Battery health assessment method for substation based on short-time discharge characteristics of float charging

Abstract

The application relates to the technical field of battery health assessment, in particular to a substation battery health assessment method based on a short-time discharge feature of a stop-floating charging, which comprises the following steps: controlling a to-be-assessed battery to be switched to a stop-floating charging state, under the premise of maintaining direct-current bus power supply, making the to-be-assessed battery bear basic operation load; applying a transient impact load to the to-be-assessed battery in a basic operation load belt state, obtaining a discharge voltage curve containing a transient impact load before, during and after the occurrence of the transient impact load, and synchronously collecting performance parameters of the to-be-assessed battery; respectively extracting short-time response features representing voltage drop amplitude, voltage recovery amplitude and voltage recovery time, and long-time influence features representing the impact stability of the battery, generating health evaluation indexes, and obtaining the health state of the to-be-assessed battery. The application improves the reliability and scientificity of the substation battery health assessment.

Description

Technical Field

[0001] This application relates to the field of battery health assessment technology, specifically to a substation battery health assessment method based on the short-term discharge characteristics of floating charge interruption. Background Technology

[0002] Valve-regulated sealed batteries in substations typically operate in float charging mode. Existing battery health assessments mainly rely on periodic offline verification capacity tests. However, substation DC systems do not allow batteries to be frequently disconnected from the bus during operation, resulting in long implementation cycles for conventional verification capacity tests and an inability to reflect the internal aging status of the batteries in real time.

[0003] More seriously, substations frequently face instantaneous high-current impact loads generated by the operation of high-voltage circuit breaker opening and closing coils during actual operation. Traditional constant-current capacity testing can only assess the steady-state capacity of batteries, completely ignoring the dynamic internal resistance changes, depolarization recovery capabilities, and performance parameter stability of batteries under instantaneous impact loads. When batteries exhibit early localized degradation, their steady-state capacity may meet the standards, but when encountering instantaneous impacts, they will experience severe nonlinear voltage drops and polarization hysteresis, leading to inaccurate health status assessments and making them highly susceptible to major power grid accidents such as DC bus under sudden operating conditions. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a substation battery health assessment method based on the short-term discharge characteristics of floating charge, in order to solve the existing issues.

[0005] The substation battery health assessment method based on the short-term discharge characteristics of floating charge in this application adopts the following technical solution:

[0006] One embodiment of this application provides a method for health assessment of substation batteries based on short-term discharge characteristics during float charging. The method includes the following steps:

[0007] Control the battery under evaluation to switch to the off-float charging state, so that the battery under evaluation can bear the basic operating load while maintaining the DC bus power supply;

[0008] An instantaneous impact load is applied to the battery under the basic operating load, and the discharge voltage curves are obtained, including those before the instantaneous impact load occurs, during its duration, and after it disappears. The performance parameters of the battery under evaluation are also collected simultaneously.

[0009] Based on the voltage characteristics of the discharge voltage curve at different stages before, during and after the instantaneous impact load occurs, short-time response characteristics representing the voltage drop amplitude, voltage rise amplitude and voltage recovery time are extracted respectively.

[0010] By comparing the fluctuation differences of the performance parameters before and after the instantaneous impact load occurs, long-term impact characteristics characterizing the battery's impact resistance stability are extracted.

[0011] A health evaluation index is generated by combining the short-term response characteristics and the long-term impact characteristics. The health evaluation index is then compared with a health evaluation threshold determined based on a standard health status to obtain the health status of the battery to be evaluated.

[0012] In one embodiment, the discharge voltage curve is divided into a first stage before the occurrence of the instantaneous impact load, a second stage during its duration, and a third stage after its disappearance.

[0013] In one embodiment, the voltage drop is:

[0014] Extract the average voltage value of the first stage and the minimum voltage value of the second stage, and calculate the voltage drop amplitude based on the difference between the average voltage value of the first stage and the minimum voltage value of the second stage.

[0015] In one embodiment, the voltage recovery amplitude is:

[0016] Extract the average voltage value of the third stage, and calculate the voltage recovery magnitude based on the difference between the average voltage value of the third stage and the minimum voltage value of the second stage.

[0017] In one embodiment, the voltage recovery time is:

[0018] The voltage recovery time is calculated based on the time difference between the moment when the discharge voltage in the third stage reaches the preset recovery threshold and the moment when the voltage reaches its minimum value.

[0019] In one embodiment, the process for determining the short-time response characteristics is as follows:

[0020] Determine the ratio of voltage rise to voltage drop, and use the relative proportion of voltage recovery time to the preset maximum recovery time to determine the voltage recovery speed;

[0021] The short-time response characteristics are obtained by integrating the ratio and the voltage recovery speed.

[0022] In one embodiment, the extraction process of the long-term influence features is as follows:

[0023] The first fluctuation characteristic value of each performance parameter in the first stage and the second fluctuation characteristic value in the third stage are extracted respectively.

[0024] For each of the aforementioned performance parameters, determine the fluctuation difference between the first fluctuation characteristic value and the second fluctuation characteristic value;

[0025] The extreme values ​​that represent the most significant fluctuation degradation are extracted from the fluctuation differences corresponding to all the performance parameters mentioned above, and these are used as the long-term impact features.

[0026] In one embodiment, the health evaluation index is a weighted sum of the short-term response characteristics and the long-term impact characteristics.

[0027] In one embodiment, the process of determining the health assessment threshold is as follows:

[0028] A substation battery simulation model with standard health status parameter configuration is established. The basic operating load and the instantaneous impact load are simulated and run multiple times to obtain benchmark test data and generate corresponding benchmark evaluation indicators.

[0029] Statistical calculations are performed on multiple benchmark evaluation indicators obtained from multiple simulation runs, and the statistical results are determined as the health evaluation threshold.

[0030] In one embodiment, the process of obtaining the health status of the battery to be evaluated is as follows:

[0031] When the health evaluation index is lower than the health evaluation threshold, the battery to be evaluated is determined to be in a state of performance degradation; otherwise, the battery to be evaluated is determined to be in a normal health state.

[0032] This application has at least the following beneficial effects:

[0033] This application controls the battery under evaluation to switch to a non-float charging state, allowing it to naturally assume basic operating loads while maintaining DC bus power supply. This control strategy requires no changes to the DC system wiring and does not require the battery pack to be disconnected from the bus. It achieves real online load testing while absolutely ensuring the safety of DC power supply to the grid, significantly reducing operation and maintenance costs and testing risks.

[0034] Secondly, by superimposing a transient impact load on the basic operating load, the instantaneous high-current impact scenario during the opening and closing of a high-voltage circuit breaker is realistically simulated. This can deeply stimulate the polarization effect and ohmic voltage drop inside the battery, thereby exposing the defects in transient impact resistance that are masked in conventional steady-state discharge. The short-term discharge process is divided into three stages: before the impact, during the duration, and after the impact. The voltage drop amplitude, recovery amplitude, and recovery time are extracted. Among them, the drop amplitude directly reflects the dynamic ohmic internal resistance of the battery (impact resistance), while the recovery amplitude and recovery time accurately reflect the dissipation rate of internal concentration polarization (depolarization capability). This solves the problem of inaccurate power supply risk assessment under sudden operating conditions in existing technologies and avoids serious accidents such as bus voltage loss caused by a sudden voltage drop during the impact even though the steady-state capacity meets the standard.

[0035] Furthermore, by comparing the fluctuation differences of performance parameters before and after the impact, long-term impact characteristics are extracted, and the degree of steady-state damage caused by instantaneous high-current impact to the internal structure of the battery is quantified, which greatly improves the early warning capability for the local degradation trend of the battery.

[0036] Finally, the short-time response characteristics reflecting transient response and the long-time influence characteristics reflecting steady-state maintenance are integrated to take into account both short-time stress resistance and long-time disturbance immunity. At the same time, a health evaluation threshold determined based on standard health status is introduced as a benchmark, so that the final health status judgment is based on an objective and comprehensive physical benchmark, which significantly improves the reliability and scientificity of substation battery health assessment. Attached Figure Description

[0037] Figure 1 The flowchart illustrates the steps of the substation battery health assessment method based on short-term discharge characteristics during float charging provided in this application. Detailed Implementation

[0038] The following description, in conjunction with the accompanying drawings, details the specific scheme of the substation battery health assessment method based on the short-term discharge characteristics of the floating charge interruption provided in this application.

[0039] This application provides an embodiment of a substation battery health assessment method based on short-term discharge characteristics during float charging. Specifically, the method is described below. Please refer to [link to relevant documentation]. Figure 1 The method includes the following steps:

[0040] To accurately analyze the health status of the batteries under evaluation in the substation, it is first necessary to switch the batteries to a non-float charging state, ensuring they bear the basic operating load of the substation while maintaining DC bus power supply, and then collect relevant performance parameters and short-time discharge voltage curves. The specific steps are as follows:

[0041] Since the substation's DC system does not allow battery banks to disconnect from the bus during operation, this embodiment adopts a "stop float charging" strategy without altering the on-site DC system wiring architecture. Specifically, the system charger output is disconnected, stopping the system charger's float charging output to the battery. At this time, because the system bus loses the original charger's float charging voltage support, the bus voltage will naturally drop. Based on the system load demand and potential difference, the battery bank to be evaluated will automatically discharge and seamlessly take over the entire substation's DC bus, maintaining the bus voltage at the battery bank's discharge operating voltage level, thus placing it under actual load conditions to bear the substation's basic operating load. This state not only verifies the battery's steady-state load-carrying capacity for recurring loads but also provides the basic physical prerequisite for subsequent application of transient impact disturbances.

[0042] While the battery under evaluation continues to bear the basic operating load, a transient impact load is applied to it. Because the opening and closing coils of the high-voltage circuit breakers in substations generate a transient large current surge, this transient impact causes a sudden change in the battery's dynamic internal resistance and triggers a transient voltage drop. Conventional constant current discharge cannot stimulate this hidden characteristic. Therefore, a simulated load is applied through programmable control to simulate the actual circuit breaker operating conditions. In a preferred embodiment, the simulated load is set to a single pulse current with an amplitude of 100A and a pulse width of 50ms. In practical applications, this can be dynamically adjusted within the range of 80~150A and a pulse width of 30~80ms, depending on the specific circuit breaker coil parameters.

[0043] Before and after the impact, the performance parameters of the battery to be evaluated are collected simultaneously. In this embodiment, current data and internal resistance data are included, and a short-time discharge voltage curve is obtained by high-frequency waveform recording. Because the voltage response is extremely fast due to the instantaneous impact, ordinary sampling rates can easily miss the minimum voltage drop and details of polarization recovery. Therefore, this embodiment uses high-frequency waveform recording (100kHz sampling rate in this embodiment) to obtain the discharge voltage, while simultaneously collecting current and internal resistance data at a higher frequency (500Hz in this embodiment). The sampling time window covers the complete physical cycle before, during, and after the instantaneous impact load. In this embodiment, data is captured for 5 seconds before the impact, 50ms during the impact, and 10 seconds after the impact ends, providing a high-precision data source for subsequent extraction of short-time response features.

[0044] To provide a reliable benchmark for subsequent health assessments, this application pre-establishes a substation battery simulation model with standard health state parameter configurations. In this simulation model, the basic operating load and instantaneous impact load are simulated using the same control logic as described above, and N simulation runs are performed. This obtains sufficient simulation performance parameters and simulation discharge voltage curves under standard health conditions, i.e., benchmark test data, to eliminate random errors and provide benchmark support for subsequent derivation and calculation of absolutely reliable health evaluation thresholds. In this embodiment, N is set to 100, but the implementer can set it as needed.

[0045] During testing of a battery under basic operating loads, a sudden high-current surge (such as simulating a high-voltage circuit breaker operation) can severely disrupt the battery's internal polarization, causing a surge in discharge current. At this time, the electrochemical reaction rate on the electrode surface lags behind, and the migration and diffusion rate of ions in the liquid phase is lower than the reaction consumption rate, resulting in an additional concentration polarization potential near the electrode interface due to changes in electrolyte concentration. Therefore, the discharge voltage will exhibit highly nonlinear characteristics during the surge and its recovery process.

[0046] This nonlinear transient response characteristic is key to accurately assessing the health status of substation batteries. The physical mechanism is as follows: if the battery pack exhibits aging degradation phenomena such as grid corrosion and active material shedding, its ohmic internal resistance and polarization internal resistance will both increase significantly. Since the battery's discharge voltage response is mainly determined by the ohmic voltage drop and polarization effect, when subjected to a sudden large current surge, a degraded battery with high internal resistance will not only experience a larger instantaneous voltage drop (dominated by the ohmic voltage drop), but its depolarization process will also be more difficult and voltage recovery more slow after the surge dissipates (dominated by the polarization effect).

[0047] Based on the above electrochemical mechanism analysis, this embodiment first extracts short-term response characteristics characterizing the impact resistance by measuring the voltage characteristics of the discharge voltage curve at different stages before, during, and after the instantaneous impact load occurs; secondly, it extracts long-term impact characteristics characterizing the battery's impact resistance stability by comparing the fluctuation differences of performance parameters before and after the instantaneous impact load occurs; finally, it combines these two characteristics to generate the final health evaluation index.

[0048] To accurately extract the above features, the acquired short-time discharge voltage curve needs to be reasonably divided into stages based on the physical process of the instantaneous impact event. In a preferred embodiment, considering the influence of the instantaneous impact on the discharge voltage, the complete short-time discharge voltage curve is divided into three characteristic stages according to the physical time sequence: Stage 1: The stage before the instantaneous impact load occurs (in this embodiment, the 5-second window before the impact occurs). During this stage, the discharge voltage exhibits the normal steady-state change under the basic DC load, and this segment of the discharge voltage sequence is denoted as L(a1). Stage 2: During the duration of the instantaneous impact load (i.e., the extremely short time window of pulse current injection, which is the 50ms mentioned above in this embodiment). During this stage, the normal steady state is broken, and the voltage experiences a sharp nonlinear drop, and this segment of the discharge voltage sequence is denoted as L(a2). Stage 3: The stage after the instantaneous impact load disappears (in this embodiment, the 10-second window after the impact ends). During this stage, the battery is in the depolarization recovery process, and the discharge voltage gradually recovers due to the combined effects of the basic operating load and the impact disturbance it just experienced, and this segment of the discharge voltage sequence is denoted as L(a3).

[0049] Based on the three physical stages described above, this embodiment sequentially extracts feature terms characterizing the voltage drop amplitude, voltage rise amplitude, and voltage recovery time. The specific process is as follows:

[0050] First, the key voltage characteristic points of each stage are obtained. The average value of all discharge voltages in the first stage L(a1) is taken as the first reference voltage, denoted as... Since the instantaneous impact occurs in the second stage L(a2), the minimum voltage value (lowest point) of the discharge voltage during this period is taken as . The average value of all discharge voltages in the third stage L(a3) is taken as the second reference voltage, denoted as... .

[0051] Secondly, the voltage sag and voltage recovery are calculated. The voltage sag is determined based on the difference between the first reference voltage and the minimum voltage. The calculation formula is as follows: ,in, This indicates the rated discharge voltage obtained from the battery monitoring system. The larger the value, the greater the dynamic internal resistance or polarization internal resistance of the battery pack when subjected to instantaneous impact, the weaker its resistance to high current impact, and the worse its health condition.

[0052] Accordingly, the voltage recovery amplitude is determined based on the difference between the second reference voltage and the minimum voltage. The calculation formula is as follows: . The larger the value, the stronger the battery's ability to recover its discharge voltage after an impact, the faster the internal electrochemical polarization and concentration polarization dissipate, and the better its health status.

[0053] Next, calculate the voltage recovery time. After an instantaneous impact load is applied, the discharge voltage will gradually recover to its normal steady state. If the battery is in poor health, the depolarization process is slow, and the recovery time will be significantly prolonged. To reliably assess this time, record the aforementioned voltage minimum value. The corresponding time is the minimum time. Meanwhile, the voltage recovery threshold is set based on the first reference voltage. ,in, The scaling factor has a value range of [0.85, 1), and is preferably 0.95 in this embodiment. It is used to prevent the voltage from never reaching the original steady-state value due to irreversible voltage drop.

[0054] Within the recovery window of the third stage L(a3), the discharge voltage is continuously monitored: if the discharge voltage reaches the voltage recovery threshold, the moment it is first reached is recorded as the recovery moment. Specifically, when the battery is severely degraded, if the discharge voltage has not recovered to the voltage recovery threshold by the end of the third stage L(a3), then the end time of the third stage L(a3) will be forcibly recorded as the recovery time. Furthermore, if the minimum voltage recorded in the second stage... If the voltage recovery threshold is greater than or equal to the specified value, then the minimum value time is directly set. Recorded as recovery time .

[0055] Subsequently, the dimensionless voltage recovery time is calculated based on the time difference between the recovery time and the minimum time. The relation is: .in, This represents the preset maximum recovery observation time span, which corresponds to the L(a3) window duration in this embodiment. The larger the value, the higher the proportion of the voltage recovery time to the entire recovery window, indicating severe internal polarization of the battery, weak depolarization ability, and poorer health status.

[0056] Finally, short-time response features are constructed comprehensively. (The above...) Reflects impact resistance, Reflects the strength of recovery. This reflects the recovery speed. The ratio of voltage rise to voltage drop is calculated, and the voltage recovery speed is determined using the relative proportion of the voltage recovery time to the preset maximum recovery time. The ratio and the voltage recovery speed are integrated to construct a short-time response characteristic that comprehensively characterizes the dynamic response capability of the battery. The specific expression is as follows: , where max[] represents the function that takes the maximum value.

[0057] In the above formula, the molecules in This term reflects the degree to which the terminal voltage recovers to its pre-drop level; This factor reflects the speed of voltage recovery. By using a weighted average of both factors, any disadvantage—such as a large voltage drop, difficulty in recovery, or slow recovery—will lead to... reduce. The larger the value, the stronger the battery's depolarization capability, the lower its dynamic internal resistance, and the better its short-time dynamic response capability.

[0058] It should be noted that if the following occurs A value of 0 indicates that the battery has extremely high tolerance and has not experienced a drop voltage. Therefore, it can be directly set to... The result of the term is a constant 1.

[0059] Theoretically, if a battery is in a healthy state, its ability to resist impact disturbances is strong, and the steady-state characteristics of its performance parameters before and after the impact should not show drastic differences. Therefore, this embodiment compares the fluctuation differences of various performance parameters before and after the instantaneous impact load occurs, and extracts long-term impact characteristics that characterize the battery's impact resistance stability. .

[0060] In practice, the performance parameters are defined as the current and internal resistance data collected synchronously as described above. Taking the current data as an example: the current data sequences L(a1,r) and L(a3,r) are extracted before the instantaneous impact load occurs (first stage) and after it disappears (third stage), respectively; the range of the two sequences is calculated as the first fluctuation characteristic value of the first stage. and the second fluctuation characteristic value of the third stage Based on the first and second fluctuation characteristic values, the fluctuation difference of the current data is calculated. The formula is: It should be noted that if A value of 0 indicates that this performance parameter of the battery was absolutely stable before and after the impact, meaning the impact did not cause any additional fluctuations or degradation. This directly reduces the fluctuation difference. It is 0.

[0061] In another embodiment, the first fluctuation characteristic value of the first stage and the second fluctuation characteristic value of the third stage Variance can also be used for calculation.

[0062] The larger the value, the more severe the degradation of data stability before and after the impact. Correspondingly, the fluctuation difference corresponding to the internal resistance data is calculated. From the fluctuation differences corresponding to current and internal resistance, the extreme value (i.e., the maximum value) that represents the most significant degradation is extracted as the long-term impact feature. . The larger the value, the more severe the impact, indicating that at least one key performance dimension of the battery has experienced violent fluctuations, suggesting a serious local defect and a poorer overall health condition.

[0063] Because the transient impact loads that substation batteries experience in actual operation are characterized by large amplitude and short duration, health degradation is reflected in both transient response and steady-state maintenance. Reflecting transient dynamic internal resistance and depolarization capability, This reflects the long-term resilience to disturbances in a steady-state state. Therefore, the final health assessment index is generated by combining both factors. , ,in, and The preset weighting coefficients, and Considering that the instantaneous impact of large currents during the opening and closing of high-voltage circuit breakers is more representative of the assessment of short-time dynamic response capability, therefore, it is assigned... A higher feature weight is preferred in this embodiment. , Using a weighted summation method can effectively avoid the unintended offsetting or masking of indicators.

[0064] Health evaluation indicators The larger the value, the stronger the battery's depolarization capability, the higher its dynamic internal resistance, and the stronger its performance parameter resistance to disturbances, indicating a better overall health status.

[0065] This application aims to conduct online, safe, and rapid health assessments of substation batteries when they cannot be disconnected from the busbar. Therefore, a benchmark reference needs to be established. To this end, based on a substation battery simulation model with standard health state parameter configurations, benchmark test data is obtained under simulated operating conditions with equal basic operating loads and instantaneous high-current impact loads. For multiple sets of benchmark test data obtained from multiple simulation runs, the benchmark short-time response characteristics and benchmark long-time impact characteristics of each set are extracted, and corresponding benchmark evaluation indicators are generated. Subsequently, statistical calculations are performed on these N sets of benchmark evaluation indicators; in this embodiment, the arithmetic mean is calculated, and the final statistical result is determined as the health assessment threshold.

[0066] When conducting online evaluations of batteries under assessment in substations at actual sites, the aforementioned stop-float charging control strategy is used to simulate the instantaneous high-current impact load of a high-voltage circuit breaker operation while maintaining the basic operating load. Simultaneously, the actual performance parameters and short-time discharge voltage curve of the battery are acquired, and the actual short-time response characteristics and long-time impact characteristics are extracted to calculate the measured health evaluation indicators of the battery under assessment.

[0067] Finally, the degree of deviation of the measured health evaluation index from the health evaluation threshold is determined, and the performance degradation level of the battery under evaluation is judged based on the degree of deviation. Specifically: when the measured health evaluation index is lower than the health evaluation threshold, it indicates that the battery's shock resistance or steady-state retention capability is substandard, and the battery under evaluation is judged to be in a state of performance degradation, requiring maintenance personnel to perform targeted maintenance or replacement as a warning; when the measured health evaluation index is not lower than the health evaluation threshold, it indicates that the battery's internal resistance and depolarization capability have reached the health baseline, and the battery under evaluation is judged to be in a normal healthy state.

Claims

1. A method for assessing the health of substation batteries based on the characteristics of short-term discharge during floating charging, characterized in that, The method includes the following steps: Control the battery under evaluation to switch to the off-float charging state, so that the battery under evaluation can bear the basic operating load while maintaining the DC bus power supply; An instantaneous impact load is applied to the battery under the basic operating load, and the discharge voltage curves are obtained, including those before the instantaneous impact load occurs, during its duration, and after it disappears. The performance parameters of the battery under evaluation are also collected simultaneously. Based on the voltage characteristics of the discharge voltage curve at different stages before, during and after the instantaneous impact load occurs, short-time response characteristics representing the voltage drop amplitude, voltage rise amplitude and voltage recovery time are extracted respectively. By comparing the fluctuation differences of the performance parameters before and after the instantaneous impact load occurs, long-term impact characteristics characterizing the battery's impact resistance stability are extracted. A health evaluation index is generated by combining the short-term response characteristics and the long-term impact characteristics. The health evaluation index is then compared with a health evaluation threshold determined based on a standard health status to obtain the health status of the battery to be evaluated.

2. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 1, characterized in that, The discharge voltage curve is divided into a first stage before the instantaneous impact load occurs, a second stage during its duration, and a third stage after it disappears.

3. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 2, characterized in that, The voltage drop is: Extract the average voltage value of the first stage and the minimum voltage value of the second stage, and calculate the voltage drop amplitude based on the difference between the average voltage value of the first stage and the minimum voltage value of the second stage.

4. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 3, characterized in that, The voltage recovery amplitude is: Extract the average voltage value of the third stage, and calculate the voltage recovery magnitude based on the difference between the average voltage value of the third stage and the minimum voltage value of the second stage.

5. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 4, characterized in that, The voltage recovery time is: The voltage recovery time is calculated based on the time difference between the moment when the discharge voltage in the third stage reaches the preset recovery threshold and the moment when the voltage reaches its minimum value.

6. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 1, characterized in that, The process for determining the short-time response characteristics is as follows: Determine the ratio of voltage rise to voltage drop, and use the relative proportion of voltage recovery time to the preset maximum recovery time to determine the voltage recovery speed; The short-time response characteristics are obtained by integrating the ratio and the voltage recovery speed.

7. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 2, characterized in that, The extraction process of the long-term influence features is as follows: The first fluctuation characteristic value of each performance parameter in the first stage and the second fluctuation characteristic value in the third stage are extracted respectively. For each of the aforementioned performance parameters, determine the fluctuation difference between the first fluctuation characteristic value and the second fluctuation characteristic value; The extreme values ​​that represent the most significant fluctuation degradation are extracted from the fluctuation differences corresponding to all the performance parameters mentioned above, and these are used as the long-term impact features.

8. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 1, characterized in that, The health evaluation index is the weighted sum of the short-term response characteristics and the long-term impact characteristics.

9. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 1, characterized in that, The process for determining the health assessment threshold is as follows: A substation battery simulation model with standard health status parameter configuration is established. The basic operating load and the instantaneous impact load are simulated and run multiple times to obtain benchmark test data and generate corresponding benchmark evaluation indicators. Statistical calculations are performed on multiple benchmark evaluation indicators obtained from multiple simulation runs, and the statistical results are determined as the health evaluation threshold.

10. The substation battery health assessment method based on short-term discharge characteristics during float charging as described in claim 1, characterized in that, The process for obtaining the health status of the battery to be evaluated is as follows: When the health evaluation index is lower than the health evaluation threshold, the battery to be evaluated is determined to be in a state of performance degradation; otherwise, the battery to be evaluated is determined to be in a normal health state.

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