Control strategy for a hybrid energy storage system to mitigate wind power fluctuations

With the intermittency and uncertainty of wind power, two-time-scale maximal power fluctuation restrictions (MPFRs) are set by electrical company for the combined power of the wind farm and the hybrid energy storage system (HESS): the maximal fluctuation of the combined power in any 1- and 30-min time window must be kept within γ_1min% and γ_30-min% of the wind farm rated power, respectively. Under this circumstance, an approach of improved first-order low-pass filter (IFLF) is proposed, which could adjust the time constant in any second if necessary when the fluctuation during the latest two seconds is exceeding a certain valve. Then a strategy to manage the power sharing between the battery and the super-capacitor at every second is described, which is based on Particle Swarm Optimization (PSO) algorithm and consider the constraints for the state of charge (SOC) of battery and the change times between battery charging and discharging. Simulation results demonstrate that the proposed control strategy is effective both in mitigating the wind power fluctuation to satisfy the MPFRs with lower HESS capacity and prolonging the lifetime of battery.