Battery Aged Capacity Estimation via Internal Impedance
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Solution Overview
Problem
Accurate estimation of the aged capacity of batteries in energy storage systems used in wind farms is challenging due to the gradual decrease in battery capacity over time, affecting the available energy storage and dispatching efficiency.
Innovation Solution
A method and apparatus that determine the internal impedance of the battery and establish a relationship between maximum capacity and charging cycles to estimate the aged capacity, allowing for precise calculation of the available energy based on state of charge and internal impedance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional battery capacity estimation methods are used, then the estimation process is simple, but the accuracy of aged capacity estimation deteriorates due to gradual battery degradation
Solution Approach 1:
The patent changes the parameter used for capacity estimation from simple state-of-charge measurements to a combination of internal impedance measurements and charging cycle counting. By monitoring how internal impedance changes with aging and correlating it with capacity degradation, the system achieves accurate aged capacity estimation without requiring complex physical models or extensive battery testing.
Solution Approach 2:
The system implements feedback by continuously monitoring internal impedance and using it to update the aged capacity estimation. The estimated aged capacity then feeds back into the energy management system to adjust charging/discharging strategies, creating a closed-loop system that improves accuracy over time while adapting to actual battery degradation patterns.
2Productivity
If battery capacity is not accurately estimated, then control strategies are simplified, but energy storage efficiency and dispatching performance deteriorate
Solution Approach 1:
The system performs preliminary estimation of aged capacity using internal impedance measurements before actual energy dispatch operations. By proactively determining the battery's degraded capacity state and establishing the relationship between impedance and capacity, the system prepares accurate available energy estimates in advance, enabling optimized control strategies for energy storage and dispatching.
3Measurement precision
If internal impedance measurement is implemented, then aged capacity estimation accuracy is improved, but measurement and calculation complexity increases
Solution Approach 1:
The system uses the battery's own electrical characteristics during normal operation to self-assess its aging state. By measuring internal impedance through routine charging/discharging cycles and correlating these measurements with capacity degradation patterns, the battery essentially monitors itself, eliminating the need for external diagnostic equipment or complex disassembly procedures.
Data Source
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AI summary
Embodiments of the invention provide techniques and apparatus for accurately estimating an aged capacity (Eaged ) of a battery in an energy storage system (ESS) used on a wind farm. E aged throughout the life of the battery may be estimated by measuring the internal impedance of the battery and using a relationship between the age of the battery (e.g., a number of charging cycles) and a maximum capacity corresponding to the battery. The state of charge (SOC) may be calculated based on the electromotive force(EMF) of the battery. The actual available energy (E available ) of the battery may be calculated based on the Eaged of the battery and the calculated SOC. In this manner, embodiments of the present invention may allow a wind farm to function as a virtual power plant (VPP)and deliver peak load electricity, regardless of intermittent wind velocity.