适用于VSC-MTDC系统的直流电压控制策略

直流电压稳定是关系到电压源型直流输电系统可靠运行的关键问题之一。文中首先分析了在电压源型直流输电系统中直接电流控制和直流电压偏差控制的工作原理，然后提出了在电压源型多端直流输电系统中采用基于直流电压偏差控制的多点直流电压控制策略。控制器采用该策略后，能实现定有功功率控制模式与定直流电压控制模式之间的自动转换，确保定直流电压控制的换流站故障退出后，仍能实现对直流电压的控制和有功的平衡。以一个5端系统为例进行仿真验证，结果表明多端直流输电系统的运行可靠性得到提高，且获得良好的动态性能。

A Novel DC Voltage Control Strategy for VSC Based Multi-terminal HVDC System

DC voltage stability is one of the most important issues for reliable operation of VSC based HVDC system. In this paper, principle of the direct current control and DC voltage error method used in VSC based HVDC system is analyzed. A multi-point DC voltage control strategy based on DC voltage error method is then proposed for VSC based multi-terminal HVDC system. This approach can realize automatic switching between active power and DC voltage control modes, so that control of DC voltage and active power balance can still be realized after lost of the converter which is in DC voltage control mode. Simulation is carried out on a VSC-MTDC system with five terminals and the results show that reliability of the multi-terminal HVDC system is improved with the proposed control strategy and satisfactory dynamic characteristics can be obtained.