Research On Distribution Network Protection And Control System With Block Chain

The development of distribution network brings a lot of problems to relay protection,as both the network structure and the characteristic of sources have changed.To recognise and isolate faults in a quick and precise way,information from remote site is necessary.However,due to the poor communication facilities,it is hard to implement the protection scheme used in high voltage network.A feasible solution is to build a dedicated protection system for distribution network,which makes use of existing communication facilities.It can be promising to utilize 5G wireless communication network to transmit protection information,but the security concern about public network must be considered.To solve this problem,a novel protection system for distribution network is built based on block chain.With the decentralized system and asymmetric encryption,the new protection system is capable of resisting cyber attack.In this system,the information about distribution network is recorded in block chain,which is visible to every node in the network,thus nodes can make decisions independently when the fault occurs,and then take actions to recover the power supply.When the structure of distribution network changes,the information saved in block chain will be updated in time,so that the protection system is capable of dealing with different operating states.Based on the new protection system,more specific research is conducted to recognise the fault precisely.The protection method used in distribution network should be capable of adapting to the changeable situation.At the same time,the influence of bad synchronization condition should also be considered.In this dissertation,5 methods which are able to work with synchronization error are compared with conventional current differential protection.The performance of different protection methods is tested in complex scenarios,considering branch line and distributed generation.The influence of fault type is also taken into consideration.Protection with positive-sequence component is also considered.Based on this analysis,a differential protection method for distribution network is proposed.This method uses fault component to calculate active power,which is capable of adapting to the complex situation.The simulation conducted in MATLAB/SIMULINK shows that this method has good performance.