Participation of DFIG wind turbines in frequency control ancillary service by optimized rotational kinetic energy

The increase in renewable and distributed energy resources has given rise to new concerns about frequency stability of electric power systems, as renewable generation is considered an intermittent source, which by its nature does not participate in frequency control. In some countries, system operators demand wind turbines to provide some sort of ancillary services, such as reactive power control and frequency/active power control in order to increase system stability. This paper focuses on the provision of primary frequency control by wind generators and proposes a novel control strategy for active power reserve provision of doubly fed induction generator wind turbines. The proposed control strategy aims at maximizing the rotational kinetic energy, using the differential evolution. The control variables in the optimization process are the rotor speed and the pitch angle, considering the given power reserve factor. The proposed control strategy is compared to the strategies proposed by other authors. The results show that, compared to the existing methods at the same de-loaded power, the proposed method yields more rotational kinetic energy, that is released into the system in case of frequency deviations, thus increasing frequency stability of a power system.