Power battery insulation detection method and detection device, battery management system and vehicle

Abstract

The application discloses a power battery insulation detection method and device, a battery management system and a vehicle. The power battery insulation detection method is used for an insulation detection circuit. The insulation detection circuit comprises a first voltage dividing unit, a second voltage dividing unit, a third voltage dividing unit and a fourth voltage dividing unit. The insulation detection circuit further comprises a separation switch and a switching switch. The power battery insulation detection method comprises the following steps: when the separation switch is in a closed state, a first voltage detection value between the fourth voltage dividing unit is obtained; it is determined that the first voltage detection value meets an abnormal threshold condition; the separation switch and the switching switch are both controlled to be disconnected, and a second voltage detection value between the fourth voltage dividing unit is obtained; and a fault state of the insulation detection circuit is determined according to the second voltage detection value. The method and the device can accurately identify the fault state of the insulation detection circuit, avoid false positives or false negatives of insulation alarms, and improve the insulation detection reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicles, in particular to a power battery insulation detection method, a power battery insulation detection device, a battery management system and a vehicle. BACKGROUND

[0002] The voltage range of the power battery is generally a B-grade voltage platform, which is far beyond the safe voltage that can be borne by human beings. The complex working environment of the vehicle can cause the insulation performance between the power battery and the vehicle chassis to decrease, and in severe cases, can cause safety accidents such as electric leakage and fire, which pose a threat to the safety of the driver and passengers. Therefore, it is of great significance to improve the safety of the electric vehicle to accurately detect the insulation resistance of the power battery of the electric vehicle in real time.

[0003] At present, some schemes use a non-balanced bridge method insulation detection device to detect the insulation of the power battery. However, if the detection channel of the detection device fails, the insulation resistance of the power battery cannot be accurately detected, which can cause the situation of missed or false insulation alarm. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the prior art. To this end, one object of the present application is to provide a power battery insulation detection method, which can accurately identify the failure of the power battery insulation detection circuit and avoid missed or false insulation detection of the power battery, thereby improving the reliability of the insulation detection.

[0005] A second object of the present application is to provide a power battery insulation detection device.

[0006] A third object of the present application is to provide a battery management system.

[0007] A fourth object of the present application is to provide a vehicle.

[0008] To achieve the above object, the power battery insulation detection method according to an embodiment of the present application is used for an insulation detection circuit, the insulation detection circuit comprises a first voltage dividing unit, a second voltage dividing unit, a third voltage dividing unit and a fourth voltage dividing unit, a first end of the first voltage dividing unit is connected with a positive electrode end of a power battery, a second end of the first voltage dividing unit is connected with a first end of the second voltage dividing unit, a second end of the second voltage dividing unit is connected with a first end of the third voltage dividing unit, a second end of the third voltage dividing unit is connected with a first end of the fourth voltage dividing unit, a second end of the fourth voltage dividing unit is connected with a negative electrode end of the power battery, a first node is formed between the second end of the first voltage dividing unit and the first end of the second voltage dividing unit, the first node is connected with the negative electrode end of the power battery through a switching switch, a second node is formed between the second end of the second voltage dividing unit and the first end of the third voltage dividing unit, the second node is connected with a vehicle body ground through a separation switch; the power battery insulation detection method comprises: acquiring a first voltage detection value between two ends of the fourth voltage dividing unit when the separation switch is in a closed state; determining that the first voltage detection value meets an abnormal threshold condition; controlling the separation switch and the switching switch to be both disconnected, acquiring a second voltage detection value between two ends of the fourth voltage dividing unit; and determining a fault state of the insulation detection circuit according to the second voltage detection value.

[0009] According to the power battery insulation detection method, when the first voltage detection value detected by the insulation detection circuit is abnormal, instead of directly determining that the insulation between the power battery and the vehicle body ground is abnormal, the separation switch is controlled to be disconnected and the second voltage detection value is acquired, and then whether the insulation detection circuit is faulty and what kind of fault is determined based on the second voltage detection value, so that the fault of the insulation detection circuit and the real insulation alarm can be more accurately identified, the false alarm or the false report of the insulation alarm is avoided, and the reliability of the insulation detection is improved.

[0010] In some embodiments, the determination that the first voltage detection value meets the abnormal threshold condition comprises: determining that the first voltage detection value is less than a first voltage threshold.

[0011] In some embodiments, the determination of the fault state of the insulation detection circuit according to the second voltage detection value comprises: if the second voltage detection value is less than a first confirmation voltage threshold, determining that a short circuit occurs between two ends of the fourth voltage dividing unit; and if the second voltage detection value is greater than or equal to the first confirmation voltage threshold, obtaining an insulation resistance value according to the first voltage detection value to determine an insulation state of the power battery.

[0012] In some embodiments, the determination that the first voltage detection value meets the abnormal threshold condition comprises: determining that the first voltage detection value is greater than a second voltage threshold.

[0013] In some embodiments, the second end of the fourth voltage dividing unit has a sampling reference ground with the negative terminal of the power battery, and the fault state of the insulation detection circuit is determined according to the second voltage detection value, including: if the second voltage detection value is less than a second confirmation voltage threshold, it is determined that there is an open circuit between the fourth voltage dividing unit and the sampling reference ground; and if the insulation detection value is greater than or equal to the second confirmation voltage threshold, an insulation resistance value is obtained according to the insulation detection value to determine the insulation state of the power battery.

[0014] In some embodiments, the first voltage detection value across the fourth voltage dividing unit is obtained, including: obtaining a first voltage value across the fourth voltage dividing unit when the switching switch is in a closed state, and obtaining a second voltage value across the fourth voltage dividing unit when the switching switch is in an open state.

[0015] In some embodiments, it is determined that the first voltage detection value satisfies an abnormal threshold condition, including: determining that the absolute value of the voltage difference between the first voltage value and the second voltage value is less than a third voltage threshold.

[0016] In some embodiments, the fault state of the insulation detection circuit is determined according to the second voltage detection value, including: obtaining an estimated voltage value across the fourth voltage dividing unit according to the resistance value of the first voltage dividing unit, the resistance value of the second voltage dividing unit, the resistance value of the third voltage dividing unit, the resistance value of the fourth voltage dividing unit, and the voltage value across the power battery; if the absolute value of the voltage difference between the second voltage detection value and the estimated voltage value is less than a third confirmation voltage threshold, it is determined that there is a signal acquisition card stagnation fault in the insulation detection circuit; and if the absolute value of the voltage difference between the second voltage detection value and the estimated voltage value is greater than or equal to the third confirmation voltage threshold, an insulation resistance value is obtained according to the first voltage detection value to determine the insulation state of the power battery.

[0017] To achieve the above object, the second aspect of the present application provides a power battery insulation detection device, comprising: an insulation detection circuit, the insulation detection circuit comprising a first voltage dividing unit, a second voltage dividing unit, a third voltage dividing unit and a fourth voltage dividing unit, a first end of the first voltage dividing unit being connected with a positive electrode end of the battery, a second end of the first voltage dividing unit being connected with a first end of the second voltage dividing unit, a second end of the second voltage dividing unit being connected with a first end of the third voltage dividing unit, a second end of the third voltage dividing unit being connected with a first end of the fourth voltage dividing unit, a second end of the fourth voltage dividing unit being connected with a negative electrode end of the battery, a first node being formed between the second end of the first voltage dividing unit and the first end of the second voltage dividing unit, the first node being connected with the negative electrode end of the battery through a switching switch, a second node being formed between the second end of the second voltage dividing unit and the first end of the third voltage dividing unit, the second node being connected with a vehicle body ground through a separation switch; a controller, the controller being connected with the insulation detection circuit, used for acquiring a voltage detection value between the fourth voltage dividing unit, and performing insulation detection on the battery according to the power battery insulation detection method.

[0018] According to the power battery insulation detection device provided by the embodiment of the present application, when the first voltage detection value detected by the insulation detection circuit is abnormal, the controller does not directly determine that the insulation between the power battery and the vehicle body ground is abnormal, but controls the separation switch to be turned off and acquires the second voltage detection value, and further identifies whether the insulation detection circuit is faulty and the type of fault based on the second voltage detection value, so that the fault of the insulation detection circuit and the real insulation alarm can be more accurately identified, the false alarm or the false alarm of the insulation alarm is avoided, and the reliability of the insulation detection is improved.

[0019] In some embodiments, the power battery insulation detection device further comprises: a filtering module, the filtering module being connected with the insulation detection circuit, used for filtering the voltage detection value between the fourth voltage dividing unit.

[0020] In some embodiments, the power battery insulation detection device further comprises: a clamping module, an input end of the clamping module being connected with the filtering module, an output end of the clamping module being connected with an AD sampling end of the controller, used for clamping the voltage detection value between the fourth voltage dividing unit within a preset range after filtering.

[0021] To achieve the above object, the third aspect of the present application provides a battery management system, comprising the power battery insulation detection device.

[0022] The battery management system according to the embodiment of the present application can more accurately identify the failure of the insulation detection circuit and the real insulation alarm by using the power battery insulation detection device in the above embodiment, and improve the reliability of insulation detection.

[0023] In order to achieve the above-mentioned purpose, the third aspect of the present application provides a vehicle comprising a power battery and the battery management system, wherein the battery management system is connected with the power battery.

[0024] The vehicle according to the embodiment of the present application can more accurately identify the failure of the insulation detection circuit and the real insulation alarm by using the battery management system in the above embodiment, and improve the reliability of insulation detection.

[0025] Additional aspects and advantages of the present application will be given in part in the following description, become apparent from the following description, or be understood through practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0027] Figure 1 is a block diagram of a power battery insulation detection device according to an embodiment of the present application;

[0028] Figure 2 is an equivalent circuit diagram of power battery insulation detection according to an embodiment of the present application;

[0029] Figure 3 is a block diagram of a power battery insulation detection device according to another embodiment of the present application;

[0030] Figure 4 is a flow chart of a power battery insulation detection method according to an embodiment of the present application;

[0031] Figure 5 is a schematic diagram of a failure fault of a detection channel of an insulation detection circuit shorting to GND;

[0032] Figure 6 is a flow chart of an insulation detection process for failure mode one according to an embodiment of the present application;

[0033] Figure 7 is a schematic diagram of a detection channel of an insulation detection circuit shorting to a power supply according to an embodiment of the present application;

[0034] Figure 8 is a flow chart of an insulation detection process for failure mode two according to an embodiment of the present application;

[0035] Figure 9 is a schematic diagram of signal acquisition for insulation detection circuit stuck according to an embodiment of the present application;

[0036] Figure 10 is a flow chart of an insulation detection process for failure mode two according to an embodiment of the present application;

[0037] Figure 11 is a block diagram of a battery management system according to an embodiment of the present application;

[0038] Figure 12 is a block diagram of a vehicle according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] Embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0040] For the failure of the detection channel of the power battery insulation detection device, the embodiments of the present application propose a power battery insulation detection method and a power battery insulation detection device, which can more accurately identify the effectiveness of the power battery insulation detection device, avoid false positives or false negatives of insulation alarms, and improve the accuracy and reliability of power battery insulation detection.

[0041] For the convenience of description, the power battery insulation detection device of the embodiments of the present application is described first.

[0042] Figure 1 is a block diagram of a power battery insulation detection device according to an embodiment of the present application, as shown in Figure 1 , the power battery insulation detection device 1 includes an insulation detection circuit 100 and a controller 200.

[0043] Figure 2 is an equivalent circuit diagram of power battery insulation detection according to an embodiment of the present application, as shown in Figure 2 , the insulation detection circuit 100 includes a first voltage dividing unit 10, a second voltage dividing unit 20, a third voltage dividing unit 30 and a fourth voltage dividing unit 40.

[0044] In some embodiments, the voltage dividing unit can include a resistor, which can include a single resistor or a series-parallel combination of multiple resistors, for example Figure 2 , taking the first voltage dividing unit 10, the second voltage dividing unit 20, the third voltage dividing unit 30 and the fourth voltage dividing unit 40 respectively including a resistor as an example.

[0045] In this configuration, the first end of the first voltage divider unit 10 is connected to the positive terminal of the power battery 50, the second end of the first voltage divider unit 10 is connected to the first end of the second voltage divider unit 20, the second end of the second voltage divider unit 20 is connected to the first end of the third voltage divider unit 30, the second end of the third voltage divider unit 30 is connected to the first end of the fourth voltage divider unit 40, and the second end of the fourth voltage divider unit 40 is connected to the negative terminal of the power battery 50. There is a first node O1 between the second end of the first voltage divider unit 10 and the first end of the second voltage divider unit 20. The first node O1 is connected to the negative terminal of the power battery 50 through a switching switch S1. There is a second node O2 between the second end of the second voltage divider unit 20 and the first end of the third voltage divider unit 30. The second node O2 is connected to the vehicle body, specifically the chassis, through a disconnect switch S2.

[0046] in, Figure 2 In this circuit, Rp represents the equivalent resistance between the positive terminal of the power battery 50 and the vehicle ground, and Rn represents the equivalent resistance between the negative terminal of the power battery 50 and the vehicle ground, which is the insulation resistance value being detected. The fourth voltage divider unit 40 can be used as a sampling resistor. The disconnect switch S2 is used to control the connection or disconnection of the power battery insulation detection circuit from the object being tested. The switching switch S1 can switch the bridge arm to switch between detecting the equivalent resistance between the positive terminal of the power battery and the vehicle ground or detecting the equivalent resistance between the negative terminal of the power battery and the vehicle ground. The fourth voltage divider unit 40 can be used as a sampling resistor. That is, the detection value of the power battery insulation detection circuit 100 can be the voltage value across the sampling resistor. Then, when the disconnect switch S2 is closed, the insulation detection between the positive and negative terminals of the power battery and the vehicle body ground can be realized by closing and opening the switch S1. For example, when the switch S1 is open, the equivalent resistance Rn between the negative terminal of the power battery and the vehicle body ground is detected. Conversely, when the switch S1 is closed, the equivalent resistance Rp between the positive terminal of the power battery and the vehicle body ground is detected. Thus, the insulation state between the power battery and the vehicle body ground can be determined.

[0047] The controller 200 is connected to the insulation detection circuit 100 to obtain the voltage detection value at both ends of the fourth voltage divider unit and to perform insulation detection on the battery according to the power battery insulation detection method. The power battery insulation detection method can be referred to in detail below.

[0048] like Figure 3 As shown, the power battery insulation detection device 1 also includes a filter module 300, which is connected to the insulation detection circuit 100 and is used to filter the voltage detection values ​​at both ends of the acquired fourth voltage divider unit to reduce signal interference and improve the accuracy of signal acquisition.

[0049] like Figure 3As shown, the power battery insulation detection device 1 further comprises a clamping module 400, an input end of the clamping module 400 is connected with the filtering module 300, and an output end of the clamping module 400 is connected with an AD sampling end of the controller 200, so as to clamp the voltage detection value between the two ends of the fourth voltage dividing unit in a preset range after filtering, avoid the collected signal exceeding the threshold of the AD sampling end, and achieve the protection effect.

[0050] For the insulation detection device using the unbalanced bridge method to detect the insulation resistance of the power battery, in some embodiments, there can be the following three failure modes:

[0051] Failure mode one: when the real insulation resistance of the power battery is greater than the insulation alarm threshold, if the detection channel of the power battery insulation detection device is short-circuited to GND, that is, the detection channel no longer passes through the sampling resistor and is directly connected to GND, the insulation resistance measured by the detection device will be very small, which will cause false alarm of the insulation alarm.

[0052] Failure mode two: when the real resistance of the power battery is greater than the insulation alarm threshold, if the detection channel of the insulation detection device is short-circuited to the power supply, that is, there is an open circuit before the GND of the detection channel, which cannot be connected to GND, and is equivalent to being short-circuited to the power supply such as +5V, at this time, the measured insulation resistance will be very large, which will cause missed alarm of the insulation alarm.

[0053] Failure mode three: if the detection channel of the insulation detection device has a failure of signal sticking, the measured insulation resistance will remain unchanged, at this time, if the real insulation resistance changes from normal to abnormal, the change will not be detected, which will cause missed alarm of the insulation alarm.

[0054] The following refers to Figures 4-10 a power battery insulation detection method according to an embodiment of the present application.

[0055] Figure 4 is a flowchart of a power battery insulation detection method according to an embodiment of the present application, as Figure 4 shown, the power battery insulation detection method of the embodiment of the present application comprises the following steps S1-S4.

[0056] S1, when the separation switch is in a closed state, a first voltage detection value between the two ends of the fourth voltage dividing unit is obtained.

[0057] Specifically, as Figure 2As shown, when the insulation detection circuit normally performs insulation detection on the power battery, the switch S3 is closed to form a loop between the power battery and the insulation detection circuit, and the separation switch S2 is in a closed state, and the fourth voltage dividing unit and the third voltage dividing unit have a voltage sampling point, so that the voltage detection value of the voltage sampling point, that is, the first voltage detection value between the fourth voltage dividing unit, is obtained, that is, the insulation detection sampling value of the insulation detection circuit, wherein the switching switch S1 can be disconnected or closed.

[0058] S2, determine whether the first voltage detection value meets the abnormal threshold condition.

[0059] Specifically, according to the first voltage detection value, the resistance values of the respective voltage dividing units of the insulation detection resistor, and the power battery voltage, the insulation resistance between the power battery and the vehicle body ground can be obtained by conversion. In order to ensure safety, the insulation resistance between the power battery and the vehicle body ground is limited to be greater than the insulation alarm threshold, and insulation alarm is performed when the insulation resistance is less than the insulation alarm threshold.

[0060] In the embodiment, under normal circumstances, the insulation resistance obtained based on the first voltage detection value detected by the insulation detection circuit is within the standard insulation resistance range, and if the first voltage detection value is abnormal, it is determined that the insulation resistance between the power battery and the vehicle body ground is abnormal. However, there is a possibility that the detection channel of the insulation detection circuit fails, which may cause the detected insulation resistance to be inconsistent with the actual insulation resistance, for example, the three failure modes mentioned above, which may cause false negatives or false positives of insulation alarm.

[0061] Different from the insulation resistance detection in the related art, the method of the embodiment of the present application further performs confirmation after determining that the first voltage detection value is abnormal, so as to accurately identify the failure fault of the detection channel of the power battery insulation detection circuit, for example, the three failure modes mentioned above, avoid false negatives or false positives of the power battery insulation resistance detection, and improve safety.

[0062] S3, control the separation switch and the switching switch to be disconnected, and obtain a second voltage detection value between the fourth voltage dividing unit.

[0063] Specifically, the separation switch and the switching switch are controlled to be disconnected, that is, the insulation detection circuit is disconnected from the detected object, for example Figure 2 the equivalent resistance Rp between the positive electrode of the power battery and the vehicle body ground and the equivalent resistance Rn between the negative electrode of the power battery and the vehicle body ground, so as to identify the fault state of the insulation detection circuit.

[0064] S4, determine the fault state of the insulation detection circuit according to the second voltage detection value.

[0065] Specifically, when an abnormal value of the first voltage detection value, i.e., the insulation resistance value, is monitored, the measured object is temporarily separated from the insulation detection circuit, and the second voltage detection value is further used for confirmation. At this time, the second voltage detection value can reflect the state of the detection channel of the insulation detection circuit, so that the fault of the failure of the insulation detection circuit detection channel and the real insulation alarm can be accurately identified, and the false alarm or the missed alarm of the insulation alarm can be avoided.

[0066] For example, for the three failure modes mentioned above, when the real insulation resistance value is greater than the insulation alarm threshold, the insulation resistance value obtained according to the first voltage detection value can be small, or the real insulation resistance value is less than the insulation alarm threshold, and the insulation resistance value obtained according to the first voltage detection value can be large, or the process that the real insulation resistance value changes from normal to abnormal cannot be detected, and at this time, the first voltage detection value can be unchanged. When such a situation occurs, i.e., the first voltage detection value is abnormal, the disconnecting switch and the switching switch are controlled to be turned off to separate the measured object and the insulation detection circuit, and then the second voltage detection value is used to identify the fault state of the insulation detection circuit, i.e., whether the insulation detection circuit is faulty and what kind of fault it is. For example, according to the second voltage detection value, it can be judged whether the detection channel of the insulation detection circuit is short-circuited, open-circuited, or the signal acquisition card is stuck.

[0067] According to the power battery insulation detection method of the embodiment of the present application, when the first voltage detection value normally detected by the insulation detection circuit is abnormal, the insulation abnormality between the power battery and the vehicle body ground is not directly determined, but the disconnecting switch is controlled to be turned off and the second voltage detection value is obtained, and then the insulation detection circuit is further identified based on the second voltage detection value to determine whether the insulation detection circuit is faulty and what kind of fault it is. Therefore, the failure fault of the insulation detection circuit and the real insulation alarm can be more accurately identified, the missed alarm or the false alarm of the insulation alarm can be avoided, and the reliability of the insulation detection can be improved.

[0068] The power battery insulation detection method of the embodiment of the present application will be described below by taking the three failure modes of the insulation detection circuit mentioned above as an example.

[0069] For the first failure mode, the real insulation resistance value is greater than the insulation alarm threshold, and the insulation detection circuit will not normally perform insulation alarm. If the detected insulation resistance value is very small, i.e., the first voltage detection value is abnormal, the insulation alarm will be falsely reported at this time.

[0070] For example, Figure 5 A schematic diagram of the failure fault of the short-circuit of the detection channel of the insulation detection circuit to GND, wherein the detection channel of the insulation detection circuit can be, for example, Figure 2 the detection path in which the insulation detection circuit is connected with the power battery and the vehicle body ground. For example, Figure 5As shown, in normal condition, the detection channel of the insulation detection circuit flows from the power supply end, for example, +5V, to the GND, i.e., the sampling reference ground, through the voltage dividing unit including the fourth voltage dividing unit. When the detection channel of the insulation detection circuit is short-circuited to the GND, i.e., the fourth voltage dividing unit is short-circuited, the detection channel no longer flows through the fourth voltage dividing unit, and the first voltage detection value is very small at this time.

[0071] In an embodiment, it is determined that the first voltage detection value is less than the first voltage threshold value, i.e., the insulation resistance is very small. In a conventional scheme, an insulation alarm is performed at this time, but in the present application, further identification and confirmation are performed according to the second voltage detection value.

[0072] Further, the control disconnecting switch and the switching switch are both disconnected, the second voltage detection value at the two ends of the fourth voltage dividing unit is obtained, and if the second voltage detection value is less than the first confirmation voltage threshold value, it is determined that the fourth voltage dividing unit is short-circuited, i.e., the detection channel of the insulation detection circuit is short-circuited to the sampling reference ground, and an insulation alarm is performed, so that the real insulation alarm can be accurately determined, and the fault occurrence point can be accurately located. In an embodiment, the first confirmation voltage threshold value can be detected and set when the detection channel of the insulation detection circuit is short-circuited.

[0073] On the contrary, if the second voltage detection value is greater than or equal to the first confirmation voltage threshold value, it is determined that the detection channel of the insulation detection circuit does not have a short-circuit fault, and the insulation resistance is obtained according to the first voltage detection value to determine the insulation state of the battery.

[0074] Specifically, for the above failure mode one: when the first voltage detection value detected by the insulation detection circuit satisfies condition 1: Vres Figure 2 , the insulation detection circuit is separated from the equivalent resistance in the measured object, for example Figure 2 , through the voltage dividing circuit of the resistors R1, R2, R3 and R4 in the known voltage dividing unit, the second voltage detection value Vcheck1 at the two ends of the resistor R4 is collected, and again confirmation is performed. If condition 2: Vcheck1

[0075] Based on the above description, Figure 6 is a flowchart of the insulation detection process for the failure mode one according to an embodiment of the present application, and as shown in Figure 2 and Figure 6 , specifically includes the following steps:

[0076] S11, the battery management system is woken up.

[0077] S12, the insulation detection circuit is started. At this time, the disconnect switch is closed.

[0078] S13, a first voltage detection value after filtering is obtained. In the embodiment, the first voltage detection value can include a voltage detection value between the fourth voltage dividing unit when the switch is closed, for example, U1 and U2, U1 is the first voltage detection value when the switch is opened, and U2 is the first voltage detection value when the switch is closed.

[0079] S14, it is judged whether the first voltage detection value satisfies U1 < Vthr1 or U2 < Vthr1. If it is satisfied, step S15 is entered, otherwise, step S16 is entered.

[0080] S15, the abnormal threshold condition corresponding flag is set to 1.

[0081] S16, the abnormal threshold condition corresponding flag is set to 0.

[0082] S17, it is judged whether the abnormal threshold condition corresponding flag is 1. If yes, step S18 is entered, otherwise, step S12 is returned.

[0083] S18, the disconnect switch and the switch are controlled to be opened.

[0084] S19, a second voltage detection value after filtering is obtained.

[0085] S20, it is judged whether the second voltage detection value satisfies Vcheck1 < Vchkthr1. If it is satisfied, step S21 is entered, otherwise, step S22 is entered.

[0086] S21, the detection channel failure corresponding flag is set to 1.

[0087] S22, the detection channel failure corresponding flag is set to 0.

[0088] S23, it is judged whether the detection channel failure corresponding flag is 1. If yes, step S24 is entered, otherwise, step S19 is returned.

[0089] S24, it is determined that the detection channel of the insulation detection circuit is short-circuited to the sampling reference ground.

[0090] Therefore, the power battery insulation detection method of the embodiment can accurately diagnose the failure that the detection channel of the insulation detection circuit is short-circuited to the GND, and the insulation alarm is not misreported, and the reliability of the insulation detection is improved.

[0091] For the second failure mode, i.e. the detection channel of the insulation detection circuit is shorted to the power supply, Figure 7 is a schematic diagram of the detection channel of the insulation detection circuit being shorted to the power supply according to an embodiment of the present application. In the embodiment, the second end of the fourth voltage dividing unit has a sampling reference ground with the negative terminal of the power battery, as shown in Figure 7 The failure point is between the fourth voltage dividing unit and the sampling reference ground, i.e. there is an open circuit between the fourth voltage dividing unit and the sampling reference ground, and the detection channel of the insulation detection circuit is shorted to the power supply, for example, +5V. At this time, the first voltage detection value is relatively large, for example, the first voltage detection value is greater than the second voltage threshold value. Under normal circumstances, the insulation resistance value detected by the insulation detection circuit based on the first voltage detection value will be very large, while the true insulation resistance value is less than the insulation alarm threshold value, thereby causing a false negative insulation alarm.

[0092] The power battery insulation detection method of the present application further controls the disconnecting switch and the switching switch to be both disconnected, separates the detected object and the insulation detection circuit, and determines the failure state of the detection channel of the insulation detection circuit according to the second voltage detection value. For example, if the second voltage detection value is less than the second confirmation voltage threshold value, it is determined that there is an open circuit between the fourth voltage dividing unit and the sampling reference ground. At this time, an insulation alarm is performed, thereby avoiding a false negative insulation alarm. In the embodiment, the second confirmation voltage threshold value can be detected and set when the open circuit occurs in the detection channel of the insulation detection circuit.

[0093] If the insulation detection value is greater than or equal to the second confirmation voltage threshold value, the insulation resistance value is obtained according to the insulation detection value to determine the insulation state of the battery.

[0094] Specifically, for the second failure mode: when the first voltage detection value measured by the insulation detection circuit satisfies condition 1: Vres>Vthr2, where Vthr2 is the second voltage threshold value, the insulation detection circuit is separated from the measured object by controlling the disconnecting switch S2 and the switching switch S1 to be disconnected. The second voltage detection value Vcheck2 is collected by the voltage dividing circuit with known resistors R1, R2, R3 and R4. Again, if condition 2: Vcheck2Vchkthr2 is satisfied, where Vchkthr2 is the second confirmation voltage threshold value, it is diagnosed that the insulation detection circuit fails. Otherwise, Vres should be taken as the effective value for insulation resistance conversion and the corresponding insulation state should be reported.

[0095] Based on the above description, Figure 8 is a flowchart of the insulation detection process for the second failure mode according to an embodiment of the present application. Referring to Figure 2 and Figure 8 , the process specifically includes the following steps:

[0096] S25, the battery management system is woken up.

[0097] S26, the insulation detection circuit is started. At this time, the separation switch is closed.

[0098] S27, the first voltage detection value after filtering is obtained. In the embodiment, the first voltage detection value can include the voltage detection value between the fourth voltage dividing unit when the switching switch is closed, for example, U1 and U2, U1 is the first voltage detection value when the switching switch is opened, and U2 is the first voltage detection value when the switching switch is closed.

[0099] S28, it is judged whether the first voltage detection value satisfies U1>Vthr2 or U2>Vthr2. If it is satisfied, step S29 is entered, otherwise, step S30 is entered.

[0100] S29, the abnormal threshold condition corresponding flag is set to 1.

[0101] S30, the abnormal threshold condition corresponding flag is set to 0.

[0102] S31, it is judged whether the abnormal threshold condition corresponding flag is 1. If yes, step S32 is entered, otherwise, step S27 is returned.

[0103] S32, the separation switch and the switching switch are controlled to be opened.

[0104] S33, the second voltage detection value after filtering is obtained.

[0105] S34, it is judged whether the second voltage detection value satisfies Vcheck2>Vchkthr2. If it is satisfied, step S35 is entered, otherwise, step S36 is entered.

[0106] S35, the detection channel failure corresponding flag is set to 1.

[0107] S36, the detection channel failure corresponding flag is set to 0.

[0108] S37, it is judged whether the detection channel failure corresponding flag is 1. If yes, step S38 is entered, otherwise, step S33 is returned.

[0109] S38, it is determined that the detection channel of the insulation detection circuit is short-circuited to the power supply.

[0110] Therefore, the power battery insulation detection method of the embodiment can accurately diagnose the failure that the detection channel of the insulation detection circuit is short-circuited to the power supply, and the insulation alarm is not missed, and the reliability of the insulation detection is improved.

[0111] For the third failure mode, the signal acquisition card of the detection channel of the insulation detection circuit is stuck, for example, Figure 9As shown, the signal collected by the controller AD sampling end is always unchanged, at this time, if the real insulation resistance value changes from normal to abnormal, it cannot be detected, thereby missing the insulation alarm.

[0112] In the embodiment of the present application, for the third failure mode, obtaining the first voltage detection value across the fourth voltage dividing unit includes: obtaining the first voltage value across the fourth voltage dividing unit when the switching switch is in the closed state, and obtaining the second voltage value across the fourth voltage dividing unit when the switching switch is in the open state.

[0113] Further, when the absolute value of the voltage difference between the first voltage value and the second voltage value is less than the third voltage threshold value, the third voltage threshold value can be a relatively small voltage value, at this time, it is determined that the first voltage detection value changes little or almost not, and it is determined that the first voltage detection value meets the abnormal threshold condition, at this time, if the real insulation resistance value is abnormal, it cannot be detected by the insulation detection circuit, and the missing insulation warning is easy to occur.

[0114] In the embodiment of the present application, when it is determined that the first voltage detection value does not change, the switching switch S1 and the disconnecting switch S2 are controlled to be opened, the insulation detection circuit is separated from the measured object, and the second voltage detection value across the fourth voltage dividing unit is further obtained. And, the estimated voltage value across the fourth voltage dividing unit is obtained by conversion according to the resistance value of the first voltage dividing unit, the resistance value of the second voltage dividing unit, the resistance value of the third voltage dividing unit, the resistance value of the fourth voltage dividing unit and the voltage value across the power battery; if the absolute value of the voltage difference between the second voltage detection value and the estimated voltage value is less than the third confirmation voltage threshold value, it is determined that the detection channel of the insulation detection circuit has a signal acquisition card sticking fault, and the insulation warning is performed, thereby avoiding missing the insulation alarm. The third confirmation voltage threshold value can be set based on the detection of the signal sticking of the detection channel of the insulation detection circuit.

[0115] On the contrary, if the absolute value of the voltage difference between the second voltage detection value and the estimated voltage value is greater than or equal to the third confirmation voltage threshold value, at this time, it is considered that there is no fault, and the insulation resistance value is obtained according to the first voltage detection value to determine the insulation state of the power battery.

[0116] Specifically, for the failure of the detection channel signal card of the insulation detection circuit: when the two voltage values, i.e. the first voltage value Vres-1 and the second voltage value Vres-2, detected by the insulation detection circuit before and after the switching of the bridge arm satisfy condition 1: |Vres1-Vres2|<Vthr3, where Vthr3 is a third voltage threshold, the insulation detection circuit is separated from the measured object by controlling the switching switch and the separation switch to be both open, and the second voltage detection value Vcheck3 is collected by the voltage division circuit of the known resistors R1, R2, R3 and R4, and then condition 2: |Vcheck3-Vref|<Vchkthr3 is satisfied again, where Vref is an estimated voltage value between the fourth voltage division unit, it is diagnosed that the insulation detection circuit fails, otherwise, Vres1 and Vres2 are taken as valid values for insulation resistance conversion and the corresponding insulation state is reported.

[0117] Based on the above description, Figure 10 is a flowchart of the insulation detection process for failure mode two according to an embodiment of the present application, referring to Figure 2 and Figure 10 , specifically comprising the following steps:

[0118] S39, the battery management system is woken up.

[0119] S40, the insulation detection circuit is started. At this time, the separation switch is closed.

[0120] S41, the first voltage value U1 and the second voltage value U2 after filtering are obtained, U1 is the first voltage detection value detected when the switching switch is open, and U2 is the first voltage detection value detected when the switching switch is closed.

[0121] S42, it is judged whether the first voltage value and the second voltage value satisfy |U1-U2|<Vthr3. If yes, step S43 is entered, otherwise, step S44 is entered.

[0122] S43, the abnormal threshold condition corresponding flag is set to 1.

[0123] S44, the abnormal threshold condition corresponding flag is set to 0.

[0124] S45, it is judged whether the abnormal threshold condition corresponding flag is 1. If yes, step S46 is entered, otherwise, step S40 is returned.

[0125] S46, the separation switch and the switching switch are controlled to be open.

[0126] S47, the second voltage detection value after filtering is obtained.

[0127] S48, judge whether the second voltage detection value satisfies |Vcheck3-U|>Vchkthr3, if yes, go to step S49, if not, go to step S50.

[0128] S49, set the detection channel failure corresponding flag bit to 1.

[0129] S50, set the detection channel failure corresponding flag bit to 0.

[0130] S51, judge whether the detection channel failure corresponding flag bit is 1, if yes, go to step S52, if not, return to step S47.

[0131] S52, determine that the insulation detection circuit exists signal sticking fault.

[0132] Therefore, the power battery insulation detection method can accurately diagnose the failure fault of the detection channel signal sticking of the insulation detection circuit, does not miss the insulation alarm, and improves the reliability of the insulation detection.

[0133] In summary, the power battery insulation detection method and device can accurately identify the failure fault of the insulation detection circuit and the real insulation alarm when the insulation detection circuit is working normally, can accurately locate the fault occurrence point, and improves the reliability of the insulation detection.

[0134] Based on the power battery insulation detection device of the above embodiment, the third aspect embodiment of the present application further proposes a battery management system.

[0135] Figure 11 For the block diagram of the battery management system according to an embodiment of the present application, as shown in Figure 11 , the battery management system 1000 includes the power battery insulation detection device 1 of the above embodiment.

[0136] Among them, the power battery insulation detection device 1 includes an insulation detection circuit and a controller, wherein in some embodiments, the composition of the insulation detection circuit can be as shown in Figure 2 , which will not be repeated here.

[0137] According to the battery management system 1000 of the embodiment of the present application, by adopting the power battery insulation detection device 1 of the above embodiment, the failure fault of the insulation detection circuit and the real insulation alarm can be more accurately identified, and the reliability of the insulation detection is improved.

[0138] The fourth aspect embodiment of the present application further proposes a vehicle, as Figure 12As shown, the vehicle 2 comprises a power battery 50 and a battery management system 1000 connected with the power battery 50, and the battery management system 1000 can detect the insulation of the power battery 50 through the insulation detection device 1 described above.

[0139] According to the vehicle 2 of the embodiment of the present application, by adopting the battery management system 1000 of the above embodiment, the insulation detection circuit failure fault and the real insulation alarm can be more accurately identified, and the reliability of the insulation detection is improved.

[0140] It should be noted that in the description of the present application, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily mean the same embodiment or example.

[0141] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for detecting the insulation of a power battery, characterized in that, An insulation detection circuit is used, comprising a first voltage divider unit, a second voltage divider unit, a third voltage divider unit, and a fourth voltage divider unit. A first terminal of the first voltage divider unit is connected to the positive terminal of the power battery. A second terminal of the first voltage divider unit is connected to the first terminal of the second voltage divider unit. A second terminal of the second voltage divider unit is connected to the first terminal of the third voltage divider unit. A second terminal of the third voltage divider unit is connected to the first terminal of the fourth voltage divider unit. A second terminal of the fourth voltage divider unit is connected to the negative terminal of the power battery. The second terminal of the fourth voltage divider unit and the negative terminal of the power battery have a sampling reference ground. A first node is located between the second terminal of the first voltage divider unit and the first terminal of the second voltage divider unit. This first node is connected to the negative terminal of the power battery via a switching switch. A second node is located between the second terminal of the second voltage divider unit and the first terminal of the third voltage divider unit. This second node is connected to the vehicle body ground via a disconnect switch. The power battery insulation detection method includes: When the disconnect switch is in the closed state, the first voltage detection value across the fourth voltage divider unit is obtained; It is determined that the first voltage detection value meets the abnormal threshold condition; Both the disconnect switch and the switching switch are disconnected to obtain the second voltage detection value across the fourth voltage divider unit. Determining the fault state of the insulation detection circuit based on the second voltage detection value includes: if the second voltage detection value is less than the first confirmation voltage threshold, then determining that a short circuit has occurred at both ends of the fourth voltage divider unit; or, if the second voltage detection value is less than the second confirmation voltage threshold, then determining that there is an open circuit between the fourth voltage divider unit and the sampling reference ground; or, obtaining an estimated voltage value at both ends of the fourth voltage divider unit based on the resistance values ​​of the first voltage divider unit, the second voltage divider unit, the third voltage divider unit, the fourth voltage divider unit, and the voltage value at both ends of the power battery; if the absolute value of the voltage difference between the second voltage detection value and the estimated voltage value is less than the third confirmation voltage threshold, then determining that the insulation detection circuit has a signal acquisition lag fault.

2. The method for detecting the insulation of a power battery according to claim 1, characterized in that, Determining that the first voltage detection value meets the abnormal threshold condition includes: determining that the first voltage detection value is less than the first voltage threshold.

3. The method for detecting the insulation of a power battery according to claim 2, characterized in that, Determining the fault state of the insulation detection circuit based on the second voltage detection value further includes: If the second voltage detection value is greater than or equal to the first confirmed voltage threshold, the insulation resistance value is obtained based on the first voltage detection value to determine the insulation state of the power battery.

4. The method for detecting the insulation of a power battery according to claim 1, characterized in that, Determining that the first voltage detection value meets the abnormal threshold condition includes: determining that the first voltage detection value is greater than the second voltage threshold.

5. The method for detecting the insulation of a power battery according to claim 4, characterized in that, Determining the fault state of the insulation detection circuit based on the second voltage detection value further includes: If the insulation detection calculated value is greater than or equal to the second confirmation voltage threshold, then the insulation resistance value is obtained based on the insulation detection value to determine the insulation state of the power battery.

6. The method for detecting the insulation of a power battery according to claim 1, characterized in that, Obtaining the first voltage detection value across the fourth voltage divider unit includes: The system acquires the first voltage value across the fourth voltage divider unit when the switch is in the closed state, and the second voltage value across the fourth voltage divider unit when the switch is in the open state.

7. The method for detecting the insulation of a power battery according to claim 6, characterized in that, Determining that the first voltage detection value meets the abnormal threshold condition includes: determining that the absolute value of the voltage difference between the first voltage value and the second voltage value is less than a third voltage threshold.

8. The method for detecting the insulation of a power battery according to claim 7, characterized in that, Determining the fault state of the insulation detection circuit based on the second voltage detection value further includes: If the absolute value of the voltage difference between the second voltage detection value and the estimated voltage value is greater than or equal to the third confirmed voltage threshold, then the insulation resistance value is obtained based on the first voltage detection value to determine the insulation state of the power battery.

9. A power battery insulation testing device, characterized in that, include: An insulation detection circuit is provided, comprising a first voltage divider unit, a second voltage divider unit, a third voltage divider unit, and a fourth voltage divider unit. A first terminal of the first voltage divider unit is connected to the positive terminal of the battery. A second terminal of the first voltage divider unit is connected to the first terminal of the second voltage divider unit. A second terminal of the second voltage divider unit is connected to the first terminal of the third voltage divider unit. A second terminal of the third voltage divider unit is connected to the first terminal of the fourth voltage divider unit. A second terminal of the fourth voltage divider unit is connected to the negative terminal of the battery. A first node is located between the second terminal of the first voltage divider unit and the first terminal of the second voltage divider unit. This first node is connected to the vehicle body ground via a disconnect switch. A controller, connected to the insulation detection circuit, is used to acquire the voltage detection value at both ends of the fourth voltage divider unit and to perform insulation detection on the battery according to any one of claims 1-8.

10. The power battery insulation testing device according to claim 9, characterized in that, The power battery insulation detection device also includes: A filtering module, which is connected to the insulation detection circuit, is used to filter the voltage detection values ​​collected at both ends of the fourth voltage divider unit.

11. The power battery insulation testing device according to claim 10, characterized in that, The power battery insulation detection device also includes: A clamping module, the input of which is connected to the filtering module, and the output of which is connected to the AD sampling terminal of the controller, is used to clamp the voltage detection values ​​at both ends of the filtered fourth voltage divider unit within a preset range.

12. A battery management system, characterized in that, Includes the power battery insulation testing device as described in any one of claims 9-11.

13. A vehicle, characterized in that, It includes a power battery and the battery management system as described in claim 12, wherein the battery management system is connected to the power battery.

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