Direct current insulation resistance detection method and detection device

Abstract

The present application relates to a kind of direct current insulation resistance detection method and detection device.The method is by establishing the mathematical model of the insulation resistance of the DC bus to be measured and bus voltage, when not accessing the positive bridge arm and negative bridge arm of unbalanced bridge, and when accessing the negative bridge arm of unbalanced bridge, the positive and negative bus voltage to ground value is collected, and the noise influence is introduced, based on the above-mentioned measured values collected, the calculation method for eliminating the noise influence is created, the iteration calculation is obtained, and the parameter θ to be identified is obtained.The insulation resistance value of the DC system to be measured is solved by substituting θ into mathematical model.The method fully considers the environmental noise and the pulse noise caused by the switching of circuit switch during the test, thereby reducing the insulation resistance detection error of the DC system to be measured, and improving the reliability of detection result.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system insulation detection, and in particular to a direct current insulation resistance detection method and a detection device. BACKGROUND

[0002] With the increasing complexity of modern power systems and the increasing demand for high reliability, insulation monitoring of direct current systems plays a crucial role in ensuring equipment safety, extending service life, and preventing equipment failure. The health status of the insulation system directly affects the stable operation and safety of the equipment, especially in key fields such as power transmission, rail transportation, and communication. Accurate monitoring and diagnosis techniques are particularly important for insulation problems in direct current systems.

[0003] Currently, insulation detection of direct current systems mainly relies on a structure combining balanced bridges and unbalanced bridges. The balanced bridge is used to clamp the positive and negative bus voltages to ground, and to control the fluctuation range of the bus voltage during the switching process of the unbalanced bridge. The main function of the unbalanced bridge is to form a bus voltage fluctuation by switching the bridge arm, and to calculate the direct current bus insulation resistance by circuit analysis and solution of the voltage fluctuation. For example, the Chinese patent application for invention with publication number CN112540226A, "Unbalanced bridge insulation resistance detection circuit and calculation method for rail transit", realizes the switching of the unbalanced bridge resistance through a single control switch, uses a sampling circuit and a signal conditioning circuit to collect voltage signals, and finally calculates the insulation resistance through Ohm's law and Kirchhoff's voltage and current laws. However, this method does not consider the environmental noise that exists universally during the measurement process, nor does it consider the pulse noise caused by the switching of the circuit switch, resulting in a large error in the calculation of the insulation resistance. SUMMARY

[0004] The technical problem to be solved by the present application is how to reduce the error in the detection of direct current insulation resistance.

[0005] The present application solves the above technical problems by the following technical means:

[0006] The present application provides a direct current insulation resistance detection method, which comprises the following steps:

[0007] S1, when the positive bridge arm and the negative bridge arm of the unbalanced bridge are not connected, the mathematical model of the insulation resistance of the bus to be measured and the bus voltage is: where U p1 is the positive bus voltage to ground, U n1 is the negative bus voltage to ground; R b is the voltage clamping balanced bridge resistance value, R x is the insulation resistance value of the positive bus to be measured, and R y is the insulation resistance value of the negative bus to be measured.

[0008] S2. When establishing the connection to the negative arm of the unbalanced bridge, the mathematical model for the insulation resistance of the busbar to be measured and the busbar voltage is as follows:

[0009] Among them, U p2 This is the voltage of the positive busbar to ground at this time, U n2 This is the voltage of the negative busbar to ground at this time; R bn The equivalent resistance values ​​of the voltage clamping balanced bridge and unbalanced bridge are calculated using the formula R. bn =R b R n / (R b +R n ), where R n The resistance value of the unbalanced bridge;

[0010] S3. Without connecting the positive and negative arms of the unbalanced bridge, measure the voltage of the positive and negative busbars to ground n times, and record them as follows:

[0011] U p1 =[u p1 (1),...,u p1 (i),...,u p1 (n)] T U n1 =[u n1 (1),...,u n1 (i),...,u n1 (n)] T ;That

[0012] in, u p1 (i) represents the positive busbar-to-ground voltage during the i-th measurement, u n1 (i) represents the negative busbar voltage to ground during the i-th measurement;

[0013] S4. When connecting the negative arm of the unbalanced bridge, measure the voltage to ground of the positive busbar and negative busbar n times, and record them as U. p2 =[u p2 (1),...,u p2 (i),...,u p2 (n)] T U n2 =[u n2 (1),...,u n2 (i),...,u n2 (n)] T ; where u p2 (i) represents the positive busbar-to-ground voltage during the i-th measurement, u n2 (i) represents the negative busbar voltage to ground during the i-th measurement;

[0014] S5, the matrix obtained in step S4 and step S5 is augmented to obtain the following formula:

[0015] U y =U x θ, wherein U y =(U p1 U p2 ) T , θ=(θ1θ2) T , θ

[0016] is a to-be-identified parameter matrix, wherein,

[0017] S6, based on the voltage data obtained in step S4 and step S5, and based on the initial parameters set by the standard deviation weighted recursive least squares method, the to-be-identified parameters θ are iteratively calculated while considering the noise factor, and the to-be-identified parameters θ are updated;

[0018] S7, the positive and negative bus insulation resistance values of the direct current system to be measured are calculated by the to-be-identified parameters θ1 and θ2.

[0019] Further, the initial parameters in step S6 include: the to-be-identified parameters θ, the covariance matrix P, the adaptive weight factor W, the forgetting factor λ, and the adjustment factor μ.

[0020] Further, the step S6 includes the following steps:

[0021] S61, the augmented input matrix U is generated using the i-th measurement data; y (i)=(u p1 (i) u p2 (i)) T , the model prediction error e(i) is calculated;

[0022] S62, the adaptive weight factor W based on the measurement data standard deviation is calculated;

[0023] S63, the gain factor K is calculated;

[0024] S64, the covariance matrix P is calculated;

[0025] S65, the to-be-identified parameters θ are calculated;

[0026] S66, if the measurement is stopped, the to-be-identified parameter matrix θ is output, and step S7 is continued to be executed; if the measurement continues, the measurement data is updated, and the iteration calculation is continued in step S61.

[0027] Further, the specific calculation formula of the model prediction error is:

[0028] e(i) = U y (i) - U x (i) θ.

[0029] Further, the adaptive weight factor is:

[0030] The calculation formula is:

[0031]

[0032] wherein, is the standard deviation of the ith measurement data and the historical data mean; is the historical data mean; a = n, p; j = 1, 2; μ is an adjustment factor.

[0033] Further, the specific calculation formula of the gain factor K is:

[0034] wherein λ is a forgetting factor.

[0035] Further, the specific calculation formula of the covariance matrix P is:

[0036] Further, the specific update formula of the to-be-identified parameter θ is: θ = θ + Ke(i).

[0037] Further, the step S7 is specifically:

[0038] The to-be-identified parameters θ1 and θ2 obtained in step S6 and the to-be-measured positive and negative bus insulating resistances R x and R y are combined to obtain the to-be-measured negative bus insulating resistance value calculation formula:

[0039] R y = (θ1- θ2) R bn R b / (θ2 R bn - θ1 R b );

[0040] The to-be-measured positive insulating resistance value calculation formula is:

[0041] R x = R by θ1 R b / (R b - R by θ1);

[0042] wherein R by is the equivalent resistance obtained by connecting the voltage clamping balance bridge resistance and the to-be-measured negative insulating resistance in parallel, and the resistance value calculation formula is: R by= R b R y (R b + R y ).

[0043] The application also provides a direct current insulation resistance detection device, which detects the insulation resistance of a direct current system according to the above method and comprises the following modules.

[0044] A master control MCU module comprising a built-in memory and a chip, which is used to execute the direct current insulation resistance detection method in any of the above schemes and calculate the insulation resistance value of the direct current system to be detected.

[0045] A balanced bridge unbalanced bridge module, which is used to collect the voltage values of the positive bus and the negative bus to ground when the non-balanced bridge positive bridge arm and the negative bridge arm are not connected and when the non-balanced bridge negative bridge arm is connected.

[0046] An AD analog-digital conversion module, which is used to convert the collected analog voltage signals into digital signals and input the digital signals into the master control MCU module.

[0047] The application has the following advantages.

[0048] The application fully considers the environmental noise and the pulse noise caused by the switching of the circuit in the measurement process, creates a calculation method for reducing the influence of noise, reduces the direct current insulation resistance detection error through the iterative calculation method, and obtains more stable insulation resistance value results through multiple measurements of the direct current system to be detected, that is, the data reliability of single test is stronger. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a direct current insulation resistance detection method flowchart of an embodiment of the application;

[0050] Figure 2 is a sub-step flowchart of step S6 of the direct current insulation resistance detection method of an embodiment of the application;

[0051] Figure 3 is a simulation result comparison diagram of an embodiment of the application and a traditional ohm method detection method;

[0052] Figure 4 is a simulation result comparison diagram of an embodiment of the application and a traditional least square method detection method; DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1

[0055] like Figure 1 As shown, this invention provides a DC insulation resistance detection method. This method calculates the insulation resistance of positive and negative busbars based on the standard deviation weighted recursive least squares method, and includes the following steps:

[0056] S1. When the positive and negative arms of the unbalanced bridge are not connected, the mathematical model for the insulation resistance and voltage of the busbar under test is as follows: Among them, U p1 U is the positive bus voltage to ground. n1 This is the negative busbar voltage to ground. R b R is the resistance value of the voltage clamping balance bridge. x R is the insulation resistance value of the positive busbar to be tested. y The value of the insulation resistance of the negative busbar to be tested;

[0057] S2. When establishing the connection to the negative arm of the unbalanced bridge, the mathematical model for the insulation resistance of the busbar to be measured and the busbar voltage is as follows:

[0058] Among them, U p2 This is the voltage of the positive busbar to ground at this time, U n2 This is the voltage of the negative busbar to ground at this time; R bn The equivalent resistance values ​​of the voltage clamping balanced bridge and unbalanced bridge are calculated using the formula R. bn =R b R n / (R b +R n ), where R n The resistance value of the unbalanced bridge;

[0059] S3. Without connecting the positive and negative arms of the unbalanced bridge, measure the voltage of the positive and negative busbars to ground n times, and record them as follows:

[0060] U p1 =[u p1 (1),...,u p1 (i),...,u p1 (n)] T U n1 =[un1 (1),...,u n1 (i),...,u n1 (n)] T ;That

[0061] in, u p1 (i) represents the positive busbar-to-ground voltage during the i-th measurement, u n1 (i) represents the negative busbar voltage to ground during the i-th measurement;

[0062] S4. When connecting the negative arm of the unbalanced bridge, measure the voltage to ground of the positive busbar and negative busbar n times, and record them as U. p2 =[u p2 (1),...,u p2 (i),...,u p2 (n)] T U n2 =[u n2 (1),...,u n2 (i),...,u n2 (n)] T ; where u p2 (i) represents the positive busbar-to-ground voltage during the i-th measurement, u n2 (i) represents the negative busbar voltage to ground during the i-th measurement;

[0063] S5. Augment and combine the matrices obtained in steps S4 and S5 to obtain the following formula:

[0064] U y =U x θ, where, U y =(U p1 U p2 ) T , θ=(θ1θ2) T θ

[0065] Let be the parameter matrix to be identified, where,

[0066] S6. Based on the voltage data obtained in steps S4 and S5, and using the standard deviation weighted recursive least squares method to set initial parameters, while considering noise factors to perform iterative calculations and update the parameters to be identified θ.

[0067] The initial parameters mentioned in step S6 include: the parameter to be identified θ, the covariance matrix P, the adaptive weighting factor W, the forgetting factor λ, and the adjustment factor μ.

[0068] S7. Calculate the insulation resistance values ​​of the positive and negative busbars of the DC system under test using the parameters to be identified, θ1 and θ2.

[0069] likeFigure 2 As shown, the step S6 includes the following steps:

[0070] S61, generating an augmented input matrix with the i-th measurement data Output matrix U y (i) = (u p1 (i) u p2 (i)) T , calculating the model prediction error e(i);

[0071] S62, calculating the update adaptive weight factor W based on the measurement data standard deviation; this step fully considers the environmental noise and impulse noise caused by the switching of circuit switches in the measurement process.

[0072] S63, calculating the update gain factor K;

[0073] S64, calculating the update covariance matrix P;

[0074] S65, calculating the update to-be-identified parameter θ;

[0075] S66, if the measurement stops, output the to-be-identified parameter matrix θ, and continue to execute step S7; if the measurement continues, update the measurement data and return to step S61 to continue the iterative calculation.

[0076] The specific calculation formula of the model prediction error is:

[0077] e(i) = U y (i) - U x (i) θ

[0078] The adaptive weight factor is:

[0079] The calculation formula is:

[0080]

[0081] Wherein, is the standard deviation of the i-th measurement data and the historical data mean. is the historical data mean; a = n, p. j = 1, 2; μ is the adjustment factor;

[0082] The specific calculation formula of the gain factor K is: Wherein λ is the forgetting factor.

[0083] The specific calculation formula of the covariance matrix P is:

[0084] The specific update formula of the to-be-identified parameter θ is: θ = θ + Ke(i).

[0085] The step S7 is specifically:

[0086] The to-be-identified parameters θ1 and θ2 obtained in step S6 are combined with the to-be-measured positive and negative bus insulating resistances R x , R y , and the mathematical relationship is solved to obtain the to-be-measured negative bus insulating resistance value calculation formula:

[0087] R y = (θ1-θ2)R bn R b / (θ2R bn -θ1R b );

[0088] The to-be-measured positive insulating resistance value calculation formula is:

[0089] R x =R by θ1R b / (R b -R by θ1);

[0090] wherein R by is the equivalent resistance obtained by connecting the voltage clamping balance bridge resistance and the to-be-measured negative insulating resistance in parallel, and the resistance value calculation formula is: R by =R b R y / (R b +R y )。

[0091] In order to verify the effectiveness of the present application, an example is simulated. In this example, the DC insulating resistance detection method simulation and the applied noise parameters are shown in Table 1:

[0092] Table 1

[0093]

[0094]

[0095] In this example, the initial parameter setting of the standard deviation weighted recursive least square method is shown in Table 2:

[0096] Table 2

[0097]

[0098] During the simulation, different random seeds for white noise and impulse noise were applied each time, and the intensity of the impulse noise varied to increase the diversity of the experiments and thus verify the robustness of the algorithm. Following the parameters in Tables 1 and 2, a total of 20 experiments were conducted using the detection method described in this embodiment, and the detection results were compared with those based on other algorithms.

[0099] like Figure 3 As shown in the simulation results, the root mean square error of the positive and negative insulation resistance based on the traditional ohmmeter method is 3.83 and 4.32, respectively. Figure 4 As shown, the detection method based on the traditional least squares method has a root mean square error of 3.90 and 4.40 for positive and negative insulation resistance, respectively. The detection method in this embodiment has root mean square errors of 1.76 and 2.03 for positive and negative insulation resistance, respectively.

[0100] The data from 20 comparative experiments are shown in the table below:

[0101] Table comparing the results of the Ohm method and this method.

[0102]

[0103]

[0104]

[0105] Table comparing the results of least squares method and this method.

[0106]

[0107]

[0108]

[0109] As can be seen from the comparison figures, the resistance value obtained by the DC system insulation resistance detection method of the present invention is less affected by noise interference, which improves the calculation accuracy. Moreover, the fluctuation of the insulation resistance calculation results in multiple experiments is much smaller than that of the traditional Ohm method and the least squares method, and it has higher stability.

[0110] Example 2

[0111] It should be further explained that, based on the same inventive concept, the present invention also provides a DC insulation resistance detection device, which performs the detection of DC system insulation resistance according to the method described in Embodiment 1, including:

[0112] The main control MCU module, including built-in memory and chip, is used to execute the DC insulation resistance detection method described in Embodiment 1 and calculate the insulation resistance value of the DC system under test.

[0113] The balanced bridge and the unbalanced bridge module, the balanced bridge part is used for clamping the bus voltage to ground voltage, and ensures that the bus voltage fluctuation is within the allowable range when the unbalanced bridge part works; the module is used for collecting the positive and negative bus voltage to ground voltage value when the positive and negative bridge arms of the unbalanced bridge are not connected and when the negative bridge arm of the unbalanced bridge is connected;

[0114] The AD analog-digital conversion module is used for converting the collected analog voltage signal into a digital signal input into the main control MCU module.

[0115] The above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A direct current insulation resistance detection method characterized by, Comprising the following steps: S1, when establishing the non-access unbalanced bridge positive bridge arm and negative bridge arm, the mathematical model of the busbar insulation resistance and busbar voltage is: Wherein, U p1 is the positive bus voltage to ground, U n1 is the negative bus voltage to ground; R b is the voltage clamping balance bridge resistance value, R x is the measured positive bus insulation resistance value, R y is the measured negative bus insulation resistance value; S2, when the access non-balance bridge negative bridge arm is established, the mathematical model of the bus insulation resistance and the bus voltage is: wherein U p2 is the voltage of the positive busbar to ground at this time, U n2 is the voltage of the negative busbar to ground at this time; R bn is the equivalent resistance value of the voltage clamping balanced bridge and the unbalanced bridge, and the calculation formula is R bn = R b R n / (R b + R n ), wherein R n is the resistance value of the unbalanced bridge; S3, when the non-balance bridge positive bridge arm and the negative bridge arm are not accessed, the n times positive bus and negative bus voltage to ground is measured, and is recorded as U p1 = [u p1 (1),...,u p1 (i),...,u p1 (n)] T , U n1 = [u n1 (1),...,u n1 (i),...,u n1 (n)] T ; wherein u p1 (i) is the positive bus voltage to ground at the i-th measurement, u n1 (i) is the negative bus voltage to ground at the i-th measurement; S4, when accessing the unbalanced bridge negative bridge arm, measuring n times of positive bus and negative bus voltage to ground, respectively recorded as U p2 = [u p2 (1),...,u p2 (i),...,u p2 (n)] T , U n2 = [u n2 (1),...,u n2 (i),...,u n2 (n)] T ; wherein, u p2 (i) is the positive bus voltage to ground at the ith time of measurement, u n2 (i) is the negative bus voltage to ground at the ith time of measurement; S5, the matrix obtained by combining step S4 and step S5 is augmented, and the following formula is obtained: U y = U x θ, where U y = (U p1 U p2 ) T , θ = (θ1 θ2) T , θ is a parameter matrix to be identified, where, S6, based on the voltage data obtained by step S4 and step S5, and based on the initial parameters set by the weighted recursive least square method, the noise factor is considered for iterative calculation, and the to-be-identified parameter matrix θ is updated; S7, the positive and negative bus insulation resistance values of the to-be-measured DC system are calculated by the to-be-identified parameters θ1 and θ2.

2. The direct current insulation resistance detection method according to claim 1, characterized by, The initial parameters in step S6 include: the to-be-identified parameter matrix θ, the covariance matrix P, the adaptive weight factor W, the forgetting factor λ, and the adjustment factor μ.

3. The method of claim 1, wherein the DC insulation resistance is detected by applying a voltage of 1.5 V to 3 V to the DC insulation resistance detection terminal of the electronic device and measuring a current flowing through the DC insulation resistance detection terminal. The step S6 includes the following steps: S61, generate an augmented input matrix with the i-th measurement data output matrix U y (i) = (u p1 (i)u p2 (i)) T , calculate the model prediction error e(i); S62, the adaptive weight factor W based on the measurement data standard deviation is calculated and updated; S63, the gain factor K is calculated and updated; S64, the covariance matrix P is calculated and updated; S65, the to-be-identified parameter matrix θ is calculated and updated; S66, if the measurement stops, the to-be-identified parameter matrix θ is output, and step S7 is continued to be executed; if the measurement continues, the measurement data is updated, and step S61 is returned to continue the iterative calculation.

4. The direct current insulation resistance detection method according to claim 3, characterized in that, The specific calculation formula of the model prediction error is: e(i) = U y (i) - U x (i) θ.

5. The direct current insulation resistance detection method according to claim 3, characterized in that, The adaptive weight factor is: The calculation formula is: wherein, is the standard deviation of the ith measurement data from the historical data mean; is the historical data mean; a = n, p; j = 1, 2; μ is an adjustment factor.

6. The direct current insulation resistance detection method according to claim 3, wherein The specific calculation formula of the gain factor K is: where λ is a forgetting factor.

7. The method of claim 6, wherein the DC insulation resistance is detected by applying a voltage of 1.5 V to 3 V to the DC insulation resistance detection terminal of the electronic device and measuring a current flowing through the DC insulation resistance detection terminal. The specific formula for calculating the covariance matrix P is:

8. The method of claim 6, wherein the DC insulation resistance is detected by applying a voltage of 1.5 V to 3 V to the DC insulation resistance detection terminal of the electronic device and measuring a current flowing through the DC insulation resistance detection terminal. The specific update formula of the to-be-identified parameter matrix θ is: θ=θ+Ke(i).

9. The method of claim 1, wherein the DC insulation resistance is detected by applying a voltage of 1.5 V to 3 V to the DC insulation resistance detection terminal of the electronic device and measuring a current flowing through the DC insulation resistance detection terminal. The step S7 is specifically: The to-be-identified parameters θ1, θ2 obtained in step S6 are combined with the to-be-measured positive and negative bus insulating resistances R x , R y Mathematical relationship formula is solved, and the to-be-measured negative bus insulating resistance value calculation formula is: R y = (θ1- θ2)R bn R b / (θ2R bn -θ1R b ); The calculation formula of the to-be-measured positive insulation resistance is: R x = R by θ1R b / (R b -R by θ1); Wherein, R by is the equivalent resistance obtained by connecting the voltage clamping balance bridge resistance and the to-be-measured negative electrode insulation resistance in parallel, and the resistance calculation formula is: R by = R b R y / (R b + R y ).

10. A direct current insulation resistance detecting device characterized by comprising: The device comprises: A main control MCU module comprising a built-in memory and a chip, used for executing the DC insulation resistance detection method according to claims 1-9, and calculating the insulation resistance value of the to-be-measured DC system; A balanced bridge and non-balance bridge module, the balanced bridge part is used for clamping the bus voltage to ground, and ensures that the bus voltage fluctuation is within the allowable range when the non-balance bridge part works; the module is used for collecting the positive and negative bus voltages to ground when the non-balance bridge positive bridge arm and the negative bridge arm are not accessed, and the positive and negative bus voltages to ground when the non-balance bridge negative bridge arm is accessed; An AD analog-to-digital conversion module, used for converting the collected analog voltage signal into a digital signal input into the main control MCU module.

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