Decreasing the Transient Response Time for a STATCOM Base on Cascaded Multilevel Inverter

Abstract

A capacitor in a STATCOM requires a high withstanding voltage when a traditional STATCOM with a single inverter is installed in a high-voltage transmission system. This paper uses a STATCOM that uses cascaded multilevel inverters (CMI) to decrease the withstanding voltage of the capacitor and increase the rated capacity of the STATCOM. A STATCOM based on CMI includes three three-phase inverters. Previous studies use three power controllers in STATCOM based on CMI but this study uses a single power controller to simultaneously control three inverters to balance the three phases of the output voltage. A conventional PI control method is replaced by Proportional Resonant (PR) control to decrease the transient response time of the controller. A 3kVar STATCOM based on CMI is implemented to demonstrate the feasibility of the proposed method. The transient response times for PR and PI controllers under various loads are compared. The experimental results show that a PR controller has a shorter transient response time than a PI controller.