基于虚拟阻抗重塑的变压器耦合逆变器控制策略  

Control Strategy of a Transformer-Coupled Inverter Based on Virtual Impedance Reshaping

作　　者：洪芦诚[1] 安闪闪 徐佳裕 唐润悦 Hong Lucheng;An Shanshan;Xu Jiayu;Tang Runyue(School of Electrical Engineering,Southeast University,Nanjing 210096,China;State Grid Hangzhou Power Supply Company,Hangzhou 310020,China)

机构地区：[1]东南大学电气工程学院,南京210096 [2]国网浙江省电力有限公司杭州供电公司,杭州310020

出　　处：《天津大学学报（自然科学与工程技术版）》2021年第12期1280-1288,共9页Journal of Tianjin University：Science and Technology

基　　金：国家自然科学基金资助项目(52077039).

摘　　要：随着能源变革以及新能源技术的迅猛发展,三相LCL型并网逆变器被广泛应用于新能源并网.对于通过变压器耦合并网的逆变器,利用变压器的自身感抗,LCL滤波器设计时往往省去电网侧的滤波电感,实现变压器与无源滤波器的集成化设计.传统的电网电压全前馈控制策略应用于此系统时,全前馈函数的一阶微分项与电容电流反馈有源阻尼项抵消,使得原来的电容电流内环控制不再起作用.此时,前馈函数的剩余项可定义为并联在电容两端的虚拟阻抗,为LCL滤波器的谐振峰提供阻尼.然而,该虚拟阻抗的实部在特定的频率范围内为负将向系统引入负阻尼,严重时可能诱发系统失稳.针对该问题,提出了一种虚拟阻抗重塑的方法,对传统的电网电压全前馈控制策略进行了修正,修正后的控制策略能够在保证电网背景谐波抑制能力的基础上有效抑制LCL滤波器的谐振峰,从而避免了系统可能面临的失稳风险.对阻抗重塑后的逆变器并网系统进行稳定性分析,结果表明阻抗重塑后的逆变器控制策略相比于未重塑的控制策略具有更大的稳定裕度.此外分析可知虚拟阻抗重塑的比例前馈项对低频电网背景谐波具有很好的抑制作用,而二阶微分前馈项对高频的抑制效果明显.最后基于PSCAD/EMTDC仿真平台搭建了系统的仿真模型,验证了提出方法的有效性.With the rapid development of energy reform and new energy technology,three-phase LCL gridconnected inverters are widely used in new energy grid-connections.For inverters coupled to the grid through a transformer,using the transformer’s own inductance,the filter inductance on the grid side is often omitted in the design of the LCL filter to realize the integrated design of the transformer and the passive filter.When the traditional grid voltage full feedforward control strategy is applied to this system,the derivative term of the full feedforward function cancels out the capacitive current feedback active damping term,so that the original capacitive current inner loop control no longer works.At this time,the remaining term of the feedforward function can be defined as the virtual impedance connected in parallel across the capacitor to provide damping for the resonance peak of the LCL filter.However,the real part of the virtual impedance is negative in a specific frequency range,which will introduce negative damping to the system.This,in turn,may induce system instability in severe cases.In response to this problem,a virtual impedance reshaping method is proposed to modify the traditional grid voltage full feedforward control strategy.The modified control strategy can effectively suppress the resonance peak of the LCL filter on the basis of ensuring the suppression of the background harmonics of the power grid,thereby avoiding the risk of instability that the system may face.The stability analysis of the inverter grid-connected system after impedance remodeling shows that the inverter control strategy after impedance remodeling has a larger stability margin than previously.In addition,the analysis shows that the proportional feedforward term of virtual impedance reshaping has a good suppression effect on low-frequency power grid background harmonics,while the second-order differential feedforward term has a significant suppression effect on high frequencies.A simulation model of the system was built based on the

关 键 词：并网逆变器 电网背景谐波 电网电压全前馈 稳定性 

分 类 号：TM712[电气工程—电力系统及自动化]