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Optimal Dispatch Strategy Of Microgrid In Grid-connected Mode And Its Application

Posted on:2018-06-25Degree:MasterType:Thesis
Country:ChinaCandidate:H T ZhangFull Text:PDF
GTID:2322330536465858Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
In recent years,new energy power generation develop rapidly.The optimal dispatch strategy of microgrid has been established to realize the economic operation of microgrid and the optimal power allocation of the controllable units in the microgrid.However,the output power of new energy power generation with wind and illumination is with volatility.And the load forecasted result based on history data exists error.The uncertain factors above would lead to the lack of reservation and the reduction of economy of the microgrid optimal dispatch strategy with single time scale.A more comprehensive optimal method is needed to be established for the optimal operation of microgrid.This paper first introduces the characters,structures in grid connected mode,operation principle and operation characteristics of photovoltaic,lithium battery,super capacitor and fuel cell.And the processing methods of each distributed unit in microgrid are summarized.A battery operating cost function is derived.Mathematical models for the operation and maintenance costs of lithium batteries and fuel cells have been established.For the microgrid with master-slave structure,the control principle and control method of host distributed unit working in grid connected mode and island mode is studied separately.And the corresponding Simulink model is set up.That the study of the characteristics and control method of distributed units paves the way for the optimal operation of microgrid below.Then the basic mathematical model of two-layer optimization and the application of two-layer optimization ideology in microgrid are studied.The comprehensive load model based on load vector is established.The robust penalty cost is introduced.The maximum fluctuations error between prediction value and actual value is considered,and a two-layer optimization dispatch model based on robustness is established.The model is calculated by programing in LINGO.Then the simulation result is analyzed.And the influence of prediction error factor and demand side response model on simulation result is analyzed.Then treat AC microgrid as the research object,and a universal multi-time scale optimization scheduling scheme of microgrid energy management within two stages that are day-ahead stage and intraday stage is proposed.Lithium battery and super capacitor are dispatched in different time scale.In day-ahead scheduling stage,a battery operating cost function is derived.According to dayahead prediction of PV and load,total operation cost of microgrid is set as objective function to optimize power dispatch.Electricity price at different periods and PV in two working modes are considered.In intraday stage,according to power fluctuations,different kinds of generating units are dispatched based on economy.Additional cost at dispatching process is considered in calculating total operating cost to obtain more accurate result.It would be convenient for the contrast of several multi-time scale optimization scheduling schemes.The characteristics and modeling methods for optimization problems of LINGO software are introduced.Then a case is calculated,and the simulation results verify the rationality of the dispatch strategy.According to the established models in Part 2 and Part 3,several optimal dispatch strategies for microgrid that consider uncertainty are compared and analyzed.Based on actual experimental environment,the dispatch strategy proposed in Part 3 is improved in both dayahead stage and intraday stage then.Finally,basic equipment in microgrid lab are introduced.The physical structure and communication architecture of the microgrid lab are studied.And the structure and function of the corresponding microgrid energy management system software platform for the microgrid lab are studied.At last,Based on the improved scheme proposed in Part 3,the program is edited in Qt Creator platform.And the control strategy of microgrid energy management system is fulfilled.Then optimal dispatch operation experiments of microgrid lab based on typical scenes are realized.And the experimental results in different scenes are analyzed.The analysis for the experimental results verify the rationality of the dispatch strategy.
Keywords/Search Tags:microgrid, operation cost of lithium battery, multi-time scale, dispatch strategy, two-layer optimization, energy management
PDF Full Text Request
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