A direct current voltage divider step response test method and system

Abstract

The application discloses a direct-current voltage divider step response test method and system, which comprises the following steps: after a step voltage signal is applied, a standard voltage signal output by a standard voltage divider, a secondary voltage signal output by a direct-current voltage transformer and an attenuation time constant of the secondary voltage signal are collected by a direct-current electronic mutual inductor tester; after the standard voltage signal and the secondary voltage signal tend to be stable, an error value of the collected secondary voltage signal and the standard voltage signal is calculated; the error value is used to correct a step response initial value of the collected secondary voltage signal and the collected attenuation time constant, so that a true value of the step response initial value of the secondary voltage signal and a true value of the attenuation time constant are obtained; and based on the true value of the step response initial value of the secondary voltage signal and the true value of the attenuation time constant, the true value of the step response value of the secondary voltage signal at different time is calculated through a step response equation of the direct-current voltage divider. The application can accurately test the step process of the direct-current voltage divider.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission testing technology, and in particular to a method and system for testing the step response of a DC voltage divider. Background Technology

[0002] Taking a ±800kV DC voltage transformer as an example, the DC voltage transformer, which provides analog output, is essentially a DC voltage divider with a rated analog output of 69.5V. The resistance and capacitance of its high-voltage arm are fixed values, while the low-voltage arm and the RC circuit of the secondary signal system together form an RC circuit to complete the DC voltage division. The secondary circuit consists of a pre-balancing circuit and a secondary voltage divider circuit.

[0003] Existing step response tests for DC voltage dividers primarily involve testing the DC voltage divider at the isolation amplifier stage after the RC secondary voltage divider using lightning voltage surges. However, during field operation, DC voltage transformers have repeatedly experienced step response spikes and overshoots at the 69.5V output voltage of the DC voltage divider due to sudden voltage changes, damaging the voltage regulator diodes and causing DC voltage divider output failures that trigger the DC control and protection system to shut down the DC output.

[0004] The lightning voltage generator produces a lightning impulse voltage, which is applied to a DC voltage divider. After passing through the DC voltage divider, the pre-balance plate, and the secondary voltage divider, a small voltage signal of about 5V is output.

[0005] However, lightning impulse tests are open-loop tests. Lightning voltage is not an ideal step signal; there is no stable voltage point, making accurate step response testing impossible. Only post-event waveform recording can be used to analyze the rise time of the DC voltage divider. Lightning impulse tests cannot measure the instantaneous value of the DC voltage overshoot in the secondary output voltage signal of the DC voltage divider's step response process, thus failing to accurately test the DC voltage divider's step response and consequently failing to effectively prevent damage to the Zener diode in the low-voltage arm of the voltage divider. Summary of the Invention

[0006] This invention provides a method and system for testing the step response of a DC voltage divider, thereby solving the problem that existing technologies cannot accurately test the step response of a DC voltage divider.

[0007] Firstly, a method for testing the step response of a DC voltage divider is provided, including:

[0008] A DC voltage divider step response test circuit is constructed, comprising: a step voltage generator, a standard voltage divider, a DC voltage transformer, and a DC electronic transformer tester. The output terminal of the step voltage generator is connected to the input terminals of the standard voltage divider and the DC voltage transformer, respectively. The input terminal of the DC electronic transformer tester is connected to the output terminals of the standard voltage divider and the DC voltage transformer, respectively.

[0009] After a step voltage signal is applied by the step voltage generator, the standard voltage signal output by the standard voltage divider, the secondary voltage signal output by the DC voltage transformer, and the decay time constant of the secondary voltage signal are acquired by the DC electronic transformer tester.

[0010] Once the secondary voltage signal meets the sudden change triggering condition, and after the standard voltage signal and the secondary voltage signal stabilize, the error value of the acquired secondary voltage signal and the standard voltage signal is calculated.

[0011] The error value is used to correct the initial value of the step response of the acquired secondary voltage signal and the acquired decay time constant, so as to obtain the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant.

[0012] Based on the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant, the true value of the step response of the secondary voltage signal at different times is calculated by using the step response equation of the DC voltage divider.

[0013] Secondly, a DC voltage divider step response testing system is provided, comprising:

[0014] The circuit construction module is used to construct a DC voltage divider step response test circuit. The DC voltage divider step response test circuit includes: a step voltage generator, a standard voltage divider, a DC voltage transformer, and a DC electronic transformer tester. The output terminal of the step voltage generator is connected to the input terminals of the standard voltage divider and the DC voltage transformer, respectively. The input terminal of the DC electronic transformer tester is connected to the output terminals of the standard voltage divider and the DC voltage transformer, respectively.

[0015] The acquisition module is used to acquire, through the DC electronic transformer tester, the standard voltage signal output by the standard voltage divider, the secondary voltage signal output by the DC voltage transformer, and the decay time constant of the secondary voltage signal after a step voltage signal is applied by the step voltage generator.

[0016] The first calculation module is used to calculate the error value of the acquired secondary voltage signal and the standard voltage signal after the secondary voltage signal meets the sudden change start condition and the standard voltage signal stabilizes.

[0017] The correction module is used to correct the initial value of the step response of the acquired secondary voltage signal and the acquired decay time constant using the error value, so as to obtain the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant.

[0018] The second calculation module, based on the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant, calculates the true value of the step response of the secondary voltage signal at different times through the step response equation of the DC voltage divider.

[0019] Thus, the embodiments of the present invention can accurately test the step process of a DC voltage divider, thereby improving the safety of the DC voltage divider during DC voltage step processes. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the DC voltage divider step response test method according to an embodiment of the present invention;

[0022] Figure 2 This is a structural diagram of the DC voltage divider step response test circuit according to an embodiment of the present invention;

[0023] Figure 3 This is a circuit diagram of the sampling signal conditioning circuit of the DC electronic current transformer tester according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the equivalent circuit of the DC voltage divider test process according to an embodiment of the present invention;

[0025] Figure 5 This is a structural block diagram of the DC voltage divider step response test system according to an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0027] This invention discloses a method for testing the step response of a DC voltage divider. For example... Figure 1 As shown, the method of this embodiment of the invention includes the following steps:

[0028] Step S101: Construct a DC voltage divider step response test circuit.

[0029] Among them, such as Figure 2 As shown, the DC voltage divider step response test circuit includes: a step voltage generator, a standard voltage divider, a DC voltage transformer, and a DC electronic transformer tester. The output terminal of the step voltage generator is connected to the input terminals of the standard voltage divider and the DC voltage transformer, respectively. The input terminal of the DC electronic transformer tester is connected to the output terminals of the standard voltage divider and the DC voltage transformer, respectively.

[0030] Specifically, the DC voltage transformer includes a DC voltage divider, a pre-balance plate, and a secondary voltage divider connected in sequence. The output terminal of the step voltage generator is connected to the input terminal of the DC voltage divider, and the input terminal of the DC electronic transformer tester is connected to the output terminal of the secondary voltage divider.

[0031] In one specific embodiment, the step voltage generator can output a 10kV DC step voltage signal. A standard voltage divider uses pure resistance to divide the 10kV voltage into a small voltage that can be sampled by the DC electronic instrument transformer tester, with a voltage division ratio of 10000 / 5. The DC electronic instrument transformer tester is then connected after the DC voltage transformer. The sampling and conditioning circuit inside the DC electronic instrument transformer tester is as follows... Figure 3 As shown, the input impedance of the entire test circuit is fixed at R. eqm =R A +R B The low-pass filter circuit of the sampling conditioning circuit consists of a resistor R1 and a capacitor C1 connected in parallel. Its design parameters are selected according to the cutoff frequency of 500kHz, which is half of the transient sampling rate of the tester (1MHz).

[0032] During field testing, the high and low voltage arms of the DC voltage divider were affected by stray capacitance, such as... Figure 4 As shown, the equivalent circuit resistance of the high-voltage arm of the DC voltage divider is R. eq1 The equivalent circuit capacitance of the high-voltage arm of the DC voltage divider is C. eq1The equivalent circuit resistance of the low-voltage arm of the DC voltage divider is R. eq2 The equivalent circuit capacitance of the low-voltage arm of the DC voltage divider is C. eq2 The low-voltage arm, pre-balance plate, and secondary voltage divider of the DC voltage divider constitute the secondary circuit, including R. eq2 and C eq2 The parallel circuit introduces an error test loop, the equivalent resistance of which is R. eqm According to the equivalent circuit analysis, adding a test circuit is equivalent to adding a resistor in parallel, which reduces the secondary equivalent resistance.

[0033] Specifically, the equivalent resistance R of the secondary circuit eqm2 The calculation formula is as follows:

[0034]

[0035] Based on the voltage division ratio of the DC voltage divider (800kJ / 69.5), the current in the main circuit (i.e., the equivalent circuit of the high-voltage arm) is equal to the current in the secondary voltage divider circuit. Therefore, the transfer function between the input primary voltage and the output secondary voltage can be obtained as follows:

[0036] u1(t) / R eq1 +C eq1 du1(t) / dt=u2(t) / R eq2 +C eq2 du2(t) / dt.

[0037] Where u1(t) represents the instantaneous value of the primary voltage signal input at time t, and u2(t) represents the instantaneous value of the secondary voltage signal output at time t.

[0038] Solving the differential equation for the first voltage step response yields:

[0039]

[0040] in, τ=R eq2 C eq2 U1 represents the target value of the first step voltage, that is, the smaller voltage obtained after the step voltage signal is divided by the standard voltage divider. U2(t) represents the step response value of the second voltage signal at time t. U2(0) represents the initial value of the step response of the second voltage signal.

[0041] Step S102: After applying a step voltage signal through the step voltage generator, the standard voltage signal output by the standard voltage divider, the secondary voltage signal output by the DC voltage transformer, and the decay time constant of the secondary voltage signal are collected by the DC electronic transformer tester.

[0042] The secondary voltage signal output by the DC voltage transformer is the voltage signal that is finally output from the secondary voltage divider.

[0043] Step S103: After the secondary voltage signal meets the sudden change start condition, and after the standard voltage signal and the secondary voltage signal stabilize, calculate the error value of the acquired secondary voltage signal and the standard voltage signal.

[0044] Specifically, the trigger condition for the mutation is: Δu2 > η. Here, Δu2 represents the instantaneous change in the secondary voltage signal, and η represents the preset threshold.

[0045] Specifically, Δu2 = [u2(t) - u2(tT)]. Where u2(t) represents the instantaneous value of the secondary voltage signal at time t, u2(tT) represents the instantaneous value of the secondary voltage signal at time tT, and T represents the preset interval time, which can be set empirically.

[0046] That is, the change in the instantaneous value of the secondary voltage signal is calculated every preset interval. When the change is greater than the preset threshold, the secondary voltage signal is considered to meet the sudden change trigger condition.

[0047] Since the step response is a transient test process, a test data window needs to be established. The calculation is performed based on the step response stabilizing. After stabilization, a 5ms data window is established, and the data within the data window is used for calculation.

[0048] Specifically, the formula for calculating the error value is:

[0049] U σ =U 2s -U2.

[0050] Among them, U 2s U1 represents the steady-state DC voltage value of the secondary voltage signal, while U2 represents the steady-state DC voltage value of the standard voltage signal.

[0051] Step S104: Correct the initial value of the step response of the acquired secondary voltage signal and the acquired decay time constant using the error value to obtain the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant.

[0052] By using the step response formula of the RC voltage divider, it can be found that the change of the secondary load of the DC voltage divider is linear with respect to steady-state DC, the initial value of the step response, and the step response time. Therefore, the test overshoot value and the true value of the step response time of the RC voltage divider can be obtained by using the resistance correction coefficient.

[0053] Specifically, the formula for calculating the true value of the initial value of the step response of the secondary voltage signal is:

[0054] U 2r (0)=U2m (0)-U σ .

[0055] Among them, U 2r (0) represents the true value of the initial value of the step response of the secondary voltage signal, U 2m (0) represents the initial value of the step response of the acquired secondary voltage signal.

[0056] Specifically, the initial value of the step response of the secondary voltage signal is the instantaneous value of the secondary voltage signal at time 0. When the sampling rate is high enough, the value of the first point after the abrupt change is the initial value of the step response, which is also the overshoot value of the step response. When the sampling rate of the tester is 1MHz, the single-point sampling interval is 1µs, which is much smaller than the decay time constant. In order to eliminate test errors, this embodiment of the invention can use the average of three consecutive points after the abrupt change as the initial value of the step response of the acquired secondary voltage signal.

[0057] The decrease in resistance leads to a linear change in the decay time constant. Therefore, the decay time constant is obtained by measuring the change in the step process value of the sample, and then corrected using the resistance correction factor ε to obtain the true value of the final decay time constant. Specifically, the formula for calculating the true value of the decay time constant is:

[0058] τ=(1-ε)τ m .

[0059] Where τ represents the true value of the decay time constant, τ m ε represents the attenuation time constant of the sampled data, and ε represents the correction coefficient of the resistance calculated from the error value.

[0060] The formula for calculating the resistance correction factor is as follows:

[0061] ε=U σ / U2.

[0062] Where ε represents the resistance correction factor, U σ U1 represents the error value, and U2 represents the steady-state DC voltage value of the standard voltage signal.

[0063] Step S105: Based on the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant, the true value of the step response of the secondary voltage signal at different times is calculated through the step response equation of the DC voltage divider.

[0064] Specifically, the formula for calculating the true value of the jump response of the secondary voltage signal is:

[0065]

[0066] Among them, U 2r (t) represents the true value of the jump response of the secondary voltage signal at time t, U2r (0) represents the true value of the initial value of the step response of the secondary voltage signal, U1 represents the smaller voltage obtained after the step voltage signal is divided by a standard voltage divider, R eq1 R represents the resistance of the equivalent circuit of the high-voltage arm of a DC voltage divider. eq2 This represents the resistance of the equivalent circuit of the low-voltage arm of a DC voltage divider.

[0067] By calculating the true value of the step response of the secondary voltage signal at time t, the true waveform of the step response of the DC voltage divider can be constructed so that the overshoot value and step response delay of the step process can be tested according to the instantaneous value of each point in accordance with the standard requirements of the DC voltage transformer.

[0068] This invention also discloses a DC voltage divider step response testing system, such as... Figure 5 As shown, it includes:

[0069] The circuit construction module 501 is used to build a DC voltage divider step response test circuit.

[0070] The DC voltage divider step response test circuit includes: a step voltage generator, a standard voltage divider, a DC voltage transformer, and a DC electronic transformer tester. The output of the step voltage generator is connected to the input of the standard voltage divider and the DC voltage transformer, respectively. The input of the DC electronic transformer tester is connected to the output of the standard voltage divider and the DC voltage transformer, respectively.

[0071] The acquisition module 502 is used to acquire the standard voltage signal output by the standard voltage divider, the secondary voltage signal output by the DC voltage transformer, and the decay time constant of the secondary voltage signal through a DC electronic transformer tester after a step voltage signal is applied by the step voltage generator.

[0072] The first calculation module 503 is used to calculate the error value of the acquired secondary voltage signal and the standard voltage signal after the secondary voltage signal meets the sudden change start condition and the standard voltage signal and the secondary voltage signal stabilize.

[0073] The correction module 504 is used to correct the initial value of the step response of the acquired secondary voltage signal and the acquired decay time constant using the error value, so as to obtain the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant.

[0074] The second calculation module 505, based on the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant, calculates the true value of the step response of the secondary voltage signal at different times through the step response equation of the DC voltage divider.

[0075] The DC voltage divider step response test system of this invention can implement the method of the above embodiments, and will not be described again here.

[0076] In summary, the embodiments of the present invention can accurately test the step process of a DC voltage divider, thereby improving the safety of the DC voltage divider during DC voltage step processes.

[0077] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for testing the step response of a DC voltage divider, characterized in that, include: A DC voltage divider step response test circuit is constructed, comprising: a step voltage generator, a standard voltage divider, a DC voltage transformer, and a DC electronic transformer tester. The output terminal of the step voltage generator is connected to the input terminals of the standard voltage divider and the DC voltage transformer, respectively. The input terminal of the DC electronic transformer tester is connected to the output terminals of the standard voltage divider and the DC voltage transformer, respectively. After a step voltage signal is applied by the step voltage generator, the standard voltage signal output by the standard voltage divider, the secondary voltage signal output by the DC voltage transformer, and the decay time constant of the secondary voltage signal are acquired by the DC electronic transformer tester. Once the secondary voltage signal meets the sudden change triggering condition, and after the standard voltage signal and the secondary voltage signal stabilize, the error value of the acquired secondary voltage signal and the standard voltage signal is calculated. The error value is used to correct the initial value of the step response of the acquired secondary voltage signal and the acquired decay time constant, so as to obtain the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant. Based on the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant, the true value of the step response of the secondary voltage signal at different times is calculated using the step response equation of the DC voltage divider.

2. The DC voltage divider step response test method of claim 1, wherein, The DC voltage transformer includes a DC voltage divider, a pre-balance plate, and a secondary voltage divider connected in sequence. The low-voltage arm of the DC voltage divider, the pre-balance plate, and the secondary voltage divider form a secondary circuit.

3. The DC voltage divider step response test method of claim 2, wherein, The formula for calculating the error value is: U σ = U 2s - U2; wherein U 2s represents the steady-state DC voltage value of the secondary voltage signal, U2 represents the steady-state DC voltage value of the standard voltage signal.

4. The DC voltage divider step response test method of claim 2, wherein, The formula for calculating the true value of the initial value of the step response of the secondary voltage signal is: U 2r (0) = U 2m (0) - U σ ; wherein U 2r (0) represents the true value of the step response initial value of the secondary voltage signal, U 2m (0) represents the step response initial value of the secondary voltage signal acquired, U σ represents the error value.

5. The DC voltage divider step response test method of claim 2, wherein, The true value of the decay time constant is calculated as follows: τ = (1 - ε)τ m ; Where τ represents the true value of the decay time constant, τ m The attenuation time constant is represented by ε, and the resistance correction coefficient is calculated from the error value.

6. The DC voltage divider step response test method of claim 5, wherein, The formula for calculating the correction factor of the resistor is: ε = U σ / U2; Where ε represents the correction factor for the resistance, U σ U1 represents the error value, and U2 represents the steady-state DC voltage value of the standard voltage signal.

7. The DC voltage divider step response test method of claim 2, wherein, The formula for calculating the true value of the jump response value of the secondary voltage signal is: Among them, U 2r (t) represents the true value of the jump response of the secondary voltage signal at time t, U 2r (0) represents the true value of the initial value of the step response of the secondary voltage signal, U1 represents the smaller voltage obtained after the step voltage signal is divided by the standard voltage divider, and R eq1 R represents the resistance of the equivalent circuit of the high-voltage arm of a DC voltage divider. eq2 This represents the resistance of the equivalent circuit of the low-voltage arm of a DC voltage divider.

8. The DC voltage divider step response test method of claim 2, wherein, The mutation activation condition is: Δu2>η; Where Δu2 represents the instantaneous change in the secondary voltage signal, and η represents the preset threshold; Where Δu2=[u2(t)-u2(tT)], u2(t) represents the instantaneous value of the secondary voltage signal at time t, u2(tT) represents the instantaneous value of the secondary voltage signal at time tT, and T represents the preset interval time.

9. A direct current voltage divider step response test system characterized by, include: The circuit construction module is used to construct a DC voltage divider step response test circuit. The DC voltage divider step response test circuit includes: a step voltage generator, a standard voltage divider, a DC voltage transformer, and a DC electronic transformer tester. The output terminal of the step voltage generator is connected to the input terminals of the standard voltage divider and the DC voltage transformer, respectively. The input terminal of the DC electronic transformer tester is connected to the output terminals of the standard voltage divider and the DC voltage transformer, respectively. The acquisition module is used to acquire, through the DC electronic transformer tester, the standard voltage signal output by the standard voltage divider, the secondary voltage signal output by the DC voltage transformer, and the decay time constant of the secondary voltage signal after a step voltage signal is applied by the step voltage generator. The first calculation module is used to calculate the error value of the acquired secondary voltage signal and the standard voltage signal after the secondary voltage signal meets the sudden change start condition and the standard voltage signal stabilizes. The correction module is used to correct the initial value of the step response of the acquired secondary voltage signal and the acquired decay time constant using the error value, so as to obtain the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant. The second calculation module, based on the true value of the initial value of the step response of the secondary voltage signal and the true value of the decay time constant, calculates the true value of the step response of the secondary voltage signal at different times through the step response equation of the DC voltage divider.

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