Dynamic Performance Improvement of Model-Based Capacitor Voltage Control for Single-Phase STATCOM with Reduced Capacitance

This paper proposes an improved model-based capacitor voltage control for single-phase STATCOM. A cascaded H-bridge multilevel converter (CHB-MC) based STATCOM consists of several series connected single-phase STATCOM; therefore, the required capacitance to achieve a constant dc voltage is comparatively high. The concept of applying the drastically reduced capacitance by accepting a strongly fluctuating capacitor voltage has been proposed. For the propose concept, keeping the peak capacitor voltage is important, and its overshoot may occur during transient changes. The transient behavior of the STATCOM with reduced capacitance is discussed and fundamentals of the proposed control are shown. Experimental results confirm that the proposed control can avoid over-shoot after a step-change in current reference.