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为了保证直流系统在紧急功率支援时能有效提升实际输送功率，有必要分析直流系统实际输送功率受直流换流站交流母线电压波动的影响情况。在理论分析时直流系统采用了准稳态模型，然后根据直流系统Ud-Id特性曲线分析得到直流系统的各种可能的运行模式受两端换流站交流母线电压的影响情况，最后针对每种模式计算得到此时直流系统的实际输送功率。仿真结果表明，理论分析得到的直流系统实际输送功率受两端换流站交流母线电压的制约情况与PSCAD/EMTDC 中直流系统详细模型的仿真结果一致。研究结果表明，只有两端换流站交流母线电压维持在一定电压水平，才能使直流系统实际输送功率达到紧急功率支援指令值。“,”ABSTRACT:To guarantee that the high voltage direct current (HVDC) system is able to raise the transmission power effectively in the case of emergency power support, it is necessary to analyze the impact of the voltage fluctuation of HVDC converter AC bus on the DC transmission power. The HVDC quasi-steady model was adopted for theoretical analyzing in this paper, then the operating mode of the HVDC system varying with HVDC converter AC bus voltages at both ends was obtained according to the HVDC Ud-Id characteristic curve, and finally the actual transmission power of the HVDC system for each possible operating mode was calculated. The simulation results show that the theoretical analysis result of the transmission power of HVDC limited by the varying of HVDC converter AC bus voltages was consistent with that of the simulation with a detail HVDC model in PSCAD/EMTDC. The research results show that in emergency, only when the HVDC converter AC bus voltages at both ends maintain at a certain voltage level, can the actual transmission power of the HVDC system follow the order of emergency power support reference.