Research On Vulnerability And Optimal Control With Distributed Generations Of Micro-grid

Nowadays,with the popularity of the large power grid,small distributed generation has an important role in the application of large power grid,and the power generation system based on distributed power generation is the trend of development.Meanwhile,the micro-grid consisted by small capacity distributed power develop rapidly.This trend makes the connection between the internal power system increasingly complex,which makes the power grid operation more complex,thus increasing the probability of the power grid failure.The vulnerability is a unique property of the grid itself,so the evaluation of the micro grid’s vulnerability is of great significance.This dissertation is supported by “micro-grid safety assessment and its multi-objective optimal control method research based on the vulnerability indexes”,subsidized by the National Foundation of China,No.51567019,evaluating the vulnerability of micro-grid.Firstly,in this paper,the brittle source of system and the definition of vulnerability are analyzed.Based on the existing vulnerability index,we put forward two evaluation index:the structural vulnerability index considering node degree and line reactance value;the operational vulnerability assessment index considering node voltage quality and power balance of the line,thus establishing the comprehensive evaluation index system by the importance of the index Different types of distribute power supply and the current calculation model of distributed power supply are introduced.We analyze the current calculation of grid system by these models,and then calculate the vulnerability index value based on the distributed power supply.Calculating the grid vulnerability of the IEEE33 power system.Simulating system’s grid vulnerability under the same type,different types and different sets.Comparing the index value under different calculation examples,we get the system vulnerability of different types of DG and different points,and evaluate the impact of distributed power on the vulnerability of the system.The simulation results show that the index is reasonable,and the system vulnerability can effectively reduce the system vulnerability and improve the security performance of the system when insert distributed generators.Secondly,based on the formed comprehensive vulnerability evaluation index,construct the reconstruction model up to the objective function,which is list with network active loss and comprehensive vulnerability,and use the global optimization of the quantum particle swarm algorithm to solve the optimal solution.The simulation results show that the proposed index is effective,the network reconfiguration can not only reduce the network loss effectively,but also reduce the system vulnerability and improve the security performance of the system.Finally,in the weighted topological model of the grid,the power value of line reactance is taken as the power value.Through estimating optimal results of network fault vulnerability,meanwhile,analyzing the changes of power grid vulnerability under failure mode to reduce the impact of failure and the occurrence of faults.We define two indices: the network structure entropy’s decrease percentage,which is over consideration of node and side difference;the transmission efficiency’s decrease percentage,which is over consideration path length.Through calculating the index change values under different fault modes,we get the vulnerability of the power grid.The results of the IEEE9 node system show that the proposed index is effective and correct.Furthermore,the results prove the importance of key nodes in the Power Grid,and arrange the network structure reasonably can improve the security and stability of the system effectively.