Battery-ultracapacitor storage devices to mitigate power fluctuations for grid connected PV system

This paper presents a control strategy based on energy storage systems to minimize the output power fluctuations for a PV system. Solar energy is naturally intermittent with stochastic fluctuations, by virtue of which, stability and power quality of grid operation are affected. This makes grid integration of PV system cumbersome. The aim of this study is to develop a control strategy to deliver smoothened power to the grid, using battery and ultracapacitors for a grid connected hybrid system. The fluctuating power is absorbed by a battery and ultracapacitors during erratic solar power variation, thus being able to mitigate the power fluctuations to the grid. Bidirectional converters are used in tandem with a battery and ultracapacitors to ensure active energy flow between the grid and the storage systems. The inverter control strategy is implemented such that it will maintain a constant DC link voltage. The PV power system is controlled to extract maximum power. Dynamic modeling and simulation study are accomplished using MATLAB/Simulink™.