电网谐波背景下风电并网逆变器的PRI控制方法

摘要

针对分布式发电接入的配电网常常因负荷影响而含有大量的低次谐波问题，分析了分布式发电中电网电压对逆变器并网电流的影响，提出了一种兼具谐波补偿和直流扰动抑制功能的比例谐振积分（PRI）控制器。与传统比例谐振（PR）控制器相比，积分环节的引入有效地提高了控制器的低频增益，特别对直流分量的扰动具有明显的抑制效果。最后在1台50 kW的三相三电平并网逆变器上进行了样机实验。实验结果表明，PRI控制器不但可以在稳态时大幅减小并网电流的谐波含量，而且在动态过程中可以迅速地抑制并网电流的直流扰动。 PRI控制器非常适合作为分布式发电并网逆变器的控制方法。%For the problem of low order harmonics caused by nonlinear loads,the impacts of grid voltage on grid current in distributed generation grid-connected inverters are analyzed, and a control strategy that can compensate harmonics and suppress DC bias is proposed. In comparison with traditional PR controller, the proposed PRI controller with an additional integral part obtains a higher gain in low frequency, and the controller has an apparent effort especially for suppressing DC bias. Finally, the PRI controller is verified in a 50 kW three-level inverter. The experimental results show that the PRI controller not only can reduce harmonics of grid current in the steady state but also can suppress DC bias rapidly in a dynamic process. The PRI controller is suitable for DGs since they typically contain low order harmonics which caused by nonlinear loads.