By taking the hybrid energy storage system(ESS)composed of the value regulated lead acid(VRLA)battery and the vanadium redox battery(VRB)as an example

in view of the intrinsic characteristics of conventional unit frequency regulation

a charge and discharge strategy and optimal capacity planning of hybrid ESS participating in the automatic generation control(AGC)by assisting conventional units is studied. Firstly

according to the characteristics of conventional unit frequency regulation

an optimal control strategy taking into account the suppression of reverse frequency regulation

dead zone oscillation

ESS over discharge

and forced state of charge(SOC)homing is proposed. Secondly

considering the cost of ESS configuration and the frequency regulation income of power generating units

a capacity planning model is developed. Finally

based on the particle swarm optimization(PSO)algorithm

the simulating calculation of the actual operation data of a power station is conducted. The results show that the frequency regulation performance and the running cost of the method are both better than those of the conventional unit frequency regulation.This work is supported by National Natural Science Foundation of China(No. 51307101)

Science and Technology Foundation for Middle-age and Young Scientist of Shandong Province(No. BS2013NJ011).