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多端直流输电和直流电网技术是解决新能源并网的有效技术手段之一,直流变压器是连接不同类型和不同电压等级直流输电系统、构建直流电网的关键设备.该文提出一种适用于连接基于电网换相换流器(line commutated converter,LCC)的高压直流输电(high voltage direct current,HVDC)系统和基于电压源换流器(voltage source converter,vsC)的高压直流输电系统的直流互联变压器.当LCC-HVDC工作在常态潮流工况下,提出的直流互联变压器与已有的文献相比,交流环流小,效率高.当LCC-HVDC工作在反转潮流工况下,直流互联变压器能够跟踪改变LCC侧电压极性.详细分析直流互联变压器在不同工况下的工作原理、调制方式和控制策略,并搭建基于Matlab/Simulink的仿真模型,验证理论分析的正确性.“,”Multi-terminal high voltage direct current (HVDC) and DC grid technology are the efficient methods to resolve the problems of renewable energy integration,and DC transformer is the key equipment to interconnect different types of HVDC systems with different voltage levels and build DC grid.This paper presented a DC transformer topology to interconnect line commutated converter based HVDC system (LCC-HVDC) and voltage source converter based HVDC system (VSC-HVDC).When LCC-HVDC operates in the normal power direction condition,the proposed DC transformer provides higher efficiency compared with the prior arts;and when LCC-HVDC operates in the reversal power direction condition,the DC transformer can change the polarity of the LCC-side voltage.The detailed operating principle,modulation method and control strategy of the proposed DC transformer under different conditions were discussed,and the simulation model based on Matlab/Simulink platform had been built to verify the theoretical analysis.