Research On Reliability Evaluation Of Microgrid Cluster Considering Optimal Dispatching

Along with the growth of the world's population, increased consumption of energy, serious environmental problems and exhaustibility of fossil fuels, the development and utilization of renewable energy attracts much more attention. Micorgrid, as an effective way of integrating and utilizing all sorts of distributed generation, is able to solve the problem of integrating massive DGs into main Grid, thus improving power quality and guaranteeing reliability of power supply. To deal with the constraints on the massive development and integration of Microgrid from the structure of distribution network, and to enhance the interactive mechanism among Microgrids, Microgrid cluster is proposed as an effective mode of clustering multi-Microgrids. How to evaluate the reliability of Microgrid cluster in a more accurate and comprehensive way has become the focus of this thesis.Firstly, the thesis analyzed the basic concept, topology and operation mode of Microgrid cluster. Based on the analysis of the influence of component failure rate on the reliability of Microgrid cluster, and taking into consideration the effects of component aging, periodic maintenance and climatic conditions on component failure rate, a component time-varying failure rate model was proposed. And on which basis, aiming at the problem that conventional Monte-Carlo simulation method cannot consider the time-varying characteristics of component failure rate, a hierarchical dynamic Monte-Carlo simulation method was adopted to build the reliability evaluation model, and to further evaluate the reliability of Microgrid cluster. Taking a demonstration project in Guangxi as an example, simulation has been made, and the results has been compared and analyzed to figure out the effects of time-varying characteristics of component failure rate on the evaluation results of Microgrid cluster.Then, taking into account the total cost of investment and operation for Microgrid cluster based on total life cycle, a coordination optimization model for Microgrid cluster considering reliability and economy was proposed, and PSO algorithm was adopted to solve the model. Specifically, the minimum outage cost caused by EDNS was taken as the target for optimal reliability, and the minimum cost for investment and operation was chosen as the target for optimal economy, a global optimal solution that compromises both reliability and economy was achieved through constant iteration. Particularly, during the optimal dispatching process, if the adequacy of the Microgrid cluster was insufficient, shedding loads would be a necessity. Under which circumstance, the power supply reliability of critical loads should be given priority to, a load shedding strategy considering load importance and location has been proposed.Finally, by embedding time-varying component failure rate model, load shedding strategy and optimization model into the reliability model, a reliability evaluation method considering optimal dispatching was proposed, the reliability indexes were calculated, and the influence of operation state of Microgrid cluster after optimal dispatching on system reliability was analyzed.