Combined active and reactive power control strategy to improve power system frequency stability with DFIGs

The increasing penetration of wind farms in the electricity grid will have a larger impact of grid operations. This requires wind farms to have the ability to assist in some of the power system control services. Frequency is one of the most important services. Doubly fed induction generator (DFIG), as a widely used machine in modern wind industries; however, its rotor speed is decoupled from the frequency in the power system and thus DFIG cannot response effectively when there's a frequency fluctuation. This paper proposes a combined active and reactive power control strategy to let DFIGs support primary frequency control. This strategy consists of two parts: One is active power control part based on virtual inertial control, the other is reactive power control part based on the theory that active power of the load is sensitive to the bus voltage magnitude. The effectiveness of the proposed strategy is verified by simulation analysis using MATLAB/SIMULINK and the results prove that it can improve the frequency stability of power systems with wind farms. Meanwhile, compare with the strategy only have one of the two control parts, the proposed strategy can further optimise the capability of DFIGs to participate in frequency regulation.