分布式虚拟同步发电机改进低电压穿越控制技术

传统分布式虚拟同步发电机不具备低电压穿越能力,在分析电网短路故障时传统虚拟同步发电机的运行特性基础上,提出保留功率环的改进分布式虚拟同步发电机低电压穿越控制技术。改进控制技术给出了电网短路故障时功率指令值的计算方法,同时在无功功率控制环中引入PI调节器,并在同步旋转坐标下对输出电流进行分序控制,实现不对称故障时输出电流的三相平衡,最后通过引入虚拟阻抗对瞬时故障电流进行抑制。改进后的分布式虚拟同步发电机低电压穿越控制技术,保留功率控制环,不改变虚拟同步发电机机理,在故障发生和清除时,只需对功率指令值进行重新设定,无需切换控制策略,实现分布式虚拟同步发电机的低电压穿越。仿真及试验结果验证所提控制策略的正确性及有效性。

Improved low voltage ride-through control strategy for distributed virtual synchronous generator

The traditional virtual synchronous control strategy has no ability to ride-through low voltage.The low voltage ride-through control technology of distributed virtual synchronous generator was proposed based on the analysis of the operating characteristics of the traditional virtual synchronous generator in the short circuit fault of the power grid.The PI controller was introduced to improve the response speed of reactive power control loop,and the calculation method of the power setpoint was redefined.Then,the output current was sequentially controlled in synchronous rotating coordinates to achieve three-phase balance of output current in asymmetric faults,and the instantaneous fault current is suppressed by introducing the virtual impedance.The improved low voltage ride through control technology of distributed virtual synchronous generator retains the power control loop,and does not change the basic mechanism of the virtual synchronous generator.When the fault occurs and disappears,only the power command value needs to be reset,and there is no need to change the control strategy.Simulation and experimental results verify correctness and effectiveness of the proposed control strategy.