Control method, device and equipment of grid-connected inverter and storage medium

Abstract

Embodiments of the present application disclose a grid-connected inverter control method, device, equipment and storage medium. The grid-connected inverter control method comprises: calculating a grid voltage prediction value in a two-phase stationary coordinate system in a current period according to a grid voltage sample value in the two-phase stationary coordinate system in a previous period, a variation angle of a three-phase grid voltage space vector and a preset numerical relationship; judging whether a grid voltage drop occurs according to a numerical relationship between an absolute value of a difference between the grid voltage sample value in the two-phase stationary coordinate system in the current period and the grid voltage prediction value and a preset voltage value; and controlling the grid-connected inverter according to a judgment result. The technical scheme of the embodiments of the present application is helpful to improve the judgment speed of the grid voltage drop, thereby relieving the problem of the grid voltage drop and improving the adaptability of the grid-connected inverter to the grid voltage drop.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of new energy power generation technology, and in particular to a control method, device, equipment and storage medium for a grid-connected inverter. Background Technology

[0002] Currently, renewable energy generation has become one of the main forms of power generation. The power fluctuations of photovoltaic and wind power generation can impact the power grid; therefore, the grid adaptability of renewable energy generation cannot be ignored. The ability of grid-connected inverters to adapt to grid voltage dips is an important component of grid adaptability.

[0003] Current technologies for detecting grid voltage dips generally rely on the dual dq decomposition of the grid voltage. This involves iteratively filtering the d-axis component of the grid voltage and using the filtered d-axis value as the criterion for voltage dip detection. However, this iterative filtering process is time-consuming. As a result, it takes approximately 5ms from the actual occurrence of a grid voltage dip to the determination that the grid has entered a low-voltage state. This excessive time hinders the mitigation of grid voltage dip problems and makes it difficult to improve the adaptability of grid-connected inverters to grid voltage dips. Summary of the Invention

[0004] This invention provides a control method, apparatus, device, and storage medium for a grid-connected inverter to improve the speed of detecting grid voltage dips, thereby alleviating the problem of grid voltage dips and improving the adaptability of the grid-connected inverter to grid voltage dips.

[0005] In a first aspect, embodiments of the present invention provide a control method for a grid-connected inverter, comprising:

[0006] The three-phase grid voltage sampling values ​​for each cycle are acquired in real time, and the three-phase grid voltage sampling values ​​for each cycle are converted into grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0007] Based on the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle, the change angle of the three-phase grid voltage space vector, and the preset numerical relationship, the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle is calculated; wherein, the preset numerical relationship is the numerical relationship between the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle, the grid voltage value in the two-phase stationary coordinate system of the previous cycle, and the change angle of the three-phase grid voltage space vector.

[0008] Based on the numerical relationship between the absolute value of the difference between the grid voltage sample value and the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the preset voltage value, it is determined whether a grid voltage drop has occurred.

[0009] The grid-connected inverter is controlled based on the judgment result.

[0010] Optionally, the two-phase stationary coordinate system includes an α-axis and a β-axis; the grid voltage sample value in the two-phase stationary coordinate system of the previous cycle includes the grid voltage sample value component on the α-axis and the grid voltage sample value component on the β-axis; the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle includes the grid voltage prediction value component on the α-axis and the grid voltage prediction value component on the β-axis.

[0011] The preset numerical relationships include a first numerical relationship between the grid voltage prediction component on the α-axis of the current period and the grid voltage sampled component on the α-axis, the grid voltage sampled component on the β-axis of the previous period, and the change angle of the three-phase grid voltage space vector; and a second numerical relationship between the grid voltage prediction component on the β-axis of the current period and the grid voltage sampled component on the α-axis, the grid voltage sampled component on the β-axis of the previous period, and the change angle of the three-phase grid voltage space vector.

[0012] Based on the grid voltage sampling values ​​in the two-phase stationary coordinate system of the previous cycle, the changing angle of the spatial vector of the three-phase grid voltage synthesis in each cycle, and the preset numerical relationships, the predicted grid voltage values ​​in the two-phase stationary coordinate system of the current cycle are calculated, including:

[0013] Based on the grid voltage sampled value components on the α-axis and β-axis of the previous period, the change angle of the three-phase grid voltage space vector, and the first numerical relationship, calculate the grid voltage predicted value components on the α-axis of the current period.

[0014] Based on the grid voltage sampled value components on the α-axis and β-axis of the previous cycle, the change angle of the three-phase grid voltage space vector, and the second numerical relationship, the predicted grid voltage component on the β-axis of the current cycle is calculated.

[0015] Optionally, the first numerical relationship is expressed as:

[0016] U1α=Ualpha*cosB-Ubeta*sinB;

[0017] The second numerical relationship is expressed as follows:

[0018] U1β=Ualpha*sinB+Ubeta*cosB;

[0019] Wherein, U1α is the predicted grid voltage component on the α-axis of the current cycle, U1β is the predicted grid voltage component on the β-axis of the current cycle, Ualpha is the sampled grid voltage component on the α-axis of the previous cycle, Ubeta is the sampled grid voltage component on the β-axis of the previous cycle, and B is the angle of change of the three-phase grid voltage space vector.

[0020] Optionally, the grid voltage sample value in the two-phase stationary coordinate system of the current period includes the grid voltage sample value component on the α coordinate axis and the grid voltage sample value component on the β coordinate axis; the preset voltage value includes a first preset voltage value and a second preset voltage value;

[0021] Based on the numerical relationship between the absolute value of the difference between the current period's two-phase stationary coordinate system voltage sample value and the predicted voltage value, and the preset voltage value, it is determined whether a grid voltage drop has occurred, including:

[0022] If the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the α axis of the current period is greater than the first preset voltage value, and / or the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the β axis of the current period is greater than the second preset voltage value, then a grid voltage drop is determined to have occurred.

[0023] Optionally, it also includes:

[0024] If the absolute value of the difference between the sampled grid voltage component and the predicted grid voltage component on the α axis of the next cycle is less than or equal to the third preset voltage value, and the absolute value of the difference between the sampled grid voltage component and the predicted grid voltage component on the β axis of the next cycle is less than or equal to the fourth preset voltage value, then the grid voltage is determined to have returned to normal.

[0025] Optionally, the grid-connected inverter is controlled based on the judgment result, including:

[0026] If a grid voltage drop occurs, the output current of the grid-connected inverter is controlled using a deadbeat current prediction control method. The deadbeat current prediction control method includes: adjusting the output current of the grid-connected inverter to the required value in the next cycle by controlling the output voltage of the grid-connected inverter based on the numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage, and inductance value of the current cycle.

[0027] Optionally, the output current of the grid-connected inverter includes an output current component on the α-axis and an output current component on the β-axis; the output voltage of the grid-connected inverter includes an output voltage component on the α-axis and an output voltage component on the β-axis; and the grid voltage includes a grid voltage component on the α-axis and a grid voltage component on the β-axis.

[0028] The numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage, and inductance value of the grid-connected inverter in the current cycle is expressed as follows:

[0029] Iα(n+1)=Iα(n)+Ts*(U'α-Eα) / Ls;

[0030] Iβ(n+1)=Iβ(n)+Ts*(U'β-Eβ) / Ls;

[0031] Where Iα(n+1) is the expected output current component on the α-axis of the next cycle, Iβ(n+1) is the expected output current component on the β-axis of the next cycle, Iα(n) is the output current component on the α-axis of the current cycle, Iβ(n) is the output current component on the β-axis of the current cycle, Ts is the cycle duration, U'α is the output voltage component on the α-axis of the current cycle, U'β is the output voltage component on the β-axis of the current cycle, Eα is the grid voltage component on the α-axis of the current cycle, Eβ is the grid voltage component on the β-axis of the current cycle, and Ls is the inductance value of the grid-connected inverter.

[0032] Optionally, controlling the grid-connected inverter based on the judgment result also includes:

[0033] If the output current component of the grid-connected inverter on the α-axis is greater than or equal to a first set value, and / or the output current component of the grid-connected inverter on the β-axis is greater than or equal to a second set value, then the output current of the grid-connected inverter is controlled by the deadbeat current prediction control method.

[0034] Optionally, controlling the grid-connected inverter based on the judgment result also includes:

[0035] If the output current component of the grid-connected inverter on the α coordinate axis is less than the first set value, and the output current component of the grid-connected inverter on the β coordinate axis is less than the second set value, then the output current of the grid-connected inverter is controlled by the dual dq control method.

[0036] Secondly, embodiments of the present invention also provide a control device for a grid-connected inverter, comprising:

[0037] The power grid voltage sampling value acquisition module is used to acquire the three-phase power grid voltage sampling values ​​of each cycle in real time, and convert the three-phase power grid voltage sampling values ​​of each cycle into power grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0038] The grid voltage prediction calculation module is used to calculate the grid voltage prediction value in the two-phase stationary coordinate system for the current period based on the grid voltage sampling value in the two-phase stationary coordinate system of the previous period, the change angle of the three-phase grid voltage space vector, and a preset numerical relationship; wherein, the preset numerical relationship is the numerical relationship between the grid voltage prediction value in the two-phase stationary coordinate system of the current period, the grid voltage value in the two-phase stationary coordinate system of the previous period, and the change angle of the three-phase grid voltage space vector.

[0039] The judgment module is used to determine whether a grid voltage drop has occurred based on the numerical relationship between the absolute value of the difference between the grid voltage sample value and the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the preset voltage value.

[0040] The control module is used to control the grid-connected inverter based on the judgment result.

[0041] Thirdly, embodiments of the present invention also provide an electronic device, the electronic device comprising:

[0042] One or more processors;

[0043] Storage device for storing one or more programs;

[0044] When the one or more programs are executed by the one or more processors, the one or more processors implement the control method for the grid-connected inverter as described in the first aspect.

[0045] Fourthly, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the control method for a grid-connected inverter as described in the first aspect.

[0046] The control method, apparatus, device, and storage medium for grid-connected inverters provided in this invention utilize the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle to calculate the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle. Based on the deviation between the grid voltage sampling value and the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle, it determines whether a grid voltage drop has occurred. This enables the determination of whether a grid voltage drop has occurred within one control cycle, thereby improving the speed of grid voltage drop detection. The technical solution of this invention, by controlling the grid-connected inverter based on the grid voltage drop determination result, also helps to quickly suppress overcurrent in the grid-connected inverter caused by grid voltage drops, thereby alleviating the grid voltage drop problem and avoiding overcurrent protection of the grid-connected inverter, thus improving the adaptability of the grid-connected inverter to grid voltage drops. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating a control method for a grid-connected inverter provided in an embodiment of the present invention;

[0048] Figure 2 This is a spatial vector diagram of a three-phase power grid voltage provided in an embodiment of the present invention;

[0049] Figure 3 This is a flowchart illustrating another control method for a grid-connected inverter provided in an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of the module structure of a control device for a grid-connected inverter provided in an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of the structure of a terminal provided in an embodiment of the present invention. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0053] Figure 1This is a flowchart illustrating a control method for a grid-connected inverter according to an embodiment of the present invention. This embodiment is applicable to improving the adaptability of a grid-connected inverter to grid voltage dips. The grid-connected inverter can be an inverter connected to the grid in a new energy power generation system, such as a grid-connected inverter in a photovoltaic power generation system or a wind power generation system. The method can be executed by a control device of the grid-connected inverter, which can be implemented in software and / or hardware. This device can be configured in an electronic device, such as a server or terminal device. Typical terminal devices include mobile terminals, specifically mobile phones, computers, or tablet computers. See also... Figure 1 The method specifically includes the following steps:

[0054] S110. Real-time acquisition of three-phase grid voltage sampling values ​​for each cycle, and conversion of three-phase grid voltage sampling values ​​for each cycle into grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0055] Specifically, the three-phase grid voltage sample value refers to the grid voltage sample value under the three-phase stationary symmetrical coordinate system. The three-phase grid voltage sample value of each cycle can be converted into the grid voltage sample value under the corresponding two-phase stationary coordinate system through the Clark transformation (3s / 2s transformation).

[0056] S120. Based on the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle, the change angle of the three-phase grid voltage space vector, and the preset numerical relationship, calculate the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle.

[0057] The preset numerical relationship is the numerical relationship between the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle and the grid voltage value in the two-phase stationary coordinate system of the previous cycle and the change angle of the three-phase grid voltage space vector.

[0058] Figure 2 This is a spatial vector diagram of a three-phase power grid voltage provided in an embodiment of the present invention. See also... Figure 2 The three-phase stationary symmetrical coordinate system includes the a-axis, b-axis, and c-axis, while the two-phase stationary coordinate system includes the α-axis and β-axis. For example, the three-phase grid voltage of the previous cycle includes Ua, Ub, and Uc (not shown in the figure). Ua, Ub, and Uc can be synthesized into the spatial vector U of the three-phase grid voltage. The angle of change of the three-phase grid voltage spatial vector refers to the angle of change of the three-phase grid voltage spatial vector in each control cycle. For example, the angle of change of the three-phase grid voltage spatial vector in each control cycle is B. Under normal circumstances, from the previous cycle to the current cycle, the three-phase grid voltage spatial vector moves from U to U1, where U1 is the spatial vector of the three-phase grid voltage in the current cycle. Therefore, based on the sampled value of the three-phase grid voltage in the previous cycle, the sampled value of the three-phase grid voltage in the current cycle can be predicted.

[0059] When the grid voltage is under normal conditions, the vector magnitude of the spatial vector U1 of the three-phase grid voltage in the current cycle is equal to that of the spatial vector U of the three-phase grid voltage in the previous cycle. Therefore, based on the numerical relationship between the vector magnitudes of the spatial vectors U1 and U of the three-phase grid voltage in the current cycle, the trigonometric relationship between the spatial vector U of the three-phase grid voltage in the previous cycle and its corresponding grid voltage value in the two-phase stationary coordinate system, and the trigonometric relationship between the spatial vector U1 of the three-phase grid voltage in the current cycle and its corresponding grid voltage value in the two-phase stationary coordinate system, we can derive the numerical relationship between the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle and the grid voltage value in the two-phase stationary coordinate system of the previous cycle and the angle of change of the three-phase grid voltage spatial vector. This is the preset numerical relationship. By substituting the sampled grid voltage value in the two-phase stationary coordinate system of the previous cycle and the angle of change of the three-phase grid voltage spatial vector into the preset numerical relationship, the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle can be calculated.

[0060] S130. Based on the numerical relationship between the absolute value of the difference between the grid voltage sample value and the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the preset voltage value, determine whether a grid voltage drop has occurred.

[0061] For example, see [link to previous article] Figure 2 If a voltage drop occurs in the current cycle, the spatial vector of the three-phase grid voltage in the current cycle will not be U1, but rather at the drop point, for example, U2. If the difference between the amplitudes of U1 and U2 is too large, it can be determined that a voltage drop has occurred. Therefore, if the absolute value of the difference between the sampled grid voltage value and the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle is greater than the preset voltage value, it indicates that the deviation between the sampled grid voltage value and the predicted grid voltage value of the current cycle is too large, and it can be determined that a voltage drop has occurred in the current cycle.

[0062] S140. Control the grid-connected inverter based on the judgment result.

[0063] If a grid voltage drop occurs, the sudden change in grid voltage will cause a sudden change in grid current. If the convergence speed of the grid-connected inverter's output current is too slow, there is a risk of instantaneous overcurrent. For example, if the determination is that a grid voltage drop has occurred in the current cycle, the grid-connected inverter can be controlled, such as by switching the control strategy of the grid-connected inverter, to control the current surge caused by the grid voltage drop.

[0064] The technical solution of this invention utilizes the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle to calculate the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle. Based on the deviation between the grid voltage sampling value and the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle, it determines whether a grid voltage drop has occurred. This achieves the determination of grid voltage drop within one control cycle, thereby improving the speed of grid voltage drop detection. In the prior art, it generally takes about 5ms from the time the grid voltage drops to the determination that the grid has entered a low-voltage state. Compared with the prior art, this solution can determine whether a grid voltage drop has occurred within one control cycle. When the duration of one control cycle is 100us, this solution can shorten the grid voltage drop detection time from 5ms to 100us. The technical solution of this invention, by controlling the grid-connected inverter based on the grid voltage drop determination result, also helps to quickly suppress the grid-connected inverter overcurrent caused by the grid voltage drop, thereby alleviating the grid voltage drop problem and avoiding overcurrent protection of the grid-connected inverter, thus improving the adaptability of the grid-connected inverter to grid voltage drops.

[0065] Based on the above embodiments, optionally, the two-phase stationary coordinate system includes an α coordinate axis and a β coordinate axis; the grid voltage sample value in the two-phase stationary coordinate system of the previous cycle includes the grid voltage sample value component on the α coordinate axis and the grid voltage sample value component on the β coordinate axis; the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle includes the grid voltage prediction value component on the α coordinate axis and the grid voltage prediction value component on the β coordinate axis; correspondingly, the preset numerical relationship includes a first numerical relationship between the grid voltage prediction value component on the α coordinate axis of the current cycle and the grid voltage sample value components on the α coordinate axis and the grid voltage sample value components on the β coordinate axis of the previous cycle and the change angle of the three-phase grid voltage space vector, and a second numerical relationship between the grid voltage prediction value component on the β coordinate axis of the current cycle and the grid voltage sample value components on the α coordinate axis and the grid voltage sample value components on the β coordinate axis of the previous cycle and the change angle of the three-phase grid voltage space vector.

[0066] Specifically, see Figure 2 Based on the numerical relationship between the vector magnitudes of the spatial vector U1 of the current cycle and the spatial vector U of the previous cycle, the trigonometric function relationship between the spatial vector U of the previous cycle and its corresponding grid voltage value in the two-phase stationary coordinate system, and the trigonometric function relationship between the spatial vector U1 of the current cycle and its corresponding grid voltage value in the two-phase stationary coordinate system, the first and second numerical relationships mentioned above can be derived.

[0067] Based on the above embodiments, optionally, the first numerical relationship is expressed as:

[0068] U1α=Ualpha*cosB-Ubeta*sinB; (1)

[0069] The second numerical relationship is expressed as follows:

[0070] U1β=Ualpha*sinB+Ubeta*cosB; (2)

[0071] Wherein, U1α is the grid voltage prediction component on the α-axis of the current period, U1β is the grid voltage prediction component on the β-axis of the current period, Ualpha is the grid voltage sampled component on the α-axis of the previous period, Ubeta is the grid voltage sampled component on the β-axis of the previous period, and B is the angle of change of the three-phase grid voltage space vector.

[0072] For example, see Figure 2 When the grid voltage is in a normal state, the space vector U1 of the three-phase grid voltage (predicted value) in the current cycle has the same vector magnitude as the space vector U of the three-phase grid voltage (sampled value) in the previous cycle. Therefore:

[0073] U1cos(A+B)=Ucos(A+B);

[0074] U1sin(A+B)=Usin(A+B);

[0075] Ucos(A+B)=UcosAcosB-UsinAsinB=Ualpha*cosB-Ubeta*sinB;

[0076] Usin(A+B)=UsinAcosB+UcosAsinB=Ualpha*sinB+Ubeta*cosB;

[0077] Where A represents the angle between the space vector U and the a-axis, and Ualpha and Ubeta are the components of the space vector U of the three-phase grid voltage (sampled value) in the previous cycle in the two-phase stationary coordinate system. Figure 2 Ualpha and Ubeta are not specifically shown in the text.

[0078] Ucos(A+B)=U1cos(A+B)=U1α=Ualpha*cosB-Ubeta*sinB;

[0079] Usin(A+B)=U1sin(A+B)=U1β=Ualpha*sinB+Ubeta*cosB;

[0080] Where U1α and U1β are the components of the space vector U1 of the three-phase grid voltage (predicted value) in the current cycle in the two-phase stationary coordinate system. Figure 2 U1α and U1β are not specifically shown. Through the above derivation process, the first and second numerical relationships can be obtained.

[0081] Optionally, step S120 specifically includes: calculating the grid voltage prediction value component on the α coordinate axis of the current period based on the grid voltage sample value component on the β coordinate axis, the change angle of the three-phase grid voltage space vector, and the first numerical relationship of the grid voltage sample value component on the α coordinate axis of the previous period.

[0082] Based on the grid voltage sampled value components on the α-axis and β-axis of the previous period, the change angle of the three-phase grid voltage space vector, and the second numerical relationship, calculate the grid voltage predicted value components on the β-axis of the current period.

[0083] For example, by substituting the grid voltage sample value component Ualpha on the α coordinate axis, the grid voltage sample value component Ubeta on the β coordinate axis, and the change angle B of the three-phase grid voltage space vector in the previous cycle into equations (1) and (2) for calculation, the grid voltage prediction value component U1α on the α coordinate axis in the current cycle and the grid voltage prediction value component U1β on the β coordinate axis in the current cycle can be obtained.

[0084] Optionally, the grid voltage sample value in the two-phase stationary coordinate system of the current cycle includes the grid voltage sample value component on the α coordinate axis and the grid voltage sample value component on the β coordinate axis; the preset voltage value includes a first preset voltage value and a second preset voltage value; correspondingly, step S130 specifically includes:

[0085] If the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the α axis of the current period is greater than the first preset voltage value, and / or the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the β axis of the current period is greater than the second preset voltage value, then a grid voltage drop is determined to have occurred.

[0086] The values ​​of the first and second preset voltages can be set according to requirements. For example, the first preset voltage can be set to 0.1Uαmax and the second preset voltage can be set to 0.1Uβmax. Uαmax represents the maximum value of the grid voltage component on the α-axis when the grid voltage is at the rated voltage, and Uβmax represents the maximum value of the grid voltage component on the β-axis when the grid voltage is at the rated voltage.

[0087] For example, the grid voltage sample value component on the α coordinate axis of the current period is denoted as Uα, and the grid voltage sample value component on the β coordinate axis is denoted as Uβ;

[0088] |Uα-U1α|>0.1Uαmax; (3)

[0089] |Uβ-U1β|>0.1Uβmax; (4)

[0090] If at least one of equations (3) and (4) is satisfied, it can be determined that a voltage drop has occurred in the current cycle.

[0091] Based on the above embodiments, optionally, the control method of the grid-connected inverter further includes: if the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the α coordinate axis of the next cycle is less than or equal to a third preset voltage value, and the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the β coordinate axis of the next cycle is less than or equal to a fourth preset voltage value, then it is determined that the grid voltage has returned to normal.

[0092] The values ​​of the third and fourth preset voltages can be set as needed. For example, the third preset voltage can be set to 0.08Uαmax and the fourth preset voltage can be set to 0.08Uβmax.

[0093] |Uα-U1α|≤0.08Uαmax; (5)

[0094] |Uβ-U1β|≤0.08Uβmax; (6)

[0095] If both equations (5) and (6) are satisfied, it can be determined that the grid voltage has returned to normal.

[0096] Optionally, step S140 specifically includes: if a grid voltage drop occurs, controlling the output current of the grid-connected inverter using a deadbeat current prediction control method.

[0097] The deadbeat current prediction control method includes: based on the numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage and inductance value of the current cycle, adjusting the output current of the grid-connected inverter in the next cycle to the required value by controlling the output voltage of the grid-connected inverter.

[0098] Specifically, since the rate of change of the output current of the grid-connected inverter is equal to the voltage drop across the inductor, the numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage, and inductance value of the grid-connected inverter can be deduced. If a grid voltage drop occurs, the output voltage of the grid-connected inverter can be adjusted to regulate the output current of the grid-connected inverter in the next cycle to the required value, thereby pulling the grid current back to a safe range.

[0099] In existing technologies, when grid voltage dips occur, a dual-dq decomposition control method is typically used. However, this method requires iterative filtering, making it difficult to quickly control the sudden current surge caused by the voltage dip, leading to overcurrent protection in the grid-connected inverter. Compared to existing technologies, this solution determines whether a grid voltage dip has occurred within one control cycle. It uses a deadbeat current prediction control method to control the inverter's output current, bringing the grid current back to a safe range within another control cycle. If the control frequency is 9.6kHz, the entire process takes only two cycles, or 200µs. This solution helps to quickly suppress overcurrent in the grid-connected inverter caused by grid voltage dips, thus mitigating the voltage dip problem and preventing overcurrent protection in the inverter, thereby improving the inverter's adaptability to grid voltage dips.

[0100] Based on the above embodiments, optionally, the output current of the grid-connected inverter includes the output current component Iα on the α coordinate axis and the output current component Iβ on the β coordinate axis; the output voltage of the grid-connected inverter includes the output voltage component on the α coordinate axis and the output voltage component on the β coordinate axis; the grid voltage includes the grid voltage component on the α coordinate axis and the grid voltage component on the β coordinate axis.

[0101] Accordingly, the numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage, and inductance value of the grid-connected inverter in the current cycle is expressed as follows:

[0102] Iα(n+1)=Iα(n)+Ts*(U'α-Eα) / Ls;

[0103] Iβ(n+1)=Iβ(n)+Ts*(U'β-Eβ) / Ls;

[0104] Where Iα(n+1) is the expected output current component on the α-axis of the next cycle, Iβ(n+1) is the expected output current component on the β-axis of the next cycle, Iα(n) is the output current component on the α-axis of the current cycle, Iβ(n) is the output current component on the β-axis of the current cycle, Ts is the cycle duration, U'α is the output voltage component on the α-axis of the current cycle, U'β is the output voltage component on the β-axis of the current cycle, Eα is the grid voltage component on the α-axis of the current cycle, Eβ is the grid voltage component on the β-axis of the current cycle, and Ls is the inductance value of the grid-connected inverter.

[0105] For example, in a two-phase stationary coordinate system formed by the α and β axes, the output current of a grid-connected inverter is controlled using a deadbeat current prediction control method. Since the rate of change of the output current of the grid-connected inverter is equal to the voltage drop across the inductor, it can be concluded that:

[0106] dIα / dt=(U'α-Eα) / Ls;

[0107] dIβ / dt=(U'β-Eβ) / Ls;

[0108] Therefore, we can deduce that:

[0109] Iα(n+1)=Iα(n)+Ts*(U'α-Eα) / Ls;

[0110] Iβ(n+1)=Iβ(n)+Ts*(U'β-Eβ) / Ls;

[0111] Therefore, if a grid voltage drop occurs, the output current of the grid-connected inverter is controlled using a deadbeat current prediction control method. The setpoint of the output current of the grid-connected inverter is set to 0. By adjusting the output voltage component U'α on the α axis and the output voltage component U'β on the β axis of the current cycle of the grid-connected inverter, the output current of the grid-connected inverter in the next cycle can be adjusted to the required value, thereby pulling the grid current back to the safe zone.

[0112] Optionally, step S140 may further include: if the output current component of the grid-connected inverter on the α coordinate axis is greater than or equal to a first set value, and / or the output current component of the grid-connected inverter on the β coordinate axis is greater than or equal to a second set value, then the output current of the grid-connected inverter is controlled by a deadbeat current prediction control method.

[0113] For example, during the period from the occurrence of a grid voltage drop to the return of the grid voltage to normal, the sudden change in grid voltage will also cause a sudden change in current. Therefore, during this process, it is also necessary to use a deadbeat current prediction control method to control the output current of the grid-connected inverter. By adjusting the output voltage of the grid-connected inverter, the output current of the grid-connected inverter in the next cycle will be adjusted to the required value, thereby pulling the grid current back to the safe zone.

[0114] The values ​​of the first and second settings can be set as needed. For example, the first setting can be set to 0.1Iαmax and the second setting can be set to 0.1Iβmax. Iαmax represents the maximum value of the output current component on the α axis when the output current of the grid-connected inverter is the rated current, and Iβmax represents the maximum value of the output current component on the β axis when the output current of the grid-connected inverter is the rated current.

[0115] |Iα|≥0.1Iαmax; (7)

[0116] |Iβ|≥0.1Iβmax; (8)

[0117] If at least one of equations (7) and (8) is satisfied, it can be determined that the current grid-connected current is in a sudden change state. The output current of the grid-connected inverter needs to be controlled by the deadbeat current prediction control method, so as to pull the grid current back to the safe zone.

[0118] Based on the above embodiments, step S140 may optionally include: if the output current component of the grid-connected inverter on the α coordinate axis is less than a first set value and the output current component of the grid-connected inverter on the β coordinate axis is less than a second set value, then the output current of the grid-connected inverter is controlled by the dual dq control method.

[0119] |Iα|<0.1Iαmax; (9)

[0120] |Iβ|<0.1Iβmax; (10)

[0121] For example, let's take the first setpoint set to 0.1Iαmax and the second setpoint set to 0.1Iβmax as an example. If both equations (9) and (10) are satisfied, it means that the current grid-connected current is controlled within 0.1 times the maximum current range. In this case, there is no need to use the deadbeat current prediction control method. The output current of the grid-connected inverter can be controlled by the dual dq control method. That is, the grid voltage is decomposed into dual dq components to obtain the positive and negative sequence components of the grid voltage. These components are then iteratively filtered, and the positive and negative sequence phases of the grid-connected current are determined according to the positive and negative sequence phases of the grid voltage. After iterative filtering, the output current of the grid-connected inverter is controlled, thereby achieving the decoupling of the positive and negative sequence components of the grid current. The dual dq control method has the advantage of strong robustness. Using this control method to control the output current of the grid-connected inverter helps to improve the stability of grid operation.

[0122] Based on the above embodiments, this embodiment further optimizes the control method of the grid-connected inverter. Figure 3 This is a flowchart illustrating another control method for a grid-connected inverter provided in an embodiment of the present invention. See also... Figure 3 The method specifically includes the following steps:

[0123] S210. Real-time acquisition of three-phase grid voltage sampling values ​​for each cycle, and conversion of three-phase grid voltage sampling values ​​for each cycle into grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0124] S220. Based on the grid voltage sampled value components on the α-axis and β-axis of the previous cycle, the change angle of the three-phase grid voltage space vector, and the preset numerical relationship, calculate the grid voltage predicted value components on the α-axis and β-axis of the current cycle.

[0125] The preset numerical relationship includes a first numerical relationship and a second numerical relationship. The first numerical relationship can be referred to in equation (1) of the above embodiment, and the second numerical relationship can be referred to in equation (2) of the above embodiment.

[0126] S230. Determine whether the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the α coordinate axis of the current period is less than or equal to the first preset voltage value, and whether the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the β coordinate axis of the current period is less than or equal to the second preset voltage value.

[0127] If the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the α coordinate axis of the current period is less than or equal to the first preset voltage value, and the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the β coordinate axis of the current period is less than or equal to the second preset voltage value, then proceed to step S230; if the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the α coordinate axis of the current period is greater than the first preset voltage value, and / or, the absolute value of the difference between the grid voltage sample value component and the grid voltage prediction value component on the β coordinate axis of the current period is greater than the second preset voltage value, then proceed to step S240.

[0128] S240, It is determined that a voltage drop in the power grid has occurred.

[0129] S250. Switch the control mode of the grid-connected inverter to the deadbeat current prediction control method, and set the setpoint of the grid-connected inverter output current to 0, so as to adjust the output current of the grid-connected inverter to the required value in the next cycle by controlling the output voltage of the grid-connected inverter.

[0130] Specifically, the deadbeat current prediction control method includes: based on the numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage, and inductance value of the current cycle, adjusting the output current of the grid-connected inverter to the required value in the next cycle by controlling the output voltage of the grid-connected inverter. The numerical relationship between the expected output current of the grid-connected inverter in the next cycle and the output current, cycle duration, output voltage, grid voltage, and inductance value of the current cycle is expressed as follows:

[0131] Iα(n+1)=Iα(n)+Ts*(U'α-Eα) / Ls;

[0132] Iβ(n+1)=Iβ(n)+Ts*(U'β-Eβ) / Ls;

[0133] If a grid voltage drop occurs, the output current of the grid-connected inverter is controlled using a deadbeat current prediction control method. The setpoint of the output current of the grid-connected inverter is set to 0. By adjusting the output voltage component U'α on the α axis and the output voltage component U'β on the β axis of the current cycle of the grid-connected inverter, the output current of the grid-connected inverter in the next cycle can be adjusted to the required value, thereby pulling the grid current back to the safe zone.

[0134] S260. Determine whether the output current component of the grid-connected inverter on the α coordinate axis is less than the first set value, and whether the output current component of the grid-connected inverter on the β coordinate axis is less than the second set value.

[0135] If the output current component of the grid-connected inverter on the α coordinate axis is less than the first set value, and the output current component of the grid-connected inverter on the β coordinate axis is less than the second set value, then proceed to step S270; if the output current component of the grid-connected inverter on the α coordinate axis is greater than or equal to the first set value, and / or the output current component of the grid-connected inverter on the β coordinate axis is greater than or equal to the second set value, then return to proceed to step S250.

[0136] S270, Switch the control mode of the grid-connected inverter to the dual dq control method.

[0137] The technical solution of this invention utilizes the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle to calculate the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle. Based on the deviation between the grid voltage sampling value and the predicted grid voltage value in the two-phase stationary coordinate system of the current cycle, it determines whether a grid voltage dip has occurred. This enables the determination of whether a grid voltage dip has occurred within one control cycle, thereby improving the speed of grid voltage dip detection. If a grid voltage dip occurs, a deadbeat current prediction control method is used to control the output current of the grid-connected inverter. This pulls the grid current back to the safe zone within one control cycle, helping to quickly suppress overcurrent in the grid-connected inverter caused by grid voltage dips, thereby mitigating the grid voltage dip problem and avoiding overcurrent protection of the grid-connected inverter, thus improving the adaptability of the grid-connected inverter to grid voltage dips.

[0138] This invention also provides a control device for a grid-connected inverter. Figure 4 This is a schematic diagram of the module structure of a control device for a grid-connected inverter according to an embodiment of the present invention. The control device for the grid-connected inverter provided in this embodiment of the present invention can execute the control method for the grid-connected inverter provided in any embodiment of the present invention. See also... Figure 4 The control device of the grid-connected inverter specifically includes: a grid voltage sampling value acquisition module 310, a grid voltage prediction value calculation module 320, a judgment module 330, and a control module 340.

[0139] The grid voltage sampling value acquisition module 310 is used to acquire the three-phase grid voltage sampling values ​​of each cycle in real time, and convert the three-phase grid voltage sampling values ​​of each cycle into grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0140] The grid voltage prediction calculation module 320 is used to calculate the grid voltage prediction value in the two-phase stationary coordinate system of the current period based on the grid voltage sampling value in the two-phase stationary coordinate system of the previous period, the change angle of the three-phase grid voltage space vector, and the preset numerical relationship; wherein, the preset numerical relationship is the numerical relationship between the grid voltage prediction value in the two-phase stationary coordinate system of the current period and the grid voltage value in the two-phase stationary coordinate system of the previous period and the change angle of the three-phase grid voltage space vector.

[0141] The judgment module 330 is used to determine whether a voltage drop has occurred based on the numerical relationship between the absolute value of the difference between the sampled value and the predicted value of the grid voltage in the two-phase stationary coordinate system of the current cycle and the preset voltage value.

[0142] The control module 340 is used to control the grid-connected inverter based on the judgment result.

[0143] The control device for the grid-connected inverter provided in the embodiments of the present invention can execute the control method for the grid-connected inverter provided in any embodiment of the present invention, and thus has the corresponding functional modules and beneficial effects of the method, which will not be elaborated further.

[0144] Figure 5 This is a schematic diagram of the structure of a terminal provided in an embodiment of the present invention. Figure 5 A block diagram of an exemplary device 410 suitable for implementing embodiments of the present invention is shown. Figure 5 The device 410 shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of the present invention.

[0145] like Figure 5 As shown, device 410 is presented in the form of a general-purpose device. Components of device 410 may include, but are not limited to: one or more processors 414, storage device 426, and bus 416 connecting different system components (including storage device 426 and processor 414).

[0146] Bus 416 represents one or more of several bus architectures, including a memory device bus or memory device controller, a peripheral bus, a graphics acceleration port, a processor, or a local bus using any of the various bus architectures. Examples of these architectures include, but are not limited to, the Industry Subversive Alliance (ISA) bus, the Micro Channel Architecture (MAC) bus, the Enhanced ISA bus, the Video Electronics Standards Association (VESA) local bus, and the Peripheral Component Interconnect (PCI) bus.

[0147] Device 410 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by device 410, including volatile and non-volatile media, removable and non-removable media.

[0148] Storage device 426 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 430 and / or cache memory 432. Device 410 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, storage system 434 may be used to read and write non-removable, non-volatile magnetic media (…). Figure 5 Not shown; usually referred to as a "hard drive"). Although Figure 5 Not shown, a disk drive for reading and writing to a removable non-volatile disk (e.g., a "floppy disk") and an optical disc drive for reading and writing to a removable non-volatile optical disc, such as a Compact Disc Read-Only Memory (CD-ROM), a Digital Video Disc Read-Only Memory (DVD-ROM), or other optical media may be provided. In these cases, each drive may be connected to bus 416 via one or more data media interfaces. Storage device 426 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of the present invention.

[0149] A program / utility 440 having a set (at least one) of program modules 442 may be stored in, for example, a storage device 426. Such program modules 442 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data. Each or some combination of these examples may include an implementation of a network environment. Program modules 442 typically perform the functions and / or methods described in the embodiments of the present invention.

[0150] Device 410 can also communicate with one or more external devices 412 (e.g., keyboard, pointing terminal, display 424, etc.), and with one or more terminals that enable a user to interact with device 410, and / or with any terminal that enables device 410 to communicate with one or more other computing terminals (e.g., network card, modem, etc.). This communication can be performed via input / output (I / O) interface 422. Furthermore, device 410 can also communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public networks, such as the Internet) via network adapter 420. Figure 5 As shown, network adapter 420 communicates with other modules of device 410 via bus 416. It should be understood that, although not shown in the figure, other hardware and / or software modules can be used in conjunction with device 410, including but not limited to: microcode, terminal drivers, redundant processors, external disk drive arrays, Redundant Arrays of Independent Disks (RAID) systems, tape drives, and data backup storage systems.

[0151] Processor 414 executes various functional applications and data processing by running programs stored in storage device 426, such as implementing the grid-connected inverter control method provided in this embodiment of the invention, the method including:

[0152] The three-phase grid voltage sampling values ​​for each cycle are acquired in real time, and the three-phase grid voltage sampling values ​​for each cycle are converted into grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0153] Based on the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle, the change angle of the three-phase grid voltage space vector, and the preset numerical relationship, calculate the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle; wherein, the preset numerical relationship is the numerical relationship between the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the grid voltage value in the two-phase stationary coordinate system of the previous cycle and the change angle of the three-phase grid voltage space vector.

[0154] Based on the numerical relationship between the absolute value of the difference between the grid voltage sample value and the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the preset voltage value, it is determined whether a grid voltage drop has occurred.

[0155] The grid-connected inverter is controlled based on the judgment result.

[0156] This invention also provides a computer-readable storage medium storing a computer program thereon. When executed by a processor, the program implements the control method for a grid-connected inverter as provided in this invention, the method comprising:

[0157] The three-phase grid voltage sampling values ​​for each cycle are acquired in real time, and the three-phase grid voltage sampling values ​​for each cycle are converted into grid voltage sampling values ​​in a two-phase stationary coordinate system.

[0158] Based on the grid voltage sampling value in the two-phase stationary coordinate system of the previous cycle, the change angle of the three-phase grid voltage space vector, and the preset numerical relationship, calculate the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle; wherein, the preset numerical relationship is the numerical relationship between the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the grid voltage value in the two-phase stationary coordinate system of the previous cycle and the change angle of the three-phase grid voltage space vector.

[0159] Based on the numerical relationship between the absolute value of the difference between the grid voltage sample value and the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the preset voltage value, it is determined whether a grid voltage drop has occurred.

[0160] The grid-connected inverter is controlled based on the judgment result.

[0161] The computer storage medium of this invention can be any combination of one or more computer-readable media. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. For example, a computer-readable storage medium can be, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this document, a computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0162] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media may also be any computer-readable medium other than computer-readable storage media, capable of sending, propagating, or transmitting programs for use by or in connection with an instruction execution system, apparatus, or device.

[0163] Program code contained on a computer-readable medium may be transmitted using any suitable medium, including but not limited to wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0164] Computer program code for performing the operations of this invention can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or terminal. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0165] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A control method of a grid-connected inverter, characterized by, The method comprises the following steps: real-time acquisition of three-phase grid voltage sample values of each cycle, and conversion of the three-phase grid voltage sample values of each cycle into grid voltage sample values in a two-phase stationary coordinate system; calculation of a grid voltage prediction value in the two-phase stationary coordinate system of the current cycle according to a grid voltage sample value in the two-phase stationary coordinate system of the previous cycle, a change angle of a three-phase grid voltage space vector, and a preset numerical relationship; wherein the preset numerical relationship is a numerical relationship between the grid voltage prediction value in the two-phase stationary coordinate system of the current cycle and the grid voltage sample value in the two-phase stationary coordinate system of the previous cycle and the change angle of the three-phase grid voltage space vector; determination of whether a grid voltage drop occurs according to a numerical relationship between an absolute value of a difference between the grid voltage sample value in the two-phase stationary coordinate system of the current cycle and the grid voltage prediction value and a preset voltage value; control of a grid-connected inverter according to the determination result; if the grid voltage drop occurs, control of an output current of the grid-connected inverter by a deadbeat current prediction control method, the deadbeat current prediction control method comprising: adjustment of the output current of the grid-connected inverter to a required value in the next cycle of the grid-connected inverter by control of an output voltage of the grid-connected inverter according to a numerical relationship between an output current expected value of the grid-connected inverter in the next cycle and an output current in the current cycle, a cycle time length, an output voltage, a grid voltage, and an inductance value of the grid-connected inverter; the output current of the grid-connected inverter comprises an output current component on an α coordinate axis and an output current component on a β coordinate axis, the output voltage of the grid-connected inverter comprises an output voltage component on the α coordinate axis and an output voltage component on the β coordinate axis, and the grid voltage comprises a grid voltage component on the α coordinate axis and a grid voltage component on the β coordinate axis; the numerical relationship between the output current expected value of the grid-connected inverter in the next cycle and the output current in the current cycle, the cycle time length, the output voltage, the grid voltage, and the inductance value of the grid-connected inverter is expressed as: Iα(n+1) = Iα(n) + Ts*(U'α - Eα) / Ls; Iβ(n+1) = Iβ(n) + Ts*(U'β - Eβ) / Ls; wherein Iα(n+1) is the output current expected value component on the α coordinate axis in the next cycle, Iβ(n+1) is the output current expected value component on the β coordinate axis in the next cycle, Iα(n) is the output current component on the α coordinate axis in the current cycle, Iβ(n) is the output current component on the β coordinate axis in the current cycle, Ts is the cycle time length, U'α is the output voltage component on the α coordinate axis in the current cycle, U'β is the output voltage component on the β coordinate axis in the current cycle, Eα is the grid voltage component on the α coordinate axis in the current cycle, Eβ is the grid voltage component on the β coordinate axis in the current cycle, and Ls is the inductance value of the grid-connected inverter.

2. The control method of the grid-connected inverter according to claim 1, characterized by, The two-phase stationary coordinate system comprises an alpha coordinate axis and a beta coordinate axis; the grid voltage sample value in the two-phase stationary coordinate system of the previous period comprises a grid voltage sample value component on the alpha coordinate axis and a grid voltage sample value component on the beta coordinate axis; the grid voltage prediction value in the two-phase stationary coordinate system of the current period comprises a grid voltage prediction value component on the alpha coordinate axis and a grid voltage prediction value component on the beta coordinate axis; The preset numerical relationship comprises a first numerical relationship between the grid voltage prediction value component on the alpha coordinate axis of the current period, the grid voltage sample value component on the alpha coordinate axis of the previous period, the grid voltage sample value component on the beta coordinate axis of the previous period and the change angle of the three-phase grid voltage space vector, and a second numerical relationship between the grid voltage prediction value component on the beta coordinate axis of the current period, the grid voltage sample value component on the alpha coordinate axis of the previous period, the grid voltage sample value component on the beta coordinate axis of the previous period and the change angle of the three-phase grid voltage space vector; According to the grid voltage sample value in the two-phase stationary coordinate system of the previous period, the change angle of the space vector synthesized by the three-phase grid voltage in each period and the preset numerical relationship, the grid voltage prediction value in the two-phase stationary coordinate system of the current period is calculated, comprising: According to the grid voltage sample value component on the alpha coordinate axis of the previous period, the grid voltage sample value component on the beta coordinate axis of the previous period, the change angle of the three-phase grid voltage space vector and the first numerical relationship, the grid voltage prediction value component on the alpha coordinate axis of the current period is calculated; According to the grid voltage sample value component on the alpha coordinate axis of the previous period, the grid voltage sample value component on the beta coordinate axis of the previous period, the change angle of the three-phase grid voltage space vector and the second numerical relationship, the grid voltage prediction value component on the beta coordinate axis of the current period is calculated.

3. The control method of the grid-connected inverter according to claim 2, characterized by, The first numerical relationship is expressed as: U1α=Ualpha*cosB-Ubeta*sinB; The second numerical relationship is expressed as: U1β=Ualpha*sinB+Ubeta*cosB; Wherein, U1α is the grid voltage prediction value component on the alpha coordinate axis of the current period, U1β is the grid voltage prediction value component on the beta coordinate axis of the current period, Ualpha is the grid voltage sample value component on the alpha coordinate axis of the previous period, Ubeta is the grid voltage sample value component on the beta coordinate axis of the previous period, and B is the change angle of the three-phase grid voltage space vector.

4. The control method of the grid-connected inverter according to claim 1, characterized by, The grid voltage sample value in the two-phase stationary coordinate system of the current period comprises a grid voltage sample value component on the alpha coordinate axis and a grid voltage sample value component on the beta coordinate axis; the preset voltage value comprises a first preset voltage value and a second preset voltage value; According to the numerical relationship between the absolute value of the difference between the grid voltage sample value and the grid voltage prediction value in the two-phase stationary coordinate system of the current period and the preset voltage value, whether the grid voltage drop occurs is determined, comprising: If the absolute value of the difference between the grid voltage sample value component on the a coordinate axis of the current period and the grid voltage prediction value component is greater than the first preset voltage value, and / or the absolute value of the difference between the grid voltage sample value component on the β coordinate axis of the current period and the grid voltage prediction value component is greater than the second preset voltage value, it is determined that the grid voltage sag occurs.

5. The control method of the grid-connected inverter according to claim 4, characterized by, Also includes: If the absolute value of the difference between the grid voltage sample value component on the a coordinate axis of the next period and the grid voltage prediction value component is less than or equal to the third preset voltage value, and the absolute value of the difference between the grid voltage sample value component on the β coordinate axis of the next period and the grid voltage prediction value component is less than or equal to the fourth preset voltage value, it is determined that the grid voltage returns to normal.

6. The control method of the grid-connected inverter according to claim 1, characterized by, According to the judgment result, the grid-connected inverter is controlled, and further includes: If the output current component of the grid-connected inverter on the a coordinate axis is greater than or equal to the first set value, and / or the output current component of the grid-connected inverter on the β coordinate axis is greater than or equal to the second set value, the output current of the grid-connected inverter is controlled by the dead-beat current prediction control method.

7. The control method of the grid-connected inverter according to claim 6, characterized by, According to the judgment result, the grid-connected inverter is controlled, and further includes: If the output current component of the grid-connected inverter on the a coordinate axis is less than the first set value, and the output current component of the grid-connected inverter on the β coordinate axis is less than the second set value, the output current of the grid-connected inverter is controlled by the double-dq control method.

8. A control device of a grid-connected inverter, characterized by comprising: Including: A grid voltage sample value acquisition module is configured to acquire three-phase grid voltage sample values of each period in real time, and convert the three-phase grid voltage sample values of each period into grid voltage sample values in a two-phase static coordinate system; A grid voltage prediction value calculation module is configured to calculate grid voltage prediction values in a two-phase static coordinate system of a current period according to grid voltage sample values in a two-phase static coordinate system of a previous period, a change angle of a three-phase grid voltage space vector, and a preset numerical relationship; wherein the preset numerical relationship is a numerical relationship between the grid voltage prediction values in the two-phase static coordinate system of the current period and the grid voltage values in the two-phase static coordinate system of the previous period and the change angle of the three-phase grid voltage space vector; A judgment module is configured to determine whether a grid voltage sag occurs according to a numerical relationship between the absolute value of the difference between the grid voltage sample values in the two-phase static coordinate system of the current period and the grid voltage prediction values and preset voltage values; A control module is configured to control a grid-connected inverter according to a judgment result, and if a grid voltage sag occurs, control the output current of the grid-connected inverter by a dead-beat current prediction control method, which includes adjusting the output current of the grid-connected inverter to a required value by controlling the output voltage of the grid-connected inverter according to a numerical relationship between the output current expected value of the grid-connected inverter in the next period, the output current of the current period, the period length, the output voltage, the grid voltage, and the inductance value of the grid-connected inverter.

9. An electronic device, comprising: The electronic device includes: One or more processors; A storage device configured to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement a control method of a grid-connected inverter as claimed in any one of claims 1-7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program, when executed by a processor, implements a control method of a grid-connected inverter as claimed in any one of claims 1-7.

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