Adaptive Cell Balancing of Series Connected Batteries Using Hybrid Droop Controller

Cell Balancing is a significant element of any Battery Management System (BMS) to increase the operational lifetime of batteries. In this paper, a decentralized control structure is proposed for BMS based on hybrid droop concept where, battery cell balancing is achieved through individual DC/DC converters for series connected batteries. The control approach distributes the power sharing among the batteries according to their State of Charges (SOCs). The decentralized control scheme eliminates the need for any communication links among the converters, which makes the system more reliable and robust compared to the conventional systems. Additionally, the output bus voltage regulation makes the system suitable for high voltage applications and grid-tied configurations. The performance of the proposed control algorithm is verified through circuit simulations, and experimental tests.

I. Introduction

The series connection of batteries and cells is preferred approach in achieving high voltage output, due to the elimination of high step-up ratio for the dc-dc converters. However, series connection creates an inherent sensitivity and limitation due to mismatch of cell parameters such as capacity, series resistance, and self-discharge rate resultant by manufacturing tolerances and the temperature distributions [1], [2]. Battery management systems (BMSs) provides a cell-balancing feature for the battery strings to fulfill the functional design requirements over their lifetime.