Abstract: The converter interfaced power sources has the advantages of flexible and fast response, the energy stored in its rotating masses can be released to realize fast system frequency support. Most of the existing control strategies pay less attention to quantitative analysis of how control strategies affect the frequency nadir, and fail to effectively enhance the frequency nadir under any conditions. Aiming at improving the system frequency nadir, a frequency support strategy based on step power control is proposed. Firstly, the system frequency response under step power control is analyzed, and the analytical expressions of the two frequency nadirs following the disturbance are derived further. Then, the optimal reference of power step control is determined by combining the kinetic energy that can be released by each wind turbine generators and a coordinated distribution of the additional power is realized based on the expressions. Finally, a test system is built on MATLAB/Simulink. The effectiveness of the proposed strategy is verified by numerical simulation results.

Key words: system frequency response, permanent magnet synchronous generator, primary frequency regulation, step power control