Research On Energy Management And Optimal Design Of Microgrid

A microgrid (MG) is a cluster of interconnected distributed generators, loads and intermediatestorage units，which cooperate with each other to be collectively treated by the grid as acontrollable load or generator. It can be operated under grid-connected mode or islanded mode. Asa new energy supply and network management technology, microgrid could allow renewable andclean resources to be integrated into a utility. At the same time, it could achieve demand-sidemanagement and economical operation. This paper focuses on the issues related to the energymanagement, optimal design and demand response of microgrid.First of all, classification of microgrid scale and topology, state of art of energy managementand optimal design method are presented in this thesis.Secondly, the quasi-steady state models of wind turbine, solar array, diesel, combined coolingheat and power (CCHP), battery, power electronics and demand-side load are presented. Themodels are the important modeling foundmental used in following chapters which addresses onenergy management and optimal design.Thirdly, considering of the operating constraints of primary equipments, a coordinated controlstrategy of typical isolated Microgrid including desalination load is proposed in this thesis. Theprimary design objectives are to ensure the long-term stable operation and to reduce the costsincurs over the system lifetime. A typical practical isolated Microgrid is studied via aself-developed quasi steady-state simulation tool. The simulation results show the effectivenessand correctness of proposed control strategy.Fourthly, this thesis proposes a reasonable integrated Energy Management System (EMS) forCCHP. Four kinds of operation modes listed as:(1) Determining cooling load by electricityconsumption,(2) Determining Electric Load by Cooling Consumption,(3) Optimal Cost and (4)Optimal Prime Energy Ratio (PER) are integrated in this EMS. Integrated factors such as thecooling and electric load, the generation possibility to grid, electricity price of micro-turbine(MT)for sale and the price of natural gas and electricity are considered into these four modes and thecooling capacity of Lithium Bromide Double-effect Absorption Refrigerator (LBDEAR) and MTpower are adjusted in real time conditions.Then, considering with the fluctuations caused by renewable energy integrated into MG, thisthesis presents a novel demand response algorithm for MG tie-line power flow smoothing. Theresidential heat pump is treated as one kind of demand-side responsive resources. This smoothingalgorithm controls the switching status of heat pumps based on a state-queueing (SQ) controlstrategy. The demand response is used to replace conventional storage device to provide powersmoothing service. Finally, this thesis presents a multi-objective optimal design method for an island Microgridwith desalination plant. The allocation ratio of net present cost (NPC) in the full life cycle, theutilization of renewable energy and pollutant emission level is the primary optimization problemin this model. The optimal number of distributed generators and the optimal capacity of energystorage are determined to satisfy the proposed multi-objective model.