Research On Microgrid Optimal Energy Management

Energy is the key support of the national economy. In the recent years, with the steady and rapid development of China's economy, energy production and consumption have been increasing rapidly. However, the unreasonable energy structure and low energy utilization efficiency have brought many environmental and social impacts. By promoting the utilization of clean and renewable energy, distributed generation (DG) can increase energy utilization efficiency, improve energy supply structure and ensure energy supply security. In addition, power system has been developed into a large-scale interconnected systems with centralized large capacity of power generations and ultra/extra-high voltage long distance transmission system. Under this condition of large-scale interconnection, failure will propagate throughout the system, even lead to blackout if it is not treated properly. Since the electricity supply of most areas in China is overly dependent on centralized power generation, the ice-snow disaster of 2008 in South China has led to power system blackout.DG is a significant supplement to traditional centralized generation, which can delivery economic, efficient and reliable electricity supply. Microgrid, an entity of various distributed energy resources (DER) with different characteristics and mutual complementation, can operate in phase with macrogrid, and improve energy utilization efficiency and electricity supply reliability. This thesis focuses on microgrid energy management, and is organized as follows.Firstly, the development background of DER is introduced. In detail, the development status of DG is summarized, and the superiorities of microgrid for DG integration are concluded. Then the research status of microgrid energy management and the impact of electric vehicle charging are reviewed.In the second chapter, the schematic diagram of typical microgrid and its optimal operation are introduced at first. To achieve the optimal operation of microgrid, optimal heat and electricity coordinated dispatch model within microgrid is proposed, in which the constraints of equipment operation capacity, system physical operation and power loss are considered. Then Particle Swarm Optimization (PSO) is introduced, and IPSO is employed to this model. The impacts of different demand profiles and different energy prices on the optimal operation of microgrid are investigated, and the matching problem of heat to power ratio (HPR) between demand and combined heat and power (CHP) is analyzed.Chapterâ…¢takes the startup and shutdown constraints of CHPs into the model proposed in chapterâ…¡. Then mixed integer programming (MIP) and PSO are applied to this model. Through the case study, the performance of mixed integer nonlinear programming (MINLP) is compared with that of IPSO when the power flow constraints within microgrid are considered; while the performance comparison between the mixed integer linear planning (MILP) and IPSO is explored when the power flow constraints are ignored.In the fourth chapter, Latin Hypercube Sampling (LHS) and scenario reduction technology are utilized to describe the stochastic nature of wind power. Then a day-ahead microgrid optimal dispatch model considering stochastic wind power is proposed, in which minimizing the impact of power exchange fluctuation at PCC is taken into account. In this model, wind power fluctuation is accommodated within microgrid. As a result, microgrid is a schedulable entity to macrogrid, while the optimal operation of microgrid is achieved.Chapterâ…¤proposes a real-time operational dispatch model of microgrid. Integrating the day-ahead optimal dispatch model with the real-time operational dispatch model, a multi-time scale microgrid energy management architecture is developed. According to the coordination of heat and electricity, day-ahead optimal dispatch model provides flexibility to real-time operational dispatch and improves the ability of microgrid to accommodate wind power fluctuation. During the real-time operation, if the real wind power output is different from the day-ahead forecasted value, the schedulability of microgrid is realized by the adjustment of day-ahead dispatch and assist of electric energy storage, while the availability of day-ahead dispatch is ensured and the impact of wind power fluctuation is minimized. The sixth chapter introduces the application background of electric vehicle (EV) and analyses the EV charging demand model. Then the impact of EV charging on distribution network (DN) is studied under conditions of different season, different charging mode and different EV penetration. The impact of EV charging on DN is also invistegated with large amount of wind power integrated.Chapterâ…¦summarizes the main findings of this paper, and points out the future research directions.