Research On Optimization Of Inverse Time Overcurrent Protection Based On Improved Particle Swarm Optimization Algorithm

In today's society,human survival and development are closely related to electricity.Traditional power generation technologies have problems such as low energy utilization rate and environmental pollution.Distributed energy sources such as wind energy and solar energy have the advantages,which brings dawn to the innovation of power generation technology.The rise of Distributed Generation(DG)technology has brought dawn to people.DG supplies are widely used and popularized for their convenience,flexibility,low carbon,environmental protection,and high efficiency.DG supplies bring convenience to people and bring some problems.After the DG supply is connected to the grid,the fault current level in the distribution network changes,and the power flow direction becomes uncertain.Therefore,the setting value of the original relay in the distribution network is no longer applicable to the new system after the DG supply is connected.If the relay still uses the original setting value,it will cause the relay to not operate correctly.Therefore,it is necessary to re-optimize the setting value of the distributed protection after the DG supply is connected to the distribution network.This paper introduces the research background and significance of relay protection setting optimization calculations considering distributed generation,as well as the latest research results and research status at home and abroad.The traditional setting and matching methods of inverse time overcurrent protection are introduced in detail,and the DG supply is connected to the distribution network from different locations and with different capacities through Matlab/Simulink software simulation.Impact on inverse time overcurrent protection in the distribution network.Converting the inverse time-limited overcurrent protection setting tuning optimization problem of distributed generation into mathematical problem solving.When establishing the objective function,consider the three uncertainties of fault line,fault type and fault point position,aiming at the shortest sum of the total action time of all inverse time overcurrent protection in the system.When establishing constraints,consider the inherent properties of the relay and the selectivity,quickness,sensitivity,and reliability requirements of relay protection.In order to simplify the coordination relationship of protection and improve the computational efficiency,and in order to improve the quickness of protection,the principle of “near backup protection” is proposed when the primary and backup protection are combined.The effectiveness and rationality of the proposed mathematical model are verified by simulation examples.In this paper,the particle swarm optimization algorithm is used to solve the mathematical model.Two problems are proposed for the problem that the particle swarm algorithm is easy to fall into the local optimal solution.According to the need of the amount to be optimized,the particles are first discretized,and then the concept of “local maxima” is introduced to improve the particle update process.Finally,the effectiveness of the algorithm is verified by simulation examples.Through the establishment of the mathematical model and the improvement of the algorithm,the optimization problem of the inverse time limit overcurrent protection setting calculation considering the DG is solved.