Control and DC-capacitor voltage balancing of a space vector-modulated five-level STATCOM

A space vector modulation (SVM)-based switching strategy for a five-level diode-clamped converter that is adapted as a static compensator (STATCOM) is presented. The main feature of the proposed SVM switching strategy is that it enables voltage-balancing of the DC capacitors, under steady-state and transient conditions, with no requirements for additional control actions or auxiliary devices. A dynamic model of the five-level STATCOM for power system studies is also developed. On the basis of the developed model, a voltage controller to regulate the DC-side voltage and a decoupled current controller to control the AC-side real and reactive power are designed. Performance of the STATCOM and the corresponding controllers are evaluated on the basis of digital time-domain simulation studies in the PSCAD/EMTDC environment. The studies demonstrate capabilities of the proposed space vector modulation (SVM) strategy to maintain voltage balance of the DC capacitors and control the STATCOM reactive power exchange for various operating conditions.