Hybrid Vehicle LDC Voltage Control for Fuel Efficiency
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Solution Overview
Problem
Existing low-voltage DC-DC converter systems in hybrid vehicles continue to charge auxiliary batteries unnecessarily when the state of charge is sufficient, leading to inefficiencies in fuel efficiency and energy loss.
Innovation Solution
The system determines whether the vehicle is in regenerative braking mode and adjusts the LDC voltage by switching from regenerative braking mode to electric vehicle mode when the state of charge of the auxiliary battery is satisfactory, thereby optimizing voltage control and reducing unnecessary charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the LDC continues to charge the auxiliary battery during regenerative braking mode, then the battery charge level is maintained, but fuel efficiency deteriorates due to unnecessary charging operations
Solution Approach 1:
The system dynamically changes the LDC output voltage parameter based on the auxiliary battery's state of charge (SOC). When SOC exceeds a threshold during regenerative braking mode, the LDC voltage is reduced to zero, stopping charging operations. This parameter adjustment eliminates unnecessary energy loss while maintaining adequate battery charge levels.
Solution Approach 2:
The control system continuously monitors the auxiliary battery's SOC and provides feedback to the LDC controller. This feedback mechanism enables real-time adjustment of charging operations, allowing the system to stop charging when the battery is sufficiently charged and resume when needed, thereby preventing energy waste while ensuring reliable battery charge levels.
2Loss of energy
If the LDC voltage is reduced to optimize fuel efficiency, then energy loss decreases, but the charging capability of the system deteriorates
Solution Approach 1:
The LDC voltage is dynamically adjusted based on real-time operating conditions. During regenerative braking mode, when the auxiliary battery SOC is high, the LDC voltage is reduced to minimize energy loss. When SOC drops below the threshold or during EV mode, the LDC voltage is restored to full charging capability. This dynamic adjustment resolves the contradiction by making charging capability variable rather than fixed.
Solution Approach 2:
The system employs periodic monitoring of battery SOC and alternating between charging and non-charging states. The LDC operates in cycles of full power charging when needed and reduced power when the battery is sufficient, creating a periodic pattern that balances energy loss reduction with charging capability maintenance.
3Loss of energy
If the LDC output voltage is continuously adjusted, then fuel efficiency is improved, but the control system complexity increases
Solution Approach 1:
The control strategy segments the operating conditions into distinct modes: regenerative braking mode and EV mode. Within each mode, the LDC voltage adjustment follows predetermined rules based on SOC thresholds. This segmentation simplifies control logic compared to continuous complex algorithms, reducing control system complexity while maintaining energy efficiency benefits.
Solution Approach 2:
The system changes discrete voltage parameters (full power, reduced power, zero power) based on SOC thresholds rather than implementing continuous complex voltage optimization. This parameter-based approach simplifies the control system architecture while achieving significant energy loss reduction through strategic voltage adjustments at critical thresholds.
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 approach improves fuel efficiency by minimizing energy loss and optimizing the charging strategy based on the vehicle's mode of operation, ensuring that the auxiliary battery is only charged when necessary.
Implementation Method 1
a low-voltage DC-DC converter (LDC) mounted within a hybrid vehicle charges an auxiliary battery by converting a high-voltage direct-current (DC) voltage output from a high-voltage battery into a low-voltage DC voltage
Data Source
AI summary
A system and method for controlling a low-voltage DC-DC converter (LDC) voltage of a hybrid vehicle are provided. The LDC voltage is optimally adjusted based on which driving mode the vehicle enters, thereby improving fuel efficiency. The method includes determining whether the hybrid vehicle is driven in a regenerative braking mode and whether a value of a state of charge (SOC) of an auxiliary battery is equal to or greater than a first critical value set as a value when charging of the auxiliary battery is unnecessary during the driving in the regenerative braking mode. When the value of the SOC of the auxiliary battery is equal to or greater than the predetermined first critical value, the driving mode is switched from the regenerative braking mode to an electric vehicle (EV) mode, and to variably adjust an LDC target voltage in the EV mode.