Battery String Overcurrent Protection via Staggered Contactor Activation
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Solution Overview
Problem
Existing battery systems face challenges in effectively managing overcurrent conditions, which can lead to equipment damage and inefficiencies due to variations in overcurrent protection device activation times, potentially causing arcing and failure in multiple string configurations.
Innovation Solution
The implementation of a battery management system (BMS) that actively controls the opening of contactors with varying time delays to ensure passive protection devices like fuses can open before active protection devices, thereby preventing excessive current flow and reducing the risk of arcing and failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If active protection devices (contactors/relays) are used for overcurrent protection, then system response speed is improved, but device complexity and risk of arcing increase
Solution Approach 1:
The patent divides the protection system into two independent segments: passive protection devices (fuses) and active protection devices (contactors/relays). Each segment operates independently with its own activation characteristics, allowing the system to benefit from both fast passive response and controlled active response without the complexities of coordinating a single device type.
Solution Approach 2:
The passive protection devices (fuses) are designed to activate first before the active protection devices (contactors/relays). This preliminary action by the fuse opens the circuit during overcurrent events, preventing the active devices from experiencing excessive current that would cause arcing and failure, while still maintaining the fast response benefit.
2Device complexity
If passive protection devices (fuses) are used alone, then device simplicity is maintained, but protection response time is insufficient
Solution Approach 1:
The patent combines passive protection devices (fuses) and active protection devices (contactors/relays) into a unified protection system. The fuse provides immediate response by melting and opening the circuit, while the contactor/relay provides additional protection and can be controlled to open under specific conditions, achieving both simplicity and fast response.
3Quantity of substance
If multiple string configurations are used to scale battery systems, then system capacity is improved, but risk of arcing and failure increases
Solution Approach 1:
The patent applies segmentation by dividing the battery system into multiple independent string configurations, each with its own protection devices. This allows the system to scale capacity by adding more strings while maintaining independent protection for each string, preventing failure in one string from affecting others and reducing overall arcing risk.
Data Source
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AI summary
A battery system (14) has a controller and multiple parallel connected battery strings, with each string including at least one battery (20), a passive overcurrent protection device (42A-42D) and an active overcurrent protection device. The passive overcurrent protection device may be configured to disconnect the string from the battery system when an electrical current in the string exceeds a first threshold value, and the active overcurrent protection device may be configured to disconnect the string from the battery system upon activation by the controller. The controller (26) may be configured to (a) activate a first active overcurrent protection device of a first string of the multiple strings at a first time, and (b) activate a second active overcurrent protection device of a second string of the multiple strings at a second time different from the first time.