Self-healing Control Strategy Of Smart Distribution Grid

As the last link of electrical energy from production to users,distribution network plays a crucial role in power system.Self-healing control technology is the inheritance and development of traditional relay protection and distribution automation technology,and the core to confirm the safe and stable operation of intelligent distribution network.The operation state of the distribution network is split into fault state and normal operation state.For the fault state,the distribution system reacts in time,reconstructs the radial operation network through tie and section switches,and recovers the power supply of the non-fault power loss area to the maximum extent.For the normal state,the distribution network adjusts the topology of the distribution network by changing the gap and shutting state of the tie and section switches to transfer the power flow distribution,and finally advance the reliability and economy of distribution network operation.Dissertation specific contents are as follows:Firstly,aiming at the distribution network fault recovery,a service restoration strategy for a distribution network based on heuristic rules and the AHP-CRITIC algorithm is proposed.In the first step,all distributed generations(DG)with black-start capability in the blackout area are traversed by a breadth-first search method to form islands and restore power supply.In the second step,by use of heuristic rules in the residual power-loss area,a candidate service restoration scheme set is generated.In the end,for service restoration,five evaluation indices such as the proportion of load restoration,switching times of circuit breakers,voltage drop,the margin of load capacity and the quantities of transferred load are introduced,and the AHP-CRITIC algorithm is employed to determine the optimal fault recovery scheme for restoring the power supply in the residual power-loss area.The simulation verifies that the distribution network service restoration strategy is effective.Secondly,aiming at the optimum operation of distribution network,a reconfiguration model with DG is established,which takes system loss,load balance and voltage deviation as objective functions,the weights of three objective functions are determined by random weight distribution to ensure the diversity of objective solutions.An adaptive multi-population fruit fly optimization algorithm(AMFOA)is proposed to perfect smell search and visual search.An adaptive step size adjustment strategy is introduced to enhance the local search ability of basic fruit fly optimization algorithm(FOA),which can achieve the effect of balancing global and local search.Multi-population strategy and Chebyshev chaotic mapping can promote the global searching ability and accelerate the searching speed of the algorithm.The simulation results verify accuracy and feasibility of the distribution network reconfiguration strategy based on AMFOA.Finally,aiming at the multi-objective optimization of distribution network,although transforming multi-objective into single objective for optimal reconfiguration of distribution network has the benefits of straightforward operation and little quantity of calculation,however,the size of weight factor is easily affected by subjective factors,and the constraint relationship between the objectives is not considered,therefore,the reliability of the optimal solution needs to be promoted.In order to improve the practicability and reliability of intelligent algorithm in distribution network reconfiguration,combined with the concept of Pareto multi-objective optimization,a multi-objective fruit fly optimization algorithm based on population Manhattan distance(pmd MOFOA)is applied,which is combined with static reconfiguration of distribution network to advance the efficiency and quality of reconfiguration.Based on the mathematical model of distribution network reconfiguration in chapter 4,the multi-objective fruit fly optimization algorithm based on population Manhattan distance is adopted to obtain the candidate scheme set of distribution network reconfiguration,and the optimal reconfiguration scheme is decided by AHP-CRITIC method.The simulation results show that the proposed multi-objective reconfiguration strategy based on pmd MOFOA is effective in reducing network loss,maintaining load balance and improving voltage quality.