Faculty of Electrical Engineering, Shahed University, Tehran, Iran.
Energy Department, Aalborg University, Aalborg, Denmark.
ISA Trans. 2019 Jan;84:154-163. doi: 10.1016/j.isatra.2018.09.021. Epub 2018 Oct 9.
Recently, LCL filters have been widely used in the output of single phase inverters. Since, the grid side inductor in these filters is in series with the grid impedance at the Point of Common Coupling (PCC), it may create new resonances. This phenomena may take the control loop toward instability. In this case, in order to have a reliable operation, the current controller should be insensitive to the grid impedance variation. In order to damp these resonances, researchers have presented some methods using active or passive damping. These methods added an extra loop to the control loop, an extra passive component in the filter or extra sensor in the control process. But in most of them, the complexity and the cost of controller have been increased. Therefore, presenting a simple control method without extra sensor, passive component or extra arrangement can be a promising approach. This paper presents an MPC-based current controller, which is simple and robust against the grid impedance variation and even the variation of the LCL filter parameters. In contrast to classical multi-loop controller like Proportional-Resonant (PR) controllers, the proposed control method does not need any parameter tuning. In the proposed controller, the switching plan and duty cycles are determined by a cost function and a switching table. Therefore, at the same time with any variation in grid impedance, the proposed controller changes the next switching state and duty cycle. Operating performance like look-up table, searching in all possible switching states to find the best state for the next switching period, makes the controller adaptive and robust against the variation of LCL filter parameters. In order to confirm the effectiveness of the proposed controller, simulations and experimental results of the proposed controller are compared with a classical PR controller.
最近，LCL 滤波器已广泛应用于单相逆变器的输出端。由于这些滤波器中的电网侧电感与公共耦合点（PCC）处的电网阻抗串联，因此可能会产生新的谐振。这种现象可能会使控制回路不稳定。在这种情况下，为了实现可靠的运行，电流控制器应不敏感于电网阻抗的变化。为了阻尼这些谐振，研究人员提出了一些使用有源或无源阻尼的方法。这些方法在控制回路中增加了一个额外的回路，在滤波器中增加了一个额外的无源元件或在控制过程中增加了一个额外的传感器。但在大多数情况下，控制器的复杂性和成本都增加了。因此，提出一种无需额外传感器、无源元件或额外布置的简单控制方法可能是一种很有前途的方法。本文提出了一种基于模型预测控制（MPC）的电流控制器，该控制器对电网阻抗变化甚至 LCL 滤波器参数变化具有简单和鲁棒性。与比例谐振（PR）等经典多环控制器相比，所提出的控制方法不需要任何参数调整。在提出的控制器中，开关计划和占空比由成本函数和开关表确定。因此，在电网阻抗发生任何变化的同时，所提出的控制器会改变下一个开关状态和占空比。与查找表类似的工作性能，即在所有可能的开关状态中搜索以找到下一个开关周期的最佳状态，使控制器能够自适应并对 LCL 滤波器参数的变化具有鲁棒性。为了验证所提出的控制器的有效性，将所提出的控制器的仿真和实验结果与经典的 PR 控制器进行了比较。
