Relay fault detection method and device, vehicle, medium and product

Abstract

The invention provides a relay fault detection method and device, a vehicle, a medium and a product, and relates to the technical field of electric vehicle charging, and the method comprises the steps: for each stage of a preparation stage, a pre-charging stage, a boosting stage and a discharging stage, in each detection period of a plurality of detection periods of the stage, determining a relay fault in the pre-charging stage, the boosting stage and the discharging stage; acquiring at least one of a first voltage between the second end of the first relay and the second end of the second relay and a second voltage between the second end of the third relay and the first end of the second relay; and performing fault detection on the first relay, the second relay and / or the third relay during the stage based on at least one of the first voltage and the second voltage acquired in each of the plurality of detection periods. According to the scheme, relay fault detection in the boosting process can be completed, the vehicle manufacturing cost is reduced, and the complexity of detection logic is reduced.

Description

Technical Field

[0001] This application relates to the field of electric vehicle charging technology, and in particular to a relay fault detection method, device, vehicle, medium, and product. Background Technology

[0002] With the rapid development of new energy vehicles, electric vehicle charging technology has become increasingly important. The charging process for electric vehicles typically involves a complex power management system, among which boost charging circuits are a common topology. Boost charging circuits use relays to control the current path, achieving efficient charging of the battery.

[0003] However, in practical applications, relays, as electromechanical components, are susceptible to faults such as mechanical wear, arc corrosion, contact adhesion, and open circuits. These faults can lead to abnormal charging processes, reduced charging efficiency, and even safety hazards. For example, relay contact adhesion may prevent the current from being effectively cut off, causing overcharging or battery damage; abnormal disconnection of relay contacts may hinder the establishment of a charging circuit, leading to charging failure or interruption.

[0004] Currently, existing relay fault detection methods typically determine the sticking status of the fast-charging positive relay by dynamically adjusting the charging request current and comparing the current flowing through the boost positive relay with the output current of the charging pile. Alternatively, they can acquire the voltage values ​​between the output terminals of the boost negative relay and the output terminals of the boost positive relay, the input terminals of the boost negative relay and the input terminals of the boost positive relay, and the output terminals of the boost negative relay and the input terminals of the boost positive relay in real time, and compare these four voltage values ​​with preset conditions to diagnose the status of the boost positive and boost negative relays. However, the detection methods that compare current values ​​require the use of current sensors; while the detection methods that compare four sets of voltage values ​​require the use of at least four voltage sensors, which not only increases the manufacturing cost of electric vehicles but also increases the complexity of relay fault detection. Summary of the Invention

[0005] This application provides a relay fault detection method, device, vehicle, medium, and product, which can solve the technical problem that existing relay fault detection methods increase the manufacturing cost and fault detection complexity of electric vehicles.

[0006] According to a first aspect of this application, a relay fault detection method is provided for detecting faults in relays of a boost charging circuit during a charging process in which a charging pile charges a battery through a boost charging circuit. The charging process sequentially includes a preparation stage (as a start stage), a pre-charge stage, a boost stage, and a discharge stage (as an end stage). The boost charging circuit includes a first relay, a second relay, a third relay, a first capacitor, a first inductor, and a boost sub-circuit. The positive and negative terminals of the charging pile are respectively connected to a first terminal of the third relay and a first terminal of the second relay. The second terminal of the third relay is connected to the first terminal of the first relay via the first inductor. The first capacitor is connected between the second terminal of the third relay and the first terminal of the second relay. The second terminals of the first relay and the second relay are respectively connected to the positive and negative input terminals of the boost sub-circuit. The boost sub-circuit is connected to the battery to be charged. The method includes: For each of the preparation phase, pre-charge phase, boost phase, and discharge phase, a fault detection process is performed during that phase, the fault detection process including: In each of the multiple detection cycles in this phase, at least one of the first voltage between the second terminal of the first relay and the second terminal of the second relay and the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired; Based on at least one of the first voltage and the second voltage obtained in each of the plurality of detection cycles, fault detection is performed on the first relay, the second relay and / or the third relay during the phase.

[0007] In some implementations, during the preparation phase, the first relay and the second relay are in an open state, and the fault detection process performed during the preparation phase includes: During the first detection cycle of the preparation phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is obtained as the second voltage of the first detection cycle. In each of the first number of detection cycles during the preparation phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle. If, within the first number of detection cycles, the difference between the current second voltage and the second voltage of the first detection cycle is greater than the first threshold voltage for N consecutive detection cycles, it is determined that the first relay and / or the second relay has a sticking fault, where N is a positive integer greater than 2 and less than the first number.

[0008] In some implementations, during the pre-charge phase, the first relay and the second relay are in a closed state, and the third relay is in an open state. The fault detection process performed during the pre-charge phase includes: In each of the second number of detection cycles during the pre-charge phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is obtained as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay and the second terminal of the second relay is obtained as the current first voltage of that detection cycle. If, within the second number of detection cycles, the current second voltage is greater than the second threshold voltage for M consecutive detection cycles, and the difference between the current second voltage and the current first voltage for the M consecutive detection cycles is greater than the third threshold voltage, it is determined that the first relay and / or the second relay has an abnormal disconnection fault, where M is a positive integer greater than 2 and less than the second number.

[0009] In some implementations, during the boost phase, the first relay, the second relay, and the third relay are in a closed state, and the fault detection process performed during the boost phase includes: In each of the third number of detection cycles during the boost phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay and the second terminal of the second relay is acquired as the current first voltage of that detection cycle. If, within the third number of detection cycles, the current second voltage is greater than the second threshold voltage for M1 consecutive detection cycles and the difference between the current second voltage and the current first voltage for the M1 consecutive detection cycles is greater than the third threshold voltage, it is determined that the first relay and / or the second relay has an abnormal disconnection fault, where M1 is a positive integer greater than 2 and less than the third number. and / or In each of the fourth number of detection cycles during the boost phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle. If, within the fourth number of detection cycles, the difference between the current second voltage and the output voltage of the charging pile is greater than the fourth threshold voltage for P consecutive detection cycles, it is determined that the third relay has experienced an abnormal disconnection fault, where P is a positive integer greater than 2 and less than the fourth number.

[0010] In some implementations, during the discharge phase, the third relay is in an open state, and the first and second relays are in a closed state. The fault detection process performed during the discharge phase includes: In each of the fifth detection cycles during the discharge phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle. If, within the fifth number of detection cycles, the difference between the current second voltage and the output voltage of the charging pile is less than the fifth threshold voltage for P1 consecutive detection cycles, the third relay is determined to have a sticking fault; where P1 is a positive integer greater than 2 and less than the fifth number. And / or, In each of the sixth detection cycles during the discharge phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay and the second terminal of the second relay is acquired as the current first voltage of that detection cycle. If, within the sixth number of detection cycles, the current second voltage is greater than the sixth threshold voltage for M2 consecutive detection cycles, and the difference between the current second voltage and the current first voltage for the M2 consecutive detection cycles is greater than the seventh threshold voltage, it is determined that the first relay and / or the second relay has an abnormal disconnection fault, where M2 is a positive integer greater than 2 and less than the sixth number.

[0011] In some embodiments, the boost sub-circuit includes; Multiple inverter units are provided, each including a winding, a positive switching element, and a negative switching element. The positive and negative switching elements are connected in series between the positive and negative output terminals of the boost sub-circuit. A common node is shared between the positive and negative switching elements. The positive switching element is connected between the positive output terminal of the boost sub-circuit and the common node, and the negative switching element is connected between the common node and the negative output terminal of the boost sub-circuit. The winding is connected between the second terminal of the first relay and the common node. The number of the plurality of inverter units is the same as the number of phases of the voltage provided by the charging pile.

[0012] In some embodiments, the boost sub-circuit further includes a second capacitor connected between the positive and negative output terminals of the boost sub-circuit.

[0013] In some implementations, during the preparation phase, the positive switching element in each inverter unit is controlled to be turned on with a first duty cycle, and the negative switching element in each inverter unit is controlled to be turned off. During the pre-charge phase, the positive switching element in each inverter unit is controlled to be turned on with a second duty cycle, and the negative switching element in each inverter unit is controlled to be turned off. During the boost phase, the negative switching element in each inverter unit is controlled to be turned on with a third duty cycle, and the positive switching element in each inverter unit is controlled to be turned off. During the discharge phase, the negative switching element in each inverter unit is controlled to be turned on with a fourth duty cycle, and the positive switching element in each inverter unit is controlled to be turned off.

[0014] According to a second aspect of this application, a relay fault detection device is provided, the device including a motor controller that performs the steps of the relay fault detection method described above.

[0015] According to a third aspect of this application, the vehicle includes the relay fault detection device described above.

[0016] The relay fault detection method of this application includes: for each of the preparation stage, pre-charge stage, boost stage, and discharge stage, in each of a plurality of detection cycles in that stage, acquiring at least one of a first voltage between the second terminal of the first relay and the second terminal of the second relay, and a second voltage between the second terminal of the third relay and the first terminal of the second relay; based on at least one of the first voltage and the second voltage acquired in each of the plurality of detection cycles, performing fault detection on the first relay, the second relay, and / or the third relay during that stage. The relay fault detection method provided by this application only requires two voltage sensors to acquire two voltages to complete the detection of relay faults during the boost process, reducing vehicle manufacturing costs and the complexity of the detection logic. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a circuit diagram illustrating a boost charging circuit according to an embodiment of this application; Figure 2 This is a flowchart illustrating the steps of a relay fault detection method according to an embodiment of this application; Figure 3 This is a circuit diagram illustrating another boost charging circuit according to an embodiment of this application; Figure 4 This is a schematic diagram illustrating the system architecture of an embodiment of this application.

[0019] Explanation of reference numerals in the attached diagram: charging pile 10, battery to be charged 20, boost charging circuit 100, first relay K1, second relay K2, third relay K3, first capacitor C1, first inductor L1, boost sub-circuit 110, positive switch element S1, negative switch element S2, winding L, second capacitor C2, common node A. Detailed Implementation

[0020] To make the above and other features and advantages of this application clearer, the application is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explanation to those skilled in the art, and are exemplary only, not restrictive.

[0021] In the following description, numerous specific details are set forth to provide a thorough understanding of this application. However, it will be apparent to those skilled in the art that the specific details are not required to practice this application. In other instances, well-known steps or operations have not been described in detail to avoid obscuring this application.

[0022] This application provides a relay fault detection method.

[0023] The relay fault detection method provided in this application will be described in detail below with reference to the accompanying drawings, through specific embodiments and application scenarios.

[0024] The relay fault detection method provided in this application embodiment is used to detect faults in the relays (first relay K1, second relay K2, and third relay K3) of the boost charging circuit 100 during the charging process in which the charging pile 10 charges the battery 20 to be charged through the boost charging circuit.

[0025] See Figure 1The boost charging circuit 100 includes a first relay K1, a second relay K2, a third relay K3, a first capacitor C1, a first inductor L1, and a boost sub-circuit 110. The positive and negative terminals of the charging pile 10 are respectively connected to the first terminals of the third relay K3 and the second relay K2. The second terminal of the third relay K3 is connected to the first terminal of the first relay K1 via the first inductor L1. The first capacitor C1 is connected between the second terminal of the third relay K3 and the first terminal of the second relay K2. The second terminals of the first relay K1 and the second relay K2 are respectively connected to the positive and negative input terminals of the boost sub-circuit 110. The boost sub-circuit 110 is connected to the battery 20 to be charged.

[0026] exist Figure 1 In the circuit, the positive output terminal and the negative output terminal of the boost circuit 110 are connected to the positive terminal and the negative terminal of the battery to be charged 20, respectively; the boost circuit 110 is used to boost the voltage input from its positive input terminal and the negative input terminal and then output it from its positive output terminal and the negative output terminal.

[0027] The charging process sequentially includes a preparation stage (as the beginning), a pre-charge stage, a voltage boost stage, and a discharge stage (as the end). For example... Figure 2 As shown, for each of the preparation phase, pre-charge phase, boost phase, and discharge phase, a fault detection process is performed during that phase, the fault detection process including: Step 101: In each of the multiple detection cycles in this stage, acquire at least one of the first voltage between the second terminal of the first relay K1 and the second terminal of the second relay K2 and the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2.

[0028] Here, the first voltage and the second voltage can be acquired by a voltage sensor respectively.

[0029] Step 102: Based on at least one of the first voltage and the second voltage obtained in each of the plurality of detection cycles, perform fault detection on the first relay, the second relay and / or the third relay during this phase.

[0030] The detection logic relies on the relay's expected on / off state and corresponding expected voltage value during a specific charging phase. By comparing the actual measured voltage with a preset threshold, it can be determined whether the relay is abnormal. For example, if the voltage difference across the relay is much smaller than the expected voltage in the off state when the relay should be in the off state, it may indicate that the relay is stuck; conversely, if there is a significant voltage difference across the relay when the relay should be in the on state, it may indicate that the relay is abnormally disconnected.

[0031] The relay fault detection process at different charging stages will be described in further detail below.

[0032] (1) Fault detection during the preparation phase During the preparation phase, the charging system is typically in its initial state. At this time, the first relay K1, the second relay K2, and the third relay K3 should all be in the off state. The main purpose of this phase is to ensure that the first relay K1 and the second relay K2 are in a normal, unblocked state before and after the boost charging process begins. If the first relay K1 and / or the second relay K2 become stuck after the boost charging process is completed, it will affect the normal driving of the vehicle.

[0033] The fault detection process is performed during the preparation phase, specifically including: In the first detection cycle of the preparation phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is obtained as the reference second voltage for the first detection cycle; In each of the first number of detection cycles during the preparation phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is continuously acquired as the current second voltage of that detection cycle. If, within the first number of detection cycles, the difference between the current second voltage and the second voltage of the first detection cycle is greater than the first threshold voltage for N consecutive detection cycles, then the first relay K1 and / or the second relay K2 are determined to have a sticking fault. Here, N is a positive integer greater than 2 and less than the first number.

[0034] Here, the first number of detection cycles can be multiple consecutive detection cycles following the first detection cycle. The values ​​of the first number and N can be calibrated according to the fault strategy requirements and bench test results. For example, the first number can be 50, and N can be 4. The first threshold voltage can be 30V. When specifically selecting the value of the first threshold voltage, it must be ensured that it is much smaller than the voltage output by the battery 20 to be charged, and greater than a certain value. If the first threshold voltage is close to the voltage output by the battery 20 to be charged, then when an adhesion fault occurs, the difference between the current second voltage and the second voltage of the first detection cycle may not reach the first threshold voltage, thus failing to meet the fault triggering condition. If the value of the first threshold voltage is too small, it may cause false fault triggering due to high-voltage environmental interference.

[0035] During the preparation phase, if the first relay K1 and / or the second relay K2 become stuck together, the voltage (or a portion thereof) of the charging pile 10 may be reflected across the first capacitor C1 through the feedback path of the stuck relays and the boost circuit 110, thus directly or indirectly affecting the second voltage. If the first relay K1 and / or the second relay K2 become stuck together, it will cause a significant difference between the second voltage and the initial value. This is addressed by judging the voltage over N consecutive detection cycles to avoid momentary interference.

[0036] (2) Fault detection during the pre-charging stage During the pre-charging phase, the first relay K1 and the second relay K2 are in the closed state, while the third relay K3 is in the open state. The main purpose of this phase is to pre-charge the first capacitor C1 to near the output voltage of the charging pile 10 through the battery to be charged 20, so as to prevent the third relay K3 from being damaged due to excessive voltage difference across the third relay K3 when it is closed.

[0037] A fault detection process is performed during the pre-charge phase, specifically including: In each of the second number of detection cycles during the pre-charge phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is obtained as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay K1 and the second terminal of the second relay K2 is obtained as the current first voltage of that detection cycle. If, within the second number of detection cycles, the current second voltage is greater than the second threshold voltage for M consecutive detection cycles, and the difference between the current second voltage and the current first voltage for the M consecutive detection cycles is greater than the third threshold voltage, then it is determined that the first relay K1 and / or the second relay K2 has experienced an abnormal disconnection fault. Here, M is a positive integer greater than 2 and less than the second number.

[0038] Here, the values ​​of the second number and M can be calibrated according to the fault strategy requirements and bench test results. Specifically, the second number can be 50, and M can be 8. The second threshold voltage can be 50V, and the third threshold voltage can be 30V. Similar to the first threshold voltage, the second and third threshold voltages must be significantly lower than the voltage output by the battery 20 to be charged, but greater than a certain value. If the second threshold voltage is close to the voltage output by the battery 20 to be charged, the current second voltage will not reach the second threshold voltage when an abnormal disconnection fault occurs, thus failing to meet the fault triggering condition. If the second threshold voltage is too small, it may cause false fault triggering due to high-voltage environmental interference.

[0039] If the third threshold voltage is close to the voltage output by the battery 20 to be charged, then in the event of an abnormal disconnection fault, the difference between the current second voltage and the current first voltage will not reach the third threshold voltage, thus failing to meet the fault triggering condition. If the value of the third threshold voltage is too small, it may cause false fault triggering due to interference from a high-voltage environment.

[0040] During the pre-charge phase, the first relay K1 and the second relay K2 should be closed, so the first voltage (input voltage of the boost circuit 110) should be close to the second voltage (passing through the first inductor L1 and the first capacitor C1). During the pre-charge phase, the third relay K3 is open, and the voltage across the first capacitor C1 is provided by the battery to be charged. If the first relay K1 and / or the second relay K2 are abnormally open, a large voltage drop will occur across these two relays. If the current second voltage is greater than the second threshold voltage, and the difference between the current second voltage and the current first voltage (i.e., the total voltage drop across the first relay K1 and the second relay K2) is greater than the third threshold voltage, it indicates that an abnormal voltage drop exists. Combined with the setting that the relays should be closed during the pre-charge phase, this indicates that the abnormal opening has occurred.

[0041] (3) Fault detection during the boost phase During the boost phase, the first relay K1, the second relay K2, and the third relay K3 are all in the closed state. This phase requires simultaneous detection of abnormal disconnection faults in the first relay K1 and / or the second relay K2, as well as the third relay K3. The main purpose of this phase is to calculate the boost charging duty cycle using the output voltage of the charging pile 10 and the actual voltage of the battery 20 to be charged, thereby boosting the output voltage of the charging pile 10.

[0042] A fault detection process is performed during the boost phase, specifically including: For abnormal disconnection of the first relay K1 and / or the second relay K2: In each of the third number of detection cycles during the boost phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is acquired as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay K1 and the second terminal of the second relay K2 is acquired as the current first voltage of that detection cycle; if the current second voltage is greater than the second threshold voltage for M1 consecutive detection cycles within the third number of detection cycles, and the difference between the current second voltage and the current first voltage for the M1 consecutive detection cycles is greater than the third threshold voltage, then it is determined that the first relay K1 and / or the second relay K2 has experienced an abnormal disconnection fault. Wherein M1 is a positive integer greater than 2 and less than the third number.

[0043] Here, the values ​​of the third threshold voltage and M1 can be calibrated according to the fault strategy requirements and bench test results. Specifically, the third threshold voltage can be 50, and M1 can be 8. Specifically, the second threshold voltage can be 50V, and the third threshold voltage can be 30V.

[0044] Similar to the pre-charging stage, during the boost stage, the first relay K1 and the second relay K2 should be closed. If they are abnormally disconnected, a significant voltage difference will occur between the first voltage (input of the boost sub-circuit) and the second voltage (output of the charging pile). The judgment logic is the same as that in the pre-charging stage.

[0045] Regarding the abnormal disconnection of the third relay K3: In each of the fourth number of detection cycles during the boost phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is acquired as the current second voltage for that detection cycle; if the difference between the current second voltage and the output voltage of the charging pile 10 is greater than the fourth threshold voltage for P consecutive detection cycles within the fourth number of detection cycles, then the third relay K3 is determined to have experienced an abnormal disconnection fault. Here, P is a positive integer greater than 2 and less than the fourth number.

[0046] Here, the values ​​of the fourth threshold voltage and P can be calibrated according to the fault strategy requirements and bench test results. Specifically, the fourth threshold voltage can be 50, and M1 can be 8. The fourth threshold voltage can be 30V. When specifically selecting the value of the fourth threshold voltage, it must be ensured to be much smaller than the output voltage of the charging pile 10, and greater than a certain value. If the fourth threshold voltage is close to the output voltage of the charging pile 10, the difference between the current second voltage and the output voltage of the charging pile 10 may not reach the fourth threshold voltage when an adhesion fault occurs, thus failing to meet the fault triggering condition. If the value of the fourth threshold voltage is too small, it may cause false fault triggering due to high-voltage environmental interference.

[0047] During the boost phase, the third relay K3 should be closed, therefore the voltage difference between its two ends (i.e., between the positive output terminal of the charging pile and the second terminal of the third relay K3) should be close to 0. If the third relay K3 is abnormally opened, there will be a large voltage drop across it, causing a significant difference between the second voltage and the actual output voltage of the charging pile 10 (which can be obtained from the control command or internal sampling of the charging pile 10). The fourth threshold voltage is used to determine whether this significant difference has occurred.

[0048] (4) Fault detection during the discharge phase During the discharge phase, the third relay K3 is in the open state, while the first relay K1 and the second relay K2 are in the closed state. The main purpose of this phase is to discharge the first capacitor C1 after the boost charging of the battery 20 is completed, so as to avoid high voltage remaining in the boost charging circuit 100 when exiting the boost charging phase.

[0049] The fault detection process is performed during the discharge phase, specifically including: Regarding the adhesion fault of the third relay K3: In each of the fifth number of detection cycles during the discharge phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is acquired as the current second voltage of that detection cycle; if the difference between the current second voltage and the output voltage of the charging pile 10 is less than the fifth threshold voltage (e.g., close to 0) for P1 consecutive detection cycles within the fifth number of detection cycles, then the third relay K3 is determined to have an adhesion fault. Here, P1 is a positive integer greater than 2 and less than the fifth number.

[0050] Here, the values ​​of the fifth threshold voltage and P1 can be calibrated according to the fault strategy requirements and bench test results. Specifically, the fifth threshold voltage can be 50, and P1 can be 30. The fifth threshold voltage can be 30V. When specifically selecting the value of the fifth threshold voltage, it must be ensured to be much smaller than the output voltage of the charging pile 10, and greater than a certain value. If the fifth threshold voltage is close to the output voltage of the charging pile 10, then when an adhesion fault occurs, the difference between the current second voltage and the output voltage of the charging pile 10 will always meet the condition of being less than the fifth threshold voltage, causing a false fault trigger. If the value of the fifth threshold voltage is too small, the fault triggering condition may never be met, thus causing the fault detection to fail.

[0051] During the discharge phase, the third relay K3 should be in the open state. Therefore, the output of the charging pile 10 should be disconnected from the input side of the boost charging circuit 100, resulting in a voltage of 0 input to the boost charging circuit. The second voltage should be significantly different from the output voltage of the charging pile 10. At the beginning of the discharge phase, when the third relay K3 is just opened, the second voltage and the output voltage of the charging pile are still basically the same. After the discharge begins, the second voltage will drop rapidly (e.g., within tens of milliseconds) to below a certain voltage (e.g., 60V). If the third relay K3 is stuck, the output voltage of the charging pile 10 may be partially or completely transferred to the measurement position of the second voltage, resulting in an abnormally small difference between the current second voltage and the output voltage of the charging pile 10 (close to 0), thus indicating a sticking fault.

[0052] For abnormal disconnection faults of the first relay K1 and / or the second relay K2: In each detection cycle of the sixth number of detection cycles during the discharge phase, the second voltage between the second terminal of the third relay K3 and the first terminal of the second relay K2 is acquired as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay K1 and the second terminal of the second relay K2 is acquired as the current first voltage of that detection cycle; If, within the sixth number of detection cycles, the current second voltage is greater than the sixth threshold voltage for M2 consecutive detection cycles, and the difference between the current second voltage and the current first voltage for the M2 consecutive detection cycles is greater than the seventh threshold voltage, then it is determined that the first relay K1 and / or the second relay K2 has experienced an abnormal disconnection fault. Where M2 is a positive integer greater than 2 and less than the sixth number.

[0053] Here, the values ​​of the sixth threshold voltage and M2 can be calibrated according to the fault strategy requirements and bench test results. Specifically, the sixth threshold voltage can be 50, and M2 can be 6. Specifically, the sixth threshold voltage can be 50V, and the seventh threshold voltage can be 30V.

[0054] The sixth threshold voltage must be significantly lower than the output voltage of the charging pile 10, but greater than a certain value. If the sixth threshold voltage is close to the output voltage of the charging pile 10, the current second voltage may not reach the sixth threshold voltage in the event of an abnormal disconnection fault, thus failing to meet the fault triggering conditions. If the value of the sixth threshold voltage is too small, it may cause false fault triggering due to interference from the high-voltage environment.

[0055] The seventh threshold voltage must be significantly lower than the output voltage of the charging pile 10, but also greater than a certain value. If the seventh threshold voltage is close to the output voltage of the charging pile 10, the difference between the current second voltage and the current first voltage will always be less than the seventh threshold voltage in the event of an abnormal disconnection fault, causing fault detection to fail. If the value of the seventh threshold voltage is too small, it may cause false fault triggering due to interference from high-voltage environments.

[0056] During the discharge phase, the first relay K1 and the second relay K2 should be in the closed state. If they are abnormally disconnected, the detection logic is similar to that of the pre-charge and boost phases. If the current second voltage is greater than the sixth threshold voltage, and the difference between the second voltage and the first voltage is greater than the seventh threshold voltage, it indicates that there is an abnormal voltage drop in K1 and / or K2, and it is determined to be an abnormal disconnection.

[0057] The method in this embodiment solves the problem that during the boost charging process, relay sticking or abnormal disconnection may occur, which may lead to the inability to perform normal boost charging and the possible abnormal motor drive phenomena.

[0058] The method in this embodiment only requires two voltage sensors to collect two voltages, which can complete the detection of relay faults during the voltage boosting process, reducing vehicle manufacturing costs and the complexity of the detection logic.

[0059] Further, see Figure 3 The boost sub-circuit 110 includes multiple inverter units, each of which includes a winding L, a positive switching element S1, and a negative switching element S2. The positive switching element S1 and the negative switching element S2 are connected in series between the positive output terminal and the negative output terminal of the boost sub-circuit 110. The positive switching element S1 and the negative switching element S2 have a common node A. The positive switching element S1 is connected between the positive output terminal of the boost sub-circuit 110 and the common node A, and the negative switching element S2 is connected between the common node A and the negative output terminal of the boost sub-circuit 110. The winding L is connected between the second terminal of the first relay K1 and the common node A. The number of the multiple inverter units is the same as the number of phases of the voltage provided by the charging pile 10.

[0060] Further, see Figure 3 The boost circuit 110 can also be understood as including a three-phase motor winding and a three-phase inverter unit. The winding L in each inverter unit forms the three-phase motor winding, the positive switching element S1 in each inverter unit forms the upper bridge of the three-phase inverter unit, and the negative switching element S2 in each inverter unit forms the lower bridge of the three-phase inverter unit. Each phase winding is connected to the common node A between the corresponding positive switching element S1 and negative switching element S2 through a neutral node.

[0061] The boost sub-circuit 110 also includes a second capacitor C2; the second capacitor C2 is connected between the positive output terminal and the negative output terminal of the boost sub-circuit 100.

[0062] exist Figure 3 In the circuit shown, the second voltage is actually the voltage across the first capacitor C1. The first voltage is the voltage across the first capacitor C1 when the first relay K1 and the second relay K2 are closed; it is the voltage across the second capacitor C2 when the first relay K1 and the second relay K2 are open and the upper bridge of the three-phase inverter unit is conducting; and it is 0 when the first relay K1 and the second relay K2 are open and the upper bridge of the three-phase inverter unit is disconnected.

[0063] During the preparation phase, the positive switching element S1 in each inverter unit is controlled to be turned on with a first duty cycle, and the negative switching element S2 in each inverter unit is controlled to be turned off. Here, the first duty cycle can be calibrated by bench testing, for example, it can be set to 0.02.

[0064] During the pre-charge phase, the positive terminal switching element S1 in each inverter unit is controlled to be turned on with a second duty cycle, and the negative terminal switching element S2 in each inverter unit is controlled to be turned off. Here, the second duty cycle can be bench-calibrated using the voltage difference between the voltage of the battery 20 to be charged and the voltage across the first capacitor C1. The second duty cycle increases as the voltage difference decreases; this is to prevent excessively rapid pre-charging from affecting the lifespan of the first capacitor C1. The second duty cycle for this stage can be set as follows: 0.019 when the voltage difference is 180~1000V, 0.029 when the voltage difference is 130~180V, 0.039 when the voltage difference is 90~130V, 0.05 when the voltage difference is 60~90V, 0.059 when the voltage difference is 40~60V, 0.07 when the voltage difference is 20~40V, 0.079 when the voltage difference is 10~20V, 0.1 when the voltage difference is 5~10V, and 0.119 when the voltage difference is 0~5V.

[0065] During the boost phase, the negative switch element S2 in each inverter unit is controlled to conduct with a third duty cycle, and the positive switch element S1 in each inverter unit is controlled to de-energize. Here, the third duty cycle can be calculated using a theoretical formula, as follows: D = 1 - (V chrgPile / V target That is, the third duty cycle, according to the principle of power conservation, can be determined by I. ChrgOut = I Bstreq ·V dc / V chrgPile The required input current of the current charging pile 10 is calculated, and then PI control is performed based on the required input current and the actual feedback current to obtain the third duty cycle.

[0066] During the discharge phase, the negative switch element S2 in each inverter unit is controlled to be turned on with a fourth duty cycle, and the positive switch element S1 in each inverter unit is controlled to be turned off. Here, the fourth duty cycle can be calibrated by bench testing, for example, it can be set to 0.06.

[0067] The relay fault detection process will be described in detail below based on the above content.

[0068] The boost charging process consists of four stages: preparation stage, pre-charge stage, boost stage, and discharge stage.

[0069] Step 1: In the preparation stage, the positive switching element S1 in each inverter unit is turned on with a first duty cycle. Step 2: At the sampling update time, voltage sensor V2 collects the value of the second voltage; Step 3: If N consecutive cycles of V are detected within 50 cycles 2FirstPeriod -V 2NowPeriod If the voltage is >30V, it is considered that the first and second relays have a sticking fault; otherwise, it is considered that no sticking fault has occurred. Among them, V 2FirstPeriod V is the voltage value collected by voltage sensor V2 in the first cycle. 2NowPeriod The voltage value collected by voltage sensor V2 in the current cycle; Step 4: During the pre-charge stage, the positive switch element S1 in each inverter unit is turned on with a second duty cycle, and the first relay K1 and the second relay K2 are closed. Step 5: At the sampling update time, voltage sensor V1 collects the value of the first voltage, and voltage sensor V2 collects the value of the second voltage; Step 6: If V is detected in N cycles within 50 cycles... 2NowPeriod >50V and |V 2NowPeriod -V 1NowPeriod If the voltage is greater than 30V, then the first relay K1 and the second relay K2 are considered to have an abnormal disconnection fault; otherwise, it is considered that no abnormal disconnection fault has occurred. Among them, V 1NowPeriod This represents the voltage value collected by voltage sensor V1 in the current cycle. Step 7: During the boost phase, control the third relay K3 to close, and control the negative switch element S2 in each inverter unit to conduct with the third duty cycle; Step 8: At the sampling update time, voltage sensor V1 collects the value of the first voltage, and voltage sensor V2 collects the value of the second voltage; Step 9: Receive the output voltage of the charging pile through the communication protocol between the MCU and BMS; Step 10: The fault detection method for abnormal disconnection of the first relay K1 and the second relay K2 is the same as that in the pre-charge stage; if |V is detected in N cycles within 50 cycles... 2NowPeriod -V ChrgPile If the voltage is greater than 30V, then the third relay K3 is considered to have an abnormal disconnection fault; otherwise, it is considered that no abnormal disconnection fault has occurred. Among them, V ChrgPile This refers to the output voltage of the charging station. Step 11: During the discharge phase, the third relay K3 is disconnected, and the negative switch element S2 in each inverter unit is turned on with the fourth duty cycle. Step 12: At the sampling update time, voltage sensor V1 collects the value of the first voltage, and voltage sensor V2 collects the value of the second voltage; Step 13: If |V is detected within N consecutive periods ChrgPile-V 2NowPeriod If |<30V, then the third relay K3 is considered to have a sticking fault; otherwise, it is considered not to have a sticking fault. If V is detected for N consecutive cycles... 2NowPeriod >50V and |V 2NowPeriod -V 1NowPeriod If the voltage is greater than 30V, then the first relay K1 and the second relay K2 are considered to have an abnormal disconnection fault; otherwise, it is considered that no abnormal disconnection fault has occurred. Step 14: When the first capacitor C1 discharges to below 60V, the first relay K1 and the second relay K2 are disconnected. Step 15: Execute the control logic of the preparation stage to determine whether the first relay K1 and the second relay K2 are stuck together.

[0070] The relay fault detection method in this embodiment can be executed by the motor control unit. Specifically, see [link to documentation]. Figure 4 The motor control unit (motor controller) is connected to the battery to be charged, the three-phase inverter unit (including six SiC modules: SiC module 01, SiC module 02, SiC module 03, SiC module 04, SiC module 05, and SiC module 06), the three-phase windings of the motor, the first relay, the second relay, the first inductor, the first capacitor, the third relay, and the charging pile in the boost charging circuit 100. The motor controller controls the on / off state of the three-phase inverter unit by sending commands with a certain duty cycle to the SiC modules of the three-phase inverter unit, and uses the three-phase windings and the external first inductor to store energy, thereby realizing the boost function.

[0071] This embodiment of the method, by equipping the boost charging circuit 100 with two voltage sensors and using a relatively simple judgment strategy, can realize the detection of relay faults during the boost charging process, and then perform post-fault processing after the relay has stuck or abnormally disconnected.

[0072] This application also provides a relay fault detection device, the device including a motor controller, the motor controller performing the steps of the relay fault detection method described in any of the above claims.

[0073] This application also provides a vehicle that includes the relay fault detection device described above.

[0074] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A relay fault detection method, characterized in that, For fault detection of a relay in a boost charging circuit during the charging process where a charging pile charges a battery via the boost charging circuit, the charging process sequentially includes a preparation stage (as the start stage), a pre-charge stage, a boost stage, and a discharge stage (as the end stage). The boost charging circuit includes a first relay, a second relay, a third relay, a first capacitor, a first inductor, and a boost sub-circuit. The positive and negative terminals of the charging pile are respectively connected to the first terminals of the third relay and the second relay. The second terminal of the third relay is connected to the first terminal of the first relay via the first inductor. The first capacitor is connected between the second terminal of the third relay and the first terminal of the second relay. The second terminals of the first relay and the second relay are respectively connected to the positive and negative input terminals of the boost sub-circuit, which is connected to the battery to be charged. The method includes: For each of the preparation phase, pre-charge phase, boost phase, and discharge phase, a fault detection process is performed during that phase, the fault detection process including: In each of the multiple detection cycles in this phase, at least one of the first voltage between the second terminal of the first relay and the second terminal of the second relay and the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired; Based on at least one of the first voltage and the second voltage obtained in each of the plurality of detection cycles, fault detection is performed on the first relay, the second relay and / or the third relay during the phase.

2. The relay fault detection method according to claim 1, characterized in that, During the preparation phase, the first relay and the second relay are in the open state. The fault detection process performed during the preparation phase includes: During the first detection cycle of the preparation phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is obtained as the second voltage of the first detection cycle. In each of the first number of detection cycles during the preparation phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle. If, within the first number of detection cycles, the difference between the current second voltage and the second voltage of the first detection cycle is greater than the first threshold voltage for N consecutive detection cycles, it is determined that the first relay and / or the second relay has a sticking fault, where N is a positive integer greater than 2 and less than the first number.

3. The relay fault detection method according to claim 1, characterized in that, During the pre-charging phase, the first and second relays are in the closed state, and the third relay is in the open state. The fault detection process performed during the pre-charging phase includes: In each of the second number of detection cycles during the pre-charge phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is obtained as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay and the second terminal of the second relay is obtained as the current first voltage of that detection cycle. If, within the second number of detection cycles, the current second voltage is greater than the second threshold voltage for M consecutive detection cycles, and the difference between the current second voltage and the current first voltage for the M consecutive detection cycles is greater than the third threshold voltage, it is determined that the first relay and / or the second relay has an abnormal disconnection fault, where M is a positive integer greater than 2 and less than the second number.

4. The relay fault detection method according to claim 1, characterized in that, During the boost phase, the first relay, the second relay, and the third relay are in the closed state. The fault detection process performed during the boost phase includes: In each of the third number of detection cycles during the boost phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay and the second terminal of the second relay is acquired as the current first voltage of that detection cycle. If, within the third number of detection cycles, the current second voltage is greater than the second threshold voltage for M1 consecutive detection cycles and the difference between the current second voltage and the current first voltage for the M1 consecutive detection cycles is greater than the third threshold voltage, it is determined that the first relay and / or the second relay has an abnormal disconnection fault, where M1 is a positive integer greater than 2 and less than the third number. and / or In each of the fourth number of detection cycles during the boost phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle. If, within the fourth number of detection cycles, the difference between the current second voltage and the output voltage of the charging pile is greater than the fourth threshold voltage for P consecutive detection cycles, it is determined that the third relay has experienced an abnormal disconnection fault, where P is a positive integer greater than 2 and less than the fourth number.

5. The relay fault detection method according to claim 1, characterized in that, During the discharge phase, the third relay is in the open state, and the first and second relays are in the closed state. The fault detection process performed during the discharge phase includes: In each of the fifth detection cycles during the discharge phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle. If, within the fifth number of detection cycles, the difference between the current second voltage and the output voltage of the charging pile is less than the fifth threshold voltage for P1 consecutive detection cycles, the third relay is determined to have a sticking fault; where P1 is a positive integer greater than 2 and less than the fifth number. And / or, In each of the sixth detection cycles during the discharge phase, the second voltage between the second terminal of the third relay and the first terminal of the second relay is acquired as the current second voltage of that detection cycle, and the first voltage between the second terminal of the first relay and the second terminal of the second relay is acquired as the current first voltage of that detection cycle. If, within the sixth number of detection cycles, the current second voltage is greater than the sixth threshold voltage for M2 consecutive detection cycles, and the difference between the current second voltage and the current first voltage for the M2 consecutive detection cycles is greater than the seventh threshold voltage, it is determined that the first relay and / or the second relay has an abnormal disconnection fault, where M2 is a positive integer greater than 2 and less than the sixth number.

6. The relay fault detection method according to claim 1, characterized in that, The boost sub-circuit includes: Multiple inverter units are provided, each including a winding, a positive switching element, and a negative switching element. The positive and negative switching elements are connected in series between the positive and negative output terminals of the boost sub-circuit. A common node is shared between the positive and negative switching elements. The positive switching element is connected between the positive output terminal of the boost sub-circuit and the common node, and the negative switching element is connected between the common node and the negative output terminal of the boost sub-circuit. The winding is connected between the second terminal of the first relay and the common node. The number of the plurality of inverter units is the same as the number of phases of the voltage provided by the charging pile.

7. The relay fault detection method according to claim 6, characterized in that, The boost sub-circuit also includes a second capacitor; the second capacitor is connected between the positive output terminal and the negative output terminal of the boost sub-circuit.

8. The relay fault detection method according to claim 6, characterized in that, During the preparation phase, the positive switching element in each inverter unit is controlled to be turned on with a first duty cycle, and the negative switching element in each inverter unit is controlled to be turned off. During the pre-charge phase, the positive switching element in each inverter unit is controlled to be turned on with a second duty cycle, and the negative switching element in each inverter unit is controlled to be turned off. During the boost phase, the negative switching element in each inverter unit is controlled to be turned on with a third duty cycle, and the positive switching element in each inverter unit is controlled to be turned off. During the discharge phase, the negative switching element in each inverter unit is controlled to be turned on with a fourth duty cycle, and the positive switching element in each inverter unit is controlled to be turned off.

9. A relay fault detection device, characterized in that, The device includes a motor controller that performs the steps of the relay fault detection method as described in any one of claims 1 to 8.

10. A vehicle, characterized in that, The vehicle includes the relay fault detection device as described in claim 9.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the relay fault detection method according to any one of claims 1 to 8.

12. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the relay fault detection method according to any one of claims 1 to 8.

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