Battery Contactor Opening Sequence for Wear-Balanced Switching
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Solution Overview
Problem
The frequent mechanical and electrical wear of contactors in energy storage systems of vehicles leads to premature contactor failure, resulting in increased maintenance costs and reduced system lifespan.
Innovation Solution
A characterization model is developed to estimate contactor wear based on system parameters such as current, voltage, temperature, inductance, and altitude, allowing for controlled opening and closing sequences to distribute wear evenly among contactors, thereby predicting maintenance needs and extending the switching arrangement's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If contactors are frequently opened and closed to manage battery pack connections, then the switching arrangement can adapt to varying power requirements, but contactor wear increases leading to premature failure
Solution Approach 1:
The system changes operational parameters by implementing different opening sequences for contactors based on their wear state. The control unit monitors wear indicators and dynamically adjusts which contactor opens first, second, or last during disconnection events, thereby distributing mechanical and electrical stress unevenly across contactors to equalize their wear rates and extend overall system life
Solution Approach 2:
The system transitions from a static contactor operation mode to a dynamic one where the opening sequence is continuously adapted based on real-time wear monitoring. The control unit dynamically reconfigures the disconnection sequence by selecting different contactors to open first based on their current wear state, making the system adaptive and extensible
2Device complexity
If contactors are opened in a fixed sequence, then the control logic is simple, but wear is unevenly distributed leading to premature failure of specific contactors
Solution Approach 1:
The system implements a feedback mechanism where the control unit continuously monitors wear indicators of contactors (such as contact resistance, opening voltage, or mechanical position) and uses this information to dynamically adjust the opening sequence. This feedback loop ensures that contactors with higher wear are opened earlier in the sequence, distributing wear more evenly across all contactors
Solution Approach 2:
The system enables self-service by allowing the contactors to effectively monitor their own wear state and the control unit to automatically adjust operational sequences based on this self-reported information. The control unit autonomously reconfigures the opening sequence without external intervention, equalizing wear distribution across the contactor array
3Speed
If all battery packs are disconnected simultaneously, then the system response is fast, but the last contactor to open experiences excessive wear from handling the full system voltage and current
Solution Approach 1:
The system segments the disconnection process into multiple sequential stages rather than a single simultaneous event. The control unit opens contactors in a predetermined sequence (first, second, last) where the last contactor to open handles only the residual voltage and current from remaining connected battery packs, significantly reducing its wear compared to handling the full system power
Solution Approach 2:
The system performs preliminary actions by opening the first and second contactors before the last contactor. This preliminary disconnection of most battery packs reduces the voltage and current burden on the final contactor, protecting it from excessive wear while maintaining overall system responsiveness
Data Source
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AI summary
A computer system comprising processing circuitry configured to: - provide a characterization model for each one of a plurality of contactors of a switching arrangement, each contactor being configured to connect and disconnected an associated battery pack of an energy storage system of a vehicle by closing and opening, respectively, the characterization model defining contactor wear for contactor opening with regards to a plurality of system parameters, the system parameters comprising at least current and voltage during contactor opening, - determine the system parameters during operation of the switching arrangement, - estimate, for each one of the contactors, the contactor wear by applying the determined system parameters to the corresponding characterization model; - control the order in which the contactors are opened in response to the estimated contactor wear, and/or predicting maintenance of contactor, or contactor exchange, in response to the estimated contactor wear.