一种应用于直流微电网并网变换器的双电流反馈控制策略

Dual current feedback control strategy for DC microgrid grid-connected converter

针对弱电网时谐振频率发生变化导致LCL型并网变换器稳定裕度降低的问题,提出一种应用于直流微电网并网变换器的双电流反馈控制策略。根据变换器交直流两侧功率守恒以及传统下垂控制方程,建立直流母线电压与变换器侧电流的二次函数关系,简化直流母线电压控制方式,减少控制器参数设计;在变换器侧电流反馈控制内环加入并网电流反馈有源阻尼,分析其阻尼等效特性,提高弱电网下的谐振抑制效果。仿真与实验结果表明该控制策略能够实现直流侧母线电压的稳定控制以及交流侧并网电流的谐波优化。

Aiming at the problem of stability margin reduction of LCL type grid-connected converter caused by variation of resonant frequency in weak power grid,a dual current feedback control strategy for DC microgrid grid-connected converter is proposed.According to the power conservation at both AC and DC sides of the converter and the traditional droop control equation,the quadratic function relationship between DC bus voltage and converter side current is established to simplify the control mode of DC bus voltage and reduce the parameter design of controller.The active damping of grid-connected current feedback is added into the inner loop of current feedback control at converter side,and its damping equivalent characteristics are analyzed to improve the resonance suppression effect in weak power grid.The simulative and experi⁃mental results show that the proposed control strategy can realize stability control of bus voltage at DC side and the harmonic optimization of grid-connected current at AC side.