Storage battery deterioration diagnosis system

Abstract

To provide a storage battery deterioration diagnosis system that, even if a storage battery is being discharged or charged, can execute deterioration diagnosis without being affected by the battery state.SOLUTION: A storage battery deterioration diagnosis system has: a current supply unit 2 that supplies an AC current to a storage battery 1; a voltage measuring unit 3 that measures the voltage of the storage battery; an operating current measuring unit 5 that measures a charge current or a discharge current of the storage battery 1; and a deterioration determination unit 4 that determines deterioration of the storage battery 1. The deterioration determination unit 4 has: an impedance calculation unit 41 that calculates the impedance of the storage battery 1 from information on the measured current and voltage; a threshold storage unit 42 that stores a threshold for determining deterioration; and a determination unit CPU that estimates the SOC during the calculation of the impedance, corrects the impedance to a numerical value at a predetermined SOC, and determines deterioration of the storage battery 1 from information on the corrected impedance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a deterioration diagnosis system for diagnosing the deterioration state of a storage battery used for an emergency power source or storing surplus power.

Background Art

[0002] Storage batteries are used for emergency power sources during power outages, storing solar power generation power, etc. When a storage battery used for such purposes deteriorates, the power that can be stored decreases and its function cannot be fully exerted. Therefore, it is necessary to grasp the degree of deterioration and replace it as needed. Therefore, as one method for diagnosing this degree of deterioration, there is a device that supplies an alternating current to a storage battery, measures the impedance, and diagnoses the deterioration state from the measured impedance value. However, in this diagnosis method, since the impedance changes depending on the charge amount of the storage battery, it was necessary to diagnose with the charge state of the storage battery, such as a fully charged state, set to a predetermined value. On the other hand, a method of diagnosing without setting such a charge state has been proposed. This is a method of measuring the voltage of a storage battery, estimating the charge amount, correcting the internal resistance from the estimated charge amount, and determining the degree of deterioration (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The method of measuring the voltage of the storage battery and estimating the charge amount can be easily determined because it is not necessary to set the charge amount to a predetermined value. However, it was assumed that the storage battery was not in an operating state, and it could not be applied in a state where power was being supplied to a load or in an operating state such as during charging.

[0005] Therefore, in view of these problems, the present invention aims to provide a battery degradation diagnosis system that can perform degradation diagnosis without being affected by whether the battery is discharging or charging. [Means for solving the problem]

[0006] To solve the above problems, the degradation diagnosis system according to claim 1 comprises a current supply unit that supplies alternating current to a storage battery, a voltage measurement unit that measures the voltage of the storage battery, an operating current measurement unit that measures the charging current or discharging current of the storage battery, and a degradation determination unit that determines the degradation of the storage battery. The degradation determination unit comprises an impedance calculation unit that calculates the impedance of the storage battery from the measured current and voltage information, a threshold storage unit that stores a threshold value for determining degradation, an impedance correction unit that estimates the SOC at the time of impedance calculation and corrects it to a value at a predetermined SOC, and a determination unit that compares the corrected impedance value with a threshold value to determine the degradation of the storage battery. With this configuration, the degree of degradation can be diagnosed by correcting the calculated impedance, without having to perform operations such as separating the battery from the load for degradation testing. SOC stands for State of Charge, and it is an indicator that represents the charge level or charge state.

[0007] The invention of claim 2 is characterized in that, in the configuration described in claim 1, it has a correction data storage unit that stores the relationship between the initial SOC of the storage battery and the storage battery voltage, and the relationship between the initial SOC and the impedance of the storage battery, and the impedance correction unit corrects the impedance calculated by the impedance calculation unit to the impedance at a predetermined SOC based on the information in the correction data storage unit and the measured value of the voltage measurement unit. This configuration allows for highly accurate degradation diagnosis by correcting the impedance calculated from the measured current and voltage information to the impedance at a predetermined SOC (State of Condition). [Effects of the Invention]

[0008] According to the present invention, since the degree of degradation is determined by correcting the calculated impedance information, the degree of degradation can be diagnosed without having to perform operations such as separating the storage battery from the load for degradation inspection. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing an example of a battery degradation diagnosis system according to the present invention. [Figure 2] This is a table showing the relationship between battery voltage and State of Charge (SOC). [Figure 3] A table diagram showing an example of impedance for SOC and SOH. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 is a configuration diagram showing an example of a battery degradation diagnosis system according to the present invention, and the battery degradation diagnosis system 10 includes a current supply unit 2 that supplies alternating current to the battery 1, a voltage measurement unit 3 that measures the voltage generated in the battery 1, a degradation determination unit 4 that determines the degradation, and the like. The degradation determination unit 4 includes an impedance calculation unit 41 for calculating the impedance inside the storage battery 1, a threshold storage unit 42 for storing threshold values ​​for determining degradation, a correction data storage unit 43 for storing correction data for correcting the calculated impedance to a value at a predetermined SOC, and a determination unit CPU 44 for controlling the degradation determination unit 4. The determination unit CPU 44 controls the current supply unit 2 to supply an alternating current of a predetermined value to the storage battery 1, and also functions as an impedance correction unit that corrects the impedance calculated by the impedance calculation unit 41 to the impedance at a predetermined SOC, and as a determination unit that determines deterioration from the corrected information.

[0011] Furthermore, arrow I1 indicates the discharge current supplied by the battery 1 to the load (not shown), or the charging current supplied to the battery 1; 5 indicates the operating current measurement unit that measures the discharge current or charging current; and arrow i1 indicates the alternating current supplied by the current supply unit 2 to the battery 1.

[0012] The battery degradation diagnosis system configured in this way performs degradation diagnosis as follows: First, the relationship between the initial SOC and battery voltage of the battery 1 to be judged, and further, the relationship between SOC and impedance are measured and stored in the correction data storage unit 43. For example, the individual battery voltages at 11 points—SOC 0% (initial), 10%, 20%...100%—and the impedance of battery 1 at each charging state are stored in the correction data storage unit 43. Furthermore, as a threshold, for example, an impedance of 74% SOH is stored in the threshold memory unit 42. Note that SOH (State of Health) is the ratio of the full charge capacity at the time of degradation, with the initial full charge capacity being 100%.

[0013] The diagnosis is performed based on the accumulation of such data. The diagnosis begins with the determination unit CPU 44 controlling the output of alternating current from the current supply unit 2 to the battery 1. This current is supplied while the battery 1 is connected to a load and in operation. That is, it is supplied while the battery 1 is charging or discharging. For example, a 1kHz, 50mA current is supplied from the current supply unit 2.

[0014] The AC component voltage Vi of the measured voltage V of the measurement unit 3 with respect to the AC current i1 supplied from the current supply unit 2 is extracted by the determination unit CPU 44, and the impedance Z of the storage battery is calculated from this voltage Vi and the AC current Ii using the following equation 1. Z = Vi / i1 ···(Equation 1)

[0015] The impedance Z(Z0) calculated in this way is corrected as follows. First, the values ​​obtained for the correction are: (a) The calculated impedance Z (a value obtained from the battery voltage and measured current of the storage battery), for example, 2.77 mΩ (b) Measured voltage (battery voltage of the storage battery), e.g., 3.92V (c) Battery voltage and SOC This is, for example, the data in Figure 2 and the relationship data between SOC and SOH as shown in Figure 3. The SOH of the battery during the measurement in Figure 3 is obtained using "An Example of the Voltage and SOC of the Battery" in Figure 2. For example, when the measured voltage is 3.92 V, it can be seen from Figure 2 that the SOC of the battery is 80%.

[0016] Using this SOC, the measured impedance value is changed to a value that can be used to determine degradation. Here, from Figure 3, the impedance value of the battery under measurement at SOC 50% is obtained. Since the impedance at SOC 50% is proportional to the measured value ZO, if the correction coefficient is k, the impedance Zs at SOC 50% can be obtained by the following formula. Zs = k × Z0 ···(Equation 2)

[0017] And the correction coefficient k is such that when the impedance at SOC 50% and SOH 100% is A, and the impedance at SOH 100% at the SOC when the measured voltage is obtained is B, k = A / B ···(Equation 3) It can be calculated. For example, if the SOC when the measured voltage is obtained is 80%, from Figure 3, the impedance at SOC 80% and SOH 100% is 2.52 mΩ. On the other hand, since the impedance at SOC 50% and SOH 100% is 4.47 mΩ, Z0 = 2.77 mΩ A = 4.47 mΩ B = 2.25 mΩ So, k = 4.47 / 2.25 = 1.99. Therefore, Zs = 2.77 × 1.99 = 5.5 mΩ It becomes like this.

[0018] When the corrected impedance Zs is compared with the data of 5.80 mΩ (the data at SOC 50% in Figure 3) of SOH 74% set as the threshold value, since the corrected impedance Zs < the threshold impedance, the result is judged as "not degraded".

[0019] In this way, the degree of degradation can be determined by correcting the calculated impedance Z0, without having to perform operations such as separating the battery 1 from the load for degradation diagnosis. Furthermore, by correcting the impedance Z0 calculated from the measured current and voltage information to the impedance at a predetermined SOC (State of Condition), degradation can be determined, enabling highly accurate degradation diagnosis.

[0020] Furthermore, since impedance includes both real and imaginary resistance, you can determine the impedance using only one of the values, or you can use both and determine that degradation has occurred if at least one of them exceeds a set threshold. Furthermore, although the impedance is corrected to 50% of the State of Charge (SOC) for the determination, the SOC used as the criterion for determination is arbitrary and can be 100% or 80%. [Explanation of Symbols]

[0021] 1. Storage battery, 2. Current supply unit, 3. Voltage measurement unit, 4. Degradation determination unit, 5. Operating current measurement unit, 10. Storage battery degradation diagnostic system, 41. Impedance calculation unit, 42. Threshold storage unit, 43. Correction data storage unit, 44. Judgment unit CPU (impedance correction unit, judgment unit).

Claims

1. a current supply unit that supplies AC current to the storage battery; a voltage measurement unit that measures the voltage of the storage battery; an operating current measurement unit that measures a charging current or a discharging current of the storage battery; a deterioration determination unit that determines deterioration of the storage battery, the deterioration determination unit includes an impedance calculation unit that calculates the impedance of the storage battery from measured current and voltage information; a threshold value storage unit that stores a threshold value for determining deterioration; an impedance correction unit that estimates the SOC at the time of impedance calculation and corrects the SOC to a predetermined value; A deterioration diagnosis system for a storage battery, comprising: a determination unit that compares the corrected impedance value with the threshold value to determine deterioration of the storage battery.

2. a correction data storage unit that stores a relationship between an initial SOC of the storage battery and a storage battery voltage, and a relationship between the initial SOC and an impedance of the storage battery; 2. The battery deterioration diagnosis system according to claim 1, wherein the impedance correction unit corrects the impedance calculated by the impedance calculation unit to the impedance at the predetermined SOC based on information in the correction data storage unit and the measurement value of the voltage measurement unit.

Images