is simple to control, does not need coordinate transformation, and can automatically adapt to the control of unbalanced conditions without complicated zero-sequence voltage or negative-sequence voltage calculation. In MATLAB/simulink, a simulation model of three-phase nine-chain star-connected cascade static synchronous compensator was built, and simulation experiments were performed under balanced conditions, load unbalanced conditions, and grid voltage unbalanced conditions. Simulation results verify the validity of the proposed control strategy.