基于阻抗分析法的三相LCL型并网逆变器附加有源阻尼设计

Design of Additional Active Damping for Three-phase LCL Grid Connected Inverter Based on Impedance Analysis Method

三相LCL型并网逆变器系统中,由于设备与系统间的交互作用可能会造成谐波振荡,严重影响系统正常运行。针对该问题,采用谐波线性化的方法,计及耦合补偿项网侧电压的影响修正阻抗模型,建立了修正后的三相LCL型并网逆变器序阻抗模型,同时从谐振原理及对数频率稳定性角度进行稳定性分析,揭示光伏并网系统高频谐振产生的机理;基于得到的并网系统阻抗特性,针对结合电容电流反馈及串联超前校正的附加有源阻尼环节,考虑阻抗特性曲线进行阻尼环节参数选取,对易振荡频段进行阻抗重塑。最后,基于Matlab/Simulink仿真平台验证了该方法的正确性和有效性。研究结果表明:附加有源阻尼环节能有效抑制谐波振荡且具有较好动态特性。

In the three-phase LCL grid connected inverter system,due to the interaction between equipment and system,harmonic oscillation may occur,which seriously affects the normal operation of the system.In order to solve this problem,the harmonic linearization method is adopted to modify the impedance model considering the influence of grid side voltage of coupling compensation term,and the modified sequence impedance model of three-phase LCL grid connected inverter is established.At the same time,stability analysis is conducted from the perspective of resonance principle and logarithmic frequency stability to reveal the generation mechanism of high-frequency resonance in photovoltaic grid connected system.The impedance characteristic curve is taken into consideration,the parameters of the damping link are selected,and the impedance is reconstructed in the frequency band which is easy to oscillate.Finally,based on the Matlab/Simulink simulation platform,the correctness and effectiveness of the method are verified.The results show that the additional active damping link can effectively suppress harmonic oscillation and has good dynamic characteristics.