CN111060791A - Insulation fault detection method and device, electric vehicle, terminal equipment and medium - Google Patents
Insulation fault detection method and device, electric vehicle, terminal equipment and medium Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/14—Circuits therefor, e.g. for generating test voltages, sensing circuits
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
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Abstract
The invention discloses an insulation fault detection method, an insulation fault detection device, an electric automobile, terminal equipment and a medium, wherein the method comprises the following steps: closing a switch in an additional branch of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel; calculating an insulation resistance value of the battery pack; and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and performing insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack. By adopting the embodiment of the invention, the insulation fault condition of the battery pack can be accurately detected.
Description
Technical Field
The invention relates to the technical field of automobiles, in particular to an insulation fault detection method and device, an electric automobile, terminal equipment and a medium.
Background
With the rapid development of electric automobile technology, electric automobiles with the advantages of economy, environmental protection and the like become vehicles selected by more and more people. Because the electric automobile comprises the high-voltage electrical system, if the battery pack of the electric automobile has insulation faults, the safety of the electric automobile and users can be greatly threatened, and therefore the realization of the insulation fault detection of the battery pack of the electric automobile has very important practical significance.
At present, in the field of automotive technology, generally, an insulation detection circuit is used to perform insulation fault detection on a battery pack, so as to obtain a fault detection result of the battery pack, for example, an insulation resistance value of the battery pack is obtained through measurement by the insulation detection circuit, then the measured insulation resistance value is compared with an insulation resistance alarm threshold, and whether an insulation fault occurs in the battery pack is determined by judging whether the measured insulation resistance value is lower than the insulation resistance alarm threshold, specifically, a schematic diagram of an insulation detection circuit in the prior art is shown in fig. 1.
The inventor finds that the insulation fault detection circuit is prone to failure and failure along with the change of the service time of a vehicle, when the insulation detection circuit fails, an inaccurate fault detection result of a battery pack can be obtained easily, and the existing insulation fault detection method does not detect the effectiveness of the insulation detection circuit in the process of detecting the insulation fault of the battery pack, so that the insulation fault detection accuracy of the existing insulation fault detection method is low.
Disclosure of Invention
The embodiment of the invention provides an insulation fault detection method and device, an electric automobile, terminal equipment and a medium, which can accurately detect the insulation fault condition of a battery pack.
In order to achieve the above object, an embodiment of the present invention provides an insulation fault detection method, including:
closing a switch in an additional branch of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel;
calculating an insulation resistance value of the battery pack; the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack;
and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and performing insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack.
As an improvement of the above scheme, the insulation detection circuit further includes a first battery interface for connecting with the positive electrode of the battery pack, a second battery interface for connecting with the negative electrode of the battery pack, a ground interface for connecting with the shell of the electric vehicle, and a first measuring resistor, a second measuring resistor, a first sampling resistor, a second sampling resistor, a third sampling resistor, and a fourth sampling resistor; the resistance value of the first measuring resistor is equal to that of the second measuring resistor;
the first end of the first switch is connected with the first battery interface, the second end of the first switch is connected with the first end of the first measuring resistor, and the second end of the first measuring resistor is connected with the grounding interface;
the first end of the first sampling resistor is connected with the first battery interface, the second end of the first sampling resistor is connected with the first end of the second sampling resistor, and the second end of the second sampling resistor is connected with the grounding interface;
the first end of the second switch is connected with the second battery interface, the second end of the second switch is connected with the first end of the second measuring resistor, and the second end of the second measuring resistor is connected with the grounding interface;
the first end of the third sampling resistor is connected with the second battery interface, the second end of the third sampling resistor is connected with the first end of the fourth sampling resistor, and the second end of the fourth sampling resistor is connected with the grounding interface;
the switch in the additional branch is a third switch, and the resistor in the additional branch is a third measuring resistor;
the first end of the third switch is connected with the first battery interface, the second end of the third switch is connected with the first end of the third measuring resistor, and the second end of the third measuring resistor is connected with the grounding interface.
As an improvement of the above aspect, the insulation fault detection method further includes the steps of:
and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is not smaller than a preset threshold value, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault or an insulation detection circuit of the battery pack is invalid.
As an improvement of the above aspect, the insulation fault detection method further includes the steps of:
and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the negative electrode side of the battery pack, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault.
As an improvement of the above scheme, the calculating the insulation resistance value of the battery pack specifically includes:
acquiring a first positive side voltage to ground and a first negative side voltage to ground of the battery pack;
judging whether the positive electrode side of the battery pack is the side with larger voltage to earth according to the first positive electrode side voltage to earth and the first negative electrode side voltage to earth, and controlling the first switch to be closed when the judgment result is yes, and controlling the second switch to be closed when the judgment result is no;
acquiring a second positive-side voltage-to-ground voltage, a second negative-side voltage-to-ground voltage, and a first time when it is detected that the positive-side voltage-to-ground voltage and the negative-side voltage-to-ground voltage of the battery pack reach steady states; wherein the first time is a time required for the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack to reach a steady state from the first switch or the second switch being closed;
when the judgment result is yes, calculating a cathode-side equivalent insulation resistance value of the battery pack according to the first anode-side voltage-to-ground voltage, the first cathode-side voltage-to-ground voltage, the second anode-side voltage-to-ground voltage, the second cathode-side voltage-to-ground voltage and the resistance value of the first measuring resistor, and taking the cathode-side equivalent insulation resistance value of the battery pack as the insulation resistance value of the battery pack;
and when the judgment result is negative, calculating the anode-side equivalent insulation resistance value of the battery pack according to the first anode-side voltage to earth, the first cathode-side voltage to earth, the second anode-side voltage to earth, the second cathode-side voltage to earth, the resistance value of the second measuring resistor and the resistance value of the third measuring resistor, and taking the anode-side equivalent insulation resistance value of the battery pack as the insulation resistance value of the battery pack.
As an improvement of the above scheme, the detecting of the insulation fault of the battery pack by the insulation detection circuit to obtain the fault detection result of the battery pack specifically includes:
judging whether the first time is less than or equal to an early warning time threshold value, if so, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault; if not, judging that the fault detection result of the battery pack is that the battery pack has no insulation fault; the early warning time threshold is configured according to the capacity value of the Y capacitor of the battery pack, the fault threshold of the insulation resistance of the battery pack to the ground and the time constant coefficient of the insulation detection circuit.
As an improvement of the above scheme, the early warning time threshold is calculated by the following formula:
△t′p＝fp×Cp×RG
of formula (II b), △ t'pThe early warning time threshold value is obtained; f. ofpIs a time constant coefficient of the insulation detection circuit; cpThe capacitance value of the Y capacitor of the battery pack is shown; rGWhen the insulation resistance value of the positive electrode side of the battery pack to the ground is equal to the fault threshold value of the insulation resistance of the battery pack to the ground, the equivalent resistance value of the positive electrode side of the battery pack to the ground is obtained;
wherein R isGThe calculation formula is specifically as follows:
in the formula, RalarmAnd the failure threshold value of the insulation resistance of the battery pack to the ground is set.
As an improvement of the above, a product between a time constant coefficient of the insulation detection circuit and a capacity value of the Y capacitor of the battery pack is obtained in advance by:
when the battery pack is in a normal insulation state, closing the third switch;
after closing the third switch, closing the first switch;
acquiring a second time △ t when it is detected that the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack reach steady statespWherein the second time is △ tpA time required for the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack to reach a steady state from the closing of the first switch;
by the formula
Calculating a product f between a time constant coefficient of the insulation detection circuit and a capacitance value of the Y capacitor of the battery packp×Cp(ii) a Wherein R isP0Is the resistance value of the third measuring resistor, R1Is the resistance value, R, of the first sampling resistor2The resistance value of the second sampling resistor is obtained;
controlling the first switch and the third switch to be turned off.
As an improvement of the above, whether the voltages to earth on the positive side and the negative side of the battery pack reach steady states is detected by:
periodically sampling the voltage to earth on the positive side and the voltage to earth on the negative side of the battery pack;
when the change value of the voltage to earth of the positive side and the change value of the voltage to earth of the negative side in two adjacent sampling are detected to be smaller than a preset voltage threshold value, the voltage to earth of the positive side and the voltage to earth of the negative side of the battery pack are judged to reach steady states.
Correspondingly, the embodiment of the invention also provides an insulation fault detection device, which comprises:
the switch control module is used for closing a switch in an additional branch of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel;
the insulation resistance value calculation module is used for calculating the insulation resistance value of the battery pack; the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack;
and the insulation fault determination module is used for determining that the insulation detection circuit is effective when the insulation resistance value of the battery pack is determined to be the equivalent insulation resistance value of the positive electrode side of the battery pack and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, and performing insulation fault detection on the battery pack through the insulation detection circuit so as to obtain a fault detection result of the battery pack.
The embodiment of the invention also provides an electric automobile which comprises an automobile shell, a battery pack, an insulation detection circuit and the insulation fault detection device.
An embodiment of the present invention further provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, the insulation fault detection method according to any one of the above is implemented.
The embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the insulation fault detection method according to any one of the above items.
Compared with the prior art, the insulation fault detection method, the insulation fault detection device, the electric automobile, the terminal equipment and the medium provided by the embodiment of the invention have the advantages that the switch in the additional branch of the insulation detection circuit is closed; calculating an insulation resistance value of the battery pack; and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and performing insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack. When the insulation detection is carried out, whether the insulation resistance value of the battery pack is the equivalent insulation resistance value of the positive electrode side of the battery pack is judged, whether the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value is judged, whether the insulation detection circuit is effective is judged, and after the insulation detection circuit is judged to be effective, the insulation fault detection is carried out on the battery pack through the insulation detection circuit, so that the fault detection result of the battery pack is obtained, the problem that the fault detection result of the inaccurate battery pack is easily obtained due to the fact that the effectiveness of the insulation detection circuit is not detected in the insulation fault detection process of the battery pack in the prior art is solved, and the insulation fault condition of the battery pack can be accurately detected.
Drawings
Fig. 1 is a schematic diagram of an insulation detection circuit of the prior art.
Fig. 2 is a schematic flow chart of an embodiment of an insulation fault detection method provided by the present invention.
Fig. 3 is a schematic structural diagram of an embodiment of an insulation detection circuit in the insulation fault detection method provided by the present invention.
Fig. 4 is a schematic view of an application scenario of an insulation detection circuit in the insulation fault detection method provided by the present invention.
Fig. 5 is a schematic structural diagram of an embodiment of the insulation fault detection apparatus provided in the present invention.
Fig. 6 is a schematic structural diagram of an embodiment of a terminal device provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any inventive step, are within the scope of the present invention.
Fig. 2 is a schematic flow chart of an embodiment of the insulation fault detection method provided in the present invention.
The embodiment of the invention provides an insulation fault detection method which can be used for operating when a vehicle controller is powered on and judging the insulation fault condition of a battery pack of a vehicle in time, so that the safety of the vehicle and personnel in the vehicle can be effectively protected in time.
The insulation fault detection method provided by the embodiment of the invention comprises the following steps S1 to S3:
s1, closing a switch in an additional branch of the insulation detection circuit; the additional branch is formed by connecting a switch and a resistor in series, and the additional branch is connected between the positive electrode side of the battery pack and the ground in parallel.
S2, calculating the insulation resistance value of the battery pack; wherein the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack.
And S3, when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and carrying out insulation fault detection on the battery pack through the insulation detection circuit so as to obtain a fault detection result of the battery pack.
In a specific implementation, the resistance value of the resistor in the additional branch may be set according to an actual insulation fault threshold, which is not limited herein, and optionally, the resistance value of the resistor in the additional branch is equal to the maximum operating voltage of the battery pack multiplied by 500 Ω/V.
In specific implementation, the preset threshold may be set according to actual calculation accuracy of the insulation resistance, which is not limited herein, and optionally, the preset threshold is 15%.
Wherein the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is: [ (resistance of resistor in additional branch-insulation resistance of battery pack)/resistance of resistor in additional branch ] × 100%.
It should be noted that, the insulation detection circuit in this embodiment is based on the insulation detection circuit of the balanced bridge method provided in the prior art, and an additional branch is added, the additional branch is formed by connecting a switch and a resistor in series, and the additional branch is connected in parallel between the positive electrode side of the battery pack and the ground. It can be understood that in the state that the insulation of the battery pack is normal and the insulation detection circuit is effective, the resistance value of the positive and negative sides of the battery pack to the ground insulation resistor tends to be infinite, and when the positive side of the insulation detection circuit introduces the resistor in the additional branch, since the positive side equivalent insulation resistance value of the battery pack is equal to the parallel value of the positive side insulation resistance to ground of the battery pack and the resistance in the additional branch, the resistance value of the insulation resistor of the negative electrode side of the battery pack to the ground tends to be infinite, so the equivalent insulation resistance value of the positive electrode side of the battery pack is smaller than the equivalent insulation resistance value of the negative electrode side of the battery pack, namely the insulation resistance value of the battery pack is equal to the equivalent insulation resistance value of the positive electrode side of the battery pack, and the calculated relative deviation between the anode side equivalent insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch circuit is smaller than a preset threshold value, namely the calculation precision of the anode side equivalent insulation resistance value is within the preset threshold value. Based on the above analysis, it can be understood that when it is determined that the insulation resistance value of the battery pack is the equivalent insulation resistance value of the positive electrode side of the battery pack and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than the preset threshold, it can be determined that the insulation detection circuit is effective, and it can be preliminarily determined that the insulation of the battery pack is normal, after it is determined that the insulation detection circuit is effective, the insulation fault of the battery pack is further detected through the insulation detection circuit, so as to obtain a fault detection result of the battery pack, and it can be further determined whether the insulation fault of the battery pack occurs, so that the insulation fault condition of the battery pack is accurately detected.
According to the insulation fault detection method provided by the embodiment of the invention, the switch in the additional branch of the insulation detection circuit is closed; calculating an insulation resistance value of the battery pack; and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and performing insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack. When the insulation detection is carried out, whether the insulation resistance value of the battery pack is the equivalent insulation resistance value of the positive electrode side of the battery pack is judged, whether the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value is judged, whether the insulation detection circuit is effective is judged, and after the insulation detection circuit is judged to be effective, the insulation fault detection is carried out on the battery pack through the insulation detection circuit, so that the fault detection result of the battery pack is obtained, the problem that the fault detection result of the inaccurate battery pack is easily obtained due to the fact that the effectiveness of the insulation detection circuit is not detected in the insulation fault detection process of the battery pack in the prior art is solved, and the insulation fault condition of the battery pack can be accurately detected.
Referring to fig. 3, the insulation detection circuit further includes a first battery interface a for connecting with the positive electrode of the battery pack, a second battery interface B for connecting with the negative electrode of the battery pack, and a ground interface C for connecting with the shell of the electric vehicle, and a first switch S1, a second switch S2, a first measuring resistor R0PA second measuring resistor R0NThe sampling resistor comprises a first sampling resistor R1, a second sampling resistor R2, a third sampling resistor R3 and a fourth sampling resistor R4; wherein the first measuring resistance R0PAnd the second measuring resistor R0NAre equal;
a first terminal of the first switch S1 is connected to the first battery interface A, and a second terminal of the first switch S1 is connected to the first measuring resistor R0PThe first measuring resistor R0PThe second end of the second terminal is connected with the grounding interface C;
a first end of the first sampling resistor R1 is connected to the first battery interface a, a second end of the first sampling resistor R1 is connected to a first end of the second sampling resistor R2, and a second end of the second sampling resistor R2 is connected to the ground interface C;
a first terminal of the second switch S2 is connected to the second battery interface B, and a second terminal of the second switch S2 is connected to the second measuring resistor R0NThe second measuring resistance R0NThe second end of the second terminal is connected with the grounding interface C;
a first end of the third sampling resistor R3 is connected to the second battery interface B, a second end of the third sampling resistor R3 is connected to a first end of the fourth sampling resistor R4, and a second end of the fourth sampling resistor R4 is connected to the ground interface C;
in said additional branchThe switch being a third switch S3, the resistance in the additional branch being a third measuring resistance RP0；
A first terminal of the third switch S3 is connected to the first battery interface A, and a second terminal of the third switch S3 is connected to the third measuring resistor RP0The third measuring resistance RP0Is connected to the ground interface C.
Fig. 4 is a schematic view of an application scenario of an insulation detection circuit according to an embodiment of the insulation fault detection method provided in the present invention.
In practical application, the first battery interface a of the insulation detection circuit is connected to the positive electrode side of the battery pack Ubat, the second battery interface B is connected to the negative electrode side of the battery pack Ubat, and the grounding interface C is connected to the shell of the electric vehicle to be grounded.
On the basis of the above embodiment, as a preferred embodiment, the insulation fault detection method further includes the steps of:
and S4, when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is not smaller than a preset threshold value, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault or the insulation detection circuit of the battery pack is invalid.
It can be understood that when the switch in the additional branch of the insulation detection circuit is in a closed state, when the insulation resistance value of the battery pack is determined to be the equivalent insulation resistance value on the positive electrode side of the battery pack, whether the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value is further determined, and if so, the following two situations may occur: firstly, the insulation detection circuit fails, so that the calculation of the insulation resistance value of the battery pack is deviated; secondly, the resistance value of the positive electrode side of the battery pack to the ground insulation resistor is small, so that the calculated insulation resistance value of the battery pack exceeds a preset calculation precision threshold value, namely, the battery pack has an insulation fault.
On the basis of the above embodiment, as a preferred embodiment, the insulation fault detection method further includes the steps of:
and S5, when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the negative electrode side of the battery pack, judging that the fault detection result of the battery pack is that the insulation fault occurs to the battery pack.
It can be understood that, when the switch in the additional branch of the insulation detection circuit is in a closed state, if the insulation of the battery pack is normal, since the positive electrode side equivalent insulation resistance value of the battery pack is equal to the parallel value of the positive electrode side insulation resistance of the battery pack and the resistance in the additional branch, and the negative electrode side insulation resistance value of the battery pack tends to infinity, the negative electrode side insulation resistance value of the battery pack should be greater than the positive electrode side equivalent insulation resistance value, when the insulation resistance value of the battery pack is determined to be the negative electrode side equivalent insulation resistance value of the battery pack, it is determined that the negative electrode side equivalent insulation resistance value of the battery pack is smaller than the positive electrode side equivalent insulation resistance value at this time, that is, the insulation fault of the battery pack occurs.
On the basis of the foregoing embodiment, as a preferred implementation, the step S2 specifically includes:
s21, acquiring a first positive electrode side voltage to ground and a first negative electrode side voltage to ground of the battery pack;
s22, judging whether the positive electrode side of the battery pack is the side with larger voltage to earth according to the first positive electrode side voltage to earth and the first negative electrode side voltage to earth, and controlling the first switch to be closed when the judgment result is yes, and controlling the second switch to be closed when the judgment result is no;
s23, acquiring a second positive side voltage-to-ground voltage, a second negative side voltage-to-ground voltage and a first time when the positive side voltage-to-ground voltage and the negative side voltage-to-ground voltage of the battery pack are detected to reach steady states; wherein the first time is a time required for the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack to reach a steady state from the first switch or the second switch being closed;
s24, when the judgment result is yes, calculating a cathode-side equivalent insulation resistance value of the battery pack according to the first anode-side voltage to earth, the first cathode-side voltage to earth, the second anode-side voltage to earth, the second cathode-side voltage to earth and the resistance value of the first measuring resistor, and taking the cathode-side equivalent insulation resistance value of the battery pack as the insulation resistance value of the battery pack;
and S25, when the judgment result is negative, calculating a positive electrode equivalent insulation resistance value of the battery pack according to the first positive electrode side voltage to ground, the first negative electrode side voltage to ground, the second positive electrode side voltage to ground, the second negative electrode side voltage to ground, the resistance value of the second measuring resistor and the resistance value of the third measuring resistor, and taking the positive electrode equivalent insulation resistance value of the battery pack as the insulation resistance value of the battery pack.
Specifically, based on the balanced bridge method, the voltage is measured according to a first positive-side voltage to ground, a first negative-side voltage to ground, a second positive-side voltage to ground, a second negative-side voltage to ground, and a first measurement resistor R0PThe resistance value of the cathode side earth insulation resistor of the battery pack can be obtained through calculation, and the equivalent insulation resistance value of the cathode side of the battery pack is equal to the resistance value of the cathode side earth insulation resistor of the battery pack; based on the balanced bridge method, the resistance value of the positive electrode side ground insulation resistor of the battery pack can be calculated according to the first positive electrode side ground voltage, the first negative electrode side ground voltage, the second positive electrode side ground voltage, the second negative electrode side ground voltage and the resistance value of the second measuring resistor, and it can be understood that the positive electrode side equivalent insulation resistance value of the battery pack is equal to the parallel connection value of the positive electrode side ground insulation resistor and the third measuring resistor of the battery pack.
Further, the step S21 specifically includes:
s211, controlling the first switch and the second switch to be switched off;
s212, periodically sampling the voltage to earth on the positive side and the voltage to earth on the negative side of the battery pack;
s213, when detecting that the change value of the voltage to earth on the positive electrode side and the change value of the voltage to earth on the negative electrode side in two adjacent sampling are smaller than a preset voltage threshold value, determining that the voltage to earth on the positive electrode side and the voltage to earth on the negative electrode side of the battery pack reach steady states;
and S214, acquiring a first positive electrode side voltage to ground and a first negative electrode side voltage to ground of the battery pack when the battery pack reaches a steady state.
After each sampling, detecting a change value of the voltage to earth of the positive side obtained by the current sampling compared with the voltage to earth of the positive side obtained by the last sampling, and a change value of the voltage to earth of the negative side obtained by the current sampling compared with the voltage to earth of the negative side obtained by the last sampling, and determining that the voltage to earth of the positive side and the voltage to earth of the negative side of the battery pack reach steady states when detecting that the change values of the two are smaller than a preset voltage threshold. In specific implementation, the sampling period may be set according to an actual situation, the voltage threshold may be preset according to the resolution and precision of voltage sampling, without affecting the beneficial effects of the present invention, and optionally, the preset voltage threshold is 1V.
In the preferred embodiment, after the first switch or the second switch is closed, when it is detected that the external insulation environment reaches the steady state, the insulation resistance value of the battery pack is calculated, so that the condition that the insulation resistance value is calculated inaccurately because the external insulation environment does not reach the steady state is avoided, and the calculation accuracy of the insulation resistance value of the battery pack is improved.
On the basis of the foregoing embodiment, as a preferred implementation manner, the performing, by the insulation detection circuit, insulation fault detection on the battery pack to obtain a fault detection result of the battery pack specifically includes:
judging whether the first time is less than or equal to an early warning time threshold value, if so, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault; if not, judging that the fault detection result of the battery pack is that the battery pack has no insulation fault; the early warning time threshold is configured according to the capacity value of the Y capacitor of the battery pack, the fault threshold of the insulation resistance of the battery pack to the ground and the time constant coefficient of the insulation detection circuit.
After the state of the first switch or the second switch is changed, whether the first time required by the positive-side voltage to earth and the negative-side voltage to earth of the battery pack to reach a stable state is smaller than or equal to an early warning time threshold value configured according to the capacity value of the Y capacitor of the battery pack, the fault threshold value of the insulation resistance to earth of the battery pack and a time constant coefficient of the insulation detection circuit is judged, if yes, the insulation resistance value to earth of the battery pack reaches the fault threshold value, so that the battery pack is judged to have an insulation fault, and if not, the insulation resistance value to earth of the battery pack does not reach the fault threshold value, so that the battery pack is judged not to have the insulation fault. The capacitance value of the Y capacitor of the battery pack can be measured by external equipment before the vehicle is subjected to strong inspection.
In this preferred embodiment, after the insulation detection circuit is determined to be valid, it is further determined whether first time required for the positive side voltage to ground and the negative side voltage to ground of the battery pack to reach a steady state after the first switch or the second switch is closed by the insulation detection circuit is less than or equal to an early warning time threshold, if so, it is determined that the battery pack has an insulation fault, if not, it is determined that the battery pack has no insulation fault, and it is further possible to accurately determine whether the battery pack has an insulation fault when insulation performance of both the positive and negative terminals of the battery pack to the ground decreases simultaneously.
Specifically, the early warning time threshold is calculated and obtained through the following formula:
△t′p＝fp×Cp×RG
of formula (II b), △ t'pThe early warning time threshold value is obtained; f. ofpIs a time constant coefficient of the insulation detection circuit; cpThe capacitance value of the Y capacitor of the battery pack is shown; rGWhen the insulation resistance value of the positive electrode side of the battery pack to the ground is equal to the fault threshold value of the insulation resistance of the battery pack to the ground, the equivalent resistance value of the positive electrode side of the battery pack to the ground is obtained;
wherein R isGIs calculated byThe method specifically comprises the following steps:
in the formula, RalarmAnd the failure threshold value of the insulation resistance of the battery pack to the ground is set.
Further, the product of the time constant coefficient of the insulation detection circuit and the capacity value of the Y capacitor of the battery pack is obtained in advance by:
s31, closing the third switch when the battery pack is in a normal insulation state;
s32, closing the first switch after closing the third switch;
s33, when it is detected that the voltages to earth on the positive side and the negative side of the battery pack reach steady state, acquiring a second time △ tpWherein the second time is △ tpA time required for the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack to reach a steady state from the closing of the first switch;
s34, passing formula
Calculating a product f between a time constant coefficient of the insulation detection circuit and a capacitance value of the Y capacitor of the battery packp×Cp(ii) a Wherein R isP0Is the resistance value of the third measuring resistor, R1Is the resistance value, R, of the first sampling resistor2The resistance value of the second sampling resistor is obtained;
and S35, controlling the first switch and the third switch to be switched off.
It is understood that, in the case where the third switch S3 is closed, the positive electrode side equivalent resistance value of the battery pack is as follows:
and when the battery pack is in a normally insulated state, the positive electrode side of the battery pack faces the groundInsulation resistance value RPTends to be infinite, and thus
Further according to Δ tP＝fP×RPG×CPIs calculated to obtain
On the basis of the above-described embodiment, as a preferred embodiment, whether the voltages to ground on the positive side and the negative side of the battery pack reach steady states is detected by:
periodically sampling the voltage to earth on the positive side and the voltage to earth on the negative side of the battery pack;
when the change value of the voltage to earth of the positive side and the change value of the voltage to earth of the negative side in two adjacent sampling are detected to be smaller than a preset voltage threshold value, the voltage to earth of the positive side and the voltage to earth of the negative side of the battery pack are judged to reach steady states.
After each sampling, detecting a change value of the voltage to earth of the positive side obtained by the current sampling compared with the voltage to earth of the positive side obtained by the last sampling, and a change value of the voltage to earth of the negative side obtained by the current sampling compared with the voltage to earth of the negative side obtained by the last sampling, and determining that the voltage to earth of the positive side and the voltage to earth of the negative side of the battery pack reach steady states when detecting that the change values of the two are smaller than a preset voltage threshold. In specific implementation, the sampling period may be set according to an actual situation, the voltage threshold may be preset according to the resolution and precision of voltage sampling, without affecting the beneficial effects of the present invention, and optionally, the preset voltage threshold is 1V.
The embodiment of the invention also provides an insulation fault detection device which can implement all the processes of the insulation fault detection method.
Fig. 5 is a schematic structural diagram of an embodiment of the insulation fault detection apparatus provided in the present invention.
An embodiment of the present invention provides an insulation fault detection apparatus, including:
a switch control module 21 for closing the switches in the additional branches of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel;
an insulation resistance value calculation module 22 for calculating an insulation resistance value of the battery pack; the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack;
and the insulation fault determination module 23 is configured to determine that the insulation detection circuit is valid when it is determined that the insulation resistance value of the battery pack is the equivalent insulation resistance value on the positive electrode side of the battery pack and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, and perform insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack.
In specific implementation, the insulation fault detection method and the insulation fault detection device provided by the embodiment of the invention can be applied to an electric vehicle to obtain an accurate insulation fault detection result, so that the accuracy of insulation fault detection is improved, and the safety of the power vehicle is improved.
The embodiment of the invention also provides an electric automobile which comprises an automobile shell, a battery pack, an insulation detection circuit and the insulation fault detection device in the embodiment. The insulation fault detection device is applied to the electric automobile, and the principle of performing insulation fault detection on the battery pack is the same as that of the embodiment, and is not repeated herein.
According to the insulation fault detection device and the electric automobile provided by the embodiment of the invention, the switch in the additional branch of the insulation detection circuit is closed; calculating an insulation resistance value of the battery pack; and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and performing insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack. When the insulation detection is carried out, whether the insulation resistance value of the battery pack is the equivalent insulation resistance value of the positive electrode side of the battery pack is judged, whether the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value is judged, whether the insulation detection circuit is effective is judged, and after the insulation detection circuit is judged to be effective, the insulation fault detection is carried out on the battery pack through the insulation detection circuit, so that the fault detection result of the battery pack is obtained, the problem that the fault detection result of the inaccurate battery pack is easily obtained due to the fact that the effectiveness of the insulation detection circuit is not detected in the insulation fault detection process of the battery pack in the prior art is solved, and the insulation fault condition of the battery pack can be accurately detected.
Fig. 6 is a schematic structural diagram of an embodiment of the terminal device provided in the present invention.
The embodiment of the present invention provides a terminal device, which includes a processor 31, a memory 32, and a computer program stored in the memory 32 and configured to be executed by the processor 31, and when the processor 31 executes the computer program, the insulation fault detection method according to any one of the above embodiments is implemented.
In addition, an embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the insulation fault detection method according to any one of the above embodiments.
The processor 31, when executing the computer program, implements the steps in the various insulation fault detection method embodiments described above, such as all the steps of the insulation fault detection method shown in fig. 2. Alternatively, the processor 31, when executing the computer program, implements the functions of the modules/units in the embodiments of the insulation fault detection apparatus, for example, the functions of the modules of the insulation fault detection apparatus shown in fig. 5.
Illustratively, the computer program may be divided into one or more modules, which are stored in the memory 32 and executed by the processor 31 to accomplish the present invention. The one or more modules may be a series of computer program instruction segments capable of performing specific functions, which are used for describing the execution process of the computer program in the terminal device. For example, the computer program may be divided into a switch control module, an insulation resistance value calculation module, and an insulation failure determination module, and the specific functions of each module are as follows: the switch control module is used for closing a switch in an additional branch of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel; the insulation resistance value calculation module is used for calculating the insulation resistance value of the battery pack; the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack; and the insulation fault determination module is used for determining that the insulation detection circuit is effective when the insulation resistance value of the battery pack is determined to be the equivalent insulation resistance value of the positive electrode side of the battery pack and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, and performing insulation fault detection on the battery pack through the insulation detection circuit so as to obtain a fault detection result of the battery pack.
The terminal device can be a desktop computer, a notebook, a palm computer, a cloud server and other computing devices. The terminal device may include, but is not limited to, a processor 31, a memory 32. It will be appreciated by those skilled in the art that the schematic diagram is merely an example of a terminal device and does not constitute a limitation of a terminal device, and may include more or less components than those shown, or combine certain components, or different components, for example, the terminal device may also include input output devices, network access devices, buses, etc.
The Processor 31 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may be any conventional processor or the like, and the processor 31 is a control center of the terminal device and connects various parts of the whole terminal device by using various interfaces and lines.
The memory 32 can be used for storing the computer programs and/or modules, and the processor 31 can implement various functions of the terminal device by running or executing the computer programs and/or modules stored in the memory 32 and calling the data stored in the memory 32. The memory 32 may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application program required by at least one function (such as a sound playing function, an image playing function, etc.), and the like; the storage data area may store data (such as audio data, a phonebook, etc.) created according to the use of the cellular phone, and the like. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.
Wherein, the terminal device integrated module/unit can be stored in a computer readable storage medium if it is implemented in the form of software functional unit and sold or used as a stand-alone product. Based on such understanding, all or part of the flow of the method according to the embodiments of the present invention may also be implemented by a computer program, which may be stored in a computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method embodiments may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, Read-Only Memory (ROM), Random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like.
It should be noted that the above-described device embodiments are merely illustrative, where the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. In addition, in the drawings of the embodiment of the apparatus provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, and may be specifically implemented as one or more communication buses or signal lines. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (13)
1. An insulation fault detection method, comprising:
closing a switch in an additional branch of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel;
calculating an insulation resistance value of the battery pack; the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack;
and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, judging that the insulation detection circuit is effective, and performing insulation fault detection on the battery pack through the insulation detection circuit to obtain a fault detection result of the battery pack.
2. The insulation fault detection method according to claim 1, wherein the insulation detection circuit further comprises a first battery interface for connecting with a positive electrode of the battery pack, a second battery interface for connecting with a negative electrode of the battery pack, and a ground interface for connecting with a shell of an electric vehicle, and a first measuring resistor, a second measuring resistor, a first sampling resistor, a second sampling resistor, a third sampling resistor, and a fourth sampling resistor; the resistance value of the first measuring resistor is equal to that of the second measuring resistor;
the first end of the first switch is connected with the first battery interface, the second end of the first switch is connected with the first end of the first measuring resistor, and the second end of the first measuring resistor is connected with the grounding interface;
the first end of the first sampling resistor is connected with the first battery interface, the second end of the first sampling resistor is connected with the first end of the second sampling resistor, and the second end of the second sampling resistor is connected with the grounding interface;
the first end of the second switch is connected with the second battery interface, the second end of the second switch is connected with the first end of the second measuring resistor, and the second end of the second measuring resistor is connected with the grounding interface;
the first end of the third sampling resistor is connected with the second battery interface, the second end of the third sampling resistor is connected with the first end of the fourth sampling resistor, and the second end of the fourth sampling resistor is connected with the grounding interface;
the switch in the additional branch is a third switch, and the resistor in the additional branch is a third measuring resistor;
the first end of the third switch is connected with the first battery interface, the second end of the third switch is connected with the first end of the third measuring resistor, and the second end of the third measuring resistor is connected with the grounding interface.
3. The insulation fault detection method according to claim 1 or 2, further comprising the steps of:
and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the positive electrode side of the battery pack, and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is not smaller than a preset threshold value, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault or an insulation detection circuit of the battery pack is invalid.
4. The insulation fault detection method according to claim 1 or 2, further comprising the steps of:
and when the insulation resistance value of the battery pack is judged to be the equivalent insulation resistance value of the negative electrode side of the battery pack, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault.
5. The insulation fault detection method according to claim 2, wherein the calculating of the insulation resistance value of the battery pack specifically includes:
acquiring a first positive side voltage to ground and a first negative side voltage to ground of the battery pack;
judging whether the positive electrode side of the battery pack is the side with larger voltage to earth according to the first positive electrode side voltage to earth and the first negative electrode side voltage to earth, and controlling the first switch to be closed when the judgment result is yes, and controlling the second switch to be closed when the judgment result is no;
acquiring a second positive-side voltage-to-ground voltage, a second negative-side voltage-to-ground voltage, and a first time when it is detected that the positive-side voltage-to-ground voltage and the negative-side voltage-to-ground voltage of the battery pack reach steady states; wherein the first time is a time required for the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack to reach a steady state from the first switch or the second switch being closed;
when the judgment result is yes, calculating a cathode-side equivalent insulation resistance value of the battery pack according to the first anode-side voltage-to-ground voltage, the first cathode-side voltage-to-ground voltage, the second anode-side voltage-to-ground voltage, the second cathode-side voltage-to-ground voltage and the resistance value of the first measuring resistor, and taking the cathode-side equivalent insulation resistance value of the battery pack as the insulation resistance value of the battery pack;
and when the judgment result is negative, calculating the anode-side equivalent insulation resistance value of the battery pack according to the first anode-side voltage to earth, the first cathode-side voltage to earth, the second anode-side voltage to earth, the second cathode-side voltage to earth, the resistance value of the second measuring resistor and the resistance value of the third measuring resistor, and taking the anode-side equivalent insulation resistance value of the battery pack as the insulation resistance value of the battery pack.
6. The insulation fault detection method according to claim 5, wherein the insulation fault detection is performed on the battery pack by the insulation detection circuit to obtain a fault detection result of the battery pack, and specifically:
judging whether the first time is less than or equal to an early warning time threshold value, if so, judging that the fault detection result of the battery pack is that the battery pack has an insulation fault; if not, judging that the fault detection result of the battery pack is that the battery pack has no insulation fault; the early warning time threshold is configured according to the capacity value of the Y capacitor of the battery pack, the fault threshold of the insulation resistance of the battery pack to the ground and the time constant coefficient of the insulation detection circuit.
7. The insulation fault detection method of claim 6, wherein the early warning time threshold is calculated by the following formula:
△t′p＝fp×Cp×RG
of formula (II b), △ t'pThe early warning time threshold value is obtained; f. ofpIs a time constant coefficient of the insulation detection circuit; cpThe capacitance value of the Y capacitor of the battery pack is shown; rGWhen the insulation resistance value of the positive electrode side of the battery pack to the ground is equal to the fault threshold value of the insulation resistance of the battery pack to the ground, the equivalent resistance value of the positive electrode side of the battery pack to the ground is obtained;
wherein R isGThe calculation formula is specifically as follows:
in the formula, RalarmAnd the failure threshold value of the insulation resistance of the battery pack to the ground is set.
8. The insulation fault detection method according to claim 7, wherein a product between a time constant coefficient of the insulation detection circuit and a capacity value of a Y capacitor of the battery pack is obtained in advance by:
when the battery pack is in a normal insulation state, closing the third switch;
after closing the third switch, closing the first switch;
acquiring a second time △ t when it is detected that the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack reach steady statespWherein the second time is △ tpA time required for the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack to reach a steady state from the closing of the first switch;
by the formula
Calculating a product f between a time constant coefficient of the insulation detection circuit and a capacitance value of the Y capacitor of the battery packp×Cp(ii) a Wherein R isP0Is the resistance value of the third measuring resistor, R1Is the resistance value, R, of the first sampling resistor2The resistance value of the second sampling resistor is obtained;
controlling the first switch and the third switch to be turned off.
9. The insulation fault detection method according to claim 5 or 8, wherein whether the voltage to ground on the positive side and the voltage to ground on the negative side of the battery pack reach steady states is detected by:
periodically sampling the voltage to earth on the positive side and the voltage to earth on the negative side of the battery pack;
when the change value of the voltage to earth of the positive side and the change value of the voltage to earth of the negative side in two adjacent sampling are detected to be smaller than a preset voltage threshold value, the voltage to earth of the positive side and the voltage to earth of the negative side of the battery pack are judged to reach steady states.
10. An insulation fault detection apparatus, comprising:
the switch control module is used for closing a switch in an additional branch of the insulation detection circuit; the additional branch circuit is formed by connecting a switch and a resistor in series, and is connected between the positive electrode side of the battery pack and the ground in parallel;
the insulation resistance value calculation module is used for calculating the insulation resistance value of the battery pack; the insulation resistance value of the battery pack is equal to the smaller one of the positive electrode side equivalent insulation resistance value and the negative electrode side equivalent insulation resistance value of the battery pack;
and the insulation fault determination module is used for determining that the insulation detection circuit is effective when the insulation resistance value of the battery pack is determined to be the equivalent insulation resistance value of the positive electrode side of the battery pack and the relative deviation between the insulation resistance value of the battery pack and the resistance value of the resistor in the additional branch is smaller than a preset threshold value, and performing insulation fault detection on the battery pack through the insulation detection circuit so as to obtain a fault detection result of the battery pack.
11. An electric vehicle characterized by comprising a vehicle body case, a battery pack, an insulation detection circuit, and the insulation failure detection device according to claim 10.
12. A terminal device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor implementing the insulation fault detection method according to any one of claims 1 to 9 when executing the computer program.
13. A computer-readable storage medium, characterized in that the computer-readable storage medium comprises a stored computer program, wherein the computer program, when running, controls an apparatus in which the computer-readable storage medium is located to perform the insulation fault detection method according to any one of claims 1 to 9.
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