Hybrid Vehicle Mode Switching for Cell Voltage Balance
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Solution Overview
Problem
Hybrid electric vehicles face output limitations and uneven cell charging due to unbalanced battery cell voltages, leading to potential overdischarge and reduced acceleration and smooth gear shift, as existing inter-cell balancing procedures are only performed when the vehicle is stopped and take a significant amount of time to complete.
Innovation Solution
An apparatus and method that includes a voltage sensor to measure cell voltages and a controller to adjust the switching time point between EV and HEV modes based on voltage differences, increasing a threshold value when the difference exceeds a reference value and returning it when the difference does not, to prevent overdischarge by dynamically managing the switching between modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inter-cell balancing procedure is performed only when the vehicle is stopped, then the balancing procedure can be completed with minimal disruption to driving, but it takes one week or more to complete and cannot prevent overdischarge during EV mode operation
Solution Approach 1:
The patent implements dynamic mode switching based on real-time cell voltage differences. When the voltage difference between cells exceeds a threshold, the system dynamically switches from EV mode to HEV mode to activate the balancing procedure, and switches back when the difference is within tolerance. This dynamic adjustment enables continuous balancing during vehicle operation rather than requiring extended stationary periods.
Solution Approach 2:
The system continuously monitors cell voltages and uses this feedback to control mode switching. The controller compares the voltage difference between the highest and lowest voltage cells against a reference threshold, and adjusts the driving mode accordingly. This closed-loop feedback mechanism ensures timely balancing while maintaining vehicle performance.
2Use of energy by moving object
If the vehicle operates in EV mode with unbalanced cell voltages, then electric motor power is utilized efficiently, but specific cells become overdischarged leading to output limitations
Solution Approach 1:
The system uses the HEV mode operation itself as the balancing mechanism. When cell voltage imbalance is detected, switching to HEV mode activates the engine-driven generator, which charges the battery cells at different rates based on their individual voltage levels, thereby self-balancing the cells without requiring external intervention or prolonged stationary charging.
3Device complexity
If a fixed threshold is used for mode switching, then the control logic is simple, but it cannot adapt to varying cell voltage conditions and may trigger unnecessary mode switches
Solution Approach 1:
The patent dynamically adjusts the voltage difference threshold based on the operating mode. When in EV mode, a first reference value is used for comparison, and when in HEV mode, a second reference value is used. This parameter change allows the system to adapt to different operating conditions while maintaining relatively simple control logic. The threshold adjustment prevents unnecessary mode switches and optimizes the balancing effectiveness.
Data Source
AI summary
An apparatus for controlling a driving mode of a hybrid vehicle and a method thereof are provided in which a specific cell, which constitutes a battery, is prevented from being overdischarged by adjusting a switching time point of a driving mode (an electric vehicle (EV) mode or a hybrid electric vehicle (HEV) mode) based on a cell voltage change of the battery mounted in the hybrid electric vehicle. The apparatus for controlling the driving mode of the hybrid vehicle includes a battery including a plurality of cells, a voltage sensor to measure voltages of the cells in the battery, and a controller to control a switching time point from the EV mode to the HEV mode based on the voltages of the cells in the battery, as measured by the voltage sensor.