应用于负序电流补偿的无锁相环并网逆变器控制策略

Grid-tied Inverter Control Strategy Without PLL for Compensating Negative Sequence Current

电网电压不平衡时,负序电流会严重影响并网逆变器输出电能的品质,电网信息的检测速度是影响负序电流补偿的主要因素之一。为此提出基于虚拟矢量的无锁相环控制策略。首先,分析了锁相环与无锁相环控制策略之间的区别。其次,通过引入延迟消除算法消除电网不平衡下所产生的二次谐波分量。最后,在固定频率旋转坐标系下通过双闭环控制对负序电流进行直接控制。实验结果表明,无锁相环控制策略不但抑制负序电流,而且省略了以往锁相环对电网电压的跟踪过程,从而在响应时间上更胜一筹。

When the grid voltage is unbalanced,the negative sequence current will seriously affect the quality of the output power of the grid-connected inverter.The detection speed of the grid information is one of the main factors of negative sequence current compensation.Therefore,a control strategy without phase-locked loop(PLL)based on virtual vector was proposed.Firstly,the difference between the control strategy with and without PLL was analyzed.Secondly,the reordering elimination algorithm was adopted to eliminate the second harmonic component generated under the imbalance of the power grid.Finally,the double-loop control was used to directly control the negative sequence current in a fixed frequency rotating frame.The experiment results show that the control strategy without PLL not only suppresses the negative sequence current,but also omits the previous PLL tracking process of the grid voltage,which is better in response time.