基于虚拟阻抗的恒压恒频微电源的故障控制策略

Fault Control Strategy of U/f Controlled Micro Sources Based on Virtual Impedance

微电网孤岛运行时,恒压恒频控制模式的逆变型分布式电源(DG)支撑整个网络的电压与频率,其控制策略对微电网的故障穿越能力具有重要影响。该文采用虚拟阻抗法设计了U/f-DG的故障控制策略,分析了基于虚拟阻抗的逆变型DG控制原理,并推导出DG在正、负序网络下的等效模型,设计了故障情况下DG的限流算法。考虑到U/f-DG对并网点电压的支撑效果,提出了一种虚拟阻抗阻感比的设计方法,使不对称故障时并网点电压不平衡度最小化。并提出一种U/f-DG与从属DG的协调控制策略,使得微电网平稳度过故障暂态阶段。最后,Simulink算例仿真验证了所提故障控制策略的有效性。

U/f controlled inverter-based distributed generator （U/f-DG） supports the grid voltage and frequency in islanded microgrid, thus its control strategy has a significant influence on fault ride-through capability of microgrid. In this paper, a fault control strategy of U/f-DG is designed by introducing virtual impedance. Control principle of U/f-DG based on virtual impedance is briefly analyzed, and its equivalent positive and negative sequence model is deduced. Current limiting algorithm of U/f-DG under fault condition is also proposed. Considering voltage support, a design method of virtual impedance R/X ratio is proposed to minimize the voltage unbalance factor under unsymmetrical fault condition. A coordinated control strategy for U/f-DG and the subordinate DGs is presented to ensure that microgrid goes through the transient period smoothly. Finally, the validity of the proposed fault control strategy is verified by Simulink simulation software.