LCL滤波电压源并网逆变器多环控制策略设计

摘要

电压源并网逆变器交流侧采用LCL滤波器进行滤波,在获得较好滤波效果的同时,也增加了系统复杂性,降低了系统稳定性.逆变器并网电能质量及其功率因数,尤其在非理想电网条件下,通常需要直接并网电流控制加以确保.而桥臂侧电流的控制能较好地将桥臂电流限制在电力电子功率模块的允许范围内,并且较好的桥臂电流有利于电力电子功率模块的有效工作.为实现上述目的,针对LCL滤波电压源并网逆变器,设计了以桥臂电流、电容电压以及并网电流为反馈量的串联多环控制策略.同时为了较好地抑制系统振荡,提高系统阻尼特性,在桥臂电流内环中增加了基于超前滞后网络的有源阻尼控制技术,构成有源阻尼多环复合控制方案.文中对多环控制系统设计及有源阻尼环节参数选取等问题进行了讨论.通过对11 kw的LCL滤波并网逆变器进行仿真与实验,验证了理论分析和方案设计的正确性.%Although harmonics in AC side of a grid-connected voltage source inverter (VSI) can be filtered out with LCL filter better than with L filter, the three-order characteristic of LCL filter makes the system complicated and unstable. It is found that the power factor and power quality of the grid-connected VSI can be guaranteed only by direct grid-side current control, especially under the non-ideal grid condition. And at the same time, the arm current can be better limited to allowable value of power electronic block by arm current control of VSI, and it is in favor of effective operation of power electronic block. So a cascaded control strategy with multiple feedback loop, namely arm current of VSI, capacitor voltage and grid-side current, is designed in this paper. Meanwhile, in order to restrain the inherent system resonance and increase the damping ratio of LCL filter, a lead-lag element for active damping is added to the inner control loop of arm current of VSI. So a composite multiple feedback control strategy is achieved. Besides, the design method of multiple feedback loop control and the parameter selection of lead-lag element are discussed. The theoretical analysis and design scheme are verified by simulation and experiments on a 11 kW LCL-VSI system.