基于双二阶滤波器的LCL型并网逆变器延时补偿方法

A delay compensation method based on a biquad filter for an LCL-type grid-connected inverter

为了抑制LCL型滤波器的谐振尖峰,电容电流反馈有源阻尼被广泛应用于LCL型并网逆变器中。由于数字控制延时带来的不利影响,电容电流反馈有源阻尼的阻尼性能被严重削弱。负阻尼区域出现在f_(s)/6到f_(s)/2之间,减弱了并网逆变器的稳定性和对电网阻抗变化下的鲁棒性。在电容电流反馈通道上插入一个双二阶滤波器来补偿数字控制延时带来的相位滞后,正阻尼范围可以扩展到f_(s)/3,从而实现了对电网阻抗变化的高鲁棒性。选择了合适的离散化方法,分析了补偿后的系统稳定性。提出了一个详细的闭环参数设计流程,以获得良好的控制性能。最后,实验结果验证所提方法的有效性和参数设计流程的可行性。

To attenuate the LCL filter resonance peak,capacitor-current-feedback active damping is widely used in an LCL-type grid-connected inverter.Because of the adverse effect introduced by the digital control delay,the performance of capacitor-current-feedback active damping significantly deteriorates.The negative damping region appears from f_(s)/6 to f_(s)/2.This weakens the stability and robustness of the grid-connected inverter against the grid impedance variation.A biquad filter is adopted to insert into the capacitor-current-feedback path to compensate for the phase-lag resulting from the digital control delay.The positive damping region can be expanded to f_(s)/3,thus achieving high robustness against grid impedance variation.The proper discrete method is chosen and the system stability after compensation is analyzed.Also,a detailed close-loop parameter design procedure is presented to obtain better control performance.Finally,experimental results are provided to verify the effectiveness of the proposed method and the feasibility of the parameter design procedure.