Vehicle Electrical System with Selective Battery Unit Coupling
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Solution Overview
Problem
Existing vehicle electrical systems face challenges in efficiently managing voltage between low-voltage and high-voltage sub-grids, particularly in vehicles with start-stop systems and boost recuperation, where lithium-ion batteries may not perform optimally at low temperatures and cannot provide high currents, leading to inefficiencies and reduced system availability.
Innovation Solution
A dual-sub-grid system with a coupling unit that selectively connects high-voltage battery units to a low-voltage sub-grid, using reverse blocking switches and an energy store like a capacitor to stabilize voltage and provide redundant power, ensuring even battery aging and optimal performance across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If lithium-ion batteries are used in the high-voltage sub-grid, then energy storage capacity and service life are improved, but the ability to provide high currents at low temperatures deteriorates
Solution Approach 1:
The battery system is segmented into multiple battery units (first battery unit, second battery unit, etc.) with individual voltage taps. This segmentation allows selective connection of specific battery units to the low-voltage sub-grid based on their state of charge, enabling the system to optimize between energy storage utilization and current delivery capability.
Solution Approach 2:
The coupling unit dynamically switches between different battery units based on real-time operating conditions, including temperature and current demands. This dynamic reconfiguration allows the system to adapt to varying requirements, selecting battery units that can best meet the instantaneous power needs while preserving overall battery health.
2Productivity
If the coupling unit switches between battery units, then optimal performance is maintained, but voltage drops and system instability occur during switching
Solution Approach 1:
The system evaluates the state of charge of all battery units in advance and pre-determines the optimal switching sequence. By planning switching actions ahead of time and selecting appropriate moments for transitions, the system minimizes the impact of switching operations on voltage stability.
Solution Approach 2:
The coupling unit acts as an intermediary between the high-voltage and low-voltage sub-grids, managing the transition between different battery units. It controls the switching process to ensure smooth handover of power delivery, preventing direct conflicts that would cause voltage drops.
3Power
If all battery units are connected in series to maximize voltage, then high-voltage output is achieved, but the flexibility to selectively supply low-voltage sub-grid deteriorates
Solution Approach 1:
The battery system is divided into multiple independent battery units with individual voltage taps, allowing the coupling unit to selectively connect specific units to the low-voltage sub-grid. This segmentation provides the flexibility to choose which battery units to supply based on their state of charge and system requirements.
Solution Approach 2:
The coupling unit dynamically reconfigures the connection topology between battery units and sub-grids based on real-time operating conditions. It can switch between different configurations to optimize for either maximum voltage output or selective supply to the low-voltage sub-grid.
4Device complexity
If a single battery unit supplies the low-voltage sub-grid, then system complexity is reduced, but the redundancy and availability deteriorate
Solution Approach 1:
The battery system is segmented into multiple independently controllable battery units, each capable of supplying the low-voltage sub-grid. This segmentation creates redundancy, as the system can switch between different battery units if one becomes unavailable, thereby improving reliability without requiring a completely separate backup system.
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 cost-effective, high-performance, and efficient energy recovery and storage, supporting start-stop systems and boost recuperation with improved availability and reduced weight, volume, and extended service life, even during cold starts.
Implementation Method 1
a coupling unit (33) which is set up to take energy from the high-voltage sub-grid (20) and feed it to the low-voltage sub-grid (21)
Implementation Method 2
The coupling unit (33) has at least two switches (44, 45) capable of reverse blocking
Implementation Method 3
The low-voltage sub-grid (21) has at least one additional energy store (28) which is set up to generate the low voltage and output it to the low-voltage sub-grid (21)
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to an electrical system (1) for a vehicle, comprising a low-voltage sub-network (21) for at least one low-voltage load (29) and comprising a high-voltage sub-network (20) for at least one high-voltage load (25) and an electric generator (23). The high-voltage sub-network (20) has a battery (40) which is designed to generate a high-voltage and output same to the high-voltage sub-network (20) and which has at least two battery units (41) with individual voltage taps (42). The high-voltage sub-network (20) is connected to the low-voltage sub-network (21) via a coupling unit (33) which is designed to draw energy from the high-voltage sub-network (20) and supply said energy to the low-voltage sub-network (21). The coupling unit (33) is designed to selectively connect the battery units (41) to the low-voltage sub-network (21). The invention further relates to a method for operating an electrical system, to a motor vehicle, and to a battery management system and a computer program which are designed to carry out the method.