Relaying Protection Strategy Of Distribution Network With Distributed Power Supply Based On MAS

Along with the development of energy reform and society,the traditional single mode of power supply can not satisfy the demand of end-users.Distributed energy systems are mostly renewable,with flexible,diverse,clean and safe characteristics,and it has become an effective way to use energy in new energy generation technologies.On the other hand,the access of distributed power can cause the distribution of power flow in the distribution system,thus affecting the correct operation of the protection system,resulting in the incorrect operation or rejection of current protection,which affects the safe and steady running of power system.In order to solve the present protection problem which is brought about by distributed power access,this thesis proposes a relay protection strategy of distribution network including distributed power based on MAS.The main work of this thesis includes the following aspects:(1)Analyzed the working principle of photovoltaic cells,the PV array output at the highest power point is controlled by a conductivity increment method in the MPPT,and is connected to the grid by inverter and PQ.Utilized BOOST boost chopper circuit for power exchange.A relevant model was established in the MATLAB/Simulink simulation environment to study the changes in output and adjustment capabilities of various parts after changes in lighting intensity.(2)In this thesis,the effect of grid connection on the distribution system current protection is analyzed.Based on the position and capacity of distributed power when it is integrated into the distribution network,the influence of upstream,downstream and adjacent feeder lines on current protection is studied respectively.The MATLAB/Simulink simulation software was used to verify the results.(3)In order to solve the problem that DG enters the power grid,the sequence component diagram of two phase short circuit and three phase short circuit failure is constructed.The setting values are recalculated,and a modified type I adaptive current protection scheme is researched.In order to satisfy the need of the largest protective scope of type-I current protection,a modified type-II cross current protection plan is proposed.In the end,MATLAB/Simulink is used to validate the performance of every protection.The results show that the scheme is feasible and effective.(4)The current protection system of distribution network with DG based on MAS is designed.This thesis introduces the principle,characteristics and structure of MAS system,proposes the auxiliary decision algorithm based on fault section location and the adaptive protection setting algorithm based on topological structure change,constructs the selective protection Agent and the adaptive protection Agent,and adaptively adjusts the protection setting by determining the fault section and selecting the corresponding scene topology structure.Finally,an example is given to verify the feasibility of the designed current protection system.