Battery State Estimation via Periodic Rest Periods
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Solution Overview
Problem
Conventional methods for estimating the state of charge (SOC) of vehicle batteries, particularly in micro-hybrid, mild-hybrid, and hybrid-electric vehicles, are inaccurate due to measurement errors and biases, leading to operational inefficiencies and potential battery instability, as they often require infrequent measurements that increase inaccuracy during vehicle operation.
Innovation Solution
A power control system that facilitates battery state estimation during vehicle operation by establishing regular rest periods with near-zero current levels, allowing for accurate measurements of SOC, state of health (SOH), and other battery parameters, using a sensor-connected energy storage device to monitor and control the battery's state, optimizing rest periods to minimize disruption and ensure accurate data collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional SOC estimation methods are used during vehicle operation, then the battery management system can continuously monitor battery state, but the measurement accuracy deteriorates due to measurement errors and biases accumulating over time
Solution Approach 1:
The patent implements periodic rest periods during which the battery is disconnected from the power network and current is reduced to near-zero levels. During these periodic intervals, accurate SOC measurements are taken when measurement errors do not accumulate, and then these accurate measurements are used to correct the SOC estimates obtained during operation.
2Loss of time
If frequent battery state measurements are taken during operation, then real-time battery monitoring is improved, but measurement accuracy decreases due to accumulated errors and biases
Solution Approach 1:
The system performs preliminary accurate measurements during rest periods before returning to operation. By obtaining accurate baseline measurements when the battery is at rest and current is near-zero, the system can then use these pre-obtained accurate values to correct subsequent measurements taken during operation, effectively carrying forward the accuracy benefit.
3Duration of action of stationary object
If the battery operates continuously without rest periods, then vehicle power supply continuity is maintained, but the ability to perform accurate state estimation is lost
Solution Approach 1:
The system introduces partial rest periods where current is reduced to near-zero but not necessarily completely stopped. This partial disconnection is sufficient to halt error accumulation and enable accurate measurements, while minimizing the impact on overall power supply continuity. The rest periods are optimized to be just long enough for accurate measurement without excessive disruption to vehicle operation.
Data Source
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AI summary
A system for providing power to a power network includes an energy storage device connected to the power network, a sensor connected with the energy storage device for measuring a state of the energy storage device during a rest period, which corresponds to a time span during which a current through the energy storage device is reduced to a level that enables an estimation of a state of the energy storage device. The system further includes a controller connected to the sensor for measuring a state of the energy storage device. The controller selectively establishes rest periods for the energy storage device. The rest periods are established by optimizing between minimization of disruption to normal operation and a need to update a measurement of the state of the energy storage device.