弱电网下锁相环对三相LCL型并网逆变器小扰动建模影响及稳定性分析  

Effect of Phase Locked Loop on the Small-signal Perturbation Modeling and Stability Analysis for Three-phase LCL-type Grid-connected Inverter in Weak Grid

作　　者：杨苓[1] 陈燕东[1] 周乐明[1] 陈智勇[1] 周小平[1] 伍文华[1] 黄旭程[1] 谢志为 罗安[1] YANG Ling;CHEN Yandong;ZHOU Leming;CHEN Zhiyong;ZHOU Xiaoping;WU Wenhua;HUANG Xucheng;XIE Zhiwei;LUO An(National Electric Power Conversion and Control Engineering Technology Research Center（Hunan University）,Changsha 410082,Hunan Province,China)

机构地区：[1]国家电能变换与控制工程技术研究中心(湖南大学)

出　　处：《中国电机工程学报》2018年第13期3792-3804,共13页Proceedings of the CSEE

基　　金：国家重点研发计划项目(2017YFB0902000);国家电网公司科技项目(SGXJ0000KXJS1700841)~~

摘　　要：在弱电网中,由于锁相环（phase locked loop,PLL）的PI控制器的动态性能,三相LCL型并网逆变器在小扰动情况下控制dq坐标系和系统dq坐标系不再重合,给系统建模与稳定性分析带来困难。为此,提出一种基于导纳模型的三相LCL型并网逆变器小扰动建模方法。首先,通过旋转矩阵,将系统dq坐标系下参数变换到控制dq坐标系,建立双dq坐标系之间的交互关系,解决了考虑PLL影响的三相LCL型并网逆变器建模难题。其次,深入研究并网逆变器的输出导纳特性。然后,分析PLL、电网阻抗和LCL滤波器参数在系统dq坐标系下对系统稳定性的影响。随着PLL带宽和电网阻抗的增大,系统由稳定变为不稳定。当系统处于稳态时,有源阻尼系数越大,系统的相角裕度越大,表明系统稳定性提高。逆变器侧电感的变化,对系统稳定性的影响很小。滤波电容和网侧电感的增大,导致系统的相角裕度减小,系统稳定性降低。最后,仿真和实验验证了理论分析的正确性。In the weak grid, due to the dynamics of PI controller in the phase locked loop（PLL）, the control dq frame is no longer aligned with the system dq frame for three-phase LCL-type grid-connected inverter when a small-signal perturbation is added to the grid voltage. That will bring difficulties to the system modeling and stability analysis. Thus, a small-signal perturbation modeling method for three-phase LCL-type grid-connected inverter is proposed based on admittance model. Firstly, by the rotating matrix, the parameters in the system dq frame are transformed into the control dq frame, and the interaction between the two dq frames is established. It solves the modeling problem for three-phase LCL-type grid-connected inverter considering the effect of PLL. Secondly, the characteristics of the grid-connected inverter output admittance are analyzed deeply. Then, the effects of PLL, grid impedance and LCL filter parameters on system stability are analyzed in the system dq frame. As a conclusion, with increase in PLL bandwidth and grid impedance, the system stability gradually is decreased, even resulting in the system instability. In a steady state, the larger the active damping coefficient is, the greater the phase margin of the system is, indicating the system stability is improved. And the variation of the inverter inductance has the smaller impact on the system stability. While, the increase of the filter capacitance and grid inductance leads to the decrease of the phase margin and reduces the system stability. Finally,the simulation and experimental results verify the validity of the theoretical analysis.

关 键 词：可再生能源发电 弱电网 三相LCL型并网逆变器 小扰动导纳建模 锁相环 

分 类 号：TM464[电气工程—电器]