基于VSG技术的VSC-HVDC输电系统受端换流器控制策略

针对传统换流器控制策略下柔性直流（voltage source converter based HVDC，VSC-HVDC）输电系统难以有效参与交流系统频率的动态调节以及交直流系统间功率传输不平衡等问题，在对虚拟同步发电机（virtual synchronous generator，VSG）运行机制特性进行研究的基础上，提出了一种基于VSG技术的VSC-HVDC输电系统受端换流器控制策略。首先，基于VSC-HVDC输电系统拓扑模型，分析了换流站虚拟同步化的可行性；其次，将具有有功模糊PI下垂控制的VSG技术引入到高压直流输电系统，通过调整下垂系数，使柔性直流输电系统逆变器在稳态运行及暂态故障下可以保障系统有功功率平衡传输，使其具有协调控制交流系统频率和直流系统电压的能力；最后，在Matlab/Simulink中构建了一个三端系统用于仿真验证。结果表明：VSC-HVDC输电系统在采用VSG控制策略后，可以改善交流电网的惯性水平，使频率变化得到衰减，其调压控制功能也能在稳态和暂态下提供较好的功率支撑作用，有效提高了交直流系统的稳定性和可靠性。

VSC-HVDC Inverter Control Strategy Based on VSG Technology

With the traditional converter control strategies, the dynamic frequency regulation of the AC power system and the unbalanced power transmission between the AC and DC systems are hard to be involved in voltage source converter based high voltage direct current（VSC-HVDC）system. Aiming at the problem, on the basis of the research on the characteristics of the virtual synchronous generator （VSG） technology, a VSC-HVDC inverter control strategy based on VSG technology is proposed. Firstly, according to the VSC-HVDC system topology model, the feasibility of virtual synchronization of converter station is analyzed. Secondly, the VSG technology with fuzzy PI droop control for active power is introduced into the HVDC transmission system. By adjusting the droop coefficient, the inverter of the flexible HVDC transmission system can ensure the active power transmission balance when the system under steady-state operation and transient faults, so that it has the ability to coordinate control the AC system frequency and the DC system voltage. Finally, a model of three-terminal system is built in Matlab/Simulink for simulation verification. The results show that the VSC-HVDC system can improve the inertial of the AC grid and reduce the change rate of frequency after adopting the VSG control strategy. The FM control can provide better support in the steady state and transient state, which improved the performance of AC and DC system effectively, as well as the reliability of the system. This work is supported by National Natural Science Foundation of China （No.51667020） and Xinjiang Uygur Autonomous Region Key Laboratory Project（No.2016D3021）