In order to improve the ability of battery energy storage system(BESS)to smooth photovoltaic(PV)power fluctuation

a slope control method with variable coefficients based on ultra-short term power prediction is proposed. On the basis of the slope control method

two parameters for controlling the partition of state of charge(SOC)and four charge and discharge power regulation parameters are proposed. Then a smoothing strategy containing the above six variable coefficients and able to regulate SOC automatically is developed. The objective function is developed based on the ultra-short term PV power prediction. And a self-adaptive chaos particle swarm optimization algorithm is used to optimize the coefficients in real time

realizing the coordinated optimization between the smoothing performance and SOC. Compared with the method with fixed coefficients

the simulation results show that the control strategy is able to reduce the charge and discharge depth of BESS on the premise of ensured smoothing of power fluctuation. This work is supported by National Natural Science Foundation of China(No. 51677067)

Beijing New-star Plan of Science and Technology(No. Z141101001814094)and State Grid Corporation of China(No. DG71-15-039).