Modeling and Control of a Lithium-Ion Battery Emulator Based on Power Converters

Sammanfattning

The lithium-ion battery market has experienced rapid growth in recent years. Considering the large demand for electric vehicles and increasing adoption of renewable energy sources in power systems, it is expected to continue doing so in the future. This trend presents opportunities not only for battery manufacturers, but also for companies that develop equipment which interacts with the batteries, such as power converters and control systems. Research related to batteries faces several infrastructural challenges and safety risks. However, when the variable of interest is the electrical behavior, the batteries may be replaced by power converters controlled to reproduce the battery characteristics, thus known as battery emulators. Therefore, this work proposes one way to implement such an emulator, based on ABB converters and a custom control algorithm. A battery model representing state of charge (SoC), temperature, and voltage dynamics was developed based on measurements from an NCA battery cell, using an equivalent circuit model approach. The battery model was then implemented as part of the control algorithm together with a conventional voltage controller. By the use of Crealizer and DriveLab ACS880, the emulator was tested and evaluated in a controller-hardware-in-the-loop (C-HIL) setting, where digital twins of ABB converters can be simulated and controlled in real-time. The C-HIL simulations revealed that the emulator was able to reproduce the electrical behavior of the modeled battery with mean absolute percentage errors in voltage reference tracking of less than 1 %. The result of this work is a first step towards facilitating research related to lithium-ion batteries by mitigating some of the practical challenges, as well as decreasing costs and safety risks. Future work includes implementing and testing the designed battery emulator control in a real power converter.