Battery Pack Bus Switching to Limit Contactor Inrush Wear
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Solution Overview
Problem
The existing energy storage systems in vehicles face premature contactor failure due to high electrical wear, particularly from inrush currents when connecting battery packs to the common traction voltage bus, leading to costly replacements.
Innovation Solution
A method that involves identifying a non-connected battery pack to be connected to the common traction voltage bus, determining the voltage difference, and actively adjusting the current of the common traction voltage bus to reduce the voltage difference below a predetermined threshold before closing the contactor, thereby minimizing contactor wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the contactor is closed to connect the battery pack to the common traction voltage bus, then the battery pack can power the load or receive charging power, but the contactor is subject to high electrical wear from inrush currents
Solution Approach 1:
The control system performs preliminary actions by detecting the voltage difference between the common traction voltage bus and the battery pack before closing the contactor. When the voltage difference exceeds the threshold, the control system activates at least one connected battery pack to discharge, adjusting the common traction voltage bus voltage to be within the threshold of the battery pack voltage before contactor closure, thereby preventing inrush currents and electrical wear.
Solution Approach 2:
The invention changes the voltage parameter of the common traction voltage bus by controlling the discharge of connected battery packs. This dynamic adjustment of the voltage parameter ensures that the voltage difference remains within a safe threshold, preventing harmful inrush currents when the contactor closes, thus protecting the contactor from electrical wear while maintaining system productivity.
2Power
If multiple battery packs are parallelly connected to meet higher power requirements, then the power capability is improved, but the complexity of the switching arrangement increases
Solution Approach 1:
The control system implements feedback by continuously monitoring the voltage difference between the common traction voltage bus and each battery pack. Based on this feedback, the control system intelligently manages the connection sequence and activates discharge control of connected battery packs to maintain voltage within threshold, simplifying the control logic despite multiple parallel battery packs and reducing switching arrangement complexity.
Data Source
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AI summary
A method for operating a switching arrangement of an energy storage system comprising a common traction voltage bus and a plurality of parallelly arranged battery packs connectable to the common traction voltage bus. The switching arrangement comprising an associated contactor for each battery pack, the contactors being configured to connect the battery packs to and from the common traction voltage bus by closing and opening. The method comprises: identifying a non-connected battery pack to be connected to the common traction voltage bus, determining the voltage difference between the common traction voltage bus and the identified battery pack, adjusting the current of the common traction voltage bus to reduce the voltage difference between the common traction voltage bus and the identified battery pack, closing the contactor associated with the identified battery pack to connect the identified battery pack to the common traction voltage bus.