基于模块化多电平换流器的多端柔性直流系统接地方式

对舟山多端柔性直流输电系统的接地方式进行了研究,确定了各换流站应采取的接地方式,其中定海和岱山换流站推荐联结变阀侧采用星形电抗＋中性点电阻接地的方式,衢山、洋山和泗礁换流站推荐采用Y/Y型联结变＋阀侧绕组中性点电阻接地方式.在确定各换流站接地方式的基础上,计算确定了换流站设备的过电压和绝缘水平,其中定海和岱山换流站联结变网侧为220 kV交流系统,推荐的设备雷电冲击绝缘水平为950 kV,其他三站联结变网侧为110 kV交流系统,推荐的设备雷电冲击绝缘水平为450 kV;五端换流站联结变阀侧及直流侧的额定电压基本一致,联结变阀侧交流母线的雷电和操作冲击绝缘水平推荐为650 kV（或750 kV）和550 kV,200 kV直流母线的雷电和操作冲击绝缘水平推荐为650 kV（或750 kV）和550 kV.

Grounding Methods of Multi-Terminal VSC-HVDC System Based on Modular Multi-level Converter

The grounding methods for multi-terminal voltage source converter based high voltage direct current （ VSC- HVDC） transmission system in Zhoushan were researched, and the grounding method for each converter station was determined, in which star ground reactance with neutral grounding resistor were recommended for Dinghai and Daishan converter station, while Y/Y converter transformer with neutral grounding resistor were recommended for Qushan, Yangshan and Sijiao converter station. On this basis, the overvoltage and insulation levels of converter station equipments were calculated. For Dinghai and Daishan converter station, the rated voltage of equipment at the ac side of the converter transformer is 220 kV, the lightning impulse insulation level for equipments at this zone are 950 kV. For the other three stations, the rated voltage is 110 kV, the lightning impulse insulation level is 450 kV; the insulation level of lightning impulse and that of switching impulse for AC equipment at the valve side of the transformer are 650 kV （ or 750 kV） and 550 kV; insulations for 200 kV DC polar line are suggested to 650 kV （or 750 kV） and 550 kV respectively.