Development of a fuzzy logic based hybrid battery management system for a grid integrated photovoltaic system

Abstract

A new topology using fuzzy logic in grid connected Photovoltaic (PV) system with battery management system (BMS) is proposed and presented here. The photovoltaic cell operation has been analysed under various weather conditions. A 100 kW grid connected PV module with BMS is used for modelling and simulation in MATLAB/Simulink environment. A Maximum Power Point Tracking (MPPT) controller is developed by using intelligent fuzzy logic controller (FLC). Conventional MPPT techniques can be classified according to their complexity of implementation, convergence speed, and accuracy of the tracking method. But FLCs have the advantage of design simplicity as they do not require the knowledge of the exact model and work for nonlinear systems. The proposed FLC is evaluated and compared with Perturb & Observe and conventional Fuzzy logic techniques for grid-connected PV system in order to control the DC-DC converter. Under different solar irradiance and temperature, it gives relatively less oscillation, faster response, and better performance compare to other two techniques. The advantage of integrating BMS parallel with a PV system is that it will provide constant power supply to the load system under varying environmental conditions. Lithium-ion batteries are considered for the battery energy storage due to the advantages and recent improvements of battery technology. In the proposed BMS, fuzzy logic is used to control power management and fault detection of the system. Fuzzy based power management controller operates the bidirectional converter of battery energy storage system. It serves the purpose to support the active power production by charging and discharging the surplus and reduced power generation from PV. Power management controller also controls state of charge to avoid overcharge or deep discharge of the BMS which increase capacity and lifetime of battery. A comparative study on the proposed model of the effect on grid disturbances under different fault conditions is also discussed. For this system, Voltage Source Converter is used as an inverter in parallel with BMS to manage the power injection into the grid extracted from distributed generation. Here overall intermittent behaviour of the combined system is assessed. The proposed BMS performs better in all cases by minimizing voltage deviation and also provides robust response at any system failure or grid faults. This fuzzy logic based combined system can help to reduce the losses and improve power quality as well as stability in a grid connected PV system.