Battery String Switching Control for SOC Balancing Across Modules
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Solution Overview
Problem
Existing battery systems in vehicles struggle to efficiently balance the state of charge (SOC) across 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 optimal connection phases and durations of battery strings to balance SOC, allowing for series, parallel, or combination connections, and switches to minimize SOC error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery strings are connected in series or parallel without active balancing, then the system can provide power, but the state of charge (SOC) becomes uneven across strings, reducing battery life and performance
Solution Approach 1:
The system dynamically switches between series and parallel connections of battery modules based on real-time SOC measurements. The controller adjusts the connection configuration adaptively to balance SOC across strings, transforming a static battery system into a dynamic one that self-balances during operation.
Solution Approach 2:
The system employs periodic switching between series and parallel configurations at predetermined intervals. This periodic action allows the battery strings to alternately charge and discharge in a controlled manner, achieving SOC balancing over time through repeated cycles of connection changes.
2Adaptability or versatility
If the battery system uses fixed connection configurations, then the control system is simple, but it cannot adapt to changing power demands and SOC imbalances
Solution Approach 1:
The battery system transitions from fixed connection configurations to dynamic reconfigurability. The controller receives SOC data and power demand information, then automatically adjusts the connection topology (series/parallel switching) in real-time, enabling the system to adapt to varying operational requirements while managing complexity through automated control.
Solution Approach 2:
The battery system is designed to perform multiple functions through a single reconfigurable architecture. The same battery modules can operate in different connection configurations (series for high voltage, parallel for high current) to meet different power demands, eliminating the need for separate systems for different operating modes.
3Reliability
If battery modules operate independently without coordination, then each module can function autonomously, but SOC imbalance accumulates across the battery system
Solution Approach 1:
The system implements a feedback control mechanism where the controller continuously monitors SOC of individual battery strings and uses this information to determine optimal switching decisions. The feedback loop ensures that SOC imbalance is detected and corrected through appropriate series/parallel reconfiguration, maintaining reliability while managing charging efficiency.
Solution Approach 2:
The system merges the operation of multiple battery modules into a coordinated system. By combining modules in series or parallel based on SOC conditions, the system achieves collective optimization where the whole battery system performs better than the sum of independent modules, improving both SOC balance and charging efficiency.
Data Source
AI summary
A battery system includes: at least two battery modules, each including at least three strings of battery cells that are configured to, at different times be: connected in series and to a first positive terminal via first switches; connected in parallel and to a second positive terminal via second switches; and disconnected from both of the first and second positive terminals; and a switch control module configured to: during operation in a first power mode: determine periods of phases, respectively; and determine periods for the strings, respectively, to be connected to the second positive terminal during the phases; during operation in a second power mode: set the periods of the phases, respectively, to be equal in length; and set the periods for the strings, respectively, to be equal in length; and selectively actuate the switches based on the periods of the phases and the periods for the strings.