Direct current system insulation detection method and portable insulation detection and verification integrated device

Abstract

The application discloses a DC system insulation detection method and a portable insulation detection and verification integrated device, and the method comprises the following steps: constructing a DC system bus insulation detection circuit, and establishing a mathematical model of bus voltage and bus insulation resistance; detection switches K4 and K12 are arranged in the bus insulation detection circuit; balance bridge switches K5, K13, K6 and K14 are arranged; K4, K12, K5, K13 and K6 are closed, and K14 is opened, and the positive and negative bus voltages to the ground are measured; after each measurement, the regularization data reuse recursive least square method is used to update the to-be-identified parameters; the states of the remaining switches remain unchanged, K6 is opened, K14 is closed, and the positive and negative bus voltages to the ground are measured; after each measurement, the regularization data reuse recursive least square method is used to update the to-be-identified parameters; and the to-be-identified parameters are combined with the mathematical model to calculate the positive and negative bus insulation resistance values, and the accuracy of bus insulation resistance measurement is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system insulation detection, in particular to a DC system insulation detection method and a portable insulation detection and verification integrated device. BACKGROUND

[0002] In modern power systems, DC power supply systems are increasingly widely used, especially in renewable energy, rail transportation and energy storage systems. The positive and negative busbars of the DC system are an important part of power transmission, and their insulation performance directly affects the safety and reliability of the system. With the increase of voltage level and the increase of equipment integration, the calculation and monitoring of insulation resistance becomes particularly important.

[0003] Currently, busbar insulation detection mainly relies on the structure combined by balanced bridge and unbalanced bridge. The balanced bridge is used to clamp the positive and negative busbar voltage to ground, and to control the fluctuation range of the busbar voltage during the switching process of the unbalanced bridge. The main function of the unbalanced bridge is to form busbar voltage fluctuation by switching the bridge arm, and to calculate the DC busbar insulation resistance by circuit analysis of voltage fluctuation. For example:

[0004] 1) Document 1 "Liu Bingjie. Research on DC busbar grounding insulation detection method [J]. Power and energy, 2018, 39(02):209-211." first analyzes the insulation detection circuit before and after the switching of the unbalanced bridge arm, and obtains two mathematical relationship formulas between the positive and negative busbar insulation resistance and the positive and negative busbar voltage before and after the switching of the bridge arm. Then, the two relationship formulas are solved to obtain the positive and negative busbar insulation resistance. However, this method only considers the ideal case of busbar voltage, and does not analyze the white noise and impulse noise existing in the busbar voltage and its measurement process, resulting in deviation in the calculation result.

[0005] 2) Document 2 "Zhang Wei, Chu Jianxin, Song Weihao. Hybrid power system DC grid insulation resistance measurement error compensation [J]. Instrument technology and sensor, 2017(8):106-109." first analyzes and models the insulation detection circuit before and after the switching of the unbalanced bridge arm, then collects multiple data before and after the switching, and uses the data set to identify the model parameters using the least squares method, and then calculates the positive and negative busbar insulation resistance through the identified parameters. However, this method requires collecting and storing a large amount of data, and the calculation of insulation resistance is not accurate if the data collected is small, and online detection cannot be performed.

[0006] 3) Document 3, a utility model patent with patent publication number CN211698045U, discloses an electrical circuit insulation detection auxiliary device. The device designs an electrical circuit insulation detection auxiliary device, which consists of an outer shell, a circuit board, a main control chip, a power supply, a power line detector, an acoustic emission detector, a thermal radiation detector, an electromagnetic emission detector, a signal converter, an alarm device and multiple signal monitoring connecting wires. However, the device has many external wiring wires and is not easy to carry. During the detection, there are phenomena such as forgetting to bring wires or losing wires, and it lacks self-calibration capability and cannot verify the impact of its own system errors and component aging on the measurement process.

[0007] In summary, the prior art has the following deficiencies:

[0008] 1) Failure to consider the white noise and pulse noise in the bus voltage and its measurement process leads to deviations in the calculation results of the bus insulation resistance;

[0009] 2) Using the least squares method to perform parameter identification and calculation to obtain the busbar insulation resistance requires a large amount of data and cannot be detected online.

[0010] 3) The insulation detection device is not easy to carry, has many wires, lacks self-calibration capabilities, and cannot verify the impact of its own system errors and component aging on the measurement process. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a novel DC system busbar insulation resistance calculation method which is less affected by noise interference, requires less measurement data and can perform online detection.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0013] A DC system insulation detection method, comprising:

[0014] S10, constructing a DC system busbar insulation detection circuit and establishing a mathematical model of busbar voltage and busbar insulation resistance;

[0015] The busbar insulation detection circuit includes a busbar voltage detection circuit and a balanced bridge / unbalanced bridge control circuit. The busbar voltage detection circuit is provided with detection switches K4 and K12. The two ends of the detection switch K4 are connected to the busbar positive electrode and the ground wire, respectively, and the two ends of the detection switch K12 are connected to the ground wire and the busbar negative electrode, respectively. The balanced bridge / unbalanced bridge control circuit includes balanced bridge switches K5 and K13, and unbalanced bridge switches K6 and K14. The two ends of the balanced bridge switch K5 and the unbalanced bridge switch K6 are connected to the busbar positive electrode and the ground wire, respectively, and the two ends of the balanced bridge switch K13 and the unbalanced bridge switch K14 are connected to the ground wire and the busbar negative electrode, respectively.

[0016] S20, close detection switches K4, K12, balance bridge switches K5, K13, unbalance bridge switch K6, open unbalance bridge switch K14, measure positive and negative bus voltage to ground;

[0017] S30, after measuring positive and negative bus voltage to ground each time, update to-be-identified parameter θ1 by regularized data reuse recursive least square method;

[0018] S40, keep the rest switch states unchanged, open unbalance bridge switch K6, close switch K14, measure positive and negative bus voltage to ground;

[0019] S50, after measuring positive and negative bus voltage to ground each time, update to-be-identified parameter θ2 by regularized data reuse recursive least square method;

[0020] S60, calculate positive and negative bus insulation resistance values by to-be-identified parameters θ1, θ2, in combination with the mathematical model of bus voltage and bus insulation resistance.

[0021] In an embodiment of the present application, the mathematical model of bus voltage and bus insulation resistance comprises:

[0022] When detection switches K4, K12, balance bridge switches K5, K13, unbalance bridge switch K6 are closed and unbalance bridge switch K14 is opened, the mathematical model of bus voltage and bus insulation resistance is as follows:

[0023] Let

[0024] In the formula, U p1 is positive bus voltage to ground under the condition of step S20, U n1 is negative bus voltage to ground under the condition of step S20; K is the resistance ratio of detection switch route, and is recorded as K=(R1+R2) / (R6+R 10 ), R4 is the resistance value of positive unbalance bridge resistance in bus voltage detection circuit, R p3 is the equivalent parallel resistance value of to-be-calculated positive bus insulation resistance R p and balance bridge resistance R3, and is recorded as R p3 =R p R3 / (R p +R3), R n7 is the equivalent parallel resistance value of to-be-calculated negative bus insulation resistance R n and balance bridge resistance R7, and is recorded as R n7 =R n R7 / (R n +R7)R n7 .

[0025] In one embodiment of the present invention, establishing a mathematical model of bus voltage and bus insulation resistance includes:

[0026] When the detection switches K4 and K12, the balancing bridge switches K5 and K13 are closed, the unbalanced bridge switch K6 is opened, and the unbalanced bridge switch K14 is closed, the mathematical model of the bus voltage and bus insulation resistance is as follows:

[0027] remember

[0028] Where U p2 is the positive bus voltage to ground under the conditions of step S40, U n2 is the voltage between the negative busbar and the ground under the condition of step S40, R8 is the resistance value of the negative unbalanced bridge resistor; K is the resistance ratio of the detection switch line, which is recorded as K = (R1 + R2) / (R6 + R 10 ), R4 is the positive unbalanced bridge resistance in the bus voltage detection circuit, R p3 The positive busbar insulation resistance R to be calculated p The equivalent parallel resistance of the balanced bridge resistor R3 is denoted as R p3 =R p R3 / (R p +R3), R n7 The negative busbar insulation resistance R to be calculated n The equivalent parallel resistance of the balanced bridge resistor R7 is denoted as R n7 =R n R7 / (R n +R7)R n7 .

[0029] In one embodiment of the present invention, in step S20, measuring the positive and negative bus voltages to ground includes:

[0030] Disconnect the unbalanced bridge switch K6, close the unbalanced bridge switch K14, and measure the voltage of the positive and negative poles of the busbar to the ground at each moment, which are 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 Among them, 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; and T represents the matrix transpose; and n is the maximum number of measurements.

[0031] In one embodiment of the present invention, in step S30, the parameter to be identified θ1 is updated by using the regularized data reuse recursive least squares method, including:

[0032] S31, calculate the prediction error e1(i);

[0033] After the i-th measurement, the positive bus voltage to ground u p1 (i) As a reference output, the negative bus voltage to ground u n1 (i) as input, calculate the model prediction error e1(i), where e1(i) = u p1 (i)-θ1(i-1)u n1 (i); where θ1(i-1) represents the parameter θ1 to be identified during the i-1th measurement;

[0034] S32, update gain factor K1, covariance matrix P1, data reuse parameters α1, β1, bus voltage mean and regularization term L1;

[0035] The gain factor calculation formula is: Where λ is the forgetting factor;

[0036] The formula for calculating the covariance matrix is:

[0037] The data reuse parameter calculation formula is: β1=(1-α1 m ) / (1-α1); where m is the number of data reuses;

[0038] The calculation formula for the bus voltage mean is:

[0039] The regularization term calculation formula is: Among them, μ1 is the regularization term adjustment coefficient;

[0040] S33, update the parameter to be identified θ1(i);

[0041] The update formula of the parameters to be identified is: θ1(i)=θ1(i-1)+L1K1β1e1(i);

[0042] S34, repeat steps S31 to S33 until the measurement is stopped.

[0043] In one embodiment of the present invention, in step S40, measuring the positive and negative bus voltages to ground includes:

[0044] The closing detection switch K4, K12, the balance bridge switch K5, K13, the opening unbalance bridge switch K6, the closing unbalance bridge switch K14, the measurement of the positive bus voltage and the negative bus voltage at each time is 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 i-th measurement, u n2 (i) is the negative bus voltage to ground at the i-th measurement; T represents the matrix transpose; n is the maximum number of measurements.

[0045] In an embodiment of the application, in step S50, the to-be-identified parameter θ2 is updated by the regularized data reuse recursive least square method, comprising:

[0046] S51, calculating the prediction error e2(i);

[0047] After the i-th measurement, the positive bus voltage to ground u p2 (i) is taken as a reference output, the negative bus voltage to ground u n2 (i) is taken as an input, and the model prediction error e2(i) is calculated, wherein e2(i) = u p2 (i)-θ2(i-1)u n2 (i); wherein θ2(i-1) represents the to-be-identified parameter θ2 at the i-1-th measurement;

[0048] S52, updating the gain factor K2, the covariance matrix P2, the data reuse parameters α2, β2, and the bus voltage mean and the regularization term L2;

[0049] The gain factor calculation formula is: Wherein λ is a forgetting factor;

[0050] The covariance matrix calculation formula is:

[0051] The data reuse parameter calculation formula is: β2= (1-α2 m ) / (1-α2); wherein m is the data reuse number;

[0052] The bus voltage mean calculation formula is:

[0053]

[0054] The regular term calculation formula is: Wherein, μ2 is a regular term adjustment coefficient;

[0055] S53, updating the to-be-identified parameter θ2(i);

[0056] The to-be-identified parameter updating formula is: θ2(i) = θ2(i-1) + L2K2β2e2(i);

[0057] S54, repeating steps S51 to S53 until stopping measurement.

[0058] In an embodiment of the present application, in step S60, the positive and negative busbar insulation resistance values are calculated by the following formula:

[0059] The to-be-identified parameters θ1 and θ2 obtained in step S10 are combined with the equivalent resistance R p3 , R n7 of the positive and negative busbar insulation resistance and the balance bridge resistance to obtain the mathematical relationship formula, and then the positive busbar insulation resistance value calculation formula is R p = R p3 R3 / (R3-R p3 ), and the negative busbar insulation resistance value calculation formula is R n = R n7 R7 / (R7-R n7 ); wherein, R3 and R7 are two series balance bridge resistances, the two ends of R3 are connected with the positive busbar and the grounding wire respectively, and the two ends of R7 are connected with the grounding wire and the negative busbar respectively.

[0060] The present application also provides a portable DC system insulation detection and verification integrated device, comprising: a handheld meter, a leakage current collector and a verification and detection host; the leakage current collector and the verification and detection host are respectively wirelessly connected with the handheld meter;

[0061] The handheld meter is used for visualization and display of data obtained from the leakage current collector and the verification and detection host.

[0062] The leakage current collector is used for measurement of leakage current data.

[0063] The verification and detection host is used for measurement of busbar data and integration of the above-mentioned DC system insulation detection method.

[0064] In an embodiment of the present application, the verification and detection host further integrates an analog grounding resistance circuit, an AC series detection circuit and a detection signal source circuit; wherein,

[0065] The simulated grounding resistance circuit includes switches K1, K2, K3, K9, K10, and K11, and resistors R11, R12, R13, R14, R15, and R16; the switch K1 is connected in series with the resistor R11 to form a first simulated branch; the switch K2 is connected in series with the resistor R12 to form a second simulated branch; the switch K3 is connected in series with the resistor R13 to form a third simulated branch; the switch K9 is connected in series with the resistor R14 to form a fourth simulated branch; the switch K10 is connected in series with the resistor R15 to form a fifth simulated branch; the switch K11 is connected in series with the resistor R16 to form a sixth simulated branch; and,

[0066] The two ends of the first, second, and third simulated branches are connected to the positive pole of the busbar and the ground wire, respectively; the two ends of the fourth, fifth, and sixth simulated branches are connected to the ground wire and the negative pole of the busbar, respectively; when the simulated grounding resistance circuit performs the ground fault simulation verification function, all switches at the positive and negative poles of the busbar are first disconnected; then, according to the polarity and resistance value of the simulated grounding verification, switches K1, K2, K3 and K9, K10, and K11 are controlled to be switched in combination, and the accuracy of the simulated grounding resistance measurement is verified by resistors R11, R12, and R13 of given resistance values;

[0067] The AC input detection circuit includes switches K7 and K15, resistors R5 and R9, and capacitors C1 and C2. Switch K7, capacitor C1, and resistor R5 are connected in series, with their ends connected to the positive busbar and ground respectively. Resistor R9, capacitor C2, and switch K15 are connected in series, with their ends connected to ground and the negative busbar respectively. Resistors R5 and R9 are connected to an analog-to-digital converter.

[0068] When the AC series-in detection circuit is working, the AC series-in detection circuit measurement function is activated when an AC series-in detection circuit is connected between the positive or negative pole of the busbar and the ground. Switches K7 and K15 are closed, and the remaining switches on the busbar are disconnected. If an AC signal is present, the AD converter will detect a voltage difference; if no AC signal is present, there will be no voltage difference.

[0069] The detection signal source circuit includes switches K8 and K16; the two ends of switch K8 are connected to the positive pole of the busbar and the ground wire respectively, and the two ends of switch K16 are connected to the ground wire and the negative pole of the busbar respectively;

[0070] Signal source injection control is used during ground fault detection. When the detection signal source circuit detects that the insulation resistance between the positive pole and the ground is too low, switch K16 is opened, switch K8 is closed, and the detection signal source is connected between the positive pole of the DC bus and the ground wire to prepare for the detection of positive ground faults. When the insulation resistance between the negative pole and the ground is detected to be too low, switch K8 is opened, switch K16 is closed, and the detection signal source is connected between the negative pole of the DC bus and the ground wire to prepare for the detection of negative ground faults.

[0071] And the leakage current collector leakage current collection circuit includes resistors R11, R22, R33, R44, R55, R00, R66, capacitor C3, operational amplifier U0, AD1 digital-analog converter, main controller MCU1, current clamp and switching switch kk;

[0072] One end of the switching switch kk is connected with the resistor R55 and then grounded, and the other end of the switching switch kk is connected with one end of the resistors R11, R22, R33 and R44, and can be selectively connected, and the resistors R11, R22, R33 and R44 have different resistance values, forming a multi-range switching multi-way switch;

[0073] And the other end of the resistors R11, R22, R33 and R44 is connected with the output end of the operational amplifier U0; and the output end of the operational amplifier U0 is further connected with the AD1 digital-analog converter and the main controller MCU1 in sequence; and the main controller MCU1 is in communication connection with the switching switch kk; the first input end of the operational amplifier U0 is connected with the connection end of the resistor R55 and the switching switch kk, and the second input end of the operational amplifier U0 is connected with the resistor R00 and the current clamp; and the resistor R66 and the capacitor C3 are connected in series and then connected in parallel with the resistor R00.

[0074] Compared with the prior art, the present application has the following beneficial effects:

[0075] Compared with the traditional ohm law detection algorithm, the regularization data reuse recursive least square method proposed in the present application designs a regularization term to punish the bus voltage data containing noise, overcomes the defect that the traditional ohm law detection algorithm is disturbed by noise and leads to deviation of the calculation result, and significantly improves the calculation accuracy.

[0076] Compared with the least square algorithm, the regularization data reuse recursive least square method proposed in the present application only uses the current time data to update the parameters in a recursive manner, and is suitable for online real-time processing. Through the data reuse technology, the data utilization rate is effectively improved, and the problem that the least square algorithm is not accurate in identification under the condition of limited data sample quantity is overcome.

[0077] The core idea of the data reuse of the present application is to repeatedly use the data of the current time step for iteration based on the input and output data of the current time step, so that a better identification parameter is obtained under the condition of using less data. In the aspect of regularization, the regularization factor of the present application is used to measure the degree of data abnormality, and the core is to punish the noise data and reduce the influence of the noise data on the identification parameter in the iteration process.

[0078] Wireless communication mode is adopted, the use of external wire is reduced, and the carrying of the integrated insulation detection and verification equipment is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0079] Figure 1 A direct current system insulation detection method flow chart is provided for the embodiment of the present application.

[0080] Figure 2 A verification and detection host principle hardware implementation diagram is provided for the embodiment of the present application.

[0081] Figure 3 A portable direct current system insulation detection and verification integrated device block diagram is provided for the embodiment of the present application.

[0082] Figure 4 A leakage current collector leakage current collection circuit principle diagram is provided for the embodiment of the present application.

[0083] Figure 5 A regularized data reuse recursive least square method and traditional ohm law detection algorithm simulation result comparison diagram is provided for the embodiment of the present application.

[0084] Figure 6 A regularized data reuse recursive least square method and traditional ohm law detection algorithm simulation result comparison diagram is provided for the embodiment of the present application. DETAILED DESCRIPTION

[0085] In order to facilitate those skilled in the art to understand the technical scheme of the present application, the technical scheme of the present application will be further described in conjunction with the drawings of the specification.

[0086] The terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0087] Please refer to Figure 1 A direct current system insulation detection method is disclosed, comprising:

[0088] S10, a direct current system bus insulation detection circuit is constructed, and a mathematical model of bus voltage and bus insulation resistance is established.

[0089] Please refer to Figure 2As shown, in an embodiment of the present application, a DC system bus insulation detection circuit is constructed, the bus insulation detection circuit is analyzed, the mathematical relationship between the positive and negative bus voltages to ground and the positive and negative bus insulation resistances is established, and the mathematical model of the positive and negative bus voltages to ground is obtained. The bus insulation detection circuit includes a bus voltage detection circuit and a balanced / unbalanced bridge control circuit.

[0090] In this embodiment, the bus voltage detection circuit includes detection switches K4 and K12, and resistors R1, R2, R6 and R10. The detection switch K4 is connected in series with the resistor R1 and the resistor R2, and the two ends of the detection switch K4 are connected to the positive bus and the ground line, respectively. The resistor R6 is connected in series with the resistor R10, and the two ends of the resistor R6 are connected to the ground line and the negative bus, respectively.

[0091] In this embodiment, the balanced / unbalanced bridge control circuit includes a balanced bridge circuit and an unbalanced bridge circuit. The balanced bridge circuit includes balanced bridge switches K5 and K13, and resistors R3 and R7. The balanced bridge switch K5 is connected in series with the resistor R3, and the two ends of the balanced bridge switch K5 are connected to the positive bus and the ground line, respectively. The resistor R7 is connected in series with the balanced bridge switch K13, and the two ends of the resistor R7 are connected to the ground line and the negative bus, respectively. The unbalanced bridge circuit includes unbalanced bridge switches K6 and K14, and resistors R4 and R8. The unbalanced bridge switch K6 is connected in series with the resistor R4, and the two ends of the unbalanced bridge switch K6 are connected to the positive bus and the ground line, respectively. The resistor R8 is connected in series with the unbalanced bridge switch K14, and the two ends of the resistor R8 are connected to the ground line and the negative bus, respectively.

[0092] In this embodiment, the mathematical model of the bus voltage and the bus insulation resistance is established, which includes:

[0093] When the detection switches K4 and K12, the balanced bridge switches K5 and K13, and the unbalanced bridge switch K6 are closed and the unbalanced bridge switch K14 is opened, the mathematical model of the bus voltage and the bus insulation resistance is as follows:

[0094] Let

[0095] In the formula, U p1 is the positive bus voltage to ground under the condition, U n1 is the negative bus voltage to ground under the condition of step S20; K is the resistance ratio of the detection switch, and is recorded as K=(R1+R2) / (R6+R 10 ), R4 is the resistance value of the positive unbalanced bridge resistor in the bus voltage detection circuit, R p3 is the equivalent parallel resistance value of the positive bus insulation resistance R p and the balanced bridge resistance R3, and is recorded as R p3 =R p R3 / (R p +R3), R n7For the to-be-calculated negative busbar insulation resistance R n The equivalent parallel resistance of the balance bridge resistance R7 is denoted as R n7 = R n R7 / (R n + R7)R n7 .

[0096] When the detection switch K4 and K12 are closed, the balance bridge switch K5 and K13 are closed, the unbalance bridge switch K6 is opened, and the unbalance bridge switch K14 is closed, the mathematical model of the busbar voltage and the busbar insulation resistance is as follows:

[0097] Denote

[0098] In the formula, U p2 Under this condition, the positive busbar voltage to ground is U n2 The negative busbar voltage to ground is U

[0099] S20, the detection switch K4 and K12 are closed, the balance bridge switch K5 and K13 are closed, the unbalance bridge switch K6 is opened, and the unbalance bridge switch K14 is opened. The positive and negative busbar voltages to ground are measured.

[0100] In an embodiment of the present application, the positive and negative busbar voltages to ground are measured, comprising:

[0101] The unbalance bridge switch K6 is opened, the unbalance bridge switch K14 is closed, and the positive and negative busbar voltages to ground at each time are measured and denoted 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 busbar voltage to ground at the ith measurement, u n1 (i) is the negative busbar voltage to ground at the ith measurement. And wherein, T represents the matrix transpose, and n is the maximum measurement number.

[0102] S30, after each measurement of the positive and negative busbar voltages to ground, the to-be-identified parameter θ1 is updated by the regularized data reuse recursive least square method.

[0103] In an embodiment of the present application, the to-be-identified parameter θ1 is updated by the regularized data reuse recursive least square method, comprising:

[0104] S31, calculate the prediction error e1(i).

[0105] After the i-th measurement, the positive bus voltage to ground u p1 (i) As a reference output, the negative bus voltage to ground u n1 (i) as input, calculate the model prediction error e1(i), where e1(i) = u p1 (i)-θ1(i-1)u n1 (i). θ1(i-1) represents the parameter θ1 to be identified during the i-1th measurement.

[0106] S32, update gain factor K1, covariance matrix P1, data reuse parameters α1, β1, bus voltage mean and the regularization term L1.

[0107] The gain factor calculation formula is: Where λ is the forgetting factor.

[0108] The formula for calculating the covariance matrix is:

[0109] The data reuse parameter calculation formula is: β1=(1-α1 m ) / (1-α1); where m is the number of data reuse times.

[0110] The calculation formula for the bus voltage mean is:

[0111] The regularization term calculation formula is: Among them, μ1 is the regularization term adjustment coefficient.

[0112] S33, update the parameter to be identified θ1(i).

[0113] The update formula of the parameters to be identified is: θ1(i)=θ1(i-1)+L1K1β1e1(i).

[0114] S34, repeat steps S31 to S33 until the measurement is stopped.

[0115] S40, keeping the states of other switches unchanged, disconnecting the unbalanced bridge switch K6, closing the switch K14, and measuring the voltages of the positive and negative busbars to ground.

[0116] In one embodiment of the present invention, measuring the voltage of the positive and negative busbars to ground includes:

[0117] Close the detection switches K4 and K12, the balance bridge switches K5 and K13, open the unbalanced bridge switch K6, close the unbalanced bridge switch K14, and measure the voltage of the positive and negative busbars to the ground at each moment, which is recorded as Up2 =[u p2 (1),...,u p2 (i),...,u p2 (n)] T 、U n2 =[u n2 (1),...,u n2 (i),...,u n2 (n)] T Among them, u p2 (i) is the positive bus voltage to ground at the i-th measurement, u n2 (i) is the negative bus voltage to ground during the i-th measurement.

[0118] S50 , after each measurement of the positive and negative busbar-to-ground voltages, the parameter to be identified θ2 is updated by using a regularized data reuse recursive least squares method.

[0119] In one embodiment of the present invention, the parameter to be identified θ2 is updated by using a regularized data reuse recursive least squares method, including:

[0120] S51, calculate the prediction error e2(i).

[0121] After the i-th measurement, the positive bus voltage to ground u p2 (i) As a reference output, the negative bus voltage to ground u n2 (i) as input, calculate the model prediction error e2(i), where e2(i) = u p2 (i)-θ2(i-1)u n2 (i); where θ2(i-1) represents the parameter θ2 to be identified during the i-1th measurement.

[0122] S52, update gain factor K2, covariance matrix P2, data reuse parameters α2, β2, bus voltage mean and the regularization term L2.

[0123] The gain factor calculation formula is: Where λ is the forgetting factor.

[0124] The formula for calculating the covariance matrix is:

[0125] The data reuse parameter calculation formula is: β2=(1-α2 m ) / (1-α2); where m is the number of data reuse times.

[0126] The calculation formula for the bus voltage mean is:

[0127] The regularization term calculation formula is: Among them, μ2 is the regularization term adjustment coefficient.

[0128] S53, update the parameter to be identified θ2(i).

[0129] The update formula of the parameters to be identified is: θ2(i)=θ2(i-1)+L2K2β2e2(i).

[0130] S54, repeat steps S51 to S53 until the measurement is stopped.

[0131] S60 , calculating the positive and negative busbar insulation resistance values ​​by using the parameters to be identified θ1 and θ2 and combining a mathematical model of the busbar voltage and the busbar insulation resistance.

[0132] In one embodiment of the present invention, the parameters to be identified θ1, θ2 obtained in step S10 and the equivalent resistance R of the positive and negative bus insulation resistances and the balance bridge resistance p3 、R n7 By solving the mathematical relationships, the equivalent resistance calculation formula is:

[0133] R p3 =(θ2-θ1)R4R8 / (KR4+θ1R8), R n7 =(θ2-θ1)KR4R8 / (θ1(KR4+θ2R8)). Then

[0134] The calculation formula for the positive busbar insulation resistance is R p =R p3 R3 / (R3-R p3 ), the negative busbar insulation resistance calculation formula is R n =R n7 R7 / (R7-R n7 ).

[0135] See also Figure 3 As shown, the present invention also provides a portable integrated DC system insulation detection and verification device, comprising: a handheld meter 10, a leakage current collector 20, and a verification and detection host 30. The leakage current collector 20 and the verification and detection host 30 are each wirelessly connected to the handheld meter 10. There is no direct communication between the leakage current collector 20 and the verification and detection host 30. Furthermore, the verification and detection host 30 integrates the DC system insulation detection method described above.

[0136] In this embodiment, the handheld meter 10 is used to visualize and display the data obtained from the leakage current collector and the calibration and detection host. The handheld meter 10 can be implemented using an externally purchased industrial-grade tablet. The industrial tablet is pre-installed with the Android operating system and has a hardware configuration of 6.21 inches with a resolution of 1520*720. The industrial-grade capacitive screen supports wet hand operation / gesture operation / multi-touch / glove mode. It has an 8-core 2.0GHz high-performance processor and 64GB ROM+4GB RAM memory. It has built-in 2G / 3G4G / 5G, Wi-Fi, and Bluetooth wireless communication interfaces, GPS / AGPS / Beidou / Galileo / GLONASS / QZSS / GNSS multi-mode positioning systems, and supports one-dimensional / two-dimensional barcode scanning and other functions. The software is implemented in JAVA language and developed as an Android APP. The Android APP mainly includes a current collector management module, a calibration analyzer management module, a communication module, a data collection processing module, a data and curve display module, a key processing module, a historical data and report management module, a system configuration module, etc.

[0137] In this embodiment, a leakage current collector 20 is used to measure leakage current data. The hardware of leakage current collector 20 consists of a main control MCU, a Bluetooth communication module, a current transformer, a signal grading and amplification module, a filtering module, an analog-to-digital conversion module, a battery management module, and a power on / off and status indicator. The acquisition software, developed in C language, implements the MCU program to receive host commands and data unpacking and sending command responses via wireless communication. It controls the analog-to-digital conversion module to collect current data, performs calculations and waveform recording on the collected data, implements current acquisition circuit calibration, monitors battery charge and manages low power consumption, scans and processes the collector's power on / off buttons, and indicates the collector's operating status.

[0138] See also Figure 4 As shown, in this embodiment, specifically, the leakage current collection circuit of the leakage current collector includes resistors R11, R22, R33, R44, R55, R00, R66, a capacitor C3, an operational amplifier U0, an AD1 digital-to-analog converter, a main controller MCU1, a current clamp and a switching switch kk.

[0139] One end of the switching switch kk is connected to the resistor R55 and then grounded, and the other end of the switching switch kk can be connected to one end of the resistors R11, R22, R33, and R44, and the resistance values ​​of the resistors R11, R22, R33, and R44 are different, forming a multi-way switch with multi-range switching.

[0140] The other ends of resistors R11, R22, R33, and R44 are connected to the output of operational amplifier U0. The output of operational amplifier U0 is also connected in sequence to the AD1 digital-to-analog converter and the main controller MCU1. The main controller MCU1 is in communication with the switch kk. The first input of operational amplifier U0 is connected to the connection end of resistor R55 and the switch kk, and the second input of operational amplifier U0 is connected to resistor R00 and the current clamp. Resistor R66 and capacitor C3 are connected in series and then in parallel with resistor R00.

[0141] In this embodiment, the leakage current acquisition circuit uses a current clamp and a multi-way switch to achieve multi-range automatic switching, ensuring that the measurement circuit and the current magnitude are in the optimal adaptation state, thereby improving the system's measurement accuracy. At the same time, the acquisition circuit is configured with a filtering link to filter out signals with frequencies of 50 Hz and above, preventing excessive signal input from saturating the measurement amplifier circuit and preventing the measurement of useful low-frequency current signals. The specific working principle is as follows:

[0142] The leakage current input current i, according to Kirchhoff's current-voltage law and the virtual short and virtual break principle of the op amp: u2=u1=i*R00,

[0143] Where j = 11, 22, 33, 44. The switching of R11, R22, R33, and R44 is realized by a multi-way switch. The voltage input to the AD1 digital-to-analog converter is obtained by the combined solution. The data collected by AD1 digital-to-analog converter is sent to the main controller MCU1, and the main controller MCU1 switches the multi-way switch to change the R j resistance value, thereby realizing multi-range switching for leakage current i of different sizes.

[0144] See also Figure 2 As shown, in one embodiment of the present invention, the calibration and detection host 30 includes a main control MCU, a wireless communication module, an analog-to-digital conversion module, a power supply module, a bus voltage detection circuit, a balanced bridge / unbalanced bridge control circuit, an analog ground resistance circuit, an AC series detection circuit, a detection signal source circuit, and an LED status indicator. The software is designed using a single-chip microcomputer program and includes wireless communication, analog-to-digital conversion control, calculation of bus voltage, positive and negative bus-to-ground voltage, positive and negative bus-to-ground insulation resistance, bus-to-ground capacitance, bus AC voltage calculation, bus signal amplitude and frequency control, calibration resistance control output, and LED status indication.

[0145] In this embodiment, the calibration and detection host 30 has three external terminals, connected to the DC system bus's positive and negative poles, and to ground. These three input and output terminals provide power for the calibration and detection host 30's normal operation, as well as an input circuit for signal detection and an output circuit for signal injection.

[0146] In this embodiment, the voltage between the positive and negative bus, the positive bus to ground voltage and the negative bus to ground voltage are sampled by the bus voltage detection circuit, and then sent to AD conversion, and the MCU data processing.

[0147] In this embodiment, the analog ground resistance circuit includes switches K1, K2, K3, K9, K10, K11, resistors R11, R12, R13, R14, R15, R16. Switch K1 is connected in series with resistor R11 to form a first analog branch; switch K2 is connected in series with resistor R12 to form a second analog branch. Switch K3 is connected in series with resistor R13 to form a third analog branch. Switch K9 is connected in series with resistor R14 to form a fourth analog branch. Switch K10 is connected in series with resistor R15 to form a fifth analog branch. Switch K11 is connected in series with resistor R16 to form a sixth analog branch.

[0148] In this embodiment, the two ends of the first, second and third analog branches are respectively connected to the positive bus and the ground line. The two ends of the fourth, fifth and sixth analog branches are respectively connected to the ground line and the negative bus. When the analog ground resistance circuit performs the ground fault simulation verification function, all switches of the positive and negative buses are first opened. Then, according to the polarity and resistance value of the analog ground verification, the switches K1, K2, K3 and K9, K10, K11 are controlled to be combined and switched, and the resistance R11, R12, R13 of the given resistance value is used to verify the accuracy of the analog ground resistance measurement.

[0149] In this embodiment, the AC string detection circuit includes switches K7, K15, resistors R5, R9, capacitors C1, C2. Switch K7, capacitor C1 and resistor R5 are connected in series, and the two ends are respectively connected to the positive bus and the ground line. Resistor R9, capacitor C2 and switch K15 are connected in series, and the two ends are respectively connected to the ground line and the negative bus. In addition, resistors R5 and R9 are connected to the AD digital-analog converter.

[0150] In this embodiment, when the AC string detection circuit is working, the positive or negative bus and the ground are connected to the AC string detection circuit measurement function, the switches K7 and K15 are closed, and the remaining switches on the bus are opened. If there is an AC signal, the AD digital-analog converter will detect a voltage difference, and if there is no string, there will be no voltage difference. The sampling circuit uses a capacitor to isolate the direct current, avoiding the influence of direct current on the accuracy of AC sampling.

[0151] In this embodiment, the detection signal source circuit includes switches K8 and K16. The two ends of switch K8 are connected to the positive busbar and the ground line, respectively, while the two ends of switch K16 are connected to the ground line and the negative busbar. Signal source injection control is used during ground fault detection. When the detection signal source circuit detects that the insulation resistance of the positive pole to ground is too low, switch K16 is opened, switch K8 is closed, and the detection signal source is connected between the positive DC busbar and the ground line, preparing to detect a positive ground fault. When the insulation resistance of the negative pole to ground is too low, switch K8 is opened, switch K16 is closed, and the detection signal source is connected between the negative DC busbar and the ground line, preparing to detect a negative ground fault. If both the positive and negative poles have low insulation resistance to ground, the pole with the low insulation resistance is prioritized. After the fault is corrected, the other pole is tested. If both the positive and negative poles have low insulation resistance to ground and the insulation resistances are nearly equal, the positive pole is detected first, followed by the negative pole.

[0152] See also Figures 1 to 4 As shown, in one embodiment of the present invention, in order to verify the effectiveness of the DC system insulation detection method of the present invention, a simulation verification is carried out. In this example, the DC system insulation detection scheme circuit simulation and applied noise parameters are shown in Table 1:

[0153] Table 1 DC system insulation detection scheme circuit simulation and applied noise parameters

[0154] Parameter name Parameter value Simulation time 5(s) Switching time 2.55(s) Simulation sampling time 0.1(s) Positive and negative bus-to-ground voltage U 117(V) <![CDATA[平衡桥电阻R3、R7]]> 30 k(Ω) non-equilibrium bridge resistors R4, R8 120 k(Ω) Positive electrode insulation resistance resistance value R x ]]> 150 k(Ω) Negative electrode insulation resistance resistance value R y ]]> 60 k(Ω) White noise mean, variance 0、0.04 Impulse noise occurrence probability, amplitude 0.05、2

[0155] In this example, the initial parameter settings of the regularized data reuse recursive least squares method are shown in Table 2:

[0156] Table 2 Initial parameter setting table of regularized data reuse recursive least squares method

[0157] Parameter name Parameter value Parameter to be identified θ 0 Covariance matrix P

[1000] Data reuse number m 5 Forgetting factor λ 1 Regularization term adjustment coefficient μ 15.0

[0158] During the simulation, the random seeds for the white noise and impulse noise were varied, and the intensity of the impulse noise was varied to increase the diversity of the experiments and thus verify the robustness of the algorithm. A total of 20 experiments were conducted using the parameters in Tables 1 and 2, and the results were compared with those of other algorithms.

[0159] Figure 5 This is a comparison chart of the simulation results of the regularized data reuse recursive least squares method and the traditional Ohm method. Figure 6This is a comparison chart of the simulation results of the regularized data reuse recursive least squares method and the traditional least squares method. Through calculation, it is known that the mean square errors of the positive and negative busbar insulation resistances of the traditional Ohm's method are 67.86 and 3.38, the mean square errors of the traditional least squares method are 68.83 and 3.15, and the mean square errors of the regularized data reuse recursive least squares method are 27.86 and 1.39. Through comparison, it can be seen that the regularized data reuse recursive least squares method proposed in the present invention is less affected by noise interference, which improves the calculation accuracy, and the fluctuation of the insulation resistance calculation results of multiple experiments is much smaller than that of the traditional Ohm's method and the least squares method, and has higher stability.

[0160] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description. It is intended that all variations within the meaning and range of equivalents of the claims be embraced herein, and any reference signs in the claims should not be construed as limiting the claims to which they relate.

[0161] The above-mentioned embodiments merely represent the implementation methods of the invention. The protection scope of the present invention is not limited to the above-mentioned embodiments. For those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, which all fall within the protection scope of the present invention.

Claims

1. A DC system insulation detection method, characterized in that: include: S10, constructing a DC system busbar insulation detection circuit and establishing a mathematical model of busbar voltage and busbar insulation resistance; The busbar insulation detection circuit includes a busbar voltage detection circuit and a balanced bridge / unbalanced bridge control circuit; the busbar voltage detection circuit is provided with detection switches K4 and K12; one end of the detection switch K4 is connected to the positive electrode of the busbar, and the other end is connected to the positive electrode of the busbar through a resistor. 、 Connect to the ground wire, one end of the detection switch K12 is connected to the negative pole of the busbar, and the other end is connected to the negative pole of the busbar through the resistor 、 Connected to the ground wire; the balanced bridge / unbalanced bridge control circuit includes balanced bridge switches K5 and K13, and unbalanced bridge switches K6 and K14; one end of the balanced bridge switch K5 is connected to the positive electrode of the busbar, and the other end is connected to the positive electrode of the busbar through a resistor Connected to the ground wire, one end of the unbalanced bridge switch K6 is connected to the positive pole of the busbar, and the other end is connected to the positive pole of the busbar through a resistor. Connect to the ground wire, one end of the balance bridge switch K13 is connected to the negative pole of the busbar, and the other end is connected to the negative pole of the busbar through the resistor Connected to the ground wire, one end of the unbalanced bridge switch K14 is connected to the negative pole of the busbar, and the other end is connected to the negative pole of the busbar through a resistor. Connect to the ground wire; S20, close the detection switches K4 and K12, the balance bridge switches K5 and K13, and the unbalanced bridge switch K6, open the unbalanced bridge switch K14, and measure the positive and negative bus voltages to ground. At this time, the mathematical model of the bus voltage and bus insulation resistance is as follows: ;remember ; Where, is the bus positive pole to ground voltage under the condition of step S20, is the voltage of the negative electrode of the busbar to ground under the conditions of step S20; To detect the resistance ratio of the switch route, record it as , is the positive unbalanced bridge resistance in the bus voltage detection circuit, The positive busbar insulation resistance to be calculated With balanced bridge resistance The equivalent parallel resistance is recorded as , The insulation resistance of the negative busbar to be calculated With balanced bridge resistance The equivalent parallel resistance is recorded as ; S30, after each measurement of the positive and negative busbar-to-ground voltages, the parameters to be identified are updated by using the regularized data reuse recursive least squares method. ,include: S31, calculate the prediction error ; No. After the first measurement, the positive bus voltage to ground As a reference output, the negative bus voltage to ground As input, calculate the model prediction error ,in ;in, Expressed as Parameters to be identified during the first measurement ; S32, update gain factor , covariance matrix , data reuse parameters 、 , bus voltage average 、 With regularization term ; The gain factor calculation formula is: ,in For the forgetting factor; The formula for calculating the covariance matrix is: ; The data reuse parameter calculation formula is: , ;in, The number of times the data is reused; The calculation formula for the bus voltage mean is: 、 ; The regularization term calculation formula is: ,in, is the regularization term adjustment coefficient; S33, update the parameters to be identified ; The update formula of the parameters to be identified is: ; S34, repeating steps S31 to S33 until the measurement is stopped; S40: Keep the other switch states unchanged, open the unbalanced bridge switch K6, close the switch K14, and measure the positive and negative bus voltages to ground. At this time, the mathematical model of the bus voltage and bus insulation resistance is as follows: ,remember ; Where, is the voltage of the positive bus to ground under the condition of step S40, is the voltage of the negative bus to ground under the condition of step S40, is the negative unbalanced bridge resistance; S50, after each measurement of the positive and negative busbar-to-ground voltages, the parameters to be identified are updated by recursive least squares method using regularized data reuse ,include: S51, calculate the prediction error ; No. After the first measurement, the positive bus voltage to ground As a reference output, the negative bus voltage to ground As input, calculate the model prediction error ,in ;in, Expressed as Parameters to be identified during the first measurement ; S52, update gain factor , covariance matrix , data reuse parameters 、 , bus voltage average 、 With regularization term ; The gain factor calculation formula is: ,in For the forgetting factor; The formula for calculating the covariance matrix is: ; The data reuse parameter calculation formula is: , ;in, The number of times the data is reused; The calculation formula for the bus voltage mean is: ； The regularization term calculation formula is: ,in, is the regularization term adjustment coefficient; S53, update the parameters to be identified ; The update formula of the parameters to be identified is: ; S54, repeating steps S51 to S53 until the measurement is stopped; S60, through the parameters to be identified 、 , combined with the mathematical model of bus voltage and bus insulation resistance, calculate the positive and negative bus insulation resistance values, including: The parameters to be identified obtained in step S10 、 Equivalent resistance to the positive and negative busbar insulation resistance and balance bridge resistance 、 The mathematical relationship is solved together, and the calculation formula for the positive busbar insulation resistance is: The calculation formula for the negative busbar insulation resistance is: ;in, 、 They are two balanced bridge resistors connected in series.

2. The DC system insulation detection method according to claim 1, characterized in that: In step S20, measuring the voltage of the positive and negative busbars to ground includes: Disconnect the unbalanced bridge switch K6, close the unbalanced bridge switch K14, and measure the voltage of the positive and negative poles of the busbar to the ground at each moment, which are recorded as 、 ;in, For the The positive bus voltage to ground during the first measurement is: For the The negative bus voltage to ground at the time of the first measurement; and T Represented as matrix transpose; is the maximum number of measurements.

3. The DC system insulation detection method according to claim 1, characterized in that: In step S40, measuring the voltage of the positive and negative busbars to ground includes: Close the detection switches K4 and K12, the balance bridge switches K5 and K13, open the unbalanced bridge switch K6, close the unbalanced bridge switch K14, and measure the positive and negative busbar voltages to ground at each moment, which are recorded as 、 ;in, For the The positive bus voltage to ground during the first measurement is: For the Negative bus voltage to ground during the first measurement; T Represented as matrix transpose; is the maximum number of measurements.

4. A portable DC system insulation detection and verification integrated device, characterized in that: include: Handheld meter, leakage current collector and calibration and detection host; The leakage current collector and the calibration and detection host are respectively connected to the handheld meter via wireless communication; Among them, the handheld meter is used for visualization and display of data obtained from the leakage current collector and the calibration and detection host; Leakage current collector, used to measure leakage current data; A calibration and detection host is used to measure bus data and integrate the DC system insulation detection method described in any one of claims 1 to 3.

5. The portable DC system insulation detection and verification integrated device according to claim 4, characterized in that: The calibration and detection host also integrates a simulated ground resistance circuit, an AC series detection circuit, and a detection signal source circuit; among them, The simulated grounding resistance circuit includes switches K1, K2, K3, K9, K10, and K11, and resistors R11, R12, R13, R14, R15, and R16; the switch K1 is connected in series with the resistor R11 to form a first simulated branch; the switch K2 is connected in series with the resistor R12 to form a second simulated branch; the switch K3 is connected in series with the resistor R13 to form a third simulated branch; the switch K9 is connected in series with the resistor R14 to form a fourth simulated branch; the switch K10 is connected in series with the resistor R15 to form a fifth simulated branch; the switch K11 is connected in series with the resistor R16 to form a sixth simulated branch; and, The two ends of the first analog branch, the second analog branch, and the third analog branch are connected to the positive electrode of the busbar and the ground wire respectively; the two ends of the fourth analog branch, the fifth analog branch, and the sixth analog branch are connected to the ground wire and the negative electrode of the busbar respectively; The AC input detection circuit includes switches K7 and K15, resistors R5 and R9, and capacitors C1 and C2. Switch K7, capacitor C1, and resistor R5 are connected in series, with their ends connected to the positive busbar and ground respectively. Resistor R9, capacitor C2, and switch K15 are connected in series, with their ends connected to ground and the negative busbar respectively. Resistors R5 and R9 are connected to an analog-to-digital converter. The detection signal source circuit includes switches K8 and K16; the two ends of switch K8 are connected to the positive pole of the busbar and the ground wire respectively, and the two ends of switch K16 are connected to the ground wire and the negative pole of the busbar respectively; And, the leakage current collection circuit of the leakage current collector includes resistors R11, R22, R33, R44, R55, R00, R66, capacitor C3, operational amplifier U0, AD1 digital-to-analog converter, main controller MCU1, current clamp and switch kk; One end of the switch kk is connected to the resistor R55 and then grounded, and the other end of the switch kk can be connected to one of the resistors R11, R22, R33, and R44, and the resistance values ​​of the resistors R11, R22, R33, and R44 are different, forming a multi-way switch with multi-range switching; The other ends of the resistors R11, R22, R33, and R44 are connected to the output end of the operational amplifier U0; the output end of the operational amplifier U0 is also connected to the AD1 digital-to-analog converter and the main controller MCU1 in sequence; the main controller MCU1 is communicatively connected to the switching switch kk; the first input end of the operational amplifier U0 is connected to the connection end of the resistor R55 and the switching switch kk, the second input end of the operational amplifier U0 is connected to one end of the resistor R00, and the other end of the resistor R00 is connected to the current clamp; and the resistor R66 and the capacitor C3 are connected in series and then in parallel with the resistor R00.

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