Battery Characterization and Dimensioning Approaches for Micro-Grid Systems

Renewable Energy Sources (RES) are used to produce energy, but their uncertain and intermittent nature requires the integration of storage devices, especially batteries, into MG systems. The main aim is to store excess produced energy for further usage when not enough energy is available. Battery modeling and characterization are mandatory to identify their parameters and study their performance within MG systems. The optimum size of energy production systems and storage devices must be determined to continuously supply electricity to the building. An instrumentation platform, composed of recent sensing and actuating equipment, for MG energy management and battery characterization has been developed. Simulation and experimental results show the effectiveness of the proposed methodology. Several battery models, including electrical-circuit models and electrochemical models, have been developed to predict the batteries' behavior. Electrical-circuit models, such as the first order RC model and the second order RC model, are widely used due to their accuracy and simplicity. The Recursive least Squares (RLS) algorithm is the most used battery characterization methodology due to its simplicity compared to other methods. It aims to online identify the battery's parameters by minimizing the difference between simulation and experimental results. The battery needs a management system, which is a regulator that regulates the battery's charge and discharge to avoid damaging the battery and the diminution of its life-time. The MG system can be composed of an AC/DC converter that converts the alternative current received from the electric grid to the direct current to operate the DC loads when there is no production and the batteries are empty. However, these converters suffer from many problems, such as poor power quality and low efficiency. Researchers have developed new varieties of rectifiers using new solid-state self-commutating devices, such as MOSFETs and IGBTs, to increase their efficiency and the quality of the power while minimizing their cost. The MG system has been modeled and evaluated using both simulations and experiments under the same conditions to study its behavior and validate the developed components' models. The system is composed of five components: PV panels for producing electricity, batteries for supplying electricity, a regulator to control the batteries' charge and discharge, a rectifier that converts AC to DC, and the electric grid for supplying the building when there is no production and the batteries are empty. The proposed methodology has been applied to a real MG system, and the results show the effectiveness of the proposed approach. The system has been simulated and experimentally validated, and the results show that the proposed approach can accurately predict the behavior of the MG system. The methodology can be applied to other MG systems to improve their performance and efficiency.