Power coordination of grid-connected wind turbine doubly fed induction generator augmented with battery storage

Wind power tends to be unsteady because it is influenced by natural and meteorological conditions, so, there is a need of energy storage system that takes care of this wind power variation. The integration of a battery energy storage system (BESS) with a wind turbine doubly fed induction generator (DFIG) can make these intermittent in wind power more dispatchable. This paper focuses on the development of a control strategy for optimal use of the BESS for this purpose. A rule-based control scheme is considered as a solution of this optimal control problem defined, to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge current limits, and lifetime. The goal of the control is to have the BESS provides power as much smoothing as possible so that the output power of the DFIG can be maximized at all wind speed independent of the estimated grid power required. Two objectives are targeted in the paper. The first objective is to obtain the maximum output power out of the existing wind regime. This is achieved by controlling the voltage injected to the rotor terminals. The second objective is to supply the demand power commitment to the grid. This is achieved by controlling the battery power flow. The size of the battery is calculated to accommodate excess power and to compensate for the deficit power according to the wind regime and the grid power demand.