Study On Optimal Configuration Of Grid-connected Microgrid

The microgrid system with distributed power supply and energy storage device can not only utilize renewable energy efficiently,but also reduce the cost of transmission and distribution,which have received widespread attention.The optimal allocation of DG in micro-grid power is a primary problem to be considered in the planning stage of micro-grid.But at present,in the research of energy storage capacity optimization in the micro network system,the majority concentrated in the search for optimal total capacity,with little regard for alloca ting the size of battery to improve the efficiency of battery energy storage system.Reasonable power allocation and battery match scheme can effectively reduce operating costs,reduce environmental pollution and improve reliability.Firstly,learning from the planning evaluation method of grid,combined with the characteristics of micro-grid power planning,the paper establishes the evaluation index system of micro-grid power planning,including reliability,economic and environmental indicators.According to the characteristics of resources and importance of load,the application of micro-grid is divided into two kinds of scenarios.One is the scenario of priority to micro source and the other one is the scenario of priority to utilization efficiency of battery.Based on the optimization objectives,constraints and scheduling strategies,the optimization allocation principles of micro-grid under two scenarios are presented.Combining with the characteristics of micro-grid power optimization allocation model,the basic genetic algorithm is improved.Validated by test function,with the selecting operation based on the roulette and the best individual preservation,dynamic crossover and dynamic mutation operator,the improved genetic algorithm is beneficial to improve the problem that traditional genetic algorithm is easy to fall into local convergence,as well as search speed and accuracy of the algorithm.For the scenario of give priority to micro source,bi-level programming model considering economy and environmental protection is established.The reliability index is calculated by Monte Carlo simulation.The model is solved by using the improved genetic algorithm.The sensitivity analysis of the optimal allocation results is carried out in the aspects of resource status,unit cost,pollutant discharge and so on.Constructed the micro-grid system which considering the utilization efficiency of battery.A parameter-average utilization efficiency of battery is introduced as the index of running cost.Adding the switching controller to the battery energy storage system to control the number and time of the battery.The static allocation model of battery capacity in the micro-grid system considering the utilization efficiency of battery is established.Objective function is minimizing the total cost of the micro-grid system including fixed cost and operation cost.The constraint conditions include battery SOC limit,battery charging and discharging power constraint,energy conservation constraint,grid connected power fluctuation and so on.A bilevel optimization algorithm for solving the static capacity allocation model is given,And a dynamic allocation method based on state of charge is proposed.