Variable frequency power supply protection method and system based on voltage mutation detection

Abstract

The present invention relates to the field of test power supply protection, and discloses a variable frequency power supply protection method and system based on voltage mutation detection, including the following steps: matching the characteristics of the variable frequency power supply and the power supply network, constructing a target variable frequency power supply control system, and performing no-load operation and load optimization on the target variable frequency power supply in the target variable frequency control system to obtain a variable frequency power supply that meets the requirements; performing a load test on the variable frequency power supply, judging whether there is a voltage mutation based on the output voltage of the test result, tracing the cause of the voltage mutation, and performing voltage mutation protection on the variable frequency power supply based on the cause of the voltage mutation. The present invention realizes no-load testing and gradual loading testing of the variable frequency power supply, and traces the situation where the variable frequency power supply may have a voltage mutation based on the test results, and finally realizes voltage mutation protection, ensuring the connection stability and reliability between the variable frequency power supplies.

Description

Technical Field

[0001] The invention relates to the field of power supply protection, and in particular to a variable frequency power supply protection method based on voltage mutation detection. Background Art

[0002] A variable frequency power supply is a power supply device that converts AC power in the mains into DC power and further outputs it as adjustable variable frequency AC power. Its working principle is mainly based on power electronics technology. Through rectification, inversion, control and filtering, it realizes the transformation and adjustment of the input voltage to output AC power of the required frequency and voltage. When the power supply voltage is unstable, the variable frequency power supply is prone to voltage mutation, or when the internal capacitor capacity is insufficient or the internal components of the inverter are aging, voltage mutation may also occur. Environmental factors and load factors are also the main causes of voltage mutation. There are various loads in the power supply network, and the frequency and voltage requirements of the power supply are different. By adjusting the output frequency and voltage, the variable frequency power supply can flexibly adapt to the needs of different loads and ensure the stable operation of the power supply network. At the same time, after the variable frequency power supply is connected to the power supply network, it can determine whether it will have a voltage mutation and provide corresponding protection when a voltage mutation occurs, thereby improving the power supply quality, achieving energy saving and consumption reduction, promoting the application of renewable energy, and improving the flexibility and reliability of the power supply network. Summary of the invention

[0003] The present invention overcomes the deficiencies of the prior art and provides a variable frequency power supply protection method and system based on voltage mutation detection.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A first aspect of the present invention provides a variable frequency power supply protection method based on voltage mutation detection, comprising the following steps:

[0006] Connecting the target variable frequency power supply to the target power supply network, and matching the characteristics of the target variable frequency power supply and the target power supply network to obtain a target variable frequency power supply control system;

[0007] The target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, and the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply;

[0008] Perform a step-by-step loading test on the qualified no-load variable frequency power supply, use the wavelet transform algorithm to monitor the voltage mutation of the no-load qualified variable frequency power supply during the step-by-step loading test, and trace the voltage mutation of the no-load qualified variable frequency power supply that generates the voltage mutation;

[0009] Based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, voltage mutation protection is performed on the no-load qualified variable frequency power supply.

[0010] Furthermore, in a preferred embodiment of the present invention, the target variable frequency power supply is connected to the target power supply network, and the target variable frequency power supply and the target power supply network are matched with each other to obtain a target variable frequency power supply control system, specifically:

[0011] The variable frequency power supply that needs to be tested for voltage mutation is calibrated as the target variable frequency power supply, and the rated input voltage, rated output voltage, rated capacity, rated operating frequency and operating frequency range of the variable frequency power supply are obtained;

[0012] Obtain a power supply network whose voltage level covers the rated input voltage and rated output voltage of the variable frequency power supply, mark it as a target power supply network, and obtain a supported power supply network frequency range on the target power supply network;

[0013] Analyze whether the rated operating frequency of the target variable frequency power supply is within the power supply network frequency range supported by the target power supply network. If so, directly connect the target variable frequency power supply to the target power supply network to obtain the target variable frequency power supply control system;

[0014] If not, connecting the target variable frequency power supply to the target power supply network and obtaining a synchronous converter, wherein the synchronous converter is capable of adjusting the frequency of the target variable frequency power supply;

[0015] Within the operating frequency range of the target variable frequency power supply, the frequency of the target variable frequency power supply is adjusted based on the synchronous converter so that the operating frequency of the target variable frequency power supply is maintained within the power supply network frequency range supported by the target power supply network, thereby obtaining a target variable frequency power supply control system.

[0016] Further, in a preferred embodiment of the present invention, the target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, and the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply, specifically:

[0017] A voltage sensor and an oscilloscope are connected to the target variable frequency power supply, wherein the voltage sensor can monitor the voltage value of the target variable frequency power supply in real time during the operation of the target variable frequency power supply, and the oscilloscope can output the voltage value of the target variable frequency power supply obtained by real-time monitoring in the form of a waveform signal;

[0018] Controlling the target variable frequency voltage to operate at no load in the target variable frequency power supply control system, and monitoring the output voltage value of the target variable frequency power supply at no load based on the voltage sensor, and converting the output voltage value of the target variable frequency power supply at no load based on the oscilloscope into a waveform signal, which is calibrated as a no-load voltage waveform signal;

[0019] Based on the rated input voltage and rated output voltage of the target variable frequency power supply, a standard fluctuation range of the no-load voltage waveform signal of the target variable frequency power supply is preset, and a waveform signal analysis is performed on the no-load voltage waveform signal to obtain an actual fluctuation range of the no-load voltage waveform signal;

[0020] If the actual fluctuation range of the no-load voltage waveform signal is maintained within the fluctuation standard range of the no-load voltage waveform signal, the target variable frequency power supply is calibrated as a no-load qualified variable frequency power supply;

[0021] If the actual fluctuation range of the no-load voltage waveform signal does not remain within the fluctuation standard range of the no-load voltage waveform signal, the working parameters of different components in the control circuit of the target variable frequency power supply when running at no load are obtained, and the Markov chain algorithm is introduced to analyze the working parameters of different components in the control circuit of the target variable frequency power supply when running at no load, and the abnormal state transition probability values ​​of different components in the control circuit of the target variable frequency power supply are calculated;

[0022] The components whose abnormal state transfer probability value is greater than the preset value are calibrated as a type of abnormal components, and the type of abnormal components are replaced. If the actual fluctuation range of the no-load voltage waveform signal is still not maintained within the standard fluctuation range of the no-load voltage waveform signal after the type of abnormal components are replaced, a power supply filter is introduced and operated at the input end of the variable frequency power supply to maintain the actual fluctuation range of the no-load voltage waveform signal within the standard fluctuation range of the no-load voltage waveform signal, so as to obtain a no-load qualified variable frequency power supply.

[0023] Further, in a preferred embodiment of the present invention, the no-load qualified variable frequency power supply is subjected to a stepwise loading test, and a wavelet transform algorithm is used to monitor the voltage mutation of the no-load qualified variable frequency power supply subjected to the stepwise loading test, and the voltage mutation of the no-load qualified variable frequency power supply that generates the voltage mutation is traced, specifically:

[0024] In the target variable frequency power supply control system, the load level range supported by the target power supply network is obtained and calibrated as the load level range supported by the target power supply network;

[0025] In the target variable frequency power supply control system, based on the load level range supported by the target power supply network, a step-by-step loading test is performed on the no-load qualified variable frequency power supply, wherein the step-by-step loading test is to gradually increase the load level at the input end of the no-load qualified variable frequency power supply, and calculate the output voltage value of the no-load qualified variable frequency power supply at different load levels;

[0026] During the step-by-step loading test of the no-load qualified variable frequency power supply, the waveform signal of the output voltage value of the no-load qualified variable frequency power supply at a single load level is calibrated as the load voltage waveform signal based on an oscilloscope;

[0027] Introducing a wavelet transform algorithm, wherein the wavelet transform algorithm can perform sampling processing on the load voltage waveform signal and calculate the wavelet coefficients of the sampling points after the sampling processing;

[0028] Based on the wavelet transform algorithm, the load voltage waveform signal is subjected to wavelet transform to obtain wavelet coefficients of the load voltage waveform signal at different sampling points, and standard thresholds of wavelet coefficients of the load voltage waveform signal at different sampling points are preset;

[0029] If the absolute value of the wavelet coefficient of the load voltage waveform signal at a sampling point is greater than the standard threshold of the wavelet coefficient of the load voltage waveform signal at the corresponding sampling point, the corresponding sampling point is calibrated as a mutation sampling point;

[0030] If there is no sudden change sampling point when the no-load qualified variable frequency power supply is running at all load levels, the no-load qualified variable frequency power supply is calibrated as a qualified variable frequency power supply;

[0031] If there is a load level that causes a sudden change sampling point when the no-load qualified variable frequency power supply is running, the no-load qualified variable frequency power supply will be calibrated as an unqualified variable frequency power supply, and the corresponding load level will be calibrated as an abnormal load level, and the load level without a sudden change sampling point will be calibrated as a normal load level;

[0032] Based on the abnormal load level and the normal load level, and in combination with the surrounding environmental factors of the unqualified variable frequency power supply, the voltage mutation of the unqualified variable frequency power supply is traced to the source.

[0033] Further, in a preferred embodiment of the present invention, based on the abnormal load level and the normal load level, and in combination with the surrounding environmental factors of the unqualified variable frequency power supply, the voltage mutation traceability of the unqualified variable frequency power supply is performed, specifically:

[0034] Determine whether the unqualified variable frequency power supply has changed from a normal load level to an abnormal load level during operation;

[0035] If so, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as the load change reason;

[0036] If not, the surrounding environmental factors of the unqualified variable frequency power supply are obtained and calibrated as a type of environmental factors, wherein the type of environmental factors include the working environment temperature and surrounding electromagnetic interference intensity of the unqualified variable frequency power supply;

[0037] Obtaining instructions for use of the unqualified variable frequency power supply, and based on the instructions for use of the unqualified variable frequency power supply, obtaining a tolerable working environment temperature threshold and a tolerable surrounding electromagnetic interference intensity threshold of the unqualified variable frequency power supply;

[0038] If the working environment temperature and the surrounding electromagnetic interference intensity of the unqualified variable frequency power supply are not maintained within the tolerable working environment temperature threshold and the tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as an environmental impact reason;

[0039] If the working environment temperature and the surrounding electromagnetic interference intensity of the unqualified variable frequency power supply are maintained within the tolerable working environment temperature threshold and the tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is assessed as its own reason.

[0040] Further, in a preferred embodiment of the present invention, based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, voltage mutation protection is performed on the no-load qualified variable frequency power supply, specifically:

[0041] Introducing a voltage mutation protection mechanism in the target variable frequency power supply control system, wherein the voltage mutation protection mechanism can disconnect the no-load qualified variable frequency power supply from the target power supply network;

[0042] When the no-load qualified variable frequency power supply is marked as an unqualified variable frequency power supply, based on the voltage mutation protection mechanism, the unqualified variable frequency power supply is controlled to be disconnected from the target power supply network in the target variable frequency power supply control system;

[0043] When the unqualified variable frequency power supply is disconnected from the target power supply network, the reasons why the no-load qualified variable frequency power supply is marked as an unqualified variable frequency power supply are analyzed;

[0044] If the reason is a load change reason, a connection circuit between the unqualified variable frequency power supply and the target power supply network is obtained, and a big data network is obtained. Based on the big data network, all schemes of parallel buffer circuits in the connection circuit between the unqualified variable frequency power supply and the target power supply network are retrieved and marked as the first protection scheme, wherein the buffer circuit can smooth the rate at which the normal load level changes to the abnormal load level;

[0045] Select a first protection scheme with the highest rate of smoothing the normal load level to the abnormal load level, mark it as a first output protection scheme, output the first output protection scheme, and obtain a qualified variable frequency power supply;

[0046] If the cause is environmental impact, the environmental impact cause is analyzed. If the environmental impact cause is that the working environment temperature is not maintained within the tolerable working environment temperature threshold, a heat sink is connected to the target variable frequency power supply control device to maintain the working environment temperature of the unqualified variable frequency power supply within the tolerable working environment temperature threshold;

[0047] If the environmental impact is caused by the surrounding electromagnetic interference intensity not being maintained within the tolerable surrounding electromagnetic interference intensity threshold, the filter power of the power filter is intelligently adjusted to maintain the surrounding electromagnetic interference intensity within the tolerable surrounding electromagnetic interference intensity threshold;

[0048] If the reason is due to the individual's own fault, the unqualified variable frequency power supply cannot be connected to the target power supply network to form the target variable frequency power supply control device.

[0049] The second aspect of the present invention further provides a variable frequency power supply protection system based on voltage mutation detection, the variable frequency power supply protection system comprising a memory and a processor, the memory storing a variable frequency power supply protection method, and when the variable frequency power supply protection method is executed by the processor, the following steps are implemented:

[0050] Connecting the target variable frequency power supply to the target power supply network, and matching the characteristics of the target variable frequency power supply and the target power supply network to obtain a target variable frequency power supply control system;

[0051] The target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, and the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply;

[0052] Perform a step-by-step loading test on the qualified no-load variable frequency power supply, use the wavelet transform algorithm to monitor the voltage mutation of the no-load qualified variable frequency power supply during the step-by-step loading test, and trace the voltage mutation of the no-load qualified variable frequency power supply that generates the voltage mutation;

[0053] Based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, voltage mutation protection is performed on the no-load qualified variable frequency power supply.

[0054] The present invention solves the technical defects existing in the background technology, and the present invention has the following beneficial effects: matching the characteristics of the variable frequency power supply and the power supply network, constructing a target variable frequency power supply control system, and performing no-load operation and load optimization on the target variable frequency power supply in the target variable frequency control system to obtain a variable frequency power supply that meets the requirements; performing a load test on the variable frequency power supply, judging whether there is a voltage mutation based on the output voltage of the test result, tracing the cause of the voltage mutation, and performing voltage mutation protection on the variable frequency power supply based on the cause of the voltage mutation. The present invention realizes no-load testing and gradual loading testing of the variable frequency power supply, and traces the situation where the variable frequency power supply may have a voltage mutation based on the test results, and finally realizes voltage mutation protection, ensuring the connection stability and reliability between the variable frequency power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying creative work.

[0056] Figure 1 A flow chart of a variable frequency power supply protection method based on voltage mutation detection is shown;

[0057] Figure 2 A flow chart of a method for tracing the source of a voltage mutation on a no-load qualified variable frequency power supply that generates a voltage mutation is shown;

[0058] Figure 3 The program view of the variable frequency power supply protection system based on voltage mutation detection is shown. DETAILED DESCRIPTION

[0059] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0060] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0061] Figure 1 A flow chart of a variable frequency power supply protection method based on voltage mutation detection is shown, comprising the following steps:

[0062] S102: Connecting the target variable frequency power supply to the target power supply network, and matching the characteristics of the target variable frequency power supply and the target power supply network to obtain a target variable frequency power supply control system;

[0063] S104: performing no-load operation on the target variable frequency power supply in the target variable frequency power supply control system, monitoring voltage changes of the target variable frequency power supply based on an oscilloscope during the no-load operation, and optimizing the target variable frequency power supply based on the voltage changes to obtain a no-load qualified variable frequency power supply;

[0064] S106: performing a step-by-step loading test on the no-load qualified variable frequency power supply, using a wavelet transform algorithm to monitor voltage mutations on the no-load qualified variable frequency power supply undergoing the step-by-step loading test, and tracing the source of voltage mutations on the no-load qualified variable frequency power supply that generates voltage mutations;

[0065] S108: Based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, voltage mutation protection is performed on the no-load qualified variable frequency power supply.

[0066] Furthermore, in a preferred embodiment of the present invention, the target variable frequency power supply is connected to the target power supply network, and the target variable frequency power supply and the target power supply network are matched with each other to obtain a target variable frequency power supply control system, specifically:

[0067] The variable frequency power supply that needs to be tested for voltage mutation is calibrated as the target variable frequency power supply, and the rated input voltage, rated output voltage, rated capacity, rated operating frequency and operating frequency range of the variable frequency power supply are obtained;

[0068] Obtain a power supply network whose voltage level covers the rated input voltage and rated output voltage of the variable frequency power supply, mark it as a target power supply network, and obtain a supported power supply network frequency range on the target power supply network;

[0069] Analyze whether the rated operating frequency of the target variable frequency power supply is within the power supply network frequency range supported by the target power supply network. If so, directly connect the target variable frequency power supply to the target power supply network to obtain the target variable frequency power supply control system;

[0070] If not, connecting the target variable frequency power supply to the target power supply network and obtaining a synchronous converter, wherein the synchronous converter is capable of adjusting the frequency of the target variable frequency power supply;

[0071] Within the operating frequency range of the target variable frequency power supply, the frequency of the target variable frequency power supply is adjusted based on the synchronous converter so that the operating frequency of the target variable frequency power supply is maintained within the power supply network frequency range supported by the target power supply network, thereby obtaining a target variable frequency power supply control system.

[0072] It should be noted that to detect whether a voltage mutation occurs in a variable frequency power supply, the variable frequency power supply needs to be connected to the power supply network, and the power supply network applies a load to the variable frequency power supply, so as to determine whether a voltage mutation occurs in the variable frequency power supply during operation. Before access, the target power supply network and the variable frequency power supply need to be paired. If they are directly connected without pairing, it will be impossible to detect whether a voltage mutation occurs in the variable frequency power supply during operation, and it will damage the power supply, causing personal injury and property damage. Pairing the target power supply network and the variable frequency power supply requires that the voltage level of the power supply network covers the rated input voltage and rated output voltage of the variable frequency power supply, otherwise the power supply network does not support the input and output voltages of the variable frequency power supply, which will cause the variable frequency power supply to burn out. At the same time, the operating frequency of the variable frequency power supply needs to be within the operating frequency range supported by the target power supply network. If it is not within the range, the target power supply network cannot be used as the load of the variable frequency power supply to realize the detection of voltage mutation of the variable frequency power supply. The frequency of the target variable frequency power supply can be synchronized by using a synchronous converter, so that the frequency of the target variable frequency power supply and the target power supply network are synchronized, and the two are connected to obtain a control system in which the target power supply network can be used as the load of the variable frequency power supply, and a target variable frequency power supply control system.

[0073] Further, in a preferred embodiment of the present invention, the target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, and the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply, specifically:

[0074] A voltage sensor and an oscilloscope are connected to the target variable frequency power supply, wherein the voltage sensor can monitor the voltage value of the target variable frequency power supply in real time during the operation of the target variable frequency power supply, and the oscilloscope can output the voltage value of the target variable frequency power supply obtained by real-time monitoring in the form of a waveform signal;

[0075] Controlling the target variable frequency voltage to operate at no load in the target variable frequency power supply control system, and monitoring the output voltage value of the target variable frequency power supply at no load based on the voltage sensor, and converting the output voltage value of the target variable frequency power supply at no load based on the oscilloscope into a waveform signal, which is calibrated as a no-load voltage waveform signal;

[0076] Based on the rated input voltage and rated output voltage of the target variable frequency power supply, a standard fluctuation range of the no-load voltage waveform signal of the target variable frequency power supply is preset, and a waveform signal analysis is performed on the no-load voltage waveform signal to obtain an actual fluctuation range of the no-load voltage waveform signal;

[0077] If the actual fluctuation range of the no-load voltage waveform signal is maintained within the fluctuation standard range of the no-load voltage waveform signal, the target variable frequency power supply is calibrated as a no-load qualified variable frequency power supply;

[0078] If the actual fluctuation range of the no-load voltage waveform signal does not remain within the fluctuation standard range of the no-load voltage waveform signal, the working parameters of different components in the control circuit of the target variable frequency power supply when running at no load are obtained, and the Markov chain algorithm is introduced to analyze the working parameters of different components in the control circuit of the target variable frequency power supply when running at no load, and the abnormal state transition probability values ​​of different components in the control circuit of the target variable frequency power supply are calculated;

[0079] The components whose abnormal state transfer probability value is greater than the preset value are calibrated as a type of abnormal components, and the type of abnormal components are replaced. If the actual fluctuation range of the no-load voltage waveform signal is still not maintained within the standard fluctuation range of the no-load voltage waveform signal after the type of abnormal components are replaced, a power supply filter is introduced and operated at the input end of the variable frequency power supply to maintain the actual fluctuation range of the no-load voltage waveform signal within the standard fluctuation range of the no-load voltage waveform signal, so as to obtain a no-load qualified variable frequency power supply.

[0080] It should be noted that the purpose of detecting the voltage value of the target variable frequency power supply under no-load condition is to ensure whether the output voltage and frequency of the target variable frequency power supply are stable. If the target variable frequency power supply is not stable under no-load condition, the target variable frequency power supply will be more unstable if a load is applied to the target variable frequency power supply. After the voltage value of the target variable frequency power supply is detected by the voltage sensor, it needs to be displayed on the oscilloscope as a voltage signal, in order to more clearly show the change of the voltage value. If the actual fluctuation range of the no-load voltage waveform signal is greater than the standard fluctuation range, it proves that there is still a voltage mutation under no-load condition of the target variable frequency power supply, which is unstable and needs to be handled abnormally for the target variable frequency power supply. The abnormality of the target variable frequency power supply is considered by Xi'an because there is an abnormality in the components inside the power supply itself, and the components need to be replaced to ensure that there is no voltage mutation under no-load condition. The abnormal state transition probability values ​​of different components in the control circuit of the target variable frequency power supply are calculated by the Markov chain algorithm. The core assumption of the Markov chain algorithm is that the future state of the system depends only on the current state, and has nothing to do with the past state. For different components in the control circuit of the target variable frequency power supply, the states of the components include working state, fault state and other intermediate states. The transition probability describes the possibility of transitioning from one state to another. The larger the transition probability, the greater the possibility of transitioning from one state to another, and the greater the probability of failure. The steps to implement the Markov chain algorithm are to first determine the component state, including only normal and faulty states, collect the operating data of different components in different states, and then construct a state transition matrix. Based on the state transition matrix, the transition probability of different components can be obtained. The larger the transition probability of a component, the greater the possibility of it being an abnormal component. Set the threshold of the transition probability of different components. If the transition probability of the component is greater than the corresponding threshold, it proves that there is a problem with the component. After obtaining a class of abnormal components, it needs to be replaced. If the voltage waveform signal is still abnormal after replacement, the variable frequency power supply can be directly filtered by connecting a filter to the variable frequency power supply to ensure that there is no voltage mutation in its no-load state.

[0081] Further, in a preferred embodiment of the present invention, based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, voltage mutation protection is performed on the no-load qualified variable frequency power supply, specifically:

[0082] Introducing a voltage mutation protection mechanism in the target variable frequency power supply control system, wherein the voltage mutation protection mechanism can disconnect the no-load qualified variable frequency power supply from the target power supply network;

[0083] When the no-load qualified variable frequency power supply is marked as an unqualified variable frequency power supply, based on the voltage mutation protection mechanism, the unqualified variable frequency power supply is controlled to be disconnected from the target power supply network in the target variable frequency power supply control system;

[0084] When the unqualified variable frequency power supply is disconnected from the target power supply network, the reasons why the no-load qualified variable frequency power supply is marked as an unqualified variable frequency power supply are analyzed;

[0085] If the reason is a load change reason, a connection circuit between the unqualified variable frequency power supply and the target power supply network is obtained, and a big data network is obtained. Based on the big data network, all schemes of parallel buffer circuits in the connection circuit between the unqualified variable frequency power supply and the target power supply network are retrieved and marked as the first protection scheme, wherein the buffer circuit can smooth the rate at which the normal load level changes to the abnormal load level;

[0086] Select a first protection scheme with the highest rate of smoothing the normal load level to the abnormal load level, mark it as a first output protection scheme, output the first output protection scheme, and obtain a qualified variable frequency power supply;

[0087] If the cause is environmental impact, the environmental impact cause is analyzed. If the environmental impact cause is that the working environment temperature is not maintained within the tolerable working environment temperature threshold, a heat sink is connected to the target variable frequency power supply control device to maintain the working environment temperature of the unqualified variable frequency power supply within the tolerable working environment temperature threshold;

[0088] If the environmental impact is caused by the surrounding electromagnetic interference intensity not being maintained within the tolerable surrounding electromagnetic interference intensity threshold, the filter power of the power filter is intelligently adjusted to maintain the surrounding electromagnetic interference intensity within the tolerable surrounding electromagnetic interference intensity threshold;

[0089] If the reason is due to the individual's own fault, the unqualified variable frequency power supply cannot be connected to the target power supply network to form the target variable frequency power supply control device.

[0090] It should be noted that the reason for introducing the voltage mutation protection mechanism is that if the variable frequency power supply has a voltage mutation when applying a load, it may damage the variable frequency power supply or even the load, causing unpredictable effects. The voltage mutation protection mechanism can detect the real-time voltage value of the variable frequency power supply. If a mutation occurs, the variable frequency power supply and the load, that is, the connection between the target power supply network, will be disconnected immediately to ensure that no damage is caused between the variable frequency power supply and the load. After disconnection, in order to protect the variable frequency power supply, it is necessary to analyze the reasons why the variable frequency power supply is marked as an unqualified variable frequency power supply, in order to find out the cause of the abnormality and correct it, so as to ensure that the probability of voltage mutation in the variable frequency power supply during operation is reduced. If the cause is the load, a buffer circuit can be connected in parallel between the target power supply network and the variable frequency power supply, wherein the buffer circuit can absorb the overvoltage generated by the power electronic device between the target power supply network and the variable frequency power supply, can effectively prevent voltage mutation, and maintain the stability and safety of the connection between the power supply network and the variable frequency power supply. All first protection schemes, that is, schemes for connecting a parallel buffer circuit in the circuit between the unqualified variable frequency power supply and the target power supply network, can be retrieved through the big data network. Among them, the big data network is regarded as a database, which stores various schemes. Since the buffer circuit can smooth the rate at which the normal load level changes to the abnormal load level, the first protection scheme with the largest rate is selected for output, the purpose is to speed up the speed at which the load level changes to normal and improve the protection effect. If the reason is the ambient temperature reason among the environmental reasons, it is judged that a heat sink is needed to maintain the working environment temperature of the unqualified variable frequency power supply within the tolerable working environment temperature threshold, to ensure that the variable frequency power supply does not produce voltage mutations due to the influence of the ambient temperature. If the reason is the excessive surrounding electromagnetic interference intensity among the environmental reasons, it is necessary to adjust the filter power intelligently according to the electromagnetic interference intensity in the power filter to ensure that the surrounding electromagnetic interference intensity is maintained within the tolerable surrounding electromagnetic interference intensity threshold. If the reason is the self-reason, it is judged that the unqualified variable frequency power supply itself has a fault and cannot be temporarily connected to the target power supply network, in order to prevent the faulty variable frequency power supply from causing more serious damage.

[0091] Figure 2 A flow chart of a method for tracing the source of a voltage mutation on a no-load qualified variable frequency power supply that generates a voltage mutation is shown, comprising the following steps:

[0092] S202: in the target variable frequency power supply control system, gradually loading the qualified no-load variable frequency power supply, and obtaining a load voltage waveform signal through an oscilloscope;

[0093] S204: performing wavelet analysis on the load voltage waveform signal based on a wavelet transform algorithm, and classifying the no-load qualified variable frequency power supplies based on the analysis results;

[0094] S206: Based on the abnormal load level and the normal load level, combined with the surrounding environmental factors of the unqualified variable frequency power supply, the voltage mutation of the unqualified variable frequency power supply is traced to the source.

[0095] Further, in a preferred embodiment of the present invention, in the target variable frequency power supply control system, the no-load qualified variable frequency power supply is subjected to a stepwise loading test, and a load voltage waveform signal is obtained through an oscilloscope, specifically:

[0096] In the target variable frequency power supply control system, the load level range supported by the target power supply network is obtained and calibrated as the load level range supported by the target power supply network;

[0097] In the target variable frequency power supply control system, based on the load level range supported by the target power supply network, a step-by-step loading test is performed on the no-load qualified variable frequency power supply, wherein the step-by-step loading test is to gradually increase the load level at the input end of the no-load qualified variable frequency power supply, and calculate the output voltage value of the no-load qualified variable frequency power supply at different load levels;

[0098] During the step-by-step loading test of the no-load qualified variable frequency power supply, based on the oscilloscope, the waveform signal of the output voltage value of the no-load qualified variable frequency power supply at a single load level is calibrated as the load voltage waveform signal.

[0099] It should be noted that after the target variable frequency power supply becomes a no-load qualified variable frequency power supply after the no-load test, it needs to be subjected to a load test to test whether a voltage mutation will occur under the load state. If a voltage mutation occurs, corresponding measures need to be taken to implement voltage mutation protection. The target power supply network can be used as the load of the no-load qualified variable frequency power supply. The advantage is that the target power supply network can achieve changes in load levels by adjusting its own voltage, which is convenient for the no-load qualified variable frequency power supply to perform gradual loading tests. After the gradual loading test, the output voltage value of the no-load qualified variable frequency power supply under different load levels is calculated, and the output voltage value is displayed in the form of a waveform signal through an oscilloscope. The waveform signal can intuitively show the change of the output voltage value, which is very useful for analyzing whether the voltage has a sudden change.

[0100] Further, in a preferred embodiment of the present invention, the wavelet analysis of the load voltage waveform signal is performed based on the wavelet transform algorithm, and the no-load qualified variable frequency power supply is classified based on the analysis result, specifically:

[0101] Introducing a wavelet transform algorithm, wherein the wavelet transform algorithm can perform sampling processing on the load voltage waveform signal and calculate the wavelet coefficients of the sampling points after the sampling processing;

[0102] Based on the wavelet transform algorithm, the load voltage waveform signal is subjected to wavelet transform to obtain wavelet coefficients of the load voltage waveform signal at different sampling points, and standard thresholds of wavelet coefficients of the load voltage waveform signal at different sampling points are preset;

[0103] If the absolute value of the wavelet coefficient of the load voltage waveform signal at a sampling point is greater than the standard threshold of the wavelet coefficient of the load voltage waveform signal at the corresponding sampling point, the corresponding sampling point is calibrated as a mutation sampling point;

[0104] If there is no sudden change sampling point when the no-load qualified variable frequency power supply is running at all load levels, the no-load qualified variable frequency power supply is calibrated as a qualified variable frequency power supply;

[0105] If there is a load level that causes a sudden sampling point to appear when the no-load qualified variable frequency power supply is running, the no-load qualified variable frequency power supply will be calibrated as an unqualified variable frequency power supply, and the corresponding load level will be calibrated as an abnormal load level. At the same time, the load level without a sudden sampling point will be calibrated as a normal load level.

[0106] It should be noted that, since the role of the wavelet transform algorithm in detecting voltage mutations is mainly reflected in its excellent time-frequency local analysis ability and sensitivity to mutation signals, the wavelet transform algorithm can be used to sample the load voltage waveform signal and calculate the wavelet coefficients of the sampling points. The wavelet coefficient reflects the real-time situation of the load voltage. If there is a sampling point whose wavelet coefficient is greater than the standard threshold, the sampling point is determined to be a mutation sampling point, that is, when the no-load qualified variable frequency power supply runs to the time corresponding to this point under load, there is a voltage mutation. If there is no mutation sampling point, the no-load qualified variable frequency power supply is a qualified variable frequency power supply, otherwise it is an unqualified variable frequency power supply. And the corresponding congestion level when there is a mutation sampling point in the unqualified variable frequency power supply is calibrated as an abnormal load level, and the load level without a mutation sampling point is calibrated as a normal load level.

[0107] Further, in a preferred embodiment of the present invention, based on the abnormal load level and the normal load level, combined with the surrounding environmental factors of the unqualified variable frequency power supply, the voltage mutation traceability of the unqualified variable frequency power supply is specifically as follows:

[0108] Determine whether the unqualified variable frequency power supply has changed from a normal load level to an abnormal load level during operation;

[0109] If so, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as the load change reason;

[0110] If not, the surrounding environmental factors of the unqualified variable frequency power supply are obtained and calibrated as a type of environmental factors, wherein the type of environmental factors include the working environment temperature and surrounding electromagnetic interference intensity of the unqualified variable frequency power supply;

[0111] Obtaining instructions for use of the unqualified variable frequency power supply, and based on the instructions for use of the unqualified variable frequency power supply, obtaining a tolerable working environment temperature threshold and a tolerable surrounding electromagnetic interference intensity threshold of the unqualified variable frequency power supply;

[0112] If the working environment temperature and the surrounding electromagnetic interference intensity of the unqualified variable frequency power supply are not maintained within the tolerable working environment temperature threshold and the tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as an environmental impact reason;

[0113] If the working environment temperature and the surrounding electromagnetic interference intensity of the unqualified variable frequency power supply are maintained within the tolerable working environment temperature threshold and the tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is assessed as its own reason.

[0114] It should be noted that there are many reasons for voltage mutation, including load reasons, environmental reasons and self reasons. Among them, to determine the cause of voltage mutation, it is necessary to first determine whether it is a load reason, because the voltage mutation occurs when the no-load qualified variable frequency power supply is loaded, so it is necessary to determine whether it is a load change reason. Determine whether the unqualified variable frequency power supply has changed from a normal load level to an abnormal load level during operation. If so, it is determined to be a load change reason, and the voltage mutation protection of the variable frequency power supply needs to be performed according to the load change situation. Otherwise, determine whether it is an environmental reason. Among them, the environmental reasons include the surrounding ambient temperature reasons and electromagnetic interference intensity reasons of the unqualified variable frequency power supply. The variable frequency power supply has a tolerable working environment temperature threshold and a tolerable surrounding electromagnetic interference intensity threshold. If the surrounding ambient temperature or electromagnetic interference intensity exceeds the corresponding tolerable working environment temperature threshold and tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as an environmental impact reason, because after exceeding the threshold, the variable frequency power supply cannot work in a compliant working environment, which will affect the voltage mutation of the variable frequency power supply. If it is neither due to the environment nor the load change, then the cause of the voltage mutation of the unqualified variable frequency power supply is judged to be its own cause.

[0115] like Figure 3 As shown, the second aspect of the present invention further provides a variable frequency power supply protection system based on voltage mutation detection, the variable frequency power supply protection system includes a memory 31 and a processor 32, the memory 31 stores a variable frequency power supply protection method, and when the variable frequency power supply protection method is executed by the processor 32, the following steps are implemented:

[0116] Connecting the target variable frequency power supply to the target power supply network, and matching the characteristics of the target variable frequency power supply and the target power supply network to obtain a target variable frequency power supply control system;

[0117] The target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, and the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply;

[0118] Perform a step-by-step loading test on the qualified no-load variable frequency power supply, use the wavelet transform algorithm to monitor the voltage mutation of the no-load qualified variable frequency power supply during the step-by-step loading test, and trace the voltage mutation of the no-load qualified variable frequency power supply that generates the voltage mutation;

[0119] Based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, voltage mutation protection is performed on the no-load qualified variable frequency power supply.

[0120] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A variable frequency power supply protection method based on voltage mutation detection, characterized in that: The following steps are involved: Connecting the target variable frequency power supply to the target power supply network, and matching the characteristics of the target variable frequency power supply and the target power supply network to obtain a target variable frequency power supply control system; The target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, and the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply; Perform a step-by-step loading test on the qualified no-load variable frequency power supply, use the wavelet transform algorithm to monitor the voltage mutation of the no-load qualified variable frequency power supply during the step-by-step loading test, and trace the voltage mutation of the no-load qualified variable frequency power supply that generates the voltage mutation; Based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, the no-load qualified variable frequency power supply is protected against voltage mutation; The stepwise loading test of the no-load qualified variable frequency power supply is carried out, and the wavelet transform algorithm is used to monitor the voltage mutation of the no-load qualified variable frequency power supply in the stepwise loading test, and the voltage mutation traceability of the no-load qualified variable frequency power supply that generates the voltage mutation is carried out, specifically: In the target variable frequency power supply control system, the load level range supported by the target power supply network is obtained and calibrated as the load level range supported by the target power supply network; In the target variable frequency power supply control system, based on the load level range supported by the target power supply network, a step-by-step loading test is performed on the no-load qualified variable frequency power supply, wherein the step-by-step loading test is to gradually increase the load level at the input end of the no-load qualified variable frequency power supply, and calculate the output voltage value of the no-load qualified variable frequency power supply at different load levels; During the step-by-step loading test of the no-load qualified variable frequency power supply, the waveform signal of the output voltage value of the no-load qualified variable frequency power supply at a single load level is calibrated as the load voltage waveform signal based on an oscilloscope; Introducing a wavelet transform algorithm, wherein the wavelet transform algorithm can perform sampling processing on the load voltage waveform signal and calculate the wavelet coefficients of the sampling points after the sampling processing; Based on the wavelet transform algorithm, the load voltage waveform signal is subjected to wavelet transform to obtain wavelet coefficients of the load voltage waveform signal at different sampling points, and standard thresholds of wavelet coefficients of the load voltage waveform signal at different sampling points are preset; If the absolute value of the wavelet coefficient of the load voltage waveform signal at a sampling point is greater than the standard threshold of the wavelet coefficient of the load voltage waveform signal at the corresponding sampling point, the corresponding sampling point is calibrated as a mutation sampling point; If there is no sudden change sampling point when the no-load qualified variable frequency power supply is running at all load levels, the no-load qualified variable frequency power supply is calibrated as a qualified variable frequency power supply; If there is a load level that causes a sudden change sampling point when the no-load qualified variable frequency power supply is running, the no-load qualified variable frequency power supply will be calibrated as an unqualified variable frequency power supply, and the corresponding load level will be calibrated as an abnormal load level, and the load level without a sudden change sampling point will be calibrated as a normal load level; Based on the abnormal load level and the normal load level, and in combination with the surrounding environmental factors of the unqualified variable frequency power supply, tracing the voltage mutation of the unqualified variable frequency power supply; The voltage mutation tracing of the unqualified variable frequency power supply is performed based on the abnormal load level and the normal load level and in combination with the surrounding environmental factors of the unqualified variable frequency power supply, specifically: Determine whether the unqualified variable frequency power supply has changed from a normal load level to an abnormal load level during operation; If so, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as the load change reason; If not, the surrounding environmental factors of the unqualified variable frequency power supply are obtained and calibrated as a type of environmental factors, wherein the type of environmental factors include the working environment temperature and surrounding electromagnetic interference intensity of the unqualified variable frequency power supply; Obtaining instructions for use of the unqualified variable frequency power supply, and based on the instructions for use of the unqualified variable frequency power supply, obtaining a tolerable working environment temperature threshold and a tolerable surrounding electromagnetic interference intensity threshold of the unqualified variable frequency power supply; If the working environment temperature and the surrounding electromagnetic interference intensity of the unqualified variable frequency power supply are not maintained within the tolerable working environment temperature threshold and the tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is evaluated as an environmental impact reason; If the working environment temperature and the surrounding electromagnetic interference intensity of the unqualified variable frequency power supply are maintained within the tolerable working environment temperature threshold and the tolerable surrounding electromagnetic interference intensity threshold, the reason for marking the no-load qualified variable frequency power supply as an unqualified variable frequency power supply is assessed as its own reason.

2. According to the variable frequency power supply protection method based on voltage mutation detection as described in claim 1, it is characterized in that: The target variable frequency power supply is connected to the target power supply network, and the target variable frequency power supply and the target power supply network are matched with each other to obtain the target variable frequency power supply control system, specifically: The variable frequency power supply that needs to be tested for voltage mutation is calibrated as the target variable frequency power supply, and the rated input voltage, rated output voltage, rated capacity, rated operating frequency and operating frequency range of the variable frequency power supply are obtained; Obtain a power supply network whose voltage level covers the rated input voltage and rated output voltage of the variable frequency power supply, mark it as a target power supply network, and obtain a supported power supply network frequency range on the target power supply network; Analyze whether the rated operating frequency of the target variable frequency power supply is within the power supply network frequency range supported by the target power supply network. If so, directly connect the target variable frequency power supply to the target power supply network to obtain the target variable frequency power supply control system; If not, connecting the target variable frequency power supply to the target power supply network and obtaining a synchronous converter, wherein the synchronous converter is capable of adjusting the frequency of the target variable frequency power supply; Within the operating frequency range of the target variable frequency power supply, the frequency of the target variable frequency power supply is adjusted based on the synchronous converter so that the operating frequency of the target variable frequency power supply is maintained within the power supply network frequency range supported by the target power supply network, thereby obtaining a target variable frequency power supply control system.

3. According to the variable frequency power supply protection method based on voltage mutation detection as described in claim 1, it is characterized in that: The target variable frequency power supply is operated at no-load in the target variable frequency power supply control system, the voltage change of the target variable frequency power supply is monitored based on an oscilloscope during the no-load operation, and the target variable frequency power supply is optimized based on the voltage change to obtain a no-load qualified variable frequency power supply, specifically: A voltage sensor and an oscilloscope are connected to the target variable frequency power supply, wherein the voltage sensor can monitor the voltage value of the target variable frequency power supply in real time during the operation of the target variable frequency power supply, and the oscilloscope can output the voltage value of the target variable frequency power supply obtained by real-time monitoring in the form of a waveform signal; Controlling the target variable frequency voltage to operate at no load in the target variable frequency power supply control system, and monitoring the output voltage value of the target variable frequency power supply at no load based on the voltage sensor, and converting the output voltage value of the target variable frequency power supply at no load based on the oscilloscope into a waveform signal, which is calibrated as a no-load voltage waveform signal; Based on the rated input voltage and rated output voltage of the target variable frequency power supply, a standard fluctuation range of the no-load voltage waveform signal of the target variable frequency power supply is preset, and a waveform signal analysis is performed on the no-load voltage waveform signal to obtain an actual fluctuation range of the no-load voltage waveform signal; If the actual fluctuation range of the no-load voltage waveform signal is maintained within the fluctuation standard range of the no-load voltage waveform signal, the target variable frequency power supply is calibrated as a no-load qualified variable frequency power supply; If the actual fluctuation range of the no-load voltage waveform signal does not remain within the fluctuation standard range of the no-load voltage waveform signal, the working parameters of different components in the control circuit of the target variable frequency power supply when running at no load are obtained, and the Markov chain algorithm is introduced to analyze the working parameters of different components in the control circuit of the target variable frequency power supply when running at no load, and the abnormal state transition probability values ​​of different components in the control circuit of the target variable frequency power supply are calculated; The components whose abnormal state transfer probability value is greater than the preset value are calibrated as a type of abnormal components, and the type of abnormal components are replaced. If the actual fluctuation range of the no-load voltage waveform signal is still not maintained within the standard fluctuation range of the no-load voltage waveform signal after the type of abnormal components are replaced, a power supply filter is introduced and operated at the input end of the variable frequency power supply to maintain the actual fluctuation range of the no-load voltage waveform signal within the standard fluctuation range of the no-load voltage waveform signal, so as to obtain a no-load qualified variable frequency power supply.

4. According to the variable frequency power supply protection method based on voltage mutation detection as described in claim 1, it is characterized in that: The voltage mutation protection for the no-load qualified variable frequency power supply is performed based on the different reasons why the no-load qualified variable frequency power supply is calibrated as an unqualified variable frequency power supply, specifically: Introducing a voltage mutation protection mechanism in the target variable frequency power supply control system, wherein the voltage mutation protection mechanism can disconnect the no-load qualified variable frequency power supply from the target power supply network; When the no-load qualified variable frequency power supply is marked as an unqualified variable frequency power supply, based on the voltage mutation protection mechanism, the unqualified variable frequency power supply is controlled to be disconnected from the target power supply network in the target variable frequency power supply control system; When the unqualified variable frequency power supply is disconnected from the target power supply network, the reasons why the no-load qualified variable frequency power supply is marked as an unqualified variable frequency power supply are analyzed; If the reason is a load change reason, a connection circuit between the unqualified variable frequency power supply and the target power supply network is obtained, and a big data network is obtained. Based on the big data network, all schemes of parallel buffer circuits in the connection circuit between the unqualified variable frequency power supply and the target power supply network are retrieved and marked as the first protection scheme, wherein the buffer circuit can smooth the rate at which the normal load level changes to the abnormal load level; Select a first protection scheme with the highest rate of smoothing the normal load level to the abnormal load level, mark it as a first output protection scheme, output the first output protection scheme, and obtain a qualified variable frequency power supply; If the cause is environmental impact, the environmental impact cause is analyzed. If the environmental impact cause is that the working environment temperature is not maintained within the tolerable working environment temperature threshold, a heat sink is connected to the target variable frequency power supply control device to maintain the working environment temperature of the unqualified variable frequency power supply within the tolerable working environment temperature threshold; If the environmental impact is caused by the surrounding electromagnetic interference intensity not being maintained within the tolerable surrounding electromagnetic interference intensity threshold, the filter power of the power filter is intelligently adjusted to maintain the surrounding electromagnetic interference intensity within the tolerable surrounding electromagnetic interference intensity threshold; If the reason is due to the individual's own fault, the unqualified variable frequency power supply cannot be connected to the target power supply network to form the target variable frequency power supply control device.

5. The variable frequency power supply protection system based on voltage mutation detection is characterized in that: The variable frequency power supply protection system includes a memory and a processor. The memory stores a variable frequency power supply protection method program. When the variable frequency power supply protection method program is executed by the processor, the variable frequency power supply protection method steps as described in any one of claims 1 to 4 are implemented.

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