摘要
LCL滤波器广泛应用于并联系统中,这种滤波器的结构有利于环流抑制和功率均分,但在非线性工况下容易在负载侧产生较大的谐波电压。针对环流抑制与电压质量控制的矛盾,对400 Hz逆变器等效阻抗进行了分析,揭示了输出电压闭环控制与引入输出电流前馈的电容电压闭环控制是等效的,可以减少谐波电压,但也削弱了负载侧电感的环流抑制作用。在此基础上,提出采用多比例谐振控制器和负载电流前馈构成虚拟负谐波阻抗,以重塑逆变器在低次谐波处的等效输出阻抗为小阻抗,从而减小谐波电压。通过采用不同基准的多比例谐振控制技术,实现了分频段阻抗重塑,使滤波器在基波和高次谐波频率处仍具有环流抑制功能。最后,使用下垂控制策略对两台逆变器进行了并联实验研究,实验结果验证了所提技术方案的有效性。
LCL filter is widely applied in parallel inverter systems because its structure is suitable to suppress circulating current,as well as to share power.However,large voltage harmonics are also readily to appear on load side when inverter connects with nonlinear loads.Considering the contradiction between circulating current suppression and voltage quality control,analysis of 400 Hz inverter’s equivalent impedance was carried out,which revealed that the output voltage feedback control was equivalent to the capacitor voltage feedback control with output current feedforward.The output voltage feedback control can eliminate the harmonics,but it also weakens the suppression of circulating current.A scheme using a multiple proportional resonance(MPR)controller and load current feedforward to form a virtual negative harmonic impedance was proposed,with which the inverter’s equivalent output impedance at low-order harmonic frequencies was reshaped to a small impedance,thereby reducing harmonic voltage drop.Furthermore,different references were adopted for MPR to realize the impedance reshaping with respect to frequency bands,which enabled the filter retain the circulating current suppression at fundamental frequency and high-order harmonics frequency band.Finally,two LCL-type inverters in parallel were tested with droop control strategy,and the experimental results verified effectiveness of the proposed method.
作者
刘海春
费涛
温鹏召
谢少军
LIU Hai-chun;FEI Tao;WEN Peng-zhao;XIE Shao-jun(College of Automation Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 211100,China)
出处
《电机与控制学报》
EI
CSCD
北大核心
2021年第9期26-34,共9页
Electric Machines and Control
基金
国家自然科学基金(51877104)。
