数字控制下LCL型并网逆变器的环路滞后补偿方法

A method of loop lag compensation for LCL-type grid-connected inverters under digital control

基于数字控制的LCL型并网逆变器会产生不可忽略的控制延时,使系统表现为非最小相位特性,而用于抑制LCL谐振的有源阻尼方法受控制延时影响,大幅改变了开环增益的相频曲线,在电网阻抗宽泛变化的弱电网中,系统鲁棒性将严重降低。文中从系统开环增益的特性入手,提出一种环路滞后补偿方法,合理设计了滞后环节的补偿参数,详细分析了所提方法在弱电网中的鲁棒性,分析结果表明该方法可分离阻尼分界频率与环路一次穿越频率,能保证系统良好的适应弱电网,最后通过仿真模型验证了理论分析的正确性与所提方法的有效性。

The LCL-type grid-connected inverters based on digital control will produce control delay which cannot be ignored,resulting in the system presents characteristics of non-minimum phase.However,the active damping methods which are used to suppress LCL resonance are influenced by control delay,the phase-frequency curve of open loop gain is greatly changed.In the weak grid with wide variation of grid impedance,the robustness of system will be seriously reduced.Starting from the characteristics of the loop open gain of the system,a method of loop lag compensation is proposed in this paper,the compensation parameters of the lag link are reasonably designed,and the robustness of the system is analyzed in detail in the weak grid.The analysis results show that this strategy can separate the frequency of damping dividing and the frequency of first loop through,and can ensure that the system well adapts the weak grid.Finally,the correctness of the theoretical analysis and the effectiveness of the strategy are verified by the simulation model.