An electric vehicle pre-charge fault detection method and an on-board controller

Abstract

The application discloses an electric vehicle pre-charging fault detection method and a vehicle-mounted controller, and realizes timely and accurate detection of pre-charging faults. The method comprises the following steps: in response to a high-voltage power-on instruction, identifying a battery charging / discharging mode, judging whether there is a need to store pre-charging information into a memory in the current mode, wherein the pre-charging information comprises changes of preset parameters in a pre-charging process and a pre-charging time constant; if yes, connecting a pre-charging loop, monitoring changes of prediction parameters to judge whether pre-charging is completed, and obtaining pre-charging information in the current mode and storing the pre-charging information into the memory when the pre-charging is completed; if no, connecting the loop, monitoring changes of prediction parameters, calling pre-charging information in the current mode from the memory, and predicting a pre-charging time required in the current mode according to the called pre-charging information; before the pre-charging time is reached, comparing the monitored changes of prediction parameters with the called changes of prediction parameters to judge whether there is a pre-charging fault.

Description

Technical Field

[0001] This invention relates to the field of pre-charging management technology, and more specifically, to a method for detecting pre-charging faults in electric vehicles and an on-board controller. Background Technology

[0002] Before electric vehicles are powered on at high voltage (high voltage power supply refers to the output of high voltage from the power battery to supply high voltage electrical components of the vehicle, such as the motor controller and drive motor), the bus capacitor of the motor controller needs to be pre-charged to reduce the sparking and arcing when the high voltage relay is closed, avoid high voltage impact damage to high voltage components, and improve the safety of the high voltage system.

[0003] Power battery power supply circuit with pre-charge circuit, for example Figure 1 As shown, the system includes: a power battery, a main positive relay K1, a main negative relay K2, a pre-charge relay K3, a pre-charge resistor R, a bus capacitor C, a motor controller, and a motor M. The pre-charge relay K3 is connected in series with the pre-charge resistor R, and then in parallel with the main positive relay K1. Before the electric vehicle is powered on, the main negative relay K2 and the pre-charge relay K3 are closed to connect the pre-charge circuit. During the pre-charge process, the voltage U of the bus capacitor C... C The pre-charge current I gradually increases. P Gradually decrease, when the voltage U C Approaching the power battery voltage U max For example, reaching U max When the charge reaches 95%, first turn on the main positive relay K1 and then turn off the pre-charge relay K3 to complete the pre-charge. Figure 2 For the voltage U during the pre-charging process C and pre-charge current I P A schematic diagram of the change curve, I P =(U max -U C ) / R, Figure 2 The time t1 in the figure represents the time when the pre-charge is completed.

[0004] Complete discharge at the motor terminal (i.e., U) C If the parameters of components such as the bus capacitor C and the pre-charge resistor R are known (e.g., 0), the required pre-charge time is fixed and predictable. Current technology typically calculates the pre-charge time in advance and embeds it in the software, ending pre-charge when the time is reached. However, in actual operating conditions, the motor may not be fully discharged, and the actual values ​​of component parameters inevitably deviate from their nominal values. Furthermore, the battery's operating mode (charging or discharging), vehicle operating time, and operating environment can all cause changes in the parameters of the bus capacitor C. Therefore, the pre-charge time is difficult to accurately predict, potentially leading to pre-charge failures, such as the pre-charge resistor R overheating and being damaged due to excessive pre-charge time. Summary of the Invention

[0005] In view of this, the present invention provides a method for detecting pre-charging faults in electric vehicles and an on-board controller, so as to achieve timely and accurate detection of pre-charging faults.

[0006] A method for detecting pre-charging faults in electric vehicles, comprising:

[0007] In response to the high-voltage power-on command of the electric vehicle, the charging / discharging mode of the power battery is identified, and it is determined whether there is a need to store pre-charge information in the memory under the current mode. The pre-charge information includes the changes of preset parameters and the pre-charge time constant during the pre-charge process.

[0008] If required, the pre-charging circuit is activated, and the pre-charging is completed by monitoring the changes in the predicted parameters; when pre-charging is completed, the pre-charging information in the current mode is obtained and stored in the memory.

[0009] If there is no demand, then: the pre-charging circuit is turned on, the changes in the prediction parameters are monitored, and the pre-charging information in the current mode is retrieved from the memory. The pre-charging time required in the current mode is predicted based on the retrieved pre-charging information. Before the pre-charging duration reaches the pre-charging time, the changes in the monitored prediction parameters and the changes in the retrieved prediction parameters are compared to determine whether there is a pre-charging fault.

[0010] Optionally, determining whether there is a need to store precharge information in the memory under the current mode includes:

[0011] Determine whether a storage command has been received manually or automatically by the system. If so, determine if there is a need to store precharge information in the memory in the current mode. If not, determine if there is no need to store precharge information in the memory in the current mode.

[0012] Optionally, the changes in the preset parameters stored in the memory include: the voltage change curve of the bus capacitor of the motor controller over time, and the voltage change rate of the bus capacitor over time.

[0013] Optionally, the step of determining whether pre-charging is complete by monitoring the changes in the predicted parameters includes: determining whether the absolute value of the voltage change rate is less than a first preset value; if so, determining that pre-charging is complete.

[0014] Optionally, obtaining the pre-charge time constant in the current mode and storing it in the memory includes: obtaining U0, U1 and t monitored in the current mode, substituting them into the zero-state response equation of the first-order RC series circuit, calculating the pre-charge time constant in the current mode and storing it in the memory.

[0015] Wherein, U0 is the voltage of the bus capacitor at the start of pre-charging, U1 is the voltage of the bus capacitor at the end of pre-charging, and t is the pre-charging time.

[0016] Optionally, determining whether a pre-charging fault exists by comparing the monitored changes in the predicted parameters with the retrieved changes in the predicted parameters before the pre-charging duration reaches the pre-charging time includes:

[0017] Calculate the time ti required for the absolute value of the voltage change rate to reach the i-th preset change rate; i = 1, 2, ..., n, where n is a positive integer;

[0018] When the pre-charging duration reaches the time ti, it is determined whether the difference between the absolute value of the voltage change rate monitored at the current time node and the reference value exceeds the second preset value. If so, it is determined that there is a pre-charging fault. The reference value is the absolute value of the voltage change rate retrieved at the same time node.

[0019] Among them, the k-th preset rate of change is greater than the (k+1)-th preset rate of change, k = 1, 2, ..., n-1, and the n-th preset rate of change is greater than the first preset value.

[0020] Optionally, the electric vehicle pre-charging fault detection method further includes: when the pre-charging duration reaches the pre-charging time, comparing the monitored changes in the predicted parameters with the retrieved changes in the predicted parameters again to determine whether a pre-charging fault exists.

[0021] Optionally, the memory is an electrically erasable programmable read-only memory (EEPROM).

[0022] An on-board controller includes a processor and a program memory, wherein the program memory stores a program that, when executed by the processor, implements any of the electric vehicle pre-charging fault detection methods disclosed above.

[0023] Optionally, the on-board controller is the controller of the power battery management system (BMS).

[0024] As can be seen from the above technical solution, under the condition that the working state of the electric vehicle pre-charging circuit is difficult to accurately predict, the present invention learns the electric vehicle pre-charging information according to the power battery charging / discharging mode and stores it in the memory. Subsequently, during the electric vehicle pre-charging process, the pre-charging information of the corresponding charging / discharging mode is adaptively retrieved as a reference to measure whether the current pre-charging process deviates significantly from the reference value. If there is a significant deviation, it indicates that there is a pre-charging fault; if there is no significant deviation, it indicates that there is no pre-charging fault, thereby realizing timely and accurate detection of pre-charging faults. Attached Figure Description

[0025] 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.

[0026] Figure 1 A circuit diagram of a power battery power supply circuit with a pre-charging circuit is disclosed in the prior art.

[0027] Figure 2 The voltage U of the bus capacitor C during the pre-charging process disclosed in the prior art C and pre-charging current I P A schematic diagram of the change curve;

[0028] Figure 3 This is a flowchart of a pre-charging fault detection method for electric vehicles disclosed in an embodiment of the present invention;

[0029] Figure 4 This is a flowchart of a self-learning stage control method for electric vehicle charging mode disclosed in an embodiment of the present invention;

[0030] Figure 5 This is a flowchart of an adaptive stage control method for electric vehicle charging mode disclosed in an embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of a vehicle-mounted controller structure disclosed in an embodiment of the present invention. Detailed Implementation

[0032] For the sake of clarity and reference, the technical terms, abbreviations, or acronyms used below are summarized as follows:

[0033] MCU: Motor Control Unit, also known as motor controller;

[0034] BMS: Battery Management System;

[0035] EEPROM: Electrically Erasable Programmable Read-Only Memory.

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] See Figure 3 This invention discloses a method for detecting pre-charging faults in electric vehicles, comprising:

[0038] Step S01: In response to the high-voltage power-on command of the electric vehicle, identify the charging / discharging mode of the power battery (that is, identify whether the power battery is in charging mode or discharging mode), and then proceed to step S02.

[0039] In this context, "high-voltage power-on" in an electric vehicle refers to the power battery outputting high-voltage electricity to supply high-voltage electrical components in the vehicle, such as the motor controller and drive motor. "Power battery in charging mode" means that the charging gun is plugged into the electric vehicle's charging port to charge the power battery. If the electric vehicle is powered on at high voltage but no charging gun is inserted, it indicates that the power battery is in discharging mode.

[0040] Step S02: Determine if there is a need to store pre-charge information in the memory under the current mode. If yes, proceed to step S03; otherwise, proceed to step S04. The pre-charge information includes: changes in preset parameters during the pre-charge process and the pre-charge time constant τ.

[0041] Step S03: Connect the pre-charging circuit and determine whether pre-charging is complete by monitoring the changes in the predicted parameters; when pre-charging is complete, obtain the pre-charging information in the current mode and store it in the memory, and then return to step S01.

[0042] Step S04: Connect the pre-charging circuit, monitor the changes in the prediction parameters, retrieve the pre-charging information in the current mode from the memory, predict the required pre-charging time t in the current mode based on the retrieved pre-charging information, and then proceed to step S05.

[0043] The pre-charge time t refers to the time required for the MCU's bus capacitor C to start pre-charging from zero voltage until pre-charging is complete.

[0044] Step S05: Before the pre-charging duration reaches the pre-charging time t, the changes in the monitored predicted parameters and the retrieved predicted parameters are compared to determine whether there is a pre-charging fault, and then the process returns to step S01.

[0045] The working principle of the embodiments of the present invention will be described in detail below:

[0046] This invention is applied to an on-board controller. Under complex conditions such as different resistance or precision of the pre-charging resistor R, different capacitance or precision of the bus capacitor C, different charging / discharging modes, vehicle operating time, or different vehicle operating environments leading to variations in the bus capacitor C, and different voltages across the bus capacitor C at the start of pre-charging, the controller can self-learn the electric vehicle's pre-charging information according to the power battery's charging / discharging mode and store it in the memory. Subsequently, during the electric vehicle's pre-charging process, it adaptively retrieves the pre-charging information from the corresponding charging / discharging mode as a reference (when the power battery is in charging mode, it retrieves the pre-charging information from the charging mode; when the power battery is in discharging mode, it retrieves the pre-charging information from the discharging mode) to measure whether the current pre-charging process significantly deviates from the reference value. If there is a significant deviation, it indicates a pre-charging fault, and the pre-charging circuit needs to be disconnected to prevent further escalation. If there is no significant deviation, it indicates no pre-charging fault. Then, when the duration of the pre-charging process reaches the required pre-charging time t, the power battery power supply circuit is first connected, and then the pre-charging circuit is disconnected.

[0047] The vehicle controller is, for example, the controller in a BMS, but is not limited to it. The memory is recommended to be an EEPROM, a type of storage chip that retains data even after power loss.

[0048] After an electric vehicle is powered on by high voltage, whether the on-board controller enters the self-learning phase or the adaptive phase depends on whether there is a need to store pre-charge information in the memory under the current charging / discharging mode (i.e., whether any one or more of the aforementioned complex operating conditions have occurred). Storing pre-charge information in the memory includes writing or modifying the pre-charge information. Generally, pre-charge information needs to be written to the memory when the electric vehicle is first powered on by high voltage. Afterwards, if the parameters of components such as the bus capacitor C and the pre-charge resistor R change due to factors such as prolonged operation of the electric vehicle, the pre-charge information in the memory needs to be modified.

[0049] One method for determining whether there is a need to store pre-charge information in the memory under the current mode is to: determine whether a storage command, triggered manually or automatically by the system, has been received. If so, it is determined that there is a need to store pre-charge information in the memory under the current mode; otherwise, it is determined that there is no need to store pre-charge information in the memory under the current mode. An automatic storage command could be triggered when the total vehicle running time reaches a preset time, or when the total vehicle mileage reaches a preset mileage, etc.

[0050] During the pre-charging process, the voltage U of the bus capacitor C is...C Voltage U C rate of change k, pre-charge current I P Each of these parameters exhibits a specific pattern of change, therefore the changes in the preset parameters stored in the memory can be selected from the following curves: U C Curves of k versus time, curves of k versus time, I P Curves showing changes over time, etc. In one example, the changes in the preset parameters that can be selected and stored in memory include: U C Curves showing the change over time and the change of k over time.

[0051] Since the absolute value of the rate of change k gradually decreases during the pre-charging process, in the example above, during the self-learning phase, the determination of whether pre-charging is complete can be made by monitoring the changes in the prediction parameters: determining whether the absolute value of the rate of change k is less than a first preset value (the first preset value is zero or a value close to zero). If so, the pre-charging is determined to be complete; if not, the pre-charging is determined to be incomplete.

[0052] Furthermore, the pre-charge loop is known to be a typical first-order RC series circuit, with the bus capacitance C present in the MCU. The selection of the pre-charge resistor R needs to be determined based on the zero-state response equation of a first-order RC series circuit. This zero-state response equation is as follows:

[0053] U1–-U0=U max (1-e -t / τ )

[0054] In the formula:

[0055] U1 is the voltage across bus capacitor C when pre-charging is complete, in V;

[0056] U0 is the voltage across bus capacitor C at the start of pre-charging, in V;

[0057] U max This represents the maximum voltage across the power battery, in V.

[0058] t represents the required pre-charging time, in seconds.

[0059] τ is the pre-charge time constant, τ=R*C;

[0060] R represents both the pre-charge resistor and its resistance value, with the unit being Ω.

[0061] C represents both the bus capacitance and its capacitance value, with the unit of capacitance being F.

[0062] Based on this, in the above example, during the self-learning phase, obtaining the pre-charge time constant τ in the current mode and storing it in the memory can be achieved by: obtaining U0, U1, and t monitored in the current mode, substituting them into the zero-state response equation, calculating the pre-charge time constant τ in the current mode, and storing it in the memory. Correspondingly, during the adaptive phase, predicting the required pre-charge time t in the current mode based on the retrieved pre-charge information can be achieved by: substituting the currently monitored U0, the retrieved τ, and the retrieved U1 into the zero-state response equation to calculate the required pre-charge time t in the current mode.

[0063] In the above example, during the adaptive phase, before the pre-charge duration reaches the pre-charge time, determining whether a pre-charge fault exists by comparing the monitored changes in the predicted parameters with the retrieved changes in the predicted parameters can be as follows:

[0064] Calculate the time ti required for the absolute value of the voltage change rate to reach the i-th preset change rate; i = 1, 2, ..., n, where n is a positive integer;

[0065] When the pre-charging duration reaches the specified time ti, it is determined whether the difference between the absolute value of the voltage change rate monitored at the current time node and the reference value exceeds a second preset value. If so, a pre-charging fault is identified. The reference value is the absolute value of the voltage change rate retrieved at the same time node. The k-th preset change rate is greater than the (k+1)-th preset change rate, where k = 1, 2, ..., n-1, and the n-th preset change rate is greater than the first preset value. Generally, n = 1 is sufficient.

[0066] Optionally, based on any of the above-disclosed embodiments, in the adaptive phase, when the pre-charging duration reaches the pre-charging time, the changes in the monitored predicted parameters and the retrieved predicted parameters are compared again to determine whether there is a pre-charging fault, thereby performing a final pre-charging fault verification at the end of the pre-charging time to avoid errors.

[0067] Based on any of the embodiments disclosed above, the control method for the self-learning phase in the electric vehicle charging mode is, for example... Figure 4 As shown, it includes:

[0068] Step S11: Connect the pre-charge circuit, monitor k, and then proceed to step S12.

[0069] Step S12: Determine if k is zero. If yes, proceed to step S13; otherwise, return to step S12.

[0070] Step S13: Determine that pre-charging is complete, then proceed to step S14.

[0071] Step S14: Obtain U during the pre-charging process C The curves showing the changes over time and the curves showing the changes of k over time are obtained, and then the process proceeds to step S15.

[0072] Step S15: Calculate the pre-charge time constant τ, and then proceed to step S16.

[0073] Step S16: Place the U C The curves of k changing over time, the curves of k changing over time, and the pre-charge time constant τ are stored in the EEPROM, thus ending this round of control.

[0074] Based on any of the embodiments disclosed above, the control method for the adaptive phase in the electric vehicle charging mode is, for example... Figure 5 As shown, it includes:

[0075] Step S21: Connect the pre-charge circuit, calculate the time t1 required for the absolute value of k to reach the preset rate of change, and then proceed to step S22.

[0076] Step S22: Time t1, determine whether the difference between the absolute value of k monitored at the current time node and the reference value 1 exceeds the second preset value, where the reference value 1 is the absolute value of k retrieved at the same time node; if it does not exceed the limit, proceed to step S23; if it does exceed the limit, proceed to step S25.

[0077] Step S23: When the pre-charging duration reaches the required pre-charging time t, determine again whether the difference between the absolute value of k monitored at the current time node and the reference value 2 exceeds the second preset value. The reference value 2 is the absolute value of k retrieved at the same time node. If it does not exceed the limit, proceed to step S24. If it does exceed the limit, proceed to step S25.

[0078] Step S24: Determine that pre-charging is complete, and this round of control ends.

[0079] Step S25: A pre-charge fault is detected, and this round of control ends.

[0080] The control method for the self-learning / adaptive phase in the electric vehicle discharge mode can be derived similarly and will not be elaborated further.

[0081] It should also be noted that the embodiments of the present invention are not limited to... Figure 1 The power supply circuit with pre-charging circuit shown can be simplified without affecting the implementation of the embodiments of the present invention.

[0082] Furthermore, embodiments of the present invention also disclose an on-board controller, such as... Figure 6As shown, it includes a processor and a program memory, wherein the program memory stores a program, which, when executed by the processor, implements any of the electric vehicle pre-charging fault detection methods disclosed above.

[0083] Optionally, the vehicle controller is a BMS controller.

[0084] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the vehicle controller disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0085] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar but different objects and are not necessarily used to describe a specific order or sequence. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the embodiments of the invention. Therefore, the embodiments of the invention are not to be limited to the embodiments shown herein, but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting pre-charging faults in electric vehicles, characterized in that, include: In response to the high-voltage power-on command of the electric vehicle, the charging / discharging mode of the power battery is identified, and it is determined whether there is a need to store pre-charge information in the memory under the current mode. The pre-charge information includes the changes of preset parameters and the pre-charge time constant during the pre-charge process. If required, the following steps are taken: the pre-charging circuit is activated, and the pre-charging is completed by monitoring the changes in the preset parameters; when the pre-charging is completed, the pre-charging information in the current mode is obtained and stored in the memory. If there is no demand, then: the pre-charging circuit is turned on, the changes of the preset parameters are monitored, and the pre-charging information in the current mode is retrieved from the memory. Based on the retrieved pre-charging information, the required pre-charging time in the current mode is predicted. Before the pre-charging duration reaches the pre-charging time, the changes in the monitored preset parameters are compared with the changes in the retrieved preset parameters to determine whether there is a pre-charging fault. The changes in the preset parameters stored in the memory include: the voltage change curve of the bus capacitor of the motor controller over time, and the voltage change rate of the bus capacitor over time. Before the pre-charging duration reaches the pre-charging time, the step of determining whether a pre-charging fault exists by comparing the monitored changes in the preset parameters with the retrieved changes in the preset parameters includes: Calculate the time ti required for the absolute value of the voltage change rate to reach the i-th preset change rate; i = 1, 2, ..., n, where n is a positive integer; When the pre-charging duration reaches the time ti, it is determined whether the difference between the absolute value of the voltage change rate monitored at the current time node and the reference value exceeds the second preset value. If so, it is determined that there is a pre-charging fault. The reference value is the absolute value of the voltage change rate retrieved at the same time node. Among them, the k-th preset rate of change is greater than the (k+1)-th preset rate of change, k = 1, 2, ..., n-1, and the n-th preset rate of change is greater than the first preset value.

2. The electric vehicle pre-charging fault detection method according to claim 1, characterized in that, The determination of whether there is a need to store precharge information in the memory under the current mode includes: Determine whether a storage command has been received manually or automatically by the system. If so, determine if there is a need to store precharge information in the memory in the current mode. If not, determine if there is no need to store precharge information in the memory in the current mode.

3. The electric vehicle pre-charging fault detection method according to claim 1, characterized in that, The step of determining whether pre-charging is complete by monitoring changes in the preset parameters includes: determining whether the absolute value of the voltage change rate is less than a first preset value; if so, determining that pre-charging is complete.

4. The electric vehicle pre-charging fault detection method according to claim 1 or 3, characterized in that, Obtaining the pre-charge time constant in the current mode and storing it in the memory includes: obtaining U0, U1 and t monitored in the current mode, substituting them into the zero-state response equation of the first-order RC series circuit, calculating the pre-charge time constant in the current mode and storing it in the memory. Wherein, U0 is the voltage of the bus capacitor at the start of pre-charging, U1 is the voltage of the bus capacitor at the end of pre-charging, and t is the pre-charging time.

5. The electric vehicle pre-charging fault detection method according to claim 1, characterized in that, The electric vehicle pre-charging fault detection method further includes: when the pre-charging duration reaches the pre-charging time, comparing the monitored changes in the preset parameters with the retrieved changes in the preset parameters again to determine whether a pre-charging fault exists.

6. The electric vehicle pre-charging fault detection method according to claim 1, characterized in that, The memory is an electrically erasable programmable read-only memory (EEPROM).

7. A vehicle-mounted controller, characterized in that, It includes a processor and a program memory, wherein the program memory stores a program, and when the program is executed by the processor, it implements the electric vehicle pre-charging fault detection method as described in any one of claims 1 to 6.

8. The vehicle controller according to claim 7, characterized in that, The on-board controller is the controller of the power battery management system (BMS).

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