不平衡电网电压下基于FPNSC算法的逆变器并网输出电流峰值控制策略

针对电网电压不平衡下电压负序引起的逆变器输出功率波动、电流峰值上升、谐波增大等问题,提出了一种基于灵活正负序控制(FPNSC)算法的逆变器并网输出电流峰值控制策略,在降低了并网电流畸变率的同时,将输出电流约束在允许范围内,保障了有功传输与动态无功支撑。通过引入正负序控制因子,FPNSC算法使输出正负序有功与无功的控制更加灵活。文中给出了不同控制目标下正、负序控制因子的选取及参考电流的计算方法;根据不平衡电网电压下逆变器控制目标,提出了基于FPNSC算法的电流峰值限制方法。仿真与实验验证了所提方法的正确性与有效性,该方法可推广应用于分布式并网发电系统中。

Strategy for control of output current peak of grid-connected FPNSC algorithm based inverter under unbalanced grid voltage

Aiming at the problems such as the fluctuation of output power,the increase of current peak and the increment of harmonics of the inverter,which is caused by the negative sequence of unbalanced voltage under unbalanced grid voltage sag conditions,a control strategy of grid connected output current of inverter based on the flexible positive and negative sequence control (FPNSC) algorithm is proposed.The grid current distortion rate is reduced,and meanwhile the output current is restricted in the allowable range,which ensures the active power transmission and dynamic reactive power support.Through the introduction of positive and negative control factor,FPNSC algorithm makes the output positive and negative part of active power and reactive power control to be more flexible.The selection of positive and negative sequence control factor and the calculation method of reference current is given under different control objectives,and the current peak limiting method based on FPNSC algorithm is proposed according to the control target of the inverter under unbalanced grid voltage sag conditions.The simulation and experimental results verify the correctness and effectiveness of the proposed method,which can be used in distributed generation system.