Direct-current power supply system and method and device for estimating health condition of lead-acid storage battery thereof

Abstract

The invention belongs to the technical field of power systems, and particularly relates to a direct-current power supply system and a health condition estimation method and device for a lead-acid storage battery thereof. The method comprises the following steps: S1, acquiring actual operation parameters of a storage battery; the actual operation parameters of the storage battery are the operation parameters of the storage battery obtained according to a preset sampling period when the storage battery is fully charged and the storage battery is subjected to constant-current discharge for continuous set time according to a preset current value; s2, determining the difference condition between the reference operation parameters of the storage battery and the actual operation parameters of the storage battery in the set time; the storage battery reference operation parameters are storage battery operation parameters obtained according to the sampling period within a set time when capacity checking starts when full-capacity capacity checking is performed according to the preset current value before the storage battery is put into operation; and S3, estimating the health condition of the storage battery according to the difference condition obtained in the S2. The technical problems that in the prior art, a health state estimation method cannot be suitable for most transformer substations and is low in universality are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, and in particular relates to a direct current power supply system and a method and device for estimating the health status of a lead-acid battery thereof. Background Art

[0002] Valve-regulated lead-acid batteries have been widely used in station DC power supply systems due to their low price, high stability, non-explosion, mature regeneration technology and other advantages. However, this type of battery also has disadvantages such as short life, many defects or frequent failures. Therefore, online monitoring and health status assessment of lead-acid batteries play an important role in their stable operation.

[0003] The state of health (SOH) of a battery is usually defined from the perspective of capacity or internal resistance, as shown in the following two equations:

[0004]

[0005] Among them, C a C is the actual capacity of the battery when it is fully charged; n is the rated capacity of the battery; R EOL is the internal resistance at the end of battery life; R C is the current internal resistance of the battery; R new It is the internal resistance of the battery when it leaves the factory.

[0006] At present, the estimation of battery health status is mostly based on a single indicator to define the battery health status, such as battery internal resistance, terminal voltage, etc. This method can directly evaluate the operating status of the battery; however, the abnormality of certain indicators does not affect the battery's power supply to the system, but may cause misjudgment by operation and maintenance personnel.

[0007] The Chinese invention patent authorization announcement text with authorization announcement number CN111736084B and authorization announcement date 2022.05.20 discloses a method for predicting the health status of valve-regulated lead-acid batteries based on an improved LSTM neural network. The method uses daily battery parameters such as floating charge voltage, equalization charge current, and equalization charge duration as input to establish an SOH prediction model of the LSTM neural network, and estimates SOH through the LSTM neural network, which greatly improves the accuracy of SOH estimation. However, SOH estimation based on big data algorithms such as LSTM neural networks often requires higher computing power requirements and higher hardware requirements. Moreover, the DC power supply monitoring devices of most current substations do not have the ability to apply large models and advanced algorithms, but require the DC power supply monitoring devices to have the function of health status monitoring. Therefore, the above-mentioned technical solution has low versatility and cannot be applied to most substation DC power supply systems. Summary of the invention

[0008] The purpose of the present invention is to provide a DC power supply system and a lead-acid battery health status estimation method and device to solve the technical problem that the health status estimation method in the prior art cannot be applied to most substations and has low versatility.

[0009] In order to solve the above technical problems, the present invention provides a method for estimating the health status of a lead-acid battery in a DC power supply system. The method comprises:

[0010] S1. Obtaining actual operating parameters of the battery; the actual operating parameters of the battery are: when the battery is fully charged, the battery is discharged at a constant current value for a set time, and the battery operating parameters are obtained according to a preset sampling period;

[0011] S2. Determine the difference between the reference operating parameters of the battery and the actual operating parameters of the battery within the set time;

[0012] The battery reference operating parameters are the battery operating parameters obtained according to the sampling period within the set time at the beginning of the capacity check when the full capacity check is performed according to the preset current value before the battery is put into operation;

[0013] S3. Estimate the battery health status according to the difference obtained in S2.

[0014] The beneficial effect of the above technical solution is that the technical solution of the method for estimating the health status of batteries in a DC power supply system of the present invention is a pioneering invention. When the present invention estimates the health status of the battery, the battery is controlled to periodically perform a shallow core capacity discharge test. And with the battery operating parameters in the full core capacity test as a reference, the battery health status is estimated by the battery operating parameters in the shallow core capacity test. The present invention performs health status assessment by means of testing experiments, without the need to use big data algorithms or advanced algorithms, and greatly reduces the hardware requirements. The present invention solves the technical problem that the health status estimation method in the prior art cannot be applied to most substations and has low versatility.

[0015] Furthermore, the battery operating parameters include at least one of a single cell voltage, a single cell internal resistance and a single cell pole temperature of the battery.

[0016] Furthermore, the method also includes: S4, executing S1 to S3 cyclically according to a preset shallow core capacity cycle.

[0017] Furthermore, the battery health condition in S3 is obtained according to the battery health degree, and the battery health degree calculation formula is:

[0018]

[0019] a1+a2+...+a m =1

[0020] Among them, SOH(i) is the health status of the i-th battery cell; m (i) is the difference between the actual operating parameters of the mth battery of the ith battery cell and the mth battery reference operating parameters of the ith battery cell; a1, a2, ..., a m are the coefficients of m battery operating parameters respectively, and M is the number of battery operating parameters.

[0021] Furthermore, the method further comprises: performing a full capacity core capacity discharge test according to a preset full capacity core capacity cycle; the full capacity core capacity cycle is greater than the shallow core capacity cycle;

[0022] Obtaining a first health degree according to the battery operating parameters within the set time of the full-capacity nuclear capacity discharge test as the actual battery operating parameters and the battery health degree calculation formula;

[0023] The second health degree is obtained according to the nominal capacity and the actual capacity of the battery obtained by the nuclear capacity discharge test; the nominal capacity is: the battery capacity obtained by performing a full capacity nuclear capacity discharge test on the battery before the DC power supply system is put into operation;

[0024] If the error between the first health degree and the second health degree exceeds the error threshold, the battery operating parameter correction coefficients a1, a2, ..., a2 are calculated based on the second health degree and the battery operating parameter correction coefficients a1, a2, ..., a2 within the set time of the full capacity discharge test. m .

[0025] Furthermore, a1, a2, ..., a m The initial value of is obtained by conducting a full-capacity nuclear capacity discharge test on batteries of the same model.

[0026] Furthermore, the preset current value is 0.1C 10 , C 10 is the rated capacity of the battery.

[0027] Furthermore, the battery health status is divided into different levels according to the battery health.

[0028] The present invention also provides a technical solution for a device for estimating the health status of a lead-acid battery in a DC power supply system: a device for estimating the health status of a lead-acid battery in a DC power supply system, comprising a processor, wherein the processor is used to execute a computer program to implement the steps of the method for estimating the health status of a lead-acid battery in a DC power supply system as described above.

[0029] The present invention also provides a technical solution of a DC power supply system: a DC power supply system, including a battery, and further including:

[0030] Discharge device: When the battery is fully charged, it controls the battery to discharge at a constant current for a set time according to a preset current value;

[0031] Battery inspection device: obtains actual operating parameters of the battery and sends them to the DC monitoring device; the actual operating parameters of the battery are: when the battery is fully charged, the battery is discharged at a constant current value for a set time, and the battery operating parameters are obtained according to a preset sampling period;

[0032] DC monitoring device: determine the difference between the actual operating parameters of the battery and the reference operating parameters of the battery, and estimate the health of the battery based on the difference; the reference operating parameters of the battery are the battery operating parameters obtained according to the sampling period within the set time at the beginning of the capacity verification when the battery is put into operation and the full capacity verification is performed according to the preset current value.

[0033] Furthermore, the battery operating parameters include at least one of a single cell voltage, a single cell internal resistance and a single cell pole temperature of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A system block diagram of a DC power supply system embodiment of the present invention;

[0035] Figure 2 The present invention is a flow chart of a method for estimating the health status of a lead-acid battery in a DC power supply system embodiment of the present invention. DETAILED DESCRIPTION

[0036] When the present invention estimates the battery health status, it controls the battery to periodically perform a shallow core capacity discharge test. And with the battery operating parameters in the full core capacity test as a reference, the battery health status is estimated by the battery operating parameters in the shallow core capacity test. The present invention performs health status assessment by means of testing experiments, without the need to use big data algorithms or advanced algorithms, and greatly reduces the hardware requirements. The present invention solves the technical problem that the health status estimation method in the prior art cannot be applied to most substations and has low versatility.

[0037] DC power supply system embodiment:

[0038] A DC power supply system, such as Figure 1As shown, it includes a charging device, a battery pack, a battery inspection device, a discharge device and a DC monitoring device, wherein the discharge device is used to control the discharge of the battery to perform a nuclear capacity discharge test, the battery monitoring device provides battery operating parameter monitoring and uploads the information to the DC monitoring device, and the DC monitoring device is used to calculate the relative error mean between the battery operating parameters and the battery reference operating parameters within the set time, and estimate the battery health status according to the relative error mean.

[0039] Specifically, the method for estimating the health status of lead-acid batteries in a DC power system based on the DC power system is as follows: Figure 2 As shown, the following steps are included:

[0040] 1) In the final stage of commissioning the station DC system, the charging device starts to charge the battery. When the battery is fully charged, the lead-acid battery configured in the system is tested for nuclear capacity discharge. The DC monitoring device is set to control the discharge device at 0.1C. 10 The battery inspection device in the system collects the voltage, internal resistance and temperature of the battery cells in real time during the first half hour of discharge, and records a set of data every 1 minute, and then records a set of data every 30 minutes until the end of discharge. After the nuclear capacity is completed, the nuclear capacity measured by the DC monitoring device reaches 100% of the nominal capacity, then the data recorded in the nuclear capacity process is stored in a fixed position in the DC monitoring device, and used as a reference value for the subsequent prediction of the health status of the battery group;

[0041] 2) Subsequently, according to the cycle set in the DC monitoring device, a shallow core capacity is performed regularly. The shallow core capacity is achieved by first adjusting the floating charge voltage of the device to be slightly lower than 2.0V*N (N is the number of battery cells configured in the DC system), and then connecting the battery discharge device and adjusting its constant current discharge current value to 0.1C 10 , that is, the discharge current (I 10 ) is the regular load current (I j ) and the test discharge current, the discharge device automatically adjusts with the battery outlet current. Refer to the "DL / T724-2021 Technical Regulations for Operation and Maintenance of Battery DC Power Supply Devices for Power Systems" for a 20-minute (set time) capacity check. During the capacity check, record the battery cell voltage, internal resistance and pole temperature every 1 minute. After the shallow capacity check, turn off the discharge device and restore the charging device output to the floating charge voltage value before adjustment to confirm that the system is operating normally.

[0042] 3) Start to compare the records stored in the shallow core capacity process with the first 20 minutes of data during the first core capacity test of the battery, and calculate the relative error mean (i.e., the difference) Er according to formulas (1), (2), and (3) respectively. v (i) Err (i) and Er T (i)

[0043]

[0044] Among them, V i (j) represents the jth voltage value recorded by the i-th battery, V i '(j) represents the jth reference voltage value recorded by the i-th battery; R i (j) represents the jth internal resistance value recorded by the i-th battery, R i '(j) represents the jth reference internal resistance value recorded in the i-th battery; T i (j) represents the jth pole temperature value recorded by the i-th battery, T i '(j) represents the jth reference electrode column temperature value recorded by the i-th battery.

[0045] Then the battery health SOH(i) is calculated according to the following formula:

[0046] SOH(i)=α(1- Er v (i))+β(1- Er r (i))+γ(1- Er T (i)) (4)

[0047] Wherein α, β, γ are coefficients, and α+β+γ=1. The initial values ​​of the three coefficients are experimental values ​​calculated based on experimental data after three full-capacity verifications of the same type of battery, and i is the battery number.

[0048] According to the above calculation results, the following table is used for comparison:

[0049] category Value (SOH(i)) state Category I 0.85～1.0 excellent Category II 0.75～0.85 good Category III <0.75 Difference

[0050] The health status of each battery is obtained based on the comparison results and displayed in the DC monitoring device, and an early warning is issued for battery cells in poor condition, prompting the user to check and confirm the battery.

[0051] In this embodiment, the difference between the voltage, internal resistance, temperature of the battery cell and the reference value is measured by the relative error mean. In other embodiments, other statistical indicators can be used to measure the difference, such as the relative square error mean, the relative standard deviation mean, etc.

[0052] In this embodiment, the battery health is comprehensively evaluated by the voltage, internal resistance and temperature of the battery cell. In other embodiments, only one or two of the indicators may be used to evaluate the battery health, but the evaluation result may have a certain error. Alternatively, it may be prohibited to limit the evaluation of the battery health to the above three indicators. When the battery health is evaluated by multiple indicators, the battery health can be obtained by the following formula:

[0053]

[0054] a1+a2+...+a m =1

[0055] Among them, SOH(i) is the health status of the i-th battery cell; m (i) is the difference between the actual operating parameters of the mth battery of the ith battery cell and the mth battery reference operating parameters of the ith battery cell; a1, a2, ..., a m are the coefficients of m battery operating parameters respectively, and M is the number of battery operating parameters.

[0056] 4) According to the battery operation and maintenance requirements, it is necessary to perform periodic full capacity verification. When performing full capacity verification, the health of the battery (i.e., the first health) is calculated using formula (4) based on the data recorded in the previous 20 minutes.

[0057] Then, the actual battery health (i.e., the second health) is calculated using the actual nuclear capacity after the nuclear capacity is completed and the nominal capacity value, and the first health and the second health are compared. If the relative error value between the two exceeds 5% (i.e., the error threshold), the least squares method is used to correct the three coefficients α, β, and γ based on the data of this full-capacity nuclear capacity test and save them to make the calculated value closer to the true value.

[0058] Example of a method for estimating the health status of a lead-acid battery in a DC power supply system:

[0059] A method for estimating the health of a lead-acid battery in a DC power supply system, the method comprising: S1, obtaining actual operating parameters of the battery; the actual operating parameters of the battery are: when the battery is fully charged, the battery is discharged at a constant current value for a set time, and the battery operating parameters are obtained according to a preset sampling period; S2, determining the difference between the reference operating parameters of the battery and the actual operating parameters of the battery within the set time; the reference operating parameters of the battery are the battery operating parameters obtained according to the sampling period within the set time at the beginning of the capacity verification when the battery is fully verified at a preset current value before it is put into operation; S3, estimating the health of the battery according to the difference obtained in S2. The specific method for estimating the health of a lead-acid battery in a DC power supply system has been introduced in sufficient detail in the above-mentioned DC power supply system embodiment, and will not be repeated here.

[0060] Embodiment of the device for estimating the health status of lead-acid batteries in a DC power supply system:

[0061] A device for estimating the health status of a lead-acid battery in a DC power system includes a processor, and the processor is used to execute a computer program to implement the steps of the method for estimating the health status of a lead-acid battery in a DC power system as described above. The specific method for estimating the health status of a lead-acid battery in a DC power system has been described in sufficient detail in the above-mentioned DC power system embodiment, and will not be repeated here.

[0062] The present invention has the following characteristics:

[0063] The invention first selects three parameters of conventional battery measurements in the DC system as the battery health prediction, and the reference value measured is the actual battery measurement value used in the system. Then the prediction value will periodically optimize the coefficient value of each parameter to make the prediction more and more accurate. Finally, the method only needs to modify the DC monitoring device program in the DC system, and the changes to the entire system are relatively small, which is convenient for promotion and application. The invention also has the following effects.

[0064] Preventive maintenance: Through health prediction, the trend of battery performance degradation can be discovered in time, so that appropriate maintenance measures can be taken, such as balanced charging, adjusting charging and discharging strategies, etc., to delay the battery aging process and extend the overall service life of the battery.

[0065] Avoid overuse: When the battery health is reduced to a certain level, timely replacement of the battery can avoid excessive use due to poor battery performance, thereby protecting the battery from further damage.

[0066] Reduce failure rate: The health of batteries in DC systems directly affects the overall performance of the equipment. Through health prediction, poorly performing batteries can be discovered and replaced in a timely manner, thereby reducing the risk of equipment downtime due to battery failure.

[0067] Improve system stability: In battery pack applications, the failure of a single battery may trigger a chain reaction, affecting the performance of the entire battery pack. Health prediction helps to detect and deal with potential problems in a timely manner, improving the stability of the entire system.

[0068] Reduce maintenance costs: Through health prediction, battery problems can be discovered and dealt with in a timely manner, avoiding the escalation of problems and resulting in higher repair or replacement costs.

[0069] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments without creative work, or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for estimating the health status of a lead-acid battery in a DC power supply system, characterized in that: The method includes: S1. Obtaining actual operating parameters of the battery; the actual operating parameters of the battery are: when the battery is fully charged, the battery is discharged at a constant current value for a set time, and the battery operating parameters are obtained according to a preset sampling period; S2. Determine the difference between the reference operating parameters of the battery and the actual operating parameters of the battery within the set time; The battery reference operating parameters are the battery operating parameters obtained according to the sampling period within the set time at the beginning of the capacity check when the full capacity check is performed according to the preset current value before the battery is put into operation; S3. Estimate the battery health status according to the difference obtained in S2.

2. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 1, characterized in that: The battery operating parameters include at least one of a single cell voltage, a single cell internal resistance and a single cell pole temperature of the battery.

3. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 1, characterized in that: The method further includes: S4, executing S1 to S3 in a loop according to a preset shallow core capacity cycle.

4. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 3, characterized in that: In S3, the battery health condition is obtained according to the battery health degree, and the battery health degree calculation formula is:

5. Among them, SOH ( i ) is the i The health of each battery cell; Er m ( i ) is the i The first battery cell m The actual operating parameters of the battery i The first battery cell m The difference between the reference operating parameters of the batteries; a 1. a 2. … a m They are m The coefficient of the battery operating parameters, M is the number of battery operating parameters.

6. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 4, characterized in that: The method further includes: performing a full capacity core capacity discharge test according to a preset full capacity core capacity cycle; the full capacity core capacity cycle is greater than the shallow core capacity cycle; Obtaining a first health degree according to the battery operating parameters within the set time of the full-capacity nuclear capacity discharge test as the actual battery operating parameters and the battery health degree calculation formula; The second health degree is obtained according to the nominal capacity and the actual capacity of the battery obtained by the nuclear capacity discharge test; the nominal capacity is: the battery capacity obtained by performing a full capacity nuclear capacity discharge test on the battery before the DC power supply system is put into operation; If the error between the first health level and the second health level exceeds the error threshold, the battery operating parameter correction coefficient is calculated based on the second health level and the battery operating parameter correction coefficient within the set time of the full capacity discharge test. a 1. a 2. … a m .

7. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 4, characterized in that: a 1. a 2. … a m The initial value of is obtained by conducting a full-capacity nuclear capacity discharge test on batteries of the same model.

8. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 1, characterized in that: The preset current value is 0.1C 10 , C 10 is the rated capacity of the battery.

9. The method for estimating the health status of a lead-acid battery in a DC power supply system according to claim 4, characterized in that: The battery health is divided into different levels according to the battery health.

10. A device for estimating the health status of a lead-acid battery in a DC power supply system, comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the method for estimating the health status of a lead-acid battery in a DC power supply system as described in any one of claims 1 to 8.

11. A DC power supply system, comprising a battery, characterized in that: Also includes: Discharge device: When the battery is fully charged, it controls the battery to discharge at a constant current for a set time according to a preset current value; Battery inspection device: obtains actual operating parameters of the battery and sends them to the DC monitoring device; the actual operating parameters of the battery are: when the battery is fully charged, the battery is discharged at a constant current value for a set time, and the battery operating parameters are obtained according to a preset sampling period; DC monitoring device: determine the difference between the actual operating parameters of the battery and the reference operating parameters of the battery, and estimate the health of the battery based on the difference; the reference operating parameters of the battery are the battery operating parameters obtained according to the sampling period within the set time at the beginning of the capacity verification when the battery is put into operation and the full capacity verification is performed according to the preset current value.

12. The DC power supply system according to claim 10, characterized in that: The battery operating parameters include at least one of a single cell voltage, a single cell internal resistance and a single cell pole temperature of the battery.

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