A method, control device and system for wireless carrier synchronization of multiple inverters in parallel

Abstract

The application belongs to the technical field of parallel carrier synchronization of inverters, and relates to a wireless carrier synchronization method, a control device and a system for parallel inverters. The method is applied to the control device of each inverter in the wireless carrier synchronization system of parallel inverters. The method comprises the following steps: collecting a power grid voltage, and calculating a zero-crossing signal period based on the difference between the time stamps of two continuous zero-crossing moments of the power grid voltage, so as to obtain a carrier reference period; calculating a period ratio of the carrier reference period and a current carrier period of the inverter, rounding the period ratio, and obtaining the number of carrier periods that should be generated by the inverter in the carrier reference period; calculating a single theoretical carrier period of the inverter based on the carrier reference period and the number of carrier periods that should be generated by the inverter in the carrier reference period, rounding the single theoretical carrier period, and obtaining a target carrier period of the inverter; and phase-modulating the carrier of the inverter based on the target carrier period, so that the carrier of the inverter is synchronized with the power grid reference.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inverter parallel carrier synchronization, in particular to a kind of inverter multi-machine parallel wireless carrier synchronization method, control device and system. BACKGROUND

[0002] With the rapid development of energy storage industry, the demand for high-power scenarios is increasing, and single inverter is limited by the capacity of power devices, which cannot meet the demand for high power. Therefore, multiple inverters need to be used in parallel. However, when multiple inverters are connected in parallel, the carrier waves of different inverters are not synchronized, which will cause the voltage instantaneous value of each inverter output to be different, thereby generating voltage difference and causing high-frequency circulating current, reducing the working efficiency of the whole system.

[0003] In the prior art, the problem of multiple inverter carrier wave asynchronization is solved by increasing a synchronization signal line or through communication. In multiple inverters, an inverter with good stability and high sampling accuracy is selected as the master, and the remaining inverters are used as slaves. A synchronization signal line is set between the master and each slave to transmit the carrier wave synchronization signal of the master to all slaves. Each slave adjusts its carrier wave based on the carrier wave signal of the master, thereby realizing carrier wave synchronization of multiple inverters. However, this method requires additional communication lines and interface modules, and the interference between inverters needs to be considered when wiring, which increases the hardware cost. In addition, there are problems such as signal transmission delay when the carrier wave signal is transmitted from the master to the slave, which also leads to a decrease in synchronization accuracy.

[0004] In summary, the existing inverter multi-machine parallel carrier synchronization method has the problems of high hardware cost and low synchronization accuracy. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the problems of high hardware cost and low synchronization accuracy in the existing inverter multi-machine parallel carrier synchronization method.

[0006] To solve the above technical problems, the present application provides an inverter multi-machine parallel wireless carrier synchronization method, which is applied to the control device of each inverter in an inverter multi-machine parallel wireless carrier synchronization system. The method comprises:

[0007] Collecting the grid voltage and calculating the zero-crossing signal period based on the difference between the time stamps of the two consecutive zero-crossing instants of the grid voltage, thereby obtaining the carrier reference period;

[0008] Calculating the period ratio of the carrier reference period and the current carrier period of the inverter, and rounding the period ratio to obtain the number of carrier periods that the inverter should generate within the carrier reference period;

[0009] The single theoretical carrier period of the inverter is calculated based on the carrier reference period and the number of carrier periods that the inverter should generate in the carrier reference period, and the single theoretical carrier period is rounded to obtain the target carrier period of the inverter;

[0010] The carrier of the inverter is phase-modulated based on the target carrier period, so that the carrier of the inverter is synchronized with the grid reference.

[0011] Preferably, after obtaining the target carrier period of the inverter, the method further comprises:

[0012] The carrier period cumulative error of the inverter in the carrier reference period is calculated based on the difference between the single theoretical carrier period and the target carrier period, and the number of carrier periods that the inverter should generate in the carrier reference period;

[0013] The carrier phase-modulation step distance of the inverter is calculated based on the difference between the target carrier period and the current carrier period of the inverter, and the step cumulative error of the inverter from the current carrier period to the target carrier period is calculated based on the carrier phase-modulation step distance;

[0014] The cumulative compensation error is obtained based on the sum of the carrier period cumulative error and the step cumulative error, and the compensation error of a single carrier period is calculated based on the cumulative compensation error and the number of carrier periods that the inverter should generate in the carrier reference period;

[0015] The target carrier period of the inverter after error compensation is obtained based on the sum of the compensation error of a single carrier period and the target carrier period, so that the carrier of the inverter is phase-modulated.

[0016] Preferably, the step cumulative error of the inverter from the current carrier period to the target carrier period is calculated based on the carrier phase-modulation step distance, comprising:

[0017] When the target carrier period is greater than the current carrier period, the cumulative error sum of the positive step is calculated based on the carrier phase-modulation step distance, so that the step cumulative error of the inverter from the current carrier period to the target carrier period is obtained;

[0018] When the target carrier period is less than the current carrier period, the cumulative error sum of the negative step is calculated based on the carrier phase-modulation step distance, so that the step cumulative error of the inverter from the current carrier period to the target carrier period is obtained;

[0019] When the target carrier period is equal to the current carrier period, the step cumulative error of the inverter from the current carrier period to the target carrier period is 0.

[0020] Preferably, the carrier reference period is obtained by calculating the zero-crossing signal period, comprising:

[0021] The zero-crossing signal period is compared with a preset period threshold, and if the zero-crossing signal period is greater than or equal to the preset period threshold, the zero-crossing signal period is taken as the carrier reference period;

[0022] If the zero-crossing signal period is less than the preset period threshold, it is determined that the current power grid voltage has zero-crossing jitter, and the power grid voltage is re-acquired, a new zero-crossing signal period is calculated based on the difference between the time stamps of the two consecutive zero-crossing moments of the power grid voltage, and when the new zero-crossing signal period is greater than or equal to the preset threshold, the zero-crossing signal period is taken as the carrier reference period.

[0023] Preferably, the calculation formula of the period ratio of the carrier reference period to the current carrier period of the inverter is:

[0024] ,

[0025] , represents the period ratio; represents a floating point number; represents the carrier reference period; represents the current carrier period of the inverter;

[0026] The calculation formula of the number of carrier periods that the inverter should generate in the carrier reference period is:

[0027] ,

[0028] , represents the number of carrier periods that the inverter should generate in the carrier reference period; represents rounding.

[0029] Preferably, the calculation formula of a single theoretical carrier period of the inverter is:

[0030] ,

[0031] , represents a single theoretical carrier period of the inverter; represents a floating point number; represents the carrier reference period; represents the number of carrier periods that the inverter should generate in the carrier reference period;

[0032] The calculation formula of the target carrier period of the inverter is:

[0033] ,

[0034] , represents the target carrier period of the inverter; represents rounding.

[0035] Preferably, the formula for calculating the carrier period cumulative error of the inverter in the carrier reference period is:

[0036] ,

[0037] wherein, represents the carrier period cumulative error of the inverter in the carrier reference period; represents rounding; represents a single theoretical carrier period of the inverter; represents a target carrier period of the inverter; represents the number of carrier periods that should be generated by the inverter in the carrier reference period;

[0038] The formula for calculating the cumulative compensation error is:

[0039] ,

[0040] wherein, represents the cumulative compensation error; represents a step cumulative error;

[0041] The formula for calculating the compensation error of a single carrier period is:

[0042] ,

[0043] wherein, represents the compensation error of a single carrier period.

[0044] Preferably, the formula for calculating the cumulative error sum of forward steps is:

[0045] ,

[0046] ,

[0047] wherein, represents the cumulative error sum of forward steps; represents a carrier phase modulation step distance; represents a target carrier period of the inverter; represents a current carrier period of the inverter;

[0048] The formula for calculating the cumulative error sum of backward steps is:

[0049] ,

[0050] wherein, represents the cumulative error sum of backward steps.

[0051] The application further provides a control device for implementing the steps of the inverter multi-machine parallel wireless carrier synchronization method, and the control device comprises:

[0052] A carrier reference acquisition module is configured to collect a power grid voltage, and calculate a zero-crossing signal period based on a difference between time stamps of two consecutive zero-crossing moments of the power grid voltage, so as to obtain a carrier reference period.

[0053] A theoretical carrier period number calculation module is configured to calculate a period ratio of the carrier reference period and a current carrier period of the inverter, and round the period ratio to obtain a number of carrier periods that the inverter should generate in the carrier reference period.

[0054] A target carrier period calculation module is configured to calculate a single theoretical carrier period of the inverter based on the carrier reference period and the number of carrier periods that the inverter should generate in the carrier reference period, and round the single theoretical carrier period to obtain a target carrier period of the inverter.

[0055] A phase modulation module is configured to modulate the carrier of the inverter based on the target carrier period, so that the carrier of the inverter is synchronized with the power grid reference.

[0056] The application further provides an inverter multi-machine parallel wireless carrier synchronization system, comprising a plurality of parallel inverters, and each inverter comprises the control device.

[0057] The inverter multi-machine parallel wireless carrier synchronization method has the following beneficial effects:

[0058] 1. The grid voltage zero-crossing signal is acquired through the grid voltage sampling circuit of the inverter itself, and then the carrier reference period is calculated. For each inverter connected in parallel, the phase of its PWM carrier is adjusted based on the carrier reference period, thereby achieving synchronization between the PWM carrier and the carrier reference period. Since all inverters are synchronized with the carrier reference period, the carriers of all inverters are also synchronized. Meanwhile, when calculating the target carrier period of each inverter, this application considers that the grid frequency is not fixed in actual applications. Therefore, the ratio of the carrier reference period to the inverter carrier period may not be divisible. Since the inverter carrier period usually needs to be configured in integer form, the phase of the carrier reference period is adjusted by adjusting the phase of the PWM carrier. The period ratio is rounded to the nearest integer between the theoretically calculated non-integer value and the actual configurable value, thus meeting the engineering requirements while ensuring a certain level of accuracy. In addition, after calculating the single theoretical carrier cycle of the inverter based on the number of certified carrier cycles, the single theoretical carrier cycle is also rounded to the nearest integer to obtain the target carrier cycle, which evenly distributes the approximation error across multiple carrier cycles of the entire number of carrier cycles, thereby improving the carrier synchronization rate of multiple inverters. There is no need to add synchronization signal lines or communication lines, reducing hardware costs. There is also no need for carrier signal transmission between the inverters, thus eliminating the problem of low carrier synchronization accuracy caused by transmission delay.

[0059] 2. There are two sources of error in the process of multi-unit parallel carrier synchronization of inverters. The first is that the target carrier period calculated by this application using rounding will approximate the theoretical non-integer value to an integer, which will introduce errors. The second is that when the inverter carrier is phase-modulated based on the target carrier period, a step adjustment method is often used. Instead of directly adjusting the current carrier period to the target carrier period instantaneously, it is adjusted gradually with a certain step size. In the step adjustment process, each step adjustment will deviate from the ideal continuous adjustment value. Therefore, step error will also be introduced in the entire step adjustment process. Based on this, after obtaining the target carrier period of the inverter, this application also calculates the compensation values ​​of the above two errors to compensate for the target carrier period, thereby further improving the accuracy of multi-unit parallel carrier synchronization of inverters. Attached Figure Description

[0060] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0061] Figure 1 Flowchart of the method for wireless carrier synchronization of multiple inverters in parallel provided in this application;

[0062] Figure 2 This is a schematic diagram of the inverter carrier cycle adjustment process provided in this application. DETAILED DESCRIPTION

[0063] The application will be further described below in conjunction with the drawings and specific embodiments so that those skilled in the art can better understand and implement the application, but the embodiments are not intended to limit the application.

[0064] Please refer to Figure 1 , Figure 1 The figure is a flow chart of the inverter multi-machine parallel wireless carrier synchronization method provided by the application. The method is applied to the control device of each inverter in the inverter multi-machine parallel wireless carrier synchronization system. The method specifically includes the following steps.

[0065] S10: Collect the grid voltage, and calculate the zero-crossing signal period based on the difference between the time stamps of the two consecutive zero-crossing moments of the grid voltage, thereby obtaining the carrier reference period.

[0066] Further, due to the poor actual grid quality or sampling circuit performance and other problems, there may be jitter at the zero-crossing of the grid voltage. The core role of the carrier reference period is to provide a stable and unified time reference for the carrier synchronization of the inverters. The zero-crossing jitter will cause the calculated zero-crossing signal period to randomly fluctuate, thereby affecting the regulation accuracy of the carrier periods of multiple inverters, and further failing to achieve the carrier synchronization of multiple inverters. Therefore, the application performs zero-crossing jitter processing after calculating the zero-crossing signal period.

[0067] Specifically, calculating the zero-crossing signal period, thereby obtaining the carrier reference period includes the following steps.

[0068] Step 1-1: Compare the zero-crossing signal period with the preset period threshold. If the zero-crossing signal period is greater than or equal to the preset period threshold, the zero-crossing signal period is taken as the carrier reference period.

[0069] Step 1-2: If the zero-crossing signal period is less than the preset period threshold, it is determined that the current grid voltage has zero-crossing jitter, and the grid voltage is re-collected. A new zero-crossing signal period is calculated based on the difference between the time stamps of the two consecutive zero-crossing moments of the grid voltage. When the new zero-crossing signal period is greater than or equal to the preset threshold, the zero-crossing signal period is taken as the carrier reference period.

[0070] S20: Calculate the period ratio of the carrier reference period and the current carrier period of the inverter, and round the period ratio to obtain the number of carrier periods that the inverter should generate within the carrier reference period.

[0071] S30: Based on the carrier reference period and the number of carrier periods that the inverter should generate within the carrier reference period, calculate the single theoretical carrier period of the inverter, and round the single theoretical carrier period to obtain the target carrier period of the inverter.

[0072] S40: Phase-modulate the carrier of the inverter based on the target carrier period, so that the carrier of the inverter is synchronized with the grid reference.

[0073] Specifically, in actual application, the grid frequency is not fixed, so the period ratio of the carrier reference period to the inverter carrier period cannot be divided, and the inverter carrier period usually needs to be configured in an integer form. The application takes the closest integer between the non-integer value calculated in theory and the actually configurable value by rounding the period ratio, thereby meeting the needs of engineering implementation under the premise of ensuring a certain accuracy. At the same time, after calculating the single theoretical carrier period of the inverter based on the carrier period number obtained after rounding, the target carrier period is also rounded to an integer. Although this integer form of target carrier period will bring a certain error, compared with direct truncation and other methods, rounding can more evenly distribute the error in multiple carrier periods of the carrier period number, thereby improving the carrier synchronization rate of multiple inverters.

[0074] Specifically, the calculation formula of the period ratio of the carrier reference period to the current carrier period of the inverter is:

[0075] ,

[0076] wherein, represents the period ratio; represents a floating point number; represents the carrier reference period; represents the current carrier period of the inverter.

[0077] The calculation formula of the carrier period number that the inverter should generate in the carrier reference period is:

[0078] ,

[0079] wherein, represents the carrier period number that the inverter should generate in the carrier reference period; represents rounding.

[0080] The calculation formula of the single theoretical carrier period of the inverter is:

[0081] ,

[0082] wherein, represents the single theoretical carrier period of the inverter; represents a floating point number; represents the carrier reference period; represents the carrier period number that the inverter should generate in the carrier reference period.

[0083] It should be noted that in the PWM generation process of the inverter, the center alignment (up and down) counting mode is adopted, specifically, the counter will first count up from 0 to the carrier period value, and then count down to 0, completing a complete PWM period, at this time, the counting value range of the counter is from 0 to the carrier period value to 0, corresponding to 2 times the carrier period. Based on this, when calculating the single theoretical carrier period after the carrier reference period is evenly divided, the carrier reference period needs to be divided by the number of carrier periods in the single period reference, and then divided by 2, so as to match the PWM center alignment counting mode.

[0084] The calculation formula of the target carrier period of the inverter is:

[0085]

[0086] Among them, The target carrier period of the inverter is represented; The integral is represented.

[0087] Further, in the carrier synchronization process of the inverter multi-machine parallel, there are two error sources, the first is that the target carrier period calculated by the rounding method adopted by the present application will approximate the theoretical non-integer value to an integer, and this approximation operation will introduce errors; the second is that when the carrier of the inverter is phase-modulated based on the target carrier period, a step adjustment method is often adopted, and the current carrier period is not directly adjusted to the target carrier period, but is adjusted step by step with a certain step size, and in the step adjustment process, each step adjustment will deviate from the ideal continuous adjustment value, so that a step error will also be introduced in the whole step adjustment process, therefore, after obtaining the target carrier period of the inverter, the present application also calculates the compensation values of the above two errors to compensate the target carrier period.

[0088] Specifically, after obtaining the target carrier period of the inverter, the following steps are further included:

[0089] Step 2-1: based on the difference between the single theoretical carrier period and the target carrier period, and the number of carrier periods that the inverter should generate in the carrier reference period, the carrier period cumulative error of the inverter in the carrier reference period is calculated.

[0090] Step 2-2: based on the difference between the target carrier period and the current carrier period of the inverter, the carrier phase modulation step distance of the inverter is calculated; based on the carrier phase modulation step distance, the step cumulative error of the inverter from the current carrier period to the target carrier period is calculated.

[0091] Step 2-3: based on the sum of the carrier period cumulative error and the step cumulative error, the cumulative compensation error is obtained; based on the cumulative compensation error and the number of carrier periods that the inverter should generate in the carrier reference period, the compensation error of a single carrier period is calculated. ​

[0092] Step 2-4: obtain the target carrier period of the error-compensated inverter based on the sum of the compensation error of the single carrier period and the target carrier period, so as to phase-modulate the carrier of the inverter.

[0093] Further, the step 2-2 calculates the step cumulative error of the inverter from the current carrier period to the target carrier period based on the carrier phase-modulation step distance, including:

[0094] Step 3-1: when the target carrier period is greater than the current carrier period, calculate the cumulative error sum of the positive step based on the carrier phase-modulation step distance, so as to obtain the step cumulative error of the inverter from the current carrier period to the target carrier period.

[0095] Step 3-2: when the target carrier period is less than the current carrier period, calculate the cumulative error sum of the negative step based on the carrier phase-modulation step distance, so as to obtain the step cumulative error of the inverter from the current carrier period to the target carrier period.

[0096] Step 3-3: when the target carrier period is equal to the current carrier period, the step cumulative error of the inverter from the current carrier period to the target carrier period is 0.

[0097] Specifically, the calculation formula of the carrier period cumulative error of the inverter in the carrier reference period is:

[0098] ,

[0099] wherein, represents the carrier period cumulative error of the inverter in the carrier reference period; represents rounding; represents the single theoretical carrier period of the inverter; represents the target carrier period of the inverter; represents the number of carrier periods that should be generated by the inverter in the carrier reference period.

[0100] The calculation formula of the cumulative compensation error is:

[0101] ,

[0102] wherein, represents the cumulative compensation error; represents the step cumulative error.

[0103] The calculation formula of the compensation error of the single carrier period is:

[0104] ,

[0105] wherein, represents the compensation error of the single carrier period.

[0106] Further, the calculation formula of the cumulative error sum of the positive step in step 3-1 is as follows:

[0107]

[0108]

[0109] wherein, represents the cumulative error sum of the positive step; represents the carrier phase step; represents the target carrier period of the inverter; represents the current carrier period of the inverter.

[0110] The calculation formula of the cumulative error sum of the negative step in step 3-2 is as follows:

[0111]

[0112] wherein, represents the cumulative error sum of the negative step.

[0113] Further, after the compensated target carrier period is obtained, only the carrier period of each inverter needs to be adjusted to the compensated target carrier period in a step-by-step manner, so as to realize the consistency of the frequency of each inverter with the grid frequency, and realize the carrier synchronization of multiple parallel inverters. Figure 2 FIG. 4 shows a carrier period adjustment flowchart of a single inverter provided by the present application.

[0114] The embodiment of the present application further provides a control device used for implementing the steps of the inverter multi-machine parallel wireless carrier synchronization method.

[0115] The carrier reference acquisition module is used for collecting the grid voltage, and calculating the zero-crossing signal period based on the difference between the time stamps of two continuous zero-crossing moments, so as to obtain the carrier reference period.

[0116] The theoretical carrier period number calculation module is used for calculating the period ratio of the carrier reference period and the current carrier period of the inverter, and rounding the period ratio to obtain the carrier period number that should be generated by the inverter in the carrier reference period.

[0117] The target carrier period calculation module is used for calculating the single theoretical carrier period of the inverter based on the carrier reference period and the carrier period number that should be generated by the inverter in the carrier reference period, and rounding the single theoretical carrier period to obtain the target carrier period of the inverter.

[0118] ​​​The phase modulation module is configured to modulate the carrier of the inverter based on the target carrier period, so that the carrier of the inverter is synchronized with the grid reference.

[0119] The embodiment of the present application further provides an inverter multi-machine parallel wireless carrier synchronization system, which comprises a plurality of parallel inverters, and each inverter comprises the control device.

[0120] In conclusion, the inverter multi-machine parallel wireless carrier synchronization method provided by the present application does not need to increase a synchronization signal line or a communication line, directly samples and processes the grid voltage to obtain a zero-crossing signal, and then calculates a carrier reference period, and for each parallel inverter, the PWM carrier is modulated based on the carrier reference period, so that the PWM carrier is synchronized with the carrier reference period, and since all the inverters are synchronized with the carrier reference period, the carriers of all the inverters are also synchronized; meanwhile, when calculating the target carrier period of each inverter, the carrier period adjustment of the inverter is considered to be an integer, a rounding processing method is introduced, and based on the error introduced by the approximate operation and the step error introduced when modulating the carrier of the inverter, a compensation value is calculated, and the target carrier period is compensated based on the compensation value, so that the PWM waves output by the plurality of inverters are more consistent in phase, and the precision of carrier synchronization is further improved.

[0121] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can adopt a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can adopt a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0122] The present application is described with reference to flowcharts and / or block diagrams according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one flow or multiple flows and / or blocks.

[0123] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0124] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0125] Obviously, the above-described embodiments are only examples and are not intended to limit the present application. Based on the above description, one of ordinary skill in the art can make other variations and changes without departing from the present application. It is not necessary to recite all of the embodiments, and obvious changes or variations are not included herein. However, such obvious changes or variations are still within the scope of the present application.

Claims

1. A method for wireless carrier synchronization of multiple inverters in parallel, characterized by, The method is applied to a control device of each inverter in a wireless carrier synchronization system of multiple inverters in parallel, and the method comprises the following steps: Collecting a grid voltage, and calculating a zero-crossing signal period based on a difference between time stamps of two continuous zero-crossing moments of the grid voltage, so as to obtain a carrier reference period; Calculating a period ratio of the carrier reference period and a current carrier period of the inverter, and rounding the period ratio to obtain a number of carrier periods that the inverter should generate in the carrier reference period; wherein the calculation formula of the period ratio of the carrier reference period and the current carrier period of the inverter is: ， wherein, denotes a cycle ratio; denotes a floating point number; denotes a carrier reference cycle; denotes an inverter current carrier cycle; Based on the carrier reference period and the number of carrier periods that the inverter should generate in the carrier reference period, calculating a single theoretical carrier period of the inverter, and rounding the single theoretical carrier period to obtain a target carrier period of the inverter; based on a difference between the single theoretical carrier period and the target carrier period and the number of carrier periods that the inverter should generate in the carrier reference period, calculating a carrier period cumulative error of the inverter in the carrier reference period; based on a difference between the target carrier period and the current carrier period of the inverter, calculating a carrier phase stepping distance of the inverter; based on the carrier phase stepping distance, calculating a stepping cumulative error of the inverter from the current carrier period to the target carrier period; based on a sum of the carrier period cumulative error and the stepping cumulative error, obtaining a cumulative compensation error; based on the cumulative compensation error and the number of carrier periods that the inverter should generate in the carrier reference period, calculating a compensation error of a single carrier period; based on a sum of the compensation error of the single carrier period and the target carrier period, obtaining the target carrier period of the inverter after error compensation; wherein the calculation formula of the single theoretical carrier period of the inverter is: ， wherein, represents a single theoretical carrier cycle of the inverter; represents a floating point number; represents a carrier reference cycle; represents the number of carrier cycles the inverter should generate within the carrier reference cycle; Based on the target carrier period, adjusting the carrier of the inverter, so that the carrier of the inverter is synchronized with the grid reference.

2. The method of claim 1, wherein, The calculation of the stepping cumulative error of the inverter from the current carrier period to the target carrier period based on the carrier phase stepping distance comprises: When the target carrier period is greater than the current carrier period, calculating a sum of cumulative errors of positive stepping based on the carrier phase stepping distance, so as to obtain the stepping cumulative error of the inverter from the current carrier period to the target carrier period; When the target carrier period is less than the current carrier period, calculating a sum of cumulative errors of negative stepping based on the carrier phase stepping distance, so as to obtain the stepping cumulative error of the inverter from the current carrier period to the target carrier period; When the target carrier period is equal to the current carrier period, the stepping cumulative error of the inverter from the current carrier period to the target carrier period is 0.

3. The method of claim 1, wherein, The calculation of the zero-crossing signal period, so as to obtain the carrier reference period, comprises: Comparing the zero-crossing signal period with a preset period threshold value, if the zero-crossing signal period is greater than or equal to the preset period threshold value, taking the zero-crossing signal period as the carrier reference period; If the zero-crossing signal period is less than the preset period threshold value, determining that there is zero-crossing jitter in the current grid voltage, and re-collecting the grid voltage, calculating a new zero-crossing signal period based on a difference between time stamps of two continuous zero-crossing moments of the grid voltage, and when the new zero-crossing signal period is greater than or equal to the preset threshold value, taking the zero-crossing signal period as the carrier reference period.

4. The method of claim 1, wherein, The calculation formula of the number of carrier periods that the inverter should generate in the carrier reference period is: ， wherein represents the number of carrier cycles that the inverter should generate within the carrier reference period; represents rounding.

5. The method of claim 1, wherein, The formula for calculating the target carrier period of the inverter is: ， wherein denotes the target carrier period of the inverter; denotes rounding.

6. The method of claim 1, wherein, The formula for calculating the carrier period cumulative error of the inverter in the carrier reference period is: ， wherein, represents the carrier period cumulative error of the inverter over the carrier reference period; represents rounding; represents the single theoretical carrier period of the inverter; represents the target carrier period of the inverter; represents the number of carrier periods that should be generated by the inverter over the carrier reference period; The formula for calculating the cumulative compensation error is: ， wherein, represents the accumulated compensation error; represents the step accumulated error; The formula for calculating the compensation error of a single carrier period is: ， wherein denotes the compensation error for a single carrier cycle.

7. The method of claim 2, wherein the wireless carrier synchronization is performed by a plurality of inverters in parallel connection. The formula for calculating the cumulative error sum of the forward step is: ， ， wherein, represents a cumulative error and of a forward step; represents a carrier phase step distance; represents a target carrier period of the inverter; represents a current carrier period of the inverter; The formula for calculating the cumulative error sum of the negative step is: ， wherein, represents the cumulative error sum of the negative steps.

8. A control device characterized by comprising: The control device is used to implement the steps of the inverter multi-machine parallel wireless carrier synchronization method according to any one of claims 1 to 7, and the control device comprises: A carrier reference acquisition module is configured to collect a power grid voltage, and calculate a zero-crossing signal period based on the difference between the time stamps of two consecutive zero-crossing moments of the power grid voltage, thereby obtaining a carrier reference period; A theoretical carrier period number calculation module is configured to calculate the period ratio of the carrier reference period to the current carrier period of the inverter, and round the period ratio to obtain the number of carrier periods that the inverter should generate in the carrier reference period; wherein the formula for calculating the period ratio of the carrier reference period to the current carrier period of the inverter is: ， wherein, denotes a period ratio; denotes a floating point number; denotes a carrier reference period; denotes an inverter current carrier period; A target carrier period calculation module is configured to calculate a single theoretical carrier period of the inverter based on the carrier reference period and the number of carrier periods that the inverter should generate in the carrier reference period, and round the single theoretical carrier period to obtain a target carrier period of the inverter; calculate a carrier phase stepping distance of the inverter based on the difference between the single theoretical carrier period and the target carrier period, and the number of carrier periods that the inverter should generate in the carrier reference period; calculate the step cumulative error of the inverter from the current carrier period to the target carrier period based on the carrier phase stepping distance; obtain a cumulative compensation error based on the sum of the carrier period cumulative error and the step cumulative error; calculate a compensation error of a single carrier period based on the cumulative compensation error and the number of carrier periods that the inverter should generate in the carrier reference period; obtain the target carrier period of the inverter after error compensation based on the sum of the compensation error of the single carrier period and the target carrier period; wherein the formula for calculating the single theoretical carrier period of the inverter is: ， wherein, represents a single theoretical carrier cycle of the inverter; represents a floating point number; represents a carrier reference cycle; represents the number of carrier cycles the inverter should generate within the carrier reference cycle; A phase modulation module is configured to modulate the carrier of the inverter based on the target carrier period, so that the carrier of the inverter is synchronized with the power grid reference.

9. A wireless carrier synchronization system for multiple inverters in parallel, characterized in that, The control device is used to implement the steps of the inverter multi-machine parallel wireless carrier synchronization method according to any one of claims 1 to 7, and the control device comprises: A carrier reference acquisition module is configured to collect a power grid voltage, and calculate a zero-crossing signal period based on the difference between the time stamps of two consecutive zero-crossing moments of the power grid voltage, thereby obtaining a carrier reference period; A theoretical carrier period number calculation module is configured to calculate the period ratio of the carrier reference period to the current carrier period of the inverter, and round the period ratio to obtain the number of carrier periods that the inverter should generate in the carrier reference period; wherein the formula for calculating the period ratio of the carrier reference period to the current carrier period of the inverter is: A target carrier period calculation module is configured to calculate a single theoretical carrier period of the inverter based on the carrier reference period and the number of carrier periods that the inverter should generate in the carrier reference period, and round the single theoretical carrier period to obtain a target carrier period of the inverter; calculate a carrier phase stepping distance of the inverter based on the difference between the single theoretical carrier period and the target carrier period, and the number of carrier periods that the inverter should generate in the carrier reference period; calculate the step cumulative error of the inverter from the current carrier period to the target carrier period based on the carrier phase stepping distance; obtain a cumulative compensation error based on the sum of the carrier period cumulative error and the step cumulative error; calculate a compensation error of a single carrier period based on the cumulative compensation error and the number of carrier periods that the inverter should generate in the carrier reference period; obtain the target carrier period of the inverter after error compensation based on the sum of the compensation error of the single carrier period and the target carrier period; wherein the formula for calculating the single theoretical carrier period of the inverter is: A phase modulation module is configured to modulate the carrier of the inverter based on the target carrier period, so that the carrier of the inverter is synchronized with the power grid reference. The control device is used to implement the steps of the inverter multi-machine parallel wireless carrier synchronization method according to any one of claims 1 to 7, and the control device comprises:

Images