Multi-Level Voltage Reinjection Converter And Its Application To Power Transmission

In the passed two decades the FACTS concept has been widely accepted and numbers of FACTS devices have been developed. Particularly the high power forced-commutated converters provide attractive performances and flexible controllability, as well as potential application for power transmission and distribution system. The paper proposed a new configuration of multi-level reinjection VSC with reinjection H-bridge chain. The new topology can apply to high power and high voltage transmission application.The new concept of multi-level reinjection VSC(MLVR-VSC)is a combination of the multi-level, soft switching and reinjection conversion concept. The MLVR-VSC is to provide a solution of dynamic voltage balancing for direct series connected switching devices to form high voltage valves, to reduce the harmonic content to produce high quality waveforms, to improve the conversion efficiency and reliability by using low switching frequency and soft switching conditions for main bridge switches. A seven-level reinjection configuration is described in detail, Its firing sequences, waveform analysis, steady and dynamic performances and capacitor voltage balancing are presented. The MLVR-VSC is could be connected to the power grid and operates as a high performance STATCOM.The EMTDC simulations results of the proposed 7-level MLVR-VSC connected to power grid as STATCOM show it is a high performance STATCOM and suitable for power transmission application. It can provide low harmonic ac output. It requires fewer switching components than the conventional multi-level schemes without needs of filters and Pulse Width Modulation. Thus it is suitable for high voltage transmission. The inbalanced source condition simulation verifies it can operate appropriately for balanced and inbalanced conditions.