HESS-based photovoltaic/batteries/supercapacitors: Energy management strategy and DC bus voltage stabilization

Abstract

The photovoltaic energy enables a variable power generation that is influenced by uncertain fluctuations caused by the weather change (temperature and solar irradiation). Hence, the requirement for an energy storage system is essential to address this major issue. The use of only one energy storage element, such as battery, is insufficient. For this purpose, supercapacitors (SCs) can also be introduced as a power storage device. The combination of batteries and SCs is a viable solution that requires an appropriate energy management strategy. The previous studies are focused on the designing and modeling. In this study, a photovoltaic system with a hybrid energy storage system (HESS) was developed by using batteries and supercapacitors. The development of an energy management strategy requires energy distribution between two different storage mediums i.e. batteries and SCs. Thus, a new dimension for a PI controller design is introduced to stabilize the direct current (DC) bus voltage and command the buck-boost converters associated with batteries and SCs. The DC bus is controlled by voltage to stabilize the DC bus voltage at the reference voltage 400 V. Two other PI controller are used to calculate the reference current of batteries and SCs. The distribution of energy between batteries and SCs is based on a low pass filter in order to eliminate the peak current on batteries and send it to SCs. The energy consumption of batteries and SCs is controlled by the filter constant. The simulation results prove that the proposed sizing design and system model provide good stabilization in the DC bus voltage. Furthermore, the augmented constant filter reduces the state-of-charge (SOC) of the battery; hence the overall lifespans of batteries are increased. The consumption of the SoCbat = 57.60% for τ = 2 s where the consumption of the SoCbat = 48.96% for τ = 16 s.