Design and Implementation of Assisting Converter-Based Integrated Battery Management System for Electromobility Applications

This paper presents a high power density battery management system for electromobility applications that integrates voltage step-up and cell balancing functions inside a single converter topology. The presented system is based on assisting conversion concept, implemented with multiple dual-active bridge (DAB) converter modules. The assisting conversion, where the converter is only processing a portion of the output power proportional to the voltage difference between the battery pack and the output of the converter, allows for the use of a smaller converter than those of conventional systems. Also, at the system level, this type of conversion results in a higher power processing efficiency. The modular structure of the converter provides multiple connections to battery cells and allows on-line cell balancing during standstill, charging, and discharging of the battery pack. The operation of the system is regulated by a practical digital controller that performs cell balancing and, at the same time, regulates the output voltage. Experimental results obtained with a 24–48 V, 200-W, 100-KHz converter for small scooters demonstrate that the assisting converter is capable of providing the two previously mentioned functions while having a smaller volume and better power processing efficiency than both the conventional DAB and boost-based solutions. The assisting DAB converter runs at a peak efficiency of a 95.4% and processes only a maximum of a 66% of the output power.