Battery State of Charge Estimation via Preisach Hysteresis Model
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Solution Overview
Problem
Existing methods for battery state of charge estimation, such as using open circuit voltage, are inaccurate due to battery hysteresis effects from historical charging and discharging cycles, which complicate the determination of the battery's state of charge.
Innovation Solution
A Preisach-model-based algorithm is employed to calculate battery state of charge, considering the hysteresis effects by using a hysteresis model that accounts for historical charge and discharge cycles, with elementary hysterons and weights to estimate the state of charge based on measurable system parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open circuit voltage-based state of charge estimation is used, then the measurement method is simple, but the estimation accuracy deteriorates due to battery hysteresis effects
Solution Approach 1:
The patent segments the continuous hysteresis loop into discrete elementary hysterons with specific threshold pairs (α, β). Each hysteron represents a discrete segment of the hysteresis behavior, allowing the complex continuous problem to be broken down into manageable discrete components that can be individually weighted and summed to predict state of charge accurately
Solution Approach 2:
The patent transforms the state of charge estimation problem by changing parameters from direct voltage measurement to a weighted sum of hysteron states. The hysteron states (q_i) and weights (w_i) are adjusted based on historical charge-discharge patterns, allowing the system to adapt to different operating conditions and accurately capture hysteresis effects that simple voltage measurement cannot
2Measurement precision
If a hysteresis model accounting for historical cycles is used, then state of charge estimation accuracy is improved, but the calculation complexity increases
Solution Approach 1:
The patent performs preliminary action by pre-defining the hysteron structure, threshold pairs, and weight parameters before actual state of charge estimation is needed. The elementary hysterons and their characteristics are established in advance, so that during operation, the system only needs to evaluate the current hysteron states and compute a weighted sum, significantly reducing real-time computational complexity
Solution Approach 2:
The patent creates a simplified computational copy of the physical hysteresis phenomenon through the Preisach model. Instead of simulating complex chemical processes and historical cycles directly, the system uses a mathematical copy consisting of elementary hysterons that replicates hysteresis behavior with much lower computational requirements, making real-time estimation feasible
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 approach provides a more accurate estimation of battery state of charge by accounting for historical dependencies, improving the reliability of battery management systems.
Implementation Method 1
Battery state of charge is difficult to measure directly. One known method to measure battery state of charge is to infer the state of charge from the open circuit voltage. However, such known methods have accuracy shortfalls. Open circuit voltage-based state of charge estimation is influenced by battery hysteresis. Chemical processes internal to the battery create history dependant characteristics which influence battery performance.
Data Source
AI summary
A method of battery state of charge estimation considering battery hysteresis includes using a Preisach-model-based algorithm to calculate a battery state of charge.