Modular Reconfigurable Mixed Battery System With Heterogeneous Modules

Contrary to the half-bridge modules in conventional modular multilevel converters (MMCs) with only serial and bypass operation, emerging topologies bring additional parallel intermodule connectivity, introducing sensorless voltage balancing, load current sharing, and enhanced efficiency. However, matching voltages and characteristics are crucial for the modules to allow for a parallel mode between them, but it is not feasible for mixed-type or heterogeneous battery systems. This article introduces a reconfigurable battery system designed to solve the challenges of integrating batteries with varying characteristics. Using compact coupled inductors and a novel modulation strategy, the system achieves intermediate states between parallel and series modes when dealing with heterogeneous modules. The coupled inductors, with minimal magnetic material and a small footprint, have a negligible common-mode inductance for the high load current and limit circulating currents through high differential-mode inductance. Furthermore, the proposed modulation strategy introduces intermodule dc-dc conversion functionality and enables an efficient bidirectional energy transfer, fully capable of controlling the power exchange between modules widely independently of the output control. This intermodule dc-dc functionality enables effective charge or load balancing among batteries of varying voltages, types, and age. Importantly, the same transistors perform the dc-dc functionality and the output control so that the topology does not need more silicon. Extensive simulations and experiments demonstrate the performance of the system. The proposed system can notably reduce the inductor's core size by more than 80% with the circulating current as high as one-fifth of the load current. The solution also reduces the cost of the inductor by more than four times. Moreover, the findings demonstrate > 15% improvement in conduction and > 50% in switching losses.

Duke Scholars

Author Stefan M Goetz Psychiatry & Behavioral Sciences, Behavioral Medicine & Neur ...