Intelligent Battery Module With Bidirectional DC-DC Converters
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Solution Overview
Problem
Conventional energy storage systems face challenges such as cell capacity variations, reduced operational capacity due to weaker cells, high manufacturing costs, and reliability issues, particularly in high-power applications like electric vehicles, where battery management and cell equalization are inefficient and costly.
Innovation Solution
An energy storage system comprising multiple modules connected in parallel, each with a bidirectional current converter, monitoring module, and controller that manages charging and discharging based on monitored characteristics, allowing for direct cell-level management and isolation of failed modules, eliminating the need for series connections and associated inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery cells are connected in series to increase output voltage, then it is easier to interface with high voltage DC bus, but variations in cell capacity and internal resistance cause weaker cells to overcharge and degrade faster
Solution Approach 1:
The battery pack is divided into multiple independent modules, each with its own bidirectional DC-DC converter. This segmentation allows each module to be managed independently, preventing the propagation of cell capacity variations across the entire pack while maintaining high voltage output through modular series connection.
Solution Approach 2:
Bidirectional DC-DC converters are introduced as intermediary devices between individual battery cells/modules and the main DC bus. These converters act as mediators that isolate cells from direct series connection, enabling voltage matching and current control without requiring perfect cell consistency, thus solving the overcharge problem while maintaining high voltage output.
2Reliability
If cell equalizer technology is used to avoid over-charging weaker cells, then battery life is extended, but additional cost, volume, and weight are added to the system
Solution Approach 1:
The bidirectional DC-DC converters serve multiple functions simultaneously: they enable high voltage output conversion, provide cell equalization during charging, and offer bypass capabilities for failed cells. This multi-functionality eliminates the need for separate equalizer circuits, reducing system complexity, cost, and volume while extending battery life.
Solution Approach 2:
The equalization function is merged into the main DC-DC converter circuitry rather than being implemented as a separate system. The converter's ability to independently control current to each module allows it to perform both power conversion and equalization tasks, thereby extending battery life without adding extra components or increasing system complexity.
3Reliability
If only part of the rated battery pack capacity is used to minimize cell damage, then operational safety is improved, but the usable capacity is reduced
Solution Approach 1:
The system dynamically adjusts the operational capacity of each module based on real-time monitoring of cell state and converter status. By using bidirectional converters that can independently control each module, the system can safely utilize nearly 100% of the rated capacity by preventing overcharge through active control rather than conservative static limits, thereby improving both safety and usable capacity.
Solution Approach 2:
The control system continuously monitors cell voltage, current, and converter status, providing real-time feedback to adjust charging/discharging rates. This feedback mechanism allows the system to safely operate at higher capacity utilization levels by dynamically preventing overcharge conditions, thus increasing usable capacity while maintaining cell protection.
4Reliability
If dissipative balance circuits are used for cell equalization, then over-charging is avoided, but high power loss occurs and equalization speed is slow
Solution Approach 1:
The passive dissipative equalization method (using resistors) is replaced with an active electronic conversion system using bidirectional DC-DC converters. Instead of dissipating excess energy as heat through resistors, the converters actively transfer and store energy in capacitors or batteries, dramatically reducing power loss while maintaining overcharge protection and enabling faster equalization speeds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances energy storage system efficiency, extends operational life, and improves reliability by allowing each module to operate within a safe range, reducing capacity loss and enabling plug-and-play functionality with intelligent module control, while maintaining high power and energy density comparable to conventional systems.
Implementation Method 1
a bi-directional current converter configured for supplying charge to the energy storage source from a power source and for discharging current
Data Source
AI summary
An energy storage system is provided. The system includes a plurality of energy storage modules connected in parallel. Each energy storage module has an energy storage source, a bidirectional current converter configured for supplying charge to the energy storage source from a power source and for discharging current for use by an electrical device, a monitoring module for monitoring the energy storage source and the current converter, and a controller configured to control the current converter based upon monitored characteristics of the storage source and the current converter to produce a respective output signal for each module. A communications module is in connection with each output signal of the energy storage modules and configured for communicating a combined output signal with one of the power source and the electrical device.