An alternating current insulation monitoring method and apparatus

Abstract

The application provides an alternating current insulation monitoring method and device, and relates to the technical field of electricity. The method comprises the following steps: controlling a controlled switch to be turned off, collecting an output voltage of an inverter as a first voltage; controlling the controlled switch to be turned on, collecting a voltage between an output end of the inverter and the ground; extracting a characteristic quantity of the first voltage and a characteristic quantity of the voltage between the output end and the ground; and determining an insulation impedance between the output end of the inverter and the ground according to the extracted characteristic quantity of the first voltage and the extracted characteristic quantity of the voltage between the output end and the ground. The application realizes alternating current insulation monitoring based on an alternating current insulation monitoring circuit adopting a single controlled switch, realizes monitoring of the insulation impedance between the output end of the inverter and the ground, simplifies the circuit structure of the alternating current insulation monitoring circuit and the process of an alternating current insulation monitoring method based on the alternating current insulation monitoring circuit while ensuring the accuracy and reliability of the monitoring result, and can effectively reduce the cost of alternating current insulation monitoring.

Description

Technical Field

[0001] This invention relates to the field of electrical technology, and more specifically, to an AC insulation monitoring method and device. Background Technology

[0002] An inverter is a converter that transforms direct current (DC) power into alternating current (AC) power of fixed frequency and voltage or frequency and voltage regulation. It is widely used in power conversion. Because the insulation resistance of the inverter's output terminals to ground is crucial to user safety—specifically, the insulation resistance of the inverter's live and neutral output wires to ground must exceed a certain threshold to ensure personal safety—monitoring the inverter's insulation resistance to ground is essential.

[0003] Currently, there are two common methods for monitoring the ground insulation impedance of inverters: DC monitoring and AC monitoring. DC monitoring generally requires an external DC bias, while AC monitoring generally requires multiple external switching circuits. Both of these methods result in complex detection circuits and methods, and relatively high monitoring costs. Summary of the Invention

[0004] The problem this invention addresses is how to simplify the detection circuit and detection method while ensuring the accuracy of AC insulation monitoring results.

[0005] To address the above problems, the present invention provides an AC insulation monitoring method based on an AC insulation monitoring circuit, which includes a controlled switch and a third resistor. One end of the controlled switch is used to connect to an output terminal of an inverter, and the other end of the controlled switch is grounded through the third resistor.

[0006] The AC insulation monitoring method includes:

[0007] The controlled switch is disconnected, and the output voltage of the inverter is collected as the first voltage.

[0008] Control the closed switch to collect the voltage between the output terminal and ground of the inverter;

[0009] Extract the characteristic quantities of the first voltage, and extract the characteristic quantities of the output terminal voltage to ground;

[0010] Based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output terminal to ground voltage, the output terminal to ground insulation impedance of the inverter is determined.

[0011] Optionally, the inverter has a first output terminal and a second output terminal, and one end of the controlled switch is used to connect to the first output terminal or the second output terminal; controlling the controlled switch to close and acquiring the voltage of the inverter's output terminal to ground includes:

[0012] Control the closed switch to collect the voltage to ground of the first output terminal and the voltage to ground of the second output terminal of the inverter.

[0013] The extraction of the characteristic quantities of the first voltage and the extraction of the characteristic quantities of the output terminal voltage to ground include:

[0014] Extract the voltage phasor of the first voltage, and extract the amplitudes of the voltage at the first output terminal to ground and the voltage at the second output terminal to ground, respectively;

[0015] The step of determining the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage includes:

[0016] Based on the preset voltage phasor of the first voltage, the amplitude of the voltage to ground at the first output terminal of the inverter, the amplitude of the voltage to ground at the second output terminal of the inverter, the relationship between the insulation impedance to ground at the first output terminal of the inverter and the insulation impedance to ground at the second output terminal of the inverter, and based on the extracted voltage phasor of the first voltage, the amplitude of the voltage to ground at the first output terminal and the amplitude of the voltage to ground at the second output terminal, the insulation impedance to ground at the first output terminal and the insulation impedance to ground at the second output terminal of the inverter are determined.

[0017] Optionally, the step of determining the insulation resistance of the first output terminal to ground and the insulation resistance of the second output terminal to ground based on the preset relationship between the voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground of the inverter, the amplitude of the voltage at the second output terminal to ground of the inverter, the insulation resistance of the first output terminal to ground of the inverter, and the insulation resistance of the second output terminal to ground of the inverter, and based on the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground, includes:

[0018] Substitute the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground into the first preset formula and the second preset formula.

[0019] The first preset formula and the second preset formula are combined to solve the problem and calculate the first output terminal insulation resistance to ground and the second output terminal insulation resistance to ground of the inverter.

[0020] The first preset formula is:

[0021]

[0022] In the above formula, Let A represent the voltage phasor of the first voltage, and let Z represent the magnitude of the voltage at the first output terminal relative to ground. L Z represents the insulation resistance of the first output terminal to ground. N R3 represents the insulation resistance of the second output terminal to ground, and R3 represents the resistance value of the third resistor.

[0023] The second preset formula is:

[0024]

[0025] In the above formula, B represents the amplitude of the voltage to ground at the second output terminal.

[0026] Optionally, controlling the closed switch and collecting the inverter's output voltage to ground includes:

[0027] Control the closed switch to collect the voltage to ground of the first output terminal or the voltage to ground of the second output terminal of the inverter.

[0028] The extraction of the characteristic quantities of the first voltage and the extraction of the characteristic quantities of the output terminal voltage to ground include:

[0029] Extract the voltage phasor of the first voltage, and extract the amplitude and phase angle of the voltage at the first output terminal to ground or the voltage at the second output terminal to ground;

[0030] The step of determining the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage includes:

[0031] Based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal of the inverter to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage and the amplitude and phase angle of the voltage at the first output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground are determined; or, based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the second output terminal of the inverter to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground are determined.

[0032] Optionally, controlling the closed switch and collecting the inverter's output voltage to ground includes:

[0033] Control the closed switch to collect the voltage to ground of the first output terminal and the voltage to ground of the second output terminal of the inverter.

[0034] The extraction of the characteristic quantities of the first voltage and the extraction of the characteristic quantities of the output terminal voltage to ground include:

[0035] Extract the voltage phasor of the first voltage, and extract the amplitude and phase angle of the voltage at the first output terminal to ground, and extract the amplitude and phase angle of the voltage at the second output terminal to ground;

[0036] The step of determining the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage includes:

[0037] Based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal of the inverter to ground and the amplitude and phase angle of the voltage at the second output terminal to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal to ground and the insulation impedance at the second output terminal to ground of the inverter are determined.

[0038] Optionally, the step of determining the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground based on the preset relationship between the voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground and the voltage at the second output terminal to ground of the inverter, and the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground of the inverter, and based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground and the amplitude and phase angle of the voltage at the second output terminal to ground, includes:

[0039] Using a lookup table method, the first output terminal to ground insulation impedance and the second output terminal to ground insulation impedance of the inverter are determined based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the first output terminal to ground voltage, and the amplitude and phase angle of the second output terminal to ground voltage. The preset database corresponding to the lookup table method is constructed based on the preset relationship between the voltage phasor of the first voltage, the amplitude and phase angle of the first output terminal to ground voltage and the second output terminal to ground voltage, and the first output terminal to ground insulation impedance and the second output terminal to ground insulation impedance of the inverter.

[0040] Optionally, the method of using a lookup table to determine the insulation resistance of the first output terminal to ground and the insulation resistance of the second output terminal to ground of the inverter based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground, and the amplitude and phase angle of the voltage at the second output terminal to ground includes:

[0041] Based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal, and the amplitude and phase angle of the voltage to ground at the second output terminal, a query is performed on the preset database to obtain a first ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the first output terminal, a second ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the first output terminal, a third ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the second output terminal, and a fourth ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the second output terminal.

[0042] The first output terminal insulation impedance to ground of the inverter is calculated based on the first and second ground insulation impedance reference values; and the second output terminal insulation impedance to ground of the inverter is calculated based on the third and fourth ground insulation impedance reference values.

[0043] Optionally, the step of calculating the first output terminal to ground insulation impedance of the inverter based on the first to ground insulation impedance reference value and the second to ground insulation impedance reference value; and calculating the second output terminal to ground insulation impedance of the inverter based on the third to ground insulation impedance reference value and the fourth to ground insulation impedance reference value includes:

[0044] Calculate the difference between the first reference value of insulation resistance to ground and the second reference value of insulation resistance to ground, and use it as the first difference;

[0045] Determine whether the absolute value of the first difference is less than the second preset threshold;

[0046] In response to determining that the absolute value of the first difference is greater than or equal to the second preset threshold, the AC insulation monitoring method is re-executed;

[0047] In response to determining that the absolute value of the first difference is less than the second preset threshold, the difference between the third ground insulation impedance reference value and the fourth ground insulation impedance reference value is calculated as the second difference value, and it is determined whether the absolute value of the second difference value is less than the third preset threshold value.

[0048] In response to determining that the absolute value of the second difference is greater than or equal to the third preset threshold, the AC insulation monitoring method is re-executed;

[0049] In response to the determination that the absolute value of the second difference is less than the third preset threshold, the first output terminal to ground insulation impedance of the inverter is calculated according to the first to ground insulation impedance reference value, the second to ground insulation impedance reference value and the third preset formula, and the second output terminal to ground insulation impedance is calculated according to the third output terminal to ground insulation impedance reference value, the fourth output terminal to ground insulation impedance reference value and the fourth preset formula.

[0050] Optionally, the third preset formula is:

[0051] Z L = a1*Z1 + b1*Z2,

[0052] Among them, Z L Z1 is the first output terminal ground insulation impedance of the inverter; a1 is the first preset weighting coefficient; b1 is the second preset weighting coefficient; Z1 is the first ground insulation impedance reference value; Z2 is the second ground insulation impedance reference value.

[0053] The fourth preset formula is:

[0054] Z N = a² * Z³ + b² * Z⁴

[0055] Among them, Z N Z1 is the insulation resistance to ground of the second output terminal of the inverter; Z2 is the third preset weighting coefficient; Z3 is the reference value of the third insulation resistance to ground; and Z4 is the reference value of the fourth insulation resistance to ground.

[0056] Optionally, the AC insulation monitoring method further includes a self-test step, which includes:

[0057] The controlled switch is disconnected, and the amplitude of the voltage to ground at the first output terminal and the amplitude of the voltage to ground at the second output terminal of the inverter are obtained.

[0058] Calculate the ratio of the amplitude of the voltage to ground at the first output terminal to the amplitude of the voltage to ground at the second output terminal;

[0059] Determine whether the ratio is greater than a first preset threshold, and determine whether the ratio is less than the reciprocal of the first preset threshold; wherein, the first preset threshold is greater than the reciprocal of the first preset threshold;

[0060] An insulation fault alarm is triggered in response to the determination that the ratio is greater than a first preset threshold or that the ratio is less than the reciprocal of the first preset threshold.

[0061] To address the above problems, the present invention also provides an AC insulation monitoring device, including an AC insulation monitoring circuit, a memory, and a processor;

[0062] The AC insulation monitoring circuit includes a controlled switch and a third resistor. One end of the controlled switch is used to connect to one output terminal of the inverter, and the other end of the controlled switch is grounded through the third resistor.

[0063] The memory is used to store computer programs;

[0064] The processor is used to implement the AC insulation monitoring method described above when executing the computer program.

[0065] Compared with the prior art, the present invention has the following beneficial effects: Compared with the existing technology, which uses external bias or multiple switching circuits for switching monitoring circuits and the corresponding monitoring methods, the AC insulation monitoring method in this embodiment is based on an AC insulation monitoring circuit using a third resistor, a controller, a grounded first sampling circuit and a second sampling circuit, and a single controlled switch to monitor AC insulation. This enables the monitoring of the ground insulation impedance of the first and second output terminals of the inverter. While ensuring the accuracy and reliability of the monitoring results, it simplifies the circuit structure of the AC insulation monitoring circuit and the process of the AC insulation monitoring method based on the AC insulation monitoring circuit, and can effectively reduce the cost of AC insulation monitoring. Attached Figure Description

[0066] Figure 1 This is a flowchart of the AC insulation monitoring method in an embodiment of the present invention;

[0067] Figure 2 This is a schematic diagram of the connection between the inverter and the AC insulation monitoring circuit in an embodiment of the present invention;

[0068] Figure 3 This is a schematic diagram of the connection between the inverter and the AC insulation monitoring circuit in another embodiment of the present invention;

[0069] Figure 4 This is a schematic diagram of the connection between the inverter and the AC insulation monitoring circuit in another embodiment of the present invention;

[0070] Figure 5 This is a sub-flowchart of step 400 in an embodiment of the present invention. Detailed Implementation

[0071] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0072] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0073] Combination Figure 1 , Figure 2 As shown, this embodiment of the invention provides an AC insulation monitoring method based on an AC insulation monitoring circuit. The AC insulation monitoring circuit includes a controlled switch and a third resistor. One end of the controlled switch is used to connect to one output terminal of an inverter, and the other end of the controlled switch is grounded through the third resistor.

[0074] AC insulation monitoring methods include:

[0075] Step 100: Control the controlled switch to open and collect the inverter's output voltage as the first voltage;

[0076] Step 200: Control the closed switch and collect the voltage between the inverter's output terminal and ground.

[0077] Step 300: Extract the characteristic quantities of the first voltage and extract the characteristic quantities of the output terminal voltage to ground;

[0078] Step 400: Determine the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage.

[0079] In this embodiment, the AC insulation monitoring circuit is used to monitor (or detect) the ground insulation impedance of the first and second output terminals of the inverter, such as real-time monitoring of the ground insulation impedance of the first and second output terminals of the inverter during operation. Specifically, when the inverter is running, its two output terminals, the first output terminal (denoted as U...)... L ) and the second output terminal (denoted as U) N There exists an alternating current Uac (i.e., the AC voltage output by the inverter), U L The insulation resistance to ground (i.e., the insulation resistance of the first output terminal to ground) is denoted as Z. L U N The insulation resistance to ground (i.e., the insulation resistance of the second output terminal to ground) is denoted as Z. N Z L Z N It can be provided by resistors, capacitors, etc., and the AC insulation monitoring circuit is used to monitor Z. L With Z N The size of Z L With Z NIf at least one of the values ​​is less than the corresponding safety threshold, it can be determined that there is an insulation fault in the inverter. At this time, the controller (MCU) can perform corresponding operations, such as controlling the inverter to stop running or issuing an insulation fault alarm, to ensure the safety of the user.

[0080] The AC insulation monitoring circuit includes a controlled switch (denoted as S1, which can be a relay, etc.), a third resistor (denoted as R3), a controller, and a grounded sampling circuit. One end of the controlled switch is connected to one output terminal of the inverter (either the first output terminal or the second output terminal), and the other end of the controlled switch is grounded through the third resistor. At least one of the first and second output terminals is connected to the controller through the sampling circuit. Specifically, in the AC insulation monitoring circuit, the first output terminal U... L Second output terminal U N One of them is grounded through a series controlled switch S1 and a third resistor R3. The opening and closing of the controlled switch S1 controls the connection and disconnection of the third resistor R3 in the AC insulation monitoring circuit. When S1 is closed, R3 is connected in parallel with Z. L or Z N Above, resulting in the corresponding U L or U N The voltage at the output terminal will change accordingly, thus facilitating the monitoring of the inverter's insulation impedance to ground. First output terminal U L Second output terminal U N At least one of them is connected to the signal input terminal of the sampling circuit, so that the sampling circuit can access the first output terminal U. L and / or the second output terminal U N The voltage (or voltage characteristics) at the sampling point is sampled, such as the corresponding amplitude and phase angle. The signal output terminal of the sampling circuit is connected to the signal input terminal of the controller, so that the sampling circuit can send the corresponding sampling processing results to the controller. The controller then performs corresponding calculations based on the sampling processing results to ultimately obtain the AC insulation monitoring circuit's monitoring of the inverter's insulation impedance to ground. The sampling circuit is grounded through a corresponding port to suppress common-mode interference, ensure the safety of sampling, and guarantee the accuracy of the sampling results. It is worth noting that the third resistor R3 in the AC insulation monitoring circuit can be a single resistor or composed of multiple resistors connected in series and / or in parallel.

[0081] This method for AC insulation monitoring is based on the aforementioned AC insulation monitoring circuit, specifically, AC insulation monitoring is achieved through the AC insulation monitoring circuit. In step 100, during inverter operation, the controlled switch S1 is opened, and relevant voltage information (including voltage waveform, etc.) of the inverter's output voltage Uac is collected (acquired) using appropriate monitoring equipment or through the controller. This information is used as the first voltage for subsequent calculation of the inverter output terminal's insulation impedance to ground. Then, in step 200, the controlled switch S1 is closed, enabling the third resistor R3 to be connected in the AC insulation monitoring circuit. The connection of the third resistor R3 causes the corresponding first output terminal Uac to... L Or the second output terminal U N The voltage at the location will change accordingly. At this time, the relevant voltage information of the inverter output terminal to ground is collected by the sampling circuit, that is, the relevant voltage information of the voltage to ground at the first output terminal of the inverter (denoted as the first output terminal to ground voltage) and / or the voltage to ground at the second output terminal (denoted as the second output terminal to ground voltage). Then, through step 300, the characteristic quantities of the first voltage and the output terminal to ground voltage are extracted. For example, the sampling circuit processes the relevant voltage information of the first voltage and the output terminal to ground voltage and inputs it into the controller. The controller performs corresponding analysis and processing on the relevant voltage information of the first voltage and the output terminal to ground voltage, such as analyzing and processing the voltage waveform in the corresponding voltage information to obtain voltage characteristic quantities (or voltage characteristic parameters) such as voltage phasors, amplitude, and phase angle. Finally, through step 400 (through the controller), the insulation impedance of the inverter output terminal to ground can be solved based on the characteristic quantities of the first voltage and the output terminal to ground voltage extracted in step 300, that is, the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground can be solved, realizing the real-time monitoring of the inverter's insulation impedance to ground.

[0082] For example, regarding the monitoring of the inverter's output-to-ground insulation impedance (the insulation impedance to ground of the first output terminal and the second output terminal), when the inverter enters the inverter state (operation), in step 100, when S1 is disconnected, the inverter's output voltage (first voltage) Uac is first acquired, so as to extract the corresponding voltage characteristic quantity (such as voltage phasor) based on the first voltage. Output frequency f, output angular velocity ω = 2πf, etc.; through step 200, S1 is closed again, resistor R3 is connected, and the voltage of the inverter's output terminal to ground (i.e., the voltage of the first output terminal U) is obtained through the sampling circuit. L The voltage to ground at the second output terminal U N (Voltage to ground at the inverter output terminal); through step 300, the controller processes the first voltage and the inverter output terminal voltage to ground accordingly, and extracts the corresponding characteristic quantities, such as the voltage phasor of the first voltage Uac. The amplitude A and phase angle α of the voltage to ground at the first output terminal of the inverter, and the amplitude B and phase angle β of the voltage to ground at the second output terminal of the inverter (where the corresponding controller calculation can be simplified by configuring a hardware zero-crossing comparator circuit); through step 400, (through the controller) Z is calculated based on A, α, B, and β. L With Z N The solution is as follows (taking the first output terminal U as an example). L (Taking grounding via a series-connected controlled switch S1 and a third resistor R3 as an example):

[0083]

[0084]

[0085]

[0086]

[0087] Where || represents the phasor magnitude operation, and arg() represents the phase angle operation. In some embodiments, obtaining at least two of A, α, B, and β is sufficient to perform Z-axis calculation. L With Z N Solve for it.

[0088] In contrast to existing monitoring circuit structures and methods that involve external biasing or multiple switching circuits, the AC insulation monitoring method in this embodiment utilizes a third resistor, a controller, a grounded first and second sampling circuit, and a single controlled switch to monitor AC insulation resistance to ground at the inverter's first and second output terminals. This method simplifies the circuit structure of the AC insulation monitoring circuit and the process of the AC insulation monitoring method based on it, while ensuring the accuracy and reliability of the monitoring results. This effectively reduces the cost of AC insulation monitoring.

[0089] Optionally, the inverter has a first output terminal and a second output terminal, and one end of the controlled switch is used to connect to either the first output terminal or the second output terminal; step 200 includes:

[0090] Control the closed switch and collect the voltage to ground of the first output terminal and the voltage to ground of the second output terminal of the inverter.

[0091] Step 300 includes:

[0092] Extract the voltage phasor of the first voltage, and extract the amplitudes of the voltage between the first output terminal and ground and the voltage between the second output terminal and ground, respectively;

[0093] Then step 400 includes:

[0094] Based on the relationship between the preset voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal of the inverter to ground, the amplitude of the voltage at the second output terminal of the inverter to ground, the insulation impedance at the first output terminal of the inverter to ground, and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal to ground and the insulation impedance at the second output terminal to ground of the inverter are determined.

[0095] Specifically, since the inverter has two output terminals, a first output terminal and a second output terminal, the voltage of the inverter's output terminal to ground in step 200 is the same as the voltage of the first output terminal to ground and the voltage of the second output terminal to ground; the characteristic quantity of the voltage of the output terminal to ground in step 300 is the same as the characteristic quantity of the voltage of the first output terminal and the second output terminal to ground; the insulation impedance of the inverter's output terminal to ground in step 400 is the same as the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground.

[0096] Optionally, the inverter's output voltage (first voltage) Uac and its corresponding voltage phasor It can be obtained by sampling and extracting by the inverter device itself, or by calculating by combining the ground voltage of the first output terminal and the second output terminal; when the controlled switch is open, the ground voltage of the first output terminal and the second output terminal can also be obtained by sampling circuit.

[0097] Optionally, based on the relationship between the preset voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground of the inverter, the amplitude of the voltage at the second output terminal to ground of the inverter, the insulation impedance at the first output terminal to ground of the inverter, and the insulation impedance at the second output terminal to ground of the inverter, and based on the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal to ground of the inverter is determined, including:

[0098] Substitute the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground into the first preset formula and the second preset formula.

[0099] The first and second preset formulas are combined to solve the problem and obtain the first output terminal insulation resistance to ground and the second output terminal insulation resistance to ground of the inverter.

[0100] The first preset formula is:

[0101]

[0102] In the above formula, The voltage phasor represents the first voltage, A represents the magnitude of the voltage at the first output terminal to ground, and Z represents the voltage phasor of the first voltage. L Z represents the insulation resistance of the first output terminal to ground. N R3 represents the insulation resistance of the second output terminal to ground, and R3 represents the resistance value of the third resistor.

[0103] The second preset formula is:

[0104]

[0105] In the above formula, B represents the magnitude of the voltage at the second output terminal to ground.

[0106] In this embodiment, the AC insulation monitoring method calculates the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground of the inverter using a first preset formula and a second preset formula. The first preset formula and the second preset formula are the preset voltage phasor of the first voltage, the amplitude of the voltage of the first output terminal to ground of the inverter, the amplitude of the voltage of the second output terminal to ground of the inverter, and the relationship between the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground of the inverter.

[0107] Specifically, the voltage phasor of the first voltage is extracted through step 300. After extracting the amplitude A of the voltage between the first output terminal and ground and the amplitude A of the voltage between the second output terminal and ground respectively; in step 400, the voltage phasor of the extracted first voltage is... Substituting the amplitude A of the voltage to ground at the first output terminal, the amplitude B of the voltage to ground at the second output terminal, and the resistance value of the third resistor (denoted as R3) into the first preset formula... Second preset formula By combining the first and second preset formulas and solving the problem, the insulation resistance Z of the first output terminal of the inverter to ground can be obtained. L The insulation resistance Z of the second output terminal to ground N .

[0108] Optionally, step 200 includes:

[0109] Control the closed switch and collect the voltage to ground of the first output terminal or the voltage to ground of the second output terminal of the inverter.

[0110] Step 300 includes:

[0111] Extract the voltage phasor of the first voltage, and extract the amplitude and phase angle of the voltage at the first output terminal to ground or the voltage at the second output terminal to ground;

[0112] Then step 400 includes:

[0113] Based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal of the inverter to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage and the amplitude and phase angle of the voltage at the first output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal to ground are determined; or, based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the second output terminal of the inverter to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground are determined.

[0114] Unlike the above method of calculating the inverter's first and second output terminal-to-ground insulation impedances based on the amplitudes of the first and second output terminal-to-ground voltages, this embodiment calculates the inverter's first and second output terminal-to-ground insulation impedances based on the amplitude and phase angle of either the first or second output terminal-to-ground voltage, i.e., according to the first preset formula. And the fifth preset formula Or according to the second preset formula And the sixth preset formula Solve for the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground of the inverter. The first and fifth preset formulas represent the preset relationships between the voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground of the inverter, and the insulation impedance of the first output terminal to ground of the inverter and the insulation impedance of the second output terminal to ground. The second and sixth preset formulas represent the preset relationships between the voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the second output terminal to ground of the inverter, and the insulation impedance of the first output terminal to ground of the inverter and the insulation impedance of the second output terminal to ground of the inverter.

[0115] Specifically, the voltage phasor of the first voltage is extracted through step 300. And after extracting the amplitude A and phase angle α of the voltage at the first output terminal to ground, or extracting the amplitude B and phase angle β of the voltage at the second output terminal to ground. In step 400, the voltage phasor of the extracted first voltage is... Substituting the amplitude A and phase angle α of the voltage to ground at the first output terminal, and the resistance value of the third resistor (denoted as R3), into the first preset formula... And the fifth preset formula By combining the first and fifth preset formulas and solving them, the insulation resistance Z of the inverter's first output terminal to ground can be obtained. LThe insulation resistance Z of the second output terminal to ground N Alternatively, the voltage phasor of the extracted first voltage. Substituting the amplitude B and phase angle β of the voltage to ground at the second output terminal, and the resistance value of the third resistor (denoted as R3), into the second preset formula... And the sixth preset formula By combining the second and sixth preset formulas and solving them, the insulation resistance Z of the first output terminal of the inverter to ground can be obtained. L The insulation resistance Z of the second output terminal to ground N .

[0116] Optionally, step 200 includes:

[0117] Control the closed switch and collect the voltage to ground of the first output terminal and the voltage to ground of the second output terminal of the inverter.

[0118] Step 300 includes:

[0119] Extract the voltage phasor of the first voltage, and extract the amplitude and phase angle of the voltage at the first output terminal to ground, and extract the amplitude and phase angle of the voltage at the second output terminal to ground;

[0120] Step 400 includes:

[0121] Based on the relationship between the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal of the inverter to ground, the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground, and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground, and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal to ground and the insulation impedance at the second output terminal to ground of the inverter are determined.

[0122] In this embodiment, after obtaining the amplitude A and phase angle α of the voltage to ground at the first output terminal, and the amplitude B and phase angle β of the voltage to ground at the second output terminal, the insulation impedance to ground at the first output terminal and the insulation impedance to ground at the second output terminal of the inverter can be solved according to any two of the corresponding preset relationships (or preset formulas). Alternatively, the insulation impedance to ground at the first output terminal and the insulation impedance to ground at the second output terminal can be determined using a lookup table method in a preset database.

[0123] Optionally, based on the relationship between the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground and the voltage at the second output terminal to ground of the inverter, the insulation impedance at the first output terminal to ground and the insulation impedance at the second output terminal to ground of the inverter, and based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal to ground and the insulation impedance at the second output terminal to ground are determined, including:

[0124] Using a lookup table method, the first output terminal to ground insulation impedance and the second output terminal to ground insulation impedance of the inverter are determined based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground, and the amplitude and phase angle of the voltage at the second output terminal to ground. The preset database corresponding to the lookup table method is constructed based on the preset relationship between the voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground and the voltage at the second output terminal to ground, and the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground of the inverter.

[0125] In this embodiment, the corresponding preset relationship is the preset database corresponding to the lookup table method. The preset database is constructed based on the preset relationship between the voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal of the inverter and the amplitude and phase angle of the voltage to ground at the second output terminal of the inverter, and the insulation impedance to ground at the first output terminal of the inverter and the insulation impedance to ground at the second output terminal of the inverter. After obtaining the voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal and the amplitude and phase angle of the voltage to ground at the second output terminal in step 300, step 400 can determine the corresponding insulation impedance to ground at the first output terminal and the insulation impedance to ground at the second output terminal of the inverter from the preset database. For example, after obtaining the corresponding amplitude and / or phase angle, the insulation impedance to ground corresponding to the corresponding amplitude and / or phase angle can be found through the corresponding correspondence table (or correspondence diagram) in the preset database. For example, the corresponding amplitude and / or phase angle can be input into the preset database, and the corresponding retrieval method can be used to search for the insulation impedance to ground corresponding to the corresponding amplitude and / or phase angle in the database.

[0126] Optionally, this method also includes:

[0127] Construct a pre-defined database that includes a table showing the correspondence between amplitude and insulation impedance to ground and / or a table showing the correspondence between phase angle and insulation impedance to ground.

[0128] Specifically, a table (or diagram) showing the correspondence between the amplitude (or phase angle) and impedance of the corresponding inverter in a steady state is obtained through prior experiments. A database containing numerous such tables is then constructed to facilitate subsequent determination of the corresponding ground insulation impedance using a lookup table method. This pre-construction of the database significantly reduces computational resources used for ground insulation impedance monitoring, improving processing efficiency. In some embodiments, considering that obtaining the actual phase angle is more difficult than obtaining the amplitude, using the amplitude correspondence is more reasonable; alternatively, utilizing both can effectively improve the corresponding monitoring accuracy.

[0129] Optionally, combined Figure 1 , Figure 5 As shown, using a lookup table method, based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground, and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground of the inverter are determined, including:

[0130] Step 410: Based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal, and the amplitude and phase angle of the voltage to ground at the second output terminal, query the preset database to obtain the first ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the first output terminal, the second ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the first output terminal, the third ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the second output terminal, and the fourth ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the second output terminal.

[0131] Step 420: Calculate the first output terminal insulation impedance to ground of the inverter based on the first and second ground insulation impedance reference values; and calculate the second output terminal insulation impedance to ground of the inverter based on the third and fourth ground insulation impedance reference values.

[0132] Considering that there may be some errors in determining the ground insulation impedance by looking up a table based solely on the corresponding amplitude and phase angle, this embodiment uses the reference values ​​of the ground insulation impedance corresponding to the amplitude and phase angle to determine the ground insulation impedance of the first output terminal and the second output terminal of the inverter, so as to effectively improve the corresponding monitoring accuracy. Specifically, based on the voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal, and the amplitude and phase angle of the voltage to ground at the second output terminal extracted in step 300, a lookup table method is used to query a preset database to obtain the first ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the first output terminal, the second ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the first output terminal, the third ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the second output terminal, and the fourth ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the second output terminal. Subsequently, the first output terminal ground insulation impedance of the inverter can be calculated according to the corresponding preset formula and the first and second ground insulation impedance reference values; and the second output terminal ground insulation impedance of the inverter can be calculated according to the corresponding preset formula and the third and fourth ground insulation impedance reference values. For example, by setting corresponding weighting coefficients, the weighted average of the first and second ground insulation impedance reference values ​​can be used as the first ground insulation impedance, and the weighted average of the third and fourth ground insulation impedance reference values ​​can be used as the second ground insulation impedance.

[0133] Optionally, step 420 includes:

[0134] Calculate the difference between the first ground insulation impedance reference value and the second ground insulation impedance reference value, and use it as the first difference value;

[0135] Determine whether the absolute value of the first difference is less than the second preset threshold;

[0136] In response to the determination that the absolute value of the first difference is greater than or equal to the second preset threshold, the AC insulation monitoring method is re-executed;

[0137] In response to the determination that the absolute value of the first difference is less than the second preset threshold, the difference between the third ground insulation impedance reference value and the fourth ground insulation impedance reference value is calculated as the second difference value, and it is determined whether the absolute value of the second difference value is less than the third preset threshold value.

[0138] In response to the determination that the absolute value of the second difference is greater than or equal to the third preset threshold, the AC insulation monitoring method is re-executed;

[0139] In response to the determination that the absolute value of the second difference is less than the third preset threshold, the first output terminal to ground insulation impedance of the inverter is calculated based on the first ground insulation impedance reference value, the second ground insulation impedance reference value and the third preset formula, and the second output terminal to ground insulation impedance is calculated based on the third output terminal to ground insulation impedance reference value, the fourth output terminal to ground insulation impedance reference value and the fourth preset formula.

[0140] In this embodiment, when determining the ground insulation impedance using the lookup table method, both amplitude and phase angle are utilized to improve monitoring accuracy and avoid situations where errors in amplitude or phase angle calculation lead to incorrect determination of the final ground insulation impedance.

[0141] Specifically, after obtaining the first ground insulation impedance reference value Z1, the second ground insulation impedance reference value Z2, the third ground insulation impedance reference value Z3, and the fourth ground insulation impedance reference value Z4 through step 410; in step 420, the difference between the first ground insulation impedance reference value Z1 and the second ground insulation impedance reference value Z2 is first calculated as the first difference value. Then, the first difference value is compared with a second preset threshold. Next, based on the comparison (judgment) result, if the absolute value of the first difference value is greater than or equal to the second preset threshold, it is considered that the difference between Z1 and Z2 is too large, indicating that at least one of the amplitude corresponding to Z1 and the phase angle corresponding to Z2 is incorrect, and resampling and determination are required, i.e., the AC insulation monitoring method is re-executed until the absolute value of the first difference value is less than the second preset threshold; and if the absolute value of the first difference value is less than the second preset threshold, the difference between the third ground insulation impedance reference value Z3 and the fourth ground insulation impedance reference value Z4 is calculated as the second difference value, and the second difference value is compared with the third preset threshold. After obtaining the second difference and comparing it with the third preset threshold, based on the comparison (judgment) result, if the absolute value of the second difference is greater than or equal to the third preset threshold, it is considered that the difference between Z3 and Z4 is too large, indicating that at least one of the amplitude corresponding to Z3 and the phase angle corresponding to Z4 is incorrect, and resampling and determination are required, i.e., the AC insulation monitoring method is re-executed until the absolute value of the second difference is less than the third preset threshold. When the absolute value of the second difference is less than the third preset threshold, the insulation resistance to ground of the first output terminal and the insulation resistance to ground of the inverter can be solved based on the third preset formula and the fourth preset formula (described later). The second and third preset thresholds can be set according to actual needs.

[0142] Optionally, the third preset formula is:

[0143] Z L = a1*Z1 + b1*Z2,

[0144] Among them, Z LZ1 is the first output terminal of the inverter to ground insulation impedance; a1 is the first preset weighting coefficient; b1 is the second preset weighting coefficient; Z1 is the first ground insulation impedance reference value; Z2 is the second ground insulation impedance reference value.

[0145] The fourth preset formula is:

[0146] Z N = a² * Z³ + b² * Z⁴

[0147] Among them, Z N Z1 is the second output terminal of the inverter to ground insulation impedance; Z2 is the third preset weighting coefficient; Z3 is the third ground insulation impedance reference value; Z4 is the fourth ground insulation impedance reference value.

[0148] Specifically, the solutions for the insulation resistance to ground of the first output terminal and the insulation resistance to ground of the second output terminal of the inverter can be obtained according to the third preset formula Z. L =a1*Z1+b1*Z2 determines the ground insulation impedance of the first output terminal, based on Z N =a2*Z3+b2*Z4 determines the ground insulation impedance of the second output terminal. Where a1 is the first preset weighting coefficient, b1 is the second preset weighting coefficient, a2 is the third preset weighting coefficient, and b2 is the fourth preset weighting coefficient. Since the ground impedance values ​​corresponding to amplitude and phase angle in the preset database may differ, preset weighting coefficients are used for weight correction. In some embodiments, 0 < a1 < 1, 0 < b1 < 1, 0 < a2 < 1, 0 < b2 < 1, and a1 + b1 = 1, a2 + b2 = 1. a1, b1, a2, and b2 can be set according to actual needs, or set according to the actual operating conditions of the inverter when constructing the preset database.

[0149] Optionally, combined Figure 3 As shown, the inverter includes a first pair of ground resistors and a second pair of ground resistors. The first output terminal is grounded through the first pair of ground resistors, and the second output terminal is grounded through the second pair of ground resistors.

[0150] The ground insulation impedance of an inverter is generally provided by a ground resistance and a ground capacitance. In certain special applications where the impedance effect of the ground capacitance is not considered (e.g., when the ground capacitance is small), the inverter's ground insulation impedance is provided by the ground resistance. For example, the first output terminal is grounded through a first ground resistance (denoted as R1), and the ground insulation impedance Z of the first output terminal is... L This is the resistance value of the first pair of ground resistors; the second output terminal is grounded through the second pair of ground resistors (denoted as R2), and the ground insulation impedance Z of the second output terminal is... N This is the resistance value of the second resistance to ground. Therefore, in the monitoring of the inverter's ground insulation impedance, the AC insulation monitoring circuit generally only needs to obtain U through sampling.L and U N The corresponding voltage amplitude, or obtained by sampling U L (or U) N By determining the corresponding voltage amplitude and phase angle, the output voltage phasor of the inverter can be obtained. Then, the impedance values ​​of resistors R1 and R2 are obtained, reducing the computational difficulty.

[0151] Optionally, in certain special applications where the inverter does not consider the impedance effect of the ground capacitance, solving for the ground insulation impedance of the first and second output terminals is equivalent to solving for two unknowns (R1, R2), which can be obtained by sampling U. L and U N The amplitude (or phase angle) is obtained. For example, taking an AC insulation monitoring circuit with a first sampling circuit for sampling the first output terminal and a second sampling circuit for sampling the second output terminal as an example, when the inverter enters the inverter state (operation), firstly, in step 100, when the controlled switch S1 is opened, the inverter's output voltage (first voltage) is collected (acquired) for subsequent calculation of the inverter output terminal's insulation impedance to ground. Then, in step 200, the controlled switch S1 is closed, resistor R3 is connected, and the relevant voltage information of the inverter output terminal's voltage to ground is collected through the sampling circuits (first sampling circuit and second sampling circuit), that is, the relevant voltage information of the inverter's first output terminal's voltage to ground and / or the second output terminal's voltage to ground is collected. Finally, in step 300, the voltage amplitude of the first voltage is extracted. Extract U L The corresponding voltage amplitudes A and U N The corresponding voltage amplitude B can be determined according to A and B perform Z... L With Z N The solution is as follows:

[0152]

[0153]

[0154] When the impedance effect of the ground capacitance is not considered, Z L =R1,Z N =R2. Alternatively, when the capacitance to ground (C1, C2) is known and R1 and R2 are unknown, or when the capacitance to ground (C1, C2) is unknown and R1 and R2 are known, it can also be determined by sampling U. L and U N The magnitude (or phase angle) is used to solve for the corresponding unknowns, as follows:

[0155]

[0156]

[0157]

[0158]

[0159] Optionally, in certain special applications where the inverter does not consider the impedance effect of the ground capacitance, solving for the ground insulation impedance of the first and second output terminals is equivalent to solving for two unknowns (R1, R2), which is obtained through a single sampling U L (or U) N The amplitude and phase angle can be obtained, reducing the sampling circuit to one. That is, the AC insulation monitoring circuit can be simplified by setting only the first sampling circuit to sample the first output terminal, or only the second sampling circuit to sample the second output terminal. For example, taking the AC insulation monitoring circuit with only the first sampling circuit sampling the first output terminal as an example, when the inverter enters the inverter state (operation), in step 100, when the controlled switch S1 is opened, the inverter's output voltage (first voltage) is collected. Then, in step 200, the controlled switch S1 is closed, resistor R3 is connected, and the relevant voltage information of the inverter's first output terminal to ground is collected through the sampling circuit (first sampling circuit). Finally, in step 300, the controller samples and processes the corresponding voltage information to extract the voltage amplitude of the first voltage. The voltage amplitude A and phase angle α of the voltage to ground at the first output terminal are extracted; through step 400, the voltage amplitude A and phase angle α of the voltage to ground at the first output terminal can be extracted. A and α perform Z... L (Z here) L =R1) and Z N (Z here) N The solution for =R2) is as follows:

[0160]

[0161]

[0162] When the impedance effect of the ground capacitance is not considered, Z L =R1,Z N =R2. Alternatively, when the capacitance to ground (C1, C2) is known and R1 and R2 are unknown, or when the capacitance to ground (C1, C2) is unknown and R1 and R2 are known, it can also be determined by sampling U. L (or U) N The unknowns are solved by the magnitude and phase angle of the equation, as follows:

[0163]

[0164]

[0165]

[0166]

[0167] Optionally, combined Figure 4 As shown, the inverter also includes a first pair of ground capacitors and a second pair of ground capacitors. The first pair of ground capacitors are connected in parallel across the first pair of ground resistors, and the second pair of ground capacitors are connected in parallel across the second pair of ground resistors.

[0168] In this embodiment, the inverter's ground insulation impedance is provided by a ground resistance and a ground capacitance. By setting a first ground capacitance and a second ground capacitance, the stability and reliability of the corresponding circuits of the inverter are ensured, and noise signals are filtered out. Specifically, the first output terminal is grounded through a first ground resistance R1 and a first ground capacitance (denoted as C1, which also represents capacitance), which is equivalent to the first ground resistance R1 and the first ground capacitance C1 being connected in parallel. The ground insulation impedance of the first output terminal is thus... The second output terminal is grounded through the second ground resistor R2 and the second ground capacitor (denoted as C2, which also represents capacitance). This is equivalent to the second ground resistor R2 and the second ground capacitor C2 being connected in parallel. Therefore, the ground insulation impedance of the second output terminal is... Among them, X C1 Capacitive reactance of C1 (X) C1 =1 / (ωC1)=1 / (2πfC1)), X C2 Capacitive reactance of C2 (X) C2 =1 / (ωC2)=1 / (2πfC2)). Thus, after obtaining Z L Z N After that, it can also be based on Solve for R1, C1, R2, and C2.

[0169] Optionally, combined Figure 4 As shown, the sampling circuit includes a grounded first sampling circuit and a second sampling circuit, and the first output terminal and the second output terminal are respectively connected to the controller through the first sampling circuit and the second sampling circuit.

[0170] In this embodiment, the first output terminal U L The signal input terminal connected to the first sampling circuit, and the second output terminal U N The signal input terminal connected to the second sampling circuit allows the first and second sampling circuits to respectively sample the signal at the first output terminal U. L Second output terminal U NThe voltage (or voltage characteristics) at the location are sampled, such as the corresponding amplitude and phase angle. The signal output terminals of both the first and second sampling circuits are connected to the signal input terminals of the controller, facilitating the transmission of the sampling results from each circuit to the controller. The controller then performs corresponding calculations based on the sampling results to ultimately obtain the AC insulation impedance to ground of the corresponding inverter as monitored by the AC insulation monitoring circuit. Both the first and second sampling circuits are grounded through their respective ports to suppress common-mode interference, ensure sampling safety, and guarantee the accuracy of the sampling results. By setting up the first and second sampling circuits, it is convenient to simultaneously calculate the insulation impedance to ground of the first and second output terminals based on their sampling results, and to facilitate mutual verification of the calculated results. This avoids the accuracy of the insulation impedance calculation being affected by a fault in one of the sampling circuits, thus ensuring the accuracy of the insulation impedance calculation.

[0171] Optionally, both the first sampling circuit and the second sampling circuit adopt differential sampling circuits.

[0172] In this embodiment, both the first sampling circuit and the second sampling circuit employ differential sampling circuits to acquire voltage characteristics such as voltage waveforms corresponding to the first and second output terminals. By using differential sampling circuits, the voltages input to the first and second sampling circuits via the first and second output terminals, respectively, are sampled sensitively, improving sampling accuracy and avoiding corresponding noise interference. Exemplarily, the differential sampling circuit includes operational amplifiers, capacitors, an integrator chip, and an ADC (analog-to-digital converter, used to achieve the digital output of the final sampled signal).

[0173] Optionally, the characteristic quantity of the first voltage also includes the voltage frequency; after step 400, the AC insulation monitoring method further includes:

[0174] Based on the voltage frequency and the insulation impedance of the first output terminal to ground and the insulation impedance of the second output terminal to ground, solve for the corresponding parameters of the first to ground resistance, the second to ground resistance, the first to ground capacitance and the second to ground capacitance.

[0175] Specifically, after obtaining the first output terminal to ground insulation impedance and the second output terminal to ground insulation impedance, if it is necessary to further determine the corresponding parameters of the first to ground resistance, the second to ground resistance, the first to ground capacitance, and the second to ground capacitance, then based on the inverter output voltage frequency f and the first output terminal to ground insulation impedance Z in the first voltage-related voltage information. L The insulation resistance Z of the second output terminal to ground NThe calculation of the corresponding parameters (such as the resistance value of the corresponding resistor, the capacitance of the corresponding capacitor, etc.) of the first pair of ground resistance, the second pair of ground resistance, the first pair of ground capacitance, and the second pair of ground capacitance can be performed according to the following formula:

[0176]

[0177]

[0178] ω = 2πf.

[0179] Optionally, the AC insulation monitoring method also includes a self-test step, which includes:

[0180] The controlled switch is disconnected, and the amplitude of the voltage to ground at the first output terminal and the amplitude of the voltage to ground at the second output terminal of the inverter are obtained.

[0181] Calculate the ratio of the magnitude of the voltage to ground at the first output terminal to the magnitude of the voltage to ground at the second output terminal;

[0182] Determine whether the ratio is greater than a first preset threshold, and determine whether the ratio is less than the reciprocal of the first preset threshold; wherein the first preset threshold is greater than the reciprocal of the first preset threshold;

[0183] An insulation fault alarm is triggered when the ratio is greater than a first preset threshold or less than the reciprocal of the first preset threshold.

[0184] In this embodiment, the AC insulation monitoring method includes a self-test step for performing an insulation fault self-test before the controlled switch is closed. For example, in step 100, when the inverter is running and the controlled switch is open, relevant voltage information (including amplitude, etc.) of the voltage to ground at the first and second output terminals of the inverter is acquired. This information can be obtained by sampling the first and second output terminals using a first sampling circuit and a second sampling circuit, respectively. Following step 100, in step 200, the ratio of the amplitude of the voltage to ground at the first output terminal to the amplitude of the voltage to ground at the second output terminal when the controlled switch is open is calculated. This ratio is compared with a first preset threshold (greater than 1) and its reciprocal. If the ratio is less than or equal to the first preset threshold and greater than or equal to its reciprocal, it is considered that no insulation fault to ground has occurred at either the first or second output terminal, the self-test is confirmed to be passed, and the controlled switch is closed to continue subsequent steps. However, if the ratio is greater than the first preset threshold or less than its reciprocal, it is considered that at least one of the first or second output terminals has an insulation fault to ground. In this case, an insulation fault alarm is directly triggered without closing the controlled switch or proceeding with subsequent steps, thus avoiding wasting computational resources. The first preset threshold can be set according to actual conditions; in some embodiments, the first preset threshold is 5.

[0185] Optionally, the self-test steps may also include:

[0186] In response to the determination that the ratio is less than or equal to the first preset threshold and greater than or equal to the reciprocal of the first preset threshold, the self-test is determined to be passed, the controlled switch is closed, and the voltage of the inverter's output terminal to ground is collected.

[0187] Specifically, the ratio of the amplitude of the voltage to ground at the first output terminal to the amplitude of the voltage to ground at the second output terminal when the controlled switch is open is calculated. This ratio is then compared with a first preset threshold (which is greater than 1) and its reciprocal. Based on the comparison (judgment) result, if the ratio is less than or equal to the first preset threshold and greater than or equal to its reciprocal, it is considered that no ground insulation fault has occurred at the first or second output terminal, the self-test is confirmed to be passed, the controlled switch is closed, and subsequent steps continue.

[0188] In other implementations, the self-test step further includes:

[0189] In response to the determination that the ratio is less than or equal to the first preset threshold and greater than or equal to the reciprocal of the first preset threshold, the self-test is determined to be fault-free, the self-test step is re-executed, and after two consecutive self-tests are performed without fault, the self-test is determined to be successful, the controlled switch is closed, and the voltage of the inverter's output terminal to ground is collected.

[0190] Specifically, to avoid the possibility of misjudgment in a single self-test process, the self-test step of this method is determined to be successful only after two (or more) consecutive self-tests have been performed without faults. That is, after the ratio of the amplitude of the first output terminal to ground voltage to the amplitude of the second output terminal to ground voltage when the controlled switch is open is less than or equal to the first preset threshold and greater than or equal to the reciprocal of the first preset threshold during two (or more) consecutive self-tests, the controlled switch is closed and the inverter's output terminal to ground voltage is collected.

[0191] Another embodiment of the present invention provides an AC insulation monitoring device, including an AC insulation monitoring circuit, a memory, and a processor;

[0192] The AC insulation monitoring circuit includes a controlled switch and a third resistor. One end of the controlled switch is used to connect to one output terminal of the inverter, and the other end of the controlled switch is grounded through the third resistor.

[0193] Memory, used to store computer programs;

[0194] A processor is used to implement the above-described AC insulation monitoring method when executing a computer program.

[0195] In this embodiment, the AC insulation monitoring device includes a memory, a processor, and the aforementioned AC insulation monitoring circuit, to implement the AC insulation monitoring method. The memory stores a computer program related to the AC insulation monitoring method, and the processor, when executing the computer program, cooperates with the AC insulation monitoring circuit to implement the AC insulation monitoring method. Thus, through the cooperation between the memory, processor, and AC insulation monitoring circuit, the smoothness, stability, and accuracy of the AC insulation monitoring method are ensured.

[0196] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for monitoring AC insulation, characterized in that, Based on the AC insulation monitoring circuit, the AC insulation monitoring circuit includes a controlled switch and a third resistor. One end of the controlled switch is used to connect to one output terminal of the inverter, and the other end of the controlled switch is grounded through the third resistor. The AC insulation monitoring method includes: The controlled switch is disconnected, and the output voltage of the inverter is collected as the first voltage. Control the closed switch to collect the voltage between the output terminal and ground of the inverter; Extract the characteristic quantities of the first voltage, and extract the characteristic quantities of the output terminal voltage to ground; Based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output terminal to ground voltage, the output terminal to ground insulation impedance of the inverter is determined. The inverter has a first output terminal and a second output terminal, and one end of the controlled switch is used to connect to the first output terminal or the second output terminal. The control of closing the controlled switch and acquiring the inverter's output voltage to ground includes: Control the closed switch to collect the voltage to ground of the first output terminal and the voltage to ground of the second output terminal of the inverter. The extraction of the characteristic quantities of the first voltage and the extraction of the characteristic quantities of the output terminal voltage to ground include: Extract the voltage phasor of the first voltage, and extract the amplitude and phase angle of the voltage at the first output terminal to ground, and extract the amplitude and phase angle of the voltage at the second output terminal to ground; The step of determining the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage includes: Based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal of the inverter to ground, the amplitude and phase angle of the voltage at the second output terminal to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground, and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal to ground and the insulation impedance at the second output terminal to ground are determined, including: Using a lookup table method, based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal to ground, and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation resistance to ground of the first output terminal and the insulation resistance to ground of the inverter are determined, specifically as follows: Based on the extracted voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal, and the amplitude and phase angle of the voltage to ground at the second output terminal, a query is performed based on a preset database to obtain the first ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the first output terminal, the second ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the first output terminal, the third ground insulation impedance reference value corresponding to the amplitude of the voltage to ground at the second output terminal, and the fourth ground insulation impedance reference value corresponding to the phase angle of the voltage to ground at the second output terminal. The first output terminal insulation impedance to ground of the inverter is calculated based on the first and second ground insulation impedance reference values; and the second output terminal insulation impedance to ground of the inverter is calculated based on the third and fourth ground insulation impedance reference values.

2. The AC insulation monitoring method as described in claim 1, characterized in that, The control of closing the controlled switch and acquiring the inverter's output voltage to ground includes: Control the closed switch to collect the voltage to ground of the first output terminal and the voltage to ground of the second output terminal of the inverter. The extraction of the characteristic quantities of the first voltage and the extraction of the characteristic quantities of the output terminal voltage to ground include: Extract the voltage phasor of the first voltage, and extract the amplitudes of the voltage at the first output terminal to ground and the voltage at the second output terminal to ground, respectively; The step of determining the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage includes: Based on the preset voltage phasor of the first voltage, the amplitude of the voltage to ground at the first output terminal of the inverter, the amplitude of the voltage to ground at the second output terminal of the inverter, the relationship between the insulation impedance to ground at the first output terminal of the inverter and the insulation impedance to ground at the second output terminal of the inverter, and based on the extracted voltage phasor of the first voltage, the amplitude of the voltage to ground at the first output terminal and the amplitude of the voltage to ground at the second output terminal, the insulation impedance to ground at the first output terminal and the insulation impedance to ground at the second output terminal of the inverter are determined.

3. The AC insulation monitoring method as described in claim 2, characterized in that, The step of determining the insulation resistance of the inverter's first and second output terminals to ground based on the preset relationship between the voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground of the inverter, the amplitude of the voltage at the second output terminal to ground of the inverter, the insulation resistance of the inverter's first and second output terminals to ground, and based on the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground, includes: Substitute the extracted voltage phasor of the first voltage, the amplitude of the voltage at the first output terminal to ground, and the amplitude of the voltage at the second output terminal to ground into the first preset formula and the second preset formula. The first preset formula and the second preset formula are combined to solve the problem and calculate the first output terminal insulation resistance to ground and the second output terminal insulation resistance to ground of the inverter. The first preset formula is: ， In the above formula, Let A represent the voltage phasor of the first voltage, and let A represent the magnitude of the voltage at the first output terminal relative to ground. Z L This indicates the insulation resistance of the first output terminal to ground. Z N R3 represents the insulation resistance of the second output terminal to ground, and R3 represents the resistance value of the third resistor. The second preset formula is: ， In the above formula, B represents the amplitude of the voltage to ground at the second output terminal.

4. The AC insulation monitoring method as described in claim 1, characterized in that, The control of closing the controlled switch and acquiring the inverter's output voltage to ground includes: Control the closed switch to collect the voltage to ground of the first output terminal or the voltage to ground of the second output terminal of the inverter. The extraction of the characteristic quantities of the first voltage and the extraction of the characteristic quantities of the output terminal voltage to ground include: Extract the voltage phasor of the first voltage, and extract the amplitude and phase angle of the voltage at the first output terminal to ground or the voltage at the second output terminal to ground; The step of determining the output-to-ground insulation impedance of the inverter based on the extracted characteristic values ​​of the first voltage and the extracted characteristic values ​​of the output-to-ground voltage includes: Based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the first output terminal of the inverter to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage and the amplitude and phase angle of the voltage at the first output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground are determined; or, based on the preset voltage phasor of the first voltage, the amplitude and phase angle of the voltage at the second output terminal of the inverter to ground, the relationship between the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground, and based on the extracted voltage phasor of the first voltage and the amplitude and phase angle of the voltage at the second output terminal to ground, the insulation impedance at the first output terminal of the inverter to ground and the insulation impedance at the second output terminal of the inverter to ground are determined.

5. The AC insulation monitoring method as described in claim 1, characterized in that, The lookup table method corresponds to a preset database constructed based on the preset relationship between the voltage phasor of the first voltage, the amplitude and phase angle of the voltage to ground at the first output terminal of the inverter and the amplitude and phase angle of the voltage to ground at the second output terminal of the inverter, and the insulation impedance to ground at the first output terminal of the inverter and the insulation impedance to ground at the second output terminal of the inverter.

6. The AC insulation monitoring method as described in claim 1, characterized in that, The first output terminal to ground insulation impedance of the inverter is calculated based on the first ground insulation impedance reference value and the second ground insulation impedance reference value. The second output terminal of the inverter is calculated to ground based on the third and fourth ground insulation impedance reference values, including: Calculate the difference between the first reference value of insulation resistance to ground and the second reference value of insulation resistance to ground, and use it as the first difference; Determine whether the absolute value of the first difference is less than the second preset threshold; In response to determining that the absolute value of the first difference is greater than or equal to the second preset threshold, the AC insulation monitoring method is re-executed; In response to determining that the absolute value of the first difference is less than the second preset threshold, the difference between the third ground insulation impedance reference value and the fourth ground insulation impedance reference value is calculated as the second difference value, and it is determined whether the absolute value of the second difference value is less than the third preset threshold value. In response to determining that the absolute value of the second difference is greater than or equal to the third preset threshold, the AC insulation monitoring method is re-executed; In response to the determination that the absolute value of the second difference is less than the third preset threshold, the first output terminal to ground insulation impedance of the inverter is calculated according to the first ground insulation impedance reference value, the second ground insulation impedance reference value and the third preset formula, and the second output terminal to ground insulation impedance is calculated according to the third ground insulation impedance reference value, the fourth ground insulation impedance reference value and the fourth preset formula.

7. The AC insulation monitoring method as described in claim 6, characterized in that, The third preset formula is: Z L =a1 Z 1+b1 Z 2, in, Z L , where a1 is the insulation resistance to ground of the first output terminal of the inverter; b1 is the first preset weighting coefficient; and b1 is the second preset weighting coefficient. Z 1 represents the first reference value for insulation resistance to ground. Z 2 is the second reference value for insulation resistance to ground; The fourth preset formula is: Z N =a2 Z 3+b2 Z 4. in, Z N a2 is the insulation resistance to ground of the second output terminal of the inverter; b2 is the third preset weighting coefficient; b2 is the fourth preset weighting coefficient. Z 3 is the reference value for the third ground insulation impedance. Z 4 is the reference value for the fourth earth insulation impedance.

8. The AC insulation monitoring method as described in claim 1, characterized in that, The AC insulation monitoring method further includes a self-test step, which includes: The controlled switch is disconnected, and the amplitude of the voltage to ground at the first output terminal and the amplitude of the voltage to ground at the second output terminal of the inverter are obtained. Calculate the ratio of the amplitude of the voltage to ground at the first output terminal to the amplitude of the voltage to ground at the second output terminal; Determine whether the ratio is greater than a first preset threshold, and determine whether the ratio is less than the reciprocal of the first preset threshold; wherein, the first preset threshold is greater than the reciprocal of the first preset threshold; An insulation fault alarm is triggered in response to the determination that the ratio is greater than a first preset threshold or that the ratio is less than the reciprocal of the first preset threshold.

9. An AC insulation monitoring device, characterized in that, Includes AC insulation monitoring circuitry, memory, and processor; The AC insulation monitoring circuit includes a controlled switch and a third resistor. One end of the controlled switch is used to connect to one output terminal of the inverter, and the other end of the controlled switch is grounded through the third resistor. The memory is used to store computer programs; The processor is configured to implement the AC insulation monitoring method as described in any one of claims 1 to 8 when executing the computer program.

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