Optimal sizing for flywheel energy storage system-conventional generator coordination in load frequency control

Conventional generators(CG) are limited in their ability to provide load frequency control because of restriction on power ramp rate and response time while flywheel energy storage systems (FESS) are well suited to assist LFC owing to their fast and accurate power tracking ability. In this paper, fixed power control (PQ control) is applied in the auxiliary service of FESS in LFC and probability statistics methods are used for demand analysis. Taking into account the regulation service of FESS and CG, the initial cost, and the operation and maintenance cost, an optimal sizing model for the FESS-CG coordination based on a control strategy developed to maintain the State of Charge (SOC) of FESS within a desired range and reduce the output adjustments of CG is established. With the optimal objects of technical and economic benefits, the non-dominated sorting genetic algorithm-II (NSGA-II) is adopted to seek the optimal sizing scheme for the capacities of FESS and CG and the parameters of the control strategy. The simulation results reveal that the method is capable of making comprehensive assessment of the technical and economic benefits of different schemes.