Bi-directional DC/DC Converters for Automotive Battery Cell Balancing
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Solution Overview
Problem
Existing electrical power systems for automotive vehicles face challenges in effectively balancing the state-of-charge across multiple energy storage cells, leading to inefficiencies and potential damage due to uneven charging and discharging.
Innovation Solution
The implementation of a bi-directional DC/DC power converter system that connects high-voltage and low-voltage storage cells in series and parallel, allowing energy transfer between them, along with a controller that monitors and balances the state-of-charge by redistributing power between cells, ensuring balanced charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple energy storage cells are connected in series to increase voltage output, then the power delivery capability is improved, but the state-of-charge imbalance between cells worsens
Solution Approach 1:
The system segments the series-connected battery pack into individual cell groups, each monitored and controlled by separate bi-directional DC/DC converters. This allows independent management of each cell group's charge state while maintaining the overall series configuration for high voltage output.
Solution Approach 2:
Bi-directional DC/DC converters are introduced as intermediary devices between the series-connected cells and the load. These converters act as mediators that can transfer charge between cells, equalizing state-of-charge imbalances while allowing the series string to maintain high voltage power delivery capability.
2Reliability
If traditional balancing methods are used to equalize cell voltages, then the state-of-charge balance is improved, but the system complexity and control requirements worsen
Solution Approach 1:
The bi-directional DC/DC converters serve multiple functions: they enable high voltage power delivery through series connection, provide active balancing between cells through controlled charge transfer, and can operate independently to manage individual cell groups. This multi-functionality reduces the need for separate balancing circuits and simplifies the overall system architecture.
Solution Approach 2:
The system employs dynamic control of the bi-directional DC/DC converters that can adapt their operation mode based on real-time cell state monitoring. The converters can switch between charging, discharging, and balancing modes, providing flexible and efficient state-of-charge management without requiring complex static circuitry.
3Power
If series connection of cells is maintained for high voltage output, then the power output is improved, but the ability to balance cells during power delivery worsens
Solution Approach 1:
The bi-directional DC/DC converters serve as intermediary devices that enable active balancing during power delivery operations. By inserting these converters between the series-connected cells and the external circuit, the system can dynamically transfer charge between cells while maintaining the high voltage series configuration, thus enabling balancing capability during normal operation.
Solution Approach 2:
The bi-directional DC/DC converters enable continuous balancing operation during power delivery, rather than requiring separate balancing phases. The converters can simultaneously perform power delivery and state-of-charge equalization, ensuring continuous useful action without interrupting the high voltage output to the load.
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 enables continuous balancing of energy storage cells, optimizing energy distribution and extending the lifespan of the battery pack by maintaining target state-of-charge levels, even during power delivery to loads, thereby enhancing the overall efficiency and reliability of the electrical power system.
Implementation Method 1
bi-directional DC/DC power converters... capable of transferring energy between the first and second sides
Data Source
AI summary
An energy storage system for an automotive vehicle includes a plurality of energy storage units electrically connected in series and a plurality of bi-directional energy converters each having first and second sides. Each of the first sides is electrically connected with one of the plurality of energy storage units. The system also includes another energy storage unit. The second sides of the plurality of bi-directional energy converters are electrically connected in parallel with the another energy storage unit. Each of the bi-directional energy converters is capable of transferring energy between the first and second sides.