Synchronization Method for Flyback Micro-inverter Grid Connection by Square Wave Harmonic Decomposition

Abstract

The present invention discloses a synchronization method for realizing the grid connection of a flyback micro-inverter by decomposing square-wave harmonics, which includes: obtaining a working electrical signal synchronized with the target grid; obtaining a square-wave signal with a frequency consistent with that of the working electrical signal according to the working electrical signal; performing Fourier decomposition on the square-wave signal to obtain a fundamental wave signal and harmonic signals, wherein the fundamental wave signal is a sine-wave signal synchronized with the frequency and phase of the square-wave signal, and the frequency of the harmonic signals is an integer multiple of the frequency of the fundamental wave signal; performing phase locking on the fundamental wave signal to obtain a sine wave synchronized with the working electrical signal; modulating the sine wave to obtain a sine pulse-width modulation wave; based on the sine pulse-width modulation wave, controlling the flyback micro-inverter to output a target alternating current with the same frequency and phase as the modulation wave to the target grid or electrical equipment. In this way, the problem of how to synchronize the alternating current with the target grid when there is only a grid-synchronized square-wave signal is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of flyback inverter grid connection, and particularly relates to a synchronization method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition. Background Art

[0002] Due to the widespread application scenarios of photovoltaic power generation and the wide range of usage areas, the frequency standards in different application scenarios and different usage areas are different. Therefore, the alternating current output by the inverter may be asynchronous with the frequency of the target power grid. However, synchronizing the alternating current output by the inverter with the frequency of the target power grid is an important link for connecting the alternating current output by the inverter to the target power grid. How to synchronize the alternating current with the target power grid has become a technical problem to be solved urgently. Summary of the Invention

[0003] The main object of the present invention is to propose a synchronization method and controller for realizing flyback micro-inverter grid connection by square wave harmonic decomposition, aiming to solve the problem of how to synchronize the alternating current with the target power grid.

[0004] In a first aspect, the present invention proposes a synchronization method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition, including:

[0005] Obtaining a working electrical signal synchronized with the target power grid;

[0006] According to the working electrical signal, obtaining a square wave signal with a frequency consistent with that of the working electrical signal;

[0007] Performing Fourier decomposition on the square wave signal to obtain a fundamental wave signal and a harmonic signal, wherein the fundamental wave signal is a sine wave signal synchronized with the frequency and phase of the square wave signal, and the frequency of the harmonic signal is an integer multiple of the frequency of the fundamental wave signal;

[0008] Performing phase locking on the fundamental wave signal to obtain a sine wave synchronized with the working electrical signal;

[0009] Modulating the sine wave to obtain a sine pulse width modulation wave;

[0010] Based on the sine pulse width modulation wave, controlling the flyback micro-inverter to output a target electrical signal with the same frequency and phase as the sine pulse width modulation wave to the target power grid or electrical equipment.

[0011] Further, the working electrical signal is a sine wave signal.

[0012] Further, the step of obtaining a square wave signal with a frequency consistent with that of the working electrical signal according to the working electrical signal includes:

[0013] Obtaining the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal;

[0014] Based on the detected feature point information, a square wave signal with a frequency consistent with that of the working electrical signal is obtained.

[0015] Further, the detected feature point information is the zero-crossing information, peak-crossing information, or valley-crossing information of the working electrical signal.

[0016] Further, the detected feature point information is the zero-crossing information of the working electrical signal;

[0017] The obtaining of the detected feedback information of the working electrical signal to obtain the detected feature point information of the working electrical signal includes:

[0018] Based on the detected feedback information of the working electrical signal by a comparator, the zero-crossing information of the working electrical signal is obtained.

[0019] Further, the obtaining of the detected feedback information of the working electrical signal to obtain the detected feature point information of the working electrical signal includes:

[0020] Based on the detected feedback information of the working electrical signal within a preset time period, the detected feature point information of the working electrical signal is obtained.

[0021] Further, the working electrical signal is a waveform signal with a preset period, the preset period is composed of a first half-period and a second half-period, and the preset time period is the time period corresponding to the first half-period, or the time period corresponding to the second half-period, or the time period corresponding to the preset period.

[0022] Further, the controlling the flyback micro-inverter to the target power grid or electrical equipment based on the sine pulse width modulation wave to output a target electrical signal with a frequency the same as that of the sine pulse width modulation wave includes:

[0023] Based on the control of the micro-inverter switch by the sine pulse width modulation wave, the flyback micro-inverter outputs a target electrical signal with a frequency the same as that of the sine pulse width modulation wave to the target power grid or electrical equipment.

[0024] In a second aspect, the present invention further provides a controller for a flyback micro-inverter. The controller for the flyback micro-inverter includes a processor and a memory. The memory stores a computer program or computer instructions. When the processor calls the computer program or the computer instructions to run, the steps of the above method for realizing synchronous grid connection of the flyback micro-inverter by square wave harmonic decomposition or the method for phase-locking of the square wave signal can be implemented.

[0025] In the embodiments of the present application, the synchronous method and controller for realizing flyback micro-inverter grid connection by square-wave harmonic decomposition can obtain the working electrical signal of the target grid synchronization square wave; obtain a square-wave signal with the same frequency as the working electrical signal according to the working electrical signal; perform Fourier decomposition on the square-wave signal to obtain a fundamental wave signal and a harmonic wave signal, where the fundamental wave signal is a sine-wave signal synchronized with the frequency and phase of the square-wave signal, and the frequency of the harmonic wave signal is an integer multiple of the frequency of the fundamental wave signal; perform phase locking on the fundamental wave signal to obtain a sine wave synchronized with the working electrical signal; modulate the sine wave to obtain a sine pulse-width modulation wave; based on the sine pulse-width modulation wave, control the flyback micro-inverter to the target grid or electrical equipment, and output a target electrical signal with the same frequency and phase as the sine pulse-width modulation wave.

[0026] The beneficial effects of the technical solution of the present invention are as follows: By converting the working signal of the target grid detected by the flyback micro-inverter into a square-wave signal with the same frequency, signal decomposition is performed on the basis of the square-wave signal to obtain the corresponding fundamental wave signal and harmonic wave signal. Phase locking is performed on the fundamental wave signal on the basis of the harmonic wave signal to realize a modulation signal generated according to the working electrical signal of the target grid, that is, a sine pulse-width modulation wave synchronized with the grid. After determining the sine pulse-width modulation wave, the corresponding flyback micro-inverter can be controlled based on the sine pulse-width modulation wave to output the corresponding modulated target electrical signal to the target grid. The target electrical signal can be used to synchronize the alternating current output by the flyback micro-inverter with the target grid, and the flyback micro-inverter can access the corresponding target grid based on the synchronized frequency. In this way, the square-wave signal corresponding to the working electrical signal can be used as the basic tracking signal, and the corresponding fundamental wave signal and harmonic wave signal can be determined according to the square-wave signal. After phase locking the fundamental wave signal, the corresponding sine pulse-width modulation wave is obtained. Based on the sine pulse-width modulation wave, the frequency of the electrical signal output by the flyback micro-inverter to the target grid is modulated to obtain the corresponding target electrical signal, so as to realize the frequency synchronization between the alternating current output by the flyback micro-inverter and the target grid, improve the adaptability between flyback micro-inverters with different frequency standards and the target grid, and also improve the accuracy of modulating the grid-connected alternating current and the accuracy of frequency synchronization with the target grid. Thus, the problem of how to synchronize the frequency between the alternating current output by the flyback micro-inverter and the target grid when there is only a grid synchronization square-wave signal is effectively solved, so that the alternating current of the flyback micro-inverter can be connected to the target grid based on the frequency synchronization between the alternating current and the target grid. In addition, in the present application, the fundamental wave signal is obtained by performing Fourier decomposition on the square-wave signal and phase locking is performed on the fundamental wave signal, so that the problem that the prior art can only perform phase locking on sine-wave signals and cannot perform phase locking on square-wave signals can be solved, and the accuracy of phase locking is improved. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic flowchart of a synchronization method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition disclosed in the embodiments of the present application;

[0029] Figure 2 It is a schematic flowchart of a phase-locked method for a square wave signal disclosed in the embodiments of the present application;

[0030] Figure 3 It is a schematic diagram of a system architecture where the flyback micro-inverter is located disclosed in the embodiments of the present application.

[0031] The realization of the object of the present invention, functional features and advantages will be further described in conjunction with the embodiments and with reference to the drawings. Specific embodiments

[0032] The following will clearly and completely describe the solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] In the following description, "some embodiments" are involved, which describe a subset of all possible embodiments. However, it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict. In the following description, the term "a plurality" refers to at least two.

[0034] In the present invention, the descriptions involving "first", "second", etc. are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein are for the purpose of describing embodiments of this application only and are not intended to limit this application.

[0036] To enable those skilled in the art to better understand the solutions of this application, before further elaborating on the embodiments of this application, the background technology related to the embodiments of this application is elaborated in detail as follows:

[0037] Due to the widespread application scenarios and usage areas of photovoltaic power generation, the frequency standards in different application scenarios and different usage areas are different. For example, the standards for inverters in different countries to convert direct current into corresponding alternating current during photovoltaic power generation can be 50Hz or 60Hz. For different application scenarios, there may be large-scale electrical equipment and small-scale electrical equipment among the electrical equipment, and for large-scale and small-scale electrical equipment, the corresponding frequency standards for the electrical energy that can be connected are different.

[0038] In this regard, since the alternating current converted by the inverter and the electrical equipment do not match in frequency standards in different regions or different scenarios, and electrical energy or equipment with inconsistent frequency standards cannot be connected or used. Therefore, synchronizing different frequency electrical signals is an important link for alternating current to access the target power grid or for electrical equipment to be powered on.

[0039] However, in some related prior arts, achieving synchronization of grid signals often uses a sine wave signal as the basic tracking signal, directly performs a series of modulation methods according to the sine wave signal to obtain corresponding modulation pulses, and modulates the electrical signal to be input or connected, so as to achieve signal synchronization between different frequency electrical signals. However, these electrical signals that are simply modulated based on the sine wave signal without phase-locked synchronization have low accuracy and cannot be synchronized. It is difficult to solve the low compatibility between different alternating currents and the target power grid, as well as between electrical equipment and the target power grid. After modulation, different frequency alternating currents and the target power grid, electrical equipment are still difficult to connect or the electrical equipment still cannot be used.

[0040] To solve the above problems, the embodiments of this application do not use a traditional sine wave signal as the basic tracking signal, but use a square wave signal as the basic tracking signal, and the frequency of this square wave signal is consistent with the frequency of the target power grid. In the embodiments of this application, by performing Fourier decomposition on the square wave signal to obtain a fundamental wave signal and performing phase locking on the fundamental wave signal, the problem that the prior art can only perform phase locking on sine wave signals and cannot perform phase locking on square wave signals can be solved, and the accuracy of phase locking is improved.

[0041] To enable those skilled in the art to better understand the solution of this application, the application environment of the solution of this application will be described and explained first.

[0042] Flyback micro-inverter (also known as: flyback micro-inverter) is a key technology for the modular structure of distributed photovoltaic power generation systems. The flyback micro-inverter is a mainstream design solution for micro-inverters and is based on a flyback converter. In a flyback micro-inverter, current feedback control or peak current control is usually used to achieve current source control of the flyback converter. Among them, in current feedback control, the flyback circuit operates in continuous current mode (CCM), and in peak current control, it operates in boundary continuous current mode (BCM). The advantage of this inverter is that its circuit structure is relatively simple, it can achieve primary and secondary electrical isolation, and solve the leakage current problem.

[0043] The flyback micro-inverter may include a comparator or a digital processor. Among them, the comparator of the flyback micro-inverter can be used to perform zero-crossing detection on the detected electrical signal (sine wave signal) and generate a square wave working signal. The digital processor can execute the steps of the square wave harmonic decomposition to realize the synchronization method for flyback micro-inverter grid connection and the steps of the phase-locking method for square wave signals.

[0044] Specifically, the comparator can perform zero-crossing detection on the detected electrical signal to determine the detection feedback information corresponding to the electrical signal. After determining the detection feedback information, the comparator can send the detection feedback information to the digital processor for further calculation to obtain the corresponding sine wave pulse width modulation wave.

[0045] The above description is a communication example related to a method for realizing synchronization of flyback micro-inverter grid connection by square wave harmonic decomposition and a phase-locking method for square wave signals disclosed in this application, which is for better explaining each step when describing this application and does not limit this application.

[0046] The present invention proposes a method for realizing synchronization of flyback micro-inverter grid connection by square wave harmonic decomposition.

[0047] Please refer to Figure 1 , Figure 1 is a schematic flowchart of a method for realizing synchronization of flyback micro-inverter grid connection by square wave harmonic decomposition disclosed in an embodiment of this application. As Figure 1 shown, the method for realizing synchronization of flyback micro-inverter grid connection by square wave harmonic decomposition may include the following steps.

[0048] Step 101, obtain the working electrical signal of the target power grid.

[0049] Among them, the working electrical signal can be the signal frequency during the storage, transmission, or operation of the target power grid, and the working electrical signal can be a sine wave signal. The target power grid can be the target power source to which alternating current is to be connected, and the alternating current can be the electrical energy output by an inverter after photovoltaic power generation.

[0050] It should be noted that the flyback micro-inverter can detect the working electrical signal of the target power grid, and the flyback micro-inverter can also input alternating current into the target power grid. Before the flyback micro-inverter outputs the alternating current to the target power grid, that is, before the alternating current is connected to the target power grid, it is also possible to determine whether the frequency of the working electrical signal of the target power grid and the frequency of the alternating current are within the same frequency standard.

[0051] Among them, the frequency standard can be a frequency standard distinguished based on different usage regions or different usage scenarios, and the frequency standard can be a preset frequency range.

[0052] In one embodiment, the frequency of the working electrical signal of the target power grid and the frequency of the alternating current can be within the preset range of the same frequency standard. When the frequency of the working electrical signal of the target power grid and the frequency of the alternating current can be within the preset range of the same frequency standard, the alternating current can be connected to the target power grid corresponding to the same frequency standard to achieve synchronous connection of the alternating current to the target power grid.

[0053] In other embodiments, the frequency of the working electrical signal of the target power grid and the frequency of the alternating current can also be of different frequency standards. That is, the frequency of the working electrical signal in the target power grid and the frequency of the electrical signal corresponding to the alternating current can be the frequency values corresponding to different frequency standards. When the frequency of the working electrical signal of the target power grid and the frequency of the alternating current can also be of different frequency standards, the following steps can be performed to synchronize the working electrical signal with the target power grid.

[0054] Exemplarily, the standard frequency corresponding to Region A can be 60 Hz, and the frequencies of the target power grid corresponding to Region A and the electrical signal output by the flyback micro-inverter are within the preset frequency range of 60 Hz. The standard frequency corresponding to Region B can be 50 Hz, and the frequencies of the target power grid corresponding to Region B and the electrical signal output by the flyback micro-inverter are within the preset range of 50 Hz. When the alternating current output by the flyback micro-inverter in Region A is incorporated into the target power grid in Region B, or the alternating current output by the flyback micro-inverter in Region B is incorporated into the target power grid in Region A, the alternating current output by the flyback micro-inverter can be synchronized.

[0055] Step 102: Obtain a square wave synchronization signal with a frequency consistent with the frequency of the working electrical signal according to the working electrical signal.

[0056] Among them, the working electrical signal can be a sine wave signal.

[0057] The square wave signal can be a non-sinusoidal signal with the same frequency as the original working electrical signal. The square wave signal can be a discrete waveform, which is periodic and composed of alternating high-level and low-level signals corresponding to the frequency of the working electrical signal.

[0058] After obtaining the working electrical signal of the target power grid and determining that the frequency of the AC electrical signal output by the flyback micro-inverter is within the range corresponding to different standard frequencies from that of the target power grid, the working electrical signal can be converted into a corresponding square wave signal. Specifically, a sinusoidal wave signal with a periodic waveform can be converted into a square wave signal with a discrete waveform.

[0059] It should be noted that when converting the sinusoidal wave signal into a square wave signal, the square wave signal can be a square wave signal with the same frequency, corresponding amplitude, and corresponding phase as the sinusoidal wave signal of the working electrical signal.

[0060] In some embodiments, the steps of obtaining a square wave signal with the same frequency and phase as the working electrical signal according to the working electrical signal may include: obtaining the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal. According to the characteristic point detection information, a square wave signal synchronized with the working electrical signal is obtained.

[0061] Among them, the characteristic point detection information can be the zero-crossing information, peak-crossing information, or valley-crossing information of the working electrical signal.

[0062] The detection feedback information can be the detection feedback signal obtained by the comparator in the flyback micro-inverter detecting the working electrical signal of the target power grid. The detection feedback signal can be the sinusoidal wave signal corresponding to the working electrical signal. The detection feedback signal can also be the detection signal corresponding to the sinusoidal wave signal corresponding to the working electrical signal. For example, the detection feedback signal can correspond to the positive level (logic "1") in the positive half-cycle of the sinusoidal wave signal and the low level (logic "0") corresponding to the negative half-cycle.

[0063] In some specific embodiments, the characteristic point detection information can be the zero-crossing information of the working electrical signal of the target power grid. Specifically, the steps of obtaining the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal may include obtaining the zero-crossing information of the working electrical signal according to the detection feedback information of the comparator for the working electrical signal.

[0064] In some other embodiments, the steps of obtaining the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal may include obtaining the characteristic point detection information of the working electrical signal according to the detection feedback information of the working electrical signal within a preset time period.

[0065] Among them, the working electrical signal can be a waveform signal with a preset period, which is composed of a first half-period and a second half-period, and the preset time period is the time period corresponding to the first half-period or the second half-period or the preset period.

[0066] Specifically, the preset period can include 0 to π, and π to 2π.

[0067] Step 103: Perform Fourier decomposition on the square wave signal to obtain a fundamental wave signal and harmonic signals.

[0068] Among them, the fundamental wave signal is a sine wave signal with the same frequency as the square wave signal, and the frequency of the harmonic signals is an integer multiple of the frequency of the fundamental wave signal.

[0069] Among them, the fundamental wave signal can be a sine wave signal corresponding to the frequency and the maximum amplitude value of the square wave signal.

[0070] The harmonic signals can be a series of components with frequencies greater than the fundamental wave frequency obtained after performing Fourier series decomposition on the square wave signal, in addition to the fundamental wave signal with the same frequency component as the square wave signal. This part of the electric quantity is called harmonic signals. The ratio between the frequency of the harmonic signals and the frequency of the fundamental wave signal is called the harmonic order, and the harmonic coefficient n = fn / f1.

[0071] Step 104: Perform phase locking on the fundamental wave signal to obtain a sine wave with the same frequency as the working electrical signal.

[0072] Among them, the sine wave can be a modulated wave obtained by performing phase locking on the fundamental wave signal.

[0073] Step 105: Modulate the sine wave to obtain a sine pulse width modulation wave.

[0074] Among them, the sine pulse width modulation wave can be a modulation signal calculated after modulating according to the fundamental wave signal corresponding to the working electrical signal, and the sine pulse width modulation wave can be used for modulating the electrical signal frequency of the alternating current.

[0075] The frequency of the sine pulse width modulation wave can be the same as the frequency of the working electrical signal of the target power grid, and the frequency of the sine pulse width modulation wave can also be within a preset frequency range with the frequency of the working electrical signal of the target power grid.

[0076] The fundamental wave signal can be used to generate a reference signal for modulating the sine wave signal corresponding to the alternating current. The harmonic signals can be frequency signals suppressed during the modulation process of the sine wave signal corresponding to the alternating current.

[0077] After determining the harmonic signal and fundamental wave signal corresponding to the working electrical signal of the target power grid, the fundamental wave signal can be phase-locked according to the frequency, phase, amplitude, etc. of the fundamental wave signal to obtain a corresponding sine pulse width modulation wave synchronized with the power grid.

[0078] It should be noted that the phase-locking of the fundamental wave signal can be integral phase-locking based on a second-order generalized integral adaptive filter. The fundamental wave signal corresponding to the square wave signal is tracked and phase-shifted by the second-order generalized adaptive filter to achieve positive and negative sequence separation and filtering of the fundamental wave signal, and a corresponding sine pulse width modulation wave is obtained.

[0079] In some embodiments, after determining the reference signal, the harmonics in the reference signal can also be suppressed according to the harmonic signal corresponding to the above square wave signal, so as to obtain a sine pulse width modulation wave with suppressed harmonic signals.

[0080] Step 105: Based on the sine pulse width modulation wave, control the flyback micro-inverter to the target power grid or electrical equipment, and output a target electrical signal synchronized with the sine pulse width modulation wave.

[0081] Wherein, the target electrical signal is a signal with the same frequency as the working electrical signal of the target power grid or a frequency within the same frequency standard range. The sine pulse width modulation wave is used to control the switch of the flyback micro-inverter, and the flyback micro-inverter is used to convert the electrical energy of the flyback micro-inverter.

[0082] After determining the sine pulse width modulation wave, the sine pulse width modulation wave can be compared with the sine wave signal corresponding to the alternating current to determine the phase difference between the sine pulse width modulation wave and the sine wave signal corresponding to the alternating current. After determining the phase difference between the sine pulse width modulation wave and the sine wave signal corresponding to the alternating current, the control pulse width for synchronizing the frequency of the alternating current with the target power grid can be calculated based on the phase difference. After determining the control pulse width, based on the pulse width modulation technology, the sine wave signal of the alternating current can be converted into a series of pulse signals according to the calculated control pulse width to obtain a corresponding target electrical signal.

[0083] After determining the target electrical signal, the alternating current can be sent to the target power grid or electrical equipment according to the signal frequency of the target electrical signal.

[0084] It should be noted that after determining the target electrical signal, based on the electrical components of the target electrical signal of the alternating current, it can be transmitted to the target power grid, and the access of electrical signals with different frequency standards can be realized. After determining the target electrical signal, the electrical components of the modulated target electrical signal can also be transmitted to the electrical equipment based on the frequency, phase, and amplitude of the target electrical signal.

[0085] In a specific embodiment, based on the sine pulse width modulation wave, the step of controlling the flyback micro-inverter to the target power grid or electrical equipment and outputting a target electrical signal synchronized with the sine pulse width modulation wave may include controlling the micro-inverter switch based on the sine pulse width modulation wave, so that the flyback micro-inverter outputs a target electrical signal synchronized with the sine pulse width modulation wave to the target power grid or electrical equipment.

[0086] Among them, for the target power grid, in the case where it is widely used in the area where electricity is consumed and the power supplies in different electricity-consuming areas have different frequency standards, there will be a problem that the generated alternating current cannot be connected to the target power grid with different frequency standards. Based on the sine pulse width modulation wave, this application connects the modulated alternating current to the target power grid, solving the problem that the frequency between the alternating current generated by photovoltaic conversion through the flyback micro-inverter and the target power grid is in different frequency standards and cannot be connected.

[0087] In addition, for the electrical equipment, based on different application scenarios, and in different application scenarios, the current frequency that the electrical equipment can use is in a different frequency standard from the frequency of the alternating current output by the flyback micro-inverter for photovoltaic power generation, resulting in the inability to connect between the electrical equipment and the alternating current, thereby reducing the adaptability of the electrical equipment. Based on the sine pulse width modulation wave, this application connects the modulated alternating current to the electrical equipment, solving the problem that the frequency between the alternating current generated by photovoltaic conversion through the flyback micro-inverter and the electrical equipment is in different frequency standards and cannot be connected, so that the electrical equipment cannot be used.

[0088] In Figure 1In the described method embodiments, the working electrical signal of the target power grid can be obtained; according to the working electrical signal, a square wave signal with the same frequency as the working electrical signal frequency can be obtained; the square wave signal is subjected to Fourier decomposition to obtain a fundamental wave signal and harmonic signals, where the fundamental wave signal is a sine wave signal with the same frequency as the square wave signal, and the frequency of the harmonic signals is an integer multiple of the frequency of the fundamental wave signal; the fundamental wave signal is phase-locked to obtain a sine wave with the same frequency as the working electrical signal; modulation is performed based on the sine wave to obtain a sine pulse width modulation wave; based on the sine pulse width modulation wave, the flyback micro-inverter is controlled to output a target electrical signal with the same frequency as the sine pulse width modulation wave to the target power grid or electrical equipment. It is possible to use the square wave signal corresponding to the working electrical signal as the basic tracking signal, and determine the corresponding fundamental wave signal and harmonic signals according to the square wave signal. After phase-locking the fundamental wave signal, the corresponding sine pulse width modulation wave is obtained. Based on this sine pulse width modulation wave, the frequency of the electrical signal output by the flyback micro-inverter to the target power grid is modulated to obtain the corresponding target electrical signal, so as to realize the frequency synchronization between the alternating current output by the flyback micro-inverter and the target power grid, improve the adaptability between the flyback micro-inverter with different frequency standards and the target power grid, and also improve the accuracy of modulating the grid-connected alternating current and the accuracy of frequency synchronization with the target power grid. Thus, the problem of how to synchronize the frequency between the alternating current output by the flyback micro-inverter and the target power grid when there is only the square wave signal for grid synchronization is effectively solved, so that the alternating current of the flyback micro-inverter can be connected to the target power grid based on the frequency synchronization between the alternating current and the target power grid.

[0089] It should be noted that the phase-locking method of the square wave signal proposed by the present invention can be Figure 1 the refined description of steps 103 and 104 of the synchronization method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition. Since the phase-locking method based on the square wave signal in the embodiments of the present application is the key to solving the corresponding technical problems of the present invention, the following is a refined description.

[0090] Please refer to Figure 2 , Figure 2 which is a schematic flow chart of a phase-locking method of a square wave signal disclosed in the embodiments of the present application. As Figure 2 shown, the phase-locking method of the square wave signal may include the following steps.

[0091] Step 201: Perform Fourier decomposition on the square wave signal to obtain a fundamental wave signal and harmonic signals.

[0092] Among them, the fundamental wave signal is a sine wave signal with the same frequency as the square wave signal, and the frequency of the harmonic signals is an integer multiple of the frequency of the fundamental wave signal.

[0093] Among them, the harmonic signals are multiple harmonic signals with higher corresponding frequencies determined based on the fundamental wave signal at different Fourier series.

[0094] Step 202: Perform phase locking on the fundamental wave signal to obtain a sine wave with the same frequency as the working electrical signal;

[0095] Step 203: Modulate the sine wave to obtain a sine pulse width modulation wave.

[0096] After determining the harmonic signal and fundamental wave signal corresponding to the square wave signal, a phase-locking method based on the second-order generalized integrator SOGI-PLL can be used to construct an adaptive filter based on the second-order generalized integrator on the digital controller in the flyback micro-inverter to achieve 90-degree phase angle shift and harmonic filtering, and obtain a sine pulse width modulation wave synchronized with the working electrical signal.

[0097] Please refer to Figure 3 , Figure 3 , which is a schematic diagram of the system architecture of a flyback micro-inverter implementing a phase-locking method disclosed in an embodiment of the present application. Specifically, the system architecture where the flyback micro-inverter is located includes a target power grid, a flyback micro-inverter, the drive of the flyback micro-inverter, and a power supply. The phase-locking method of the square wave signal can be applied to the flyback micro-inverter, which includes a processor and a memory. Among them, the processor is one of the core components of the controller, responsible for the overall control and coordination functions; the memory includes a program memory and a data memory, which are used to store the corresponding method programs and signal data respectively. The drive of the flyback micro-inverter can start the flyback micro-inverter as the host computer of the flyback micro-inverter. The power supply can be electrically connected to the flyback micro-inverter as an energy storage device. The target power grid is the power grid to be connected, and the flyback micro-inverter can obtain the electrical signal of the target power grid.

[0098] As a specific implementation manner, the controller of the flyback micro-inverter can obtain the working electrical signal of the target power grid, and the controller of the flyback micro-inverter can also determine the signal frequency of the electrical signal output by the flyback micro-inverter. When it is determined that the signal frequency of the working electrical signal of the target power grid is inconsistent with the signal frequency of the electrical signal output by the flyback micro-inverter, the phase-locking method of the square wave signal disclosed in the present application is executed to synchronize the frequency and phase of the electrical signal output by the flyback micro-inverter with the working electrical signal of the target power grid.

[0099] Specifically, after the controller of the flyback micro-inverter obtains the working electrical signal of the target power grid, the controller can perform phase locking on the working electrical signal through the phase-locking method based on the square wave signal to obtain a sine pulse width modulation wave with the same initial phase and frequency as the working electrical signal. After determining the sine pulse width modulation wave, the sine pulse width modulation wave is output to the flyback micro-inverter to modulate the electrical signal output by the flyback micro-inverter, thereby achieving frequency synchronization between the two electrical signals.

[0100] As an implementation manner, as shown in Figure 3As shown, the controller obtains the working electrical signal of the target power grid. Specifically, the controller is an inverter controller for controlling a flyback inverter. The controller includes a microprocessor, which is one of the core components of the controller and is responsible for the overall control and coordination functions. The microprocessor can implement the control algorithms and logics of the flyback inverter, including power regulation, frequency control, voltage adjustment, etc., to ensure that the output electrical energy of the flyback inverter meets the requirements of the power grid. The microprocessor also provides a communication interface with an external system, such as a monitoring system. The communication interface is, for example, a power grid interface. Through the communication interface, the microprocessor can exchange data with external devices, receive instructions, and report the operating status of the flyback inverter through the monitoring system. And the microprocessor can process data from various sensors (such as current sensors, voltage sensors) and input devices (such as buttons, switches), and make corresponding decisions according to the monitored situations. For example, in the case where the frequency of the working electrical signal of the target power grid is different from the frequency of the electrical signal of the power supply, the frequency synchronization of the electrical signal of the power supply and the power grid is achieved.

[0101] Furthermore, after the controller obtains the working electrical signal of the target power grid, through phase-locked technology, the working electrical signal is phase-locked to obtain a first sine modulation wave signal that is consistent with the initial phase and frequency of the working electrical signal. At the same time, the controller can obtain the preset power factor of the power supply to be connected to the grid.

[0102] Specifically, the controller can obtain the time difference corresponding to the phase angle difference according to the phase angle difference. Then the controller generates a sine correction modulation wave signal according to the time difference and the first sine modulation wave signal, where the half-cycle duration of the sine correction modulation wave signal is equal to the difference between the half-cycle duration of the first sine modulation wave signal and the time difference. Thus, the period and frequency of the sine correction modulation wave signal can be known, and then the sine correction modulation wave signal is generated. Finally, based on the sine correction modulation wave signal, the controller controls the flyback inverter to output a target alternating current corresponding to the sine correction modulation wave signal to the target power grid or electrical equipment.

[0103] It should be noted that the flyback inverter in this application refers to an inverter that adopts flyback switching power supply technology. A flyback switching power supply is a switching power supply that uses a flyback high-frequency transformer to isolate the input and output circuits. "Flyback" specifically means that when the switching tube is turned on, the output transformer acts as an inductor, and electrical energy is converted into magnetic energy, and there is no current in the output circuit at this time; on the contrary, when the switching tube is turned off, the output transformer releases energy, and magnetic energy is converted into electrical energy, and there is current in the output circuit. Preferably, the inverter in the embodiment is a micro-inverter, and the micro-inverter can achieve maximum power point tracking (MPPT) at the component level and has advantages over centralized inverters. In this way, the overall output power can be maximized by optimizing the output power of each module.

[0104] InFigure 2 In the described method embodiments, a square wave signal synchronized with the working electrical signal can be obtained according to the working electrical signal; the square wave signal is subjected to Fourier decomposition to obtain a fundamental wave signal and harmonic signals, where the fundamental wave signal is a sine wave signal with the same frequency as the square wave signal, and the frequency of the harmonic signals is an integer multiple of the frequency of the fundamental wave signal; the fundamental wave signal is phase-locked to obtain a sine pulse width modulation wave with the same frequency as the working electrical signal. By converting the working signal of the target power grid detected by the flyback micro-inverter into a synchronized square wave signal, signal decomposition is performed on the basis of the square wave signal to obtain the corresponding fundamental wave signal and harmonic signals. Phase-locking is performed on the fundamental wave signal on the basis of the harmonic signals to generate a modulation signal according to the working electrical signal of the target power grid, that is, a sine pulse width modulation wave. After determining the sine pulse width modulation wave, the corresponding power supply can be controlled based on the sine pulse width modulation wave to output the corresponding modulated target electrical signal to the target power grid. The target electrical signal can be used to achieve the frequency and phase synchronization between the power supply and the target power grid, and the power supply accesses the corresponding target power grid based on the synchronized information. In this way, a square wave signal corresponding to the working electrical signal can be used as the basic tracking signal, and the corresponding fundamental wave signal and harmonic signals can be determined according to the square wave signal. After phase-locking the fundamental wave signal, the corresponding sine pulse width modulation wave is obtained, and sine pulse width modulation is performed based on the sine pulse width modulation wave to obtain the corresponding target electrical signal, so as to achieve the synchronization between the alternating current and the power grid, improve the adaptability between the alternating current with different frequency standards and the target power grid, and also improve the accuracy of modulating the alternating current and the accuracy of frequency synchronization with the target power grid. Thus, the problem of how to synchronize the frequency between the flyback micro-inverter alternating current and the target power grid is effectively solved, and the flyback micro-inverter alternating current can be connected to the target power grid based on the frequency synchronization between the alternating current and the target power grid. In addition, in the present application, the fundamental wave signal is obtained by performing Fourier decomposition on the square wave signal and phase-locking the fundamental wave signal, so that the problem that the prior art can only phase-lock sine wave signals and cannot phase-lock square wave signals can be solved, and the accuracy of phase locking is improved.

[0105] An embodiment of the present application also discloses a controller of a flyback micro-inverter. The controller of the flyback micro-inverter stores a computer program, including a processor and a memory. The memory stores a computer program or computer instructions. When the processor calls the computer program or the computer instructions to run, the computer program is executed by the processor to implement the synchronization method for flyback micro-inverter grid connection by square wave harmonic decomposition or the phase-locking method for square wave signals in any of the above technical solutions.

[0106] It should be understood that the same or corresponding information in the above different embodiments can be referred to each other.

[0107] It should be understood that the above are only partial or preferred embodiments of the present invention, and neither the text nor the drawings can limit the scope of protection of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the overall concept of the present invention, or any direct / indirect application in other related technical fields, is included in the scope of protection of the present invention.

Claims

1. A synchronous method for realizing flyback micro-inverter grid connection by square-wave harmonic decomposition, characterized in that, Including: Obtain the working electrical signal synchronized with the target power grid; According to the working electrical signal, obtain a square wave signal with a frequency consistent with that of the working electrical signal; Perform Fourier decomposition on the square wave signal to obtain a fundamental wave signal and harmonic signals, where the fundamental wave signal is a sine wave signal synchronized with the frequency and phase of the square wave signal, and the frequency of the harmonic signals is an integer multiple of the frequency of the fundamental wave signal; Perform integral phase-locking on the fundamental wave signal based on an adaptive filter of second-order generalized integral to obtain a sine wave synchronized with the working electrical signal; Modulate the sine wave to obtain a sine pulse width modulation wave, including tracking and phase-shifting the fundamental wave signal corresponding to the square wave signal based on an adaptive filter of second-order generalized integral to achieve positive and negative sequence separation and filtering of the fundamental wave signal, and obtain the corresponding sine pulse width modulation wave; Based on the sine pulse width modulation wave, control the flyback micro-inverter to the target power grid or electrical equipment to output a target electrical signal with the same frequency and phase as the sine pulse width modulation wave, including: comparing the sine pulse width modulation wave with the sine wave signal corresponding to the alternating current to determine the phase difference between the sine pulse width modulation wave and the sine wave signal corresponding to the alternating current; calculating the control pulse width for controlling the frequency synchronization of the alternating current with the target power grid according to the phase difference, and converting the sine wave signal corresponding to the alternating current into a series of pulse signals based on the control pulse width to obtain the corresponding target electrical signal.

2. The synchronous method for realizing the anti - flyback micro - inverter grid connection by square - wave harmonic decomposition according to claim 1, characterized in that, The working electrical signal is a sine wave signal.

3. The synchronous method for realizing flyback micro-inverter grid connection by square-wave harmonic decomposition according to claim 2, characterized in that The obtaining a square wave signal with a frequency consistent with that of the working electrical signal according to the working electrical signal includes: Obtain the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal; According to the characteristic point detection information, obtain a square wave signal with a frequency consistent with that of the working electrical signal.

4. The synchronous method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition according to claim 3, characterized in that, The characteristic point detection information is the zero-crossing information of the working electrical signal; The obtaining the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal includes: According to the detection feedback information of the working electrical signal by a comparator, obtain the zero-crossing information of the working electrical signal.

5. The synchronous method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition according to claim 3, characterized in that, The obtaining the detection feedback information of the working electrical signal to obtain the characteristic point detection information of the working electrical signal includes: According to the detection feedback information of the working electrical signal within a preset time period, obtain the characteristic point detection information of the working electrical signal.

6. The synchronous method for realizing the grid connection of flyback micro-inverter by square wave harmonic decomposition according to claim 5, characterized in that, The working electrical signal is a waveform signal with a preset period, the preset period is composed of a first half period and a second half period, and the preset time period is the time period corresponding to the first half period or the time period corresponding to the second half period or the time period corresponding to the preset period.

7. The synchronous method for realizing flyback micro-inverter grid connection by square wave harmonic decomposition according to any one of claims 1 to 6, characterized in that The controlling the flyback micro-inverter to the target power grid or electrical equipment based on the sine pulse width modulation wave to output a target electrical signal with the same frequency and phase as the sine pulse width modulation wave includes: Based on the control of the micro-inverter switch by the sine pulse width modulation wave, enable the flyback micro-inverter to the target power grid or electrical equipment to output a target electrical signal with the same frequency and phase as the sine pulse width modulation wave.

8. A controller for a flyback micro-inverter, characterized in that The controller of the flyback micro-inverter includes a processor and a memory. The memory stores computer programs or computer instructions. When the processor calls and runs the computer programs or the computer instructions, the steps of the synchronous method for realizing grid connection of the flyback micro-inverter by square-wave harmonic decomposition as described in any one of claims 1 to 7 are implemented.

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