Research On Optimal Sizing And Optimal Energy Management For Microgrid

Power electronics, distributed generation(DG) and energy storage technologies based Microgrid(MG) can integrate the advantages of DG units, facilitate renewable energy accessing to power system, and coordinate distributed power and the power system. Therefore, it becomes a useful complement of power system. At present, MG is regarded as an important part for the development of smart power grids worldwide. Optimal sizing for MG is an important aspect at the planning and design stage of MG, which is greatly significant for improving MG reliability and operating economy. Optimal energy management for MG is the important guarantee to achieve safe, reliable, economical and efficient operation.In this paper, optimal sizing and optimal energy management for MG are studied. The main work is presented as follow:(1) Aiming at independent power supply wind/photovoltaic/storage MG, the optimal sizing model is established, and particle swarm optimization (PSO) algorithm based solving method is proposed. In the study case, battery group and electrolyzer-hydrogen tank-fuel cell circulatory system are put as storage unit respectively, for analyzing the optimal sizing of MG. Case results show that the MG with battery storage is more economical, and that reasonable assessment of the outage cost and reliability index set is an effective means of reducing MG power redundant investment.(2) Real-time optimal energy management for grid-connected MG is proposed. It previously divides the 24 hours in a day into peak time, normal time and valley time. In real-time dispatch, different dispatching strategies are used according to current time and the state of charge(SOC) of battery storage. Case study results indicate the proposed method can not only realize economical operation, but also help outer grid with "Peak clipping and valley filling".(3) Mult-time scale coordinated optimal energy management for standalone MG is proposed, including day-ahead scheduling and real-time dispatch. In the day-ahead scheduling, optimal on/off states of controllable micro-sources in each time interval of whole day are arranged through the day-ahead model. In the real-time dispatch, the result of day-ahead scheduling is adopted, and two kinds of real-time energy management are proposed respectively for MG with storage device and MG without storage device. In the real-time energy management, the state of energy(SOE) of storage device is divided into four operating levels (for MG with storage device), and different strategies are used according to the current SOE level of storage device and the net load power. Load bidding strategy is used, while load shedding and excess-power dissipating are considered in MG operation. Case study results indicate that the proposed mult-time scale coordinated optimal energy management for standalone MG can not only ensure the MG reliable, economical and long-term operation, but also reduce the configuration capacity requirements of storage device in a MG.