This paper proposes a multiloop framework for current control of grid-connected voltage source inverters (VSIs) with LCL output filter. The discrete-time model is of third-order with a nonminimum phase zero when controlling the grid side current. This poses some difficulties on the design of most types of controllers. Motivated by this problem, the inner loop is implemented by a discrete-time sliding mode control law to ensure the tracking of the converter side current. This can be achieved regardless the grid impedance and voltage, making the converter to behave like a current source inverter with a capacitive+inductive (CL) filter. Thus, the problem of current control falls from a third-order system to a second-order system. Several types of controllers can be designed to implement the outer loop based on the equivalent CL circuit. In this work, a resonant controller with a virtual resistor was applied. Simulations and experimental results are presented to validate the proposal.

中文翻译：

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具有 LCL 滤波器的并网 VSI 的多环路框架中的滑模控制器


本文提出了一种用于具有 LCL 输出滤波器的并网电压源逆变器 (VSI) 电流控制的多环框架。控制网侧电流时，离散时间模型是三阶的，具有非最小相位零。这给大多数类型控制器的设计带来了一些困难。受此问题的启发，内环采用离散时间滑模控制律来实现，以确保变换器侧电流的跟踪。无论电网阻抗和电压如何，都可以实现这一点，使转换器的行为类似于带有电容+电感 (CL) 滤波器的电流源逆变器。这样，电流控制问题就从三阶系统降到了二阶系统。可以设计几种类型的控制器来实现基于等效 CL 电路的外环。在这项工作中，应用了带有虚拟电阻的谐振控制器。提出了模拟和实验结果来验证该建议。