A method and system for detecting the health status of batteries used in a DC system of a substation

Abstract

The present invention provides a method and system for detecting the health status of batteries used in a DC system of a substation. The method comprises acquiring first status data including the battery pack's access switch status, the closing switch status between DC buses, the battery pack's voltage increment status, and the battery pack's current increment status; determining the battery's operating condition based on the first status data; collecting operating data including the battery's boost rate, charge increment, charging duration, and discharge duration based on the operating condition; calculating a health characteristic value HF of the battery under the corresponding operating condition based on the operating data; acquiring second status data including the battery's voltage V, internal resistance R, temperature T, and health characteristic value HF; and generating a state of health (SOH) value diagnostic model based on the second status data for determining the battery's health status. The present invention can determine the battery's health status from multiple perspectives based on the operating condition of the battery in the DC circuit, thereby improving the accuracy of battery health status detection.

Description

Technical Field

[0001] The present invention relates to the technical field of battery health status detection, and in particular to a method and system for detecting the health status of a battery for a DC system of a substation. Background Art

[0002] Substations are the central nerve cells of the power grid, and their safe and stable operation is closely linked to them. The substation's DC system is crucial for providing power to protection, automation, control, and signaling systems. A failure in the substation's DC system could cause the substation's relay protection and automation devices to lose power, preventing circuit breakers from tripping and isolating the fault. This could lead to a series of dangerous consequences, including over-tripping of upstream power sources and even grid disconnection. As the core power supply device of a substation's DC system, the healthy operation of batteries is crucial to ensuring the safety and reliability of the power grid.

[0003] Due to long-term online operation, batteries inevitably experience defects such as aging, plate bridge disconnection, chemical deposition, and sulfation. Due to the inherent characteristics of batteries, their failures often exhibit a "cliff-like" pattern: a battery operating with defects can suddenly experience a disconnection (open circuit) in the positive and negative electrodes. Substation battery packs consist of multiple lead-acid (lithium iron phosphate) batteries connected in series. A single disconnect in any cell can cause the voltage of the entire pack to drop to zero, leading to failure of the substation's DC system and potentially posing a significant threat to grid operations. Therefore, defect monitoring, early warning, and troubleshooting measures for substation batteries are crucial. Summary of the Invention

[0004] In view of this, the problem to be solved by the present invention is to provide a health status detection method and system for batteries used in a substation DC system, which can judge the health status of the battery from multiple angles in combination with operating conditions, thereby improving the accuracy of battery health status detection.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method and system for detecting the health status of batteries for a substation DC system includes a plurality of DC circuits for providing DC power to the substation DC system. The DC circuits include chargers connected to corresponding DC busbars. The output terminals of the chargers are connected in parallel to a battery pack, which is composed of a plurality of batteries connected in series.

[0007] Determine the battery operating condition, obtain first state data including the access switch state of the battery pack, the closing switch state between the DC buses, the voltage increment state of the battery pack, and the current increment state of the battery pack, and determine the operating condition of the battery based on the first state data;

[0008] Calculate the battery State of Health (SOH) value, collect operating data including the battery boost rate, charge increment, charging time, and discharge time based on the operating conditions, calculate the battery's health characteristic value HF under the corresponding operating conditions based on the operating data, obtain second-state data including the battery voltage V, internal resistance R, temperature T, and health characteristic value HF, and the SOH value diagnostic model generates an SOH value for determining the battery's state of health based on the second-state data.

[0009] Furthermore, the operating conditions include static power supply A in which the charger supplies power normally and the battery pack operates stably, AC failure B in which the charger fails and the battery pack discharges, AC recovery C in which the charger resumes power supply and the battery pack charges, core capacity discharge D in which the charger supplies power normally and the battery pack exits operation and is in a test state, and core capacity charging E in which the charger supplies power normally and the battery pack is reconnected and charged.

[0010] Furthermore, determining the operating condition of the battery pack includes: data collection, obtaining current status data of the battery pack;

[0011] Condition matching: Match the status data with the corresponding status data of static power supply A, AC failure B, AC recovery C, core capacity discharge D, and core capacity charging E. If a match is successful with any of them, the operating condition of successful matching is output; if all the matches fail, the operating condition of abnormal power supply F is output and jump to the data collection step.

[0012] Furthermore, the health characteristic value of the battery under the static power supply A The calculation formula is:

[0013] ,

[0014] Among them, t （n）charge Indicates the total charging time of the nth battery when the float charge voltage of the battery pack increases by x, t （n）discharge It indicates the total discharge time of the nth battery when the float charge voltage of the battery pack drops by x, where x is a non-negative value.

[0015] Furthermore, the health characteristic value of the battery under AC failure B The calculation formula is:

[0016] ,

[0017] Among them, Δt represents the sampling time interval, Δu （n） Indicates the change in voltage drop of the nth battery within the Δt interval;

[0018] The health characteristic value of the battery under AC recovery C The calculation formula is:

[0019] ,

[0020] ,

[0021] ,

[0022] ,

[0023] Among them, t sum Indicates the total duration of AC recovery, t CI Indicates the duration of the constant current phase, t CV Indicates the duration of the constant voltage stage, Q0 is the nominal capacity of the battery, U m is the float charge voltage reference value of the battery, u （n） is the voltage of the nth battery, N is the number of batteries in the battery pack, v1 is the battery voltage at the start of charging, and v2 is the battery voltage at the end of charging.

[0024] Furthermore, the health characteristic value of the battery under the core capacity discharge D and core capacity charge E 、 The calculation formula is:

[0025] ,

[0026] ,

[0027] Among them, T （n）discharge Indicates the discharge time of the nth battery, T （n）charge Indicates the charging time of the nth battery.

[0028] Furthermore, the SOH value diagnostic model is constructed based on a Gaussian process regression algorithm and corresponds one-to-one to the operating conditions.

[0029] A power supply protection system for batteries used in a DC system of a substation includes a power supply unit that outputs DC power, a diagnostic unit that determines whether the battery in the power supply unit is below a SOH threshold, a protection unit that removes batteries below the SOH threshold from the circuit, and an early warning unit that indicates the location of defective batteries below the SOH threshold.

[0030] The power supply unit includes a plurality of DC circuits for outputting DC power; the diagnostic unit includes a working condition module for detecting the working status of the battery pack, and a diagnostic module for calculating the SOH value of each battery in the battery pack and judging whether it is lower than the SOH threshold.

[0031] Furthermore, the DC circuit includes a first circuit and a second circuit with identical circuit structures, the first circuit includes a first charger and a first battery pack, the first charger and the first battery pack are connected to one end of a third switch via a first switch and a second switch, respectively, and the other end of the third switch is connected to the first DC bus;

[0032] The second circuit includes a second charger, a second battery pack, a fourth switch, a fifth switch and a sixth switch. The output end of the second circuit is connected to the second DC bus. The seventh switch is connected in series between the first DC bus and the second DC bus.

[0033] Furthermore, the protection unit includes an isolation circuit for removing the battery, and the isolation circuit includes a plurality of relay switches corresponding one to one with the batteries, the positive pin of the relay switch is connected to the positive pole of the battery, and the negative pin of the relay switch is connected to the negative pole of the battery.

[0034] The advantages and positive effects of the present invention are:

[0035] By determining the operating characteristics of the battery pack, corresponding first state data is collected based on the operating characteristics, and then the health characteristic value HF of the battery in the battery pack is calculated. The state of health value diagnostic model corresponding to the operating characteristics generates the SOH value based on the battery voltage V, internal resistance R, temperature T and health characteristic value HF. The battery's SOH value is used to determine whether the battery has defects. The above method can judge the health status of the battery from multiple angles based on the operating conditions, thereby improving the accuracy of battery health status detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0037] Figure 1 This is a flow chart of a method for detecting the health status of a battery for a DC system of a substation according to the present invention;

[0038] Figure 2 This is a schematic diagram of calculating the battery health characteristic value HF in a health status detection method for a battery used in a DC system of a substation according to the present invention;

[0039] Figure 3 This is a schematic diagram of calculating an estimated SOH value within a health status detection method for a battery used in a DC system of a substation according to the present invention;

[0040] Figure 4 This is a system diagram of a power supply protection system for a battery used in a DC system of a substation according to the present invention;

[0041] Figure 5 This is a DC circuit diagram of a power supply protection system for a battery used in a DC system of a substation according to the present invention;

[0042] Figure 6 The present invention discloses an isolation circuit diagram within a power supply protection system of a battery for a DC system of a transformer substation. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] The present invention provides a method for detecting the health status of batteries used in a DC system of a substation. Figure 5 As shown, the DC circuit includes a DC circuit that supplies power to the substation DC system. The DC circuit includes a charger that converts 220V AC power from the power grid into 220V DC power, and a battery pack composed of several batteries connected in series. The output of the charger is connected to a DC bus, which is also connected in parallel to the battery pack. The substation DC system is equipped with several DC buses that transmit DC power, each of which is individually connected to a corresponding power-consuming device. One embodiment of the present application is as follows: the substation DC system is equipped with two DC buses, namely a first DC bus and a second DC bus, which correspond to a first circuit and a second circuit for outputting DC power, respectively.

[0046] In one embodiment of the present application, a first DC bus corresponds to a first circuit. When the first circuit is operating, a charger converts AC power from the grid into DC power, which is then used to power the first DC bus, with the battery pack serving as a backup power source. In the event of a grid failure, the charger fails, and the battery pack powers the first DC bus.

[0047] like Figure 1 and Figure 2The health status detection method shown includes: determining the battery operating condition, obtaining first status data including the access switch status of the battery pack, the closing switch status between the DC buses, the voltage increment status of the battery pack, and the current increment status of the battery pack, and determining the operating condition of the battery based on the first status data.

[0048] The connection switch status includes Pos1 = 0 or 1: when the battery pack is connected, Pos1 = 1; when the battery pack is not connected, Pos1 = 0. The loop-closing switch status includes Pos2 = 0 or 1: when the connection switch between the two DC buses is closed, Pos2 = 1; when the connection switch between the two DC buses is open, Pos2 = 0. The voltage increment status includes State_Voltage = -1, 0, or 1: when the battery pack is charging, the voltage increment is positive, State_Voltage = 1; when the battery pack is stabilizing or serving as a backup power source, the voltage increment is zero, State_Voltage = 0; when the battery pack is discharging, the voltage increment is negative, State_Voltage = -1. The current increment states include State_Current=-1, 0, and 1: when the battery pack is charging, the current flows from the charger to the battery pack, State_Current=1; when the battery pack is discharging, the current flows from the battery pack to the DC bus, State_Current=-1; when the battery pack is isolated, no current flows between the battery pack and the charger (or DC bus), State_Current=0.

[0049] The operating conditions include static power supply A, AC failure B, AC recovery C, core capacity discharge D and core capacity charging E. Different operating conditions correspond to different first state data. The operating condition of the battery pack in the DC circuit is determined by matching the first state data.

[0050] When the DC circuit is in static power supply A, the charger outputs current normally, and the battery pack is used for voltage stabilization or as a backup power supply. The first state data is:

[0051] ,

[0052] When the DC circuit is in AC failure B, the AC input of the charger is abnormal, causing the charger to be unable to output and the battery pack to discharge. The first state data is:

[0053] ,

[0054] When the DC circuit is in AC recovery C, the charger outputs DC power normally and the battery pack is charged. The first state data is:

[0055] ,

[0056] When the DC circuit is in the core capacity discharge D, the charger outputs DC power normally, the battery pack is not connected to the DC circuit, and performs constant current discharge alone (the battery pack discharges constant current to the load in the substation DC system). The first state data is:

[0057] ,

[0058] When the DC circuit is in core capacity charging E, the charger outputs DC power normally, and the battery pack is connected to the DC circuit and charged. The first state data is:

[0059] ,

[0060] Determining the battery pack's operating condition includes: data collection, obtaining the battery pack's current first-state data; and operating condition matching, matching the first-state data with the first-state data corresponding to static power supply A, AC failure B, AC recovery C, core capacity discharge D, and core capacity charge E. If a match is successful, the successfully matched operating condition is output. If all matches fail, the abnormal power supply F operating condition is output. Abnormal power supply F indicates that the charger or battery is currently operating abnormally, requiring the data collection step to be repeated until the battery's current operating condition is determined.

[0061] Calculate the battery State of Health (SOH) value, collect operating data including the battery boost rate, charge increment, charging time, and discharging time based on the operating conditions, calculate the battery's health characteristic value HF under the corresponding operating conditions based on the operating data, obtain second state data including the battery voltage V, internal resistance R, temperature T, and health characteristic value HF, and the SOH value diagnostic model generates an SOH value for determining the battery's state of health based on the second state data.

[0062] During static power supply A, based on existing experience, the time required for battery charging / discharging to increase / decrease the voltage by a fixed amount is significantly correlated with the battery SOH value. Therefore, the operating data includes the total charging time and the total discharging time of the battery, and the battery health characteristic value HF can be calculated. The operation data collection process is: adjust the floating charge voltage setting value of the charger (the charging voltage of the battery pack) up and down, and the voltage value of the charging voltage increase and decrease is x, so that the battery pack performs short-term charging and discharging. Health characteristic value during static power supply The calculation formula is:

[0063] ,

[0064] Among them, t （n）charge It indicates the total charging time of the nth battery when the charging voltage of the charger increases by x, t （n）discharge It represents the total discharge time of the nth battery when the charging voltage of the charger decreases by x, where x represents a non-negative value.

[0065] During AC failure B, after the AC system loses voltage (after the grid cannot provide AC power to the charger), the battery pack discharges at a constant current equal to the charger output current during static power supply A. The battery pack voltage starts to drop from the static float charge voltage. Due to the uncertainty of the grid failure time, the discharge process time is difficult to measure. At the same discharge time interval, the higher the battery health, the smaller the battery voltage drop. Therefore, the operating data includes the battery voltage drop rate. The collection process is: collect the battery voltage change value at fixed intervals. Health characteristic value during AC failure The calculation formula is:

[0066] ,

[0067] Among them, Δt represents the sampling time interval, Δu （n） This value represents the change in voltage drop of the nth battery cell over the interval Δt. Δt is set based on user experience. To ensure the accuracy of the characteristic indicator, a fixed duration of Δt, such as 15 minutes, is recommended.

[0068] At AC recovery C, after the grid AC fault is restored, the charger recharges the battery pack. Since the remaining power in the battery pack varies depending on the duration of the grid fault, the charging method of the battery pack may be constant current first and then constant voltage, or constant voltage throughout the charging process.

[0069] During constant current charging, the larger the area of ​​the differential curve between the battery charge and the battery voltage, the better the battery's storage performance, and therefore the larger the battery's SOH value; during constant voltage charging, the closer the battery's charging voltage is to the equalizing charging voltage of the battery pack, the larger the battery's SOH value.

[0070] However, in actual situations, if the AC failure time B is short and the battery power loss is low, there is no constant current charging stage. Therefore, in order to more accurately generate the battery SOH value, the operating data includes the constant current charging time, constant voltage charging time and total charging time, and the health characteristic value when AC is restored C The calculation formula is:

[0071] ,

[0072] , , ,

[0073] Where: t sum Indicates the total duration of AC recovery, t CI Indicates the constant current charging time, t CV Indicates the constant voltage charging time. Q0 is the nominal capacity of the battery, U m is the float charge voltage reference value of the battery, u（n） is the voltage of the nth battery, N is the number of batteries in the battery pack, v1 is the battery voltage at the start of charging, and v2 is the battery voltage at the end of charging.

[0074] During the core capacity discharge D, the battery pack is disconnected from the DC circuit and a separate discharge test is performed (i.e., the battery pack is connected to the tester). During the test, the battery pack is discharged from the float charge voltage to the cut-off voltage at a constant current. The longer the battery discharge time, the higher the SOH value. Therefore, the discharge time of each battery is collected separately. The calculation formula is:

[0075] ,

[0076] Among them, T （n）discharge Indicates the discharge time of the nth battery.

[0077] During core capacity charging (E), after verifying that the voltage of each battery in the battery pack is normal, the battery pack is reconnected to the DC circuit. The charger charges the battery pack, and the voltage of all batteries in the battery pack rises to the float charge voltage. The shorter the battery charging time, the higher the SOH value. Therefore, the charging time of each battery is collected separately. Health characteristic value during core capacity charging The calculation formula is:

[0078] ,

[0079] Among them, T （n）charge Indicates the charging time of the nth battery.

[0080] To improve the accuracy of SOH calculation, the state quantities Pos1, Pos2, State_Voltage, and State_Current are continuously detected to determine whether there are any changes in the state quantities. If not, the second state data sampling time is adjusted according to the current operating conditions to continuously update the battery's SOH value. If yes, the first state data is immediately collected to update the operating conditions, and the second state data is collected according to the operating conditions to update the battery's SOH value.

[0081] An embodiment of the present application is: operating condition A is the long-term state of the actual operation of the substation DC system, and the second state data is collected once every 1 hour; in operating condition B, the second state data is collected once every 15 minutes; in operating conditions C, D, and E, the second state data includes the entire process of the operating condition.

[0082] like Figure 3As shown, the input of the SOH value diagnostic model is the second state data, and the output is the SOH value. When training the SOH value diagnostic model, the second state data and corresponding SOH values ​​under different operating conditions are separately collected. Based on the collected data, the SOH value diagnostic model corresponding to the operating condition is separately trained to obtain the SOH value diagnostic model corresponding to the different operating conditions, thereby achieving multi-angle judgment of the battery health status while ensuring the accuracy of the judgment. One embodiment of the present application is to construct an SOH value diagnostic model based on the Gaussian process regression algorithm (GPR), and the SOH value diagnostic models for static power supply A, AC failure B, AC recovery C, core capacity discharge D, and core capacity charging E are model 1, model 2, model 3, model 4, and model 5, respectively.

[0083] When calculating a battery's SOH value, the SOH value diagnostic model corresponding to the operating conditions of the battery pack is retrieved based on the battery's status. The SOH value diagnostic model accepts the second-state data and outputs the battery's SOH value. The second-state data of all batteries in the pack are sequentially input into the SOH value diagnostic model, which then outputs the SOH value of each battery in the pack. Based on the SOH value, any defective batteries in the pack are determined. If any battery's SOH value falls below the SOH threshold, it is promptly removed (and: each SOH value update is accompanied by a health status determination and removal decision).

[0084] A DC battery power supply protection system for a substation, such as Figure 4 As shown, the system comprises a substation system (corresponding to the substation's DC system) and a power supply protection system, which is connected to the substation's DC system via a DC bus. The power supply protection system includes a power supply unit that outputs DC power, a diagnostic unit that determines whether the battery within the power supply unit is defective, a protection unit that removes defective batteries from the circuit, and an early warning unit that indicates the location of defective batteries.

[0085] The power supply unit includes a DC circuit whose output is connected to the DC bus. This circuit supplies power to the substation's DC system through the DC bus. The DC circuit also includes a charger that converts AC power to DC power and a battery pack consisting of several batteries connected in series. The output of the power supply is connected to the DC bus, and the battery pack is connected in parallel to the output of the power supply. When the power supply circuit is operating, the power supply outputs DC power to power the substation's DC system, while the battery pack provides voltage stabilization or serves as a backup power source. In the event of a grid or charger failure, the battery pack provides sole power to the substation's DC system.

[0086] One embodiment of the present application is: Figure 5As shown, the DC circuit includes a first circuit and a second circuit with identical circuit structures. The first circuit includes a first charger and a first battery pack. These are connected to one end of a third switch K3 via a first switch K1 and a second switch K2 (corresponding to the battery pack's access switches), respectively. The other end of the third switch K3 is connected to the first DC bus. When the third switch K3 is closed, the first circuit begins supplying power. During normal operation of the first power supply circuit, the first and second switches K1 and K2 are simultaneously closed. If the grid or the first charger fails, the first switch K1 opens, and if the first battery pack fails, the second switch K2 opens. The second circuit includes a second charger, a second battery pack, a fourth switch K4, a fifth switch K5, and a sixth switch K6. The output of the second circuit is connected to the second DC bus.

[0087] A seventh switch K7 is provided between the first DC bus and the second DC bus. The seventh switch K7 corresponds to a closing switch between the DC buses. Before the battery pack core capacity discharges D, the seventh switch K7 is closed to close the two DC buses, and then the connection between the battery pack and the corresponding DC circuit is disconnected to execute the core capacity discharge D.

[0088] The power supply diagnostic unit includes a working condition module that detects the working status of the battery pack and a diagnostic module that determines whether the health status of each battery in the battery pack meets the threshold. The working condition module determines the operating condition of the battery pack based on the first state data of the battery pack and outputs working condition feedback. The working condition data includes the state of the second switch K2 or the state of the fifth switch K5, the state of the seventh switch K7, the voltage increment data of the battery pack, and the current increment data of the battery pack. The working condition feedback of the battery pack includes: static operation during the charger's independent power supply process, AC failure during the charger's power supply failure process, AC recovery during the charger's power supply recovery process, capacity discharge during the battery capacity verification process, capacity charging during the system connection process after verification is completed, and abnormal operation that does not belong to any of the above processes.

[0089] The diagnostic module receives operating condition feedback, collects the operating data of the battery pack based on the operating condition feedback, and calculates the health characteristic value HF of each battery in the battery pack under the corresponding operating condition based on the operating data. The diagnostic module includes a SOH value diagnostic model corresponding to the operating condition. The SOH value diagnostic model receives the health characteristic value HF, voltage V, internal resistance R, and temperature T of the battery under the corresponding operating condition, outputs the SOH value representing the health status of the battery, and determines whether there is a defect based on the SOH value of each battery.

[0090] The protection unit receives the location information of batteries whose SOH values ​​are lower than the SOH threshold, removes low SOH batteries based on the location information, and feeds back the protection results. Figure 6As shown, the protection unit includes an isolation circuit for removing batteries. The isolation circuit consists of several relay switches corresponding to each battery. The positive pin of each relay switch is connected to the positive terminal of the battery, and the negative pin of the relay switch is connected to the negative terminal of the battery. The isolation circuit operates as follows: based on the position information, the protection unit controls the corresponding relay switch to conduct, short-circuiting the positive and negative terminals of the corresponding battery, thereby isolating the battery.

[0091] like Figure 5 As shown, the power supply output ends of the first battery pack and the second battery pack are respectively provided with a first relay switch km1 and a second relay switch km2 in a normally closed state, and a third relay switch km3 is provided between the first DC bus and the second DC bus. One embodiment of the present application is: when multiple batteries below the SOH threshold in the first battery pack are removed, causing the battery pack voltage to drop significantly, or when the AC power supply fails for a long time, causing the voltage of the first battery pack to fall below the limit safety voltage, the power provided by the first battery pack cannot meet the normal operation of the substation relay protection and automatic devices, the first relay switch km1 is controlled to be disconnected, the third relay switch km3 is controlled to be closed, the first DC bus and the second DC bus are operated in a closed loop, and the second charger and the second battery pack are used to carry the entire substation DC load, which can extend the power supply time and buy time for emergency repairs.

[0092] The warning unit receives the protection result and location information and issues a text warning reminder. In one embodiment of the present application, when a staff member receives a text warning reminder that "the health status of the nth battery in the Nth battery pack is below the threshold and has been shut down," the staff member goes to the location of the nth battery to replace the battery and reconnect the battery to the Nth battery pack.

[0093] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of this patent.

Claims

1. A method for detecting the health status of a battery for a DC system in a substation, characterized in that: The invention comprises a plurality of DC circuits for providing DC power to the DC system of the substation, wherein the DC circuits include chargers connected to corresponding DC buses, the output ends of the chargers are connected in parallel to a battery pack, and the battery pack is composed of a plurality of storage batteries connected in series; Determine the battery operating condition, obtain first state data including the access switch state of the battery pack, the closing switch state between the DC buses, the voltage increment state of the battery pack, and the current increment state of the battery pack, and determine the operating condition of the battery based on the first state data; Calculating the battery state of health (SOH) value, collecting operating data including the battery boost rate, charge increment, charging duration, and discharging duration based on the operating conditions, calculating the battery health characteristic value HF under the corresponding operating conditions based on the operating data, and obtaining second state data including the battery voltage V, internal resistance R, temperature T, and the health characteristic value HF. The SOH value diagnostic model generates an SOH value for determining the battery health state based on the second state data; The operating condition includes the AC recovery C when the charger resumes power supply and charges the battery pack, and the health characteristic value of the battery under the AC recovery C The calculation formula is: ， ， ， ， Among them, t sum Indicates the total duration of the AC recovery process, t CI Indicates the duration of the constant current phase, t CV Indicates the duration of the constant voltage stage, Q0 is the nominal capacity of the battery, U m is the float charge voltage reference value of the battery, u （n） is the voltage of the nth battery, N is the number of batteries in the battery pack, v1 is the battery voltage at the start of charging, and v2 is the battery voltage at the end of charging.

2. The method for detecting the health status of a battery for a DC system of a substation according to claim 1, characterized in that: The operating conditions include static power supply A in which the charger supplies power normally and the battery pack operates stably, AC failure B in which the charger fails and the battery pack discharges, core capacity discharge D in which the charger supplies power normally and the battery pack exits operation and is in a test state, and core capacity charging E in which the charger supplies power normally and the battery pack is reconnected and charged.

3. The method for detecting the health status of a battery for a DC system of a substation according to claim 2, characterized in that: Determining the operating condition of the battery pack includes: data collection, obtaining current first state data of the battery pack; Operating condition matching: Match the first state data with the first state data corresponding to static power supply A, AC failure B, AC recovery C, core capacity discharge D, and core capacity charging E respectively. If a match is successful with any one of them, output the operating condition of successful matching; if all the matches fail, output the operating condition of abnormal power supply F, and jump to the data collection step.

4. The method for detecting the health status of a battery for a DC system of a substation according to claim 2, characterized in that: The health characteristic value of the battery under static power supply A The calculation formula is: ， Among them, t （n）charge Indicates the total charging time of the nth battery when the float charge voltage of the battery pack increases by x, t （n）discharge It indicates the total discharge time of the nth battery when the float charge voltage of the battery pack drops by x, where x is a non-negative value.

5. The method for detecting the health status of a battery for a DC system of a substation according to claim 2, characterized in that: The health characteristic value of the battery under AC failure B The calculation formula is: ， Among them, Δt represents the sampling time interval, Δu （n） It represents the change in the voltage drop of the nth battery within the Δt interval.

6. The method for detecting the health status of a battery for a DC system of a substation according to claim 2, characterized in that: The health characteristic value of the battery under the core capacity discharge D and core capacity charge E 、 The calculation formulas are: ， ， Among them, T （n）discharge Indicates the discharge time of the nth battery, T （n）charge Indicates the charging time of the nth battery.

7. The method for detecting the health status of a battery for a DC system of a substation according to claim 1, characterized in that: The SOH value diagnostic model is constructed based on a Gaussian process regression algorithm and corresponds one-to-one to the operating conditions.

8. A power supply protection system for a battery used in a DC system of a substation, according to a method for detecting the health status of a battery used in a DC system of a substation according to any one of claims 1 to 7, characterized in that: It includes a power supply unit that outputs direct current, a diagnostic unit that determines whether the battery in the power supply unit is below the SOH threshold, a protection unit that removes batteries below the SOH threshold from the battery pack, and an early warning unit that reminds the location of defective batteries below the SOH threshold; The power supply unit includes several DC circuits that output DC power; the diagnostic unit includes an operating condition module that detects the working status of the battery pack, and a diagnostic module that calculates the SOH value of each battery in the battery pack and determines whether it is lower than the SOH threshold.

9. A power supply protection system for a storage battery used in a DC system of a substation according to claim 8, characterized in that: The DC circuit includes a first circuit and a second circuit with identical circuit structures. The first circuit includes a first charger and a first battery pack. The first charger and the first battery pack are connected to one end of a third switch via a first switch and a second switch, respectively. The other end of the third switch is connected to the first DC bus. The second circuit includes a second charger, a second battery pack, a fourth switch, a fifth switch and a sixth switch. The output end of the second circuit is connected to the second DC bus. The seventh switch is connected in series between the first DC bus and the second DC bus.

10. A power supply protection system for a battery used in a DC system of a substation according to claim 8, characterized in that: The protection unit includes an isolation circuit for removing the battery, and the isolation circuit includes a plurality of relay switches corresponding to the batteries one by one, the positive pin of the relay switch is connected to the positive electrode of the battery, and the negative pin of the relay switch is connected to the negative electrode of the battery.

Images