Ac insulation impedance detection method and device based on insulation detection circuit

Abstract

The application relates to an alternating current insulation impedance detection method and device based on an insulation detection circuit. The insulation detection circuit comprises first to Mth resistors, first to second capacitors and a single-pole multi-throw switch. The method comprises the following steps: respectively controlling the first to Nth movable terminals and the fixed terminal of the single-pole multi-throw switch to be closed, collecting the first to Nth peak voltages of the Mth-2 resistor, the first alternating current voltage between the two ends of the Mth-2 resistor and the first to Nth phase differences between the alternating current voltage and the alternating current input voltage, calculating the fire line-to-ground insulation impedance and the zero line-to-ground insulation impedance according to the first to Nth peak voltages and the first to Nth phase differences, and determining that the fire line-to-ground insulation impedance fails when the fire line-to-ground insulation impedance is smaller than a preset threshold value, and determining that the zero line-to-ground insulation impedance fails when the zero line-to-ground insulation impedance is smaller than the preset threshold value. Therefore, the problem that the resistance impedance and the capacitance impedance component cannot be identified in the alternating current insulation impedance detection is solved, and the accuracy of detecting the external impedance value is improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to an AC insulation impedance detection method and device based on an insulation detection circuit. Background Technology

[0002] Insulation resistance is a standard for judging the insulation performance of an electrical system. For high-voltage energy storage systems, it is important to test the insulation resistance of the positive and negative busbars of the battery clusters to ground.

[0003] In related technologies, the commonly used methods for testing DC insulation circuits mainly include the balanced bridge method and the unbalanced bridge method. For example... Figure 1 As shown, the balanced bridge method involves connecting a large detection resistor R1 and R2 in parallel with the positive insulation resistance Rx (V1) and the negative insulation resistance Ry (V2), respectively. When the insulation resistance on one side decreases, the voltage on that side will be rapidly pulled down, thus detecting the fault and the resistance value. Figure 2 As shown, the unbalanced bridge method adds a switch and a resistor on each side compared to the balanced bridge method. By alternately switching the switches on both sides, the equivalent resistance of the two poles to ground is changed, and the unbalanced detection voltage on the positive and negative detection resistors is obtained, thereby calculating the insulation resistance of the positive and negative poles.

[0004] In related technologies, AC insulation detection circuits are commonly used in inverters and onboard chargers (OBCs). They can also be tested using balanced and unbalanced bridge methods, except that the DC voltage between the positive and negative insulation resistances is replaced by an AC voltage. Similarly, the AC voltage divider resistors of the detection resistor are used to detect the AC peak value or effective value. The insulation resistance value is then obtained by solving a two-variable linear equation.

[0005] However, in DC detection schemes, the presence of capacitors can be ignored, while in AC circuits, the presence of capacitors is related to the AC frequency and capacitance value, resulting in capacitive reactance. Currently, traditional balanced bridge and unbalanced bridge methods cannot identify resistive impedance and capacitive reactance components in AC insulation impedance testing, resulting in inaccurate detection of external impedance values. Furthermore, the influence of the Y capacitor is significant in both balanced and unbalanced bridge methods. Summary of the Invention

[0006] This application provides an AC insulation impedance detection method and apparatus based on an insulation detection circuit to solve the problems in related technologies, such as the inability to identify resistive impedance and capacitive reactance components in AC insulation impedance detection, and effectively improves the accuracy of detecting external impedance values.

[0007] The first aspect of this application provides an AC insulation impedance detection method based on an insulation detection circuit. The insulation detection circuit includes first to M resistors, first to second capacitors, and a single-pole multi-throw switch. One end of the first to M-3 resistors is connected to the first to Nth moving terminals of the single-pole multi-throw switch, respectively. One end of the M-2 resistor is connected to the stationary terminal of the single-pole multi-throw switch. The other ends of the first to M-3 resistors and one end of the M-1 resistor are both connected to the live wire. The other end of the M-1 resistor is grounded. The other ends of the M-2 resistor and one end of the M resistor are both connected to the other end of the M-1 resistor. The other end of the M resistor is connected to the neutral wire. One end of the first capacitor is connected to one end of the M-1 resistor. The other end of the first capacitor is grounded. One end of the second capacitor is connected to the other end of the first capacitor. The other end of the second capacitor is connected to the other end of the M resistor. N and M are both integers, and M ≥ 5, N = M - 3. The method includes the following steps:

[0008] The first to Nth moving terminals and the fixed terminals are controlled to close respectively, and the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage and the AC input voltage across the (M-2)th resistor are collected.

[0009] The insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground are calculated based on the first to Nth peak voltages and the first to Nth phase differences. If the insulation impedance of the live wire to ground is less than a first preset threshold, the insulation impedance of the live wire to ground is determined to be faulty. If the insulation impedance of the neutral wire to ground is less than a second preset threshold, the insulation impedance of the neutral wire to ground is determined to be faulty.

[0010] Optionally, in some embodiments, calculating the insulation resistance of the live wire to ground and the insulation resistance of the neutral wire to ground based on the first to Nth peak voltages and the first to Nth phase differences includes:

[0011] The impedance values ​​of the (M-2)th resistor, the (M-1)th resistor, the capacitive reactance of the first capacitor, and the capacitive reactance of the second capacitor are calculated based on the first to Nth peak voltages and the first to Nth phase differences. The insulation impedance of the live wire to ground is obtained by performing parallel impedance calculation on the impedance value of the (M-2)th resistor and the capacitive reactance of the first capacitor. The insulation impedance of the neutral wire to ground is obtained by performing parallel impedance calculation on the impedance value of the (M-1)th resistor and the capacitive reactance of the second capacitor.

[0012] Optionally, in some embodiments, after acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the method further includes:

[0013] If the first to Nth peak voltages are all less than the corresponding third preset threshold, it is determined that the impedance of the (M-1)th resistor and the first capacitor has decreased; if the first to Nth peak voltages are all greater than the corresponding fourth preset threshold, it is determined that the impedance of the Mth resistor and the second capacitor has decreased.

[0014] Optionally, in some embodiments, after acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the method further includes:

[0015] If a portion of the peak voltages from the first to the Nth peak voltages is greater than the corresponding third preset threshold, and the remaining portion is less than the corresponding third preset threshold, or if a portion of the peak voltages from the first to the Nth peak voltages is greater than the corresponding fourth preset threshold, and the remaining portion is less than the corresponding fourth preset threshold, then the current AC insulation impedance detection is determined to be faulty.

[0016] Optionally, in some embodiments, the resistance values ​​of the first resistor to the (M-3)th resistor are different.

[0017] A second aspect of this application provides an AC insulation impedance detection device based on an insulation detection circuit. The insulation detection circuit includes first to M resistors, first to second capacitors, and a single-pole multi-throw switch. One end of the first to M-3 resistors is connected to the first to Nth moving terminals of the single-pole multi-throw switch, respectively. One end of the M-2 resistor is connected to the stationary terminal of the single-pole multi-throw switch. The other ends of the first to M-3 resistors and one end of the M-1 resistor are both connected to the live wire. The other end of the M-1 resistor is grounded. The other ends of the M-2 resistor and one end of the M resistor are both connected to the other end of the M-1 resistor. The other end of the M resistor is connected to the neutral wire. One end of the first capacitor is connected to one end of the M-1 resistor, and the other end of the first capacitor is grounded. One end of the second capacitor is connected to the other end of the first capacitor, and the other end of the second capacitor is connected to the other end of the M resistor. N and M are both integers, and M ≥ 5, N = M - 3. The device includes:

[0018] The acquisition module is used to control the closing of the first to Nth moving terminals and the stationary terminals respectively, acquire the first to Nth peak voltages of the (M-2)th resistor, and the first to Nth phase differences between the first AC voltage and the AC input voltage across the (M-2)th resistor;

[0019] The determination module is used to calculate the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground based on the first to Nth peak voltages and the first to Nth phase differences, and to determine that the insulation impedance of the live wire to ground is faulty when the insulation impedance of the live wire to ground is less than a first preset threshold, and to determine that the insulation impedance of the neutral wire to ground is faulty when the insulation impedance of the neutral wire to ground is less than a second preset threshold.

[0020] Optionally, in some embodiments, the determination module includes:

[0021] The first calculation unit is used to calculate the impedance value of the (M-2)th resistor, the impedance value of the (M-1)th resistor, the capacitive reactance value of the first capacitor, and the capacitive reactance value of the second capacitor based on the first to Nth peak voltages and the first to Nth phase differences; the second calculation unit is used to perform parallel impedance calculation on the impedance value of the (M-2)th resistor and the capacitive reactance value of the first capacitor to obtain the insulation impedance of the live wire to ground, and to perform parallel impedance calculation on the impedance value of the (M-1)th resistor and the capacitive reactance value of the second capacitor to obtain the insulation impedance of the neutral wire to ground.

[0022] Optionally, in some embodiments, after acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the acquisition module further includes:

[0023] The first judgment unit is used to determine that the impedance of the (M-1)th resistor and the first capacitor is reduced when the peak voltages from the first to the Nth are all less than the corresponding third preset threshold; the second judgment unit is used to determine that the impedance of the Mth resistor and the second capacitor is reduced when the peak voltages from the first to the Nth are all greater than the corresponding fourth preset threshold.

[0024] Optionally, in some embodiments, after acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the acquisition module further includes:

[0025] The third judgment unit is used to determine that the current AC insulation resistance detection has failed when some of the peak voltages from the first to the Nth peak voltages are greater than the corresponding third preset threshold and the remaining peak voltages are less than the corresponding third preset threshold, or when some of the peak voltages from the first to the Nth peak voltages are greater than the corresponding fourth preset threshold and the remaining peak voltages are less than the corresponding fourth preset threshold.

[0026] Optionally, in some embodiments, the resistance values ​​of the first resistor to the (M-3)th resistor are different.

[0027] A third aspect of this application provides an on-board charger inverter, which includes an AC insulation impedance detection device based on an insulation detection circuit as described in the above embodiments.

[0028] A fourth aspect of this application provides a vehicle that includes an on-board charger inverter as described above.

[0029] Therefore, this application utilizes an insulation detection circuit composed of first to M resistors, first to second capacitors, and a single-pole multi-throw switch. By controlling the closing of the first to N moving and stationary terminals of the single-pole multi-throw switch respectively, it collects the first to N peak voltages of the (M-2)th resistor and the first to N phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage. Based on the first to N peak voltages and the first to N phase differences, it calculates the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground. If the insulation impedance of the live wire to ground is less than a first preset threshold, it is determined that the insulation impedance of the live wire to ground has failed; similarly, if the insulation impedance of the neutral wire to ground is less than a second preset threshold, it is determined that the insulation impedance of the neutral wire to ground has failed. Thus, this application can identify the resistive and capacitive components in the insulation impedance through phase detection, thereby solving the problem in related technologies where resistive impedance and capacitive reactance components cannot be identified in AC insulation impedance detection, effectively improving the accuracy of detecting external impedance values.

[0030] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0031] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 This is a schematic diagram of the circuit principle of the balanced bridge method in related technologies;

[0033] Figure 2 This is a schematic diagram of the unbalanced bridge circuit principle in related technologies;

[0034] Figure 3 This is a schematic diagram illustrating the principle of unbalanced bridge circuit detection in related technologies;

[0035] Figure 4 This is a schematic diagram of an insulation detection circuit provided according to an embodiment of this application;

[0036] Figure 5 This is a flowchart of an AC insulation impedance detection method based on an insulation detection circuit according to an embodiment of this application;

[0037] Figure 6This is a schematic diagram of an insulation detection circuit according to a specific embodiment of this application;

[0038] Figure 7 This is a waveform diagram of the initial state according to a specific embodiment of this application;

[0039] Figure 8 This is a waveform diagram showing the reduced insulation resistance of the live wire to ground according to a specific embodiment of this application;

[0040] Figure 9 This is a waveform diagram showing the further reduction of the live wire-to-ground insulation impedance according to a specific embodiment of this application;

[0041] Figure 10 This is a schematic diagram of an equivalent circuit according to a specific embodiment of this application;

[0042] Figure 11 This is a schematic diagram of an equivalent circuit according to another specific embodiment of this application;

[0043] Figure 12 This is a block diagram of an AC insulation impedance detection device based on an insulation detection circuit according to an embodiment of this application. Detailed Implementation

[0044] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0045] The following describes, with reference to the accompanying drawings, an AC insulation impedance detection method, apparatus, on-board charger inverter, and vehicle based on an insulation detection circuit according to embodiments of this application. Addressing the problem mentioned in the background art of being unable to identify resistive impedance and capacitive reactance components in AC insulation impedance detection, this application provides an AC insulation impedance detection method based on an insulation detection circuit. In this method, the first to Nth moving terminals and the stationary terminals are controlled to close respectively; the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage and the AC input voltage across the (M-2)th resistor are collected; the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground are calculated based on the first to Nth peak voltages and the first to Nth phase differences; and the insulation impedance of the live wire to ground is determined to be faulty when it is less than a first preset threshold, and the insulation impedance of the neutral wire to ground is determined to be faulty when it is less than a second preset threshold. This solves the problem of being unable to identify resistive impedance and capacitive reactance components in AC insulation impedance detection, effectively improving the accuracy of detecting external impedance values.

[0046] Before introducing the embodiments of this application, let's first introduce the insulation impedance detection method and its principle in related technologies.

[0047] As described in the background section, common methods for detecting DC insulation circuits include the balanced bridge method and the unbalanced bridge method. Those skilled in the art will understand that while the balanced bridge method can quickly detect faults when the insulation resistance on one side decreases significantly, it cannot identify faults when both poles simultaneously experience a decrease in insulation resistance to ground. In the unbalanced bridge method, the voltage across the positive and negative detection resistors changes with the switching cycle. When the insulation resistance of one pole decreases, the voltage across that detection resistor decreases, and the voltage across the corresponding detection resistor on the other side increases, thereby enabling the detection of DC insulation circuits.

[0048] However, the balanced bridge method and the unbalanced bridge method cannot identify the resistive impedance and capacitive reactance components in AC insulation impedance testing, resulting in the inability to accurately detect the external impedance value.

[0049] For example, such as Figure 3 As shown, during the detection process of the unbalanced bridge circuit, switches S1 and S2 are controlled by the internal circuit of the inverter. By closing S1 and opening S2, and closing S2 and opening S1, and simultaneously closing S1 and S2, the voltages at the terminals of R3 and R4 are sampled respectively (sampled AC voltage peak values, for a total of three sets of data). The values ​​of Rx, Ry, Cx, and Cy are calculated by solving equations. However, there is capacitive reactance in the external circuit being tested (AC_L and AC_N respectively have Y capacitors Cx and Cy). Therefore, the unknowns in the AC circuit become four: Rx, Ry, Cx, and Cy. The calculation process for this parallel RC condition is complex, and simply sampling the peak or effective value of the AC voltage cannot accurately determine the insulation impedance Zx (Rx in parallel with Cx) and Zy (Zy equals Ry in parallel with Cy).

[0050] Therefore, to solve the above problems, this application proposes an AC insulation impedance detection method based on an insulation detection circuit. This insulation detection circuit can be applied to on-board charger inverters and can identify resistive impedance and capacitive reactance components, thereby effectively improving the accuracy of detecting external impedance values. Specific embodiments of the AC insulation impedance detection method based on the insulation detection circuit of this application will be described in detail below with reference to the accompanying drawings.

[0051] Specifically, Figure 4 This is a schematic diagram of the insulation detection circuit provided in an embodiment of this application.

[0052] like Figure 4 As shown, the insulation detection circuit includes: first resistor R1 to M-3 resistor R M-3 The M-2 resistor R M-2 The M-1th resistor R M-1 The Mth resistor R MThe first capacitor Cx, the second capacitor Cy, and the single-pole multi-throw switch S1.

[0053] Among them, the first resistor R1 to the (M-3)th resistor R M-3 One end is connected to the first moving terminal 1 to the Nth moving terminal N of the single-pole multi-throw switch S1, respectively, and the (M-2)th resistor R M-2 One end is connected to the stationary terminal a of the single-pole multi-throw switch S1, and the first resistor R1 to the (M-3)th resistor R M-3 The other end and the (M-1)th resistor R M-1 One end of each resistor is connected to the live wire AC_L, and the (M-1)th resistor R M-1 The other end is grounded, and the (M-2)th resistor R M-2 The other end and the Mth resistor R M One end of each resistor is connected to the (M-1)th resistor R. M-1 The other end is connected to the Mth resistor R. M The other end is connected to the neutral line AC_N, and one end of the first capacitor Cx is connected to the (M-1)th resistor R. M-1 One end of the first capacitor Cx is connected to the ground, and the other end of the second capacitor Cy is connected to the other end of the first capacitor Cx. The other end of the second capacitor Cy is connected to the Mth resistor R. M The other end is connected, N and M are both integers, and M≥5, N=M-3.

[0054] It should be noted that, Figure 4 11 in the diagram refers to the internal detection circuit. Figure 4 12 in the diagram represents the external circuit being tested. The controller in the insulation detection circuit of this embodiment can sample signals, and the single-pole multi-throw switch S1 is controlled by this controller.

[0055] Optionally, in some embodiments, the resistance value of the first resistor R1 is equal to that of the (M-3)th resistor R. M-3 The resistance values ​​are different.

[0056] It is understandable that, such as Figure 4 As shown, the first resistor R1 to the (M-3)th resistor R M-3 The resistance values ​​must be different in order to accurately detect the external impedance value.

[0057] Furthermore, Figure 5 A flowchart of an AC insulation impedance detection method based on an insulation detection circuit provided in an embodiment of this application.

[0058] like Figure 5 As shown, the AC insulation impedance detection method based on the insulation detection circuit includes the following steps:

[0059] In step S501, the first to Nth moving terminals and the stationary terminals are closed respectively, and the resistance R of the (M-2)th resistor is sampled. M-2The first to Nth peak voltages, and the (M-2)th resistor R M-2 The first phase difference between the first AC voltage at both ends and the first to Nth phase difference between the AC input voltage.

[0060] Specifically, combined Figure 4 and Figure 5 This application achieves this by respectively closing the single-pole multi-throw switch S1 and the first resistor R1 to the (M-3)th resistor R M-3 The resistance R of the (M-2)th resistor can be obtained. M-2 The N sampling peak values ​​at both ends can be recorded as V in this embodiment of the application. pp1 To V ppN Record R M-2 The phase difference between the AC voltage at both ends and the first to Nth phases of the inverter AC (Alternating Current) is: to

[0061] Furthermore, in some embodiments, such as Figure 4 As shown, the resistor R of the (M-2)th resistor is sampled. M-2 The first to Nth peak voltages, and the (M-2)th resistor R M-2 After determining the phase difference between the first AC voltage at both ends and the first to Nth phase difference between the AC input voltage, the method further includes: if the first to Nth peak voltages are all less than the corresponding third preset threshold, then the (M-1)th resistor R is determined to be... M-1 There is a decrease in impedance with the first capacitor Cx. If the peak voltages from the first to the Nth are all greater than the corresponding fourth preset threshold, then the Mth resistor R is determined to be... M The impedance of the second capacitor Cy decreases.

[0062] It is understandable that, such as Figure 4 As shown, this application collects the (M-2)th resistor R M-2 The first to Nth peak values ​​and the M-2th resistance R M-2 After determining the phase difference between the first AC voltage and the first to Nth phase difference of the AC input voltage, it is necessary to compare the changes in the first to Nth phase differences with the changes that occurred before the insulation failure. Therefore, this embodiment sets a third preset threshold and a fourth preset threshold to determine the changes in the first to Nth peak voltages, respectively. If the peak voltage decreases, that is, if the first to Nth peak voltages are all less than the third preset threshold, then it is initially determined that the (M-1)th resistor R... M-1 The impedance decreases when the first capacitor Cx is connected; if the peak voltage increases, i.e., the peak voltages from the first to the Nth are all greater than the fourth preset threshold, then it is initially determined that the Mth resistor R... M The second capacitor Cy changes.

[0063] Alternatively, in some embodiments, such as Figure 4 As shown, when collecting the (M-2)th resistor RM-2 The first to Nth peak voltages, and the (M-2)th resistor R M-2 After the phase difference between the first AC voltage at both ends and the first to Nth phase difference of the AC input voltage, the following is also included: if a portion of the peak voltages among the first to Nth peak voltages is greater than the corresponding third preset threshold and the remaining portion of the peak voltages is less than the corresponding third preset threshold, or if a portion of the peak voltages among the first to Nth peak voltages is greater than the corresponding fourth preset threshold and the remaining portion is less than the corresponding fourth preset threshold, then the current AC insulation impedance detection is determined to be faulty.

[0064] Based on the above embodiments, it can be understood that the changes in the first to Nth peak voltages should be synchronous during normal detection; that is, the first to Nth peak voltages should decrease or increase simultaneously in order to accurately detect the external impedance value. Therefore, in this embodiment, if it is detected that some of the first to Nth peak voltages decrease while the remaining peak voltages increase, or if the first to Nth peak voltages increase while the remaining peak voltages decrease, it is determined that the AC insulation impedance detection has failed.

[0065] Furthermore, this application does not specifically limit the values ​​of the third preset threshold and the fourth preset threshold. The values ​​of the third preset threshold and the fourth preset threshold can be equal or different, and those skilled in the art can set them according to their needs.

[0066] In step S502, the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground are calculated based on the first to Nth peak voltages and the first to Nth phase differences. If the insulation impedance of the live wire to ground is less than the first preset threshold, the insulation impedance of the live wire to ground is determined to be faulty. If the insulation impedance of the neutral wire to ground is less than the second preset threshold, the insulation impedance of the neutral wire to ground is determined to be faulty.

[0067] Alternatively, in some embodiments, such as Figure 4 As shown, the insulation resistance of the live wire to ground and the insulation resistance of the neutral wire to ground are calculated based on the first to Nth peak voltages and the first to Nth phase differences, including: calculating the resistance R of the M-2th phase based on the first to Nth peak voltages and the first to Nth phase differences. M-2 The impedance value, the (M-1)th resistor R M-1 The impedance value, the capacitive reactance value of the first capacitor Cx, and the capacitive reactance value of the second capacitor Cy; for the (M-2)th resistor R M-2 The insulation impedance of the live wire to ground is obtained by paralleling the impedance value of the live wire and the capacitive reactance value of the first capacitor Cx, and the insulation impedance of the M-1th resistor R is calculated. M-1 The neutral-to-ground insulation impedance is obtained by paralleling the impedance value of the neutral line with the capacitive reactance value of the second capacitor Cy.

[0068] The following examples illustrate in detail the calculation of the (M-1)th resistor R in this application. M-1The parallel impedance of the first capacitor Cx is the phase impedance L. Calculate the Mth resistor R. M The process of the parallel impedance of the second capacitor Cy being the impedance of the N-phase.

[0069] Specifically, Figure 6 This is a schematic diagram of an insulation detection circuit according to a specific embodiment of this application, as shown below. Figure 6 As shown in the embodiments of this application, Assume that the switching resistor R1 (first resistor) is 1000kΩ and R2 (second resistor) is 500kΩ; in addition, the unknown quantities in the circuit are assigned the following values ​​in this embodiment: Rx:=1.2MΩ, Ry:=1MΩ, Cx:=10nF, Cy:=8nF.

[0070] It should be noted that the sampling resistor in this embodiment is used to calculate the impedance of the live wire AC_L to ground by the voltage division ratio of the resistors, and the resistance value of the sampling resistor R3 (the third resistor) is ignored in the calculation process.

[0071] In some cases, such as Figure 6 As shown, by switching the single-pole multi-throw switch S1 to the first resistor R1, the following equation can be obtained:

[0072]

[0073]

[0074] Where XC1 is the capacitive reactance of the first capacitor Cx, XC2 is the capacitive reactance of the second capacitor Cy, and the impedance is... Angular frequency ω:=2·π·f, period f:=50Hz, first capacitor Cx:=10nF, second capacitor Cy:=8nF.

[0075] In this embodiment, the first resistor R1 and the fourth resistor Rx are connected in parallel, and the resistance value is calculated as follows:

[0076]

[0077] Calculation of resistance of live wire AC_L relative to ground:

[0078]

[0079] Calculation of neutral line AC_N resistance relative to ground:

[0080]

[0081] Then, the voltage values ​​of the live wire AC_L and the neutral wire AC_N relative to ground are calculated:

[0082]

[0083]

[0084] Among them, U ac For AC voltage difference, U L U is the live wire voltage. N RL is the voltage of the neutral line, RN is the resistance of the live wire AC_L relative to ground, and RN is the resistance of the neutral wire AC_N relative to ground.

[0085] Then, calculate the peak value and argument (between -π and π):

[0086] V1:=|U L |=0.428;

[0087] θ1:=arg(U L ) = -0.086;

[0088] Where V1 is the first peak value between -π and π when the single-pole multi-throw switch S1 switches to the first resistor R1, U L θ is the live wire voltage, and θ1 is the first argument between -π and π when the single-pole multi-throw switch S1 switches to the first resistor R1.

[0089] In some cases, such as Figure 6 As shown, this application switches the single-pole multi-throw switch S1 to the second resistor R2, and calculates the parallel resistance of the second resistor R2 and the fourth resistor Rx, which yields the following formula:

[0090]

[0091] Calculation of resistance of live wire AC_L relative to ground:

[0092]

[0093] Calculation of neutral line AC_N resistance relative to ground:

[0094]

[0095] Then, the voltage values ​​of the live wire AC_L and the neutral wire AC_N relative to ground are calculated:

[0096]

[0097]

[0098] Then, calculate the peak value and argument (between -π and π):

[0099] V2:=|U L |=0.396;

[0100] θ2:=arg(U L) = -0.217;

[0101] Where V2 is the second peak value between -π and π when the single-pole multi-throw switch S1 switches to the second resistor R2, U L θ2 is the live wire voltage, and θ2 is the second argument between -π and π when the single-pole multi-throw switch S1 switches to the second resistor R2.

[0102] It should be noted that this application takes into account that in the inverter circuit, the Y capacitors Cx and Cy will cause a phase shift to the sampled voltage value. Therefore, when calculating, the phase difference between XC1 (capacitor reactance of the first capacitor Cx) and XC2 (capacitor reactance of the second capacitor Cy) and Vac is substituted to calculate the components of the capacitor reactance jwc and impedance R in the impedance Z. The phase angle can be the time difference for detecting the zero crossing point or the time difference for sampling the peak voltage.

[0103] Therefore, based on the above calculations, this application can solve for the values ​​of the fourth resistor Rx, the fifth resistor Ry, the first capacitor Cx, and the second capacitor Cy by simultaneously solving the system of equations relating the first peak value V1, the second peak value V2, the first argument θ1, and the second argument θ2.

[0104] Furthermore, this application needs to determine whether the calculated insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground have failed. Therefore, this application embodiment sets a first preset threshold and a second preset threshold to determine whether the insulation impedance of the live wire to ground is less than a critical value. When the insulation impedance of the live wire to ground is less than the first preset threshold, it is determined that the insulation impedance of the live wire to ground has failed. It also determines whether the insulation impedance of the neutral wire to ground is less than a critical value, and when the insulation impedance of the neutral wire to ground is less than the second preset threshold, it is determined that the insulation impedance of the neutral wire to ground has failed.

[0105] Furthermore, this application does not specifically limit the first and second preset thresholds mentioned above, and those skilled in the art can set them according to actual needs.

[0106] To enable those skilled in the art to further understand the AC insulation impedance detection method based on insulation detection circuit of this application, the following examples illustrate the simulation results of the AC unbalanced bridge method using this method.

[0107] Specifically, such as Figure 6 As shown, under the condition that the single-pole multi-throw switch S1 is closed with R1 and R2 respectively, the voltage across the third resistor R3 is measured. After adding phase angle detection, the phase difference between the AC voltage across the third resistor R3 and the AC input voltage can be detected. The specific method can be to calculate the sampling time difference between the peak value of the AC input sine wave and the peak voltage of the sine wave across the third resistor R3, or the sampling time difference between the two zero-crossing signals. No specific limitation is made here.

[0108] Furthermore, through circuit simulation, this embodiment of the application shows that after the single-pole multi-throw switch S1 is closed with the first resistor R1 and the second resistor R2 respectively, a phase difference can be observed between the voltage of the live wire L relative to ground and the voltage of the neutral wire N relative to ground. The following results are obtained:

[0109] In the initial state, such as Figure 6 As shown, the fourth resistor Rx = the fifth resistor Ry = 500kΩ, the first peak value Vpp1 = 1.1V, and the second peak value Vpp2 = 1.1V. Figure 7 This is a waveform diagram of the initial state of a specific embodiment of this application. Figure 7 Curve L in the figure represents the voltage of the live wire AC_L relative to ground, which can be obtained by multiplying the sampling resistor by the voltage divider ratio. Figure 7 Curve N in the figure represents the voltage of the neutral wire AC_N relative to ground. This voltage can be obtained by subtracting the voltage of the live wire AC_L relative to ground from the AC voltage of the live wire AC_L relative to the neutral wire AC_N, such as... Figure 7 As shown, in the initial state, the insulation resistance of the live wire AC_L and the neutral wire AC_N did not change significantly, and the two were almost equal, with a phase difference of about 180°.

[0110] In some cases, such as Figure 6 As shown, the insulation resistance of the live wire AC_L has decreased, the ground has shifted towards the live wire AC_L, the voltage of the live wire AC_L to ground has decreased, and the voltage of the neutral wire AC_N to ground has increased. Figure 8 As shown, Figure 8 This is a waveform diagram showing the reduced insulation impedance of the live wire to ground according to a specific embodiment of this application. It can be seen that the phase difference between the two has changed.

[0111] In other cases, such as Figure 6 As shown, the insulation resistance of the live wire AC_L further decreases, the ground shifts towards the live wire AC_L, the voltage of the live wire AC_L to ground decreases, and the voltage of the neutral wire AC_N to ground increases, as shown. Figure 9 As shown, Figure 9 This is a waveform diagram showing the further reduction of the live wire to ground insulation impedance according to a specific embodiment of this application. It can be seen that the phase difference between the two changes further.

[0112] It should be noted that the above-listed embodiments are merely illustrative and are not intended to limit the scope of this application. In actual implementation, the insulation detection circuit of this application embodiment may include not only the first resistor R1 and the second resistor R2 described above, but may also include more parameter resistors and capacitors (such as...). Figure 4 As shown in the figure, its purpose is to construct more equations and more points to fit the impedance curve.

[0113] For example, Figure 10This is a schematic diagram of the equivalent circuit of a specific embodiment of this application. Figure 10 In this equivalent circuit, the components include: resistors R1, R3, Rx, Ry, capacitors Cx and Cy. Furthermore, this embodiment will collect the peak voltage of resistor R3, the AC voltage across resistor R3, and the phase difference between the AC input voltage and the AC voltage. Therefore, this embodiment constructs the following equation (1):

[0114]

[0115] Among them, V ac_l ω is the AC input voltage, j is the impedance, and ω is the angular frequency.

[0116] Figure 11 This is a schematic diagram of the equivalent circuit of another specific embodiment of this application. Figure 11 In this equivalent circuit, there are: capacitors C1, Cx, Cy, resistors R3, Rx, and Ry. Furthermore, in this embodiment, the peak voltage of resistor R3, the AC voltage across resistor R3, and the phase difference between the AC input voltage are collected. Therefore, this embodiment constructs the following equation (2):

[0117]

[0118] Among them, V ac_l ω is the AC input voltage, j is the impedance, and ω is the angular frequency.

[0119] Therefore, this application improves the accuracy of AC insulation impedance detection by incorporating phase angle detection to identify the RC component in the insulation impedance and fit the impedance curve.

[0120] According to the AC insulation impedance detection method based on an insulation detection circuit proposed in this application, the insulation detection circuit, composed of first to M resistors, first to second capacitors, and a single-pole multi-throw switch, is used to collect the first to N peak voltages of the (M-2)th resistor and the first to N phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage. The insulation impedance of the live wire to ground and the neutral wire to ground are calculated based on the first to N peak voltages and the first to N phase differences. If the live wire to ground insulation impedance is less than a first preset threshold, the live wire to ground insulation impedance is determined to be faulty; similarly, if the neutral wire to ground insulation impedance is less than a second preset threshold, the neutral wire to ground insulation impedance is determined to be faulty. Therefore, this application can identify the resistive and capacitive components in the insulation impedance through phase detection, thus solving the problem in related technologies where resistive impedance and capacitive reactance components cannot be identified in AC insulation impedance detection, effectively improving the accuracy of detecting external impedance values.

[0121] Next, referring to the accompanying drawings, an AC insulation impedance detection device based on an insulation detection circuit according to an embodiment of this application is described.

[0122] Figure 12 This is a block diagram of an AC insulation impedance detection device based on an insulation detection circuit according to an embodiment of this application.

[0123] like Figure 12 As shown, the AC insulation impedance detection device 1000 based on the insulation detection circuit includes: a data acquisition module 100 and a judgment module 200.

[0124] Specifically, the acquisition module 100 is used to control the closing of the first to Nth moving terminals and the stationary terminals respectively, acquire the first to Nth peak voltages of the (M-2)th resistor, and the first to Nth phase differences between the first AC voltage and the AC input voltage across the (M-2)th resistor; the determination module 200 is used to calculate the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground based on the first to Nth peak voltages and the first to Nth phase differences, and determine that the insulation impedance of the live wire to ground is faulty when the insulation impedance of the live wire to ground is less than a first preset threshold, and determine that the insulation impedance of the neutral wire to ground is faulty when the insulation impedance of the neutral wire to ground is less than a second preset threshold.

[0125] Optionally, in some embodiments, the determination module 200 includes: a first calculation unit and a second calculation unit.

[0126] The first calculation unit is used to calculate the impedance value of the (M-2)th resistor, the impedance value of the (M-1)th resistor, the capacitive reactance value of the first capacitor, and the capacitive reactance value of the second capacitor based on the first to Nth peak voltages and the first to Nth phase differences. The second calculation unit is used to perform parallel impedance calculation on the impedance value of the (M-2)th resistor and the capacitive reactance value of the first capacitor to obtain the insulation impedance of the live wire to ground, and to perform parallel impedance calculation on the impedance value of the (M-1)th resistor and the capacitive reactance value of the second capacitor to obtain the insulation impedance of the neutral wire to ground.

[0127] Optionally, in some embodiments, after acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the acquisition module 100 further includes: a first judgment unit and a second judgment unit.

[0128] The first judgment unit is used to determine that the impedance of the (M-1)th resistor and the first capacitor decreases when the peak voltages from the first to the Nth are all less than the corresponding third preset threshold; the second judgment unit is used to determine that the impedance of the Mth resistor and the second capacitor decreases when the peak voltages from the first to the Nth are all greater than the corresponding fourth preset threshold.

[0129] Optionally, in some embodiments, after acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the acquisition module 100 further includes a third judgment unit.

[0130] The third judgment unit is used to determine that the current AC insulation impedance detection has failed when some of the peak voltages from the first to the Nth peak voltages are greater than the corresponding third preset threshold and the remaining peak voltages are less than the corresponding third preset threshold, or when some of the peak voltages from the first to the Nth peak voltages are greater than the corresponding fourth preset threshold and the remaining peak voltages are less than the corresponding fourth preset threshold.

[0131] Optionally, in some embodiments, the resistance values ​​of the first resistor to the (M-3)th resistor are different.

[0132] It should be noted that the foregoing explanation of the embodiment of the AC insulation impedance detection method based on the insulation detection circuit also applies to the AC insulation impedance detection device based on the insulation detection circuit in this embodiment, and will not be repeated here.

[0133] The AC insulation impedance detection device based on an insulation detection circuit proposed in this application utilizes an insulation detection circuit composed of first to M resistors, first to second capacitors, and a single-pole multi-throw switch. By controlling the closing of the first to N moving and stationary terminals of the single-pole multi-throw switch respectively, the device acquires the first to N peak voltages of the (M-2)th resistor and the first to N phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage. Based on the first to N peak voltages and the first to N phase differences, the device calculates the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground. If the insulation impedance of the live wire to ground is less than a first preset threshold, the live wire to ground insulation impedance is determined to be faulty; similarly, if the insulation impedance of the neutral wire to ground is less than a second preset threshold, the neutral wire to ground insulation impedance is determined to be faulty. Therefore, this application can identify the resistive and capacitive components in the insulation impedance through phase detection, thereby solving the problem in related technologies where resistive impedance and capacitive reactance components cannot be identified in AC insulation impedance detection, effectively improving the accuracy of detecting external impedance values.

[0134] This application also provides an on-board charger inverter, including an AC insulation impedance detection device based on an insulation detection circuit as described in the above embodiments.

[0135] The on-board charger inverter proposed in the embodiments of this application solves the problem in the related technology that the resistance impedance and capacitive reactance components cannot be identified in AC insulation impedance detection by the above-mentioned AC insulation impedance detection device based on the insulation detection circuit, and effectively improves the accuracy of detecting external impedance values.

[0136] This application also provides a vehicle including the on-board charger inverter as described above.

[0137] The vehicle proposed in the embodiments of this application solves the problem in the related technology that the resistance impedance and capacitive reactance components cannot be identified in AC insulation impedance detection, and effectively improves the accuracy of detecting external impedance values ​​by using the on-board charger inverter described above.

[0138] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0139] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0140] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0141] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or more of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (FPGAs), field-programmable gate arrays (FPGAs), etc.

[0142] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0143] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for detecting AC insulation impedance based on an insulation detection circuit, characterized in that, The insulation detection circuit includes first to M resistors, first to second capacitors, and a single-pole multi-throw switch. One end of the first to M-3 resistors is connected to the first to Nth moving terminals of the single-pole multi-throw switch, respectively. One end of the M-2 resistor is connected to the stationary terminal of the single-pole multi-throw switch. The other ends of the first to M-3 resistors and one end of the M-1 resistor are both connected to the live wire. The other end of the M-1 resistor is grounded. The other ends of the M-2 resistor and one end of the M resistor are both connected to the other end of the M-1 resistor. The other end of the M resistor is connected to the neutral wire. One end of the first capacitor is connected to one end of the M-1 resistor. The other end of the first capacitor is grounded. One end of the second capacitor is connected to the other end of the first capacitor. The other end of the second capacitor is connected to the other end of the M resistor. N and M are both integers, and M ≥ 5, N = M - 3. The method includes the following steps: The first to Nth moving terminals and the fixed terminals are controlled to close respectively, and the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage and the AC input voltage across the (M-2)th resistor are collected. The insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground are calculated based on the first to Nth peak voltages and the first to Nth phase differences. If the insulation impedance of the live wire to ground is less than a first preset threshold, the insulation impedance of the live wire to ground is determined to be faulty. If the insulation impedance of the neutral wire to ground is less than a second preset threshold, the insulation impedance of the neutral wire to ground is determined to be faulty.

2. The method according to claim 1, characterized in that, The calculation of the insulation resistance of the live wire to ground and the insulation resistance of the neutral wire to ground based on the first to Nth peak voltages and the first to Nth phase differences includes: The impedance values ​​of the (M-2)th resistor, the (M-1)th resistor, the capacitive reactance of the first capacitor, and the capacitive reactance of the second capacitor are calculated based on the first to Nth peak voltages and the first to Nth phase differences. The insulation impedance of the live wire to ground is obtained by performing parallel impedance calculation on the impedance value of the (M-2)th resistor and the capacitive reactance value of the first capacitor, and the insulation impedance of the neutral wire to ground is obtained by performing parallel impedance calculation on the impedance value of the (M-1)th resistor and the capacitive reactance value of the second capacitor.

3. The method according to claim 2, characterized in that, After acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the method further includes: If the first to Nth peak voltages are all less than the corresponding third preset threshold, then it is determined that the impedance of the (M-1)th resistor and the first capacitor has decreased. If the first to Nth peak voltages are all greater than the corresponding fourth preset threshold, then it is determined that the impedance of the Mth resistor and the second capacitor has decreased.

4. The method according to claim 2, characterized in that, After acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the method further includes: If a portion of the peak voltages from the first to the Nth peak voltages is greater than the corresponding third preset threshold, and the remaining portion is less than the corresponding third preset threshold, or if a portion of the peak voltages from the first to the Nth peak voltages is greater than the corresponding fourth preset threshold, and the remaining portion is less than the corresponding fourth preset threshold, then the current AC insulation impedance detection is determined to be faulty.

5. The method according to any one of claims 1-4, characterized in that, The resistance values ​​of the first resistor and the (M-3)th resistor are different.

6. An AC insulation impedance detection device based on an insulation detection circuit, characterized in that, The insulation detection circuit includes first to M resistors, first to second capacitors, and a single-pole multi-throw switch. One end of the first to M-3 resistors is connected to the first to Nth moving terminals of the single-pole multi-throw switch, respectively. One end of the M-2 resistor is connected to the stationary terminal of the single-pole multi-throw switch. The other ends of the first to M-3 resistors and one end of the M-1 resistor are both connected to the live wire. The other end of the M-1 resistor is grounded. The other ends of the M-2 resistor and one end of the M resistor are both connected to the other end of the M-1 resistor. The other end of the M resistor is connected to the neutral wire. One end of the first capacitor is connected to one end of the M-1 resistor. The other end of the first capacitor is grounded. One end of the second capacitor is connected to the other end of the first capacitor. The other end of the second capacitor is connected to the other end of the M resistor. N and M are both integers, and M ≥ 5, N = M - 3. The device includes: The acquisition module is used to control the closing of the first to Nth moving terminals and the stationary terminals respectively, acquire the first to Nth peak voltages of the (M-2)th resistor, and the first to Nth phase differences between the first AC voltage and the AC input voltage across the (M-2)th resistor; The determination module is used to calculate the insulation impedance of the live wire to ground and the insulation impedance of the neutral wire to ground based on the first to Nth peak voltages and the first to Nth phase differences, and to determine that the insulation impedance of the live wire to ground is faulty when the insulation impedance of the live wire to ground is less than a first preset threshold, and to determine that the insulation impedance of the neutral wire to ground is faulty when the insulation impedance of the neutral wire to ground is less than a second preset threshold.

7. The apparatus according to claim 6, characterized in that, The determination module includes: The first calculation unit is used to calculate the impedance value of the (M-2)th resistor, the impedance value of the (M-1)th resistor, the capacitive reactance value of the first capacitor, and the capacitive reactance value of the second capacitor based on the first to Nth peak voltages and the first to Nth phase differences. The second calculation unit is used to perform parallel impedance calculation on the impedance value of the (M-2)th resistor and the capacitive reactance value of the first capacitor to obtain the insulation impedance of the live wire to ground, and to perform parallel impedance calculation on the impedance value of the (M-1)th resistor and the capacitive reactance value of the second capacitor to obtain the insulation impedance of the neutral wire to ground.

8. The apparatus according to claim 7, characterized in that, After acquiring the first to Nth peak voltages of the (M-2)th resistor and the first to Nth phase differences between the first AC voltage across the (M-2)th resistor and the AC input voltage, the acquisition module further includes: The first judgment unit is used to determine that the impedance of the (M-1)th resistor and the first capacitor decreases when the peak voltages from the first to the Nth are all less than the corresponding third preset threshold. The second judgment unit is used to determine that the impedance of the Mth resistor and the second capacitor decreases when the first to Nth peak voltages are all greater than the corresponding fourth preset threshold.

9. An on-board charger inverter, characterized in that, Includes an AC insulation impedance detection device based on an insulation detection circuit as described in any one of claims 6-8.

10. A vehicle, characterized in that, include: The on-board charger inverter as described in claim 9.

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