高压柔性直流电网分层协同自适应下垂控制

为实现直流电网的潮流优化及扰动后不平衡功率的合理分配,提出一种直流电网分层协同自适应下垂控制策略。其中,系统控制层基于各站直流电压、有功功率等信息,以直流电网运行中网损和直流电压偏差最小为优化目标,实时分析并优化各站的直流电压、有功功率指令,以实现稳态时直流电网潮流最优;换流站控制层以本地信号为依据,综合考虑各换流站功率裕度以及电压偏差影响,通过实时自适应调整下垂系数,合理分配扰动后直流电网内部的不平衡功率,同时减小直流电压的偏差。系统控制层的指令值优化与换流站控制层的下垂系数优化协同作用,实现直流电网功率的协调控制。以七端直流电网为例的仿真结果验证了所提策略的有效性和优越性。

Hierarchical Coordinated Adaptive Droop Control in Flexible HVDC Grid

In order to optimize the power flow of the high voltage direct current(HVDC)grid and reasonably distribute the unbalanced power after disturbance, this paper proposes a hierarchical coordinated adaptive droop control strategy in flexible DC grid. Based on the DC voltage and active power of converter stations, the system-level control layer takes minimum network loss and DC voltage deviation of DC grid as the optimization object. Then the references of DC voltage and active power are analyzed and optimized in real time, so that the DC power flow optimization can be achieved in steady state. The optimization of converter-level control layer is based on the local signals. Considering the power margin of converters and the voltage deviation factor, the droop coefficient is adjusted in real time to realize the reasonable distribution of unbalanced power in the DC grid after disturbance and reduce the deviation of DC voltage. The optimization of reference values on system-level control layer is coordinated with the optimization of droop coefficient on converter-level control layer, so the coordination control of power is realized. The simulation results of seven-terminal DC grid verify the effectiveness and superiority of the proposed strategy.