| Microgrid is an important way of energy supply in the future by coordinating and complementing a variety of distributed generations,which could greatly meet users' demand of electricity as well as saving investment cost.The optimal sizing of microgrid is the primary problem in the planning stage,and it relates to the performance in system operation.Wind and solar are the most widely used renewable energy.A hybrid microgrid including wind turbine,photovoltaic panels and energy storage system is a typical multi-energy complementary application.According to the characteristics of each unit,the optimal sizing of that hybrid microgrid is a multi-objective optimization problem based on the overall performance,such as pursuing the economy,environmental protection and system reliability.In order to solve this problem,a sizing coordinated optimization methodology for the hybrid microgrid system including wind turbine,photovoltaic panels and energy storage system is proposed in this paper.Firstly,the output model of the system is constructed,and the output characteristics of each component is analyzed.Then,according to the output characteristics of each unit and its role in the microgrid,the power allocation strategy is presented,which is the foundation for the simulation of the sizing plan.The multi-objective sizing coordinated optimization process of microgrid is determined,including equipment selection,operation strategy formulation,capacity optimization and plan selection.Among them,the capacity optimization is the core part of coordination optimization.Aiming at this multi-objective optimization problem,the grid-connected and off-grid multi-objective sizing optimization model are constructed.The life cycle economy,system environmental performance,system reliability and independence of the system are set respectively.The optimization objectives of reliability and renewable energy utilization level are to set constraints on power balance,equipment capacity,occupied area and system operation.The model is solved by NSGA-II method,which adds fast non-dominated sorting,introduces elite strategy and adopt improved non-inferior sorting genetic algorithm with congestion degree operator,it could reduce the complexity of the algorithm,as well as improve the accuracy of population at the time of obtaining Pareto front solution of multi-objective optimization problem.Aiming at the multiple plan decision making problem introduced by Pareto front solution,Topsis method is used to rank the solution according to the preference of decision maker,and the final sizing plan of the hybrid microgrid is determined.At last,a grid-connected microgrid demonstration project is selected for case study to verify the effectiveness of the proposed methodology.The historical data of wind speed,radiation intensity,temperature and power load are analyzed.The simulation time interval is set as one hour.And the multi-objective capacity optimization model is introduced to optimize the sizing of microgrid in terms of economy,carbon emission and system independence in the lifetime.The final sizing plan is selected by Topsis method.A typical day is selected to simulate the output state of each unit in the system,which proves the reliability of the methodology in solving the multi-objective sizing optimization problem of hybrid microgird in this paper. |
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