考虑有功备用的光伏发电接入配电网的频率支撑研究

Research on frequency support of the photovoltaic power generation connectedto distribution network considering active standby

随着光伏并网系统越来越多,发电机侧和负荷功率平衡被破坏而出现功率缺额的现象频发。这种功率缺额现象会导致电网频率发生波动,影响稳定性,当电网频率变化时,若光伏发电系统工作在最大功率,则无法通过提高有功功率参与电网调频。针对两级式光伏并网发电系统,基于光伏有功备用思想,提出了减载控制和虚拟同步机(VSG)相结合的控制策略,使得光伏发电系统参与电网频率调节,且能保持较好的稳定性。仿真验证了在提出的控制策略下光伏发电具有较好的频率支撑能力。在αβ坐标系下引入虚拟阻抗的虚拟同步机控制策略,通过调节光伏有功功率实现调频,使得频率能够在0.6 s以内恢复;且能够提高光伏发电系统稳定性。

With the increasing number of photovoltaic grid-connected systems,the balance between generator side and load side could be destroyed frequently,which will cause the shortage of power.Such power deficit will cause fluctuations of the grid frequency and affect stability.If the photovoltaic power generation system works in the maximum power point(MPP)when the frequency changes,it cannot participate in grid frequency regulation by increasing the active power.Therefore,for the two-stage photovoltaic grid-connected power generation system,a control strategy combining load reduction control and virtual synchronous generator(VSG)was proposed,which could enable the photovoltaic power generation system to participate in the grid frequency regulation and maintain good stability.The simulation results showed that the photovoltaic power generation had better frequency support ability under the proposed control strategy.The virtual synchronous machine control strategy of virtual impedance was introduced in theαβcoordinate system,and the frequency modulation was realized by adjusting the photovoltaic active power,so that the frequency can be recovered within 0.6 s.And it could improve the stability of the photovoltaic power generation system.