Research On The Impact Of New Energy Centralized Access On Power Network Protection And The Countermeasure

With the increasing attention and vigorous development of clean energy,the development of renewable energy,such as wind power and photovoltaic energy,has been high-speed development.Due to the constraints of natural conditions,China generally presents the technical characteristics of "large scale,concentrated density" in the use of new energy power.As new energy mostly feeds power into the power grid in the form of centralized access,with the large-scale access of new energy sources to power grid,its complex fault characteristics bring many new problems and challenges to relay protection.In this paper,based on the actual situation of regional power grid in a certain area,the impact of new energy sources on power grid protection and the corresponding strategies are studied systematically by theory and simulation.The short-circuit current characteristics fed by new energy sources are the main factors affecting the relay protection performance of power grid.According to the access status of different types of new energy plants in a regional power grid,the short-circuit current characteristics of doubly-fed power supply and inverted power supply(photovoltaic and direct-drive wind power)are studied theoretically.The basic composition,attenuation characteristics,main influencing factors of short-circuit current of two kinds of new energy sources and the differences between the short-circuit current characteristics of traditional synchronous generators are analyzed and summarized.The analysis conclusion can provide reference and guidance for the performance evaluation and improvement of related protection.In order to analyze the impact of new energy access on relay protection more comprehensively,this paper designs and constructs a simulation platform for fault transient characteristics analysis and protection performance evaluation of power grid.Based on the access point of new energy plant,according to the short-circuit current impact area and the performance evaluation requirements of relay protection,the local equivalence of primary power grid is processed to improve the simulation efficiency.According to the actual protection configuration of the power grid and the protection principle and algorithm adopted,the software module of the secondary protection system is developed,and the precise simulation of the operation characteristics of the protection device is realized.The simulation platform provides a powerful tool for analysis and evaluation of relay protection performance.Based on the developed simulation platform,the operational performance of tie-line distance protection and current differential protection in new energy plant is analyzed and evaluated,including phase selector,impedance element and direction element of different principles.Aiming at the existing problems,an improved scheme of fault phase selector and directional element suitable for new energy access is proposed.The correctness of the improved scheme is verified by digital simulation.Finally,the paper summarizes the work done and looks forward to the next research work.