Series-Connected DC/DC Converters for Battery Module Decoupling
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Solution Overview
Problem
Existing battery systems face challenges in reliability and maintenance due to high voltage series connections, requiring specialized tools and trained personnel for cell replacement, leading to increased costs and logistical efforts, especially in applications like electric vehicles and stationary systems where a single cell failure can cripple the entire system.
Innovation Solution
The use of DC/DC converters with series outputs and optional freewheeling diodes allows for parallel connection of battery modules with lower terminal voltage, enabling flexible voltage selection and continued operation even if a DC/DC converter fails, eliminating the need for expensive contactors and allowing module replacement without interrupting voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery cells are connected in series to achieve high operating voltage, then the required voltage for electric motors is met, but the system becomes vulnerable to complete failure when a single cell fails and requires expensive contactors for safety disconnection
Solution Approach 1:
The battery system is segmented into multiple independent battery modules, each with its own DC/DC converter. This segmentation allows the system to maintain operation even if one module fails, as other modules can continue to provide power. The high voltage is achieved through series connection of converter outputs rather than direct series connection of all battery cells, isolating failure points.
Solution Approach 2:
DC/DC converters are introduced as intermediary devices between the battery modules and the load. These converters act as mediators that can independently control and isolate each battery module's contribution to the total voltage. This eliminates the need for expensive contactors while maintaining system reliability, as the converters can be switched individually without requiring high-voltage disconnection devices.
2Adaptability or versatility
If a large number of battery cells are connected in series to meet different operating state requirements, then voltage and energy needs are satisfied, but the price, weight, and volume of the battery system increase
Solution Approach 1:
The system employs dynamic voltage control through DC/DC converters that can adjust output voltage based on actual operating requirements. Instead of using a fixed large number of series-connected cells to cover all possible voltage needs, the converters dynamically adjust the effective voltage contribution from each battery module, allowing the system to adapt to different operating states without the weight penalty of oversized battery capacity.
3Power
If battery cells are connected in series to achieve high voltage, then the required power output is obtained, but specialized tools and trained personnel are required for cell replacement, increasing maintenance costs and logistical effort
Solution Approach 1:
The battery system is divided into modular battery modules that can be independently replaced. Each module is a self-contained unit with standardized connections, allowing maintenance personnel to replace individual modules without needing specialized high-voltage tools or extensive training. This modular approach significantly simplifies maintenance while maintaining the required power output through the series connection of converter outputs.
4Object-affected harmful factors
If expensive contactors are provided to de-energize the battery system for safety, then high voltage disconnection is achieved, but the system cost increases significantly
Solution Approach 1:
DC/DC converters serve as intermediary devices that eliminate the need for expensive contactors. The converters can be electronically switched to disconnect individual battery modules from the output without requiring mechanical high-voltage switching devices. This intermediary approach maintains safety by providing controlled disconnection while significantly reducing system cost by eliminating the need for multiple high-voltage contactors.
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 design enhances the reliability and maintainability of battery systems by decoupling output voltage from the number of connected battery cells, enabling flexible voltage adjustment and uninterrupted operation, reducing logistical and maintenance costs.
Implementation Method 1
DC/DC converters each having a first and a second input and a first and a second output... The DC/DC converters are connected in series on the output side
Data Source
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AI summary
A power transmitter for a battery system, a battery system comprising such a power transmitter, and a motor vehicle comprising such a battery system are disclosed. The power transmitter includes a plurality of DC/DC converters, each of which has a first and a second input and a first and a second output. The first and second inputs are designed to connect a battery module, while the DC/DC converters are connected in series at the output end.