Single-phase Inverter Parallel Synchronization Method and System, Single-phase Inverter, and Storage Medium

Abstract

The present invention provides a parallel synchronization method and system for single-phase inverters, a single-phase inverter, and a storage medium. The method includes: determining whether the mains power is normal; if the mains power is normal, correcting a first quasi-tracking phase angle based on the high and low level signals corresponding to the mains power, and performing phase synchronization on the current phase angle of the single-phase inverter according to the corrected first quasi-tracking phase angle; if the mains power is abnormal and the single-phase inverter is the host or has preempted the host position, generating a synchronization signal according to the phase of the single-phase inverter, and sending the synchronization signal to each slave; if the mains power is abnormal and the single-phase inverter is a slave, correcting a second quasi-tracking phase angle according to the synchronization signal, and performing phase synchronization on the current phase angle of the single-phase inverter according to the corrected second quasi-tracking phase angle. Based on the present invention, parallel synchronization of all parallel-connected single-phase inverters can be achieved, and the reliability and stability of the operation of the single-phase inverter parallel synchronization system can also be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of parallel application of inverters, and particularly to a single-phase inverter parallel synchronization method and system, a single-phase inverter, and a storage medium. Background Art

[0002] With the rapid development of inverter technology, the requirements for the capacity, performance, and reliability of power supply systems are getting higher and higher. Moreover, due to the increasing power requirements of power supply systems, more and more products are starting to add a parallel function to meet the needs of modular design for high power and redundancy.

[0003] In the prior art, to achieve parallel operation between inverters, it is necessary to ensure the consistency of the amplitude, frequency, and phase of the output voltages of each inverter. Currently, the phase tracking of the inverter output voltage is usually based on a Second-Order Generalized Integrator (SOGI) and coordinate transformation operations. However, since the SOGI operation cannot completely filter out the harmonic content contained in the mains power itself / interference from the sampling circuit, the phase-locked angle calculated by the phase tracking is deviated.

[0004] However, the deviation of the phase-locked angle will cause the phases of each inverter to be asynchronous, which will further increase the circulating current of the inverter and even damage the machine. Therefore, the phase tracking link in the inverter parallel system is very crucial for the reliable and stable operation of the inverter parallel system. Summary of the Invention

[0005] Embodiments of the present invention provide a single-phase inverter parallel synchronization method and system, a single-phase inverter, and a storage medium to solve the problem that the harmonic content contained in the mains power itself / interference from the sampling circuit in the prior art affects the calculation accuracy of the phase-locked angle, resulting in asynchronous phases when each inverter is paralleled.

[0006] In a first aspect, embodiments of the present invention provide a single-phase inverter parallel synchronization method, which is applied to each single-phase inverter in a single-phase inverter parallel synchronization system including at least two single-phase inverters connected in parallel;

[0007] The single-phase inverter parallel synchronization method includes:

[0008] Determine whether the mains power is normal;

[0009] If the mains power is normal, correct the first quasi-tracking phase angle according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first quasi-tracking phase angle, and synchronize the current phase angle of the single-phase inverter according to the corrected value of the first quasi-tracking phase angle;

[0010] If the mains power is abnormal and the single-phase inverter is the master, or if the mains power is abnormal, the single-phase inverter is a slave, and the single-phase inverter seizes the master position in the single-phase inverter parallel synchronization system, a synchronization signal is generated according to the phase of the single-phase inverter, and the synchronization signal is sent to each slave in the single-phase inverter parallel synchronization system;

[0011] If the mains power is abnormal, the single-phase inverter is a slave, and after receiving the synchronization signal sent by the master in the single-phase inverter parallel synchronization system, the second quasi-tracking phase angle is corrected according to the synchronization signal to obtain a corrected value of the second quasi-tracking phase angle, and the current phase angle of the single-phase inverter is phase-synchronized according to the corrected value of the second quasi-tracking phase angle.

[0012] In a second aspect, an embodiment of the present invention provides a single-phase inverter, including: a control unit, a zero-crossing detection unit, and an output isolation unit;

[0013] The control unit includes: a memory, a processor, and a computer program. The memory is used to store the computer program, and the processor is used to call and run the computer program to execute the steps of the method described in the first aspect or any possible implementation manner of the first aspect above;

[0014] The input end of the zero-crossing detection unit is used to be connected to the mains power. The output end of the zero-crossing detection unit is connected to the input end of the control unit. The output end of the control unit is connected to the input end of the output isolation unit. The output end of the output isolation unit is connected to the CAP port of the control unit.

[0015] In a third aspect, an embodiment of the present invention provides a single-phase inverter parallel synchronization system, including: at least two single-phase inverters described in the second aspect above;

[0016] Wherein, the output end of the output isolation unit in each single-phase inverter is connected to the CAP port of the control unit in other single-phase inverters.

[0017] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in the first aspect or any possible implementation manner of the first aspect above are implemented.

[0018] An embodiment of the present invention provides a method and system for parallel synchronization of single-phase inverters, a single-phase inverter, and a storage medium. The method for parallel synchronization of single-phase inverters is applied to each single-phase inverter in a single-phase inverter parallel synchronization system including at least two single-phase inverters connected in parallel; the method includes: determining whether the mains power is normal; if the mains power is normal, correcting a first phase angle to be tracked according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first phase angle to be tracked, and performing phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the first phase angle to be tracked; if the mains power is abnormal and the single-phase inverter is the master, or if the mains power is abnormal and the single-phase inverter is a slave and the single-phase inverter preempts the master position in the single-phase inverter parallel synchronization system, generating a synchronization signal according to the phase of the single-phase inverter, and sending the synchronization signal to each slave in the single-phase inverter parallel synchronization system; if the mains power is abnormal and the single-phase inverter is a slave and after receiving the synchronization signal sent by the master in the single-phase inverter parallel synchronization system, correcting a second phase angle to be tracked according to the synchronization signal to obtain a corrected value of the second phase angle to be tracked, and performing phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the second phase angle to be tracked. In the embodiment of the present invention, the phase of the mains voltage or the phase of the standard phase angle corresponding to the single-phase inverter as the master is used as the target phase for each single-phase inverter to follow. Each single-phase inverter adjusts its own phase based on the standard phase angle until the phases of all single-phase inverters meet the preset conditions after parallel connection, and the parallel synchronization of all single-phase inverters is realized; moreover, since the parallel synchronization of each single-phase inverter is not achieved through the mains power itself / sampling circuit, the problem that the harmonic content caused by the interference of the mains power itself / sampling circuit may lead to the deviation of the phase-locked angle is effectively avoided, and further the reliable operation of the single-phase inverter parallel synchronization system is improved. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only 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.

[0020] Figure 1 is the implementation flowchart of the method for parallel synchronization of single-phase inverters provided by the embodiment of the present invention;

[0021] Figure 2 is the parallel synchronization flowchart of the method for parallel synchronization of single-phase inverters provided by the embodiment of the present invention;

[0022] Figure 3It is the phase following flowchart of the single-phase inverter parallel synchronization method provided by the embodiments of the present invention;

[0023] Figure 4 It is the structural schematic diagram of the single-phase inverter provided by the embodiments of the present invention;

[0024] Figure 5 It is the structural schematic diagram of the single-phase inverter parallel synchronization system provided by the embodiments of the present invention;

[0025] Figure 6 It is the structural schematic diagram of the single-phase inverter parallel synchronization device provided by the embodiments of the present invention;

[0026] Figure 7 It is the structural schematic diagram of the control unit provided by the embodiments of the present invention. Specific embodiments

[0027] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0028] To make the purpose, technical solutions, and advantages of the present invention clearer, the following will be described through specific embodiments with reference to the accompanying drawings.

[0029] In the prior art, the single-phase AC phase-locked technology is usually as follows:

[0030] (1) After the AC signal passes through the SOGI operation, the in-phase signal α and the quadrature signal β are obtained.

[0031] (2) The formula for the in-phase signal transfer function in the SOGI operation is: Among them, H d (s) represents the transfer function of the in-phase signal; k represents the closed-loop coefficient, and k usually takes the value of 1.414 in engineering; ω n represents the resonant frequency of the SOGI, ω n = 2πf; s represents the unique parameter in the transfer function obtained from the Laplace transform; the formula for the quadrature signal transfer function is: Among them, H q (s) represents the transfer function of the quadrature signal.

[0032] (3) Define the obtained in-phase signal α and quadrature signal β as: Among them, a represents the effective value of the mains voltage, and θ represents the mains phase angle.

[0033] (4) Define the phase angle obtained after single-phase phase locking as θ', and perform the dq coordinate transformation on it as follows: Where, θ' represents the phase angle of the mains electricity after single-phase phase locking; u d 、u q respectively represent the mains electricity voltages in the d-axis and q-axis two projection directions obtained by the dq coordinate transformation.

[0034] It can be calculated as follows: From this, it can be known that when the phase locking is successful, θ - θ' = 0, u q = 0, and use to perform closed-loop control on the q-axis, and accumulate and calculate the phase angle value within one mains electricity cycle to obtain the phase-locked angle θ; where, T represents the interruption period of the control unit in the single-line inverter.

[0035] However, the disadvantages of the single-phase AC phase-locking technology in the existing technology are as follows: 1) The phase tracking must go through the SOGI and coordinate transformation operations, and the calculation amount is relatively large, and the requirements for the main frequency and sampling accuracy of the control unit MCU are relatively high; 2) The SOGI operation cannot completely filter out the harmonic content contained in the mains electricity itself / sampling interference, which will cause a deviation in the phase-locked angle obtained by the phase tracking calculation. Based on this, the embodiment of the present invention provides a single-phase inverter parallel synchronization method, Figure 1 This is the implementation flowchart of the single-phase inverter parallel synchronization method provided by the embodiment of the present invention, as Figure 1 shown; this single-phase inverter parallel synchronization method is applied to each single-phase inverter in a single-phase inverter parallel synchronization system including at least two single-phase inverters connected in parallel.

[0036] This single-phase inverter parallel synchronization method includes:

[0037] Step 101: Determine whether the mains electricity is normal.

[0038] In step 101, determining whether the mains electricity is normal can be: the control unit in the single-phase inverter uses the zero-crossing detection unit in the single-phase inverter to calculate the effective value and frequency value of the mains electricity voltage; then compare the obtained effective value of the mains electricity voltage and the mains electricity voltage frequency value with a preset range, and determine whether the effective value of the mains electricity voltage and the mains electricity voltage frequency value are normal according to the comparison result, and further determine whether the mains electricity is normal. In this embodiment, by determining whether the mains electricity is normal, it is beneficial for the single-phase inverter to further perform corresponding operations based on normal mains electricity or abnormal mains electricity to achieve the parallel synchronization of all single-phase inverters connected in parallel.

[0039] Step 102: If the mains electricity is normal, correct the first quasi-tracking phase angle according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain the first quasi-tracking phase angle correction value, and perform phase synchronization on the current phase angle of the single-phase inverter according to the first quasi-tracking phase angle correction value.

[0040] In step 102, Figure 2 is the parallel synchronization flowchart of the parallel synchronization method for single-phase inverters provided by the embodiments of the present invention, Figure 3 is the phase following flowchart of the parallel synchronization method for single-phase inverters provided by the embodiments of the present invention ( Figure 3 where θ(t) can represent the first phase angle to be tracked of the mains voltage or the second phase angle to be tracked of the host; θ'(t) can represent the current phase angle of the single-phase inverter; Δ can represent a preset threshold; θ”(t) can represent the current phase angle adjustment value of the single-phase inverter; and Δθ can represent a preset step size.). Figure 4 is the structural schematic diagram of the single-phase inverter provided by the embodiments of the present invention. Please refer to Figures 1 to 4 simultaneously. In Figure 4 , the input end of the zero-crossing detection unit in the single-phase inverter is connected to the mains, and the output end of the zero-crossing detection unit is connected to the input end of the control unit. Therefore, when the mains is normal, the zero-crossing detection unit in the single-phase inverter generates a high-low level signal corresponding to the mains based on the normal mains and outputs it to the control unit. The control unit corrects the first phase angle to be tracked based on the high-low level signal to obtain a corrected value of the first phase angle to be tracked; then, based on the corrected value of the first phase angle to be tracked, the current phase angle of the single-phase inverter is phase-synchronized to ensure that each single-phase inverter in the single-phase inverter parallel synchronization system can be phase-synchronized with the normal mains when the mains is normal, thereby realizing the parallel synchronization of all single-phase inverters and ensuring the reliable operation of the single-phase inverter parallel synchronization system.

[0041] In a possible implementation manner, correcting the first phase angle to be tracked according to the high-low level signal output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first phase angle to be tracked includes:

[0042] Obtaining the first phase angle to be tracked of the mains voltage at time i based on the interruption period of the control unit in the single-phase inverter; where i is a positive integer.

[0043] Determining whether the high-low level signal received by the single-phase inverter at time i is at the rising edge / falling edge.

[0044] If the high-low level signal received by the single-phase inverter at time i is at the rising edge / falling edge, correcting the first phase angle to be tracked at time i based on a first preset value to obtain a corrected value of the first phase angle to be tracked at time i.

[0045] In this embodiment, please refer to Figures 1 to 4, based on the interruption period of the control unit in the single-phase inverter, integrate cycle by cycle to construct the first pseudo-tracking phase angle of the mains voltage at time i; where i is a positive integer. The control unit can be a single-chip microcontroller control chip, a DSP control chip, etc., and this application does not limit this. Exemplarily, the calculation method of the first pseudo-tracking phase angle of the mains voltage at time i can be: where, θ(t i ) is the first pseudo-tracking phase angle of the mains voltage at time i, θ(t i-1 ) is the first pseudo-tracking phase angle of the mains voltage at time i - 1, T is the interruption period of the control unit in the single-phase inverter, and ω is the power frequency angular velocity of the single-phase inverter. Then, determine whether the high and low level signals received by the single-phase inverter at time i are at the rising edge / falling edge; Exemplarily, the determination method of the rising edge / falling edge can be: when the low level of the high and low level signal changes to high level, it is determined as the rising edge; when the high level of the high and low level signal changes to low level, it is determined as the falling edge. If the high and low level signals received by the single-phase inverter at time i are at the rising edge, Exemplarily, the first preset value can be that is, correct the first pseudo-tracking phase angle at time i to to obtain the corrected value of the first pseudo-tracking phase angle at time i; and if the high and low level signals received by the single-phase inverter at time i are at the falling edge, Exemplarily, the first preset value can be that is, correct the first pseudo-tracking phase angle at time i to to obtain the corrected value of the first pseudo-tracking phase angle at time i. In this embodiment, after obtaining the first pseudo-tracking phase angle of the mains voltage at time i, it is also possible to determine whether the frequency of the high and low level signals corresponding to the mains voltage at the current time is normal. When the mains voltage frequency is normal, further determine whether the high and low level signals are at the rising edge / falling edge to determine the normal mains voltage at the current time in real time, thereby effectively ensuring the accuracy of the corrected value of the first pseudo-tracking phase angle to be followed. In this embodiment, due to the possible deviation of the clock cycles of the control units in each single-phase inverter, there may be a phase shift when each single-phase inverter obtains the mains phase, and then the obtained mains phase has a deviation, resulting in out-of-phase synchronization when each single-phase inverter is paralleled. Based on this, in this embodiment, the phase of the mains obtained by the single-phase inverter is corrected cyclically, effectively ensuring the accuracy of the first pseudo-tracking phase angle (that is, effectively ensuring the accuracy of the obtained mains phase), and then facilitating each single-phase inverter to perform phase correction based on the corrected first pseudo-tracking phase angle to ensure reliable and stable parallel operation of each single-phase inverter.

[0046] In a possible implementation manner, after determining whether the high and low level signals received by the single-phase inverter at time i are at the rising edge / falling edge, it further includes:

[0047] If the high and low level signals received by the single-phase inverter at time i are not at the rising edge / falling edge, then let i = i + 1, and return to execute the step of "acquiring the first quasi-tracking phase angle of the mains voltage at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps.

[0048] In this embodiment, please refer to Figures 1 to 4 , when the high and low level signals received by the single-phase inverter at time i are not at the rising edge / falling edge, at this time, calculate the first quasi-tracking phase angle of the next moment of time i, that is, let i = i + 1, and jump to the step of "acquiring the first quasi-tracking phase angle of the mains voltage at time i based on the interruption period of the control unit in the single-phase inverter", and according to calculate the first quasi-tracking phase angle of the mains voltage at the current time i. In this embodiment, when the single-phase inverter detects that the high and low level signals are not at the rising edge or the falling edge, the first quasi-tracking phase angle of the current time i is continuously updated in a loop until the high and low level signals are at the rising edge or the falling edge, and then the first quasi-tracking phase angle is corrected. The purpose is to ensure that the phase of the mains voltage obtained by the single-phase inverter is exactly the same as the actual mains voltage phase, so as to ensure that each single-phase inverter can perform phase synchronization based on the accurately obtained mains voltage phase, and realize the parallel synchronization of all single-phase inverters in the single-phase inverter parallel synchronization system.

[0049] In a possible implementation manner, before correcting the first quasi-tracking phase angle of time i based on the first preset value to obtain the corrected value of the first quasi-tracking phase angle of time i, it further includes:

[0050] Judge whether the frequency corresponding to the high and low level signals satisfies the first preset frequency range.

[0051] If the frequency corresponding to the high and low level signals satisfies the first preset frequency range, then correct the first quasi-tracking phase angle of time i based on the first preset value to obtain the corrected value of the first quasi-tracking phase angle of time i.

[0052] If the frequency corresponding to the high and low level signals does not satisfy the first preset frequency range, then let i = i + 1, and return to execute the step of "acquiring the first quasi-tracking phase angle of the mains voltage at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps.

[0053] In this embodiment, please refer to Figures 1 to 4, before correcting the first quasi-tracking phase angle at time i, it is also possible to determine whether the working frequency of the mains power is normal at this time. After obtaining the first quasi-tracking phase angle several times in a loop, the mains power frequency may become abnormal. Therefore, at this time, the frequency corresponding to the high and low level signals can be judged based on the first preset frequency range to ensure that the phases synchronized by each single-phase inverter subsequently are the phases of the mains power with normal frequencies. Exemplarily, the first preset frequency range can be: 49.8Hz to 50.2Hz or 49.2Hz to 50.8Hz or other possible frequency fluctuation ranges when the mains power voltage is normal, etc., and the present application does not limit this. When the frequency corresponding to the high and low level signals satisfies the first preset frequency range, it proves that the mains power is normal at this time. Therefore, the first quasi-tracking phase angle at the current time (i.e., time i) is corrected based on the first preset value to obtain the corrected value of the first quasi-tracking phase angle at the current time. Exemplarily, the first preset value can be or The present application does not limit this. When the frequency corresponding to the high and low level signals does not satisfy the first preset frequency range, it proves that the mains power is abnormal at this time (possible abnormal situations can be: the mains power frequency fluctuates or the mains power loses power, etc.). At this time, let i = i + 1, and re-obtain the first quasi-tracking phase angle of the mains power voltage at time i based on the interruption period of the control unit in this single-phase inverter, and then re-judge whether the high and low level signals are at the rising edge / falling edge and whether to correct the first quasi-tracking phase angle. In this way, the accuracy of the mains power phases synchronized by each single-phase inverter when the mains power is normal is effectively guaranteed, and further, the parallel synchronous operation of each single-phase inverter is also effectively guaranteed.

[0054] In a possible implementation manner, while obtaining the first quasi-tracking phase angle of the mains power voltage at time i based on the interruption period of the control unit in this single-phase inverter, it further includes:

[0055] Based on the interruption period, obtain the current phase angle of this single-phase inverter at time i.

[0056] The phase synchronization of the current phase angle of this single-phase inverter according to the corrected value of the first quasi-tracking phase angle includes:

[0057] Based on the corrected value of the first quasi-tracking phase angle at time i and the interruption period, obtain the first quasi-tracking phase angle of the mains power voltage at time i + 1, and based on the current phase angle at time i and the interruption period, obtain the current phase angle of this single-phase inverter at time i + 1.

[0058] Calculate the absolute value of the first difference between the current phase angle at time i + 1 and the first quasi-tracking phase angle at time i + 1.

[0059] When the absolute value of the first difference is greater than a preset threshold, the current phase angle at time i + 1 is adjusted according to a preset step size to obtain the adjusted value of the current phase angle at time i + 1, so as to perform phase synchronization based on the adjusted value of the current phase angle at time i + 1.

[0060] In this embodiment, please refer to Figures 1 to 4 , while obtaining the first quasi-tracked phase angle of the mains voltage at time i each time, the single-phase inverter also obtains its own current phase angle at time i based on the interruption period of the internal control unit thereof. After the first quasi-tracked phase angle of the mains voltage at time i is corrected, the obtained corrected value of the first quasi-tracked phase angle can effectively ensure the accuracy of the phase angle to be followed by each single-phase inverter. At this time, based on the corrected first quasi-tracked phase angle at time i (i.e., the corrected value of the first quasi-tracked phase angle at time i) and the interruption period of the control unit of the single-phase inverter, the first quasi-tracked phase angle of the mains voltage at the next moment (i.e., time i + 1) is obtained, and the current phase angle of the single-phase inverter at the next moment (i.e., time i + 1) is obtained based on the updated current phase angle after time i and the interruption period. At this time, the absolute value of the first difference between the current phase angle at time i + 1 and the first quasi-tracked phase angle at time i + 1 is calculated. When the absolute value of the first difference is greater than a preset threshold, it proves that there is a phase difference that does not meet the conditions between the single-phase inverter and the mains voltage at this time. Then, the current phase angle at time i + 1 is adjusted according to a preset step size to obtain the adjusted value of the current phase angle at time i + 1, so as to continuously achieve synchronization with the mains phase based on the adjusted value of the current phase angle at time i + 1. In this embodiment, by judging whether the absolute value of the first difference between the phase of the single-phase inverter and the mains phase at the current moment is greater than a preset threshold, it is judged whether the single-phase inverter is synchronized with the phase of the normal mains voltage at this time. If not synchronized, the phase of the single-phase inverter is adjusted step by step based on a preset step size, and thus it can be effectively ensured that the single-phase inverter can be synchronously tracked with the phase of the normal mains voltage in real time.

[0061] In a possible implementation manner, adjusting the current phase angle at time i + 1 according to a preset step size to obtain the adjusted value of the current phase angle at time i + 1 includes:

[0062] Adjusting the current phase angle at time i + 1 according to θ”(t i+1 ) = θ'(t i+1 ) + flag × Δθ to obtain the adjusted value of the current phase angle at time i + 1.

[0063] Wherein, θ”(t i+1 ) represents the adjusted value of the current phase angle at time i + 1, and θ'(t i+1) represents the current phase angle at time i + 1, flag = 1 or flag = -1 represents the adjustment direction, and Δθ represents the preset step size.

[0064] In this embodiment, according to θ”(t i+1 ) = θ'(t i+1 ) + flag × Δθ, the current phase angle at time i + 1 is adjusted step by step to obtain the adjusted value of the current phase angle at time i + 1. Wherein, θ”(t i+1 ) represents the adjusted value of the current phase angle at time i + 1, θ'(t i+1 ) represents the current phase angle at time i + 1, flag = 1 or flag = -1 represents the adjustment direction, and Δθ represents the preset step size. Exemplarily, the preset step size can be: such appropriate phase step sizes, and the present application does not limit this. In this embodiment, by adjusting the phase of the single-phase inverter step by step, it can effectively ensure that the single-phase inverter can be synchronously tracked with the real-time phase of the normal mains voltage.

[0065] In a possible implementation manner, when the absolute value of the first difference is greater than the preset threshold and the current phase angle at time i + 1 is adjusted according to the preset step size to obtain the adjusted value of the current phase angle at time i + 1, the determination method of the value of the adjustment direction is:

[0066] Judge whether the current phase angle at time i + 1 is less than the first quasi-tracked phase angle at time i + 1.

[0067] When the current phase angle at time i + 1 is less than the first quasi-tracked phase angle at time i + 1, judge whether the absolute value of the first difference is greater than the first judgment condition.

[0068] If the absolute value of the first difference is greater than the first judgment condition, then flag = -1.

[0069] If the absolute value of the first difference is not greater than the first judgment condition, then flag = 1.

[0070] When the current phase angle at time i + 1 is not less than the first quasi-tracked phase angle at time i + 1, judge whether the absolute value of the first difference is greater than the second judgment condition.

[0071] If the absolute value of the first difference is greater than the second judgment condition, then flag = 1.

[0072] If the absolute value of the first difference is not greater than the second judgment condition, then flag = -1.

[0073] In this embodiment, when gradually adjusting the phase of the single-phase inverter to synchronize with the phase of the normal mains voltage, a left or right phase shift may affect the synchronization period for the single-phase inverter to successfully synchronize with the phase of the normal mains voltage. Therefore, it can be first determined whether a left or right phase shift can enable the single-phase inverter to synchronize with the phase of the normal mains voltage within the minimum number of step adjustments or the shortest synchronization period. In this way, the efficiency of the single-phase inverter in synchronizing the mains voltage phase is effectively guaranteed, which is also beneficial to the parallel synchronization operation of all single-phase inverters. Therefore, when the absolute value of the first difference is greater than a preset threshold and the current phase angle at time i + 1 is adjusted according to a preset step to obtain the adjusted value of the current phase angle at time i + 1, the method for determining the adjustment direction when the single-phase inverter gradually adjusts the phase can be as follows: First, determine whether the current phase angle at time i + 1 is less than the first phase angle to be tracked at time i + 1; when the current phase angle at time i + 1 is less than the first phase angle to be tracked at time i + 1, determine whether the absolute value of the first difference is greater than the first judgment condition. Exemplarily, let θ'(t i+1 ) represent the current phase angle at time i + 1, and let θ(t i+1 ) represent the first phase angle to be tracked at time i + 1. The absolute value of the first difference is: A' = |A| = |θ'(t i+1 ) - θ(t i+1 )|. The first judgment condition can be: B = |2π + A| = |2π + θ'(t i+1 ) - θ(t i+1 )|. If the absolute value of the first difference A' is greater than the first judgment condition B, then flag = -1. If the absolute value of the first difference A' is not greater than the first judgment condition B, then flag = 1. When the current phase angle at time i + 1 is not less than the first phase angle to be tracked at time i + 1, determine whether the absolute value of the first difference is greater than the second judgment condition. Exemplarily, the second judgment condition can be: C = |2π - A| = |2π - θ'(t i+1 ) + θ(t i+1 )|. If the absolute value of the first difference A' is greater than the second judgment condition C, then flag = 1; if the absolute value of the first difference A' is not greater than the second judgment condition C, then flag = -1.

[0074] Step 103: If the mains power is abnormal and the single-phase inverter is the host, or if the mains power is abnormal and the single-phase inverter is a slave and after the single-phase inverter seizes the host position in the single-phase inverter parallel synchronization system, generate a synchronization signal according to the phase of the single-phase inverter and send the synchronization signal to each slave in the single-phase inverter parallel synchronization system.

[0075] In step 103, please also refer to Figures 1 to 4, when the mains power is abnormal, if there is a master in the single-phase inverter parallel synchronization system, the phase of the master is used as the standard phase for synchronization; if there is a master in the single-phase inverter parallel synchronization system, one of the single-phase inverters in each single-phase inverter preempts the master position to become the master. After determining the master, the single-phase inverter acting as the master generates a synchronization signal based on its own phase information (exemplarily, the synchronization signal can be the high and low level signals corresponding to the master), and sends the synchronization signal to each slave in the single-phase inverter parallel synchronization system, so that each slave can achieve synchronization with the master phase after receiving the synchronization signal.

[0076] Step 104: If the mains power is abnormal, the single-phase inverter is a slave, and after receiving the synchronization signal sent by the master in the single-phase inverter parallel synchronization system, correct the second quasi-tracked phase angle according to the synchronization signal to obtain a corrected value of the second quasi-tracked phase angle, and perform phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the second quasi-tracked phase angle.

[0077] In step 104, please refer to Figures 1 to 4 , when the mains power is abnormal, after the single-phase inverter in the single-phase inverter parallel synchronization system receives the synchronization signal sent by the master, the control unit set inside it will correct the second quasi-tracked phase angle at an appropriate time according to the synchronization signal to obtain a corrected value of the second quasi-tracked phase angle, and then synchronize the current phase angle of the single-phase inverter based on the corrected value of the second quasi-tracked phase angle to ensure that each slave can be synchronized with the phase of the master, thereby ensuring the reliable operation of the single-phase inverter parallel synchronization system.

[0078] In a possible implementation, correcting the second quasi-tracked phase angle according to the synchronization signal to obtain a corrected value of the second quasi-tracked phase angle includes:

[0079] Based on the interruption period of the control unit in the single-phase inverter, obtain the second quasi-tracked phase angle of the master at time i; where i is a positive integer.

[0080] Judge whether the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge.

[0081] If the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge, correct the second quasi-tracked phase angle at time i based on the first preset value to obtain a corrected value of the second quasi-tracked phase angle at time i.

[0082] In this embodiment, please refer to Figures 1 to 4, based on the interruption period of the control unit in the single-phase inverter, integrate cycle by cycle to construct the second quasi-tracked phase angle of the host at time i; where i is a positive integer. In addition, the control unit of the single-phase inverter can be a single-chip microcomputer control chip, a DSP control chip, etc., and this application does not make any limitations in this regard. Exemplarily, the calculation method of the second quasi-tracked phase angle of the host at time i can be: where, θ 1 (t i ) is the second quasi-tracked phase angle of the host at time i, θ 1 (t i-1 ) is the second quasi-tracked phase angle of the host at time i - 1, T is the interruption period of the control unit in the single-phase inverter, and ω is the power frequency angular velocity of the single-phase inverter. Then, determine whether the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge; Exemplarily, the determination method of the rising edge / falling edge can be: when the synchronization signal changes from low level to high level, it is determined that the synchronization signal is at the rising edge; when the synchronization signal changes from high level to low level, it is determined that the synchronization signal is at the falling edge. If the synchronization signal received by the single-phase inverter at time i is at the rising edge, Exemplarily, the first preset value can be that is, correct the second quasi-tracked phase angle at time i to to obtain the corrected value of the second quasi-tracked phase angle at time i; and if the synchronization signal received by the single-phase inverter at time i is at the falling edge, Exemplarily, the first preset value can be that is, correct the second quasi-tracked phase angle at time i to to obtain the corrected value of the second quasi-tracked phase angle at time i. In this embodiment, after obtaining the first quasi-tracked phase angle of the mains voltage at time i, it is also possible to judge whether the frequency corresponding to the high and low level signals of the mains voltage at the current time is normal. When the mains voltage frequency is normal, further judge whether the high and low level signals are at the rising edge / falling edge to determine the normality of the mains voltage at the current time in real time, and thus effectively ensure the accuracy of the corrected value of the first quasi-tracked phase angle to be followed. In this embodiment, due to the possible deviation of the clock cycles of the control units in each single-phase inverter, there may be a phase shift when each single-phase inverter obtains the host phase, and further, the obtained host phase has a deviation, resulting in a decrease in the accuracy of phase synchronization when each single-phase inverter is paralleled and synchronized. Based on this, in this embodiment, by cyclically correcting the phase of the host obtained by the single-phase inverter, the real-time accuracy of the second quasi-tracked phase angle is effectively guaranteed (that is, the accuracy of the obtained host phase is effectively guaranteed), and thus it is beneficial for each single-phase inverter to perform phase correction based on the corrected second quasi-tracked phase angle to ensure the reliable and stable parallel and synchronous operation of each single-phase inverter.

[0083] In a possible implementation, after determining whether the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge, it further includes:

[0084] If the synchronization signal received by the single-phase inverter at time i is not at the rising edge / falling edge, then let i = i + 1, and return to execute the step of "obtaining the second quasi-tracked phase angle of the host at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps.

[0085] In this embodiment, please refer to Figures 1 to 4 When the synchronization signal received by the single-phase inverter at time i is not at the rising edge / falling edge, at this time, calculate the second quasi-tracked phase angle of the next moment of time i, that is, let i = i + 1, and jump to the step of "obtaining the second quasi-tracked phase angle of the host at time i based on the interruption period of the control unit in the single-phase inverter", and according to Calculate the second quasi-tracked phase angle of the host at the current time i. In this embodiment, when the single-phase inverter detects that the synchronization signal is not at the rising edge or the falling edge, it always continuously updates the second quasi-tracked phase angle of the current time i in a loop until the synchronization signal is at the rising edge or the falling edge, and then the second quasi-tracked phase angle will be corrected. The purpose is to ensure that the phase of the host obtained by the single-phase inverter is exactly the same as the actual phase of the host, so as to ensure that each slave single-phase inverter can perform phase synchronization based on the highly accurate host phase obtained, and realize the parallel synchronization of all single-phase inverters in the single-phase inverter parallel synchronization system.

[0086] In a possible implementation, before correcting the second quasi-tracked phase angle of time i based on the first preset value to obtain the corrected value of the second quasi-tracked phase angle of time i, it further includes:

[0087] Judge whether the frequency corresponding to the synchronization signal satisfies the second preset frequency range.

[0088] If the frequency corresponding to the synchronization signal satisfies the second preset frequency range, then correct the second quasi-tracked phase angle of time i based on the first preset value to obtain the corrected value of the first quasi-tracked phase angle of time i.

[0089] If the frequency corresponding to the synchronization signal does not satisfy the second preset frequency range, then let i = i + 1, and return to execute the step of "obtaining the second quasi-tracked phase angle of the host at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps.

[0090] In this embodiment, please refer to Figures 1 to 4, before correcting the second pseudo-tracking phase angle at time i, it is also possible to determine whether the operating frequency of the host is normal at this time. After obtaining the second pseudo-tracking phase angle several times in a loop, considering that the operating frequency of the host may be abnormal, at this time, the frequency corresponding to the synchronization signal can be judged based on the second preset frequency range to ensure that the phases synchronized by each subsequent single-phase inverter slave are the phases of the host with normal frequencies. Exemplarily, the second preset frequency range can be: 49.5 Hz to 50.5 Hz or 49.8 Hz to 50.2 Hz or other possible frequency fluctuation ranges when the host frequency is normal, etc., and this application does not limit this. When the frequency corresponding to the synchronization signal satisfies the second preset frequency range, it proves that the host is operating normally at this time. Therefore, the second pseudo-tracking phase angle at the current time (i.e., time i) is corrected based on the first preset value to obtain the corrected value of the second pseudo-tracking phase angle at the current time. Exemplarily, the first preset value can be or This application does not limit this. When the frequency corresponding to the synchronization signal does not satisfy the second preset frequency range, it proves that the host is operating abnormally at this time (possible abnormal situations can be: large fluctuations in the operating frequency of the host or power failure of the host, etc.). At this time, let i = i + 1, and re-obtain the second pseudo-tracking phase angle of the host at time i based on the interruption period of the control unit in this single-phase inverter, and then re-determine whether the synchronization signal is at the rising edge / falling edge and whether to correct the second pseudo-tracking phase angle. In this way, it effectively ensures the accuracy of the host phase synchronized by each single-phase inverter slave when the host is operating normally, and further effectively ensures the parallel synchronization operation of each single-phase inverter.

[0091] In a possible implementation manner, while obtaining the second pseudo-tracking phase angle of the host at time i based on the interruption period of the control unit in this single-phase inverter, it further includes:

[0092] Based on the interruption period, obtain the current phase angle of this single-phase inverter at time i.

[0093] Phase synchronization of the current phase angle of this single-phase inverter according to the corrected value of the second pseudo-tracking phase angle includes:

[0094] Based on the corrected value of the second pseudo-tracking phase angle at time i and the interruption period, obtain the second pseudo-tracking phase angle of the host at time i + 1, and based on the current phase angle at time i and the interruption period, obtain the current phase angle of this single-phase inverter at time i + 1.

[0095] Calculate the absolute value of the second difference between the current phase angle at time i + 1 and the second pseudo-tracking phase angle at time i + 1.

[0096] When the absolute value of the second difference is greater than a preset threshold, the current phase angle at time i + 1 is adjusted according to a preset step size to obtain the adjusted value of the current phase angle at time i + 1, so as to perform phase synchronization according to the adjusted value of the current phase angle at time i + 1.

[0097] In this embodiment, please refer to Figures 1 to 4 , while obtaining the second quasi-tracked phase angle of the host at time i each time, the single-phase inverter also obtains its own current phase angle at time i based on the interruption period of the control unit inside it. After correcting the second quasi-tracked phase angle of the host at time i, the obtained corrected value of the second quasi-tracked phase angle can effectively ensure the accuracy of the phase angle that each slave single-phase inverter needs to follow. At this time, based on the corrected second quasi-tracked phase angle at time i (that is, the corrected value of the second quasi-tracked phase angle at time i) and the interruption period of the control unit of the single-phase inverter, the second quasi-tracked phase angle of the host at the next moment (that is, time i + 1) is obtained, and the current phase angle of the single-phase inverter at the next moment (that is, time i + 1) is obtained based on the updated current phase angle after time i and the interruption period. At this time, calculate the absolute value of the second difference between the current phase angle at time i + 1 and the second quasi-tracked phase angle at time i + 1. When the absolute value of the second difference is greater than a preset threshold, it proves that there is a phase difference that does not meet the conditions between the single-phase inverter and the host at this time. Then, the current phase angle at time i + 1 is adjusted according to a preset step size to obtain the adjusted value of the current phase angle at time i + 1, so as to continuously achieve phase synchronization with the host based on the adjusted value of the current phase angle at time i + 1. In this embodiment, by judging whether the absolute value of the second difference between the phase of the single-phase inverter and the phase of the host at the current moment is greater than a preset threshold, it is judged whether the single-phase inverter is in phase synchronization with the host at this time. If not, the phase of the single-phase inverter is adjusted step by step based on a preset step size, and thus it can effectively ensure that the single-phase inverter can be in real-time phase synchronization with the host phase.

[0098] In a possible implementation manner, adjusting the current phase angle at time i + 1 according to a preset step size to obtain the adjusted value of the current phase angle at time i + 1 includes:

[0099] Adjust the current phase angle at time i + 1 according to θ”(t i+1 ) = θ'(t i+1 ) + flag × Δθ to obtain the adjusted value of the current phase angle at time i + 1.

[0100] Wherein, θ”(t i+1 ) represents the adjusted value of the current phase angle at time i + 1, θ'(t i+1 ) represents the current phase angle at time i + 1, flag = 1 or flag = -1 represents the adjustment direction, and Δθ represents the preset step size.

[0101] In this embodiment, according to θ”(t i+1 ) = θ'(t i+1 ) + flag × Δθ, the current phase angle at time i + 1 is gradually adjusted to obtain the adjusted value of the current phase angle at time i + 1. Wherein, θ”(t i+1 ) represents the adjusted value of the current phase angle at time i + 1, θ'(t i+1 ) represents the current phase angle at time i + 1, flag = 1 or flag = -1 represents the adjustment direction, and Δθ represents the preset step size. Exemplarily, the preset step size can be: Appropriate phase step sizes such as etc., and this application does not limit this. In this embodiment, by gradually adjusting the phase of the single-phase inverter, it can be effectively ensured that the single-phase inverter can be in real-time synchronization with the host phase.

[0102] In a possible implementation manner, when the absolute value of the second difference is greater than the preset threshold and the current phase angle at time i + 1 is adjusted according to the preset step size to obtain the adjusted value of the current phase angle at time i + 1, the determination method of the value of the adjustment direction is:

[0103] Judge whether the current phase angle at time i + 1 is less than the second quasi-tracked phase angle at time i + 1.

[0104] When the current phase angle at time i + 1 is less than the second quasi-tracked phase angle at time i + 1, judge whether the absolute value of the second difference is greater than the third judgment condition.

[0105] If the absolute value of the second difference is greater than the third judgment condition, then flag = -1.

[0106] If the absolute value of the second difference is not greater than the third judgment condition, then flag = 1.

[0107] When the current phase angle at time i + 1 is not less than the second quasi-tracked phase angle at time i + 1, judge whether the absolute value of the second difference is greater than the fourth judgment condition.

[0108] If the absolute value of the second difference is greater than the fourth judgment condition, then flag = 1.

[0109] If the absolute value of the second difference is not greater than the fourth judgment condition, then flag = -1.

[0110] In this embodiment, when gradually adjusting the phase of the single-phase inverter to synchronize with the phase of the host, the left or right phase shift may affect the synchronization period for the single-phase inverter to successfully synchronize with the host phase. Therefore, it can be first determined whether the left or right phase shift can enable the single-phase inverter to synchronize with the host phase within the minimum number of step adjustments or the shortest synchronization period. In this way, the efficiency of the single-phase inverter synchronizing with the host phase is effectively guaranteed, which is also beneficial to the parallel synchronization operation of all single-phase inverters. Therefore, when the absolute value of the second difference is greater than the preset threshold, and when adjusting the current phase angle at time i + 1 according to the preset step size to obtain the adjusted value of the current phase angle at time i + 1, the method for determining the adjustment direction when the single-phase inverter gradually adjusts the phase can be as follows: First, determine whether the current phase angle at time i + 1 is less than the second phase angle to be tracked at time i + 1; when the current phase angle at time i + 1 is less than the second phase angle to be tracked at time i + 1, determine whether the absolute value of the second difference is greater than the third judgment condition. Exemplarily, let θ'(t i+1 ) represent the current phase angle at time i + 1, and let θ 1 (t i+1 ) represent the second phase angle to be tracked at time i + 1. The absolute value of the second difference is: D' = |D| = |θ'(t i+1 ) - θ 1 (t i+1 )|. The third judgment condition can be: E = |2π + D| = |2π + θ'(t i+1 ) - θ 1 (t i+1 )|. If the absolute value of the second difference D' is greater than the third judgment condition E, then flag = -1. If the absolute value of the second difference D' is not greater than the third judgment condition E, then flag = 1. When the current phase angle at time i + 1 is not less than the second phase angle to be tracked at time i + 1, determine whether the absolute value of the second difference is greater than the fourth judgment condition. Exemplarily, the fourth judgment condition can be: E = |2π - D| = |2π - θ'(t i+1 ) + θ 1 (t i+1 )|. If the absolute value of the second difference D' is greater than the fourth judgment condition E, then flag = 1; if the absolute value of the first difference D' is not greater than the second judgment condition E, then flag = -1.

[0111] An embodiment of the present invention provides a method for parallel synchronization of single-phase inverters. The method for parallel synchronization of single-phase inverters is applied to each single-phase inverter in a single-phase inverter parallel synchronization system including at least two single-phase inverters connected in parallel. The method includes: determining whether the mains power is normal; if the mains power is normal, correcting a first quasi-tracking phase angle according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first quasi-tracking phase angle, and performing phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the first quasi-tracking phase angle; if the mains power is abnormal and the single-phase inverter is the host, or if the mains power is abnormal and the single-phase inverter is a slave and the single-phase inverter seizes the host position in the single-phase inverter parallel synchronization system, generating a synchronization signal according to the phase of the single-phase inverter, and sending the synchronization signal to each slave in the single-phase inverter parallel synchronization system; if the mains power is abnormal and the single-phase inverter is a slave and after receiving the synchronization signal sent by the host in the single-phase inverter parallel synchronization system, correcting a second quasi-tracking phase angle according to the synchronization signal to obtain a corrected value of the second quasi-tracking phase angle, and performing phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the second quasi-tracking phase angle. In the embodiment of the present invention, the phase of the mains voltage or the standard phase angle corresponding to the single-phase inverter serving as the host is used as the target phase for each single-phase inverter to follow. Each single-phase inverter adjusts its own phase based on the standard phase angle until the own phase of each single-phase inverter and the phase corresponding to the standard phase angle meet the preset conditions, and the parallel synchronization of all single-phase inverters connected in parallel is realized; moreover, since the parallel synchronization of each single-phase inverter is not achieved through the mains power itself / sampling circuit, the problem that the harmonic content caused by the interference of the mains power itself / sampling circuit may lead to a phase-locked angle deviation is effectively avoided, thereby further improving the reliable operation of the single-phase inverter parallel synchronization system.

[0112] The method for parallel synchronization of single-phase inverters provided by the embodiment of the present invention only uses the high and low levels obtained by zero-crossing detection / synchronization signal hardware as the trigger source for phase following, can effectively avoid the influence of sampling circuit interference and harmonics contained in the mains power itself, has a relatively small overall calculation amount, has a relatively low performance requirement for the control unit MCU, and is beneficial to reducing the hardware cost of the product.

[0113] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0114] On the other hand, an embodiment of the present invention provides a single-phase inverter parallel synchronization system. Figure 5 For the structural schematic diagram of the single-phase inverter parallel synchronization system provided by the embodiment of the present invention, as Figure 5 shown, the system includes: at least two single-phase inverters as described in the second aspect above.

[0115] Among them, the output end of the output isolation unit in each single-phase inverter is connected to the CAP port of the control unit in other single-phase inverters.

[0116] In this embodiment, as Figure 5 shown, taking the example that the single-phase inverter parallel synchronization system includes three single-phase inverters, the internal settings of each single-phase inverter are the same to ensure that when the mains power is abnormal and there is no host in the system, a certain single-phase inverter can preempt the host position to become the host, and then provide a standard phase with phase synchronization for each slave.

[0117] On the other hand, Figure 6 FIG. is a schematic structural diagram of the single-phase inverter parallel synchronization device provided by the embodiment of the present invention. As Figure 6 shown, the single-phase inverter parallel synchronization device is applied to each single-phase inverter in a single-phase inverter parallel synchronization system including at least two single-phase inverters connected in parallel.

[0118] The single-phase inverter parallel synchronization device 6 includes:

[0119] A mains power judgment module 601, configured to judge whether the mains power is normal.

[0120] A phase following mains power module 602, configured to, if the mains power is normal, correct the first quasi-tracking phase angle according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first quasi-tracking phase angle, and perform phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the first quasi-tracking phase angle.

[0121] A synchronization signal determination module 603, configured to, if the mains power is abnormal and the single-phase inverter is the host, or if the mains power is abnormal and the single-phase inverter is a slave and the single-phase inverter preempts the host position in the single-phase inverter parallel synchronization system, generate a synchronization signal according to the phase of the single-phase inverter, and send the synchronization signal to each slave in the single-phase inverter parallel synchronization system.

[0122] A phase following host module 604, configured to, if the mains power is abnormal and the single-phase inverter is a slave and receives the synchronization signal sent by the host in the single-phase inverter parallel synchronization system, correct the second quasi-tracking phase angle according to the synchronization signal to obtain a corrected value of the second quasi-tracking phase angle, and perform phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the second quasi-tracking phase angle.

[0123] On the other hand, an embodiment of the present invention provides a single-phase inverter, including: a control unit, a zero-crossing detection unit, and an output isolation unit.

[0124] The control unit includes: a memory, a processor, and a computer program. The memory is used to store the computer program, and the processor is used to call and run the computer program to execute the steps of the method in the first aspect or any possible implementation manner of the first aspect as described above.

[0125] The input end of the zero-crossing detection unit is used to be connected to the mains power, the output end of the zero-crossing detection unit is connected to the input end of the control unit, the output end of the control unit is connected to the input end of the output isolation unit, and the output end of the output isolation unit is connected to the CAP port of the control unit.

[0126] In this embodiment, please refer to Figure 4 and Figure 7 simultaneously. The single-phase inverter provided in the embodiment of the present invention includes: a control unit, a zero-crossing detection unit, and an output isolation unit. Among them, the input end of the zero-crossing detection unit is connected to the mains power, the output end of the zero-crossing detection unit is connected to the input end of the control unit, the output end of the control unit is connected to the input end of the output isolation unit, and the output end of the output isolation unit is connected to the CAP port of the control unit. In addition, the zero-crossing detection unit further includes: a differential sampling circuit and a comparison circuit, and the output isolation unit further includes: a signal amplification circuit and a signal isolation circuit; specifically, the input end of the differential sampling circuit is connected to the mains power, the output end of the differential sampling circuit is connected to the input end of the comparison circuit, the output end of the comparison circuit is connected to the input end of the control unit, the output end of the control unit is connected to the input end of the signal amplification circuit, the output end of the signal amplification circuit is connected to the input end of the signal isolation circuit, and the input end of the signal isolation circuit is connected to the CAP port of the control unit.

[0127] Figure 7 is a schematic structural diagram of the control unit provided in the embodiment of the present invention. As Figure 7 shown, the control unit 7 of this embodiment includes: a processor 70, a memory 71, and a computer program 72 stored in the memory 71 and operable on the processor 70. When the processor 70 executes the computer program 72, it implements the steps in the above-mentioned embodiments of the parallel synchronization method of each single-phase inverter, such as Figure 1 the steps 101 to 104 shown. Or, when the processor 70 executes the computer program 72, it implements the functions of each module in the above-mentioned device embodiments, such as Figure 6 the functions of the modules 601 to 604 shown.

[0128] Exemplarily, the computer program 72 can be segmented into one or more modules / units. The one or more modules / units are stored in the memory 71 and executed by the processor 70 to implement the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program 72 in the control unit 7. For example, the computer program 72 can be segmented into Figure 6 the modules 601 to 604 shown.

[0129] The control unit 7 can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The control unit 7 may include, but is not limited to, a processor 70 and a memory 71. Those skilled in the art can understand that Figure 7 this is only an example of the control unit 7 and does not constitute a limitation on the control unit 7. It may include more or fewer components than shown in the figure, or combine certain components, or different components. For example, the control unit may further include input / output devices, network access devices, a bus, etc.

[0130] The so-called processor 70 may be a central processing unit (CPU), or 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. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0131] The memory 71 may be an internal storage unit of the control unit 7, such as the hard disk or memory of the control unit 7. The memory 71 may also be an external storage device of the control unit 7, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the control unit 7. Further, the memory 71 may also include both the internal storage unit and the external storage device of the control unit. The memory 71 is used to store the computer program and other programs and data required by the control unit 7. The memory 71 may also be used to temporarily store the data that has been output or will be output.

[0132] Those skilled in the art can clearly understand that, for the convenience and conciseness of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiments can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of this application. The specific working processes of the units and modules in the above system can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0133] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0134] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A professional technician can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0135] In the embodiments provided by the present invention, it should be understood that the disclosed device / control unit and method can be implemented in other ways. For example, the device / control unit embodiments described above are merely illustrative. For example, the division of the module or unit is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the device or unit can be in electrical, mechanical or other forms.

[0136] The unit described as a separated component may or may not be physically separated, and the component displayed as a unit may or may not be a physical unit, that is, it can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0137] In addition, in each embodiment of the present invention, each functional unit can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0138] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-mentioned embodiment methods of the present invention, it can also be completed by a computer program instructing relevant hardware. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned embodiments of the single-phase inverter parallel synchronization method can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the content included in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electrical carrier signals and telecommunication signals.

[0139] The above-mentioned embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A single-phase inverter parallel operation synchronization method, characterized in that The single-phase inverter parallel synchronization method is applied to each of the single-phase inverters in a single-phase inverter parallel synchronization system including at least two single-phase inverters connected in parallel; The single-phase inverter parallel synchronization method includes: Determine whether the mains power is normal; If the mains power is normal, correct the first quasi-tracking phase angle according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first quasi-tracking phase angle, and perform phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the first quasi-tracking phase angle; If the mains power is abnormal and the single-phase inverter is the master, or if the mains power is abnormal and the single-phase inverter is a slave and the single-phase inverter preempts the master position in the single-phase inverter parallel synchronization system, generate a synchronization signal according to the phase of the single-phase inverter, and send the synchronization signal to each slave in the single-phase inverter parallel synchronization system; If the mains power is abnormal and the single-phase inverter is a slave and after receiving the synchronization signal sent by the master in the single-phase inverter parallel synchronization system, correct the second quasi-tracking phase angle according to the synchronization signal to obtain a corrected value of the second quasi-tracking phase angle, and perform phase synchronization on the current phase angle of the single-phase inverter according to the corrected value of the second quasi-tracking phase angle; The step of correcting the first quasi-tracking phase angle according to the high and low level signals output by the zero-crossing detection unit in the single-phase inverter to obtain a corrected value of the first quasi-tracking phase angle includes: Based on the interruption period of the control unit in the single-phase inverter, obtain the first quasi-tracking phase angle of the mains voltage at time i; where i is a positive integer; Determine whether the high and low level signal received by the single-phase inverter at time i is at the rising edge / falling edge; If the high and low level signal received by the single-phase inverter at time i is at the rising edge / falling edge, correct the first quasi-tracking phase angle at time i based on a first preset value to obtain a corrected value of the first quasi-tracking phase angle at time i; Alternatively, the step of correcting the second quasi-tracking phase angle according to the synchronization signal to obtain a corrected value of the second quasi-tracking phase angle includes: Based on the interruption period of the control unit in the single-phase inverter, obtain the second quasi-tracking phase angle of the master at time i; where i is a positive integer; Determine whether the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge; If the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge, correct the second quasi-tracking phase angle at time i based on a first preset value to obtain a corrected value of the second quasi-tracking phase angle at time i.

2. The single-phase inverter parallel synchronization method according to claim 1, wherein After determining whether the high and low level signal received by the single-phase inverter at time i is at the rising edge / falling edge, it further includes: If the high and low level signal received by the single-phase inverter at time i is not at the rising edge / falling edge, let i = i + 1, and return to execute the step of "based on the interruption period of the control unit in the single-phase inverter, obtain the first quasi-tracking phase angle of the mains voltage at time i" and subsequent steps; Alternatively, after determining whether the synchronization signal received by the single-phase inverter at time i is at the rising edge / falling edge, it further includes: If the synchronization signal received by the single-phase inverter at time i is not at the rising edge / falling edge, let i = i + 1, and return to execute the step of "acquiring the second quasi-tracking phase angle of the host at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps.

3. The single-phase inverter parallel synchronization method according to claim 1, characterized in that, Before correcting the first quasi-tracking phase angle at time i based on the first preset value to obtain the corrected value of the first quasi-tracking phase angle at time i, it further includes: Judging whether the frequency corresponding to the high and low level signals meets the first preset frequency range; If the frequency corresponding to the high and low level signals meets the first preset frequency range, correct the first quasi-tracking phase angle at time i based on the first preset value to obtain the corrected value of the first quasi-tracking phase angle at time i; If the frequency corresponding to the high and low level signals does not meet the first preset frequency range, let i = i + 1, and return to execute the step of "acquiring the first quasi-tracking phase angle of the mains voltage at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps; Alternatively, before correcting the second quasi-tracking phase angle at time i based on the first preset value to obtain the corrected value of the second quasi-tracking phase angle at time i, it further includes: Judging whether the frequency corresponding to the synchronization signal meets the second preset frequency range; If the frequency corresponding to the synchronization signal meets the second preset frequency range, correct the second quasi-tracking phase angle at time i based on the first preset value to obtain the corrected value of the first quasi-tracking phase angle at time i; If the frequency corresponding to the synchronization signal does not meet the second preset frequency range, let i = i + 1, and return to execute the step of "acquiring the second quasi-tracking phase angle of the host at time i based on the interruption period of the control unit in the single-phase inverter" and subsequent steps.

4. The single-phase inverter parallel synchronization method according to claim 1, characterized in that When acquiring the first quasi-tracking phase angle of the mains voltage at time i based on the interruption period of the control unit in the single-phase inverter, it further includes: Based on the interruption period, acquiring the current phase angle of the single-phase inverter at time i; The phase synchronization of the current phase angle of the single-phase inverter according to the corrected value of the first quasi-tracking phase angle includes: Based on the corrected value of the first quasi-tracking phase angle at time i and the interruption period, acquiring the first quasi-tracking phase angle of the mains voltage at time i + 1, and based on the current phase angle at time i and the interruption period, acquiring the current phase angle of the single-phase inverter at time i + 1; Calculating the absolute value of the first difference between the current phase angle at time i + 1 and the first quasi-tracking phase angle at time i + 1; When the absolute value of the first difference is greater than the preset threshold, adjusting the current phase angle at time i + 1 according to the preset step size to obtain the adjusted value of the current phase angle at time i + 1, so as to perform phase synchronization according to the adjusted value of the current phase angle at time i + 1; Alternatively, when acquiring the second quasi-tracking phase angle of the host at time i based on the interruption period of the control unit in the single-phase inverter, it further includes: Based on the interruption period, acquiring the current phase angle of the single-phase inverter at time i; The phase synchronization of the current phase angle of the single-phase inverter according to the corrected value of the second quasi-tracking phase angle includes: Based on the second pseudo-tracking phase angle correction value at time i and the interruption period, obtain the second pseudo-tracking phase angle of the host at time i + 1, and based on the current phase angle at time i and the interruption period, obtain the current phase angle of the single-phase inverter at time i + 1; Calculate the absolute value of the second difference between the current phase angle at time i + 1 and the second pseudo-tracking phase angle at time i + 1; When the absolute value of the second difference is greater than a preset threshold, adjust the current phase angle at time i + 1 according to a preset step size to obtain an adjusted value of the current phase angle at time i + 1, so as to perform phase synchronization according to the adjusted value of the current phase angle at time i + 1.

5. The single-phase inverter parallel synchronization method according to claim 4, characterized in that, The adjusting the current phase angle at time i + 1 according to a preset step size to obtain an adjusted value of the current phase angle at time i + 1 includes: According to θ”(t i+1 ) = θ'(t i+1 ) + flag×Δθ, the current phase angle at time i + 1 is adjusted to obtain the adjusted value of the current phase angle at time i + 1; where, θ”(t i+1 ) represents the current phase angle adjustment value at time i + 1, θ'(t i+1 ) represents the current phase angle at time i + 1, flag = 1 or flag = -1 represents the adjustment direction, and Δθ represents the preset step size.

6. The single-phase inverter parallel synchronization method according to claim 5, characterized in that When, in the case of adjusting the current phase angle at time i + 1 according to a preset step size to obtain an adjusted value of the current phase angle at time i + 1 when the absolute value of the first difference is greater than a preset threshold, the determination method of the value of the adjustment direction is: Judge whether the current phase angle at time i + 1 is less than the first pseudo-tracking phase angle at time i + 1; When the current phase angle at time i + 1 is less than the first pseudo-tracking phase angle at time i + 1, judge whether the absolute value of the first difference is greater than a first judgment condition; If the absolute value of the first difference is greater than the first judgment condition, then flag = -1; If the absolute value of the first difference is not greater than the first judgment condition, then flag = 1; When the current phase angle at time i + 1 is not less than the first pseudo-tracking phase angle at time i + 1, judge whether the absolute value of the first difference is greater than a second judgment condition; If the absolute value of the first difference is greater than the second judgment condition, then flag = 1; If the absolute value of the first difference is not greater than the second judgment condition, then flag = -1; Or, when, in the case of adjusting the current phase angle at time i + 1 according to a preset step size to obtain an adjusted value of the current phase angle at time i + 1 when the absolute value of the second difference is greater than a preset threshold, the determination method of the value of the adjustment direction is: Judge whether the current phase angle at time i + 1 is less than the second pseudo-tracking phase angle at time i + 1; When the current phase angle at time i + 1 is less than the second pseudo-tracking phase angle at time i + 1, judge whether the absolute value of the second difference is greater than a third judgment condition; If the absolute value of the second difference is greater than the third judgment condition, then flag = -1; If the absolute value of the second difference is not greater than the third judgment condition, then flag = 1; When the current phase angle at time i + 1 is not less than the second pseudo-tracking phase angle at time i + 1, judge whether the absolute value of the second difference is greater than a fourth judgment condition; If the absolute value of the second difference is greater than the fourth judgment condition, then flag = 1; If the absolute value of the second difference is not greater than the fourth judgment condition, then flag = -1.

7. A single-phase inverter, characterized in that, Includes: A control unit, a zero-crossing detection unit, and an output isolation unit; The control unit includes: a memory, a processor, and a computer program. The memory is used to store the computer program, and the processor is used to call and run the computer program to execute the method according to any one of claims 1 to 6; The input end of the zero-crossing detection unit is used to be connected to the mains power. The output end of the zero-crossing detection unit is connected to the input end of the control unit. The output end of the control unit is connected to the input end of the output isolation unit. The output end of the output isolation unit is connected to the CAP port of the control unit.

8. A single-phase inverter parallel synchronization system, characterized in that Comprising: At least two single-phase inverters according to claim 7; Wherein, the output end of the output isolation unit in each single-phase inverter is connected to the CAP port of the control unit in other single-phase inverters.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it realizes the steps of the method according to any one of claims 1 to 6 above.

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