Battery State Estimation Using Recursive Parameter Correction
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Solution Overview
Problem
Existing battery state estimation methods, such as current integration and OCV estimation, face challenges in accurately estimating state of charge (SOC) and state of health (SOH due to errors from current offsets and equivalent circuit parameters, leading to reduced accuracy over time.
Innovation Solution
A battery state estimation device that combines current integration and OCV estimation methods using recursive estimation units to correct for current offsets and equivalent circuit parameters, incorporating feedback loops to refine SOC and SOH estimates, thereby improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If current integration method is used to estimate SOC, then short-term SOC change can be accurately followed, but estimation accuracy deteriorates with passage of time due to error accumulation from current offset
Solution Approach 1:
The patent implements a feedback mechanism where the OCV estimation method provides periodic corrections to the current integration method. The OCV-based SOC estimation serves as a reference that feeds back to correct the accumulated errors in the current integration method, thereby maintaining long-term accuracy while preserving short-term responsiveness.
Solution Approach 2:
The patent merges two SOC estimation methods (current integration and OCV estimation) into a unified estimation system. The current integration method provides continuous short-term tracking, while the OCV method provides periodic long-term accuracy correction, creating a hybrid approach that leverages the strengths of both methods.
2Measurement precision
If OCV estimation method is used to estimate SOC, then error accumulation is avoided, but short-term estimation accuracy is poor due to susceptibility to equivalent circuit parameter errors and voltage measurement errors
Solution Approach 1:
The patent combines OCV estimation with current integration estimation, where the OCV method provides accurate long-term reference values and the current integration method fills in the short-term dynamics that OCV alone cannot capture, achieving both long-term accuracy and short-term responsiveness.
Solution Approach 2:
The patent introduces an intermediary mechanism where the OCV-based SOC estimation acts as a mediator to correct the current integration method. The OCV estimation serves as an intermediate reference that bridges the gap between continuous current integration and periodic voltage measurement, improving overall estimation accuracy.
3Measurement precision
If weighting and combining of two SOC estimation values is performed, then advantages of both methods are achieved, but errors due to SOH and current offset cannot be removed completely
Solution Approach 1:
The patent uses feedback from the OCV estimation method to actively correct errors in the current integration method. Rather than simple weighting, the OCV-based SOC serves as a feedback signal that identifies and corrects systematic errors including current offset and SOH-related inaccuracies, achieving more complete error removal.
4Measurement precision
If SOH estimation is performed using SOC variation amounts in periods with charge/discharge current exceeding threshold, then current integration error influence is reduced, but estimation reliability decreases when current does not exceed threshold sufficiently long
Solution Approach 1:
The patent introduces OCV-based SOC estimation as an intermediary that provides an alternative path for SOH estimation. When current-based methods are unavailable (current below threshold), the OCV method serves as a mediator to continue SOH estimation, ensuring continuous reliability regardless of current conditions.
Data Source
AI summary
Provided is a battery state estimation device configured to: calculate a first state of charge and a first open circuit voltage corresponding to the first state of charge by using a detection current output from a current detection unit and state-of-charge estimation parameters; calculate a second open circuit voltage and a second state of charge corresponding to the second open circuit voltage by using a detection voltage output from a voltage detection unit and equivalent circuit parameters; recursively estimate and update the state-of-charge estimation parameters by using a state-of-charge error, which is a value obtained by subtracting the first state of charge from the second state of charge; and recursively estimate and update the equivalent circuit parameters by using an open circuit voltage error, which is a value obtained by subtracting the first open circuit voltage from the second open circuit voltage.