Cascaded Li-Ion Battery Pack Equalization Without Centralized Control
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Solution Overview
Problem
Existing active equalization methods for lithium-ion battery packs rely on centralized controllers and communication links, which can fail in case of communication failures or centralized controller failures, preventing effective battery equalization.
Innovation Solution
A decentralized active equalization method for cascaded lithium-ion battery packs, where each battery cell is connected to a DC bus through an independent equalizer with its own controller, sampling circuit, power supply circuit, drive circuit, and main circuit, enabling voltage and current double closed-loop control without relying on a centralized controller or communication link.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centralized controller is used to coordinate equalization commands for all battery cells, then optimal equalization control can be achieved, but the system becomes vulnerable to communication failures and centralized controller failures
Solution Approach 1:
The patent divides the centralized control system into multiple independent decentralized controllers, each responsible for its own battery cell. This segmentation eliminates the single point of failure in centralized control while maintaining equalization functionality through local autonomous decision-making based on bus voltage comparisons.
2Loss of energy
If passive equalization is used to dissipate excess energy through resistors, then the implementation is simple and low-cost, but energy efficiency is poor due to unnecessary energy consumption
Solution Approach 1:
The patent introduces a DC bus as an intermediary energy transfer medium between battery cells. Instead of directly dissipating energy through resistors, excess energy from high-SOC cells is transferred through the bus to low-SOC cells, enabling active equalization with improved energy efficiency while maintaining relative implementation simplicity.
3Loss of energy
If active equalization transfers energy between battery cells, then energy efficiency is improved, but the system complexity increases due to additional power electronic components
Solution Approach 1:
The patent merges multiple independent equalization circuits into a shared DC bus architecture. Each battery cell connects to the common bus through its own power electronic switch and inductor, allowing energy transfer between any cells through the bus. This merging reduces overall system complexity compared to dedicated point-to-point equalization circuits while maintaining active energy transfer capabilities.
Data Source
AI summary
The present disclosure provides a decentralized active equalization method for a cascaded lithium-ion battery pack. The method includes: connecting each battery cell in the cascaded lithium-ion battery pack to a direct current (DC) bus through an equalizer respectively, where each equalizer includes an independent controller, a sampling circuit, a power supply circuit, a drive circuit, and a main circuit; connecting an input terminal of the main circuit to a corresponding battery cell, and connecting an output terminal of the main circuit to the DC bus. The present disclosure solves the technical problem that an existing cascaded lithium-ion battery pack equalization method cannot achieve equalization when a centralized controller failure or a communication failure occurs, improves the reliability of the equalization method, can make the equalizer work at high efficiency by configuring parameters of C, K, and R, and speeds up the equalization or improves the equalization accuracy. The present disclosure uses a bus structure, which can achieve the equalization of all battery cells at the same time, thereby greatly improving the equalization speed. The present disclosure uses a modular design and can be arbitrarily configured according to the scale of the cascaded lithium battery pack, and has strong scalability.