基于态势利导的同步逆变器负序电流抑制方法

Situation Orientation Based Suppression Method of Negative Sequence Current for Synchronverter

电网电压不平衡时,同步逆变器并网运行输出负序电流导致三相并网电流严重不平衡,进而使电网不稳定加剧,制约了其在新能源并网中的应用。针对此问题,对电网电压与逆变器输出电压未能同步而产生的不平衡电流进行机理分析,提出了一种抑制负序电流的新方法。该方法首先对逆变器输出电流进行态势预测,提前预知电流态势信息,然后将预测所得电流变化量转化为相应电压变化量作为前馈信息输入同步控制系统进行实时补偿,可实现同步逆变器态势利导下的快速预防控制。仿真结果表明,所提方法有效抑制了电网电压不平衡时的负序电流,降低了电流不平衡度,并提高了控制系统的动态性能。

When the grid voltage is unbalanced,the output negative sequence current of synchronverter in grid-connected operation causes serious unbalance of three-phase grid-connected current,and this situation further aggravates the instability of power grid and restricts its application in the new energy grid connection.In response to this problem,the mechanism of unbalanced current caused by the grid voltage and inverter output voltage being unsynchronized is analyzed,then a novel method to suppress the negative sequence current is proposed.Firstly,the output current of synchronverter is predicted to foresee current situation information in advance.Secondly,the value of voltage which is calculated by the differential current value from situation prediction is imported to synchronous control system to realize real time compensation.This method can realize preventive control quickly by situation orientation.The simulation results show that the proposed method can effectively restrain the negative sequence current,reduce current unbalance,and improve the dynamic performance of the control system.