基于虚拟同步发电机技术的改进微网下垂控制

Modified droop control based on virtual synchronous generator

采用虚拟同步发电机技术模拟真实同步发电机的旋转惯性和阻尼分量,使得逆变器具有类似于真实发电机所具有的转子特性,从而使得逆变器的输出频率具有一定的抗扰动能力。通过对VSG的阻尼系数D的改进,在控制层面实现了虚拟阻尼的动态变化,在减少频率波动的前提下减小了系统的动态变化时间,并且结合了改进有功-频率控制和电压-无功下垂控制,算例仿真表明,所提控制方法改善了系统的动态频率特性和母线电压水平,取得了良好的控制效果。

The virtual synchronous generator has the capacity to simulate the rotating inertial and damping components of real synchronous generator, so that the inverter has virtual rotor characteristics similar to those of a real generator of which the output frequency of inverter has a certain disturbance suppression capability. The damping coefficient D in VSG is improved to achieve dynamic changes of virtual damping at the control level. Besides, the dynamic change time of system is reduced on the premise of reducing frequency fluctuation, and the modified P f and Q-U droop con trol are combined success{ully. A simulation is included to verify the proposed control method. It is shown that the control strategy improves the dynamic frequency characteristic and bus voltage stability of the system.