A High-Efficiency Capacitor-Based Battery Equalizer for Electric Vehicles

Abstract

Technology in electric vehicles has increased substantially in the past decade. Moreover, it is projected to grow at record highs in the coming years since these vehicles are needed to reduce the contamination related to the transportation sector. One of the essential elements of an electric car is its battery, due to its cost. Batteries comprise parallel and series-connected cell arrangements to meet the power system requirements. Therefore, they require a cell equalizer circuit to preserve their safety and correct operation. These circuits keep a specific variable of all cells, such as the voltage, within a particular range. Within cell equalizers, capacitor-based ones are very common as they have many desirable characteristics of the ideal equalizer. In this work, an equalizer based on the switched-capacitor is proposed. A switch is added to this technology that allows the disconnection of the capacitor from the circuit. In this way, an equalization process can be achieved without excess transfers. Therefore, a more efficient and faster process can be completed. In addition, it allows another equalization variable to be used, such as the state of charge. This paper studies the operation, power design, and controller design of the converter. Moreover, the proposed equalizer was compared to other capacitor-based architectures. Finally, simulation results were presented to validate the theoretical analysis.

Average Model of Switched-Energy-Tank Battery Equalizer for Accelerated Performance Assessment

“…Active methods transfer energy from high-voltage cells to low-voltage cells via an energy tank. Such an energy tank can be a converter [17][18][19][20][21][22][23], an inductor in the switched-inductor equalizer (SI-E) [24][25][26], a capacitor in the switched-capacitor equalizer (SC-E) [27][28][29][30][31], or a resonance circuit in the switched-resonance equalizer (SR-E) [32][33][34]. Due to their high equalizing capabilities and efficiency, as well as the similarity of their operations, they can be referred to as switched-energy-tank equalizers (SET-Es).…”