多电平注入式电压源变换器应用于高压直流输电系统研究

MULTI-LEVEL VOLTAGE REINJECTION VSC HVDC TRANSMISSION

采用强迫关断开关元件的AC/DC变换器使高压直流输电(HVDC)和柔性交流输电(FACTS)系统具有良好的性能和灵活自由控制有功功率和无功功率的特性.系统中关键装置强迫关断AC/DC变换器必须是高压大功率的装置,才有可能满足输配电的要求.采用多电平技术可显著地提高交流系统容量和电压等级,但常规多电平AC/DC变流器的拓朴结构复杂度随级数成平方律而增加,以及对有功功率控制限制了它们在输电系统中的应用.本文介绍了一种新型的多电平注入式AC/DC变换技术,并对采用该技术的AC/DC变换器用于大功率HVDC系统的应用进行了仿真研究.仿真结果表明,该变换器可产生高质量的波形,易于高压大功率化,可自由控制有功和无功功率,使HVDC的传输性能大大改善,而且采用合理的控制策略,还可以改善HVDC联接的交流系统传输特性,实现单位功率因数传输电能.

This paper depicts a new concept of MLVR conversion （Multi-Level Voltage Reinjection）. and an HVDC link based on MLVR-VSC （voltage Source Converter） terminals is simulated. The simulation results demonstrate that the MLVR-VSC can provide high quality waveforms, achieve high power and high voltage with low power rating and simple extra components, control active and reactive power to benefit the DC link as well as the two AC systems linked by the HVDC link, unity power factor transmission can be achieved. High power AC/DC converters based on forced commutated power switches and capable to provide high quality waveforms and flexible controllability of active and reactive powers for HVDC （High Voltage Direct Current） and FACTS（Flexible AC Transmission System） applications. The forced commutated AC/DC converters for transmission application must be high power and high voltage to suit practical requirements. The multi-level conversion could provide the possibility to increase the power and voltage level, but the complexity of conventional multi-level topologies is increased with the square of the level number, and also the restricts of the active power controllability limit their application in HVDC and FACTS transmissions.