Vehicle Power System Voltage Stabilization via Residual Power Routing
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Solution Overview
Problem
The dual battery type electric power system for vehicles experiences voltage drops in the main battery, leading to discomfort for drivers due to fluctuations in regenerative electric power generation and consumption, which affects the performance of electrical loads like headlights and windshield wipers.
Innovation Solution
An electric power system with an alternator, main and sub storage devices, and a control device that manages regenerative electric power generation and discharging, maintaining the main battery's terminal voltage within a specified range by controlling the electric power converter to transmit residual generated power to the sub storage device during speed reduction and vice versa during braking, using a rectifier and regulator with field current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large charging current is applied to the sub battery during regenerative braking, then the regenerative electric power generation efficiency is improved, but the main battery terminal voltage drops excessively causing electrical load performance degradation
Solution Approach 1:
The invention introduces an electric power converter as an intermediary device between the main battery and sub battery. This converter acts as a mediator that controls the charging current flow, allowing the system to achieve high regenerative power generation while preventing excessive current from causing main battery voltage drops that would degrade electrical load performance.
Solution Approach 2:
The invention dynamically changes the charging current parameter based on the main battery's state of charge (SOC). When the main battery SOC is high, the charging current to the sub battery is increased to maximize regenerative power generation. When the main battery SOC is low, the charging current is reduced to prevent main battery voltage drops, thus maintaining electrical load performance stability.
2Reliability
If the charging current to the sub battery is reduced to maintain main battery voltage, then electrical load performance is maintained, but the regenerative power generation efficiency decreases
Solution Approach 1:
The invention implements dynamic control of the charging current to the sub battery based on real-time monitoring of the main battery's state of charge. The control device continuously adjusts the charging current parameter, increasing it when the main battery has sufficient charge capacity and reducing it when the main battery charge level is low, thereby optimizing both regenerative power generation efficiency and main battery voltage stability under varying operating conditions.
3Loss of energy
If the alternator generates maximum electric power during vehicle speed reduction, then the energy recovery is maximized, but the main battery voltage fluctuates causing driver discomfort
Solution Approach 1:
The invention segments the energy storage function into two separate batteries: the main battery that supplies power to electrical loads and the sub battery that specifically stores regenerative electric power. This segmentation allows the alternator to generate maximum electric power during braking for maximized energy recovery, while the sub battery absorbs the excess power without causing voltage fluctuations that would affect driver comfort through electrical load performance changes.
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 system stabilizes the main battery's voltage, enhances regenerative power generation efficiency, and prevents excessive voltage drops, ensuring consistent performance of electrical loads while reducing fuel consumption and maintaining a simple structure.
Implementation Method 1
The alternator is driven to generate an electric power by a rotary power transmitted from an internal combustion engine of a vehicle
Implementation Method 2
The alternator is comprised of a rectifier and a regulator having a field current control switch
Data Source
AI summary
An ECU in an electric power system for a vehicle controls a DC-DC converter so that an alternator transmits a residual generated electric power to a sub battery while a terminal voltage of a main battery is maintained within an optimally specified voltage range. This residual generated electric power is obtained by subtracting from a maximum generating electric power of the alternator an electric power to be consumed by electric loads and an electric power with which the main battery is charged. This can suppress any fluctuation of the voltage of electric power of the electric power system, namely, the output voltage of the alternator and the voltage of the main battery, and perform a maximum regenerative electric power generation. The sub battery is efficiently changed with the regenerative electric power.