A power battery bms protection system and a protection method thereof

Abstract

This invention relates to the field of circuit emergency protection, specifically to a power battery BMS protection system and method, comprising: during the charging process of the power battery to the load capacitor at the load end through a pre-charge circuit, real-time acquisition of the load voltage at the load end; if the time consumed in the first boost stage when the load voltage increases to a first stage voltage threshold and the time consumed in the second boost stage when the load voltage increases from the first stage voltage threshold to a second stage voltage threshold are detected, then the ratio of the second boost stage time to the first boost stage time is used as the measured time ratio; the measured time ratio is compared with a preset standard resistance-capacitance time ratio to identify whether there is a leakage path in the circuit at the load end; if a leakage path is identified, charging protection measures are executed. This invention provides effective safety protection for the pre-charging process of the load capacitor in the event of leakage.

Description

Technical Field

[0001] This invention relates to the field of circuit emergency protection, specifically to a power battery BMS protection system and its protection method. Background Technology

[0002] As the core energy source for electric vehicles and energy storage power stations, the power battery system is typically equipped with a battery management system (BMS) and a high-voltage relay control circuit. In the initial stage of power-on, to avoid the battery voltage being directly applied to the load capacitor and generating a damaging surge current, a "pre-charge circuit" with a series pre-charge resistor is commonly used for current-limiting startup.

[0003] Traditional BMS systems typically use a "fixed timeout + voltage threshold" strategy to determine the success of pre-charging. However, if a "soft short circuit" (weak leakage current) exists at the load end due to insulation aging or moisture, the leakage current will divert the pre-charging current, causing the voltage to rise slowly but still reach the threshold. During this process, the pre-charging resistor continuously bears high power, easily exceeding its thermal capacity limit and burning out. Although traditional BMS systems are equipped with current sensors, the current during the pre-charging stage is relatively small (several amperes to hundreds of milliamperes), while the sensors are designed to cover the large discharge current and have a large range. This results in insufficient accuracy in the small current range and zero-point drift, making it difficult to accurately distinguish between the capacitor charging current and the weak leakage current. Summary of the Invention

[0004] To address the problem that existing technologies cannot provide effective safety protection for the pre-charging process of the load capacitor when facing leakage current, relying solely on voltage sampling data in the absence of high-precision current detection, this invention provides a power battery BMS protection system and its protection method.

[0005] The present invention provides a power battery BMS protection system and protection method, which adopts the following technical solution: One embodiment of the present invention provides a method for protecting a power battery, the method comprising the following steps: During the process of the power battery charging the load capacitor in the load terminal through the pre-charge circuit, the load voltage of the load terminal is collected in real time. If the time consumed in the first boost phase when the load voltage increases to the first stage voltage threshold and the time consumed in the second boost phase when the load voltage increases from the first stage voltage threshold to the second stage voltage threshold are monitored, then the ratio of the time consumed in the second boost phase to the time consumed in the first boost phase is taken as the measured time ratio. The measured time consumption ratio is compared with the preset standard resistance-capacitance time consumption ratio to identify whether there is a leakage path in the circuit at the load end. If a leakage path is identified, charging protection measures are implemented.

[0006] Preferably, the method further includes: Starting from the closed pre-charge circuit, when the load voltage collected in real time first reaches the first stage voltage threshold at the first time point and remains above the first stage voltage threshold for a preset time after the first time point, and when the load voltage first reaches the second stage voltage threshold at the second time point and remains above the second stage voltage threshold for a preset time after the second time point, it is determined that the first boost stage time when the load voltage increases to the first stage voltage threshold and the second boost stage time when the load voltage increases from the first stage voltage threshold to the second stage voltage threshold are detected. The first time point is taken as the first boost stage time, and the difference between the second time point and the first time point is taken as the second boost stage time.

[0007] Preferably, the specific steps for obtaining the standard resistance-capacitance time ratio are as follows: The time taken for the voltage across the capacitor in any first RC circuit to increase to the first stage voltage threshold is denoted as the first time, and the time taken for the voltage across the capacitor to increase from the first stage voltage threshold to the second stage voltage threshold is denoted as the second time. The ratio of the second time to the first time is used as the standard resistance-capacitance time ratio.

[0008] Preferably, the method further includes: If no leakage path is identified, the load capacitance value is calculated based on the time consumed in the first boost stage. Calculate the cumulative heat generated during the full charging process of the load capacitor based on the load capacitance value; Based on the accumulated heat generation, it is determined whether the current load capacitor has an overcapacity fault. If an overcapacity fault is detected, charging protection measures are implemented.

[0009] Preferably, the method further includes: If no capacity over-limit fault is detected, a dynamic timeout threshold is calculated based on the load capacitance value; and the preset fixed timeout time is updated using the dynamic timeout threshold. Use the updated timeout period for charging timeout protection.

[0010] Preferably, the specific steps for obtaining the dynamic timeout threshold are as follows: The reference time constant is calculated based on the preset pre-charge resistance value and load capacitance value, and then multiplied by a certain factor to serve as the dynamic timeout threshold.

[0011] Preferably, the specific steps for obtaining the load capacitance value are as follows: In the second RC circuit formed by the pre-charge circuit, the load capacitance value is calculated based on the preset pre-charge resistance value and the time consumed in the first boost stage.

[0012] Preferably, the method further includes: if the load voltage is detected to be consistently lower than the second-stage voltage threshold within a preset maximum allowable pre-charging time, then charging protection measures are implemented.

[0013] Preferably, the residual voltage in the load capacitor at the load end is released before charging the load capacitor at the load end through the pre-charge circuit.

[0014] Another embodiment of the present invention provides a power battery BMS protection system, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor runs the computer program, it implements all the steps of the power battery protection method described above.

[0015] The beneficial effects of the technical solution of the present invention are: This invention utilizes the time-emission ratio characteristic to achieve decoupled identification of the load circuit properties, naturally eliminating the interference of capacitance variables and being sensitive only to the nonlinear response introduced by leakage. This allows this embodiment to accurately identify abnormal leakage loads without relying on high-precision, small-range current sensors. The presence of such leakage loads can cause the load capacitor to be continuously charged without being fully charged (e.g., after the charging time exceeds the timeout period, it is still not fully charged or charged to a preset voltage threshold), which in turn causes the pre-charge resistor to continuously heat up and burn out. This invention effectively avoids the risk of resistor burnout caused by leakage by identifying the leakage path and performing charging protection. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating the steps of a power battery protection method according to an embodiment of the present invention. Figure 2 A flowchart illustrating the steps of charging protection based on capacity over-limit faults provided in one embodiment of the present invention; Figure 3 This is a flowchart illustrating the steps of charging protection based on a dynamic timeout threshold, as provided in one embodiment of the present invention. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a power battery BMS protection system and its protection method according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] The following description, in conjunction with the accompanying drawings, details a specific scheme for a power battery BMS protection system and its protection method provided by the present invention.

[0021] Please see Figure 1 The diagram illustrates a flowchart of a power battery protection method according to an embodiment of the present invention, which includes the following steps: Step S101: During the process of the power battery charging the load capacitor in the load terminal through the pre-charge circuit, the load voltage of the load terminal is collected in real time.

[0022] This embodiment charges the load capacitor at the load end by closing a pre-charge circuit, where the pre-charge circuit refers to the circuit formed by the pre-charge resistor and the load end in series. The load capacitor refers to the equivalent capacitance of the entire load end connected in parallel. After closing the pre-charge circuit, the power battery will charge the load capacitor. This charging process is a dynamic process rather than a static process. The pre-charge resistor acts as a current limiter to prevent huge surge currents from damaging the contactor contacts or fuses at the load end.

[0023] The load voltage, which is collected in real time during the charging process, dynamically increases from small to large. The pattern of its change is then used to describe the characteristics of the load circuit at the load end.

[0024] As an example, the power battery refers to a lithium iron phosphate battery with a nominal open-circuit voltage of 12.8 volts, which serves as a backup power source for UPS / EPS; the pre-charge resistor used in this example has a resistance of 150 ohms.

[0025] As an example, a controlled relay is used to close and open the pre-charge circuit.

[0026] As an example, a voltage sensor is connected in parallel to the load terminal to sample the voltage, i.e., the load voltage, at a sampling frequency of 1 kHz.

[0027] Step S102: If the time consumed in the first boost stage when the load voltage increases to the first stage voltage threshold and the time consumed in the second boost stage when the load voltage increases from the first stage voltage threshold to the second stage voltage threshold are detected, then the ratio of the time consumed in the second boost stage to the time consumed in the first boost stage is taken as the measured time ratio.

[0028] The duration of the first boost phase represents the length of time during which the load voltage is in a lower voltage phase (i.e., the load voltage is less than or equal to the first phase voltage threshold) during the dynamic growth of the load voltage. The duration of the second boost phase represents the length of time during which the load voltage is in a higher voltage phase (i.e., the load voltage is between the first phase voltage threshold and the second phase voltage threshold) during the dynamic growth of the load voltage.

[0029] The measured time ratio represents the proportion of time taken for each voltage increase stage during the dynamic growth of the load voltage. It accurately reflects the characteristics of the load circuit at the load end (used to distinguish whether the load circuit has pure capacitive characteristics in subsequent tests). The ratio of the time taken for the second boost stage to the time taken for the first boost stage allows the measured time ratio to automatically offset the common-mode error caused by the change in resistance with temperature.

[0030] Specifically, when the maximum allowable precharge time If the load voltage consistently fails to reach the second-stage voltage threshold, a severe short circuit or leakage fault is detected at the load end, preventing the voltage from rising. In this case, charging protection measures are immediately implemented. In one example, implementing charging protection measures includes disconnecting the pre-charge circuit and reporting fault information, including: "Pre-charge hard fault, short circuit and leakage risk." This fallback mechanism ensures that the system can promptly disconnect the circuit under extreme fault conditions, preventing the protection resistor from burning out. As an example, when the second-stage voltage threshold is set to 50% × At that time, Set to 300 milliseconds; where The initial battery voltage refers to the voltage across the power battery measured by a voltage sensor before the pre-charge circuit is closed (i.e., before charging begins). In some embodiments, a table can be pre-set, containing different values ​​for the second-stage voltage threshold. The corresponding values ​​(i.e., the second-stage voltage threshold and) The key-value pairs are constructed, and the time is obtained based on the second-stage voltage threshold by looking up a table. If the value cannot be found when looking up the table, it is interpolated (e.g., linear interpolation) based on the key-value pairs recorded in the table.

[0031] Specifically, when the load voltage equals within 5 milliseconds When the load capacitor is fully charged in a short time, the pre-charging process ends directly, thus ending this embodiment, without the need to implement charging protection measures.

[0032] Step S103: Compare the measured time consumption ratio with the preset standard resistance-capacitance time consumption ratio to identify whether there is a leakage path in the circuit at the load end. If a leakage path is identified, then execute charging protection measures.

[0033] The standard RC time ratio represents the proportion of time taken for the load voltage to climb one voltage stage for a load circuit that conforms to the characteristics of a pure capacitor (in which case the precharge circuit is regarded as an RC circuit). It is equivalent to the ratio of the time taken for the second boost stage to the time taken for the first boost stage in an RC circuit. It describes the inherent property of any RC circuit and is independent of the parameters of the RC circuit (i.e., the resistance and capacitance in the RC circuit).

[0034] In actual operation, if a parallel leakage resistor (soft short circuit) exists at the load end, the current flowing through the leakage resistor will increase linearly as the voltage increases. This leakage current diverts the current that should be used for capacitor charging, resulting in a slower charging speed. In the lower voltage stage, the load voltage is low, the leakage current is small, and its effect on extending the time of the first boost stage is not significant. In the higher voltage stage, the load voltage is high, the leakage current increases significantly, causing the time of the second boost stage to be greatly extended. Therefore, the presence of leakage current inevitably leads to a significantly greater measured time ratio than the standard RC time.

[0035] In this embodiment, if the measured time consumption ratio is greater than the standard resistance-capacitance time consumption ratio, it is determined that there is a non-negligible parallel leakage path at the load end. At this time, the load circuit is no longer a purely capacitive load (i.e., it does not conform to the characteristics of a pure capacitor), and continued charging will cause the resistor to continue to heat up and cannot be fully charged. At this time, charging protection measures are implemented.

[0036] In one example, performing charging protection measures includes: disconnecting the precharge circuit and reporting fault information, including: "Precharge failed, there is a low insulation resistance or soft short circuit fault".

[0037] Thus, as can be seen from steps S101 to S103, this embodiment utilizes the time consumption ratio characteristic to achieve decoupled identification of the load circuit properties, which naturally eliminates the interference of capacitance variables and is only sensitive to the nonlinear response introduced by leakage. This allows this embodiment to accurately identify abnormal leakage loads without relying on high-precision small-range current sensors. The presence of such leakage loads will cause the load capacitor to be continuously charged without being fully charged (for example, after the charging time exceeds the timeout period, it is still not fully charged or charged to a preset voltage threshold), which in turn causes the pre-charge resistor to continuously heat up and burn out. This embodiment effectively avoids the risk of resistor burnout caused by leakage by identifying the leakage path and performing charging protection.

[0038] Furthermore, such as Figure 2 As shown, in another preferred embodiment, the method further includes: Step S104: If no leakage path is identified, calculate the load capacitance value based on the time consumed in the first boost stage; calculate the cumulative heat generated during the full charging process of the load capacitor based on the load capacitance value; identify whether the current load capacitor has an over-limit capacity fault based on the cumulative heat generated; if an over-limit capacity fault is identified, execute charging protection measures.

[0039] The identification of no leakage path refers to the situation where the measured time ratio is less than or equal to the standard resistance-capacitance time. In this case, the load circuit conforms to the characteristics of a pure capacitor, and is considered to have no leakage fault. The circuit insulation is good, and the pre-charge circuit is regarded as an RC circuit. The linear physical law of the RC circuit can be used to accurately quantify and evaluate the size of the load capacitance, thereby obtaining the capacitance value of the load capacitance, which is simply referred to as the load capacitance value.

[0040] Specifically, the pre-charge circuit is considered as an RC circuit, and the load capacitor and the pre-charge resistor are considered as a resistor and capacitor connected in series in the RC circuit; the time taken for the first boost stage refers to the time it takes for the voltage of the capacitor in the RC circuit to increase to the first stage voltage threshold.

[0041] Furthermore, after knowing the size of the load capacitor, the cumulative heat generation is calculated, which represents the maximum heat released by the pre-charge resistor when the load capacitor is fully charged.

[0042] It should be noted that this embodiment is based on the load capacitor being fully charged (i.e., the load voltage equals...). This is in the case of charging to the pre-charge cutoff voltage (e.g., 96%), rather than charging to the pre-charge cutoff voltage. The calculations are performed under the following conditions to allow for a safety margin. This is because, in actual operating conditions, the load voltage will jump to [a certain value] the instant the main relay is closed after pre-charging. Or, the pre-charge process may result in slight overcharging due to control delays. (Press...) The calculations cover all possible upper limits of heat generation.

[0043] It should be further explained that, according to the principle of capacitor energy storage, during the charging process of an RC circuit, half of the work done by the power source is converted into capacitor energy storage, and the other half is necessarily converted into resistive heat energy. Therefore, the maximum heat released by the pre-charge resistor, that is, the cumulative heat generated, is equal to the energy stored in the load capacitor. : , This represents the load capacitance value; the calculation formula is well-known, and its principle will not be elaborated in this embodiment.

[0044] The identification of a capacity over-limit fault refers to a situation where the cumulative heat generation exceeds the preset resistance thermal capacity limit. In this case, it indicates that the load capacitance is too large (for example, exceeding the maximum load capacity of the hardware design). If charging is forced, the pre-charge resistor will face the risk of overheating and burning out. At this time, charging protection measures need to be implemented.

[0045] In one example, the charging protection measures include: disconnecting the precharge circuit and reporting the fault message "Precharge failed, load capacitance too large".

[0046] It should be noted that the resistance thermal capacity limit is a value specified in the precharge resistor device datasheet, representing the maximum heat generated when the precharge resistor does not suffer serious burn-out risk. In this embodiment, the resistance thermal capacity limit is 800 joules.

[0047] Thus, as can be seen from steps S101 to S104, in a preferred embodiment, the characteristics of the time consumption ratio are used to achieve decoupling identification of the load circuit properties. This naturally eliminates the interference of capacitance variables and is only sensitive to the nonlinear response introduced by leakage. This allows this embodiment to accurately distinguish between "normal large capacitance load" and "abnormal leakage load" without relying on a high-precision small-range current sensor. This embodiment provides circuit protection for these two situations, effectively avoiding the risks of charging due to large capacitance and resistor burnout due to leakage.

[0048] Furthermore, such as Figure 3 As shown, another preferred embodiment includes: Step S105: If no capacity over-limit fault is detected, calculate the dynamic timeout threshold based on the load capacitance value; and use the dynamic timeout threshold to update the preset fixed timeout time and implement charging protection measures.

[0049] The identification of no capacity over-limit fault refers to the situation where the cumulative heat generation is less than or equal to the preset resistance thermal capacity limit. In this case, it means the current load capacitor is safe and can be charged. In existing technology, a fixed timeout period (e.g., 500ms) and a voltage threshold (e.g., ...) are set during charging. (95%), when the pre-charge time (i.e. the time to close the pre-charge circuit) is within the timeout period and the load capacitor is not charged to the voltage threshold, circuit protection (i.e., secondary protection) is required again to further avoid the risk of pre-charge resistor burnout during long-term charging.

[0050] However, a fixed timeout period may not be able to adapt to complex and ever-changing battery charging and discharging scenarios (for example, as the demand for high-power fast charging and long battery life increases, the load capacitance value at the load end will change), causing the circuit protection action to be mistakenly executed due to timeout during charging, thus reducing the pre-charge time.

[0051] In this embodiment, the dynamic timeout threshold is calculated based on the load capacitance value. The dynamic timeout threshold represents the time used to determine whether the charging timeout has occurred when the precharge circuit is regarded as an RC circuit (at this time, the load capacitance and the precharge resistor are the resistor and capacitor in the RC circuit). It is a non-fixed value determined by the load capacitance and the precharge resistor.

[0052] This preferred embodiment uses a dynamic timeout threshold to update a preset fixed timeout period before executing charging protection measures. This allows the circuit protection action to dynamically adapt to complex and varied battery charging and discharging scenarios, enabling pre-charging for as long as possible. The complex and varied battery charging and discharging scenarios affect the size of the dynamic timeout threshold by influencing the load capacitance or pre-charging resistance.

[0053] In one example, the charging protection measures described in this step include: disconnecting the precharge circuit and reporting fault information, including: "Precharge failed, precharge timed out".

[0054] Thus, as can be seen from steps S101 to S105, in this preferred embodiment, the traditional experience-based "timeout protection" is replaced by the quantification of physical heat and the calculation of dynamic timeout threshold, which maximizes the adaptability of the power battery to different capacity loads. That is, under the premise that the pre-charging resistor does not burn out, the pre-charging can be allowed for as long as possible, and multi-level protection during the charging process is realized, which significantly improves the robustness and load-bearing start-up capability of the system.

[0055] In a preferred embodiment, before closing the precharge circuit (i.e., before charging), a residual voltage discharge circuit is closed first. For example, the two ends of the load are short-circuited through a resistor (e.g., a precharge resistor), and the short-circuit time is set to 500 milliseconds. The purpose is to release the residual voltage in the load capacitor at the load end. In other embodiments, the residual voltage discharge circuit can also be closed whenever the load is de-energized.

[0056] As a preferred example, the methods for obtaining the time of the first boost stage and the time of the second boost stage include: Starting from the closed pre-charge circuit, when the load voltage collected in real time first reaches the first stage voltage threshold at the first time point and remains above the first stage voltage threshold for a preset time after the first time point, and when the load voltage first reaches the second stage voltage threshold at the second time point and remains above the second stage voltage threshold for a preset time after the second time point, it is determined that the first boost stage time when the load voltage increases to the first stage voltage threshold and the second boost stage time when the load voltage increases from the first stage voltage threshold to the second stage voltage threshold are detected. The first time point is taken as the first boost stage time, and the difference between the second time point and the first time point is taken as the second boost stage time.

[0057] Although this example requires a preset time period, the final recorded first and second time points are the moments when the load voltage actually reaches the threshold for the first time (i.e., the first stage voltage threshold and the second stage voltage threshold), thus avoiding voltage fluctuation problems to a certain extent and ensuring the physical accuracy of the time data.

[0058] The specific methods for obtaining the first and second time points include: After closing the pre-charge circuit, a timer is used to keep track of the load voltage. When the load voltage is greater than or equal to the first-stage voltage threshold, the timer's timing is recorded as the first candidate moment. Load voltage is then continuously sampled within a preset time period after the first candidate moment (including the first candidate moment). If no load voltage is found to be lower than the first-stage voltage threshold, the first candidate moment is taken as the first time point. If a load voltage is found to be lower than the first-stage voltage threshold, the timing of that occurrence is reset as the first candidate moment. This process is repeated until the first time point is obtained.

[0059] The method for obtaining the second time point is similar, and will not be described in detail in this embodiment.

[0060] When sampling voltage at a sampling frequency of 1kHz, the preferred time length for the preset time is 2 to 5 milliseconds. This embodiment will be described using 3 milliseconds as an example.

[0061] As a preferred example, methods for obtaining the standard resistor-capacitor time-consuming ratio include: During the charging process of any first RC circuit, the time it takes for the voltage across the capacitor (i.e., the load capacitor) to increase to the first stage voltage threshold is denoted as the first time T1 (equivalent to the first boost stage time in the RC circuit). The time it takes for the voltage across the capacitor to increase from the first stage voltage threshold to the second stage voltage threshold is denoted as the second time T2 (equivalent to the second boost stage time obtained in the RC circuit). Standard resistor-capacitor time ratio. This corresponds to the proportion of time taken for the load voltage to climb by one voltage stage in an RC circuit, describing the inherent circuit characteristics of an RC circuit. In an optional example, the standard resistor-capacitor time ratio obtained in the preferred example above is used... Plus As the standard resistor-capacitor time ratio obtained in this optional example, its purpose is to introduce To encompass: Errors caused by engineering factors such as internal resistance fluctuations, resistance temperature drift, and voltage sampling discretization errors in power batteries, and to avoid erroneous charging process protection due to failure to consider these engineering factors. As an example, It equals 0.5 volts.

[0062] As a preferred example, the method for calculating the load capacitance value includes: The RC circuit formed by the precharge circuit is referred to as the second RC circuit (that is, the precharge circuit can be equivalent to a second RC circuit during the charging process). The capacitor and resistor in the second RC circuit refer to the load capacitor and the precharge resistor. The first boost stage time calculated above represents the time it takes for the voltage across the load capacitor to increase from 0 volts to the first stage voltage threshold.

[0063] Based on the properties of the second RC circuit, the load capacitance value is calculated according to the pre-charge resistance value and the time consumed in the first boost stage.

[0064] As a preferred example, the specific method for obtaining the dynamic timeout threshold is as follows: A preset cycle frequency is used. The product of the time constant of the second RC circuit (i.e., the product of the pre-charge resistance value and the load capacitance value) and the cycle frequency is denoted as the reference time constant. .

[0065] Taking a period frequency of 3 as an example, for the obtained reference time constant The voltage across the load capacitor of the second RC circuit during time... The internal capacity can theoretically be charged to full voltage (i.e.) This represents 95.02% of the original value. This example adds a safety margin based on this theory, specifically referring to the time constant. After being enlarged by a certain factor (for example, after being enlarged by 0.5 times, that is...) (1.5 times) is used as the dynamic timeout threshold; This dynamic timeout threshold serves as an update to the fixed timeout period. Therefore, when the charging time (i.e., the closing time of the pre-charge circuit) exceeds the updated timeout period (i.e., the dynamic timeout threshold), the load voltage (i.e., the voltage of the load capacitor in the second RC circuit) does not exceed the limit. When the charge reaches 95.02%, charging protection measures are implemented.

[0066] When the charging time is less than or equal to the updated timeout (i.e., the dynamic timeout threshold), or greater than the updated timeout while the load voltage is greater than... If the voltage reaches 95.02%, then continue charging until the load capacitor is fully charged (i.e., the load voltage equals 95.02%). In other embodiments, the load voltage may also be greater than 99% × It is considered fully charged. After being fully charged (that is, after the pre-charge is completed), the power battery will be directly connected to the load to supply power, and the pre-charge resistor will no longer be connected in series in the power supply circuit (that is, the pre-charge resistor will be cut off from the power supply circuit).

[0067] As a preferred example, the first-stage voltage threshold is set to the initial battery voltage. The voltage threshold for the second stage is set to the initial battery voltage, which is a1 times that of the first stage. a2 times, satisfying 0 <a1<a2<1。

[0068] As an example, the methods for calculating T1 and T2 include: It is known that in the first RC circuit, the voltage across the capacitor at time t is denoted as V(t), where the initial voltage V(0) = 0 volts, satisfying the formula: .

[0069] Based on this formula, it can be seen that the voltage across capacitor C rises from 0 volts to... Time consumed at (i.e., the first stage voltage threshold) The voltage across capacitor C is from Climb to Time consumed at (i.e., the second-stage voltage threshold) .

[0070] Where exp() represents an exponential function with the natural constant as the base, and ln() represents a logarithmic function with the natural constant as the base. R represents the resistance value in the first RC circuit, and C represents the capacitance value in the first RC circuit. When calculating the preset standard resistance-capacitance time ratio, This term is reduced out, so the preset standard resistance-capacitance time ratio and the measured time ratio are both dimensionless data, which means they are unrelated to the resistance and capacitance in the RC circuit. Therefore, the above process does not require attention to the capacitance and resistance values ​​in the first RC circuit.

[0071] As an example, based on the properties of the second RC circuit, the load capacitance value is calculated according to the pre-charge resistance value and the time consumed in the first boost stage, including the following formulas: The load capacitance value is expressed as The pre-charge resistance is expressed as Let t1 represent the time taken for the first boost stage, and let the voltage threshold for the first stage be... The second RC circuit at this time satisfies: Solve according to this formula. .

[0072] As an example, let a1 = 0.25 and a2 = 0.5. At this point, the default standard resistance-capacitance time ratio is 1.409. All values ​​in this embodiment are rounded to three decimal places.

[0073] This concludes the example.

[0074] In another embodiment of the present invention, a power battery BMS protection system is provided. The system includes a pre-charge resistor for limiting the current of the pre-charge circuit, and a controllable relay for controlling the closing and opening of the pre-charge circuit and cutting off the pre-charge resistor from the power supply circuit, referred to as the first relay and the second relay, respectively.

[0075] In one example, the second relay is connected in parallel across the pre-charge resistor, and when the contacts of the second relay are closed, the two ends of the pre-charge resistor are short-circuited; wherein the first relay is connected in series with the pre-charge resistor.

[0076] When the contacts of the second relay are open, the precharge circuit is closed and opened by closing and opening the contacts of the first relay.

[0077] When the second relay contacts are closed, if the first relay contacts are closed, the power supply circuit between the power battery and the load is connected (that is, the power battery is directly connected to the load for power supply). At this time, the two ends of the pre-charge resistor are short-circuited, thereby cutting off the pre-charge resistor from the power supply circuit. If the first relay contacts are open, the power battery does not supply power to the load.

[0078] The system also includes a protection module comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the memory and processor are contained in a BMS (Battery Management System), and the processor executes all the steps of all the above embodiments when running the computer program.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for protecting a power battery, characterized in that, The method includes the following steps: During the process of the power battery charging the load capacitor in the load terminal through the pre-charge circuit, the load voltage of the load terminal is collected in real time. If the time consumed in the first boost phase when the load voltage increases to the first stage voltage threshold and the time consumed in the second boost phase when the load voltage increases from the first stage voltage threshold to the second stage voltage threshold are monitored, then the ratio of the time consumed in the second boost phase to the time consumed in the first boost phase is taken as the measured time ratio. The measured time consumption ratio is compared with the preset standard resistance-capacitance time consumption ratio to identify whether there is a leakage path in the circuit at the load end. If a leakage path is identified, charging protection measures are implemented. The specific steps for obtaining the standard resistance-capacitance time ratio are as follows: The time taken for the voltage across the capacitor in any first RC circuit to increase to the first stage voltage threshold is denoted as the first time, and the time taken for the voltage across the capacitor to increase from the first stage voltage threshold to the second stage voltage threshold is denoted as the second time. The ratio of the second time to the first time is used as the standard resistance-capacitance time ratio.

2. The power battery protection method according to claim 1, characterized in that, The method further includes: Starting from the closed pre-charge circuit, when the load voltage collected in real time first reaches the first stage voltage threshold at the first time point and remains above the first stage voltage threshold for a preset time after the first time point, and when the load voltage first reaches the second stage voltage threshold at the second time point and remains above the second stage voltage threshold for a preset time after the second time point, it is determined that the first boost stage time when the load voltage increases to the first stage voltage threshold and the second boost stage time when the load voltage increases from the first stage voltage threshold to the second stage voltage threshold are detected. The first time point is taken as the first boost stage time, and the difference between the second time point and the first time point is taken as the second boost stage time.

3. The power battery protection method according to claim 1, characterized in that, The method further includes: If no leakage path is identified, the load capacitance value is calculated based on the time consumed in the first boost stage. Calculate the cumulative heat generated during the full charging process of the load capacitor based on the load capacitance value; Based on the accumulated heat generation, it is determined whether the current load capacitor has an overcapacity fault. If an overcapacity fault is detected, charging protection measures are implemented.

4. The power battery protection method according to claim 3, characterized in that, The method further includes: If no capacity over-limit fault is detected, a dynamic timeout threshold is calculated based on the load capacitance value; and the preset fixed timeout time is updated using the dynamic timeout threshold. Use the updated timeout period for charging timeout protection.

5. The power battery protection method according to claim 4, characterized in that, The specific steps for obtaining the dynamic timeout threshold are as follows: The reference time constant is calculated based on the preset pre-charge resistance value and load capacitance value, and then multiplied by a certain factor to serve as the dynamic timeout threshold.

6. The power battery protection method according to claim 3, characterized in that, The specific steps for obtaining the load capacitance value are as follows: In the second RC circuit formed by the pre-charge circuit, the load capacitance value is calculated based on the preset pre-charge resistance value and the time consumed in the first boost stage.

7. The power battery protection method according to claim 1, characterized in that, The method further includes: if the load voltage is detected to be consistently lower than the second-stage voltage threshold within a preset maximum allowable pre-charging time, then charging protection measures are implemented.

8. The power battery protection method according to claim 1, characterized in that, Before charging the load capacitor at the load end through the pre-charge circuit, release the residual voltage in the load capacitor at the load end.

9. A power battery BMS protection system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor runs the computer program, it implements all the steps of the power battery protection method according to any one of claims 1 to 8.

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