By adjusting the output of the energy storage battery according to the fixed sagging coefficient, the power can be quickly adjusted and has a better frequency modulation effect. Based on the adaptive droop coefficient and SOC balance, a primary frequency modulation control strategy for energy storage has been recommended [ 14 ].
The dynamic frequency modulation model of the whole regional power grid is composed of thermal power units, energy storage systems, nonlinear frequency difference signal decomposition, fire-storage cooperative fuzzy control power distribution, energy storage system output control and other components. Fig. 1.
Based on the above analysis, a control strategy based on cooperative frequency modulation of thermal power units and an energy storage output control system is proposed to improve the frequency stability of the power grid.
Under the four control strategies of A, B, C and D, the hybrid energy storage participating in the primary frequency modulation of the unit |Δ fm | is 0.00194 p.u.Hz, excluding the energy storage system when the frequency modulation |Δ fm | is 0.00316 p.u.Hz, compared to a decrease of 37.61 %.
Huang Yihan et al. established the distributed parameter dynamic model of the drum boiler of a thermal power unit, and the relative errors of the frequency modulation power were effectively reduced to 2.16 % from 38.74 %. Second, the thermal power unit coupled energy storage to participate in the primary frequency modulation.
The frequency modulation of thermal power unit has disadvantages such as long response time and slow climbing speed. Battery energy storage has gradually become a research hotspot in power system frequency modulation due to its quick response and flexible regulation.