高渗透率下一种提高LCL滤波并网逆变器鲁棒性的新型锁相环设计方案

A New Phase-locked Loop Design Scheme to Improve the Robustness of LCL Filtered Grid-connected Inverters Under High Permeability

高渗透率下LCL滤波并网逆变器可能因锁相环与电网阻抗的交互影响而引发系统失稳问题。基于上述背景,首先建立考虑电网阻抗影响时的锁相环等效控制框图,利用锁相环输出相角与扰动量之间的函数关系揭示系统鲁棒性下降的主要原因,剖析传统前置滤波器锁相环存在的主要弊端。鉴于此,从优化锁相环控制结构角度考虑,提出一种新型锁相环设计方案,并对所提锁相环的等效传递函数进行推导,同时通过设计示例给出具体的参数设计方法。理论分析表明,所提新型锁相环拥有和传统前置二阶低通滤波器锁相环相同的谐波衰减特性,系统鲁棒性得到保证,并且无需额外的相位补偿环节即可实现并网公共点单位功率因数入网。最后,通过仿真和实验结果验证所提新型锁相环设计方案的有效性。

Under high permeability,LCL filtered grid-connected inverters may cause system instability due to the interaction of phase locked loop(PLL)and grid impedance.Based on the above background,the equivalent control block diagram of PLL considering the influence of grid impedance is established.By using the function relation between the output phase angle of PLL and the disturbance quantity,the main reason of the system robustness decline is revealed,and the main disadvantages of the traditional pre-filter PLL are analyzed.In view of this,from the perspective of optimizing the control structure of PLL,a new design scheme of PLL is proposed,and the equivalent transfer function of the proposed PLL is deduced.At the same time,the specific parameter design method is given through the design example.Theoretical analysis shows that the proposed new PLL has the same harmonic attenuation characteristics as the traditional pre-second-order low-pass filter PLL,the robustness of the system is guaranteed,and the unit power factor of grid connected common point can be realized without additional phase compensation link.Finally,the effectiveness of the proposed new PLL design scheme is verified by simulation and experimental results.