Performance analysis of lead acid battery model for hybrid power system

This paper presents the mathematical model of a lead-acid battery, which is often used as the energy storage unit in hybrid power systems. The lead-acid battery is complex, nonlinear device exhibiting memory effect. In the hybrid power system, the battery plays very important role in sense that it controls all other energy converters integrated. The operating voltage of a PV system is determined by the battery, the turn-on and turn-off of the diesel genset is guided by the battery SOC. The battery is modeled to elaborate current-voltage characteristics based upon the important phenomenon like self discharge, gassing effect in the view of hybrid power system application. The model is developed in Matlab/Simulink environment. The measured current in the time period of 3 weeks in 90 Ah, 12 V battery is used as input to the model and the output voltage of model is compared with measured one. The current-voltage behavior of the model is much closed to real one. The model is used for real time application.

I. Nomenclature

Battery current

Gassing Current

Battery terminal voltage

Battery internal voltage

SOC

State of charge of the battery

Initial state of charge

AhD

Ampere hour discharged

Ampere-hour discharged at beginning of the process

Nominal ampere-hour of the battery

Main reaction current in the battery

SG

Specific gravity of the battery

Specific gravity at full charged condition

Specific gravity at full charged condition

DK

Fit parameter corresponding to the discharge capacity of the reference cell at an infinitesimal discharge current