Optimal Capacity Configuration Of Energy Storage System For Frequency Regulation In High Wind Penetration Power System

The inertia of a variable speed wind turbine is decoupled by power electronic converters from the power network and therefore does not intrinsically contribute to power system inertia.With the increasing wind penetration level in power systems, transmission system operators have become concerned about frequency stability. As a result, it is of great significance to equip the wind turbine with the ability of frequency response. As fast response and high energy density are advantages of lithium battery, it is possible for wind turbine to provide frequency assistance to power system with the coordination of lithium battery energy storage system(ESS). To improve the economic benefit of participation of wind farms in frequency regulation, it is one of the important research focuses to study the coordination between wind farm and ESS for power system frequency assistance.In this paper, the primary frequency response of power system and necessary primary reserve provided by wind farms are studied by simulation base on a typical power system frequency response model. Two control strategies of primary reserve of wind farm, proportional curtailment strategy and constant curtailment strategy, are introduced. The efficiency indicator of curtailed wind power for aggregated and distributed control by proportional curtailment strategy are compared. At the same time, the variability of efficiency indicator of curtailed wind power is studied for different proportional curtailed coefficient. A proper energy storage medium for primary frequency regulation is chose by comparing technology and economic properties of different energy storage medium. Different control strategies of ESS are proposed based on different methods for selecting valid reserve. The economic benefits of different control strategies are compared while providing the same primary reserve. The structure of wind-storage network integrated system and mathematical model of ESS are presented. Design and implementation of a 10kW/20 kWh lithium battery ESS is introduced. The competence of lithium battery ESS for providing primary reserve is verified by experiment. Work in this paper provides a reference for the study of improving the economic benefit of primary reserve offering wind farm and it has certain engineering value.