中点钳位型三电平逆变器并联系统的零序环流抑制策略  

Zero-Sequence Circulating Current Suppression Strategy of Neutral-Point-Clamped Three-Level Inverter Parallel System

作　　者：徐畅 宫金武[1] 张国琴 代克民 查晓明[1] Xu Chang;Gong Jinwu;Zhang Guoqin;Dai Kemin;Zha Xiaoming(School of Electrical Engineering and Automation Wuhan University Wuhan 430072,China;School of Electronics and Electrical Engineering Wuhan Textile University Wuhan 430200,China)

机构地区：[1]武汉大学电气与自动化学院,武汉430072 [2]武汉纺织大学电子与电气工程学院,武汉430200

出　　处：《电工技术学报》2023年第S01期124-135,共12页Transactions of China Electrotechnical Society

基　　金：国防科工局稳定支持项目(6142217200403);国家自然科学基金项目(52177191)资助。

摘　　要：针对中点钳位型(NPC)三电平逆变器并联系统内普遍存在的零序环流问题,该文首先分析模块间环流的通路,建立零序环流的电路和数学模型。根据等效模型阐述零序环流各成分的产生机制,并对零序环流进行定量分析。定义零序环流的三类具体成分:通态零序环流、开关零序环流及混合零序环流。对于不同类别的零序环流,提出共享直流侧中线和改进型LCL滤波器的硬件措施及准比例积分谐振(PIR)控制器的软件措施去抑制对应环流成分的高频、低频分量;另外,针对改进型LCL滤波器中交流滤波电容中点和直流侧电容中点连接电缆上有较大高频电流的缺陷,提出载波移相控制下模块共用滤波电容的优化方案,在保证环流抑制效果的同时将奇数次开关频率的高频纹波转移到共用电容上,实现奇数纹波分量的自动抵消,使连接电缆上的电流减小近50%;最后,仿真与实验结果验证了所提环流抑制策略的可行性。Parallel operation of inverters is the most common and direct means to improve power capacity and power level.However,in parallel inverter system,zero-sequence circulating current(ZSCC)occurs because of the common AC and DC bus.This will lead to distortion of output current and additional device loss,which seriously threatens the stability of the parallel system.The ZSCC of neutral-point-clamped(NPC)three-level inverter parallel system studied in this paper is more complex than that of the two-level parallel inverters,and it is necessary to take both hardware and software measures to suppress it.Most of the existing studies focused on software control strategies to suppress ZSCC.For the use of hardware measures,following the traditional scheme was a common choice.Few studies have been done to improve the traditional hardware measures.This paper optimizes the connecting pattern of the improved LCL,which is a traditional hardware measure commonly used to suppress ZSCC,and forms a module shared capacitance scheme under carrier phase-shifting control.Compared with the traditional improved LCL,the added connection cable has smaller current ripple.Firstly,the loop of circulating circuit is analyzed according to the switch state of the bridge-leg,and the mathematical and circuit model of ZSCC are established.The circulating current is also quantified by Fourier decomposition.Then,a switch function is introduced to further refine the category of ZSCC.For different types of ZSCC,the generation mechanism is explained,and hardware measures of sharing DC side midline and improved LCL and software measures of quasi-proportional-integral-resonance controller are proposed to suppress the corresponding ZSCC.Simulations and experiments show the validity of the proposed measures.At the same time,experiments show that the proposed methods are also feasible when hardware parameters of each inverter are inconsistent and the inverter modules are put in or removed.In addition,it should be noted that there is a large high frequency curr

关 键 词：三电平中点钳位型逆变器 逆变器并联系统 零序环流抑制 准比例积分谐振控制 模块共用滤波电容 载波移相控制 

分 类 号：TM464[电气工程—电器]