弱电网下并网逆变器自适应H_∞控制方法

Adaptive H_∞ Control Method for Grid-connected Inverters in Weak Grid

在实际应用中,采用传统的鲁棒H_∞控制方法的并网逆变器,其稳定性和干扰抑制性能往往会受到电网弱电网特性的影响。为了增强并网逆变器对电网阻抗变化的适应能力,提出一种适用于弱电网的并网逆变器改进H_∞控制方法,即自适应H_∞控制方法。以单相并网逆变器为例,建立了弱电网下并网逆变器的鲁棒H_∞控制模型,证明了弱电网特性将会造成该模型中系统参数、控制输入参数以及干扰输入参数出现参数摄动,从而影响了系统的稳定性以及干扰抑制性能。为了克服弱电网特性的影响,改进方法中引入了间接控制来取代公共连接点电压前馈动态地调节公共连接点电压,消除了控制系统的参数摄动,增强了并网逆变器对弱电网具有自适应性,提高了系统的稳定性和干扰抑制性能。最后,通过搭建的实验平台验证了理论分析和所提自适应H_∞控制方法的合理性及有效性。

In practical applications, the stability and interference suppression performance of the grid-connected inverter, using the traditional robust H∞ control method, are often affected by the weak grid characteristics of the power grid. In order to enhance the adaptability of grid-connected inverters to grid impedance changes, this paper presents an improved H∞ control method for grid-connected inverters which is suitable for weak grids. A single-phase grid-connected inverter is used as an example to establish a robust H∞ control model for a grid-conneeted inverter under a weak grid and to prove that the weak grid characteristics will cause the system parameter, control input parameter and interference input parameter are perturbed, which affects the stability and interference suppression performance of the system. In order to overcome the influence of weak grid characteristics and improve the stability and interference suppression performance of the system, an improved H∞ control method for grid-connected inverter in weak power grid is proposed. In this method, indirect control is introduced to dynamically adjust the voltage of the common connection point and to eliminate the parameter perturbation of the control system, which makes the grid-connected inverter adaptable to the weak grid. Finally, the rationality and validity of the theoretical analysis and the improved H∞ control method are verified by the experiments.