Hybrid Vehicle Battery Disconnection Control via Electric Machine
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Solution Overview
Problem
In hybrid electric vehicles, existing methods for disconnecting a battery from the traction voltage DC-link are not fully controlled, leading to potential damage and operational interruptions, especially when the battery temperature is outside its operating range or when faults occur, requiring a more reliable and efficient method to maintain vehicle functionality.
Innovation Solution
A method that involves controlling the hybrid vehicle's electrical system to disconnect the battery pack from the traction voltage DC-link by shutting down the power electronics unit, disconnecting the battery pack using a relay, and activating the electric machine as a generator to maintain power to essential auxiliary units, allowing for controlled disconnection and reconnection without the need for an additional battery, thus avoiding surge currents and ensuring continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery pack is disconnected from the traction voltage DC-link when temperature is outside operating range or faults occur, then vehicle safety and reliability are improved, but operational interruptions and potential damage occur due to uncontrolled disconnection
Solution Approach 1:
The control method performs preliminary actions by shutting down the power electronics unit and activating the electric machine as a generator before disconnecting the battery pack. This preparatory sequence ensures that essential auxiliary units are already powered by alternative means when the battery is disconnected, preventing operational interruptions and potential damage from uncontrolled disconnection.
2Productivity
If additional components like auxiliary batteries are added to maintain power during battery disconnection, then operational continuity is improved, but device complexity and cost increase
Solution Approach 1:
The electric machine is designed to perform multiple functions: it serves as a motor during normal operation and as a generator when the battery pack is disconnected. This multi-functionality allows the system to maintain power to essential auxiliary units during battery disconnection without requiring additional components like auxiliary batteries, thereby reducing system complexity while ensuring operational continuity.
3Productivity
If the battery pack is kept connected to maintain power supply, then operational continuity is improved, but damage risk and safety issues occur when battery temperature is outside operating range
Solution Approach 1:
The control method introduces an intermediary power supply mechanism where the electric machine acts as a generator to bridge the power supply gap when the battery pack must be disconnected due to temperature or fault conditions. This intermediary solution allows the system to maintain power supply continuity to essential auxiliary units while protecting the battery from damage by keeping it disconnected from the traction voltage DC-link when outside operating parameters.
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 controlled disconnection and reconnection of the battery pack, ensuring the vehicle can operate without the main battery pack, enhancing vehicle robustness and reducing the risk of damage during temperature extremes or faults, and eliminates the need for an extra battery, providing a simpler and cheaper solution.
Implementation Method 1
the electric machine (18) will start to function as a generator for supplying power to the loads (38) of the vehicle
Implementation Method 2
a relay that can be opened to disconnect the battery pack from the high voltage DC-link
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for controlling a hybrid vehicle electrical system comprising the steps of: driving the vehicle (1) in a first driving mode where the battery pack (4) is connected to said traction voltage DC-link (7) and the battery pack (4) is supplying the electrical auxiliary units (6) with power, shutting down the power electronics unit in order to cease power delivery from the electric machine (3) to the traction voltage DC-link (7) or to the electric machine (3) from the traction voltage DC-link (7), disconnecting the battery pack (3) from the traction voltage DC-link (7) by opening the relay (8), and activating the power electronics unit and controlling output voltage of the power electronics unit to a predetermined level.