自适应三次谐波注入的回接型LCL光伏逆变器共模谐振电流抑制方法  

Common-Mode Resonant Current Suppression for Back-Connected LCL Photovoltaic Inverter Using Adaptive Third Harmonic Injection

作　　者：张洪亮[1] 张子成[1] 陈杰 邢相洋[1] Zhang Hongliang;Zhang Zicheng;Chen Jie;Xing Xiangyang(School of Control Science and Engineering Shandong University,Jinan 250061 China;Huawei Digital Power Technologies Co.Ltd,Shanghai 201206 China)

机构地区：[1]山东大学控制科学与工程学院,济南250061 [2]华为数字能源技术有限公司,上海201206

出　　处：《电工技术学报》2023年第1期220-233,共14页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金资助项目(61821004,61733010)。

摘　　要：三电平逆变器具有损耗小、谐波低等优势,在非隔离型光伏系统中广泛应用。因其常采用中点回接型LCL滤波器抑制漏电流,易引发共模谐振电流,影响并网系统稳定性。为此,该文揭示了共模谐振电流的产生机理,研究了调制策略对共模谐振电流的影响。提出一种自适应3次谐波注入算法,有效降低了共模谐振电流。首先,为保证调制的正确性,推导了3次谐波注入系数的取值范围;然后,根据直流电压和调制度,提出了3次谐波注入系数的自适应律,以提升逆变器系统并网性能;最后,为便于工程应用,降低控制器的计算负担,推导了基于电流闭环控制的3次谐波注入实现方法,该方法计算量小、稳定性好、适用范围广。该方法为3次谐波注入调制算法的应用提供了理论支撑和实现途径,具有较强的工程应用价值。仿真和实验结果证明了不同工况下提出方法的正确性及有效性。Due to the parasitic capacitance between the photovoltaic array and the ground, the leakage current is easily generated in non-isolated photovoltaic grid-connected system, which will reduce the equipment life and endanger personal safety. Therefore, the modified LCL filter with neutral-point back connection is often adopted for non-isolated system to provide a low-impedance bypass path and suppress the leakage current.However, the LCL filter modification brings potential risk of common-mode(CM) resonance in CM loop which will cause inverter-side current oscillation, leakage current increment, and system instability. Passive and active damping methods have been proposed to overcome the drawback of CM current but will bring extra power losses or complex controller design tasks. To address the CM resonance issue, this paper proposes an adaptive third harmonic injection algorithm based on the analysis of different modulation strategy influences on the CM resonant current.Firstly, the mathematical model and generation mechanism of CM resonant current are introduced briefly and the CM voltage spectrums of space vector pulse width modulation(SVPWM) method, saddle pulse width modulation(SAPWM) method and third harmonic injection pulse width modulation(THIPWM) method are compared, which shows the advantage of THIPWM method on CM resonant current suppression. Secondly, the exact available range of the third-harmonic injection coefficient is derived to ensure the correctness of modulation and determine the adjustable range of the coefficient. Thirdly, according to DC voltage and modulation index, an adaptive law for the injection coefficient is proposed to improve the performance of the grid-connected inverter.Fourthly, the third-harmonic injection implementation method for current closed-loop control is derived in order to facilitate engineering application and reduce the calculation burden of the controller.To verify the effectiveness of the proposed method, simulation and experiment are performed on Matlab/Simulink platf

关 键 词：非隔离型光伏系统 共模谐振电流抑制 自适应3次谐波注入调制 闭环控制算法 

分 类 号：TM46[电气工程—电器]