Battery state-of-charge estimation method and battery management system
First Claim
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1. A battery state-of-charge (SOC) estimation method comprising:
- an SOC table creation step of dividing, by a processor, the entire area of a two-dimensional coordinate system representing a relation between battery open-circuit voltages and battery SOCs into a plurality of segments in which gradients of a linear function according to increase tendencies or decrease tendencies of data represented on the two-dimensional coordinate system are different from each other, at a time point when a battery is charged or discharged at a plurality of different temperatures, and storing, by the processor, function information representative of the relation between battery open-circuit voltages and battery SOCs for each segment in an SOC table;
a parameter estimation step comprising;
generating a control signal, by the processor, to control a control switch unit comprising, a charge control switch installed between the battery and a current source and a discharge control switch installed between the battery and a load receiving the current from the battery, said control signal generation being such that the current inputted to the battery from the current source or outputted from the battery to the load has a pulse form with a predetermined frequency,measuring, by the processor, an inputted current to the battery or an outputted current from the battery, an open circuit voltage of the battery, and a temperature of the battery, andcalculating, by the processor, a resistance value of a resistor applied to a battery equivalent model and capacitance of a capacitor applied to the battery equivalent model;
an SOC calculation step of calculating, by the processor, an SOC of the battery using the function information and the measured current;
an SOC comparison step of acquiring, by the processor, a difference between an SOC extracted by using the function information, measured open circuit voltage of the battery, and measured temperature of the battery, and the SOC calculated at the SOC calculation step; and
a processing step of displaying the calculated SOC when the difference acquired at the SOC comparison step is smaller than a critical value, displaying the calculated SOC and the fact that the difference between the extracted SOC and the calculated SOC is larger than the critical value when the difference between the extracted SOC and the calculated SOC is larger than the critical value and displaying the number of errors indicating that the difference between the extracted SOC and the calculated SOC is larger than the critical value, by the processor.
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Abstract
Provided are a battery state-of-charge (SOC) estimation method and a battery management system which are capable of estimating an SOC using an inexpensive processor and a small-capacity memory. The SOC estimation method includes an SOC table creation step, an SOC calculation step, an SOC comparison step, and a processing step. The battery management system includes a battery, a sensing resistor, a control switch unit, and a processor.
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14 Claims
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1. A battery state-of-charge (SOC) estimation method comprising:
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an SOC table creation step of dividing, by a processor, the entire area of a two-dimensional coordinate system representing a relation between battery open-circuit voltages and battery SOCs into a plurality of segments in which gradients of a linear function according to increase tendencies or decrease tendencies of data represented on the two-dimensional coordinate system are different from each other, at a time point when a battery is charged or discharged at a plurality of different temperatures, and storing, by the processor, function information representative of the relation between battery open-circuit voltages and battery SOCs for each segment in an SOC table; a parameter estimation step comprising; generating a control signal, by the processor, to control a control switch unit comprising, a charge control switch installed between the battery and a current source and a discharge control switch installed between the battery and a load receiving the current from the battery, said control signal generation being such that the current inputted to the battery from the current source or outputted from the battery to the load has a pulse form with a predetermined frequency, measuring, by the processor, an inputted current to the battery or an outputted current from the battery, an open circuit voltage of the battery, and a temperature of the battery, and calculating, by the processor, a resistance value of a resistor applied to a battery equivalent model and capacitance of a capacitor applied to the battery equivalent model; an SOC calculation step of calculating, by the processor, an SOC of the battery using the function information and the measured current; an SOC comparison step of acquiring, by the processor, a difference between an SOC extracted by using the function information, measured open circuit voltage of the battery, and measured temperature of the battery, and the SOC calculated at the SOC calculation step; and a processing step of displaying the calculated SOC when the difference acquired at the SOC comparison step is smaller than a critical value, displaying the calculated SOC and the fact that the difference between the extracted SOC and the calculated SOC is larger than the critical value when the difference between the extracted SOC and the calculated SOC is larger than the critical value and displaying the number of errors indicating that the difference between the extracted SOC and the calculated SOC is larger than the critical value, by the processor. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A battery management system comprising:
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a sensing resistor connected to one end of a battery; a control switch unit comprising, a charge control switch installed between the battery and a current source and a discharge control switch installed between the battery and a load receiving the current from the battery, and configured to transmit a current supplied from the current source to the battery or transmit a current outputted from the battery to the load, in response to a control signal; and a processor configured to generate the control signal, and to measure an open-circuit voltage of the battery, a current inputted to the battery or outputted from the battery, and a temperature of the battery, the processor further configured to calculate parameters of elements applied to an equivalent model of the battery using a measured temperature of the battery, a measured current of the battery, and a measured open-circuit voltage of the battery, and create and store an SOC table using the temperature and the open-circuit voltage of the battery, wherein the processor represents data of a relation between battery SOCs and battery open-circuit voltages on a two-dimensional coordinate system at a plurality of different temperatures at a time point when a battery is charged or discharged, and divides segments according to increase tendencies or decrease tendencies of the data represented on the two-dimensional coordinate system such that gradients of a linear function for respective segments are different from each other, wherein the processor calculates a current SOC of the battery using the temperature of the battery, the open-circuit voltage of the battery, and a gradient and an intercept of the linear function stored in the SOC table, and extracts an SOC based on the open-circuit voltage of the battery when the SOC of the battery was calculated, by referring to the SOC table, issues a command to display the calculated SOC and the fact that a difference between the calculated SOC and the extracted SOC is larger than a predetermined critical value when the difference between the calculated SOC and the extracted SOC is larger than the predetermined critical value, and issues the command to display the calculated SOC when the difference between the calculated SOC and the extracted SOC is smaller than the predetermined critical value, wherein the processor issues a command to store a number of errors in which the fact that the difference between the calculated SOC and the extracted SOC is larger than the predetermined critical value is detected, when the difference between the calculated SOC and the extracted SOC is larger than the predetermined critical value, and to update the data stored in the SOC table when the number of errors is larger than a predetermined reference number. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification