Research On Fault Feature And Protection Principle In Micro-grid

With the penetration rate of power electronic devices rapidly increasing in power systems,new energy grid-connected power generation,flexible DC transmission,reactive power compensation,and AC drives are widely used.Electromagnetic conversion equipment is gradually being replaced by power electronic conversion equipment.Power electronics dominated power systems will become a new trend in the development of modern power systems.However,the use of large-scale power electronic devices is bound to change the fault characteristics of traditional power systems,resulting in the protection of traditional power systems can not meet the requirements of the new fault characteristics.The fault characteristics analysis of power electronic power system and the relay protection technology under the new situation have not yet been effectively studied.Therefore,it is necessary to analyze the fault characteristics of the power electronic power system and provide new basis for its fault location and protection,and make it safe,stable and efficient long-term operate.Microgrid is a low-voltage autonomous distribution network,which is a typical power electronic distribution system.This article takes the microgrid as an object to study its fault characteristics and protection principles.The specific work is briefly described as follows:(1)This article first investigated the research status of microgrid fault analysis and its protection,followed by the introduction of distributed power supply modeling,and introduced the distributed power supply control strategy in detail,to study the faults under different control strategies.The characteristics laid the foundation.(2)Then theoretically detailed analysis of the distributed power supply fault output characteristics under different control strategies,as well as the fault characteristics of the micro-grid system with micro-grid system connected to the grid and islanding in two operating states,and through the simulation software Modeling it for simulation verification.(3)Afterwards,based on the fault characteristics analyzed in Chapter 2,the influence of the distributed power access on the protection of the power distribution system is analyzed in detail.Based on the new features of the microgrid,the EtherCAT centralized longitudinal differential protection scheme is proposed.By setting up a failure analysis module in the upper computer,a centralized protection system is formed to integrate the protection and control of the micro-grid and achieve fast protection and fault location of the whole micro-network.(4)Finally,with the aid of the microgrid experimental platform,the above protection and positioning principle is implemented on TwinCAT,and the accuracy of the fault location and the correctness of the centralized protection algorithm are verified through experiments.