BATTERY STATE ESTIMATOR COMBINING ELECTROCHEMICAL SOLID-STATE CONCENTRATION MODEL WITH EMPIRICAL EQUIVALENT-CIRCUIT MODEL
First Claim
1. A method for determining a state of a battery cell during charging or discharging, said method comprising:
- providing an equivalent-circuit model of the battery cell including a terminal voltage which is equal to a sum of a diffusion-effect voltage drop, a double-layer voltage drop, an ohmic resistance voltage drop and an open circuit voltage;
establishing resistance values and capacitance values associated with the double-layer voltage drop and the ohmic resistance voltage drop in the equivalent-circuit model;
providing a reduced-order electrochemical model for determining an open circuit voltage value based on calculations of solid concentrations of active material at a positive electrode and a negative electrode of the battery cell;
obtaining measured terminal voltage data and measured current data for the battery cell during charging or discharging, where the measured data is obtained using sensors; and
calculating the state of the battery cell, using a microprocessor, based on the equivalent-circuit model, the established resistance values and capacitance values, the reduced-order physics-based model and the measured terminal voltage data and current data.
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Abstract
A battery state estimator which combines an electrochemical solid-state concentration model with an empirical equivalent-circuit model. The battery state estimator uses a reduced-order physics-based electrochemical solid-state concentration model to calculate open circuit voltage of a battery cell, and uses the calculated open circuit voltage in an equivalent-circuit model to evaluate a diffusion voltage drop and other battery cell parameters. The battery state estimator is implemented in an online estimator framework using an extended Kalman filter, with a measured terminal voltage and measured current as inputs. A state of charge of the battery cell can be determined from the calculated open circuit voltage, and the state of charge along with the other parameters from the equivalent-circuit model are used to evaluate battery pack performance and to control battery pack charging and discharging.
34 Citations
20 Claims
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1. A method for determining a state of a battery cell during charging or discharging, said method comprising:
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providing an equivalent-circuit model of the battery cell including a terminal voltage which is equal to a sum of a diffusion-effect voltage drop, a double-layer voltage drop, an ohmic resistance voltage drop and an open circuit voltage; establishing resistance values and capacitance values associated with the double-layer voltage drop and the ohmic resistance voltage drop in the equivalent-circuit model; providing a reduced-order electrochemical model for determining an open circuit voltage value based on calculations of solid concentrations of active material at a positive electrode and a negative electrode of the battery cell; obtaining measured terminal voltage data and measured current data for the battery cell during charging or discharging, where the measured data is obtained using sensors; and calculating the state of the battery cell, using a microprocessor, based on the equivalent-circuit model, the established resistance values and capacitance values, the reduced-order physics-based model and the measured terminal voltage data and current data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for determining a state of a battery cell in an electric vehicle battery pack during charging or discharging, said method comprising:
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providing an equivalent-circuit model of the battery cell including a terminal voltage which is equal to a sum of a diffusion-effect voltage drop, a double-layer voltage drop, an ohmic resistance voltage drop and an open circuit voltage; establishing resistance values and capacitance values associated with the double-layer voltage drop and the ohmic resistance voltage drop in the equivalent-circuit model, where the double-layer voltage drop in the equivalent-circuit model is modeled as a first parallel resistor-capacitor pair and a second parallel resistor-capacitor pair, and the first and second parallel resistor-capacitor pairs have different time constants; providing a reduced-order electrochemical model for determining an open circuit voltage value based on calculations of solid concentrations of active material at a positive electrode and a negative electrode of the battery cell; obtaining measured terminal voltage data and measured current data for the battery cell during charging or discharging, where the measured data is obtained using sensors; calculating the state of the battery cell, using a microprocessor, based on the equivalent-circuit model, the established resistance values and capacitance values, the reduced-order electrochemical model and the measured terminal voltage data and current data, where the state of the battery cell includes the open circuit voltage, the solid concentrations of active material at the electrodes, the diffusion-effect voltage drop and the double-layer voltage drop; and calculating a state of charge of the battery cell based on the calculated open circuit voltage. - View Dependent Claims (12, 13, 14)
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15. A system for determining a state of a battery cell during charging or discharging, said system comprising:
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a voltmeter for measuring voltage data for the battery cell; an ammeter for measuring current data for the battery cell; and a controller in communication with the voltmeter and the ammeter, said controller including a processor and a memory, said controller being configured to compute the state of the battery cell using the measured voltage data and current data as input to a hybrid battery state estimator, where the hybrid battery state estimator includes an equivalent-circuit model and a reduced-order electrochemical model combined in a continuously running numerical predictor-corrector. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification