Battery Current Limit Control Using Polarization State Estimation
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Solution Overview
Problem
Existing battery control systems inaccurately calculate allowable current values due to the assumption of a constant resistance value, which can lead to excessive current limitations when the actual resistance is smaller during rapid switching between charging, discharging, and pausing periods.
Innovation Solution
A battery control device that uses a battery equivalent circuit model to estimate the internal state of a unit cell, including open circuit voltage and polarization voltage, and calculates a corrected allowable current value by accounting for the influence of polarization, allowing for more accurate current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed resistance value corresponding to a sufficiently large polarization voltage is used, then the allowable current value can be calculated with a small calculation amount, but the allowable current value may be excessively limited when the actual resistance is smaller
Solution Approach 1:
The patent applies dynamics by making the resistance value adjustable rather than fixed. The resistance value is dynamically changed based on the relationship between the actual resistance and the assumed resistance. When the actual resistance is smaller than the assumed resistance, the resistance value used for calculation is reduced accordingly, allowing the system to adapt to changing battery conditions while maintaining both calculation efficiency and accuracy
Solution Approach 2:
The patent changes the parameter of resistance value based on the polarization state and actual measurements. By adjusting the resistance value parameter according to the difference between actual and assumed resistance, the system optimizes the balance between calculation simplicity and current limit accuracy, avoiding excessive current limitation while maintaining computational efficiency
2Device complexity
If a resistance value table reflecting polarization voltage influence is used, then calculation amount is reduced, but the actual resistance value tends to be smaller than the assumed resistance value during rapid switching between charging, discharging, and pausing
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual resistance value and comparing it with the assumed resistance value from the resistance value table. Based on this feedback, the system adjusts the resistance value used for allowable current calculation, ensuring that the current control remains accurate even during rapid switching between charging, discharging, and pausing operations
Solution Approach 2:
The system dynamically adjusts the resistance value based on real-time battery conditions. Instead of using a static resistance value from the table, the patent modifies the resistance value according to the actual polarization state and resistance measurements, enabling reliable current control during dynamic operating conditions
Data Source
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AI summary
An object of the present invention is to provide a battery control device capable of obtaining an allowable charge/discharge current value further accurately reflecting a polarization state of a battery. A battery controller 101 includes a first allowable current value calculation unit 704, a battery equivalent circuit model 702, and a correction amount calculation unit 706t. The first allowable current value calculation unit calculates a first allowable current value Imax1 which is a current limit value of a battery assuming a non-polarization state, based on an open circuit voltage OCV of the battery and upper and lower limit voltages Vmax and Vmin set in the battery. The battery equivalent circuit model 702 estimates a polarization state of the battery at the time of calculating the current limit value. The correction amount calculation unit 706t calculates an allowable current value correction value ΔI for correcting the first allowable current value Imax1 based on the estimated polarization state. The second allowable current value Imax2 which is the corrected first allowable current value is output as an allowable charge/discharge current value of the battery.