A system and method for determining the harmonic tolerance level between solid-state switching switches

Abstract

This invention discloses a system and method for determining the interharmonic tolerance level of solid-state switching switches (SSDs), belonging to the field of power supply testing. The method includes: establishing a measurement system; randomly selecting the interharmonic content rate to begin testing for a chosen fundamental voltage value and interharmonic frequency, thus obtaining an initial interval for the interharmonic content rate boundary values; and using a binary search method to find and determine the critical value of the interharmonic content rate that meets the accuracy requirements within the initial interval. This method can quickly and reliably determine the critical value of the interharmonic content rate that causes the same SSD to switch under different fundamental voltage amplitudes and at different frequencies of interharmonics. It effectively measures the interharmonic tolerance level of SSDs and has significant guiding significance for SSD selection and power grid suitability evaluation.

Description

Technical Field

[0001] This invention belongs to the field of power control, and more specifically, relates to a system and method for measuring the harmonic tolerance level between solid-state switching switches. Background Technology

[0002] Dual power supply systems are a means of providing reliable power to loads. Solid-state transfer switches (SSTS) are key devices in dual power supply systems. When a voltage drop exceeds a set value, the SSTS can quickly disconnect the main power supply and then quickly connect the backup power supply. Compared with traditional automatic transfer switches, SSTSs have advantages such as short switching time, high reliability, and no arcing, and therefore have been widely used in recent years. To increase power supply reliability, loads sensitive to voltage sags should be equipped with backup power supplies, and the main and backup power supplies can be quickly switched using SSTSs. When the voltage sag depth exceeds the switching limit set by the SSTS, the SSTS will switch, and the load will switch from the main power supply to the backup power supply. After the sag is eliminated, the SSTS will switch again, switching the load back to the main power supply. However, interharmonics in the power system can cause voltage fluctuations. If the voltage fluctuation amplitude exceeds the switching value set by the SSTS, the SSTS will also switch, disconnecting the main power supply and connecting the backup power supply. The content of interharmonics that trigger SSTS operation varies depending on their frequency. The interharmonic content of the same frequency at different fundamental voltages will cause the SSTS (Security Shielded Switch) to activate at different concentrations. The boundary value of this interharmonic content that triggers SSTS switching is the indicator of the SSTS interharmonic tolerance level. However, the threshold interharmonic content required to trigger SSTS activation varies for different equipment, and currently, there is no specific experimental method for determining this boundary value. Summary of the Invention

[0003] This invention provides a system and method for determining the harmonic tolerance level between solid-state switching switches. It can quickly and accurately determine the harmonic tolerance level between solid-state switching switches, solving the problem that there is currently no accurate method for determining the boundary value of the interharmonic content rate, thus making it impossible to accurately determine the harmonic tolerance level between solid-state switching switches.

[0004] The technical solution of this invention is as follows:

[0005] This invention provides a system for measuring the harmonic tolerance level between solid-state switching switches, comprising:

[0006] Programmable power supply, AC voltage stabilizer, load cabinet, multi-channel data acquisition device, and multiple circuit breakers; among which,

[0007] The programmable power supply, as the main power supply, is connected to the input terminal of the solid-state switching switch to be tested via a circuit breaker.

[0008] The AC regulated power supply is connected as a backup power supply to the input terminal of the solid-state switching switch to be tested via a circuit breaker;

[0009] The load cabinet is connected to the output terminal of the solid-state switching switch to be tested via a circuit breaker;

[0010] The multi-channel data acquisition device is electrically connected to the programmable power supply, the AC regulated power supply and the load cabinet respectively, and can synchronously test and record the voltage and current waveform signals of the programmable power supply, the AC regulated power supply and the load cabinet during the test.

[0011] The present invention also provides a method for determining the harmonic tolerance level between solid-state switching switches using the system described in the present invention, characterized by the following steps:

[0012] Step S1: The interharmonic voltage set by the programmable power supply output of the system is synchronously acquired and recorded by the multi-channel data acquisition device of the system at a preset sampling frequency. The dual power supply voltage on the input side, the load voltage and current on the output side of the solid-state switching switch to be measured are also acquired and recorded.

[0013] Step S2, determine the initial interval of the interharmonic content rate boundary, including:

[0014] Step S21, set the operating mode of the programmable power supply as follows: (1) First output a fundamental voltage with a duration of a preset duration and an effective value equal to the effective value U0 of the AC regulated power supply voltage; (2) Then output an interharmonic voltage with a duration of not less than the preset duration, which is a fundamental voltage superimposed with an interharmonic, and the frequency of the superimposed interharmonic is f. ih The initial value of the interharmonic content is IHRU, and the initial value of the interharmonic content is arbitrarily given; (3) then restore to the fundamental voltage with an effective value equal to the effective value U0 of the AC regulated power supply voltage;

[0015] Step S22, Determine the initial interval of the interharmonic content rate boundary: After turning on the programmable power supply, operate the programmable power supply according to the operating mode set in step S21, change the interharmonic content rate of the frequency superimposed on the fundamental voltage, and determine whether the state of the solid-state switch under test has switched based on the change value of the input current amplitude collected by the multi-channel data acquisition device. Based on the interharmonic content rate corresponding to the switching state of the solid-state switch under test, determine the initial interval of the interharmonic content rate boundary of the state reversal of the solid-state switch under test as [IHRU]. b ,IHRU a ];

[0016] Step S3, based on the identified initial interval, determines the precise value of the interharmonic content rate boundary for the state reversal of the solid-state switching device to be measured, including:

[0017] Step S31, use the binary search method according to formula (1) Calculate the original median value IHRU of the initial interval. m According to formula (2) The original intermediate value IHRU m The ratio of the minimum step size Δ of the harmonic content of the programmable power supply regulation is rounded down and restored to obtain the rounded intermediate value IHRU. r Then, the rounded intermediate value IHRU is superimposed on the fundamental voltage output to the programmable power supply. r If the state switching of the solid-state switch to be measured is to be changed, then the rounded-down intermediate value IHRU should be used. r The new upper limit value and the initial lower limit value form a new interval; if the state of the solid-state switch to be measured has not switched, then the rounded intermediate value IHRU is used. r The new lower limit and the initial upper limit together form a new interval;

[0018] Step S32: Calculate the difference between the upper and lower limits of the new interval, and determine whether the difference reaches the minimum step size Δ of the harmonic content rate between programmable power supply superposition. If so, confirm that the lower limit of the new interval is the frequency f. ih Find the precise critical value of the interharmonic content rate of the solid-state switching switch under the fundamental voltage U0 condition, and end the search. If not, repeat step S31.

[0019] Compared with existing technologies, the system and method for measuring the harmonic tolerance level between solid-state switching devices provided by this invention have at least the following advantages:

[0020] By utilizing a measurement system, a programmable power supply (actually the main power source) alternately applies normal fundamental voltage and interharmonic voltage to the solid-state switching switch (SSD) under test. Data is collected and recorded using a multi-channel data acquisition device to coarsely determine the initial range of the interharmonic content boundary. Then, a binary search method is used to finely adjust this initial range to obtain the precise critical value of the interharmonic content of the SSD, thereby determining its interharmonic tolerance level. This method can quickly and reliably determine the critical value of the interharmonic content that causes the same SSD to switch under different fundamental voltage amplitudes and frequencies of interharmonics. It effectively measures the interharmonic tolerance level of SSDs and has significant guiding significance for SSD selection and grid suitability evaluation. Attached Figure Description

[0021] The accompanying drawings used in the following description of the embodiments are briefly introduced. These drawings are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the system for measuring the harmonic tolerance level between solid-state switching switches according to the present invention.

[0023] Figure 2 This is a flowchart of the method for determining the harmonic tolerance level between solid-state switching switches according to the present invention.

[0024] Figure 3 This is a schematic diagram of the output interharmonic superposition fundamental voltage waveform for controlling the programmable power supply settings according to the present invention.

[0025] Figure 4 This is a schematic diagram of the critical interharmonic content affecting the switching of solid-state switching switches in the method for determining the interharmonic tolerance level of solid-state switching switches according to the present invention.

[0026] Figure 5 This is a graph showing the trend of interharmonic critical content of solid-state switching switches under different fundamental voltages in the method for determining the interharmonic tolerance level of solid-state switching switches according to the present invention. Detailed Implementation

[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, making the above and other objects, features, and advantages of the present invention clearer. In all the drawings, the same reference numerals indicate the same parts. The drawings are not intentionally drawn to scale; the focus is on illustrating the main points of the invention.

[0028] refer to Figure 2 This invention provides a system for measuring the harmonic tolerance level between solid-state switching switches, comprising:

[0029] Programmable power supply, AC voltage stabilizer, load cabinet, multi-channel data acquisition device, and multiple circuit breakers; among which,

[0030] The programmable power supply, as the main power supply, is connected to the input terminal of the solid-state switching switch to be tested via a circuit breaker.

[0031] The AC regulated power supply is connected as a backup power supply to the input terminal of the solid-state switching switch to be tested via a circuit breaker;

[0032] The load cabinet is connected to the output terminal of the solid-state switching switch to be tested via a circuit breaker.

[0033] The multi-channel data acquisition device is electrically connected to the programmable power supply, the AC regulated power supply and the load cabinet respectively, and can synchronously test and record the voltage and current waveform signals of the programmable power supply, the AC regulated power supply and the load cabinet during the test.

[0034] In the above system, the load cabinet is a load cabinet that meets the rated power of the solid-state switching switch to be measured, and the power factor of the load cabinet is 1 or 0.8.

[0035] refer to Figure 2 The present invention also provides a method for determining the harmonic tolerance level between solid-state switching switches using the above system, the steps of which are as follows:

[0036] Step S1: The interharmonic voltage set by the programmable power supply output of the system is synchronously acquired and recorded by the multi-channel data acquisition device of the system at a preset sampling frequency. The dual power supply voltage on the input side, the load voltage and current on the output side of the solid-state switching switch to be measured are also acquired and recorded.

[0037] Step S2, determine the initial interval of the interharmonic content rate boundary, including:

[0038] Step S21, set the operating mode of the programmable power supply as follows: (1) First output a fundamental voltage with a duration of a preset duration and an effective value equal to the effective value U0 of the AC regulated power supply voltage; (2) Then output an interharmonic voltage with a duration of not less than the preset duration, which is a fundamental voltage superimposed with an interharmonic, and the frequency of the superimposed interharmonic is f. ih The initial value of the interharmonic content is IHRU, and the initial value of the interharmonic content is arbitrarily given; (3) then restore to the fundamental voltage with an effective value equal to the effective value U0 of the AC regulated power supply voltage;

[0039] Step S22, Determine the initial interval of the interharmonic content rate boundary: After turning on the programmable power supply, operate the programmable power supply according to the operating mode set in step S21, change the interharmonic content rate of the frequency superimposed on the fundamental voltage, and determine whether the state of the solid-state switch under test has switched based on the change value of the input current amplitude collected by the multi-channel data acquisition device. Based on the interharmonic content rate corresponding to the switching state of the solid-state switch under test, determine the initial interval of the interharmonic content rate boundary of the state reversal of the solid-state switch under test as [IHRU]. b ,IHRU a ];

[0040] Step S3, determine the precise value of the interharmonic content rate boundary based on the initial interval of the interharmonic content rate boundary of the solid-state switching state reversal to be measured, including:

[0041] Step S31, use the binary search method according to formula (1) Calculate the original median value IHRU of the initial interval. m According to formula (2) The original intermediate value IHRU m The ratio of the minimum step size Δ of the harmonic content of the programmable power supply regulation is rounded down and restored to obtain the rounded intermediate value IHRU. r Then, the rounded intermediate value IHRU is superimposed on the fundamental voltage output to the programmable power supply. r If the state switching of the solid-state switch to be measured is to be changed, then the rounded-down intermediate value IHRU should be used. r The new upper limit value and the initial lower limit value form a new interval; if the state of the solid-state switch to be measured has not switched, then the rounded intermediate value IHRU is used. r The new lower limit and the initial upper limit together form a new interval;

[0042] Step S32: Calculate the difference between the upper and lower limits of the new interval, and determine whether the difference reaches the minimum step size Δ of the harmonic content rate between programmable power supply superposition. If so, confirm that the lower limit of the new interval is the frequency f. ih Find the precise critical value of the interharmonic content rate of the solid-state switching switch under the fundamental voltage U0 condition, and end the search. If not, repeat step S31.

[0043] In step S2 of the above method, the interharmonic content of the superimposed frequency is changed in the following manner: the change value of the input current amplitude collected by the multi-channel data acquisition device is used to determine whether the state of the solid-state switch to be measured has switched; based on the interharmonic content corresponding to the switching state of the solid-state switch to be measured, the initial interval of the interharmonic content boundary of the state reversal of the solid-state switch to be measured is found, including:

[0044] (1) If the state of the solid-state switching switch to be measured changes from the main power supply to the backup power supply after the initial interharmonic is superimposed on the fundamental voltage, the content of the interharmonic at that frequency is reduced by 2% at intervals, and M = 0, N = 1; If the state of the solid-state switching switch to be measured does not change from the main power supply to the backup power supply after the initial interharmonic is superimposed, the content of the interharmonic at that frequency is increased by 2% at intervals, and N = 0, M = 1; M is a counter for the number of times the interharmonic content is increased, and N is a counter for the number of times the interharmonic content is decreased. The initial values ​​of M and N are both 0.

[0045] (2) During the process of superimposing interharmonics on the fundamental voltage after the first time, if N > 0, the content of the interharmonics at this frequency continues to decrease at intervals of 2% until the state of the solid-state switching switch to be measured has not been switched from the main power supply to the backup power supply. During this process, let M = 0 remain unchanged and N = N + 1; if M > 0, the content of the interharmonics at this frequency continues to increase at intervals of 2% until the state of the solid-state switching switch to be measured has been switched from the main power supply to the backup power supply. During this process, let N = 0 remain unchanged and M = M + 1.

[0046] (3) During the superposition of interharmonics to the fundamental voltage after the first time, if the state of the solid-state switching switch to be measured has not switched from the main power supply to the backup power supply, and N = 0, it indicates that the SSTS has not undergone state reversal; if N > 0, it indicates that the state of the solid-state switching switch to be measured has reversed from switching to non-switching. Then, the current interharmonic content is used as the lower limit of the initial interval IHRU. b The harmonic content between the previous states is used as the upper limit of the initial interval IHRU. a The lower bound of the initial interval IHRU b The upper limit of the initial interval IHRU a The initial interval for the interharmonic content boundary of the solid-state switching switch state reversal is determined. When the solid-state switching switch state changes from main power to backup power, if M = 0, it indicates that the solid-state switching switch state has not reversed; if M > 0, it indicates that the solid-state switching switch state has reversed from not switching to switching. The current interharmonic content is then used as the upper limit of the initial interval IHRU. a The harmonic content between the previous states is used as the lower limit of the initial interval IHRU. b The lower bound of the initial interval IHRU b The upper limit of the initial interval IHRU a The initial interval of the interharmonic content rate boundary of the state reversal of the solid-state switching switch to be measured is determined.

[0047] In step S2 of the above method, the preset duration is 0.4s;

[0048] The sampling frequency of the multi-channel data acquisition device is not less than 12.8 kHz.

[0049] In step S1 of the above method, the switching voltage of the solid-state switching switch to be measured is set to kU0, where U0 is the effective value of the AC regulated power supply voltage, and k takes the value of: k≤0.9 or k≥0.1.

[0050] In step S3 of the above method, the intermediate value IHRU is rounded down. rThis is an integer multiple of the minimum interharmonic adjustment step size Δ of the programmable power supply. This is because programmable power supplies have a minimum interharmonic adjustment step size limit; the interharmonic content after binary division may not be output. It needs to be rounded according to its minimum compensation before the power supply is set to output the value. This refers to using the rounded intermediate value IHRU. m Use this setting to configure the programmable power supply output value.

[0051] refer to Figure 2 It can be seen that the above method can determine the critical value of the harmonic content of a solid-state switching switch at different frequencies, that is, by changing the interharmonic frequency f. ih By repeating steps S2 to S3 of the above method, the critical value of the interharmonic content rate corresponding to the switching of the solid-state switching caused by different frequency interharmonics can be measured under the same fundamental voltage U0.

[0052] The above method can also determine the critical value of the interharmonic content of the solid-state switching switch at the same frequency under different fundamental voltage values. That is, by changing the fundamental voltage value U and repeating steps S2 to S4 of the above method, the critical value of the interharmonic content corresponding to the switching of the solid-state switching switch caused by the interharmonic at the same frequency under different fundamental voltage values ​​can be obtained.

[0053] The embodiments of the present invention will be further described below with reference to the accompanying drawings. It should also be noted that any parts not described in detail below are understood to be well-known in the art.

[0054] Example 1

[0055] refer to Figure 2 The method for determining the harmonic tolerance level between solid-state switching switches in this embodiment is as follows, including:

[0056] Step S1: First, establish a measurement system, referring to... Figure 1 As shown, the measurement system consists of a programmable power supply, an AC regulated power supply, the SSTS to be measured, a load cabinet, a multi-channel data acquisition device, and test auxiliary accessories.

[0057] In the above system, a programmable power supply (main power supply) and a regulated power supply (backup power supply) are connected to the input terminal of the SSTS to be tested via a circuit breaker. At its output terminal, a load cabinet that meets the rated power of the SSTS is connected via a circuit breaker. The power factor of the load cabinet can be 1 or 0.8. At the same time, a multi-channel data acquisition device is used to simultaneously test and record the voltage and current waveform signals of the two power supplies and the load side during the test process.

[0058] In the above system, the programmable power supply is used to output a set interharmonic voltage, that is, to output a voltage consisting of "fundamental frequency + constant interharmonic voltage of a set frequency". The multi-channel data acquisition device has a multi-channel synchronous data acquisition and recording function, which can simultaneously record the dual power supply voltages input to the SSTS, as well as the output voltage and current, with a sampling frequency of not less than 12.8kHz.

[0059] In the above system, if the effective value of the regulated power supply voltage is U0, the switching voltage of the SSTS is set to kU0, and k is generally taken as k≤0.9 or k≥1.1.

[0060] Step S2, determine the initial interval (coarse adjustment) of the interharmonic content rate boundary:

[0061] In step 2 above, the programmable power supply first outputs a fundamental voltage with an effective value of U0 for a duration of 0.4s, then outputs a "fundamental + interharmonic" voltage for a duration of not less than 0.4s, and then returns to outputting only the fundamental voltage U0. The superimposed interharmonic frequency is f. ih Its initial content is IHRU, and the waveform is as follows: Figure 3 As shown.

[0062] The initial value of the interharmonic content superimposed on the fundamental frequency is arbitrarily given. After the programmable power supply is turned on, the change in current amplitude acquired by the multi-channel data acquisition device is used to determine whether the SSTS state has switched. An interharmonic content increment counter M and a decrement counter N are set, both initially set to 0. The interharmonic content superimposed at this frequency is changed to find the initial interval for state reversal, as detailed below:

[0063] (1) If the SSTS switches from the main power supply to the backup power supply after the initial interharmonic is superimposed, the content of the interharmonic at that frequency is reduced by 2% at intervals, M=0, N=1. If the SSTS does not switch from the main power supply to the backup power supply after the initial interharmonic is superimposed, the content of the interharmonic at that frequency is increased by 2% at intervals, N=0, M=1.

[0064] (2) During the superposition process after the first time, if N > 0, the content of the inter-harmonic at that frequency continues to decrease at intervals of 2% until the SSTS ends before switching from the main power supply to the backup power supply. During this process, M = 0 remains unchanged, and N = N + 1. If M > 0, the content of the inter-harmonic at that frequency continues to increase at intervals of 2% until the SSTS ends before switching from the main power supply to the backup power supply. During this process, N = 0 remains unchanged, and M = M + 1.

[0065] (3) During the superposition process after the first time, if the SSTS does not switch from the main power supply to the backup power supply, and N = 0, it means that the SSTS has not undergone a state flip; if N > 0, it means that the state change of the SSTS has changed from switching to no switching. Then, the current interharmonic content is used as the lower limit of the interval IHRU. b The harmonic content between the previous states is used as the upper limit of the interval IHRU. a Determine the initial interval. When the SSTS switches from main power to backup power, if M=0, it means the SSTS has not undergone a state transition; if M>0, it means the SSTS has changed from no switching to switching. The current interharmonic content is then used as the upper limit of the interval IHRU. a The harmonic content of the previous state is used as the lower limit of the interval IHRU b Determine the initial interval.

[0066] The terms mentioned above are explained as follows:

[0067] SSTS Status: Whether the SSTS is connected to the main power supply or the backup power supply.

[0068] SSTS Status Switching: The action of SSTS switching from main power to backup power or from backup power to main power.

[0069] SSTS state flip: SSTS changes from state to state without switching or from state without switching to state switching.

[0070] Step S3: Use the binary search method to determine the precise value of the interharmonic content rate boundary (fine-tuning);

[0071] In step S3, the binary search method calculates the original intermediate value IHRU of the interval according to equation (1). m The intermediate value IHRU is obtained by rounding down and restoring the value of the harmonic content between the programmable power supply regulation and the minimum step size Δ. r Then, overlay this value, observe the SSTS switching status, and update the upper and lower limits of the interval.

[0072]

[0073]

[0074] The method for updating the upper and lower limits of the interval is as follows:

[0075] (1) Superimpose a content of IHRU on the fundamental wave r If the SSTS is switched, the intermediate value is updated to the new upper limit of the interval, while the lower limit remains unchanged, thus forming a new interval.

[0076] (2) Superimpose a content of IHRU on the fundamental frequency rIf the SSTS is not switched, the intermediate value is updated to the new lower limit of the interval, while the upper limit remains unchanged, thus forming a new interval.

[0077] In step S3 above, due to the limitation of the minimum adjustment step size of the programmable power supply, the set value must be an integer multiple of it. When performing a binary search, a value smaller than the minimum adjustment step size will appear, so a rounding operation must be performed.

[0078] After determining the new interval, calculate the difference between the upper and lower limits of the new interval. If the difference is determined to reach the minimum step size Δ of the superimposed harmonic content of the programmable power supply, then the lower limit of the new interval is set as the frequency f. ih The critical content rate of interharmonics under the fundamental voltage U0 condition is determined; otherwise, the bisection method is used to find the boundary value of interharmonics.

[0079] Furthermore, the above method also includes step S4, which uses the above method to determine the critical value of the interharmonic content at different frequencies, specifically by changing the interharmonic frequency f. ih Repeat steps S2 to S3 to obtain the critical content rate corresponding to SSTS switching caused by harmonics at different frequencies under the fundamental voltage U0 condition.

[0080] The above method can also be used to determine the critical values ​​of the interharmonic content rate for different fundamental voltage values. Specifically, by changing the fundamental voltage U and repeating steps S2 to S4, the critical content rate corresponding to the SSTS switching caused by the same frequency interharmonic at different fundamental voltage amplitudes can be obtained.

[0081] Example 2:

[0082] The programmable power supply (main power) and three-phase 380V AC mains power (backup power) are connected to the input of the SSTS via circuit breakers. The output of the SSTS is connected to a load bank capable of handling a maximum load of 400A and 265kW (resistive) via a circuit breaker. A multi-channel data acquisition device is used to simultaneously test and record the voltage and current waveforms of the two power supplies and the load side during the test. The test circuit consists of a programmable power supply, SSTS, load bank, multi-channel data acquisition device, and auxiliary test accessories. The functions of each part are as follows:

[0083] (1) Programmable power supply: used to output a set interharmonic voltage, that is, to output a voltage of "fundamental frequency + constant interharmonic of set frequency" ( Figure 3 ).

[0084] (2) SSTS: This test uses a certain brand of three-phase integrated SSTS as the object, with a rated capacity of 400A and a set switching threshold of 216V.

[0085] (3) Multi-channel data acquisition device: It has the function of synchronous data acquisition and recording of multiple channels, and can synchronously record the dual power supply voltage of SSTS input as well as the output voltage and current, with a sampling frequency of not less than 12.8kHz.

[0086] (i) The experimental results of determining the critical SSTS switching content of harmonics at different frequencies using the system and method of the present invention are as follows:

[0087] The switching threshold voltage of a certain brand of SSTS tested was 216V. The main power supply side was a programmable power supply with an effective value of 230V for its output fundamental voltage. At this time, according to... Figure 2 The test procedure was based on 50Hz, and interharmonic frequencies of 35Hz, 40Hz, 45Hz, 47Hz, 49Hz, 51Hz, 53Hz, 55Hz, 60Hz, and 65Hz were selected to test the critical content rate that caused SSTS switching. The test results are shown in Table 1.

[0088] Table 1. Critical content of interharmonics at a fundamental voltage of 230V.

[0089] Interharmonic frequency / Hz 35 40 45 47 49 51 53 55 60 65 Critical content / % 7.1 6.3 6.0 5.9 5.6 5.8 6.0 6.1 6.4 7.1

[0090] Based on Table 1, plot the curves showing the effect of interharmonics on the SSTS in this experiment, as shown below. Figure 4 As shown, this illustrates that low-frequency interharmonics in the power grid can affect the switching of SSTS.

[0091] (II) The experimental results of determining the critical interharmonic content of SSTS switching corresponding to different fundamental voltages using the system and method of the present invention are as follows:

[0092] The switching threshold voltage of a certain brand of SSTS tested was 216V. The main power supply side was a programmable power supply, and its effective output fundamental voltage was set to 220V, 225V, 230V, and 235V respectively. Figure 2 The experimental procedure was to test the critical content rate of SSTS switching caused by interharmonics with frequencies of 35Hz and 45Hz under different fundamental voltage amplitudes. The results are shown in Table 2.

[0093] Table 1. Critical Interharmonic Content at Different Fundamental Voltages

[0094]

[0095] Table 2 shows the trend of the critical content of harmonics at the same frequency under different fundamental voltage conditions in this experiment. Figure 5 As shown.

[0096] The parts not described in detail in the above embodiments can be understood as knowledge known to those skilled in the art.

[0097] Those skilled in the art will understand that the scope of protection of this invention is not limited to the preferred embodiments described above. Any variations and substitutions that can be easily conceived by those skilled in the art based on the technical content disclosed in this invention should fall within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A method for determining the harmonic tolerance level between solid-state switching switches, characterized in that it is used for... A system for determining the harmonic tolerance level between solid-state switching switches includes: a programmable power supply, an AC regulated power supply, a load cabinet, a multi-channel data acquisition device, and multiple circuit breakers. The programmable power supply serves as the main power supply and is connected to the input terminal of the solid-state switching switch under test via circuit breakers. The AC regulated power supply serves as a backup power supply and is connected to the input terminal of the solid-state switching switch under test via circuit breakers. The load cabinet is connected to the output terminal of the solid-state switching switch under test via circuit breakers. The multi-channel data acquisition device is electrically connected to the programmable power supply, the AC regulated power supply, and the load cabinet, and can simultaneously test and record the voltage and current waveform signals of the programmable power supply, the AC regulated power supply, and the load cabinet during the test. The method steps are as follows: Step S1: The interharmonic voltage set by the programmable power supply output of the system is synchronously acquired and recorded by the multi-channel data acquisition device of the system at a preset sampling frequency. The dual power supply voltage on the input side, the load voltage and current on the output side of the solid-state switching switch to be measured are also acquired and recorded. Step S2, determine the initial interval of the interharmonic content rate boundary, including: Step S21, set the operating mode of the programmable power supply as follows: (1) First output a fundamental voltage with a duration of a preset duration and an effective value equal to the effective value U0 of the AC regulated power supply voltage; (2) Then output an interharmonic voltage with a duration of not less than the preset duration, which is a fundamental voltage superimposed with an interharmonic, and the frequency of the superimposed interharmonic is f. ih The initial value of the interharmonic content is IHRU, and the initial value of the interharmonic content is arbitrarily given; (3) then restore to the fundamental voltage with an effective value equal to the effective value U0 of the AC regulated power supply voltage; Step S22, Determine the initial interval of the interharmonic content rate boundary: After turning on the programmable power supply, operate the programmable power supply according to the operating mode set in step S21, change the interharmonic content rate of the frequency superimposed on the fundamental voltage, and determine whether the state of the solid-state switch under test has switched based on the change value of the input current amplitude collected by the multi-channel data acquisition device. Based on the interharmonic content rate corresponding to the switching state of the solid-state switch under test, determine the initial interval of the interharmonic content rate boundary of the state reversal of the solid-state switch under test as [IHRU]. b ,IHRU a ]; Step S3, based on the identified initial interval, determines the precise value of the interharmonic content rate boundary for the state reversal of the solid-state switching device to be measured, including: Step S31, use the binary search method according to formula (1) Calculate the original median value IHRU of the initial interval. m According to formula (2) The original intermediate value IHRU m The ratio of the minimum step size Δ of the harmonic content of the programmable power supply regulation is rounded down and restored to obtain the rounded intermediate value IHRU. r Then, the rounded intermediate value IHRU is superimposed on the fundamental voltage output to the programmable power supply. r If the state switching of the solid-state switch to be measured is to be changed, then the rounded-down intermediate value IHRU should be used. r The new upper limit value and the initial lower limit value form a new interval; if the state of the solid-state switch to be measured has not switched, then the rounded intermediate value IHRU is used. r The new lower limit and the initial upper limit together form a new interval; Step S32: Calculate the difference between the upper and lower limits of the new interval, and determine whether the difference reaches the minimum step size Δ of the harmonic content rate between programmable power supply superposition. If so, confirm that the lower limit of the new interval is the frequency f. ih Find the precise critical value of the interharmonic content rate of the solid-state switching switch under the fundamental voltage U0 condition, and end the search. If not, repeat step S31.

2. The method for determining the harmonic tolerance level between solid-state switching switches according to claim 1, characterized in that, In step S2, the interharmonic content of the superimposed frequency is changed in the following manner: the change value of the input current amplitude collected by the multi-channel data acquisition device is used to determine whether the state of the solid-state switch to be measured has switched; based on the interharmonic content corresponding to the switching state of the solid-state switch to be measured, the initial interval of the interharmonic content boundary of the state reversal of the solid-state switch to be measured is found, including: (1) If the state of the solid-state switching switch to be measured changes from the main power supply to the backup power supply after the initial interharmonic is superimposed on the fundamental voltage, the content of the interharmonic at that frequency is reduced at intervals of 2%, and M=0, N=1; If the state of the solid-state switching switch to be measured does not change from the main power supply to the backup power supply after the initial interharmonic is superimposed, the content of the interharmonic at that frequency is increased at intervals of 2%, and N=0, M=1; M is a counter for setting the number of times the interharmonic content is increased, and N is a counter for setting the number of times the interharmonic content is decreased. The initial values ​​of M and N are both 0. (2) During the process of superimposing interharmonics on the fundamental voltage after the first time, if N>0, the content of the interharmonics at this frequency continues to decrease at intervals of 2% until the state of the solid-state switching switch to be measured has not been switched from the main power supply to the backup power supply. During this process, let M=0 remain unchanged and N=N+1; if M>0, the content of the interharmonics at this frequency continues to increase at intervals of 2% until the state of the solid-state switching switch to be measured has been switched from the main power supply to the backup power supply. During this process, let N=0 remain unchanged and M=M+1. (3) During the superposition of interharmonics to the fundamental voltage after the first time, if the state of the solid-state switching switch to be measured has not switched from the main power supply to the backup power supply, and N=0, it indicates that the SSTS has not undergone state reversal; if N>0, it indicates that the state of the solid-state switching switch to be measured has reversed from switching to non-switching. Then, the current interharmonic content is used as the lower limit of the initial interval IHRU. b The harmonic content between the previous states is used as the upper limit of the initial interval IHRU. a The lower bound of the initial interval IHRU b The upper limit of the initial interval IHRU a The initial interval for the interharmonic content boundary of the solid-state switching switch state reversal is determined. When the solid-state switching switch state changes from main power to backup power, if M=0, it indicates that the solid-state switching switch state has not reversed; if M>0, it indicates that the solid-state switching switch state has reversed from not switching to switching. Then, the current interharmonic content is used as the upper limit of the initial interval IHRU. a The harmonic content between the previous states is used as the lower limit of the initial interval IHRU. b The lower bound of the initial interval IHRU b The upper limit of the initial interval IHRU a The initial interval of the interharmonic content rate boundary of the state reversal of the solid-state switching switch to be measured is determined.

3. The method for determining the harmonic tolerance level between solid-state switching switches according to any one of claims 1 to 2, characterized in that, In step S1, the switching voltage of the solid-state switching switch to be measured is set to kU0, where U0 is the effective value of the AC regulated power supply voltage, and k takes the value of: k≤0.9 or k≥0.

1.

4. The method for determining the harmonic tolerance level between solid-state switching switches according to claim 1, characterized in that, In step S3, the intermediate value IHRU is rounded down. r It is an integer multiple of the minimum interharmonic adjustment step size Δ of the programmable power supply.

5. The method for determining the harmonic tolerance level between solid-state switching switches according to claim 1, characterized in that, The load cabinet is a load cabinet that meets the rated power of the solid-state switching switch to be measured, and the power factor of the load cabinet is 1 or 0.8.

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