Battery Power Capability Estimation Using Voltage Spread Offset
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Solution Overview
Problem
Existing battery control methodologies face reduced accuracy in estimating battery power capability due to reactive voltage control strategies, particularly during power pulses, which can affect the precision of remaining battery power estimates.
Innovation Solution
The method involves recording the history of reactive voltage control limit adjustments across different operating conditions, such as state of charge and temperature, to estimate battery power capability by increasing the calibrated voltage control limit based on the voltage spread, and using this recorded data for future power capability estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive voltage control limit adjustments are made to protect weak battery cells, then battery cell protection is improved, but battery power capability estimation accuracy deteriorates
Solution Approach 1:
The system proactively adjusts the voltage control limit before power capability estimation by calculating an offset based on voltage spread and adding it to the nominal voltage control limit. This preliminary adjustment compensates for the reactive control changes that would otherwise distort the power capability estimation, allowing accurate predictions while maintaining cell protection.
Solution Approach 2:
The voltage spread offset acts as an intermediary parameter that bridges the conflict between reactive voltage control and accurate power estimation. By introducing this offset calculation and adjustment mechanism, the system can simultaneously achieve both cell protection through reactive control and accurate power capability estimation by compensating for the control adjustments.
2Measurement precision
If voltage control limit is increased based on voltage spread, then power capability estimation accuracy is improved, but control system complexity increases
Solution Approach 1:
The system changes the voltage control limit parameter dynamically by adding a calculated offset based on voltage spread. This parameter adjustment approach improves power capability estimation accuracy without requiring fundamental changes to the control architecture, maintaining relative simplicity while achieving better estimation.
Solution Approach 2:
The patent replaces complex mechanical or hardware-based solutions with computational methods. Instead of using additional sensors or hardware mechanisms to improve estimation accuracy, the system uses software-based calculations of voltage spread and offset adjustments, substituting computational complexity for physical complexity.
Data Source
AI summary
A method for estimating battery power capability in a torque-generating system having a battery pack with battery cells includes calculating a voltage spread as a difference between an average and minimum cell voltage of the battery pack. The method also includes increasing a calibrated voltage control limit by an offset that is based on a magnitude of the voltage spread, doing so when the minimum cell voltage is less than the control limit, and recording the offset in a memory location referenced by pack operating conditions. Further, the power capability is estimated using the recorded offset when the battery pack operates under conditions that are the same as the operating conditions, and then executing a control action of the system using the estimated power capability. A torque-generating system includes the battery pack, an electric machine, and a controller programmed to execute the above-described method.