Frequency Regulation Control Strategy for Flywheel Energy Storage Coupled With Thermal Power Units Under Multiple Operation Stages

ObjectivesFlywheel energy storage that assists thermal power units to participate in frequency regulation is widely used in the field of grid frequency regulation. In view of the fact that the current commonly used energy storage control strategies fail to fully consider the operating requirements of frequency in different stages of change, an adaptive frequency modulation control strategy for flywheel energy storage-thermal power units is proposed that considers the effects of positive and negative inertia.MethodsConsidering the effects of positive and negative inertia control on frequency recovery at different stages of frequency variation, this study proposes an adaptive frequency control method for a thermal power-energy storage coupled system under dynamic operating conditions. This method fully integrates the advantages of inertia control and droop control, and adaptively adjusts the control strategy according to the system frequency deviation and the real-time state of charge (SOC) of energy storage.ResultsUnder step disturbance, the proposed strategy reduces the maximum dynamic frequency deviation by 2.8%, the steady-state deviation by 2.9%, and the settling time by 17 s, while the change curve of SOC becomes smooth. Under continuous disturbance, the proposed strategy can reduce the frequency deviation by 8.1% and reduce the output of thermal power units by 52.8%. The SOC of the energy storage system can be maintained within a good range throughout the command period.ConclusionsThe proposed strategy can improve the frequency regulation performance of the system, reduce unit output fluctuations, and take into account the state of charge management of the energy storage system.