Dual Frequency Hierarchical Modular Multilayer Battery Balancer Architecture

This article presents a dual frequency hierarchical modular multilayer balancer (MMB) architecture capable of performing electrochemical impedance spectroscopy (EIS) and self-heating for battery systems. The MMB comprises two layers of balancing circuits: a cell-level balancer operates at a few MHz with miniaturized size; and a string-level balancer operates at a few hundred kHz to achieve high efficiency and rapid balancing. By reusing the balancer circuitry, the cell-level balancer can perform EIS, and the string-level balancer can perform battery self-heating. The key contributions of this article include: first, the circuit topology and multi-input-multi-output (MIMO) power flow control of the dual frequency hierarchical balancer; second, a miniaturized common-mode (CM) Class-D based 4-port cell-level balancer for wide bandwidth EIS; and third, a high efficiency multiactive-bridge (MAB) based 12-port string-level balancer for self-heating. A MMB prototype with a 12-port 200 kHz string-level balancer and four 4-port 13.56 MHz cell-level balancers is built and tested with a battery string comprising sixteen Li-ion battery cells. The MMB is capable of performing EIS up to 100 kHz and self-heating across a wide frequency range (100 Hz-18 kHz). The 100-W 12-port string-level balancer achieves 93% peak efficiency. The 30-W 4-port cell-level balancer achieves 74% peak efficiency. Experimental results validated the performance and functionality of the MMB system.