Battery String MPC Switching for Series-Parallel SOC Balancing
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Solution Overview
Problem
Existing battery systems in vehicles struggle to efficiently balance the state of charge (SOC) across multiple battery strings and modules, leading to uneven charging and discharging, which can reduce battery life and performance.
Innovation Solution
A battery system with a switch control module that uses model predictive control (MPC) to determine the optimal periods for connecting battery strings to terminals, balancing SOCs by adjusting the connection periods based on SOC differences between strings and modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery strings are connected in parallel to charge/discharge simultaneously, then charging speed and power output are improved, but SOC imbalance between strings increases
Solution Approach 1:
The system dynamically adjusts the connection configuration of battery strings between series and parallel arrangements based on real-time SOC measurements. The controller monitors SOC levels and reconfigures the battery architecture adaptively, transitioning from static to dynamic operation to maintain SOC balance while optimizing power output.
Solution Approach 2:
The controller implements periodic switching between series and parallel connections for different battery strings. By alternating connection configurations in time-based cycles, the system ensures that strings which were previously discharged more quickly receive extended charging periods, thereby balancing SOC levels across all strings over time.
2Stress or pressure
If battery strings are connected in series, then voltage output is improved, but current capacity and power delivery are reduced
Solution Approach 1:
The system dynamically reconfigures battery string connections between series and parallel arrangements based on real-time power demands and SOC levels. The controller adjusts the architectural configuration adaptively, transitioning from static to dynamic operation to maintain optimal power delivery while managing voltage output requirements.
3Device complexity
If fixed connection configurations are used, then system complexity is reduced, but ability to balance SOC and optimize performance is limited
Solution Approach 1:
The system employs dynamic reconfiguration of battery string connections controlled by a controller that monitors SOC levels and power demands. This dynamic approach allows the system to adapt its architecture in real-time, balancing SOC across strings and optimizing performance without requiring overly complex manual intervention or fixed configurations.
Solution Approach 2:
The controller automatically monitors SOC levels and manages the reconfiguration of battery connections without external intervention. The system self-regulates by detecting SOC imbalances and autonomously adjusting connection configurations to balance charges, reducing the need for complex external control mechanisms while maintaining high adaptability.
Data Source
AI summary
A battery system includes: switches; two battery modules, each of the two battery modules including three strings of battery cells configured to, at different times be: connected in series and to a first positive terminal via first ones of the switches; connected in parallel and to a second positive terminal via second ones of the switches; and disconnected from both of the first and second positive terminals; and a switch control module configured to: determine state of charges (SOCs) of the strings of battery cells, respectively; determine, using model predictive control, periods of phases, respectively, to balance SOCs of the battery modules; determine, using model predictive control, periods for the strings, respectively, to be connected during the phases to balance the SOCs of the strings of battery cells; and selectively actuate the switches based on the periods of the phases and the periods for the strings of battery cells.