Dual-Battery DC Link Control for EV Power Peaks and Battery Aging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current electric vehicle systems face challenges in managing high power peaks and maintaining battery health during long routes, as high-energy batteries are prone to premature aging due to high power changes, and existing solutions do not effectively divide labor between energy storage and dynamic power handling.
Innovation Solution
The method involves connecting two batteries to a DC intermediate circuit in different configurations: a high-energy battery with a converter for static operation and a high-performance battery without a converter for dynamic processes, with state-of-charge-dependent battery current specifications controlled using non-linear functions and PI controllers to manage power peaks and maintain optimal charge levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-energy batteries are used to enable autonomous driving over longer distances, then energy storage capacity is improved, but the batteries are prone to premature aging due to high power peaks and significant power fluctuations
Solution Approach 1:
The patent divides the battery system into two separate batteries: a high-energy battery (first battery) for energy storage and a high-performance battery (second battery) for dynamic power handling. This segmentation allows each battery to be optimized for its specific function, preventing the high-energy battery from experiencing damaging power fluctuations while maintaining autonomous driving capability.
Solution Approach 2:
Each battery is assigned different functional qualities: the first battery is optimized for energy storage capacity while the second battery is optimized for power delivery and acceptance. This local quality differentiation ensures that the high-energy battery does not have to handle high power peaks, thereby extending its service life.
2Device complexity
If a single battery is used for both energy storage and dynamic power handling, then device complexity is reduced, but the battery cannot effectively divide labor between static energy storage and dynamic power processes
Solution Approach 1:
The battery system is segmented into two functionally distinct batteries, each optimized for specific tasks. The first battery handles static energy storage while the second battery manages dynamic power processes, creating an effective division of labor that improves overall energy management efficiency despite increased system complexity.
Solution Approach 2:
The control system dynamically switches between the two batteries based on real-time power demands. The second battery is activated during high-power transients (acceleration, regenerative braking) while the first battery maintains steady-state operation, optimizing the performance and longevity of both batteries.
3Device complexity
If the second battery is connected without a converter, then device complexity is reduced and dynamic response is improved, but the state of charge requires disproportionate correction to prevent overcharging or over-discharging
Solution Approach 1:
The control system continuously monitors the state of charge of the second battery and uses feedback control to adjust the battery current specification. When the state of charge approaches extreme values, the control algorithm disproportionately increases correction currents to rapidly return the state of charge to the optimal range, preventing overcharging or over-discharging while maintaining simple hardware architecture.
Solution Approach 2:
The control algorithm dynamically changes the battery current specification parameter based on the state of charge level. The current specification is adjusted disproportionately when the state of charge exceeds threshold values, enabling rapid correction without requiring additional hardware converters.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates, inter alia, to a method for operating an electric vehicle (10) comprising a grid-side converter (13) for connection to a trackside power supply network (20), a DC link (14) connected to the grid-side converter (13), a drive-side converter (15) connected to the DC link (14), and a first battery (50) indirectly connected to the DC link (14) by means of a battery-side converter (70).According to the invention, it is provided that, depending on the state of charge (SoC) of a second battery (60), which is connected to the DC link (14) without an inverter, a battery current setpoint (Iv1) is determined and, using this battery current setpoint (Iv1), at least one of the aforementioned inverters (13, 70) is controlled, wherein the value of the battery current setpoint (Iv1) is chosen to be greater than zero if the state of charge (SoC) exceeds an upper threshold (SW1) or falls below a lower threshold (SW2), and wherein the value of the battery current setpoint (Iv1) is chosen to be disproportionately larger the more the state of charge (SoC) exceeds the upper threshold (SW1) or falls below the lower threshold (SW2).