Hybrid Vehicle Voltage Converter Dynamic Boosting Control
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Solution Overview
Problem
Hybrid vehicles face challenges in maintaining battery state of charge (SOC) within a predetermined range when the eco-mode switch is activated, leading to reduced fuel efficiency and potential battery degradation due to limitations in generator motor workload and intermittent engine operation.
Innovation Solution
A hybrid vehicle system that includes a voltage converter with a selector and controller to adjust the upper voltage limit, switching between first and second modes based on battery SOC and user power demands, and additional controls for engine operating points and accessory management to maintain SOC and enhance fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the boosting operation of the converter is stopped by turning ON the eco switch to eliminate switching loss, then fuel efficiency is improved, but the workload of the generator motor is limited causing a drop in generated electric power
Solution Approach 1:
The converter's boosting operation is made dynamic rather than static. The controller enables intermittent boosting operations based on real-time conditions (battery SOC, vehicle state, user operations) rather than completely stopping the boosting function. This allows the system to adapt between fuel efficiency mode (reduced boosting) and power generation mode (increased boosting) to resolve the contradiction.
Solution Approach 2:
The controller changes operational parameters of the converter based on battery SOC and vehicle state. When battery charge is sufficient, boosting is reduced to minimize switching loss. When battery charge is low or power demand is high, boosting parameters are adjusted to maximize electric power generation, thus resolving the contradiction between energy loss and power output.
2Loss of energy
If the generator motor workload is limited to enhance fuel efficiency, then switching loss is reduced, but the amount of generated electric power drops causing frequent intermittent engine operation
Solution Approach 1:
The controller implements feedback control by continuously monitoring battery SOC and vehicle state, then adjusting converter boosting operations accordingly. When SOC approaches lower limits or vehicle power demand increases, the controller provides feedback to increase boosting intensity, preventing excessive SOC drops and ensuring reliable battery charge maintenance while managing switching loss.
Solution Approach 2:
The controller performs preliminary assessments of battery charge levels and vehicle operational needs before making boosting decisions. By anticipating when SOC may drop below appropriate ranges, the controller proactively adjusts converter operations to prevent reliability issues before they occur, rather than reacting after problems arise.
3Loss of energy
If the upper limit of boosted voltage is reduced to minimize switching loss, then fuel efficiency is improved, but the system cannot meet high power demands when SOC is low
Solution Approach 1:
The upper voltage limit of the converter is made dynamic rather than fixed. The controller adjusts the voltage ceiling based on real-time conditions: during normal operation with sufficient battery charge, the voltage limit is reduced to minimize switching loss and improve fuel efficiency. However, when battery SOC is low or high power delivery is required, the controller dynamically raises the voltage limit to ensure adequate power supply capability.
Solution Approach 2:
The controller changes the operational parameters of the converter, specifically the upper voltage limit, based on battery SOC and power demand conditions. This parameter adjustment allows the system to optimize between energy efficiency (lower voltage limit) and power delivery capability (higher voltage limit) depending on operational context, resolving the contradiction between these two requirements.
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 enhances fuel efficiency by reducing electrical losses and prevents significant SOC drops below the lower limit, ensuring sufficient electric power generation and maintaining battery health.
Implementation Method 1
a voltage converter for boosting a voltage of the battery and supplying the boosted voltage to the electric motor
Implementation Method 2
a generator capable of generating electric power from mechanical power received from the engine
Implementation Method 3
an electric motor capable of outputting mechanical traction power from the electric power supplied from the battery and the generator
Data Source
Figure 1
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AI summary
Disclosed is a hybrid vehicle wherein such a situation that the residual capacity of a battery drops significantly below the lower limit of a reasonable range is avoided while fuel efficiency is enhanced. The hybrid vehicle (10), comprising an engine (12), a generator (MG1), a battery (50), and an electric motor (MG2) for driving, is further provided with a converter (48) for supplying the voltage of the battery (50) that has been boosted to the electric motor (MG2), an eco-switch (72) for selecting a first mode or a second mode in association with the boosting operation of the converter (48), and a hybrid ECU (66) for changing the upper limit of the voltage boosted by the converter (48) from a first upper limit in the first mode to a second upper limit lower than the first upper limit when the second mode is selected by the eco-switch (72), and changing the upper limit of the voltage boosted by the converter (48) from the second upper limit to the first upper limit when the residual capacity of the battery (50) drops below a threshold.