KR20230055179A - Apparatus and method for estimating SOC - Google Patents

Abstract

The present invention provides an SOC estimation device and an SOC estimation method using the same. The SOC estimation device includes: a battery including a plurality of battery cells capable of charging and discharging; a measuring unit which measures the voltage and current of the battery; an average calculation unit which calculates the average of the voltage and current; and a SOC estimation unit which estimates the SOC using the average voltage and average current calculated from the average calculation unit.

Description

SOC estimation apparatus and method {Apparatus and method for estimating SOC}

The present invention relates to an apparatus and method for estimating SOC of a battery, and more particularly, to an apparatus and method for estimating SOC applicable to a battery apparatus using alternating current and voltage.

Recently, as the demand for portable electronic products such as laptop computers and mobile phones increases rapidly, and the development of electric vehicles, storage batteries, robots, and satellites is in full swing, research on high-performance batteries that can be repeatedly charged and discharged is actively underway.

Currently commercialized batteries include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium batteries. It is in the limelight due to its low energy density and high energy density.

Electrical and electronic devices that use batteries as power must be equipped with a battery management system (BMS) to control the operation of the battery. The BMS may monitor states such as temperature, voltage, and current of the battery, and control battery balancing and charging or discharging through state of charge (SOC) estimation based on the monitored battery state. Here, SOC is a parameter representing the relative ratio of the current capacity to the maximum capacity representing the electrical energy stored in the battery when the battery is fully charged, and can be expressed as 0 to 1 (or 0% to 100%). can For example, when the maximum capacity of the battery is 1000 ampere-hours (Ah) and the capacity currently stored in the battery is 750 Ah, the state of charge of the battery is 0.75 (or 75%).

1 is a graph of a voltage estimation method in which an SOC algorithm is a process of estimating SOC in general. Reference numerals A and B compensate this with the values for estimating the voltage, and compare it with the actual measured value of reference numeral C to estimate the SOC. 2 is a graph showing voltage waveforms when alternating current is input. In T2, the voltage is normally estimated as in the general situation, but in T3, the voltage is changed in a wave form by the alternating current, and thus the value estimated by the algorithm and the actual measured value are different. As a result, erroneous estimation occurs, and the estimation method considering the measured voltage at T4 differs from the actual measured voltage.

In the SOC algorithm, when estimating the SOC, not only the voltage estimation but also the measured current value are used at the same time. When the AC current is input, the voltage has a wave-like shape due to the AC current. At this time, in order to avoid a problem, the input current should be simultaneously recognized in the form of a wave and the movement of the voltage and current should be synchronized. However, due to the characteristics of BMIS, the current uses the average value of a certain period and the voltage uses the instantaneous measurement value. When AC current is input, the voltage is input in a wave shape and the current is input in a line shape with relatively little change. At this time, the voltage and current are asynchronous, and the SOC algorithm produces an incorrect estimate.

That is, the conventional SOC algorithm is designed to correspond to DC current and voltage, and in particular, the Extended Kalman Filter SOC estimation method is not suitable for AC current and voltage.

Korean Patent Registration No. 10-2066702

The present invention provides a device and method for estimating SOC applicable to a battery device using alternating current and voltage.

The present invention provides an SOC estimation device and method for estimating SOC by calculating an average value of AC voltage.

An SOC estimating device according to an aspect of the present invention includes a battery including a plurality of chargeable/dischargeable battery cells; a measurement unit for measuring voltage and current of the battery; an average calculation unit that calculates an average of the voltage and current; and an SOC estimating unit estimating SOC using the average voltage and average current calculated by the average calculating unit.

The measurement unit measures AC voltage and AC current.

The average calculator calculates an average voltage and average current from the AC voltage and AC current.

The average calculator includes an average voltage calculator that calculates the average voltage and an average current calculator that calculates the average current.

The average voltage calculator calculates an average voltage from an average of instantaneously measured voltage values of sequentially input AC voltages.

The average current calculation unit calculates an average by integrating currents input for a predetermined time.

An SOC estimation method according to another aspect of the present invention includes measuring voltage and current of a battery including a plurality of chargeable and dischargeable battery cells; calculating an average of the voltage and current; and estimating SOC using the calculated average voltage and average current.

AC voltage and AC current of the battery are measured.

Average voltage and average current are calculated from the AC voltage and AC current.

The average voltage is calculated from the average of instantaneously measured voltage values of sequentially input AC voltages.

The average current is calculated by integrating currents input for a predetermined time.

According to an embodiment of the present invention, the SOC estimating device may include an average calculating unit to calculate an average of state data of the battery, and the SOC estimating unit may estimate the SOC using the average value of the calculated data. That is, the average calculator may calculate averages of AC voltage and AC current of the battery to generate average voltage and average current, and the SOC estimator may estimate SOC using the average voltage and average current. Therefore, since the SOC is estimated by calculating the average of the AC voltages, the voltage value does not fluctuate, preventing errors in SOC estimation. That is, when the current and voltage measured from a conventional battery are AC, the average current and instantaneous voltage are output. Since the AC voltage is output, the voltage value fluctuates, resulting in an error when estimating the SOC. However, since the present invention estimates the SOC by calculating the average of AC voltages, the voltage value does not fluctuate, preventing errors in SOC estimation.

1 is a SOC estimation graph of a general voltage estimation method.
2 is a graph showing voltage waveforms when alternating current is input.
3 is a block diagram for explaining the configuration of a battery device including an SOC estimation device according to an embodiment of the present invention;
4 is a block diagram of an SOC device according to an embodiment of the present invention.
5 is a schematic diagram for explaining the operation of some components of an SOC estimation device according to an embodiment of the present invention.
6 is a flowchart illustrating a SOC estimation method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only these embodiments make the disclosure of the present invention complete, and the scope of the invention to those skilled in the art. It is provided for complete information.

3 is a block diagram for explaining the configuration of a battery device including an SOC estimation device according to an embodiment of the present invention, and FIG. 4 is a block diagram of the SOC device according to an embodiment of the present invention. 5 is a schematic diagram for explaining the operation of some components of the SOC estimating device according to an embodiment of the present invention.

3 to 5 , a battery device according to an embodiment of the present invention includes a battery 100 providing energy to an electric/electronic device including a plurality of chargeable/dischargeable battery cells, and a state of the battery 100 It may include a BMS 200 that manages the battery 100 by measuring and estimating the capacity, lifespan, etc. of the battery 100 accordingly. Here, in the present invention, the battery 100 outputs an AC current and voltage, and the BMS 200 calculates an average value of the AC current and voltage to estimate the SOC. The battery device according to an embodiment of the present invention will be described in more detail for each component as follows.

The battery 100 can be charged and discharged to provide energy necessary for driving electric and electronic devices. That is, the battery 100 may be charged and store electric energy of a predetermined capacity and discharged to provide electric energy for operating the electric scooter. The battery 100 may include a plurality of battery modules, and the battery modules may include a plurality of battery cells capable of being charged and discharged. That is, a battery module may be formed by including a plurality of battery cells and by binding the plurality of battery cells in a predetermined unit, and a plurality of battery modules may form one battery 100 . Meanwhile, a plurality of battery cells may be connected in series and/or in parallel in various ways to meet specifications of an electric scooter. Of course, a plurality of battery packs each including a plurality of battery cells may also be connected in series and/or in parallel. Here, the type of battery cell is not particularly limited, and may include, for example, a lithium ion battery, a lithium polymer battery, a nickel cadmium battery, a nickel hydride battery, a nickel zinc battery, and the like.

The BMS 200 measures the state of the battery 100, estimates the capacity and lifespan of the battery 100 accordingly, and manages the battery 100 using the estimated state information. That is, the BMS 200 may measure states such as voltage, current, and temperature of the battery 100 and estimate functions such as capacity and lifespan of the battery 100 using state information. In addition, the BMS 200 may control charging or discharging of the battery 100 according to the functional state estimated using such state information. For example, when the capacity of the battery 100 is insufficient, it is possible to notify the user that the battery 100 needs to be charged so that the battery 100 can be charged, and when the capacity of the battery 100 is sufficient beyond the set capacity Electrical energy for driving an electric/electronic device may be provided. The BMS 200 includes a measurement unit 210 that measures the state of the battery 100, such as voltage, current, and temperature, and an average calculation unit 220 that calculates an average of the current and voltage measured by the measurement unit 210. ) and the SOC estimator 230 estimating the SOC using the average voltage and current calculated through the average calculator 220, and controlling the battery 100 according to the estimation result of the SOC estimator 230 A control unit 240 and a storage unit 250 for storing information of the battery 100 may be included. Here, the measurement unit 210 may measure the AC voltage and current from the battery 100, and the average calculating unit 210 calculates averages of the AC current and voltage to generate average current and average voltage, thereby generating an average of the AC input. It functions as a correction filter for The BMS 200 will be described in more detail for each component as follows.

The measurement unit 210 may be provided to measure the state of the battery 100 . The measurement unit 210 measures states such as voltage, current, and temperature of the battery 100 . To this end, the measuring unit 210 may include a voltage sensor 211 for measuring voltage, a current sensor 212 for measuring current, and a temperature sensor 213 for measuring temperature. At this time, the measurement unit 210 may measure states such as current and voltage of the battery module and battery cell. That is, the state of each of a plurality of battery cells may be measured, or the state of a battery module in which a plurality of battery cells are bundled may be measured. To this end, the measuring unit 210 may include a plurality of sensors. That is, at least one voltage sensor 211 , at least one current sensor 212 , and at least one temperature sensor 213 may be included. The voltage sensor 211, the current sensor 212, and the temperature sensor 213 periodically measure the voltage, current, and temperature of the battery 100 and provide the measurement results to the average calculation unit 220 or the estimation unit 230. do. The measurement result may be provided to the average calculator 220 or the estimator 220 as an analog signal or a digital signal. The voltage sensor 211 measures the voltage applied between the positive electrode and the negative electrode of the battery 100 and provides it to the average calculating unit 220 . As an example, the voltage sensor 211 may include a differential amplifier circuit outputting a voltage signal corresponding to a voltage difference between the positive and negative terminals of the battery 100 . Here, the voltage sensor 211 may measure an AC voltage. That is, the voltage sensor 211 may measure the AC voltage of the battery 100 and provide it to the average calculator 220 . In addition, the current sensor 212 is a sense resistor or a hall sensor, and generates a signal corresponding to the magnitude of the charging current and provides it to the average calculation unit 220 . The current sensor 212 may measure not only the charging current but also the magnitude of the discharging current. Here, the current sensor 212 may measure an alternating current. That is, the current sensor 212 may measure the AC current of the battery 100 and provide it to the average calculator 220 . Also, the temperature sensor 213 may be, for example, a thermal coupler used for temperature measurement. The temperature sensor 213 generates a signal corresponding to the temperature of the battery 100 and provides it to the SOC estimation unit 230 .

The average calculation unit 220 calculates an average value of the AC voltage and current measured by the measuring unit 210 . That is, the average calculator 220 may include an average voltage calculator 221 that calculates an average value of AC voltage and an average current calculator 222 that calculates an average value of AC current. The average voltage calculator 221 calculates an average of AC voltages measured by the voltage sensor 211 of the measurement unit 210 . To this end, the average voltage calculator 221 may calculate an average of instantaneously measured voltage values of sequentially input AC voltages, for example. For example, as shown in FIG. 5 , instantaneously measured voltages are input from the measurement unit 210 at intervals of 250 ms, which is the data update cycle of the BMIC/BMS (in1 to in4), and instantaneously measured voltage values are sequentially input. The average voltage can be output by calculating the average with the previous cycle voltage. That is, the first input voltage (in1) is output as it is (out1), the second input voltage (in2) is output after calculating the average value with the first input voltage (in1) (out2), and the third input voltage (in3 ) is output by calculating the average value with the second input voltage in2 (out3), and the fourth input voltage in4 is output by calculating the average value with the third input voltage in3 (out4). Of course, the average voltage calculating unit 221 may calculate the average value of the input voltages in various other ways. For example, the average value may be calculated by integrating the input voltages for a predetermined time. The average current calculation unit 222 calculates and outputs an average of the AC currents measured by the current sensor 212 of the measuring unit 210 . To this end, the average current calculation unit 222 outputs an average value by integrating currents input for a predetermined period of time. For example, the average current calculator 222 accumulates the input current for 250 ms and outputs an average value. Of course, the average current calculator 222 may calculate the average value of the input currents in various ways, for example, it may calculate and output the average of two sequentially input alternating currents. That is, the average of two sequentially input AC currents may be calculated, such that the first input current is output as it is and the second input current is output after calculating an average value of the first input current.

The SOC estimator 230 estimates the SOC of the battery 100 . There may be various methods for estimating SOC. As a first method, the capacity of the battery 100 estimated from the SOH estimator (not shown) and the current of the battery 100 measured from the measurement unit 210 and the average value calculated from the average calculation unit 220 are used. We can estimate the SOC of (100). That is, the SOC estimator 230 calculates the SOC of the battery 100 by integrating the average current value calculated from the average calculator 220 for a predetermined time and dividing it by the battery capacity estimated from the SOH estimator. can be estimated As a second method, the SOC estimator 230 may estimate the SOC using the open circuit voltage (OCV) of the battery 100 . That is, the SOC may be estimated by referring to the initial OCV table stored in the storage unit 250 for the OCV measured by the measurer 210 and extracting a matched SOC. For example, if the OCV measured by the measurement unit 210 is 3560 mV, it may be estimated that the SOC is 40% by referring to the OCV table. As a third method, the SOC estimator 230 may estimate the SOC by measuring the impedance of the battery 100 . As a fourth method, the SOC estimator 230 estimates the SOC of each battery 100 using measurement data after charging and discharging the battery 100 . For example, the SOC estimator 230 calculates a first SOC after discharging when battery discharge occurs, and calculates a second SOC after charging when charging follows after discharging. Also, when re-discharging continues after charging, the third SOC is calculated after re-discharging. Then, these operations are repeatedly performed. In this case, the SOC estimator 230 may estimate the SOC of the battery using voltage, current, and temperature measurement value information based on a Kalman filter or an extended Kalman filter. That is, the SOC estimator 230 models the OCV of the battery, the internal resistance, and the resistor-capacitor parallel circuit as an equivalent circuit connected in series, and uses a linear or nonlinear function and a current integration method using the factors of the equivalent circuit model as variables. Estimating the SOC of the battery by estimating the SOC and correcting the estimated SOC using the sensing data generated in real time by the measurement unit 210 and the average voltage and current calculated by the average calculating unit 220, thereby estimating the SOC of the battery. can do.

The controller 240 may generate a control signal for managing and controlling the battery 100 according to a result of estimating the state of the battery 100 according to the SOC estimator 230 . That is, if the battery 100 needs to be charged according to the estimation result of the SOC estimator 230, the control unit 240 can generate a corresponding signal to control a charging switch (not shown), and When the state of charge is sufficient, a discharge switch (not shown) may be controlled by generating a control signal for providing electrical energy to the electric/electronic device. That is, although not shown, the BMS 200 includes a charge switch and a discharge switch to charge the battery 100 by driving the charge switch or the discharge switch according to a control signal from the control unit 240 according to the state of the battery 100. Or you can discharge it.

The storage unit 250 may store various data for management of the battery 100 . For example, the storage unit 250 may store data such as the type of the battery 100, voltage and current for charging and discharging, and SOC, SOH, and SOP according thereto. Accordingly, the charging and discharging of the battery 100 may be controlled using the data of the storage unit 250 . The storage unit 250 may include flash memory, electrically erasable programmable read-only memory (EEPROM), static RAM (SRAM), ferro-electric RAM (FRAM), phase-change RAM (PRAM), magnetic RAM (MRAM), and the like. Non-volatile memory may be used.

As described above, the SOC estimating device according to an embodiment of the present invention includes an average calculation unit 220 to calculate an average of the state data of the battery 100 measured by the measurement unit 210, and to calculate an average value of the calculated data. The SOC estimator 230 may estimate the SOC using That is, the average calculation unit 220 calculates the average of the AC voltage and AC current of the battery 100 measured by the measurement unit 210 to generate average voltage and average current, and uses the average voltage and average current The SOC estimator 230 may estimate the SOC. Therefore, the present invention can prevent errors in estimating SOC. That is, when the current and voltage measured from the conventional battery 100 are AC, the average current and instantaneous voltage are output. Since the AC voltage is output, the voltage value fluctuates, causing an error when estimating the SOC. However, since the present invention estimates the SOC by calculating the average of AC voltages, the voltage value does not fluctuate, preventing errors in SOC estimation.

As another embodiment, the BMS of the present invention may be configured in a form in which an AC correction filter, that is, an average calculating unit 220 is connected in series to a conventional BMS including the above-described measuring unit 210 . That is, a typical BMS outputs an average value for current and an instantaneous measured voltage value for measured AC current and AC voltage values. In order to reduce the error, an AC correction filter that calculates an average of instantaneously measured voltage values, that is, an average calculator 220 is connected in series to the output of the measurement unit 210, and the current/voltage value passing through the AC correction filter is SOC It is supplied to the estimation unit 230. The AC correction filter outputs the BMS measured value as it is for the current value, and calculates and outputs the average value of the instantaneously measured voltage values for the voltage in the manner described above.

6 is a flowchart illustrating a SOC estimation method according to an embodiment of the present invention.

Referring to FIG. 6 , the SOC estimation method according to an embodiment of the present invention includes a process of measuring the state of the battery 100 (S110) and calculating an average of the voltage and current measured from the battery 100 (S110). S120), estimating the SOC using the average voltage and average current (S130), and controlling the charging and discharging of the battery 100 according to the SOC estimation (S140). The SOC estimation method according to an embodiment of the present invention will be described in more detail for each process as follows.

S110: During operation of the battery 100, that is, while current is supplied from the battery 100 to the electric/electronic device and the charging/discharging operation of the battery 100 is in progress, the measuring unit 210 measures the state of the battery 100 do. The measurement unit 210 may include a voltage sensor 211 , a current sensor 212 , and a temperature sensor 213 to measure voltage, current, and temperature of the battery 100 . At this time, the battery 100 may output AC voltage and AC current, and accordingly, the measuring unit 210 may measure the AC voltage and AC current. That is, the voltage sensor 211 may measure the AC voltage from the battery 100 and the current sensor 212 may measure the AC current from the battery 100 .

S120: An average of voltage and current measured from the battery 100 is calculated. That is, the average calculator 220 includes an average voltage calculator 221 that calculates an average value of the AC voltage and an average current calculator 222 that calculates an average value of the AC current measured by the measurement unit 210. Calculate the average value of alternating voltage and current. Here, the average voltage calculator 221 may calculate an average of instantaneously measured voltage values of sequentially input AC voltages, for example. For example, as shown in FIG. 5, voltages measured at intervals of 250 ms are input from the measuring unit 210 (in1 to in4), the first input voltage (in1) is output as it is (out1), and the second input voltage (in1) is output as it is (out1). The input voltage (in2) is output by calculating the average value with the first input voltage (in1) (out2), and the third input voltage (in3) is output by calculating the average value with the second input voltage (in2) (out3 ), the fourth input voltage (in4) is output by calculating an average value with the third input voltage (in3) (out4). Also, the average current calculation unit 222 outputs an average value by integrating the input current for a predetermined time. For example, the average current calculator 222 accumulates the input current for 250 ms and outputs an average value.

S130 : The SOC estimator 230 estimates the SOC of the battery 100 using the average voltage and average current. There may be various methods for estimating SOC. As a first method, the capacity of the battery 100 estimated from the SOH estimator (not shown) and the current of the battery 100 measured from the measurement unit 210 and the average value calculated from the average calculation unit 220 are used. We can estimate the SOC of (100). That is, the SOC estimator 230 calculates the SOC of the battery 100 by integrating the average current value calculated from the average calculator 220 for a predetermined time and dividing it by the battery capacity estimated from the SOH estimator. can be estimated As a second method, the SOC estimator 230 may estimate the SOC using the open circuit voltage (OCV) of the battery 100 . That is, the SOC may be estimated by referring to the initial OCV table stored in the storage unit 250 for the OCV measured by the measurer 210 and extracting a matched SOC. For example, if the OCV measured by the measurement unit 210 is 3560 mV, it may be estimated that the SOC is 40% by referring to the OCV table. As a third method, the SOC estimator 230 may estimate the SOC by measuring the impedance of the battery 100 . As a fourth method, the SOC estimator 230 estimates the SOC of each battery 100 using measurement data after charging and discharging the battery 100 . For example, the SOC estimator 230 calculates a first SOC after discharging when battery discharge occurs, and calculates a second SOC after charging when charging follows after discharging. Also, when re-discharging continues after charging, the third SOC is calculated after re-discharging. Then, these operations are repeatedly performed. In this case, the SOC estimator 230 may estimate the SOC of the battery using voltage, current, and temperature measurement value information based on a Kalman filter or an extended Kalman filter. That is, the SOC estimator 230 models the OCV of the battery, the internal resistance, and the resistance-capacitor parallel circuit as an equivalent circuit connected in series, and uses a linear or nonlinear function using the factors of the equivalent circuit model as variables and a current integration method. By estimating the SOC and correcting the estimated SOC using the sensing data generated in real time by the measurement unit 210 and the average voltage and current calculated by the average calculation unit 220, the SOC of the battery can be estimated. can

S140 : The charging and discharging of the battery 100 may be controlled according to the SOC estimation. To this end, the controller 240 may generate a control signal for managing and controlling the battery 100 according to a result of estimating the state of the battery 100 according to the SOC estimator 230 . That is, if the battery 100 needs to be charged according to the estimation result of the SOC estimator 230, the control unit 240 can generate a corresponding signal to control a charging switch (not shown), and When the state of charge is sufficient, a discharge switch (not shown) may be controlled by generating a control signal for providing electrical energy to the electric/electronic device.

Although the technical spirit of the present invention as described above has been specifically described according to the above embodiments, it should be noted that the above embodiments are for explanation and not for limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical spirit of the present invention.

100: battery 200: BMS
210: measurement unit 220: average calculation unit
230: SOC estimation unit 240: control unit
250: storage unit

Claims (11)

a battery including a plurality of battery cells capable of being charged and discharged;
a measurement unit for measuring voltage and current of the battery;
an average calculation unit that calculates an average of the voltage and current; and
and an SOC estimator for estimating the SOC using the average voltage and average current calculated by the average calculation unit.
The SOC estimation device according to claim 1 , wherein the measuring unit measures an AC voltage and an AC current.
The SOC estimation device of claim 2 , wherein the average calculator calculates an average voltage and an average current from the AC voltage and AC current.
The SOC estimation device of claim 3 , wherein the average calculator includes an average voltage calculator to calculate the average voltage and an average current calculator to calculate the average current. The SOC estimation device of claim 4 , wherein the average voltage calculator calculates an average voltage from an average of instantaneously measured voltage values of sequentially input AC voltages.
The SOC estimation device of claim 4 , wherein the average current calculation unit calculates an average by integrating currents input for a predetermined time.
measuring voltage and current of a battery including a plurality of chargeable and dischargeable battery cells;
calculating an average of the voltage and current;
SOC estimation method comprising the step of estimating the SOC using the calculated average voltage and average current.
The SOC estimation method of claim 7 , wherein the AC voltage and AC current of the battery are measured.
The SOC estimation method according to claim 8 , wherein average voltage and average current are calculated from the AC voltage and AC current.
The SOC estimation method of claim 9 , wherein the average voltage is calculated from an average of instantaneously measured voltage values of sequentially input AC voltages.
The SOC estimation method of claim 10 , wherein the average current is calculated by integrating currents input for a predetermined period of time.

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