PhD defence of Asal Zabetian Hosseini – Effective Power Converter Control Solutions for Electric Vehicle Battery Systems

Abstract

In this thesis, performances of battery systems at both the cell and pack levels are examined through modeling and simulations, and control designs and algorithms are proposed and validated via offline simulation and controller-hardware-in-the-loop implementation to improve battery systems efficiency and ease their integration into the power grid.

At the cell level, the state-of-charge and temperature imbalance can cause different aging rates and limit the battery pack’s available capacity. To address these issues, we propose a cell balancing control design for simultaneous state of charge and temperature balancing to subside these imbalances among battery cells during the charging process.

At the pack level, DC fast charging stations are growing in popularity to facilitate the fast charging of electric vehicles. However, they can negatively affect the grid stability by causing fast load changes or exceeding the power transfer limit in the power line. Enabling bidirectional power transfer through vehicle-to-grid for electric vehicles’ batteries, we aimed to ease the growth of DC fast charging stations in grids. This strategy requires control designs considering the battery system limits and characterizations. Distributed and centralized control designs are suggested for off-board bidirectional power electronics converter DC chargers to enable safe and efficient vehicle-to-grid technology.

In the final stage of this study, different validation methods, their applications, and their necessities in the power electronics integration into power systems are studied and proposed control designs are validated via the proposed method for the controller-hardware-in-the-loop validation employing a real-time simulator and a digital industrial microcontroller.

The proposed control solutions aim to manage electric vehicle battery systems more effectively. The obtained results from both offline simulations and the controller-hardware-in-the-loop approach closely align and provide compelling evidence that the proposed controllers significantly enhance the performance and longevity of battery systems.