Insulation detection method, circuit and equipment

Abstract

The invention discloses an insulation detection method, circuit and equipment, and belongs to the field of insulation detection.The insulation detection method comprises the steps that an excitation signal with a preset frequency is injected into a high-voltage electrical loop of an automatic control system, then time domain sampling is conducted on the excitation signal injected into the high-voltage electrical loop to obtain a sampling signal, and then the excitation signal is obtained from the sampling signal; according to the method, the frequency domain amplitude of the excitation signal with the preset frequency is determined, and finally, the resistance value of the insulation impedance corresponding to the frequency domain amplitude can be determined according to a preset corresponding relation, so that the detected resistance value of the insulation impedance accurately covers insulation impedance changes outside and inside an energy storage system in a high-voltage electrical loop; and moreover, the influence of electromagnetic interference is eliminated, the detection precision is improved, and the automation degree is relatively high.

Description

Technical Field

[0001] The present invention relates to the field of insulation detection, and in particular to an insulation detection method, circuit and device. Background Art

[0002] For an industrial automation control system with an energy storage system as the input power source, it is of great significance to detect the insulation impedance between the high-voltage electrical circuit and the outer casing. However, in the related art, there is a lack of a mature method for detecting the insulation impedance between the high-voltage electrical circuit and the outer casing. It is not only difficult to comprehensively and accurately detect the value of the insulation impedance between the high-voltage electrical circuit and the outer casing, but also requires manual participation during the detection process, resulting in a low degree of automation.

[0003] Therefore, how to provide a solution to the above technical problems is an issue that those skilled in the art need to solve currently. Summary of the Invention

[0004] The object of the present invention is to provide an insulation detection method, circuit and device. First, an excitation signal with a preset frequency is injected into the high-voltage electrical circuit of the automation control system, then the excitation signal injected into the high-voltage electrical circuit is sampled in the time domain to obtain a sampling signal, and then the frequency-domain amplitude of the excitation signal with the preset frequency is determined from the sampling signal. Finally, according to the preset corresponding relationship, the value of the insulation impedance corresponding to the frequency-domain amplitude can be determined, so that the detected value of the insulation impedance accurately covers the "change of the insulation impedance between the outside and the inside of the energy storage system in the high-voltage electrical circuit", and the influence of electromagnetic interference is eliminated, improving the detection accuracy and having a high degree of automation.

[0005] To solve the above technical problems, the present invention provides an insulation detection method, including:

[0006] Inject an excitation signal with a preset frequency into the high-voltage electrical circuit of the automation control system, where the automation control system uses an energy storage system as the input power source;

[0007] Perform time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal;

[0008] Determine the frequency-domain amplitude of the excitation signal with the preset frequency from the sampling signal;

[0009] According to the preset corresponding relationship, determine the value of the insulation impedance corresponding to the frequency-domain amplitude, where the preset corresponding relationship is: the corresponding relationship between the frequency-domain amplitude and the insulation impedance.

[0010] On the other hand, injecting an excitation signal with a preset frequency into the high-voltage electrical circuit of the automation control system includes:

[0011] Output an excitation signal with a preset frequency. After the excitation signal is amplitude-amplified and the DC bias is removed, inject the AC component of the excitation signal into the high-voltage electrical circuit.

[0012] On the other hand, after performing time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal, it further includes:

[0013] After stopping injecting the excitation signal with a preset frequency into the high-voltage electrical circuit of the automatic control system, determine the frequency-domain amplitude of the excitation signal with the preset frequency from the sampling signal.

[0014] On the other hand, determining the frequency-domain amplitude of the excitation signal with the preset frequency from the sampling signal includes:

[0015] Input the sampling signal into a frequency-domain amplitude calculation model to obtain the frequency-domain amplitude of the excitation signal with the preset frequency in the sampling signal;

[0016] Among them, the frequency-domain amplitude calculation model is constructed based on the method of the forward Fourier transform, and the frequency-domain amplitude calculation model has the real part coefficients and imaginary part coefficients of the pre-calculated forward discrete Fourier transform.

[0017] On the other hand, the excitation signal includes two mutually differential sine signals.

[0018] To solve the above technical problems, the present invention also provides an insulation detection circuit, including:

[0019] A controller for implementing the steps of the insulation detection method as described above;

[0020] A signal injection circuit respectively connected to the controller and the high-voltage electrical circuit of the automatic control system.

[0021] On the other hand, the signal injection circuit includes a signal amplification circuit module and a resistor-capacitor coupling circuit;

[0022] The signal amplification circuit is connected to the controller, and the signal amplification circuit is used to amplitude-amplify the excitation signal;

[0023] The resistor-capacitor coupling circuit is respectively connected to the controller, the signal amplification circuit and the high-voltage electrical circuit, and the resistor-capacitor coupling circuit is used to filter out the DC bias and transmit the AC component of the excitation signal.

[0024] On the other hand, it further includes a switch provided in the resistor-capacitor coupling circuit, and the switch is used to close the connection between the high-voltage electrical circuit and the signal injection circuit after performing time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal.

[0025] On the other hand, it further includes a signal conversion circuit disposed between the resistor-capacitor coupling circuit and the controller, and the signal conversion circuit is configured to adjust the amplitude of the excitation signal in the signal injection circuit within the signal detection range of the controller.

[0026] To solve the above technical problems, the present invention further provides an insulation detection device, including: the insulation detection circuit as described above and the high-voltage electrical circuit of the automatic control system.

[0027] Beneficial effects: The present invention provides an insulation detection method. Considering that (1) the excitation signal with good penetration can propagate in the entire high-voltage electrical circuit, so that the amplitude of the excitation signal can be affected by "the change of the insulation impedance outside and inside the energy storage system in the high-voltage electrical circuit", and (2) the conversion of the frequency-domain amplitude can eliminate the electromagnetic interference received by the time-domain waveform. Therefore, the present invention first injects an excitation signal with a preset frequency into the high-voltage electrical circuit of the automatic control system, then performs time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal, then determines the frequency-domain amplitude of the excitation signal with the preset frequency from the sampling signal, and finally can determine the resistance value of the insulation impedance corresponding to the frequency-domain amplitude according to the preset corresponding relationship, so that the detected resistance value of the insulation impedance accurately covers "the change of the insulation impedance outside and inside the energy storage system in the high-voltage electrical circuit", and eliminates the influence of electromagnetic interference, improves the detection accuracy, and has a relatively high degree of automation.

[0028] The present invention further provides an insulation detection circuit and device, which have the same beneficial effects as the above insulation detection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the related technologies and embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a schematic flowchart of the first insulation detection method provided by the present invention;

[0031] Figure 2 It is a schematic structural diagram of an insulation detection circuit provided by the present invention;

[0032] Figure 3 It is a schematic structural diagram of a signal amplification circuit provided by the present invention;

[0033] Figure 4 It is a schematic structural diagram of a resistor-capacitor coupling circuit and a switching switch provided by the present invention;

[0034] Figure 5 Schematic diagram of a signal conversion circuit provided by the present invention;

[0035] Figure 6 Schematic diagram of the process of the second insulation detection method provided by the present invention;

[0036] Figure 7 Schematic diagram of the process of the third insulation detection method provided by the present invention. Detailed implementation manners

[0037] The core of the present invention is to provide an insulation detection method, circuit and device. First, an excitation signal with a preset frequency is injected into the high-voltage electrical circuit of the automated control system, and then the excitation signal injected into the high-voltage electrical circuit is sampled in the time domain to obtain a sampling signal. Then, from the sampling signal, the frequency-domain amplitude of the excitation signal with the preset frequency is determined. Finally, according to the preset corresponding relationship, the resistance value of the insulation impedance corresponding to the frequency-domain amplitude can be determined, so that the detected resistance value of the insulation impedance accurately covers the "insulation impedance change between the outside and the inside of the energy storage system in the high-voltage electrical circuit", and eliminates the influence of electromagnetic interference, improves the detection accuracy, and has a high degree of automation.

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Please refer to Figure 1 , Figure 1 Schematic diagram of the process of the first insulation detection method provided by the present invention. This insulation detection method is applied to a controller and includes:

[0040] S101: Inject an excitation signal with a preset frequency into the high-voltage electrical circuit of the automated control system, where the automated control system uses an energy storage system as the input power source;

[0041] Specifically, considering the technical problems in the above background art and also considering that (1) an excitation signal with good penetrability can propagate throughout the high-voltage electrical circuit, so that the amplitude of the excitation signal can be affected by the "change in the insulation impedance between the outside and inside of the energy storage system in the high-voltage electrical circuit", and (2) the conversion of the frequency-domain amplitude can eliminate the electromagnetic interference received by the time-domain waveform. Therefore, in the embodiments of the present invention, it is desired to detect the insulation impedance between the high-voltage electrical circuit and the outer casing of the automatic control system comprehensively and accurately by the method of "injecting an excitation signal into the high-voltage electrical circuit, performing frequency-domain conversion on the sampled excitation signal, and determining the insulation impedance". Therefore, in this step, an excitation signal with a preset frequency can be first injected into the high-voltage electrical circuit of the automatic control system, so that the excitation signal generates an amplitude change due to the "change in the insulation impedance between the outside and inside of the energy storage system in the high-voltage electrical circuit".

[0042] Specifically, the excitation signal can be a sine signal with excellent penetrability; the automatic control system (with the energy storage system as the input power source) can be of various types. For example, it can be a multi-axis drive type frequency converter. The multi-axis drive type frequency converter has been increasingly applied to automatic control systems. In the multi-axis drive type frequency converter, the rectification unit and the inversion unit are separately assembled. The rectification unit converts three-phase alternating current into a DC power supply, and then is connected to multiple inversion units through a common busbar method. Many factories, considering the situation of accidental power failure, use a high-voltage energy storage battery system as a backup power supply and connect it to the common busbar end of the inversion unit. Once an accidental power failure occurs at the front end of the inverter, the high-voltage energy storage battery system can be timely switched to be used as a power supply to ensure the normal operation of the load equipment at the back end of the inversion unit.

[0043] Among them, the "change in the insulation impedance between the outside and inside of the energy storage system in the high-voltage electrical circuit" The change in the insulation impedance outside the energy storage system can include the insulation impedance of the bus output circuit outside the energy storage system, while the insulation impedance inside the energy storage system can include the change in the insulation impedance caused by phenomena such as "copper bar shedding or electrolyte leakage due to cell damage in the energy storage system". This will lead to a decrease in the insulation performance between the high-voltage electrical circuit and the outer casing, resulting in an increase in leakage current; it is worth mentioning that this increase in leakage current not only greatly affects the normal use of the entire automatic control system, but also poses a serious threat to the personal safety of on-site operators. Therefore, it is of great significance to comprehensively and accurately detect the "insulation impedance between the high-voltage electrical circuit and the outer casing".

[0044] Specifically, the preset frequency can be set flexibly by oneself, and the embodiments of the present invention do not make any limitations in this regard.

[0045] S102: Perform time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal;

[0046] Specifically, while injecting an excitation signal into the high-voltage electrical appliance circuit, it can be considered that the excitation signal has been affected by the insulation impedance between the high-voltage electrical circuit and the outer casing, resulting in an amplitude change. Therefore, the excitation signal injected into the high-voltage electrical circuit can be sampled in the time domain to obtain a sampling signal, which is used as the data basis for subsequent steps to detect the insulation impedance.

[0047] S103: Determine the frequency-domain amplitude of the excitation signal at a preset frequency from the sampling signal;

[0048] Specifically, the sampling signal is a complex time-domain signal, which includes sine and cosine components of different frequencies. Except for the sine excitation signal at the preset frequency, the remaining components can be regarded as interference. Therefore, in order to accurately determine the amplitude of the excitation signal, in the embodiments of the present invention, the frequency-domain amplitude of the excitation signal at the preset frequency can be determined from the sampling signal, so as to filter out the interference signals of other frequencies in the time-domain sampling signal, highlight the components of the required excitation signal, and thus improve the accuracy of the finally determined insulation impedance.

[0049] S104: Determine the resistance value of the insulation impedance corresponding to the frequency-domain amplitude according to a preset correspondence relationship, where the preset correspondence relationship is: the correspondence relationship between the frequency-domain amplitude and the insulation impedance.

[0050] Specifically, considering that the "insulation impedance between the high-voltage electrical circuit and the outer casing" affects the frequency-domain amplitude of the excitation signal, in order to facilitate the determination of the insulation impedance according to the frequency-domain amplitude, in the embodiments of the present invention, the preset correspondence relationship can be determined in advance. After determining the frequency-domain amplitude of the excitation signal, the resistance value of the insulation impedance corresponding to the frequency-domain amplitude can be determined efficiently and accurately according to the preset correspondence relationship.

[0051] Specifically, the frequency-domain calculation method in the embodiments of the present invention has the characteristics of strong anti-interference ability, solves the problems that the time-domain amplitude algorithm cannot work normally and stably in a complex electromagnetic interference environment, and the detection circuit is easily affected by the internal temperature change of the energy storage system, resulting in a decrease in detection accuracy.

[0052] The present invention provides an insulation detection method. Considering that (1) an excitation signal with good penetrability can propagate throughout the high-voltage electrical circuit, so that the amplitude of the excitation signal can be affected by "the change in insulation impedance outside and inside the energy storage system in the high-voltage electrical circuit", and (2) the conversion of the frequency-domain amplitude can eliminate the electromagnetic interference received by the time-domain waveform. Therefore, the present invention first injects an excitation signal with a preset frequency into the high-voltage electrical circuit of the automatic control system, then performs time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal, and then determines the frequency-domain amplitude of the excitation signal with the preset frequency from the sampling signal. Finally, according to the preset corresponding relationship, the resistance value of the insulation impedance corresponding to the frequency-domain amplitude can be determined, so that the detected resistance value of the insulation impedance accurately covers "the change in insulation impedance outside and inside the energy storage system in the high-voltage electrical circuit", and eliminates the influence of electromagnetic interference, improves the detection accuracy, and has a relatively high degree of automation.

[0053] Based on the above embodiments:

[0054] As an optional embodiment, injecting an excitation signal with a preset frequency into the high-voltage electrical circuit of the automatic control system includes:

[0055] Output an excitation signal with a preset frequency. After the excitation signal is amplified in amplitude and the DC bias is removed, the AC component of the excitation signal is injected into the high-voltage electrical circuit.

[0056] Specifically, on the one hand, considering that the amplitude of the excitation signal output by the controller is small and is easily affected by noise interference during transmission and detection, resulting in a reduction in detection accuracy; on the other hand, considering that "in insulation detection, the DC component may interfere with the detection result and affect the judgment of the insulation state". Therefore, in the embodiments of the present invention, after the output excitation signal is amplified in amplitude and the DC bias is removed, the AC component of the excitation signal can be injected into the high-voltage electrical circuit. On the one hand, the amplified signal has a larger amplitude, and during the subsequent sampling process, the signal intensity is stronger relative to the noise, and can more accurately reflect the insulation state of the object to be detected, improving the overall signal-to-noise ratio of the insulation detection process. On the other hand, the excitation signal with the DC bias filtered out can support more accurate insulation detection.

[0057] As an optional embodiment, after performing time-domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal, it further includes:

[0058] After stopping injecting the excitation signal with a preset frequency into the high-voltage electrical circuit of the automatic control system, then determine the frequency-domain amplitude of the excitation signal with the preset frequency from the sampling signal.

[0059] Specifically, considering that the insulation impedance detection requirement does not always exist, the injection and termination of the excitation signal can be carried out according to the insulation detection requirement, so as to reduce the impact on the high-voltage electrical circuit and prevent the high-voltage electrical circuit from affecting the insulation detection circuit. At the same time, when performing insulation detection, timing moments such as power-on and power-off that are prone to false detection can be avoided. Therefore, in the embodiment of the present invention, the injection of the excitation signal with a preset frequency into the high-voltage electrical circuit of the automated control system can be stopped, and after stopping the injection of the excitation signal with a preset frequency into the high-voltage electrical circuit of the automated control system, the frequency-domain amplitude of the excitation signal with a preset frequency can be determined from the sampling signal.

[0060] As an alternative embodiment, determining the frequency-domain amplitude of the excitation signal with a preset frequency from the sampling signal includes:

[0061] Based on the forward discrete Fourier transform method, the frequency-domain amplitude of the excitation signal with a preset frequency is determined from the sampling signal.

[0062] Specifically, considering that the sampling signal in the time domain may be distorted due to electromagnetic interference, however, the complex sampling signal can be decomposed into sine and cosine components of different frequencies. The components of the excitation signal with a preset frequency have relatively stable characteristics in the frequency domain, and the forward discrete Fourier transform method can efficiently determine the frequency-domain amplitude of the excitation signal with a preset frequency in the sampling signal. Therefore, in the embodiment of the present invention, based on the forward discrete Fourier transform method, the frequency-domain amplitude of the excitation signal with a preset frequency can be determined from the sampling signal.

[0063] Of course, in addition to the forward discrete Fourier transform method, other methods can also be used to determine the frequency-domain amplitude of the excitation signal with a preset frequency from the sampling signal, and the embodiment of the present invention does not limit this here.

[0064] As an alternative embodiment, based on the forward discrete Fourier transform method, determining the frequency-domain amplitude of the excitation signal with a preset frequency from the sampling signal includes:

[0065] Input the sampling signal into the frequency-domain amplitude calculation model to obtain the frequency-domain amplitude of the excitation signal with a preset frequency in the sampling signal;

[0066] Wherein, the frequency-domain amplitude calculation model is constructed based on the forward Fourier transform method, and the frequency-domain amplitude calculation model has the real part coefficient and the imaginary part coefficient of the forward discrete Fourier transform calculated in advance.

[0067] Specifically, considering the frequency-domain amplitude calculation model based on the forward discrete Fourier transform, the calculation of sine and cosine involves a huge amount of computation, which will significantly reduce the efficiency of determining the frequency-domain amplitude. After analysis, it is found that the real and imaginary coefficients of the forward discrete Fourier transform can be determined by pre-calculation, and by substituting the real and imaginary coefficients into the frequency-domain amplitude calculation model, this part of the sine and cosine calculation process can be omitted when using the calculation model. Therefore, in the embodiments of the present invention, a frequency-domain amplitude calculation model can be constructed based on the forward Fourier transform method, and the real and imaginary coefficients of the forward discrete Fourier transform can be pre-calculated. Then, when using the frequency-domain amplitude calculation model combined with the real and imaginary coefficients, the frequency-domain amplitude of the excitation signal with a preset frequency in the sampling signal can be efficiently determined.

[0068] Specifically, the frequency-domain amplitude calculation model can be:

[0069] ; (1)

[0070] Where X is the frequency-domain amplitude of the excitation signal in the sampling signal; n is the sampling point sequence number; N is the number of sampling points within a set period T; and Dsa[N] is the time-domain amplitude array in the sampling signal.

[0071] Specifically, the real coefficient C Re and the imaginary coefficient C Im of the forward discrete Fourier transform can be pre-calculated, and the time-domain amplitude array of the sampling signal is subjected to the forward discrete Fourier transform to obtain the frequency-domain amplitude X of the excitation signal with a preset frequency in the sampling signal. The expression form of the above frequency-domain amplitude calculation model with respect to the real and imaginary coefficients is:

[0072] ; (2)

[0073] Where the real coefficient C Re can be expressed as:

[0074] ; (3)

[0075] The imaginary coefficient C Im can be expressed as:

[0076] ; (4)

[0077] As an alternative embodiment, the excitation signal includes two mutually differential sine signals.

[0078] Specifically, considering that a single-channel excitation signal is prone to severe distortion after being affected by interference signals in a high-voltage electrical environment with strong electromagnetic interference, which greatly reduces the accuracy of insulation detection. Since the signals transmitted on the two lines of a differential signal are equal in magnitude and opposite in polarity, and only the difference between the two signals is concerned at the receiving end, the influence of common-mode interference on the difference is extremely small. That is, two sinusoidal signals that are differential to each other have the advantage of strong anti-interference ability. Therefore, the excitation signal in the embodiments of the present invention can be two sinusoidal signals that are differential to each other.

[0079] Among them, the controller can output two sinusoidal signals that are differential to each other through the digital-to-analog converter inside itself. Figure 2 DAC1 and DAC2 in [[ ]] are the output channels of two DACs (Digital-to-Analog Converter), and correspondingly, signal sampling can be performed through two ADC (Analog-to-Digital Converter) channels, that is Figure 2 ADC1 and ADC2 in [[ ]].

[0080] To better illustrate the embodiments of the present invention, please refer to Figure 6 , Figure 6 which is a schematic flowchart of the second insulation detection method provided by the present invention. Figure 6 The process in [[ ]] includes: the controller core initializes each part of the peripherals (including ADC, DAC, DMA, and GPIO peripherals), sets the analog-to-digital converter to differential input mode, and allocates a buffer space (in RAM); within a set period, the controller core starts the digital-to-analog converter to generate two differential sinusoidal excitation signals, and (enables GPIO) controls the switching switch to inject the sinusoidal excitation signals into the high-voltage electrical circuit; within a set period, the controller core starts the analog-to-digital converter to sample the sinusoidal excitation signals, and (enables DMA) stores the sampled signals into the pre-allocated buffer space in sequence; (controls the switching switch to turn off by suspending the GOIP peripheral), and imports the sampled signals in the buffer space into the frequency-domain amplitude calculation model in sequence; performs the forward discrete Fourier transform on the time-domain amplitude array of the sampled signals by combining the pre-calculated forward discrete Fourier transform coefficients to obtain the frequency-domain amplitude of the sampled signals; determines the resistance value of the insulation impedance corresponding to the frequency-domain amplitude according to the preset corresponding relationship.

[0081] Among them, when each sampling is completed, the DMA (Direct Memory Access) peripheral directly transfers the sampling data to the controller's RAM (Random Access Memory) for storage, forming a sampling array Dsa[N]. This data transfer method greatly reduces the overhead of occupying the controller kernel during data transfer and also ensures that no packet loss occurs during data transfer; the on / off of the switching switch can be accurately controlled through the GPIO (General-Purpose Input / Output) peripheral.

[0082] Among them, the controller in the embodiment of the present invention can be composed of a general linear power supply and the minimum system of a microcontroller chip. Among them, the general linear power supply can provide a stable voltage for the entire circuit; the microcontroller chip can generate two sinusoidal excitation signals that are differential to each other, and perform equal-time-interval sampling on the signal to be detected through a differential-input analog-to-digital converter.

[0083] As an alternative embodiment, determining the resistance value of the insulation impedance corresponding to the frequency-domain amplitude according to a preset correspondence relationship includes:

[0084] Determine the preset range where the frequency-domain amplitude is located and use it as the target range;

[0085] According to the preset relational expression corresponding to the target range, determine the resistance value of the insulation impedance corresponding to the frequency-domain amplitude, where the preset relational expression is obtained by using the linear calibration method.

[0086] Specifically, in order to be able to quickly and accurately determine the insulation impedance according to the frequency-domain amplitude, in the embodiment of the present invention, the preset relational expressions (the relational expressions between the frequency-domain amplitude and the insulation impedance) for "different ranges of the corresponding frequency-domain amplitude" can be obtained by the linear calibration method. Then, the preset range where the frequency-domain amplitude is located can be first determined and used as the target range, and then, according to the preset relational expression corresponding to the target range, the resistance value of the insulation impedance corresponding to the frequency-domain amplitude can be determined.

[0087] Among them, the linear calibration process of each preset relational expression is as follows:

[0088] Use the linear calibration method to obtain the frequency-domain amplitude X of the sampling signal i and the mapping relationship with the insulation impedance value R i The linear calibration method and the process of obtaining the conversion mapping relationship table are as follows:

[0089] First, use the standard resistor R for the measured insulation resistance i (i ∈ N +)Perform substitution, then convert the sampled signal into a time-domain amplitude array, and calculate the frequency-domain amplitude X of the sampled signal using the above-mentioned forward discrete Fourier transform method i ; According to the measured resistance value sequence R i and the frequency-domain amplitude sequence X of the sampled signal i Make a mapping table of the conversion relationship between the two, that is, divide the measured resistance value sequence R i into different resistance value intervals at equal intervals with a gradient of ∆R, and calculate the standard resistance value R in each resistance value interval i and the frequency-domain amplitude X of the sampled signal i of the first-order linear function formula (that is, the preset relationship), including the slope S i and the offset O i ;

[0090] Ri = i * ∆R (i ∈ N + ); (5)

[0091] ; (6)

[0092] ; (7)

[0093] Specifically, Table 1 below is a table of preset relationships corresponding to different frequency-domain amplitude ranges. The table shows the linear slope and zero-offset in the preset relationship under different frequency-domain amplitude ranges. After determining the frequency-domain amplitude, the target range where the frequency-domain amplitude is located can be determined, and then the linear slope and zero-offset required for its preset relationship can be obtained by indexing through the look-up table method. Furthermore, the resistance value R of the insulation impedance can be calculated through the determined preset relationship o .

[0094] Table 1

[0095]

[0096] Among them, the preset relationship can be expressed as:

[0097] R o = S i * X + O i ; (8)

[0098] To better illustrate the embodiments of the present invention, please refer to Figure 7 , Figure 7Schematic flowchart of the third insulation detection method provided by the present invention. The process in the figure includes: initialization of the peripherals of the controller; calculation of discrete Fourier transform coefficients and setting of real and imaginary part arrays; setting of the conversion mapping table (i.e., Table 1) between the frequency-domain amplitude of the sampling signal and the insulation impedance according to the linear calibration process; opening up the cache space of the controller and sending the start and end addresses to the DMA peripheral for setting; starting the timer and enabling the interrupt function; starting the output of the DAC peripheral and enabling DO1 to be at a high level; starting the sampling of the ADC peripheral (sampling frequency f), starting the transmission of the DMA peripheral and enabling the interrupt function; performing one ADC sampling and one DMA transmission; after the DMA transmission is completed, determining whether an interrupt has occurred. If not, returning to the previous step. If so, stopping the sampling of the ADC peripheral, closing the DMA peripheral interrupt and loading the sampling data into the sample array Dsa[N]; calculating the frequency-domain amplitude X of the sampling signal; determining the index number of the conversion mapping table according to the frequency-domain amplitude X of the sampling signal; looking up the slope and offset of the preset relational expression according to the index number; calculating the resistance value of the insulation impedance according to the preset relational expression; finally, the output enable of the DAC peripheral can be turned off to make DO1 at a low level and waiting for the next action of "starting the output of the DAC peripheral and enabling DO1 to be at a high level".

[0099] The present invention also provides an insulation detection circuit, including:

[0100] A controller for implementing the steps of the insulation detection method in the foregoing embodiments;

[0101] A signal injection circuit respectively connected to the high-voltage electrical circuit of the controller and the automation control system.

[0102] Specifically, for better illustration of the embodiments of the present invention, please refer to Figure 2 , Figure 2 Schematic structural diagram of an insulation detection circuit provided by the present invention. Considering that the controller can inject the generated excitation signal into the high-voltage electrical circuit with the help of relevant circuits, which is beneficial to improving the signal-to-noise ratio and anti-interference effect. Therefore, in the insulation detection device in the embodiments of the present invention, the controller can inject an excitation signal with a preset frequency into the high-voltage electrical circuit of the automation control system through the signal injection circuit.

[0103] Among them, the insulation detection device can be used as an auxiliary device for the high-voltage electrical circuit, and can be connected to the high-voltage electrical circuit for insulation detection when insulation detection is required, and can also be disconnected when insulation detection is not required.

[0104] Based on the above embodiments:

[0105] As an optional embodiment, the signal injection circuit includes a signal amplification circuit module and a resistor-capacitor coupling circuit;

[0106] The signal amplification circuit is connected to the controller, and the signal amplification circuit is used to amplify the amplitude of the excitation signal;

[0107] The resistor-capacitor coupling circuit is respectively connected to the controller, the signal amplification circuit and the high-voltage electrical circuit. The resistor-capacitor coupling circuit is used to filter out the DC bias and transmit the excitation signal of the AC component.

[0108] Specifically, first, considering that the amplitude of the excitation signal output by the controller is small and is easily affected by noise interference during transmission and detection, resulting in a decrease in detection accuracy. Therefore, in the embodiment of the present invention, the amplitude of the excitation signal can be amplified by the signal amplification circuit. The amplified signal has a larger amplitude. In the subsequent sampling process, the signal intensity is relatively stronger than the noise, and it can more accurately reflect the insulation state of the object to be detected, improving the overall signal-to-noise ratio of the insulation detection process. Second, considering that in insulation detection, the DC component may interfere with the detection result and affect the judgment of the insulation state. Therefore, in the embodiment of the present invention, the DC bias can be filtered out by the resistor-capacitor coupling circuit. The capacitor therein can isolate the DC component of the injected sinusoidal excitation signal and only allow the AC component to pass through, while the resistor therein can cooperate with the capacitor to achieve the transmission of the sinusoidal excitation signal.

[0109] As an optional embodiment, the insulation detection circuit further includes a switching switch disposed in the resistor-capacitor coupling circuit. The switching switch is used to close the connection between the high-voltage electrical circuit and the signal injection circuit after obtaining a sampling signal by performing time-domain sampling on the excitation signal injected into the high-voltage electrical circuit.

[0110] Specifically, in order to facilitate injecting the excitation signal into the high-voltage electrical circuit when needed and switching the electrical connection with the high-voltage electrical circuit when not needed, thereby protecting the safety of the monitoring circuit. Therefore, in the embodiment of the present invention, the establishment and disconnection of the electrical connection between the resistor-capacitor coupling circuit and the high-voltage electrical circuit can be achieved through the switching switch.

[0111] As an optional embodiment, the insulation detection circuit further includes a signal conversion circuit disposed between the resistor-capacitor coupling circuit and the controller. The signal conversion circuit is used to adjust the amplitude of the excitation signal in the signal injection circuit within the signal detection range of the controller.

[0112] Specifically, considering that the analog-to-digital converter inside the controller has a certain signal detection range, and the signal amplitude of the excitation signal may exceed this signal detection range. Therefore, in the embodiment of the present invention, the amplitude of the excitation signal at the resistor-capacitor coupling circuit can be adjusted within the signal detection range of the controller through the signal conversion circuit, so as to suppress the common-mode interference and high-frequency noise, make the sampling signal adapt to the input range of the controller's analog-to-digital converter, and improve the sampling accuracy.

[0113] As an optional embodiment, the insulation detection device further includes:

[0114] A filtering circuit connected to the signal injection circuit and the signal conversion circuit respectively, which is used to filter the DC component of the excitation signal in the signal injection circuit, so as to suppress the common-mode interference coupled by the high-voltage electrical circuit.

[0115] Specifically, considering that there may be a DC component (common-mode interference) coupled by the high-voltage electrical circuit in the excitation signal, which affects the signal quality and the final insulation detection accuracy. Therefore, in the embodiments of the present invention, a filtering circuit can be arranged between the signal injection circuit and the signal conversion circuit to filter the DC component of the excitation signal in the signal injection circuit, so as to suppress the common-mode interference coupled by the high-voltage electrical circuit, thereby facilitating the improvement of the insulation detection accuracy.

[0116] As an alternative embodiment, the signal amplification circuit includes a signal amplification circuit with an operational amplifier as the core.

[0117] Specifically, the signal amplification circuit with an operational amplifier as the core has the advantages of simple structure, low cost and high reliability.

[0118] Of course, in addition to the "signal amplification circuit with an operational amplifier as the core", the signal amplification circuit can also be of other types, which are not limited in the embodiments of the present invention.

[0119] For a better description of the embodiments of the present invention, please refer to Figure 3 and Figure 4 , Figure 3 FIG. Figure 4 FIG. Figure 3 In

[0120] Figure 4In it, the resistor-capacitor coupling circuit and the switching switch are generally controlled by a controller to turn on and off the single-pole double-throw relay, so as to inject the sinusoidal excitation signal output by the signal amplification circuit into the high-voltage electrical circuit after resistor-capacitor coupling. Among them, Vin3 and Vin4 are the input terminals of the excitation sinusoidal signal, which are respectively connected to the output terminals Vout1 and Vout2 of the signal amplification circuit; the capacitor C1, capacitor C2, resistor R12 and resistor R13 together form a resistor-capacitor coupling circuit, where the capacitors C1 and C2 are used to isolate the DC component of the injected sinusoidal signal; the resistors R9 to R11, the NPN transistor Q1 and the relay K1 form a sinusoidal excitation signal injection channel, and DO1 is the control port of the controller, which is used to control the on-off state of the sinusoidal excitation signal injection channel; Vout3 and Vout4 are the output terminals of the sinusoidal excitation signal, which are respectively connected to the positive and negative terminals of the high-voltage electrical circuit bus.

[0121] Specifically, for a better description of the embodiments of the present invention, please refer to Figure 5 , Figure 5 which is a schematic structural diagram of a signal conversion circuit provided by the present invention; Figure 5 In it, the signal conversion circuit scales the amplitude of the detected sinusoidal excitation signal and adjusts its DC bias voltage to make it cover the input range of the analog-to-digital converter in the controller as much as possible, increase the sampling dynamic range of the detected signal, and enhance the signal-to-noise ratio of the sampling signal, thereby improving the measurement accuracy of the insulation detection circuit; among them, Vin5 and Vin6 are the input terminals of the sampling signal, which are respectively connected to the output terminals Vout1 and Vout2 of the signal amplification circuit, and are also respectively connected to the input terminals Vin3 and Vin4 of the resistor-capacitor coupling circuit and the switching switch; the capacitors C3 and C4 are used to isolate the DC component of the sampling signal and suppress the common-mode interference (that is, the filtering circuit in the above text) coupled from the high-voltage electrical circuit; the resistors R14 to R21, the capacitors C5, C6, the DC bias voltage Vref3 and the operational amplifiers U3 and U4 form a signal conversion circuit. Among them, the DC bias voltage Vref3 can be taken as half of the reference source voltage of the analog-to-digital converter in the controller, so that the amplified sinusoidal excitation signal can cover the input range of the analog-to-digital converter in the controller as much as possible; the resistors R16 and C5 and the resistors R21 and C6 are used as low-pass filters for the subsequent sampling signal to suppress the high-frequency noise interference in the sampling signal; Vout5 and Vout6 are the output terminals after the sampling signal is converted, which are respectively connected to the differential input terminals of the analog-to-digital converter in the controller.

[0122] The present invention also provides an insulation detection device, which includes the insulation detection circuit and the high-voltage electrical circuit of the automatic control system in the foregoing embodiments.

[0123] For the introduction of the insulation detection device provided by the embodiments of the present invention, please refer to the embodiments of the foregoing insulation detection circuit, and the embodiments of the present invention will not be elaborated herein again.

[0124] The various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. It should also be noted that in this specification, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the element.

[0125] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An insulation detection method, characterized in that: include: Injecting an excitation signal of a preset frequency into a high-voltage electrical circuit of an automation control system, wherein the automation control system uses an energy storage system as an input power source; Performing time domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal; Determining the frequency domain amplitude of the excitation signal of a preset frequency from the sampled signal; According to a preset corresponding relationship, the resistance value of the insulation impedance corresponding to the frequency domain amplitude is determined, wherein the preset corresponding relationship is: the corresponding relationship between the frequency domain amplitude and the insulation impedance.

2. The insulation detection method according to claim 1, characterized in that: The high voltage electrical circuit of the automation control system that injects the excitation signal of the preset frequency includes: An excitation signal of a preset frequency is output, and after the excitation signal is amplitude amplified and the DC bias is removed, the AC component of the excitation signal is injected into the high-voltage electrical circuit.

3. The insulation detection method according to claim 1, characterized in that: After performing time domain sampling on the excitation signal injected into the high-voltage electrical circuit to obtain a sampling signal, the method further includes: After stopping injecting the excitation signal of the preset frequency into the high-voltage electrical circuit of the automation control system, the frequency domain amplitude of the excitation signal of the preset frequency is determined from the sampled signal.

4. The insulation detection method according to claim 1, characterized in that: Determining the frequency domain amplitude of the excitation signal of the preset frequency from the sampled signal includes: Inputting the sampled signal into a frequency domain amplitude calculation model to obtain a frequency domain amplitude of an excitation signal of a preset frequency in the sampled signal; Among them, the frequency domain amplitude calculation model is constructed based on the Fourier transform forward transform method, and the frequency domain amplitude calculation model has pre-calculated real coefficients and imaginary coefficients of discrete Fourier transform forward transform.

5. The insulation detection method according to any one of claims 1 to 4, characterized in that: The excitation signal includes two mutually differential sinusoidal signals.

6. An insulation detection circuit, characterized in that: include: A controller, used to implement the steps of the insulation detection method according to any one of claims 1 to 5; A signal injection circuit is connected to the high voltage electrical circuit of the controller and the automation control system respectively.

7. The insulation detection circuit according to claim 6, characterized in that: The signal injection circuit includes a signal amplification circuit module and a resistance-capacitance coupling circuit; The signal amplifying circuit is connected to the controller, and the signal amplifying circuit is used to amplify the amplitude of the excitation signal; The RC coupling circuit is respectively connected to the controller, the signal amplifying circuit and the high-voltage electrical circuit, and is used for filtering out the DC bias and transmitting the excitation signal of the AC component.

8. The insulation detection circuit according to claim 7, characterized in that: It also includes a switching switch arranged in the RC coupling circuit, and the switching switch is used to close the connection between the high-voltage electrical circuit and the signal injection circuit after completing the time domain sampling of the excitation signal injected into the high-voltage electrical circuit to obtain the sampling signal.

9. The insulation detection circuit according to claim 7, characterized in that: It also includes a signal conversion circuit arranged between the RC coupling circuit and the controller, and the signal conversion circuit is used to adjust the amplitude of the excitation signal in the signal injection circuit to within the signal detection range of the controller.

10. An insulation detection device, characterized in that: include: The high-voltage electrical circuit of the insulation detection circuit and the automatic control system as described in any one of Rights 6-9.

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