并网逆变器无锁相环基准正弦的实现方法

An Approach to Obtain Reference Sinusoidal Signal for Grid-Connected Inverter Without Phase-Locked Loop

新能源并网发电要求并网电流与电网电压同频同相,获得与电网同步的基准正弦是关键。实际并网系统中,电网电压畸变和频率偏移严重影响了锁相环检测基准正弦的准确度,为此提出一种基准正弦的实现方法。该方法利用一相电网电压,无需锁相环可获得与该相电网电压同频同相的基准正弦,经适当矩阵变换可得三相的基准正弦,不受电网电压畸变、多次过零及不平衡的影响。为保证算法的有效性,需将低通滤波器给定初值并进行低频信号的提取。仿真算例及试验结果均验证了该方法的可行性。

It is necessary for grid-connection of distributed generation system to make the inverter output current strictly kept the same frequency and phase as those of grid voltage,thus the key point is to obtain the reference sinusoidal signal that is synchronic to power grid.Since in actual grid-connected system the grid voltage distortion and grid frequency deviation seriously affect the accuracy of reference sinusoidal signal detected by phase-locked loop（PLL）,an approach to obtain reference sinusoidal signal is proposed,in which only single-phase voltage is utilized to attain the reference sinusoidal signal with the same frequency and phase angle as those of grid voltage without PLL.The sinusoidal signal obtained by the proposed approach is not affected by the distortion,multi-times of zero-crossing and unbalance of grid voltage.To ensure the effectiveness of the proposed algorithm,the initial value of second-order low-pass active filter should be set to extract low-frequency signal.The feasibility of the proposed method is verified by simulation results and experimental results.