Study And Simulation On The Communication Network Of Active Distribution Network With Multi-microgrids

In order to adjust and optimize the energy structure,speeding up the development of low-carbon renewable energy technologies with the represent of the wind and light has become a consensus.However,the large-scale uncertain distributed energys resources(DERs)connecting to distribution netwrks may lead to power quality problems at the terminal of the distribution network.The bidirectional power flow caused by DERs also increases the complexity of power operation management.At present,the reasearch of microgrid is gradually transitioning from single microgrid to multi-microgrids that can realize the coordinated operation for the large-scale distributed power generation unit in the middle and low voltage distribution networks.The advantage of the microgrid is further embodied and expanded through the conception of muti-microgrids.The data acquisition,protection and control of active distribution system(ADS)with multi-microgrid neeed a strong communication system to supprot.High-speed,bidirectional,real-time,integrated communication network is the basis of multi-microgrid interaction and coordinated optimization.Summing up the results of research at home and abroad,this thesis analyzes the structure and control scheme of ADS including multi-microgrid,and summarizes the two-way interaction service and the smart terminal device in the ADS.By dividing the ADS including multi-microgrid communication system into three layers(the local layer,the access layer and the trunk layer),the specific communication schemes about different layered networks are discussed in detail.The communication data is divided into telesignalisation,telecontrol,telemetering and other data services from the perspective of communication network transmission of ADS with multi-microgrids,and their communication requirements also are analyzed detailed.Then,An evaluation system for the multi-microgrid grid-connected communication scheme is established,the evaluation of qualitative indexes is accomplished by make use of the cloud model.Subsequently,the cloud model similarity method,which is based on the expected curve,is applied to convert qualitative indexes to ration indexes.Then,the subjective and objective weights of different evaluation is determined using the analytic hierarchy process and the entropy method.Finally,the gray comprehensive evaluation method is introduced to obtain the ultimate correlation degree of different communication networking schemes.The ultimate correlation degree indicates that when the number of microgrids is small,Ethernet Passive Optical Network(EPON)-Ethernet is the preferred networking scheme for multi-microgrid grid-connected.However,considering that more microgrids will access to the ADS,Wireless Local Area Networks(WLAN)-Worldwide Interoperability for Microwave Access(Wimax)is the best networking solution.At the end of this thesis,A typical structure of gird-connected multi-microgrids is gived,and the communication networking is constructed using the Wimax and WLAN communication technology.Then the Wimax path loss model is analysed and the multi-microgrid data flow model is established.The communication simulation scenario of ADS with multi-microgrids is builed through OPNET(Optimized Network Engineering Tool)platform.Based on this scenario,the influence of transmission interval,message lengths and link layer access mechanism on the delay of the whole communication network is analyzed.