Читать книгу Smart Grids and Micro-Grids - Umashankar Subramaniam - Страница 32

Intermittency and fluctuation of renewable energy sources coupled with increased penetration pose a challenging problem for microgrid (MG) from the perspective of maintaining grid stability and delivering reliable power. Distributed energy storage (DES) is the best option to mitigate the uncertain power generation challenge posed by renewable energy while maintaining grid reliability with reduced microgrid operational cost. The excess renewable generation is stored by DES and is used when it is useful from either a technical perspective (e.g., voltage and frequency regulation) or an economic perspective (e.g., energy arbitrage). From the perspective of improving power quality and frequency regulation, energy storage systems (ESS) having high power density and fast response is required. For load levelling as well as peak shaving requirements in the microgrid, ESS (Energy Storage Systems) having high energy density and long discharge time is required. This chapter intends to explore the need and application of ESSs to deliver the electric power to costumers that meet the reliability and quality standard. Characteristics of different ESS technologies and their relative pros and cons are discussed, which is the key to select ESSs for a particular application in a microgrid. An overview of interfacing circuit for integrating ESS to microgrids such as DC-DC converter and DC-AC converter is also discussed. The development of simulation model of a popular bidirectional DC-DC converter which is used for controlling the charging and discharging of the ESS to microgrid is discussed as an example of application of ESS in microgrid. To control real and reactive power flow to the grid, modelling and control of voltage source inverter (VSI) based grid tried converter that interfaces ESS and grid is provided. Discussion on simulation results of the developed model in MATLAB-Simulink is provided to show the ability of VSI system for charging the battery or providing power for microgrid as per the requirement mandated by higher level controller of the microgrid.