This article revisits the design of the current controller for grid-connected voltage-source converters (VSCs), considering the dynamic impacts of the phase-locked loop (PLL), weak grids, and of voltage feedforward (VFF) control. First, a single-input single-output transfer-function-based model is proposed to characterize the interactions of control loops. It is analytically found that the proportional gain of the current controller essentially aggravates the instability effect of PLL in weak grids, while the cutoff frequency of the low-pass filter used with the VFF loop has a nonmonotonic relationship with the PLL-induced instability. Then, based on these findings, a guideline for redesigning the current controller of PLL-synchronized VSCs is developed, which enables a codesign of the current controller and VFF controller. Finally, simulation and experimental results confirm the validity of theoretical analyses.

中文翻译：

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重新思考弱电网中 PLL 同步 VSC 的电流控制器设计

本文回顾了并网电压源转换器 (VSC) 的电流控制器设计，考虑了锁相环 (PLL)、弱电网和电压前馈 (VFF) 控制的动态影响。首先，提出了一种基于单输入单输出传递函数的模型来表征控制回路的相互作用。分析发现，电流控制器的比例增益本质上加剧了弱电网中锁相环的不稳定效应，而与VFF环路一起使用的低通滤波器的截止频率与锁相环引起的不稳定具有非单调关系。然后，基于这些发现，制定了重新设计 PLL 同步 VSC 的电流控制器的指南，从而实现了电流控制器和 VFF 控制器的协同设计。最后，