| Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC)transmission system is quite different with the conventional thyristor based converterHVDC transmission due to the use of IGBT valves based converter and pulse widthmodulation (PWM). This difference in operation makes VSC-HVDC a number ofpotential advantages over the classic HVDC, which has been widely used and ispromising to replace the conventional HVDC in the near future.Flexible HVDC uses the technology of VSC-HVDC. The research works onVSC-HVDC with the debugging experience of the Shanghai Nanhui VSC-HVDCDemonstration Project was introduced and the result was concluded. The maincontents are stated below:(1) The basic working principle of VSC-HVDC technology was studied in thispaper. Some related problems such as the transmission system connection mode, theconvertor station electrical wiring, the transmission principle, the MMC topologicalstructure, the MMC working principle and so on were discussed and analyzed withthe detailed design scheme of the demonstration project.(2) Converter station control system is one of the core of Flexible HVDCtransmission system. The design scheme of the control system of the converter stationin the demonstration project was studied, including the station control system,man-machine interface, VSC-HVDC control system, VSC-HVDC protection system,Valve Base Controller, etc. The control strategy and the protection criterion wereanalyzed in detail.(3) The performance of the demonstration project was test under differentoperation mode. The result showes that the demonstration project has a excellentperformance, a flexible control, a reliable operation, and it meets the designrequirements. The research results are summarized finally.The development of Flexible HVDChas enormous social benefits, has positive significance to the development of nationaleconomy, representing the development direction of high voltage direct currenttransmission at the present stage. |
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