Distributed Protection Scheme And Implementation For Active Distribution Network

As a highly efficient method of energy utilization,more and more Distributed Generations(DG)are being integrated to the Distribution Network duo to world energy crisis and environment pollution.The protection and control of the distribution network are facing new challenges with the introduction of DG on distribution network.Therefore,it has bright application prospects to perform related researches on Active Distribution Network(ADN)protection and control scheme and to develop ADN protection and control devices.This thesis's main contents are as follow:(1)A distributed protection scheme based on smart terminal units(STU)is proposed.It consists of three parts,including distributed fault location,isolation and power service restoration for feeder,anti-island protection considering low voltage ride through(LVRT),as well as topology self-identification based on TCP/IP protocol.Feeder fault section can be located and isolated automatically,and the power service can be restored quickly by the information interaction between STUs.As for unintentional island in which the DG energizes a portion of the area electric powersystem,with the proposed scheme,anti-island protection can be coordinated with LVRT and self-healing of ADN perfectly.(2)Distributed protection and control prototypes of active distribution network are developed.The protection prototype hardware is composed of microprocessors,field programmable logic arrays(FPGAs),analog-to-digital converters(ADCs),and memory.It has a powerful data processing capability and provides strong support for distributed protection and control programs.Based on the concept of hierarchical,modular and multitasking,the advanced application program of distributed protection and control function of active distribution network is designed,which can realize data processing,protection control and anti-island protection.The active distribution network protection devices are developed based on the distributed protection scheme.Hardware structure and software process are designed.The device adopts a hierarchical,modular,multitasking software design concept and consists of two parts,system software and application software.The function of system software is access the data provided by hardware and provide service for upper application software.And the ADN protection function is realized by application software.Device's main processes include data processing process,protection and control process,anti-island protection process and message processing process.(3)RTDS was used to build the active distribution network test model to complete the closed-loop test of the developed prototype.Based on real distribution network parameter,the active distribution system model with inverted DG is set up.The function and performance test of four active distribution network protection prototypes are carried out according to different fault conditions.The test results show that the proposed distributed protection control scheme can meet the requirements of the rapid fault self-healing of the active distribution network.The developed prototype has stable performance and reliable operation,and has certain engineering application prospect.