Static synchronous compensator (STATCOM) can effectively improve the power quality in the mediumvoltage distributed energy system (DES). In order to keep the system stable operation, fault-tolerant ability should be maintained to improve the reliability of STATCOM. With the idea of virtual capacitor voltage, a simplified fault-tolerant control scheme is proposed for popular cascaded H-bridge (CHB) based STATCOM. First, an improved modulation method is adopted to significantly reduce these carrier waves. Then, based on the virtual capacitor voltage, the control scheme during the cell fault can be further simplified. Finally, the detailed postfault operation principle is presented according to different operation conditions of STATCOM, where the capacitor voltages in the faulty phase can remain unchanged in certain cases. Validation results verify the effectiveness of the proposed fault-tolerant scheme.
Keywords distributed energy system (DES), static synchronous compensator (STATCOM), fault-tolerant, bridge cell fault, virtual voltage