A coordinated DC voltage control strategy for H-bridge cascaded STATCOM

Keeping the equalization of the DC capacitor voltage is one of the critical problems for the reliable operation of the cascaded H-bridge multilevel STATCOM. In this paper, a novel coordinated DC voltage control strategy for H-bridge cascaded STATCOM is proposed to solve this above problem without extra infrastructures. This control strategy is a two-level hierarchy which consists of a predicted central controller and an amending distributed controller. This predicted central controller is to obtain the reference of equivalent output voltage of STATCOM by a dual-loop DC voltage and AC instantaneous current controller. The result of distributed DC voltage controller is functioned to just amend the above average voltage reference slightly while the implement of predict ac output reference as a feed forward component. The simulation platform has been built on Matlab/Simulink and PLECS. The simulation results show that the proposed control strategy has excellent robustness and fast-response characteristic in a large step change.