微网孤岛运行模式下的改进下垂控制方法研究

Research on Improved Droop Control Method for Islanding Operating Mode in Micro-grid

受线路阻抗参数影响,传统的功率下垂控制难以保证并联微源输出的无功功率按其容量比合理分配。针对这一问题,提出了一种用于微网孤岛运行时的改进功率下垂控制策略,公共母线处的中央控制器向各并联微源的本地控制器发送无功功率给定值信号,通过积分器调节后实现下垂特性曲线的平移,保证并联微源输出的无功功率可以合理分配。此外,在无功-电压下垂策略中增加了公共母线电压有效值的反馈控制,保证了该处稳态电压为额定值;同时,在有功-频率下垂策略中通过减小下垂增益保证了系统稳态频率偏离额定值很小,加入了有功功率的微分环节,保证了下垂增益较小时系统仍然具有较好的动态性能。仿真结果验证了所提控制策略的正确性和有效性。

Affected by line impedance,traditional power droop control cannot ensure that the output reactive power of parallel micro-sources could be reasonably allocated according to its respective capacity. In order to deal with this problem,an improved power droop control strategy for islanding operating in micro-grid is proposed. The central controller of the common bus transmits the given reactive power signals to the local controllers of parallel micro-sources. Through the regulation of integral controller,the droop characteristic curve could be moved evenly and automatically to ensure that the output reactive power of parallel micro-sources can be allocated reasonably. In addition,the feedback control of voltage root-mean-square of the common bus is added to the reactive power-voltage droop strategy,which guarantees the steady-state voltage could be of its rated value. Besides,through reducing the droop coefficient in the active power-frequency droop strategy,the system frequency deviation from its rated value could be very small. A differential link of the active power is added to improve the dynamic performance of the system when the active power-frequency droop coefficient is small. Simulation results have verified the correctness and effectiveness of the proposed control strategy.