Abstract
AbstractThe rapid developments in the field of electrochemistry, enabled lithium-ion batteries to achieve a very good position among all the other types of energy storage devices. Therefore they became an essential component in most of the modern portable and stationary energy storage applications, where the specific energy and the life time play an important role. In order to analyze and optimize lithium-ion batteries an accurate battery model for the dynamic behavior is required. At the beginning of this paper four different categories of electrical models for li-ion cells are presented. In the next step a comparison between equivalent circuit diagrams and fractional rational functions with the complex variable s is shown for lithium-ion battery modeling. It is described how to identify the parameters of the models in the time domain and also in frequency domain. The validation of the different models is made for high and low dynamic current profiles. In the first step the dependency of all model parameters on the temperature and on the battery age is neglected. These effects will be taken into account in the continuation of this work
Highlights
In order to analyze and optimize systems with Li-ion batteries, such as smart grids with big energy storage devices, photovoltaic, and other systems, it is necessary to have accurate electrical models of all the components in the system
Equivalent Circuit Model with RLC Elements. It uses a network of R, L and C elements to simulate the dynamic characteristics of the Li-ion cell, and a voltage source to model the open circuit voltage (OCV) as shown in Fig.1, demonstrating one time constant (OTC) model and two time constants (TTC) model [11]
The ohmic resistance Ro of the battery is calculated during short interruptions of the current signal, while OTC and TTC model parameters are estimated during long interruptions using nonlinear least squares algorithm [11]
Summary
In order to analyze and optimize systems with Li-ion batteries, such as smart grids with big energy storage devices, photovoltaic, and other systems, it is necessary to have accurate electrical models of all the components in the system. In the way to develop an accurate model for Li-ion batteries both time and frequency domain behaviors of the model should be investigated thoroughly For this purpose two groups of models have been investigated in this paper. The research work which is published in the paper is a step forward on the way to simulate a big energy storage system in the research project “IRENE” (Integration of Renewable Energies and Electromobility). This energy storage system (300kW, 170kWh) includes inverters, transformers, filters, and other power electronic devices [7]
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