A method for testing voltage sag immunity by dichotomic partitioning

Abstract

The application provides a voltage sag resistance capacity division bisection test method. According to the characteristics of a "rectangular shape" and a "non-rectangular shape" of a voltage resistance curve, the special position of an inflection point is utilized to divide the entire amplitude-duration plane into two parts, and different methods are respectively adopted to quickly test according to the different characteristics of the two parts.

Description

Technical Field

[0001] This invention relates to the field of voltage drop withstand capability testing technology, and in particular to a partial bisection method for testing voltage sag withstand capability. Background Technology

[0002] In modern industrial parks, equipment is becoming increasingly integrated and sophisticated, with a large number of precision devices being deployed in production and daily life. Against this backdrop, the contradiction between voltage sag events—inevitable events in power systems—and the increasingly sensitive nature of high-tech precision equipment is becoming increasingly prominent. Therefore, studying the impact of voltage sags on equipment through testing has become a hot topic and a challenging issue for both industry and academia. Rationally describing the characteristics, degree, and patterns of voltage sag impacts on equipment through actual measurements can intuitively express its tolerance. The impact of voltage sags on the normal operation of sensitive equipment is highly complex and uncertain. Scientifically investigating complex and uncertain events requires not only in-depth exploration of their impact mechanisms but also the acquisition of assessment data through scientific methods. In addition to obtaining assessment samples through actual production, obtaining data through actual measurements has become an essential choice.

[0003] Looking at domestic and international research on equipment withstand capability testing methods, current methods for testing equipment voltage sag withstand capability include: the top-down method, left-to-right method, and closed method proposed by IEEE Std 1668-2017, the step-by-step testing method adopted by foreign scholars, and the dichotomy method proposed by the power quality team of Sichuan University.

[0004] A comprehensive analysis of existing testing methods reveals that they primarily rely on the methods outlined in the IEEE 1668-2017 standard and the point-by-point method. While the IEEE 1668-2017 method offers a clear test plan, it is prone to missing critical points on non-rectangular withstand curves. The point-by-point method, with its small test step size, offers high accuracy but is labor-intensive and time-consuming. All of these methods for testing the voltage sag withstand capability of equipment suffer from drawbacks, including low accuracy of the obtained curves, slow testing speed, inability to accurately measure the VTC at the 0° starting point of the AC contactor, and low accuracy in testing the horizontal portion of rectangular voltage withstand curves. Summary of the Invention

[0005] The purpose of this invention is to provide a bipartite test method for voltage sag withstand capability, which can improve the test accuracy of the horizontal portion of the rectangular voltage withstand capability curve.

[0006] This invention is achieved through the following technical solution: a partial binary method for testing voltage sag tolerance, characterized by comprising the following steps:

[0007] S1. Determine the initial voltage sag of the power equipment under test, and determine the critical duration T0 of the power equipment under test at the initial voltage sag using the time bisection method.

[0008] S2. The voltage sag is increased in equal steps, and the power equipment under test is tested cyclically using the time bisection method. The time bisection interval and critical duration of each test cycle are determined. If the critical duration of a cycle is greater than 20ms compared to the previous cycle, the point determined by the cycle is the dividing point and the test cycle is stopped. The voltage sag value corresponding to the dividing point is recorded as U1 and the duration as T1. Otherwise, the step is repeated to continue the test cycle.

[0009] S3. Divide the entire amplitude-duration plane into upper and lower parts using the dividing line y = U1. The part below the dividing line is the first part, and the part above the dividing line is the second part.

[0010] S4. Connect the critical duration points under each amplitude according to the cyclical order of the first part to obtain the first tolerance curve of the power equipment under test.

[0011] S5. The second part takes T1+20ms as the initial duration, and the duration of the second part increases in equal steps. The critical sag amplitude of the power equipment under test under the duration is determined by the amplitude bisection method.

[0012] S6. The second part is cyclically tested using the amplitude bisection method, and the voltage sag amplitude corresponding to each cycle is obtained. When the duration of the second part reaches the maximum value, the cyclic test of the second part ends. The critical sag amplitude points under each duration are connected according to the cyclic sequence of the second part to obtain the second withstand curve of the power equipment under test.

[0013] S7. Connect the first tolerance curve and the second tolerance curve to obtain the power tolerance curve of the entire device under test.

[0014] Preferably, step S1 includes: determining the initial voltage sag of the power equipment under test to be 0%.

[0015] Preferably, step S2 includes: increasing the voltage sag in equal steps of 5%, and performing cyclic testing on the power equipment under test using a time-division method at different voltage sag values; during the cyclic testing process, if the voltage sag is within the maximum duration T... max If the electrical equipment under test does not malfunction under these conditions, it is assumed that the electrical equipment under test can withstand the voltage dip of this magnitude, and the cyclic test is stopped.

[0016] Preferably, the maximum duration T max It lasts for 2 seconds.

[0017] Preferably, step S2 further includes: during the cyclic testing of the power equipment under test using the time bisection method, with T0+100ms as the first test point, if the power equipment under test fails at T0+100ms, the time bisection interval is set to [0ms, T0+100ms], and if the power equipment under test is normal at T0+100ms, the time bisection interval is set to [T0+100ms, 2000ms].

[0018] Preferably, when the length of the time interval is less than 1ms, the corresponding loop test ends and the next loop begins.

[0019] Preferably, step S5 includes: increasing the duration of the second part in equal increments of 20ms.

[0020] Preferably, step S5 further includes: the duration of the second part reaches its maximum value at 2000ms.

[0021] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention provides a bipartite testing method for voltage sag withstand capability. Based on the characteristics of voltage withstand curves having both "rectangular" and "non-rectangular" shapes, the method utilizes the special position of the inflection point to divide the entire amplitude-duration plane into two parts. Then, different methods are used to quickly test each part according to its different characteristics. This method is applicable to testing the withstand curves of various types of equipment, requires minimal testing workload, and achieves high testing accuracy. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only preferred embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart of a partial bisection method for testing voltage sag tolerance provided by the present invention;

[0024] Figure 2 This is a schematic diagram of the boundary line between the amplitude and duration planes.

[0025] Figure 3 This is a schematic diagram showing the test results of the switching power supply using the two-part method.

[0026] Figure 4 This is a schematic diagram showing the results of testing a switching power supply using the step-by-step testing method.

[0027] Figure 5This is a schematic diagram showing the results of testing a switching power supply using a closed-loop testing method, from top to bottom and from left to right.

[0028] Figure 6 This is a schematic diagram showing the test results of the switching power supply using the binary search method.

[0029] Figure 7 This is a schematic diagram showing the results of testing an AC contactor using the two-part method.

[0030] Figure 8 This is a schematic diagram showing the results of testing an AC contactor using the step-by-step testing method. Detailed Implementation

[0031] To better understand the technical content of this invention, specific embodiments are provided below, and the invention will be further described in conjunction with the accompanying drawings.

[0032] See Figures 1 to 2 This invention discloses a partial bisection method for testing voltage sag tolerance, comprising the following steps:

[0033] S1. Determine the initial voltage sag of the power equipment under test. The initial voltage sag is 0%. The voltage sag increases from 0% in steps of 5%. The duration T0 of the power equipment under test at the voltage sag is determined by the time bisection method.

[0034] S2. Under different voltage sag amplitudes, the power equipment under test is subjected to cyclic testing using the time-division bisection method. During the cyclic testing process, if the maximum duration T is reached... max If the electrical equipment under test does not malfunction under these conditions, it is assumed that the electrical equipment under test can withstand the voltage dip of this magnitude, and the cyclic test is stopped.

[0035] Where T max The maximum time is preferably 2ms, following the guidelines of IEEE 1668-2017.

[0036] During the cyclic testing of the power equipment under test using the time bisection method, T0+100ms is taken as the first test point. If the power equipment under test fails at T0+100ms, the time bisection interval is set to [0ms, T0+100ms]; if the power equipment under test is normal at T0+100ms, the time bisection interval is set to [T0+100ms, 2000ms]. When the interval length is less than 1ms, the current cycle ends and the next cycle begins.

[0037] In some embodiments of the present invention, when the critical duration of the next cycle is greater than 20ms compared to the critical duration of the previous cycle, the cycle test is stopped, and the voltage sag value U1 and duration T1 corresponding to the dividing line are recorded.

[0038] S3. During the cyclic test using the time bisection method, when the critical duration of the next cycle is greater than the critical duration of the previous cycle by more than 20ms, the voltage sag amplitude of the next cycle is used as the dividing line to divide the entire amplitude-duration plane into two parts, with the part below the dividing line being the first part and the part above the dividing line being the second part. The voltage sag amplitude U1 and duration T1 corresponding to the dividing line are recorded.

[0039] S4. Connect the critical duration points under each sag value according to the cyclical order of the first part to obtain the first tolerance curve of the power equipment under test.

[0040] S5. The second part takes T1+20ms as the initial duration and 20ms as the step size. The duration of the second part increases by equal steps. The voltage sag amplitude of the power equipment under test under the duration is determined by the amplitude bisection method.

[0041] S6. The second part is cyclically tested using the amplitude bisection method, and the voltage sag amplitude corresponding to each cycle is obtained. When the duration of the second part reaches the maximum value, the cyclic test of the second part ends. The critical sag amplitude points under each duration are connected according to the cyclic sequence of the second part to obtain the second withstand curve of the power equipment under test.

[0042] In some embodiments of the invention, the duration of the second part reaches its maximum value at 2000 ms.

[0043] S7. Connect the first tolerance curve and the second tolerance curve to obtain the power tolerance curve of the entire device under test.

[0044] To verify the applicability and correctness of the test method proposed in this invention, actual tests were conducted on the switching power supply and the AC contactor, respectively.

[0045] The switching power supply is from Merck, with a rated output voltage of 24V and a rated power of 150W. Under the 0° waveform start point and 0° phase transition characteristic, only amplitude and duration are considered as influencing factors. The actual inflection point of this switching power supply is (68%, 112ms). The AC contactor used is a Siemens 3RT6018-1AN21 contactor. Under the 0° waveform start point and 0° phase transition characteristic, only amplitude and duration are considered as influencing factors. The step-by-step test method uses a time step of 5ms and an amplitude step of 5%. The amplitude step for both the top-to-bottom and left-to-right methods is 5%. The binary method uses an amplitude step of 5%, ending the cycle when the time difference between the two points is 1ms, with a maximum duration of 2s. For all test methods, the maximum voltage amplitude is set to 85%, the minimum voltage amplitude to 0%, and the maximum and minimum durations to 2s and 0.02s, respectively.

[0046] Record the number of tests and the obtained inflection point values ​​for each test method when testing the switching power supply. Compare the duration of the inflection point amplitude with the actual duration of the inflection point amplitude to obtain the maximum time error and the maximum amplitude error for each test method, as shown in Table 1.

[0047] Table 1

[0048] From top to bottom 25 15 2 From left to right 25 15 2 Closed 12 15 2 Step-by-step testing method 6384 3 2 dichotomy 132 2 2 Partial Dichotomy 63 Approximately 1 2

[0049] The inflection point values ​​obtained by the top-down and left-to-right methods proposed in IEEE 1668-2017 are (70%, 100ms); the inflection point value obtained by the step-by-step testing method is also (70%, 115ms); the inflection point value obtained by the bisection method is (70%, 109ms); and the inflection point value obtained by the partial bisection method is (70%, 113ms). The voltage withstand curves obtained by each testing method are shown below. Figure 3 — Figure 6 As shown.

[0050] Comparing the inflection point values ​​obtained by the above testing methods with the actual inflection point values, the part-by-part bisection method has the smallest testing error. Although the bisection method has a similar error to the part-by-part bisection method, it uses more testing methods. Compared with the closed method, the number of tests is greatly reduced, and the error of the test data is also smaller. Furthermore, the part-by-part bisection method can more accurately obtain the vertical portion of the non-rectangular withstand curve. Therefore, through actual testing, it is found that the main advantage of the part-by-part bisection method proposed in this paper is that it can improve both testing efficiency and testing accuracy, and it is applicable to voltage withstand curves of various shapes, proving that the method has universality.

[0051] The withstand voltage curves of the AC contactor were tested using the bisection method and the partial bisection method. The resulting voltage withstand curves are shown below. Figure 7 — Figure 8 As shown in the figure. Comparing the two figures, it can be found that the voltage withstand curve obtained by the "partial bisection method" has the highest accuracy.

[0052] When using the bisection method, with an amplitude step size of 5%, the test cycle ends and the next cycle begins when the time difference between two points is 1ms. The partial bisection method uses the same amplitude and time step size as the bisection method. Analysis of the test results shows that the top-to-bottom, left-to-right, and closed-loop testing methods cannot obtain a complete voltage sag withstand curve. Using the step-by-step testing method, with amplitude and time steps set to 5% and 5ms respectively, more than 4000 tests are required to obtain a relatively complete voltage withstand curve. The voltage withstand curve obtained by the bisection method is similar to that of the partial bisection method, but the bisection method requires nearly 100 tests, while the partial bisection method only requires 60. Therefore, by comprehensively comparing the required number of tests and the obtained withstand curves, the partial bisection method shows higher testing accuracy and faster convergence speed.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing voltage sag withstand capability using a part-by-part method, characterized in that, Includes the following steps: S1. Determine the initial voltage sag of the power equipment under test, and determine the critical duration T0 of the power equipment under test at the initial voltage sag using the time bisection method. S2. The voltage sag is increased in equal steps, and the power equipment under test is tested cyclically using the time bisection method. The time bisection interval and critical duration of each test cycle are determined. If the critical duration of a cycle is greater than 20ms compared to the previous cycle, the point determined by the cycle is the dividing point and the test cycle is stopped. The voltage sag value corresponding to the dividing point is recorded as U1 and the duration as T1. Otherwise, the step is repeated to continue the test cycle. S3. Divide the entire amplitude-duration plane into upper and lower parts using the dividing line y = U1. The part below the dividing line is the first part, and the part above the dividing line is the second part. S4. Connect the critical duration points under each amplitude according to the cyclical order of the first part to obtain the first tolerance curve of the power equipment under test. S5. The second part takes T1+20ms as the initial duration, and the duration of the second part increases in equal steps. The critical sag amplitude of the power equipment under test under the duration is determined by the amplitude bisection method. S6. The second part is cyclically tested using the amplitude bisection method, and the voltage sag amplitude corresponding to each cycle is obtained. When the duration of the second part reaches the maximum value, the cyclic test of the second part ends. The critical sag amplitude points under each duration are connected according to the cyclic sequence of the second part to obtain the second withstand curve of the power equipment under test. S7. Connect the first withstand curve and the second withstand curve to obtain the power withstand curve of the entire device under test. Step S1 includes: determining that the initial voltage sag of the power equipment under test is 0%; Step S2 includes: increasing the voltage sag in equal steps of 5%, and performing cyclic testing on the power equipment under test using a time-division bisection method at different voltage sag values. During the cyclic testing process, if the voltage sag is within the maximum duration T... max If the electrical equipment under test does not malfunction under these circumstances, it is determined that the electrical equipment under test can withstand the voltage sag of this magnitude, and the cyclic test is stopped. The maximum duration T max It takes 2 seconds; Step S2 further includes: during the cyclic testing of the power equipment under test using the time bisection method, with T0+100ms as the first test point, if the power equipment under test fails at T0+100ms, the time bisection interval is set to [0ms, T0+100ms], and if the power equipment under test is normal at T0+100ms, the time bisection interval is set to [T0+100ms, 2000ms].

2. The method for testing voltage sag withstand capability using a partial bisection method according to claim 1, characterized in that, When the length of the time interval is less than 1ms, the corresponding loop test ends and the next loop begins.

3. The method for testing voltage sag withstand capability using a partial bisection method according to claim 1, characterized in that, Step S5 includes: increasing the duration of the second part in equal increments of 20ms.

4. The method for testing voltage sag withstand capability using a partial bisection method according to claim 1, characterized in that, Step S5 further includes: the duration of the second part reaches its maximum value at 2000ms.

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