Research On Multi-objective Optimal Operation For AC/DC Hybrid Microgrid

With the growth of DC distributed resources and DC load,people begin to think about building DC power grid.Based on the traditional microgrid,the AC/DC hybrid microgrid emerged as the times require.Not only hybrid microgrid can effectively reduce the number of converters in the electrical equipment,but also decrease the uncontrollability and instability of distributed resources.Therefore,the research on the AC/DC hybrid microgrid has theoretical and practical value.This article focuses on the multi-objective optimization and operation of microgrid which contains a variety of micro sources.The main works are as follows:(1)Firstly,the structure of microgrid that can reduce the loss of inverter is analyzed.Secondly,the power generation principles and the mathematical models of wind turbine,photovoltaic generation and combined cooling,heat and power system are explored.Considering the storage battery has the characteristics of short life and high cost,the discharge depth of battery is counted by the rain flow counting method,and then the life loss of battery is calculated.Taking into account the popularity of electric vehicles(EVs),a random charging model is also established,which simulates the starting time,the ending time and the mileage of charging,and then gets the charging load of EVs.Finally,the application of transferable load in the demand-side response is described.(2)For the modeling and solving of multi-objective optimization problems.Firstly,the objective functions and constraints under isolated mode and grid-connected mode are put forward,then a corresponding time-sharing scheduling strategy is formulated.Secondly,we analyze the principle of genetic algorithm,and then two improved genetic algorithms are compared.Finally,we use standard test function to verify the effectiveness of improved nondominated sorting genetic algorithm(NSGA-II)in solving multi-objective optimization problems.(3)Considering the time sharing price and the proposed scheduling strategy,NSGA-II algorithm is applied to solve the model of microgrid.According to the simulation results,the output power of each micro source,the power exchange with large power gird,the cost of consumption,operation,purchase and sale are calculated under different conditions.The cost survey shows that the comprehensive benefit of the microgrid is related to its operation mode.Compared with the single-objective optimization,multi-objective optimization give consideration to both economic performance and operational constraints.When the transferable load is involved in the schedule,the economical efficiency of microgrid and user can be further improved.