A zero-crossing detection method, a commutation switching method, a system and a commutation switching device

Abstract

A zero-crossing detection method, phase-change switching method, system and phase-change switching device provided by the present invention. The zero-crossing detection method includes: obtaining a signal to be detected; performing zero-crossing detection on the signal to be detected by using a plurality of zero-crossing detection methods to obtain zero-crossing detection times corresponding to the respective zero-crossing detection methods; screening out a set of candidate zero-crossing times with all detection results being consistent from the zero-crossing detection times corresponding to the respective zero-crossing detection methods; and determining a target zero-crossing time from the set of candidate zero-crossing times based on the time sequence. By implementing the present invention, the accuracy of zero-crossing recognition is improved.

Description

Technical Field

[0001] The present invention relates to the field of power commutation switching, and particularly to a zero - point detection method, a commutation switching method, a system and a commutation switching device. Background Art

[0002] The power supply mode selected for domestic distribution networks is mainly three - phase four - wire system. Whether a certain phase load increases or decreases rapidly, it will increase the three - phase imbalance of the distribution network. Once the degree of three - phase imbalance increases, it will endanger the relevant equipment of the distribution network. Severe imbalance will increase the loss of the transformer, cause the excitation current of the transformer to increase, and may even damage the transformer in severe cases. At the same time, it will also endanger the equipment of users, resulting in great economic losses.

[0003] Currently, in terms of improving three - phase imbalance, the commonly used means include: load compensation devices, distribution network reconstruction, and three - phase balance optimized commutation. Among them, the three - phase balance optimized commutation strategy is widely applied. It generally regularly calculates the three - phase imbalance degree on the low - voltage side of the distribution transformer, and when it exceeds the limit, it reduces the three - phase imbalance degree by manually changing the connection phase of the load at the low - voltage load end. This kind of manual commutation will cause temporary power outage of users during the adjustment process, and after the commutation is completed, it can only solve the imbalance problem in a certain period and cannot solve the problem permanently. Therefore, people hope to use intelligent commutation devices to improve the three - phase imbalance of the distribution network, which can realize automatic sampling, operation, and communication of the power grid, and through a preset intelligent commutation strategy, obtain the optimal commutation scheme for the distribution network, and finally realize the three - phase balance of the power grid through automatic phase - sequence switching of the switch. Since the commutation execution terminal of the intelligent commutation device uses the zero - crossing moment of voltage and current as a reference during switching, and the zero - crossing moment detection method in the prior art is easily affected by various harmonic - containing and frequency - fluctuating waveforms in the power grid, resulting in low zero - crossing detection accuracy, which in turn affects the improvement effect of three - phase imbalance. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low zero - crossing moment judgment accuracy in the prior art, and thus provide a zero - point detection method, a commutation switching method, a system and a commutation switching device.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] In the first aspect, an embodiment of the present invention provides a zero - point detection method, including: obtaining a signal to be detected; performing zero - point detection on the signal to be detected by using multiple zero - point detection methods to obtain zero - point detection moments corresponding to each zero - point detection method; screening out a set of candidate zero - point moments with consistent detection results from the zero - point detection moments corresponding to each zero - point detection method; and determining a target zero - point moment from the set of candidate zero - point moments based on the time sequence.

[0007] Optionally, the zero-crossing detection of the signal to be detected using multiple zero-crossing detection methods includes: performing zero-crossing detection on the signal to be detected using a first zero-crossing detection method; the performing zero-crossing detection on the signal to be detected using the first zero-crossing detection method includes: performing a fast Fourier transform calculation on the signal to be detected to obtain the phase spectrum corresponding to the signal to be detected in the time-frequency domain; obtaining the first zero-crossing detection moment corresponding to the first zero-crossing detection method according to the phase components of the voltage and current fundamental waves corresponding to the power frequency in the phase spectrum.

[0008] Optionally, the obtaining the first zero-crossing detection moment corresponding to the first zero-crossing detection method according to the phase components of the voltage and current fundamental waves corresponding to the power frequency in the phase spectrum includes: calculating the zero-crossing moment through the following formula:

[0009] where T u is the zero-crossing moment of entry, k is the number of cycles, is the phase component of the voltage fundamental wave;

[0010] where T i is the zero-crossing moment of exit, k is the number of cycles, is the phase component of the current fundamental wave.

[0011] Optionally, the zero-crossing detection of the signal to be detected using multiple zero-crossing detection methods includes: performing zero-crossing detection on the signal to be detected using a second zero-crossing detection method; the performing zero-crossing detection on the signal to be detected using the second zero-crossing detection method includes: performing zero-crossing detection on the signal to be detected by means of comparator interruption to obtain the second zero-crossing detection moment corresponding to the second zero-crossing detection method.

[0012] In a second aspect, an embodiment of the present invention provides a commutation switching method, including: acquiring a signal to be detected, and obtaining a target zero-crossing moment by using the zero-crossing detection method described in the first aspect of the present invention; calculating a target relay action delay time; determining a target signal sending moment based on the target zero-crossing moment and the target relay action delay time, and performing commutation switching at the target zero-crossing moment based on the target signal sending moment.

[0013] Optionally, the calculating the target relay action delay time includes: collecting historical relay action delay times, and acquiring a preset relay action delay time; adding and averaging the historical relay action delay time and the preset relay action delay time to determine the target relay action delay time.

[0014] In a third aspect, an embodiment of the present invention provides a zero - point detection system, including: a first acquisition module, configured to acquire a signal to be detected; a first calculation module, configured to perform zero - point detection on the signal to be detected by using multiple zero - point detection methods to obtain zero - point detection times corresponding to the respective zero - point detection methods; a first screening module, configured to screen out a set of candidate zero - point times with consistent detection results from the zero - point detection times corresponding to the respective zero - point detection methods; and a first processing module, configured to determine a target zero - point time from the set of candidate zero - point times based on the time sequence.

[0015] In a fourth aspect, an embodiment of the present invention provides a commutation switching system, including: a second processing module, configured to acquire a signal to be detected and obtain a target zero - point time by using the zero - point detection method described in the first aspect of the present invention; a second calculation module, configured to calculate a target relay action delay time; and a first switching module, configured to determine a target signal sending time based on the target zero - point time and the target relay action delay time, and perform commutation switching at the target zero - point time based on the target signal sending time.

[0016] In a fifth aspect, an embodiment of the present invention provides a commutation switching device, including: a sampling device, a software zero - point detection device, a hardware zero - point detection device, a controller, and a commutation switching actuator. Among them, the sampling device is configured to collect a signal to be detected of a device to be switched and send the signal to be detected to the software zero - point detection device and the hardware zero - point detection device; the hardware zero - point detection device is configured to perform zero - point detection on the signal to be detected to obtain a first zero - point time and send the first zero - point time to the controller; the software zero - point detection device is configured to perform zero - point detection on the signal to be detected to obtain a second zero - point time and send the second zero - point time to the controller; the controller is configured to compare the first zero - point time and the second zero - point time, generate a commutation switching control signal, and send the commutation switching control signal to the commutation switching actuator; and the commutation switching actuator is configured to perform a commutation switching action on the device to be switched according to the commutation switching control signal.

[0017] In a sixth aspect, an embodiment of the present invention provides a computer - readable storage medium storing computer instructions for causing a computer to execute the zero - point detection method described in the first aspect of the present invention or the commutation switching method described in the second aspect of the present invention.

[0018] In a seventh aspect, an embodiment of the present invention provides a computer device, including: a memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor executes the computer instructions to execute the zero-crossing detection method described in the first aspect of the present invention or the commutation switching method described in the second aspect of the present invention.

[0019] The technical solution of the present invention has the following advantages:

[0020] The zero-crossing detection method provided by the present invention includes: obtaining a signal to be detected; performing zero-crossing detection on the signal to be detected by using multiple zero-crossing detection methods to obtain zero-crossing detection times corresponding to the respective zero-crossing detection methods; screening out a set of candidate zero-crossing times with consistent detection results from the zero-crossing detection times corresponding to the respective zero-crossing detection methods; and determining a target zero-crossing time from the set of candidate zero-crossing times based on the time sequence. By performing zero-crossing detection on the signal to be detected by combining multiple zero-crossing detection methods, even when the detection effect of one method is poor, another method can still be used as a supplement, so that for various waveforms with harmonics and frequency fluctuations in the power grid, the finally detected zero-crossing still has a relatively accurate result. The multi-dimensional accurate zero-crossing detection effectively solves the distortion problem of the power quantity signal caused by the randomness of diverse system loads and the dynamic interference characteristics, and solves the problem that the existing zero-crossing detection scheme cannot meet the requirement of accurate zero-crossing identification in the complex scenarios of diverse load dynamic operations.

[0021] The commutation switching method provided by the present invention includes: obtaining a signal to be detected, and using the above zero-crossing detection method to obtain a target zero-crossing time; calculating the target relay action delay time; determining a target signal sending time based on the target zero-crossing time and the target relay action delay time, and performing commutation switching at the target zero-crossing time based on the target signal sending time. By continuously correcting the delay time of the target relay, the relay can complete the zero-crossing action more accurately, and the risk of generating arcs and inrush currents during the commutation process is minimized, protecting the contacts of the relay, extending the service life of the relay, preventing the failure of breaking due to arcing, and reducing the impact on the power grid.

[0022] The commutation switching device provided by the present invention includes: a sampling device, a software zero-crossing detection device, a hardware zero-crossing detection device, a controller, and a commutation switching actuator. Among them, the sampling device is used to collect the signal to be detected of the device to be switched, and send the signal to be detected to the software zero-crossing detection device and the hardware zero-crossing detection device; the hardware zero-crossing detection device is used to perform zero-crossing detection on the signal to be detected to obtain the first zero-crossing moment, and send the first zero-crossing moment to the controller; the software zero-crossing detection device is used to perform zero-crossing detection on the signal to be detected to obtain the second zero-crossing moment, and send the second zero-crossing moment to the controller; the controller is used to compare the first zero-crossing moment and the second zero-crossing moment, generate a commutation switching control signal, and send the commutation switching control signal to the commutation switching actuator; the commutation switching actuator is used to perform commutation switching actions on the device to be switched according to the commutation switching control signal. By adopting a combination of multiple zero-crossing detection methods to perform zero-crossing detection on the signal to be detected, even if the detection effect of one method is poor, the other method can still be used as a supplement, so that for various harmonic-containing and frequency-fluctuating waveforms in the power grid, the finally detected zero-crossing still has a relatively accurate result. Through multi-dimensional precise zero-crossing detection, the distortion problem of the power signal caused by the randomness of diverse system loads and the dynamic interference characteristics is effectively solved, and the problem that the existing zero-crossing detection scheme cannot meet the requirement of precise zero-crossing identification in the complex scenario of diverse load dynamic operation is solved, and the accuracy of zero-crossing switching of the commutation switching device is improved. Description of the Drawings

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a flowchart of a specific example of the zero-crossing detection method in the embodiment of the present invention;

[0025] Figure 2 It is a flowchart of a specific example of the commutation switching method in the embodiment of the present invention;

[0026] Figure 3a It is the input signal in the normal power grid working state for the commutation execution terminal to perform zero-crossing switching in the embodiment of the present invention;

[0027] Figure 3b It is the output signal for performing zero-crossing detection by applying the zero-crossing detection algorithm of the application software;

[0028] Figure 3c It is the output signal for performing zero-crossing detection by applying the hardware comparator interruption;

[0029] Figure 3d It is the real-time judgment output signal of the system state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0030] Figure 4a It is the input signal in the flat-shoulder multi-zero-crossing waveform working state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0031] Figure 4b It is the output signal of zero-crossing detection by using the zero-crossing detection algorithm of the application software;

[0032] Figure 4c It is the output signal of zero-crossing detection by using the interrupt of the application hardware comparator;

[0033] Figure 4d It is the real-time judgment output signal of the system state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0034] Figure 5a It is the input signal in the steep and extremely fast zero-crossing waveform working state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0035] Figure 5b It is the output signal of zero-crossing detection by using the zero-crossing detection algorithm of the application software;

[0036] Figure 5c It is the output signal of zero-crossing detection by using the interrupt of the application hardware comparator;

[0037] Figure 5d It is the real-time judgment output signal of the system state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0038] Figure 6a It is the input signal in the non-power frequency working state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0039] Figure 6b It is the output signal of zero-crossing detection by using the zero-crossing detection algorithm of the application software;

[0040] Figure 6c It is the output signal of zero-crossing detection by using the interrupt of the application hardware comparator;

[0041] Figure 6d It is the real-time judgment output signal of the system state for zero-crossing switching of the commutation execution terminal in the embodiment of the present invention;

[0042] Figure 7 It is the principle block diagram of a specific example of the zero-crossing detection system in the embodiment of the present invention;

[0043] Figure 8It is a principle block diagram of a specific example of the commutation switching system in the embodiment of the present invention;

[0044] Figure 9 It is a principle block diagram of a specific example of the commutation switching device in the embodiment of the present invention;

[0045] Figure 10 It is a composition diagram of a specific example of the computer device provided by the embodiment of the present invention. Detailed implementation manners

[0046] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0047] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0048] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0049] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] The embodiment of the present invention provides a zero-crossing detection method, which is applied to a zero-crossing switching device, such as Figure 1 shown, and includes the following steps:

[0051] Step S10: Obtain the signal to be detected.

[0052] In a specific embodiment, during the operation of the zero-crossing switching device, the commutation terminal voltage and current signals are sampled point by point at a frequency f, and the voltage and current signals are analyzed with a set time window length Ts. Subsequently, a multi-time-frequency analysis process is performed on the voltage and current signals Xn within the time window, and the starting sampling time is recorded as 0. Considering that on the one hand, too few data points within the time window cannot accurately reflect the fundamental difference characteristics between fault arcs and arc-like phenomena, and on the other hand, too many data points within the time window cannot quickly perform fast Fourier transform analysis. Therefore, in the embodiment of the present invention, the number of data points N within the time window is selected as 256. To meet the hardware requirements of the Cortex-M3 processor in the zero-crossing switching device and be able to reflect the characteristic frequency band of the difference between the zero-crossing point and the non-zero-crossing point, the sampling frequency f of the commutation execution terminal output voltage and current signals is taken as 12.8 kHz. Among them, the sampling frequency can be adjusted according to the processor parameters and is not limited herein. In the embodiment of the present invention, the zero-crossing switching device includes: a commutation execution terminal, a reactive power compensation device, and a high-voltage vacuum switch. Only as an example, it is not limited thereto.

[0053] Step S11: Use multiple zero-crossing detection methods to perform zero-crossing detection on the signal to be detected, and obtain the zero-crossing detection moments corresponding to each zero-crossing detection method.

[0054] In a specific embodiment, in actual engineering applications, multiple zero-crossing detection methods can be used to perform zero-crossing detection on the signal to be detected. The zero-crossing detection methods include: Step S111: Use the first zero-crossing detection method to perform zero-crossing detection on the signal to be detected. Specifically, the zero-crossing detection process includes the following steps:

[0055] Step S1111: Perform fast Fourier transform calculation on the signal to be detected to obtain the phase spectrum corresponding to the signal to be detected in the time-frequency domain.

[0056] Step S1112: Obtain the first zero-crossing detection moment corresponding to the first zero-crossing detection method according to the phase components of the voltage and current fundamental waves corresponding to the power frequency in the phase spectrum.

[0057] In the embodiment of the present invention, the voltage and current detection signal Xn is analyzed by using the fast Fourier transform method to obtain the amplitude spectrum An and the phase spectrum Bn corresponding to the commutation execution terminal voltage and current detection signal Xn in the time-frequency domain under this time window.

[0058] For the amplitude spectrum and phase spectrum obtained by the fast Fourier transform, each element in the amplitude spectrum and phase spectrum corresponds to the information of a certain frequency of the acquired signal. The present invention uses the original signal data with 256 points and a sampling frequency of 12.8 kHz. Therefore, the frequency corresponding to the i-th element in the amplitude spectrum and phase spectrum after the fast Fourier transform is 12800*(i - 1) / 256 Hz. The signals obtained in the application scenario of the zero-crossing switching device are the voltage and current in the power grid. Its main component is the fundamental frequency component of 50 Hz for transmitting electric energy, and it contains certain high-order, discrete harmonics with frequencies that are multiples of 50 Hz. For the first element in the amplitude spectrum and phase spectrum with a frequency of 0 Hz, that is, the DC component, it only appears in the neutral line during faults such as three-phase imbalance in the low-voltage AC power grid, or in the case of ground faults, etc. Generally, its content is extremely small and the existence time is very short, so it can be ignored; for the elements with frequencies ≥100 Hz in the amplitude spectrum and phase spectrum starting from the third element, that is, the high-order harmonic components, although there are certain requirements for the harmonic content during power transmission in the power grid and their content is also small, their composition is complex and it is difficult to analyze. Ignoring them can save a large amount of computing resources without affecting the judgment of the zero-crossing result, so they are also not considered. Based on this, when obtaining its characteristics, the second element, the 50 Hz fundamental frequency component, is mainly used to grasp the relevant information of the voltage and current detection signal Xn and realize the prediction and judgment of the zero-crossing time. For the second group of elements, the amplitude spectrum part is the amplitude of the component at the 50 Hz frequency, and the argument between [0, 2π] in the phase spectrum part is the phase of the fundamental frequency component of 50 Hz. Obtaining the amplitudes of the fundamental waves of voltage and current at the 50 Hz frequency, that is, obtaining the amplitudes of the main components of the voltage and current detection signal Xn, can be used to calculate the power of the load after the commutation execution terminal and report it to the commutation control terminal for formulating the three-phase imbalance automatic adjustment commutation strategy. Obtaining the phases of the fundamental waves of voltage and current at the 50 Hz frequency, that is, obtaining the initial phases of the main components of the voltage and current detection signal Xn, can also be used to obtain the power of the load after the commutation execution terminal and can also be used to judge the zero-crossing moment. Therefore, these two characteristic quantities are used to obtain the relevant information of the voltage and current detection signal Xn for zero-crossing prediction and judgment.

[0059] In the embodiment of the present invention, according to the phase components of the fundamental waves of voltage and current corresponding to the power frequency in the phase spectrum, the first zero-crossing detection moment corresponding to the first zero-crossing detection method is obtained, including: using the phase component of the fundamental wave of voltage corresponding to the power frequency in the phase spectrum The phase component of the fundamental wave of current The signal amplitude A of the fundamental wave of voltage u and the signal amplitude A of the fundamental wave of current i , the time-domain expressions of the fundamental waves of voltage and current corresponding to the power frequency in the phase spectrum can be obtained According to the expression, the zero-crossing moments of the fundamental voltage and current corresponding to the power frequency in the subsequent phase spectrum can be obtained. Specifically, the zero-crossing moments are calculated by the following formula:

[0060]

[0061] where T u is the zero-crossing moment of the cut-in, k is the number of cycles, is the phase component of the fundamental voltage;

[0062]

[0063] where T i is the zero-crossing moment of the cut-out, k is the number of cycles, is the phase component of the fundamental current.

[0064] In the embodiment of the present invention, when detecting the zero-crossing moment by the first zero-crossing detection method, the fast Fourier transform method is adopted. Not only is the calculation speed fast and the information acquisition efficiency high, but also the information required for analyzing the voltage and current signals can be quickly obtained with less computing resources, which speeds up the time for zero-crossing prediction and judgment. This method can obtain the information at each frequency of the signal, which is convenient for subsequent steps to obtain the required characteristic quantities and no other processing process is required, simplifying the calculation process of the algorithm.

[0065] The present invention can reliably identify the zero-crossing points of various harmonics. In the actual power grid, various harmonics will be generated due to different load characteristics, resulting in different detection signals. The use of the fast Fourier transform in the present invention can effectively identify the zero-crossing points of the voltage and current under the influence of various harmonics, accurately provide a scientific and reasonable action moment for the commutation terminal, solve the problem of non-zero switching caused by the difficulty in finding the zero-crossing point, achieve accurate capture of the zero-crossing point in the case of multi-electricity distortion, and improve the power supply stability of the substation area. And it can ensure the rapidity of zero-crossing detection. The selected fast Fourier transform method only needs to collect the data of one cycle for subsequent judgment, solves the problem of long time consumption of the traditional zero-crossing detection algorithm, speeds up the zero-crossing detection and judgment time, and reduces the performance requirements of the zero-crossing detection algorithm for the equipment

[0066] Furthermore, the zero-crossing detection method further includes: Step S112: Use the second zero-crossing detection method to detect the zero-crossing of the signal to be detected. Specifically, the zero-crossing detection process includes the following steps:

[0067] Step S1121: Use the method of comparator interruption to detect the zero-crossing of the signal to be detected, and obtain the second zero-crossing detection moment corresponding to the second zero-crossing detection method.

[0068] In an embodiment of the present invention, the comparator compares the signal to be detected with the grounded signal, i.e., the zero signal. When the signal to be detected is greater than zero, the comparator outputs 1; when the signal to be detected is less than zero, the comparator outputs 0. Therefore, when the output signal changes from 1 to 0 or from 0 to 1, the signal to be detected undergoes a positive-negative switching, that is, a zero crossing occurs. For the output of the comparator connected to the interrupt detection, it is set to trigger on the rising / falling edge. When the interrupt is triggered, it is regarded as a zero crossing occurring.

[0069] Step S12: Screen out a set of candidate zero-crossing moments with consistent detection results from the zero-crossing detection moments corresponding to each zero-crossing detection method.

[0070] In a specific embodiment, the fundamental frequency time-domain expression obtained by using the first zero-crossing detection method is a trigonometric function with a frequency of 50 Hz, which is a periodic function. It passes through a zero crossing every half cycle. All subsequent zero-crossing phases can be obtained through the initial phase in the expression, and the zero-crossing moments corresponding to these phases can be obtained in combination with the power frequency. The interrupt trigger moment obtained by the second zero-crossing detection method is the zero-crossing moment. The intersection of the zero-crossing moments obtained by the above two zero-crossing detection methods is taken to screen out a set of candidate zero-crossing moments with consistent detection results. Specifically, the first zero-crossing detection method and the second zero-crossing detection method are used to perform real-time output commutation to execute the 0 / 1 determination result of whether the terminal voltage and current signals have a zero crossing. When a zero crossing occurs, 1 is output; when it is determined that there is no zero crossing, 0 is output. Only when both methods output 1 simultaneously is it considered that the signal has achieved a zero crossing; otherwise, it is considered that the signal has not reached the actual zero crossing. The joint confirmation of the two methods ensures that the zero-crossing switching strategy can find the actual zero crossing of the signal, improving the accuracy of zero-crossing judgment.

[0071] Step S13: Determine the target zero-crossing moment from the set of candidate zero-crossing moments based on the time sequence.

[0072] In a specific embodiment, the zero-crossing moments obtained by the first zero-crossing detection method and the second zero-crossing detection method are judged together. When both of them consider that the zero-crossing moment has been reached, it is regarded as detecting the zero crossing of the (voltage) current detection signal X n and record the moment at this time as t 0 After the commutation execution terminal includes the delay Δt of the entire zero-crossing switching process, the next zero crossing that is closest to the determined zero crossing and has the smallest error is selected, that is, the zero crossing 0.01 s after half a cycle is the target zero-crossing moment.

[0073] The zero - point detection method provided by the present invention includes: obtaining a signal to be detected; performing zero - point detection on the signal to be detected by using multiple zero - point detection methods to obtain the zero - point detection moments corresponding to each zero - point detection method; screening out a set of candidate zero - point moments with consistent detection results from the zero - point detection moments corresponding to each zero - point detection method; and determining a target zero - point moment from the set of candidate zero - point moments based on the time sequence. By using a combination of multiple zero - point detection methods to perform zero - point detection on the signal to be detected, even when the detection effect of one method is poor, another method can still be used as a supplement, so that for various waveforms with harmonics and frequency fluctuations in the power grid, the finally detected zero - crossing points still have relatively accurate results. Through multi - dimensional precise zero - crossing detection, the distortion problem of the power signal caused by the randomness of diverse system loads and dynamic interference characteristics is effectively solved, and the problem that the existing zero - crossing detection scheme cannot meet the requirements of precise zero - crossing identification in the complex scenarios of diverse load dynamic operations is solved.

[0074] The embodiment of the present invention also provides a commutation switching method, as Figure 2 shown, which includes the following steps:

[0075] Step S20: Obtain a signal to be detected, and use the above - mentioned zero - point detection method to obtain a target zero - point moment.

[0076] Step S21: Calculate the target relay action delay time.

[0077] Step S22: Based on the target zero - point moment and the target relay action delay time, determine a target signal sending moment, and perform commutation switching at the target zero - point moment based on the target signal sending moment.

[0078] In a specific embodiment, first, the voltage and current signals are sampled in real - time, and the above - mentioned zero - point detection method is used to perform zero - crossing judgment on the voltage and current signals. When both of the above two methods consider that the zero - crossing moment has been reached, it is regarded as detecting the zero - crossing point of the (voltage) current detection signal Xn. Record the moment at this time as t0, and after the commutation execution terminal includes the delay Δt of the entire zero - crossing switching process, select the next zero - crossing point that is closest to the determined zero - crossing point and has the smallest error, that is, the zero - crossing point after half a cycle of 0.01s. Send a commutation signal at t0 + 0.01s - Δt, so that the commutation execution terminal completes the cut - out at t0+0.01s, and sets the cut - out completion signal to 1, and counts the relay action delay time Δt0 of the cut - out phase. Perform weighted averaging on the statistically obtained relay action delay time Δt 0 of the cut - out phase and the relay action delay time Δt stored in the system to obtain a new relay action delay time Δt', and replace the original relay action delay time stored in the system.

[0079] Specifically, calculating the target relay action delay time includes the following steps:

[0080] Step S211: Collect the historical relay operation delay time and obtain the preset relay operation delay time.

[0081] Step S212: Add and average the historical relay operation delay time and the preset relay operation delay time to determine the target relay operation delay time.

[0082] In practical engineering applications, the operation time of the relay has a certain dispersion, and its operation time will change with the working scenario, service time, etc., which affects the delay estimation in the zero-crossing switching strategy. In the present invention, the operation time of the relay for each operation is statistically analyzed after each relay operation, and it is weighted and averaged with the previously statistically averaged relay operation time as the correction for considering the delay during subsequent relay operations. Under such a delay correction algorithm, the weight of the most recent relay operation time is the largest, and the weight of the older relay operation time is smaller. This not only takes into account the situation that the relay operation times are more similar within a short period of time but also avoids misjudgment of the delay estimation caused by sudden changes in the relay operation time, enabling the zero-crossing switching strategy of the phase-change execution terminal to ensure that the relay operates at the zero-crossing moment of the phase signal where it is located to complete the switching.

[0083] By continuously statistically analyzing, updating, and correcting the delay time of the execution terminal operation, the present invention fully considers the delays generated in each link during terminal operation and the influence of the dispersion of the relay electrical life, enabling the relay to operate more accurately at the zero-crossing point, minimizing the risks of arc and inrush current generation during the phase-change process, protecting the contacts of the relay, extending the service time of the relay, preventing interruption failure due to arcing, and reducing the impact on the power grid.

[0084] In actual engineering applications, neither software nor hardware zero-crossing detection can obtain the absolute zero-crossing moment, and both contain certain errors. Among them, software zero-crossing detection based on the fast Fourier transform has a certain error in the moment of the zero-crossing point, while hardware zero-crossing detection based on a comparator has a certain error in the signal value at the zero-crossing point moment. In some working conditions with a large amount of harmonics, such as a steep and extremely fast zero-crossing waveform, the zero-crossing point moment obtained based on the fast Fourier transform may, due to the error in the moment, judge a point where the actual signal value is still large, losing the normal zero-crossing point judgment ability. In these working conditions, hardware zero-crossing detection based on a comparator will not judge a zero-crossing point with a large error and presents a value close to the actual zero-crossing moment. On the contrary, in some other working conditions, such as a flat-shoulder multi-zero-crossing waveform, the zero-crossing point moment detected based on the comparator may, due to the error in the actual value, judge a zero-crossing point where the actual fundamental frequency signal value has not yet reached the zero-crossing phase, losing the normal zero-crossing point judgment ability. In these working conditions, software zero-crossing detection based on the fast Fourier transform will not judge a zero-crossing point with a large error and presents a value close to the actual zero-crossing moment. At the same time, in engineering applications, the calculation time of the algorithm, the action time of the relay, etc. will have a certain impact on the zero-crossing detection at the commutation execution terminal, resulting in the inability to find the correct zero-crossing point. The zero-crossing switching strategy of the present invention's solution will consider various delays in the entire process during the relay driving process after zero-crossing detection and introduce them into the zero-crossing point prediction process, so that there will be no large error between the final action moment of the relay and the actual zero-crossing point of the detection signal.

[0085] This reflects the benefits of the zero-crossing switching strategy's attention to multiple methods for improving the reliability of zero-crossing point moment judgment. Such a zero-crossing switching strategy can not only quickly detect the zero-crossing moment but also effectively and errorlessly prevent obvious errors in zero-crossing detection judgment caused by algorithm and device errors. In particular, it solves the interference problem of zero-crossing detection for steep and extremely fast zero-crossing waveforms and flat-shoulder multi-zero-crossing waveforms, ultimately improving the zero-crossing switching ability of the commutation execution terminal and reducing the risk of arcing and damage to equipment in the power grid.

[0086] Further, during the commutation execution process, in addition to the cut-out action, an in-cut is also required to achieve the three-phase balance of the power grid. The same zero-point detection method is also used for the in-cut phase voltage signal to obtain the target zero-crossing moment, so that the commutation execution terminal completes the in-cut action. After the in-cut is completed, it is also necessary to count the relay action delay time of the in-cut phase. For the counted relay action delay time Δt of the in-cut phase 0 Perform a weighted average with the relay action delay time Δt stored in the system to obtain a new relay action delay time Δt', and replace the original relay action delay time stored in the system.

[0087] Specifically, during the cut-in process, the current signal is first detected until its zero-crossing point, and then the voltage signal is detected. This ensures that there is no simultaneous connection between phases during cut-in and cut-out, preventing short circuits. After the signal acquisition and processing are completed, the current and voltage signals are detected in sequence, which can ensure that the time difference between cut-out and cut-in does not exceed 20 ms. This not only prevents power-off hazards to sensitive loads but also ensures the rapidity of detecting the zero-crossing moment.

[0088] In addition to focusing on the dispersive delay of the actuator, the above commutation switching method also considers various delay factors such as action signal communication, program operation, and signal sampling during the entire three-phase unbalance adjustment process, enabling the commutation execution terminal to accurately perform switching actions such as cut-in and cut-out at the zero-crossing point.

[0089] Combined with FIGS. 3-5, the zero-crossing switching strategy of the commutation execution terminal applying the present invention is described for predicting and judging the zero-crossing points of various different voltage signals of the commutation execution terminal.

[0090] Combined with FIG. 3, the zero-crossing detection method of the commutation execution terminal of the present invention is described for predicting and judging the zero-crossing point prediction effect under standard signals when the commutation execution terminal is connected to the power grid.

[0091] As Figure 3a shown, the signals of the commutation execution terminal are acquired at a sampling frequency f = 12.8 kHz. Before 23 ms, the commutation execution terminal is in a normal operating state. After 23 ms, the zero-crossing switching algorithm of the commutation execution terminal is started, and signal information acquisition begins. After 43 ms, after one cycle of the fundamental wave 50 Hz for 20 ms, the signal information acquisition is completed, and the software zero-crossing detection algorithm is started to calculate and process the acquired information and predict the zero-crossing point. After 60 ms, the zero-crossing detection algorithm calculation is completed, the comparator interrupt is opened, and the software and hardware jointly predict and judge the zero-crossing point. Around 63 ms, the C-phase signal crosses zero. Around 67 ms, the B-phase signal crosses zero.

[0092] The signal is analyzed by fast Fourier transform, and the amplitude spectrum and phase spectrum of the signal in the time-frequency domain are obtained. The power frequency information is extracted from it for judgment, and the zero-crossing time based on the software zero-crossing detection algorithm is obtained as Figure 3b shown. The software zero-crossing detection algorithm judges the zero-crossing moment by the phase of the sampled signal. When the phase of the signal reaches near the phase corresponding to the zero-crossing moment, it is considered that the zero-crossing is detected. Under standard signals, there is no interference from harmonics to the zero-crossing detection. The amplitude deviation near the zero-crossing point judged by the phase of the signal is not large, and a relatively accurate zero-crossing moment can be obtained. The signal is compared and analyzed with the zero signal through a comparator, and the zero-crossing moment based on the hardware comparator interrupt is obtained as Figure 3cAs shown in the figure. The hardware comparator interrupt detection determines the zero-crossing moment by the amplitude of the sampling signal. When the amplitude of the signal reaches near the amplitude corresponding to the zero-crossing moment, it is considered that the zero-crossing is detected. Under the standard signal, there is no interference from harmonics to the zero-crossing detection. Near the zero-crossing point judged by the amplitude of the signal, the phase deviation is not very large, and a relatively accurate zero-crossing moment can be obtained.

[0093] Such a complementary process of jointly judging the zero-crossing by software and hardware enables an output of 0 level when the signal does not cross zero and an output of 1 level when the signal crosses zero, as Figure 3d shown. The results obtained by the two methods are jointly used to judge whether the signal of the commutation execution terminal crosses zero. When neither the software nor the hardware method detects that the signal crosses zero, the system outputs 0, judging that the signal does not cross zero, and continues to perform the zero-crossing detection of the commutation execution terminal signal in the next time period; when only the software detection algorithm or only the hardware comparator detects that the signal crosses zero, the signal 0 is still output, judging that the voltage signal does not cross zero, and continues to perform the zero-crossing detection of the commutation execution terminal signal in the next time period; when both the software and hardware methods detect that the signal crosses zero, it is judged that the signal of the commutation execution terminal has crossed zero during this time period, and a disconnection or closing signal is sent to the relay of the corresponding phase in combination with the corresponding delay. In order to ensure that the zero-crossing point of the signal can be found, the software zero-crossing detection algorithm will judge that the zero-crossing condition is reached when the signal phase is close to the zero-crossing, and then it is considered that the zero-crossing is reached when the hardware comparator detects the zero-crossing. From Figure 3d the results shown, the software and hardware zero-crossing detection methods can give a correct low-level indication for the normal signal when it does not cross zero, a correct high-level indication for the signal when it crosses zero, and a correct low-level indication for the non-actual zero-crossing moments in the flat-shoulder multi-zero-crossing waveform, steep and extremely fast zero-crossing waveform, etc. Therefore, this detection method can accurately distinguish the zero-crossing moment and non-zero-crossing moment of the signal in the commutation execution terminal.

[0094] Combined with Figure 4, the zero-crossing detection strategy of the commutation execution terminal of the present invention is applied to the prediction and judgment effect of the zero-crossing point under the flat-shoulder multi-zero-crossing waveform signal of the commutation execution terminal connected to the power grid.

[0095] As Figure 4a shown, the commutation execution terminal signal is acquired at a sampling frequency f = 12.8 kHz. Before 27 ms, the commutation execution terminal is in a normal operating state. After 27 ms, the zero-crossing switching algorithm of the commutation execution terminal is started, and the signal information is collected. After 47 ms, after one cycle of the fundamental wave of 50 Hz for 20 ms, the signal information collection is completed, and the software zero-crossing detection algorithm is started to calculate and process the collected information and predict the zero-crossing point. After 60 ms, the zero-crossing detection algorithm calculation is completed, the comparator interrupt is opened, and the software and hardware jointly predict and judge the zero-crossing point. Around 65 ms, the C-phase signal crosses zero. Around 89 ms, the B-phase signal crosses zero.

[0096] Analyze the signal through fast Fourier transform, obtain the amplitude spectrum and phase spectrum of the signal in the time-frequency domain, extract the power frequency information from it and make a judgment based on this, and obtain the zero-crossing time based on the software zero-crossing detection algorithm as Figure 4b shown. The software zero-crossing detection algorithm judges the zero-crossing moment from the phase of the sampled signal. When the phase of the signal reaches near the phase corresponding to the zero-crossing moment, it is considered that zero-crossing is detected. In the case of a flat-shoulder multi-zero-crossing waveform signal, the harmonics have little interference on the software zero-crossing point detection. The amplitude deviation near the zero-crossing point judged by the signal phase is not large, and a relatively accurate zero-crossing moment can be obtained. Compare the signal with the zero signal through a comparator for analysis, and obtain the zero-crossing moment based on the interruption of the hardware comparator as Figure 4c shown. The hardware comparator interruption detection judges the zero-crossing moment from the amplitude of the sampled signal. When the amplitude of the signal reaches near the amplitude corresponding to the zero-crossing moment, it is considered that zero-crossing is detected. In this harmonic-containing signal, the harmonics have a greater interference on the zero-crossing point detection. The phase deviation near the zero-crossing point judged by the signal amplitude is large, and the joint cooperation of software zero-crossing detection is required to reduce the deviation and ensure the correctness of the zero-crossing detection method for the judgment result of the zero-crossing moment.

[0097] Such a complementary process of jointly judging zero-crossing by software and hardware enables the output of 0 level when the signal has not crossed zero and 1 level when the signal has crossed zero, as Figure 4d shown. The results obtained by the two methods are jointly used to judge whether the signal of the commutation execution terminal has crossed zero. When neither the software nor the hardware method detects that the signal has crossed zero, the system outputs 0, judges that the signal has not crossed zero, and continues to perform the zero-crossing detection of the signal of the commutation execution terminal in the next time period; when only the software detection algorithm or only the hardware comparator detects that the signal has crossed zero, the signal 0 is still output, judges that the signal has not crossed zero, and continues to perform the zero-crossing detection of the signal of the commutation execution terminal in the next time period; when both the software and hardware methods detect that the signal has crossed zero, it is judged that the signal of the commutation execution terminal has crossed zero during this time period, and a disconnection or closing signal is sent to the relay of the corresponding phase in combination with the corresponding delay. In order to ensure that the zero-crossing point of the signal can be found, the software zero-crossing detection algorithm will judge that the zero-crossing condition is reached when the signal phase is close to the zero-crossing, and then it is considered that the zero-crossing is reached when the hardware comparator detects the zero-crossing. From Figure 3d the results shown, the software and hardware zero-crossing detection methods can give correct low-level indications for the normal signal when it has not crossed zero, correct high-level indications for the signal when it has crossed zero, and correct low-level indications for non-actual zero-crossing moments in flat-shoulder multi-zero-crossing waveforms, steep and extremely fast zero-crossing waveforms, etc. Therefore, this detection method can more accurately distinguish the zero-crossing moment and non-zero-crossing moment of the signal in the commutation execution terminal.

[0098] Combined with Figure 5, the zero-crossing detection method for the commutation execution terminal described is applied to predict and judge the zero-crossing point of the commutation execution terminal connected to the power grid under a steep and extremely fast zero-crossing waveform.

[0099] As Figure 5a shown, the commutation execution terminal signal is acquired at a sampling frequency f = 12.8 kHz. Before 22 ms, the commutation execution terminal is in a normal operating state. After 22 ms, the zero-crossing switching algorithm of the commutation execution terminal is started, and signal information acquisition begins. After 42 ms, after one cycle of the fundamental wave of 50 Hz for 20 ms, the signal information acquisition is completed, and the software zero-crossing detection algorithm is started to calculate and process the acquired information and predict the zero-crossing point. After 60 ms, the zero-crossing detection algorithm calculation is completed, the comparator interrupt is opened, and both software and hardware jointly predict and judge the zero-crossing point. Around 65 ms, the C-phase signal crosses zero. Around 78 ms, the B-phase signal crosses zero.

[0100] The signal is analyzed by fast Fourier transform, and the amplitude spectrum and phase spectrum of the signal in the time-frequency domain are obtained. The power frequency information is extracted from it for judgment, and the zero-crossing time based on the software zero-crossing detection algorithm is obtained as Figure 5b shown. The software zero-crossing detection algorithm judges the zero-crossing moment by the phase of the sampling signal. When the phase of the signal reaches near the phase corresponding to the zero-crossing moment, it is considered that the zero-crossing is detected. Under this harmonic-containing signal, the harmonic has a large interference on the software zero-crossing detection, and the amplitude deviation is large near the zero-crossing point judged by the phase of the signal. The signal is compared and analyzed with the zero signal through a comparator, and the zero-crossing moment based on the hardware comparator interrupt is obtained as Figure 5c shown. The hardware comparator interrupt detection judges the zero-crossing moment by the amplitude of the sampling signal. When the amplitude of the signal reaches near the amplitude corresponding to the zero-crossing moment, it is considered that the zero-crossing is detected. Under this harmonic-containing signal, the harmonic has little interference on the zero-crossing detection, and the phase deviation is small near the zero-crossing point judged by the amplitude of the signal, and a relatively accurate zero-crossing moment can be obtained. In this working condition, the accuracy of software detection alone is insufficient, and the joint cooperation of the hardware comparator is required to reduce the deviation and ensure the correctness of the judgment result of the zero-crossing detection method for the zero-crossing moment.

[0101] Such a complementary process of jointly judging zero-crossing by software and hardware enables the output of 0 level when the signal does not cross zero and 1 level when the signal crosses zero, as Figure 5dAs shown, the results obtained by the two methods are jointly used to determine whether the signal of the commutation execution terminal crosses zero. When neither the software nor the hardware method detects that the signal crosses zero, the system outputs 0, determines that the signal does not cross zero, and continues to perform the zero-crossing detection of the commutation execution terminal signal in the next time period; when only the software detection algorithm or only the hardware comparator detects that the signal crosses zero, the signal 0 is still output, determines that the signal does not cross zero, and continues to perform the zero-crossing detection of the commutation execution terminal signal in the next time period; when both the software and hardware methods detect that the signal crosses zero, it is determined that the signal of the commutation execution terminal crosses zero during this time period, and a disconnection or closing signal is sent to the relay of the corresponding phase. In order to ensure that the zero-crossing point of the signal can be found, the software zero-crossing detection algorithm determines that the zero-crossing condition is reached when the signal phase is close to crossing zero, and then determines that the zero-crossing is reached when the hardware comparator detects the zero-crossing. From Figure 3d As shown in the results, the software and hardware zero-crossing detection methods can give correct low-level indications for the moments when the signal does not cross zero, can give correct high-level indications for the moments when the signal crosses zero, and can give correct low-level indications for the non-actual zero-crossing moments in flat-shoulder multi-zero-crossing waveforms, steep and extremely fast zero-crossing waveforms, etc. Therefore, this detection method can accurately distinguish the zero-crossing moments and non-zero-crossing moments of the signal in the commutation execution terminal.

[0102] As shown in FIGS. 3 to 5, the zero-crossing switching strategy of the commutation execution terminal provided by the present invention obtains the relevant characteristics of the signal through time-frequency domain transformation, realizes reliable and fast zero-crossing switching, and the software and hardware combination method greatly improves the accuracy of zero-crossing detection, solves the problem of unable to detect the correct zero-crossing caused by harmonic characteristics, effectively prevents the damage and safety threats brought by non-zero-crossing switching to the power grid and the operation of the commutation execution terminal, greatly extends the operation time and life of the commutation execution terminal equipment, improves the smooth commutation ability of the commutation execution terminal, and improves the ability of the commutation execution terminal to operate safely and stably.

[0103] Combined with FIG. 6, the zero-crossing prediction and judgment effect of the zero-crossing switching strategy of the commutation execution terminal of the present invention applied to the case of frequency fluctuation is described.

[0104] As Figure 6a shown, before 22 ms, the commutation execution terminal is in a normal operation state. After 22 ms, the zero-crossing switching algorithm of the commutation execution terminal is started, and signal information is collected. After 42 ms, after one cycle of the fundamental wave of 50 Hz for 20 ms, the signal information collection is completed, and the software zero-crossing detection algorithm is started to calculate and process the collected information and predict the zero-crossing point. After 60 ms, the zero-crossing detection algorithm calculation is completed, the comparator interrupt is opened, and the software and hardware jointly predict and judge the zero-crossing point. At about 64 ms, the signal crosses zero. The signal waveform is 49 Hz.

[0105] Analyze the signal through fast Fourier transform, obtain the amplitude spectrum and phase spectrum of the signal in the time-frequency domain, extract the power frequency information from it and make a judgment based on this, and obtain the zero-crossing time based on the software zero-crossing detection algorithm as Figure 6b shown. The software zero-crossing detection algorithm judges the zero-crossing moment from the phase of the sampled signal. When the phase of the signal reaches near the phase corresponding to the zero-crossing moment, it is considered that zero-crossing is detected. Under the frequency fluctuation signal, it has a certain impact on the software zero-crossing detection, resulting in a certain error in the zero-crossing point predicted by the software. Compare the signal with the zero signal through a comparator for analysis, and obtain the zero-crossing moment based on the hardware comparator interruption as Figure 6c shown. The hardware comparator interruption detection judges the zero-crossing moment from the amplitude of the sampled signal. When the amplitude of the signal reaches near the amplitude corresponding to the zero-crossing moment, it is considered that zero-crossing is detected. Under this non-standard power frequency signal, the interference to the comparator detection is very small, and the phase deviation is very small near the zero-crossing point judged by the signal amplitude, and a relatively accurate zero-crossing moment can be obtained. In this working condition, the accuracy of software detection alone is not enough to correctly predict the zero-crossing point, and the cooperation of the hardware comparator is needed to reduce the deviation and ensure the correctness of the judgment result of the zero-crossing detection method for the zero-crossing moment.

[0106] Such a complementary process of jointly judging zero-crossing by software and hardware enables the output of 0 level when the signal has not crossed zero and 1 level when the signal has crossed zero, as Figure 6d shown. The results obtained by the two methods are jointly used to judge whether the signal of the commutation execution terminal has crossed zero. When neither the software nor the hardware method detects that the signal has crossed zero, the system outputs 0, judges that the signal has not crossed zero, and continues to perform the zero-crossing detection of the commutation execution terminal signal in the next time period; when only the software detection algorithm or only the hardware comparator detects that the signal has crossed zero, the signal 0 is still output, judges that the signal has not crossed zero, and continues to perform the zero-crossing detection of the commutation execution terminal signal in the next time period; when both the software and hardware methods detect that the signal has crossed zero, it is judged that the signal of the commutation execution terminal has crossed zero during this time period, and a disconnection or closing signal is sent to the relay of the corresponding phase in combination with the corresponding delay. In order to ensure that the zero-crossing point of the signal can be found, the software zero-crossing detection algorithm will judge that the zero-crossing condition is reached when the signal phase is close to the zero-crossing, and then it is considered that the zero-crossing is reached when the hardware comparator detects the zero-crossing. From the Figure 6d shown results, the software and hardware zero-crossing detection methods can give correct low-level indications for the normal signal when it has not crossed zero, correct high-level indications for the signal when it has crossed zero, and correct low-level indications for the non-actual zero-crossing moments of the signal under frequency fluctuation conditions. Therefore, this detection method can accurately distinguish the zero-crossing moment and non-zero-crossing moment of the signal in the commutation execution terminal.

[0107] The commutation switching method provided by the present invention includes: obtaining a signal to be detected, and obtaining a target zero-crossing moment by using the above-mentioned zero-crossing detection method; calculating the target relay action delay time; determining a target signal sending moment based on the target zero-crossing moment and the target relay action delay time, and performing commutation switching at the target zero-crossing moment based on the target signal sending moment. By continuously correcting the delay time of the target relay, the relay can complete the zero-crossing action more accurately, and the risk of generating arcs and inrush currents during the commutation process is minimized, protecting the contacts of the relay, extending the service life of the relay, preventing the interruption failure caused by arcing, reducing the impact on the power grid.

[0108] An embodiment of the present invention further provides a zero-crossing detection system, as Figure 7 shown, including:

[0109] A first acquisition module 10, configured to acquire a signal to be detected. For the detailed content, refer to the relevant description of step S10 in the above embodiment, which will not be elaborated here.

[0110] A first calculation module 11, configured to perform zero-crossing detection on the signal to be detected by using multiple zero-crossing detection methods, and obtain zero-crossing detection moments corresponding to the zero-crossing detection methods. For the detailed content, refer to the relevant description of step S11 in the above embodiment, which will not be elaborated here.

[0111] A first screening module 12, configured to screen out a set of candidate zero-crossing moments with all consistent detection results from the zero-crossing detection moments corresponding to the zero-crossing detection methods. For the detailed content, refer to the relevant description of step S12 in the above embodiment, which will not be elaborated here.

[0112] A first processing module 13, configured to determine a target zero-crossing moment from the set of candidate zero-crossing moments based on the time sequence. For the detailed content, refer to the relevant description of step S13 in the above embodiment, which will not be elaborated here.

[0113] An embodiment of the present invention further provides a commutation switching system, as Figure 8 shown, including:

[0114] A second processing module 20, configured to acquire a signal to be detected, and obtain a target zero-crossing moment by using the zero-crossing detection method of the first aspect of the present invention. For the detailed content, refer to the relevant description of step S20 in the above embodiment, which will not be elaborated here.

[0115] A second calculation module 21, configured to calculate the target relay action delay time. For the detailed content, refer to the relevant description of step S21 in the above embodiment, which will not be elaborated here.

[0116] The first switching module 22 is configured to determine the target signal sending moment based on the target zero moment and the target relay operation delay time, and perform phase conversion switching at the target zero moment based on the target signal sending moment. For the detailed content, please refer to the relevant description of step S22 in the above embodiments, which will not be elaborated here.

[0117] An embodiment of the present invention further provides a phase conversion switching device, such as Figure 9 shown, including: a sampling device 1, a software zero point detection device 2, a hardware zero point detection device 3, a controller 4, and a phase conversion switching actuator 5, where

[0118] The sampling device 1 is configured to collect the signal to be detected of the device to be switched, and send the signal to be detected to the software zero point detection device 2 and the hardware zero point detection device 3.

[0119] The software zero point detection device 2 is configured to perform zero point detection on the signal to be detected to obtain the first zero moment, and send the first zero moment to the controller 4.

[0120] The hardware zero point detection device 3 is configured to perform zero point detection on the signal to be detected to obtain the second zero moment, and send the second zero moment to the controller 4.

[0121] The controller 4 is configured to compare the first zero moment and the second zero moment, generate a phase conversion switching control signal, and send the phase conversion switching control signal to the phase conversion switching actuator 5.

[0122] The phase conversion switching actuator 5 is configured to perform a phase conversion switching action on the device to be switched according to the phase conversion switching control signal.

[0123] In a specific embodiment, the above phase conversion switching device further includes: a communication module 6, an interaction module 7, and a drive circuit 8, where

[0124] The communication module 6 is configured to receive the switching instruction of the superior control device, and send the switching instruction to the controller 4, and the controller 4 is configured to generate a phase conversion switching control signal according to the switching instruction.

[0125] The interaction module 7 is configured to receive the manual operation switching instruction, and send the switching instruction to the controller 4, and the controller 4 is configured to generate a phase conversion switching control signal according to the switching instruction.

[0126] The drive circuit 8 is configured to drive the phase conversion switching actuator 5 to act according to the phase conversion switching control signal sent by the controller 4.

[0127] In an embodiment of the present invention, the input side of the commutation execution terminal is connected to the AC power grid in a three-phase four-wire system. Voltage and current signals are input into the software zero-crossing detection device 2 and the hardware zero-crossing detection device 3 through the sampling device 1. Then, the zero-crossing detection devices 2 and 3 perform zero-crossing detection on the voltage and current signals to obtain the first zero-crossing moment and the second zero-crossing moment, and send the first zero-crossing moment and the second zero-crossing moment to the controller 4 to generate a commutation switching control signal. During normal operation, the signals output by the sampling device 1 and the hardware zero-crossing detection device 3 of the commutation execution terminal are not analyzed and detected, and the commutation execution terminal does not actively switch, maintaining stable operation. If the communication module 6 receives an instruction from the superior or sends an instruction through the manual operation interaction module 7, it starts to collect. The controller 4 controls the signals of one cycle to be analyzed by the sampling device 1 and the software zero-crossing detection device 2 in sequence to obtain their frequency spectra and phase spectra. Subsequently, according to the aforementioned zero-crossing detection process, the software-detected zero-crossing is obtained, and in combination with the hardware-detected zero-crossing obtained by the hardware zero-crossing detection device 3, the drive circuit 8 controls the commutation switching actuator 5 to act when the phase where it is located passes through zero, finally realizing the switching of the phase where the load is located, eliminating the three-phase imbalance phenomenon in the power grid and avoiding the generation of arcs during the process, avoiding the failure of breaking due to arcing and causing a short circuit, and extending the service life of the commutation execution terminal. In an embodiment of the present invention, the commutation switching actuator 5 is a relay, and only this is taken as an example, not limited thereto.

[0128] Further, in actual engineering applications, the action time of the relay has a certain dispersion, and its action time will change with the working scenario, service time, etc., which affects the delay estimation in the zero-crossing switching strategy. In the present invention, the action time of the relay for each action execution is statistically analyzed, and it is weighted and averaged with the previously statistically averaged action time of the relay as the correction for considering the delay when the relay acts later. Under such a delay correction algorithm, the weight of the most recent relay action time is the largest, and the weight of the older relay action time is smaller. This not only takes into account the situation that the relay action times are more similar within a similar time period but also avoids misjudgment of the delay estimation when the relay action time suddenly changes, enabling the zero-crossing switching strategy of the commutation execution terminal to ensure that the relay acts at the zero-crossing moment of the signal in the phase where it is located to complete the switching.

[0129] The commutation switching device provided by the present invention includes: a sampling device, a software zero-crossing detection device, a hardware zero-crossing detection device, a controller, and a commutation switching actuator. Among them, the sampling device is used to collect the signal to be detected of the device to be switched, and send the signal to be detected to the software zero-crossing detection device and the hardware zero-crossing detection device; the hardware zero-crossing detection device is used to perform zero-crossing detection on the signal to be detected to obtain the first zero-crossing moment, and send the first zero-crossing moment to the controller; the software zero-crossing detection device is used to perform zero-crossing detection on the signal to be detected to obtain the second zero-crossing moment, and send the second zero-crossing moment to the controller; the controller is used to compare the first zero-crossing moment and the second zero-crossing moment, generate a commutation switching control signal, and send the commutation switching control signal to the commutation switching actuator; the commutation switching actuator is used to perform commutation switching actions on the device to be switched according to the commutation switching control signal. By adopting a combination of multiple zero-crossing detection methods to perform zero-crossing detection on the signal to be detected, even when the detection effect of one method is poor, the other method can still be used as a supplement, so that for various waveforms with harmonics and frequency fluctuations in the power grid, the finally detected zero-crossing still has a relatively accurate result. Through multi-dimensional precise zero-crossing detection, the distortion problem of the power signal caused by the randomness of diverse system loads and dynamic interference characteristics is effectively solved, and the problem that the existing zero-crossing detection scheme cannot meet the requirements of precise zero-crossing identification in the complex scenario of diverse load dynamic operation is solved, improving the accuracy of zero-crossing switching of the commutation switching device.

[0130] An embodiment of the present invention also provides a computer device, as Figure 10 shown, the device may include a processor 61 and a memory 62, where the processor 61 and the memory 62 may be connected through a bus or other means, Figure 10 Taking the connection through the bus as an example.

[0131] The processor 61 may be a central processing unit (CPU). The processor 61 may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. chips, or combinations of the above types of chips.

[0132] The memory 62, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the corresponding program instructions / modules in the embodiments of the present invention. The processor 61 executes various functional applications and data processing of the processor by running the non-transitory software programs, instructions, and modules stored in the memory 62, that is, to implement the zero-crossing detection method or the phase-change switching method in the above method embodiments.

[0133] The memory 62 may include a program storage area and a data storage area. Among them, the program storage area can store an operating system and application programs required for at least one function; the data storage area can store data created by the processor 61, etc. In addition, the memory 62 may include high-speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state storage devices. In some embodiments, the memory 62 may optionally include a memory remotely disposed relative to the processor 61, and these remote memories can be connected to the processor 61 through a network. Examples of the above network include but are not limited to the Internet, an enterprise intranet, an enterprise internal network, a mobile communication network, and combinations thereof.

[0134] One or more modules are stored in the memory 62 and, when executed by the processor 61, implement the zero-crossing detection method or the phase-change switching method provided in the embodiments of the present invention.

[0135] For specific details of the above computer device, reference can be made to Figure 1 - the corresponding relevant descriptions and effects in the embodiments shown in FIG. 6, which will not be elaborated here.

[0136] Those skilled in the art can understand that to implement all or part of the processes in the above method embodiments, it can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the above method embodiments. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (RAM), a flash memory, a hard disk drive (abbreviation: HDD), or a solid-state drive (SSD), etc.; the storage medium can also include a combination of the above types of memories.

[0137] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or variations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A zero - point detection method, characterized in that, it includes: Obtain the signal to be detected; Perform zero - point detection on the signal to be detected by using multiple zero - point detection methods to obtain the zero - point detection times corresponding to each zero - point detection method; Select a set of candidate zero - point times with consistent detection results from the zero - point detection times corresponding to each zero - point detection method; Based on the time sequence, determine the target zero - point time from the set of candidate zero - point times; The step of performing zero - point detection on the signal to be detected by using multiple zero - point detection methods includes: performing zero - point detection on the signal to be detected by using the first zero - point detection method; The step of performing zero - point detection on the signal to be detected by using the first zero - point detection method includes: Perform fast Fourier transform calculation on the signal to be detected to obtain the phase spectrum corresponding to the signal to be detected in the time - frequency domain; According to the phase components of the voltage and current fundamental waves corresponding to the power frequency in the phase spectrum, obtain the first zero - point detection time corresponding to the first zero - point detection method; The step of obtaining the first zero - point detection time corresponding to the first zero - point detection method according to the phase components of the voltage and current fundamental waves corresponding to the power frequency in the phase spectrum includes: calculating the zero - crossing time through the following formula: Among them, Tu is the zero-crossing moment of cutting in, k is the number of cycles, is the phase component of the fundamental voltage; Among them, Ti is the zero-crossing moment of the cut-off, k is the number of cycles, is the phase component of the fundamental current.

2. The zero - point detection method according to claim 1, characterized in that, The step of performing zero - point detection on the signal to be detected by using multiple zero - point detection methods includes: performing zero - point detection on the signal to be detected by using the second zero - point detection method; The step of performing zero - point detection on the signal to be detected by using the second zero - point detection method includes: Perform zero - point detection on the signal to be detected by using the comparator interruption method to obtain the second zero - point detection time corresponding to the second zero - point detection method.

3. A phase - change switching method, characterized in that, it includes: Obtain the signal to be detected, and use the zero - point detection method according to any one of claims 1 - 2 to obtain the target zero - point time; Calculate the target relay action delay time; Based on the target zero - point time and the target relay action delay time, determine the target signal sending time, and perform phase - change switching at the target zero - point time based on the target signal sending time.

4. The phase - change switching method according to claim 3, characterized in that, The step of calculating the target relay action delay time includes: Collect the historical relay action delay time and obtain the preset relay action delay time; Sum and average the historical relay action delay time and the preset relay action delay time to determine the target relay action delay time.

5. A zero - point detection system, characterized in that, it includes: A first acquisition module for obtaining the signal to be detected; A first calculation module for performing zero - point detection on the signal to be detected by using multiple zero - point detection methods to obtain the zero - point detection times corresponding to each zero - point detection method; A first screening module for selecting a set of candidate zero - point times with consistent detection results from the zero - point detection times corresponding to each zero - point detection method; A first processing module for determining the target zero - point time from the set of candidate zero - point times based on the time sequence; Performing zero - point detection on the signal to be detected by using multiple zero - point detection methods includes: performing zero - point detection on the signal to be detected by using a first zero - point detection method; The performing zero - point detection on the signal to be detected by using a first zero - point detection method includes: Performing a fast Fourier transform calculation on the signal to be detected to obtain the phase spectrum corresponding to the signal to be detected in the time - frequency domain; Based on the phase components of the fundamental voltage and current corresponding to the power frequency in the phase spectrum, obtaining the first zero - point detection moment corresponding to the first zero - point detection method; The obtaining the first zero - point detection moment corresponding to the first zero - point detection method based on the phase components of the fundamental voltage and current corresponding to the power frequency in the phase spectrum includes: calculating the zero - crossing moment through the following formula: wherein, T u is the zero-crossing moment of entry, k is the number of cycles, is the phase component of the fundamental voltage; wherein, T i is the zero-crossing moment cut out, k is the number of cycles, is the phase component of the fundamental current.

6. A commutation switching system, Characterized in that, It includes: A second processing module, configured to obtain a signal to be detected and obtain a target zero - point moment by using the zero - point detection method described in any one of claims 1 - 2; A second calculation module, configured to calculate the target relay action delay time; A first switching module, configured to determine a target signal sending moment based on the target zero - point moment and the target relay action delay time, and perform commutation switching at the target zero - point moment based on the target signal sending moment.

7. A commutation switching device, Characterized in that, It includes: A sampling device, a software zero - point detection device, a hardware zero - point detection device, a controller, and a commutation switching actuator, where, The sampling device is configured to collect a signal to be detected of a device to be switched and send the signal to be detected to the software zero - point detection device and the hardware zero - point detection device; The hardware zero - point detection device is configured to perform zero - point detection on the signal to be detected to obtain a first zero - point moment and send the first zero - point moment to the controller; The software zero - point detection device is configured to perform zero - point detection on the signal to be detected to obtain a second zero - point moment and send the second zero - point moment to the controller; The controller is configured to compare the first zero - point moment and the second zero - point moment, generate a commutation switching control signal, and send the commutation switching control signal to the commutation switching actuator; The commutation switching actuator is configured to perform a commutation switching action on the device to be switched according to the commutation switching control signal; Performing zero - point detection on the signal to be detected by using a first zero - point detection method includes: Performing a fast Fourier transform calculation on the signal to be detected to obtain the phase spectrum corresponding to the signal to be detected in the time - frequency domain; Based on the phase components of the fundamental voltage and current corresponding to the power frequency in the phase spectrum, obtaining the first zero - point detection moment corresponding to the first zero - point detection method; The obtaining the first zero - point detection moment corresponding to the first zero - point detection method based on the phase components of the fundamental voltage and current corresponding to the power frequency in the phase spectrum includes: calculating the zero - crossing moment through the following formula: Among them, T u is the zero-crossing moment of entry, k is the number of cycles, is the phase component of the fundamental voltage; Among them, T i is the zero-crossing moment of the cut-off, k is the number of cycles, is the phase component of the fundamental current.

8. A computer - readable storage medium, Characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the zero-point detection method according to any one of claims 1-2 or the commutation switching method according to any one of claims 3-4.

9. A computer device, characterized in that it comprises: a memory and a processor, the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the zero-point detection method according to any one of claims 1-2 or the commutation switching method according to any one of claims 3-4 by executing the computer instructions.

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