Asymmetrical Fault Current Calculation Method and Influencing Factors Analysis of Droop-Controlled Inverters  

作　　者：Huimin Zhao Zhikang Shuai Jun Ge An Luo Weimin Wu Z.John Shen 

机构地区：[1]College of Electrical and Information Engineering,Hunan University,Changsha 410006,China [2]Electrical Engineering Department,Shanghai Maritime University,Shanghai 201306,China [3]Department of Electrical and Computer Engineering,Ilinois Institute of Technology,Chicago,IL 60616 USA

出　　处：《CSEE Journal of Power and Energy Systems》2024年第2期562-573,共12页中国电机工程学会电力与能源系统学报（英文）

基　　金：supported by National Natural Science Foundation of China under Grant 51977066。

摘　　要：Since the fault dynamic of droop-controlled inverter is different from synchronous generators (SGs), protection devices may become invalid, and the fault overcurrent may damage power electronic devices and threaten the safety of the microgrid. Therefore, it is imperative to conduct a comprehensive fault analysis of the inverter to guide the design of protection schemes. However, due to the complexity of droop control strategy, existing literatures have simplified asymmetric fault analysis of droop-controlled inverters to varying degrees. Therefore, accurate fault analysis of a droop-controlled inverter is needed. In this paper, by analyzing the control system, an accurate fault model is established. Based on this, a calculation method for instantaneous asymmetrical fault current is proposed. In addition, the current components and current characteristics are analyzed. It was determined that fault currents are affected by control loops, fault types, fault distance and nonlinear limiters. In particular, the influences of limiters on the fault model, fault current calculation and fault current characteristics were analyzed. Through detailed analysis, it was found that dynamics of the control loop cannot be ignored, the fault type and fault distance determine fault current level, and part of the limiters will totally change the fault current trend. Finally, calculation and experimental results verify the correctness of the proposed method.

关 键 词：Asymmetrical fault analysis droop control fault current calculation method LIMITER transient fault characteristics 

分 类 号：TM721.1[电气工程—电力系统及自动化]