A new 4-level open-ended transformer based STATCOM for high power applications

A new scheme for a 4-level Static Compensator (STATCOM) integrating two 2-Level converters, supplying / absorbing reactive power to / from the grid is proposed in this paper. Reduced component count and simpler layout of switches are the attractive features of the proposed topology over the existing diode clamped multilevel converter. Furthermore, less number of dc links and smaller dc link capacitor values as compared to the cascaded multilevel converter, make the proposed solution more effective than state of the art. Phase Opposition Disposition (POD) Carrier Based Pulse Width Modulation (CB-PWM) with minor modification is suggested for improved performance. Equivalent circuit model of the system is derived based on which a controller for the scheme is designed. The effectiveness of the scheme is verified through detailed simulation study. To confirm the viability of the scheme, experimental studies are carried out on a scaled-down laboratory prototype of the scheme developed for the purpose.