基于坐标变换的微网功率解耦及限幅控制策略

A Coordinate Transformation Based Power Decoupling and Restriction Control Strategy for Microgrid

传统的功率下垂控制在低压微电网中的直接应用会引起有功和无功功率的耦合问题,为此采用了基于坐标变换的虚拟功率下垂控制方法,并对其解耦特性、功率均分及限幅问题进行了研究.利用相对增益分析方法分析了采用坐标变换后系统功率的耦合程度,从理论上证明了当坐标变换矩阵与线路阻抗的阻感比相同时,虚拟功率下垂控制可以实现功率的完全解耦.针对线路阻抗差异而导致的功率无法均分问题,提出了通过增加虚拟负阻抗来实现并联逆变器间功率均分的方法.考虑到现有的虚拟功率下垂限幅范围与实际功率限幅范围的不对等性,提出了新型虚拟功率下垂限幅控制方法,将功率越限部分划分为8个区域,根据逆变器输出的实际功率确定其所属区域,进而采取相应的限幅调整措施.仿真结果验证了所提控制策略的正确性和有效性.

In low voltage microgrid, traditional power droop control will cause active and reactive power coupling problem. Virtual power droop control based on coordinate transformation was adopted and its decoupling characteristics, power sharing and restriction problems were studied. Relative gain analysis method was used to analyze the power coupling degree after adopting coordinate transformation. It is theoretically proved that the virtual power droop control can realize total power decoupling characteristics when the coordinate transformation matrix and line impedance have the same resistance and inductance ratio. Aiming power sharing, a strategy was proposed, which aimed at the problem that line impedance difference can cause uneven to improve power sharing accuracy by adding virtual negative impedance. In the light of the limitation of the existing power restriction range of virtual power droop control which is not equal to the actual power restriction range of the inverter, a new power restriction control strategy was proposed. Eight sections were divided for the operation points, in which the power exceeds the limits. The section number was determined according to the inverter output power and the corresponding adjustment measures were taken. Simulation results have verified the correctness and effectiveness of the proposed control strategy.