Control strategy of BESS for smoothing fluctuation of photovoltaic power based on fuzzy control theory

Recently, the penetration of photovoltaic (PV) power in power system has being promoted rapidly. However, the PV power shows drastic fluctuation which presents great challenge to the power grid. Thus, how to mitigate the fluctuation of PV station needs to be solved. Battery energy storage system (BESS) is flexible to charge/discharge and track the fluctuation of PV power, and also BESS integrated with PV station has fast response capability, so it is well suited for smoothing PV power fluctuations. At the same time, it should be noted that BESS has relatively high price per unit size. So how to prolong its lifetime and decrease the average cost per time unit is significant for the application of BESS. In this paper, a control strategy of BESS based on fuzzy control theory is presented to avoid the overdischarge of BESS, accordingly decrease the potential damage to BESS to decrease its lifetime. Also the fuzzy control theory based charge/discharge scheme is presented to adjust SOC to maintain the state of health (SOH) of BESS. The effectiveness of the proposed method has been demonstrated by case study with actual PV power data.