三相LCL型并网逆变器的阻抗建模及特性分析

Impedance modeling and characteristic analysis of three-phase LCL-type grid-connected inverters

考虑锁相环、电流调节器(含dq轴解耦系数)、LCL型滤波器等环节,并计及运行工作点,采用谐波线性化的方法建立了三相LCL型并网逆变器正、负序阻抗模型,并基于PSCAD/EMTDC对阻抗模型进行仿真验证。详细分析了锁相环、电流调节器控制参数及滤波器参数对阻抗特性的影响,结果表明:锁相环比例和积分增益对并网逆变器阻抗特性的影响主要在工频附近,而电流调节器比例和积分增益则在次同步和超同步频域均有一定的影响;锁相环和电流调节器积分增益主要影响逆变器工频附近的幅频特性和相频特性;电流调节器比例增益对逆变器正序阻抗特性的影响较大,而锁相环比例增益的影响较小。

Considering the PLL(Phase Locked Loop),current regulator(including dq-axis decoupling coefficient),LCL filter,etc.,and taking into account the operating point,the positive and negative sequence impedance models of three-phase LCL grid-connected inverter are established by harmonic linearization method and verified by PSCAD/EMTDC. The effects of the control parameters of PLL,current regulator and filter on impedance characteristics are analyzed in detail. The results show that the influence of the proportional and integral gains of PLL on the impedance characteristics of grid-connected inverter is mainly in the vicinity of the base frequency,and the proportional and integral gains of current regulator have certain influence in the sub synchronous and super synchronous frequency domains. The integral gains of PLL and current loop mainly affect the amplitude-frequency characteristics and phase-frequency characteristics of inverter near the base frequency. The proportional gain of current regulator has a great influence on the positive sequence impedance characteristics of inverter,while the proportional gain of PLL has less influence.