Pre-synchronization grid connection method and device based on virtual synchronization control, terminal equipment and storage medium

Abstract

The invention discloses a pre-synchronization grid connection method and device based on virtual synchronization control, terminal equipment and a storage medium, and the method comprises the steps: repeatedly executing a pre-synchronization operation when a state identifier corresponding to an additional frequency maintaining signal is a first identifier until a voltage q-axis component deviation is smaller than a preset threshold value, and at the moment, converting a state identifier corresponding to the additional frequency holding signal into a second identifier, stopping the pre-synchronization operation, and merging the power electronic interface power supply controlled by the virtual synchronous machine into the power grid system. Therefore, by implementing the method, large impact current can be prevented from occurring in the switching-on grid-connected process, and safe and stable operation of the power electronic interface power supply and the power grid is effectively ensured.

Description

Technical Field

[0001] The present invention relates to the field of power electronic interface power supply grid connection, and in particular to a pre-synchronization grid connection method, device, terminal equipment and storage medium based on virtual synchronization control. Background Art

[0002] At present, with the increasing proportion of power electronic interface power supplies in power systems, higher requirements are put forward for the reliable grid connection and reliable operation of power electronic interface power supplies. Due to the voltage source control characteristics of power electronic interface power supplies that use virtual synchronous control, if they are not reasonably pre-synchronized, they will cause a large current shock when connected to the grid, endangering the safe and stable operation of the power electronic interface power supply and the power grid. Summary of the invention

[0003] The present invention provides a pre-synchronization grid-connected method, device, terminal equipment and storage medium based on virtual synchronization control. The method adjusts the state mark of the additional frequency holding signal according to the size of the voltage q-axis component deviation. On this basis, the state mark of the additional frequency holding signal is used to determine whether to perform a pre-synchronization operation or a grid-connected operation, thereby avoiding large impact currents in the process of closing and connecting to the grid, thereby ensuring the safe and stable operation of the power electronic interface power supply and the power grid.

[0004] An embodiment of the present invention provides a pre-synchronization grid-connection method based on virtual synchronization control, comprising:

[0005] After receiving the grid connection instruction, the state flag corresponding to the additional frequency holding signal is set to the first flag; wherein the additional frequency holding signal is used to indicate the pre-synchronization operation state;

[0006] When the state identifier corresponding to the additional frequency holding signal is a first identifier, repeatedly performing a pre-synchronization operation until the state identifier corresponding to the additional frequency holding signal changes to a second identifier, and stopping the pre-synchronization operation;

[0007] When the state identifier corresponding to the additional frequency maintaining signal is a second identifier, the power electronic interface power supply controlled by the virtual synchronous machine is incorporated into the power grid system;

[0008] The pre-synchronization operation includes:

[0009] Collect the current grid-side voltage of the converter and the current machine-end voltage of the converter;

[0010] Calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage, and determining whether the voltage q-axis component deviation is less than a preset threshold value,

[0011] If yes, setting the state flag corresponding to the additional frequency holding signal to the second flag;

[0012] If not, a corresponding additional frequency component is generated according to the voltage q-axis component deviation, and the additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0013] Further, the generating of a corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes:

[0014] Inputting the voltage q-axis component deviation into a preset PI controller, so that the PI controller outputs a corresponding additional frequency component according to the voltage q-axis component deviation;

[0015] The additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0016] Further, the calculating of the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage includes:

[0017] Performing Park transformation on the grid-side voltage to obtain a first voltage q-axis component of the grid-side voltage;

[0018] Performing Park transformation on the machine-end voltage to obtain a second voltage q-axis component of the machine-end voltage;

[0019] The voltage q-axis component deviation is obtained by subtracting the first voltage q-axis component from the second voltage q-axis component.

[0020] Furthermore, the adding the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes:

[0021] The updated second control structure of the virtual synchronous machine is calculated by the following formula:

[0022]

[0023] In the formula, u qgrid is the first voltage q-axis component; u qvsc is the second voltage q-axis component; k p is the proportional coefficient of the PI controller; k i is the integral coefficient of the PI controller; s is the Laplace operator; P * is the active power reference value; P is the active power measured at the grid-connected point of the converter; D is the virtual synchronous droop coefficient; TJ is the virtual synchronous inertia time constant; ω0 is the reference angular frequency; ω * is the updated virtual synchronous angular frequency reference value.

[0024] An embodiment of the present invention further provides a pre-synchronization grid-connected device based on virtual synchronization control, comprising: an additional frequency maintenance signal initialization module, a pre-synchronization operation execution module and a grid-connected module;

[0025] The additional frequency holding signal initialization module is used to set the state identifier corresponding to the additional frequency holding signal to the first identifier after receiving the grid connection instruction; wherein the additional frequency holding signal is used to indicate the pre-synchronization operation state;

[0026] The pre-synchronization operation execution module is used to repeatedly execute the pre-synchronization operation when the state identifier corresponding to the additional frequency holding signal is the first identifier, until the state identifier corresponding to the additional frequency holding signal changes to the second identifier, and stop the pre-synchronization operation;

[0027] The grid-connected module is used to connect the power electronic interface power supply controlled by the virtual synchronous machine into the power grid system when the state identifier corresponding to the additional frequency holding signal is the second identifier;

[0028] The pre-synchronization operation includes:

[0029] Collect the current grid-side voltage of the converter and the current machine-end voltage of the converter;

[0030] Calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage, and determining whether the voltage q-axis component deviation is less than a preset threshold value,

[0031] If yes, setting the state flag corresponding to the additional frequency holding signal to the second flag;

[0032] If not, a corresponding additional frequency component is generated according to the voltage q-axis component deviation, and the additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0033] Further, the generating of a corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes:

[0034] Inputting the voltage q-axis component deviation into a preset PI controller, so that the PI controller outputs a corresponding additional frequency component according to the voltage q-axis component deviation;

[0035] The additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0036] Further, the calculating of the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage includes:

[0037] Performing Park transformation on the grid-side voltage to obtain a first voltage q-axis component of the grid-side voltage;

[0038] Performing Park transformation on the machine-end voltage to obtain a second voltage q-axis component of the machine-end voltage;

[0039] The voltage q-axis component deviation is obtained by subtracting the first voltage q-axis component from the second voltage q-axis component.

[0040] Furthermore, the adding the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes:

[0041] The updated second control structure of the virtual synchronous machine is calculated by the following formula:

[0042]

[0043] In the formula, u qgrid is the first voltage q-axis component; u qvsc is the second voltage q-axis component; k p is the proportional coefficient of the PI controller; k i is the integral coefficient of the PI controller; s is the Laplace operator; P * is the active power reference value; P is the active power measured at the grid-connected point of the converter; D is the virtual synchronous droop coefficient; T J is the virtual synchronous inertia time constant; ω0 is the reference angular frequency; ω * is the updated virtual synchronous angular frequency reference value.

[0044] The present application also provides a terminal device, including:

[0045] one or more processors;

[0046] A memory, coupled to the processor, for storing one or more programs;

[0047] When the one or more programs are executed by the one or more processors, the one or more processors implement the pre-synchronization grid-connection method based on virtual synchronization control as described in the above-mentioned embodiment of the invention.

[0048] The present application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the pre-synchronization grid-connection method based on virtual synchronization control as described in the above-mentioned embodiment of the invention is implemented.

[0049] The following beneficial effects are achieved by implementing the present invention:

[0050] The present invention provides a pre-synchronization grid-connected method, apparatus, terminal equipment and storage medium based on virtual synchronization control. The method repeatedly performs a pre-synchronization operation when the state identifier corresponding to the additional frequency holding signal is a first identifier, and stops the pre-synchronization operation only when the state identifier corresponding to the additional frequency holding signal is changed to a second identifier. Thus, when the pre-synchronization operation is performed, the control structure of the virtual synchronous machine is continuously updated. Therefore, when the additional frequency holding signal is changed to the second identifier (i.e., whether the voltage q-axis component deviation is less than a preset threshold), the power electronic interface power supply controlled by the virtual synchronous machine is connected to the power grid system, which can avoid large impact current in the closing and grid-connected process, thereby ensuring the safe and stable operation of the power electronic interface power supply and the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 It is a flowchart of a pre-synchronization grid-connection method based on virtual synchronization control provided by a certain embodiment of the present application;

[0053] Figure 2 is a control structure diagram of a virtual synchronous machine provided in a certain embodiment of the present application;

[0054] Figure 3 It is a structural schematic diagram of a pre-synchronization grid-connected device based on virtual synchronization control provided by a certain embodiment of the present application;

[0055] Figure 4 It is a structural diagram of a terminal device provided in a certain embodiment of the present application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0058] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0059] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0060] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0061] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0062] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0063] See also Figure 1 , is a flow chart of a pre-synchronization grid-connection method based on virtual synchronization control provided by an embodiment of the present invention, including:

[0064] S1. After receiving the grid connection instruction, setting the state identifier corresponding to the additional frequency holding signal to the first identifier; wherein the additional frequency holding signal is used to indicate the pre-synchronization operation state;

[0065] Specifically, after receiving the grid connection instruction, the additional frequency holding signal needs to be initialized, thereby setting the state flag corresponding to the additional frequency holding signal to 0, that is, when the state flag corresponding to the additional frequency holding signal is 0, the pre-synchronization operation is performed.

[0066] S2, when the state identifier corresponding to the additional frequency holding signal is the first identifier, repeatedly performing the pre-synchronization operation until the state identifier corresponding to the additional frequency holding signal changes to the second identifier, and stopping the pre-synchronization operation;

[0067] The pre-synchronization operation includes:

[0068] Collect the current grid-side voltage of the converter and the current machine-end voltage of the converter;

[0069] Calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage, and determining whether the voltage q-axis component deviation is less than a preset threshold value,

[0070] If yes, setting the state flag corresponding to the additional frequency holding signal to the second flag;

[0071] If not, generating a corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine;

[0072] Indicatively, when the state identifier corresponding to the additional frequency holding signal is 0, the pre-synchronization operation is repeatedly performed;

[0073] Specifically, the current grid-side voltage u of the converter is collected.grid And the current terminal voltage u of the converter vsc , and calculating the voltage q-axis component deviation between the machine-side voltage and the grid-side voltage;

[0074] In a preferred embodiment, the calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage includes:

[0075] Performing Park transformation on the grid-side voltage to obtain a first voltage q-axis component of the grid-side voltage;

[0076] Performing Park transformation on the machine-end voltage to obtain a second voltage q-axis component of the machine-end voltage;

[0077] Subtracting the first voltage q-axis component from the second voltage q-axis component to obtain the voltage q-axis component deviation;

[0078] Specifically, the grid-side voltage u grid Perform Park transformation to obtain the first voltage q-axis component u of the grid-side voltage qgrid ; The terminal voltage u vsc Perform Park transformation to obtain the second voltage q-axis component u of the terminal voltage qvsc ;

[0079] Then, the first voltage q-axis component and the second voltage q-axis component are subtracted to obtain the voltage q-axis component deviation, and the specific formula is as follows:

[0080] Δu q =u qgrid -u qvsc ;

[0081] In the formula, Δu q is the voltage q-axis component deviation.

[0082] It should be noted that since Park transformation is a coordinate transformation method commonly used in motor control, the specific solution process will not be described in detail in this application.

[0083] In a preferred embodiment, the generating of the corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain the updated second control structure of the virtual synchronous machine includes:

[0084] Inputting the voltage q-axis component deviation into a preset PI controller, so that the PI controller outputs a corresponding additional frequency component according to the voltage q-axis component deviation;

[0085] superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine;

[0086] Specifically, the integral coefficient in the PI controller is k i , the proportional coefficient in the PI controller is k p , the Laplace operator is s, and the above parameters are all preset constants;

[0087] Therefore, the voltage q-axis component deviation Δu q The input value is preset in the PI controller, so that the PI controller outputs the corresponding additional frequency component according to the voltage q-axis component deviation, and the specific formula is as follows:

[0088]

[0089] Where omega_{add} is the additional frequency component;

[0090] Then, the additional frequency component omega_{add} is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0091] In a preferred embodiment, the step of superimposing the additional frequency component onto the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes:

[0092] The updated second control structure of the virtual synchronous machine is calculated by the following formula:

[0093]

[0094] In the formula, u qgrid is the first voltage q-axis component; u qvsc is the second voltage q-axis component; k p is the proportional coefficient of the PI controller; k i is the integral coefficient of the PI controller; s is the Laplace operator; P * is the active power reference value; P is the active power measured at the grid-connected point of the converter; D is the virtual synchronous droop coefficient; T J is the virtual synchronous inertia time constant; ω0 is the reference angular frequency; ω * is the updated virtual synchronous angular frequency reference value;

[0095] Specifically, see Figure 2, by superimposing the calculated additional frequency component omega_{add} to the original first control structure of the virtual synchronous machine, the updated second control structure of the virtual synchronous machine is obtained, wherein P is the active power measured at the grid-connected point of the converter. When the converter sends electric energy to the grid, that is, the active power output by the converter flows to the grid, the measured active power P is positive at this time. On the contrary, when the converter absorbs electric energy from the grid, that is, the active power input by the converter comes from the grid, the measured active power P is negative at this time.

[0096] Based on the updated virtual synchronous angular frequency reference value in the second control structure, the output frequency and phase of the virtual synchronous machine are adjusted to reduce the error between the grid-side voltage and the machine-end voltage.

[0097] S3, when the state identifier corresponding to the additional frequency maintaining signal is the second identifier, the power electronic interface power supply controlled by the virtual synchronous machine is incorporated into the power grid system;

[0098] Specifically, during a certain pre-synchronization operation, if it is determined that the voltage q-axis component deviation is less than a preset threshold, at this time, the state identifier corresponding to the additional frequency holding signal is set to the second identifier, and then when the state identifier corresponding to the additional frequency holding signal is the second identifier, the power electronic interface power supply controlled by the virtual synchronous machine is incorporated into the power grid system;

[0099] It should be noted that by ensuring that the voltage q-axis component deviation is less than a given preset threshold, a large inrush current can be avoided during the closing and grid-connected process, thus protecting the safety of equipment and the power system;

[0100] Preferably, the given preset threshold is 0.01 pu.

[0101] See also Figure 3 , is a pre-synchronization grid-connected device based on virtual synchronization control provided by an embodiment of the present invention, comprising: an additional frequency holding signal initialization module, a pre-synchronization operation execution module and a grid-connected module;

[0102] The additional frequency holding signal initialization module is used to set the state identifier corresponding to the additional frequency holding signal to the first identifier after receiving the grid connection instruction; wherein the additional frequency holding signal is used to indicate the pre-synchronization operation state;

[0103] The pre-synchronization operation execution module is used to repeatedly execute the pre-synchronization operation when the state identifier corresponding to the additional frequency holding signal is the first identifier, until the state identifier corresponding to the additional frequency holding signal changes to the second identifier, and stop the pre-synchronization operation;

[0104] The grid-connected module is used to connect the power electronic interface power supply controlled by the virtual synchronous machine into the power grid system when the state identifier corresponding to the additional frequency holding signal is the second identifier;

[0105] The pre-synchronization operation includes:

[0106] Collect the current grid-side voltage of the converter and the current machine-end voltage of the converter;

[0107] Calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage, and determining whether the voltage q-axis component deviation is less than a preset threshold value,

[0108] If yes, setting the state flag corresponding to the additional frequency holding signal to the second flag;

[0109] If not, a corresponding additional frequency component is generated according to the voltage q-axis component deviation, and the additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0110] In a preferred embodiment, the generating of the corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain the updated second control structure of the virtual synchronous machine includes:

[0111] Inputting the voltage q-axis component deviation into a preset PI controller, so that the PI controller outputs a corresponding additional frequency component according to the voltage q-axis component deviation;

[0112] The additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

[0113] In a preferred embodiment, the calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage includes:

[0114] Performing Park transformation on the grid-side voltage to obtain a first voltage q-axis component of the grid-side voltage;

[0115] Performing Park transformation on the machine-end voltage to obtain a second voltage q-axis component of the machine-end voltage;

[0116] The voltage q-axis component deviation is obtained by subtracting the first voltage q-axis component from the second voltage q-axis component.

[0117] In a preferred embodiment, the step of superimposing the additional frequency component onto the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes:

[0118] The updated second control structure of the virtual synchronous machine is calculated by the following formula:

[0119]

[0120] In the formula, u qgrid is the first voltage q-axis component; u qvsc is the second voltage q-axis component; k p is the proportional coefficient of the PI controller; k i is the integral coefficient of the PI controller; s is the Laplace operator; P * is the active power reference value; P is the active power measured at the grid-connected point of the converter; D is the virtual synchronous droop coefficient; T J is the virtual synchronous inertia time constant; ω0 is the reference angular frequency; ω * is the updated virtual synchronous angular frequency reference value.

[0121] See also Figure 4 , a certain embodiment of the present application further provides a terminal device, including:

[0122] one or more processors;

[0123] A memory, coupled to the processor, for storing one or more programs;

[0124] When the one or more programs are executed by the one or more processors, the one or more processors implement the pre-synchronization grid-connected method based on virtual synchronization control as described above.

[0125] The processor is used to control the overall operation of the terminal device to complete all or part of the steps of the above-mentioned pre-synchronization grid-connected method based on virtual synchronization control. The memory is used to store various types of data to support the operation of the terminal device, and these data may include, for example, instructions for any application or method used to operate on the terminal device, and data related to the application. The memory can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (Static Random Access Memory, referred to as SRAM), electrically erasable programmable read-only memory (Electrically Erasable Programmable Read-Only Memory, referred to as EEPROM), erasable programmable read-only memory (Erasable Programmable Read-Only Memory, referred to as EPROM), programmable read-only memory (Programmable Read-Only Memory, referred to as PROM), read-only memory (Read-Only Memory, referred to as ROM), magnetic memory, flash memory, magnetic disk or optical disk.

[0126] In an exemplary embodiment, the terminal device can be implemented by one or more application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), field programmable gate arrays (FPGA), controllers, microcontrollers, microprocessors or other electronic components to execute the pre-synchronization grid-connected method based on virtual synchronization control as described in any of the above embodiments, and achieve the same technical effect as the above method.

[0127] In another exemplary embodiment, a computer-readable storage medium including a computer program is also provided, and when the computer program is executed by a processor, the steps of the pre-synchronization grid-connection method based on virtual synchronization control as described in any of the above embodiments are implemented. For example, the computer-readable storage medium can be the above-mentioned memory including the computer program, and the above-mentioned computer program can be executed by the processor of the terminal device to complete the pre-synchronization grid-connection method based on virtual synchronization control as described in any of the above embodiments, and achieve the technical effect consistent with the above method.

[0128] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A pre-synchronization grid-connection method based on virtual synchronization control, characterized in that: include: After receiving the grid connection instruction, the state flag corresponding to the additional frequency holding signal is set to the first flag; wherein the additional frequency holding signal is used to indicate the pre-synchronization operation state; When the state identifier corresponding to the additional frequency holding signal is a first identifier, repeatedly performing a pre-synchronization operation until the state identifier corresponding to the additional frequency holding signal changes to a second identifier, and stopping the pre-synchronization operation; When the state identifier corresponding to the additional frequency maintaining signal is a second identifier, the power electronic interface power supply controlled by the virtual synchronous machine is incorporated into the power grid system; The pre-synchronization operation includes: Collect the current grid-side voltage of the converter and the current machine-end voltage of the converter; Calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage, and determining whether the voltage q-axis component deviation is less than a preset threshold value, If yes, setting the state flag corresponding to the additional frequency holding signal to the second flag; If not, a corresponding additional frequency component is generated according to the voltage q-axis component deviation, and the additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

2. The pre-synchronization grid-connection method based on virtual synchronization control according to claim 1, characterized in that: The method of generating a corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes: Inputting the voltage q-axis component deviation into a preset PI controller, so that the PI controller outputs a corresponding additional frequency component according to the voltage q-axis component deviation; The additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

3. The pre-synchronization grid-connection method based on virtual synchronization control according to claim 2, characterized in that: The calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage includes: Performing Park transformation on the grid-side voltage to obtain a first voltage q-axis component of the grid-side voltage; Performing Park transformation on the machine-end voltage to obtain a second voltage q-axis component of the machine-end voltage; The voltage q-axis component deviation is obtained by subtracting the first voltage q-axis component from the second voltage q-axis component.

4. The pre-synchronization grid-connection method based on virtual synchronization control according to claim 3, characterized in that: The step of superimposing the additional frequency component onto the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes: The updated second control structure of the virtual synchronous machine is calculated by the following formula: In the formula, u qgrid is the first voltage q-axis component; u qvsc is the second voltage q-axis component; k p is the proportional coefficient of the PI controller; k i is the integral coefficient of the PI controller; s is the Laplace operator; P * is the active power reference value; P is the active power measured at the grid-connected point of the converter; D is the virtual synchronous droop coefficient; T J is the virtual synchronous inertia time constant; ω0 is the reference angular frequency; ω * is the updated virtual synchronous angular frequency reference value.

5. A pre-synchronization grid-connected device based on virtual synchronization control, characterized in that: include: Additional frequency holding signal initialization module, pre-synchronization operation execution module and grid connection module; The additional frequency holding signal initialization module is used to set the state identifier corresponding to the additional frequency holding signal to the first identifier after receiving the grid connection instruction; wherein the additional frequency holding signal is used to indicate the pre-synchronization operation state; The pre-synchronization operation execution module is used to repeatedly execute the pre-synchronization operation when the state identifier corresponding to the additional frequency holding signal is the first identifier, until the state identifier corresponding to the additional frequency holding signal changes to the second identifier, and stop the pre-synchronization operation; The grid-connected module is used to connect the power electronic interface power supply controlled by the virtual synchronous machine into the power grid system when the state identifier corresponding to the additional frequency holding signal is the second identifier; The pre-synchronization operation includes: Collect the current grid-side voltage of the converter and the current machine-end voltage of the converter; Calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage, and determining whether the voltage q-axis component deviation is less than a preset threshold value, If yes, setting the state flag corresponding to the additional frequency holding signal to the second flag; If not, a corresponding additional frequency component is generated according to the voltage q-axis component deviation, and the additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

6. The pre-synchronization grid-connected device based on virtual synchronization control according to claim 5, characterized in that: The method of generating a corresponding additional frequency component according to the voltage q-axis component deviation, and superimposing the additional frequency component to the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes: Inputting the voltage q-axis component deviation into a preset PI controller, so that the PI controller outputs a corresponding additional frequency component according to the voltage q-axis component deviation; The additional frequency component is superimposed on the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine.

7. The pre-synchronization grid-connected device based on virtual synchronization control according to claim 6, characterized in that: The calculating the voltage q-axis component deviation between the grid-side voltage and the generator-end voltage includes: Performing Park transformation on the grid-side voltage to obtain a first voltage q-axis component of the grid-side voltage; Performing Park transformation on the machine-end voltage to obtain a second voltage q-axis component of the machine-end voltage; The voltage q-axis component deviation is obtained by subtracting the first voltage q-axis component from the second voltage q-axis component.

8. The pre-synchronization grid-connected device based on virtual synchronization control according to claim 7, characterized in that: The step of superimposing the additional frequency component onto the original first control structure of the virtual synchronous machine to obtain an updated second control structure of the virtual synchronous machine includes: The updated second control structure of the virtual synchronous machine is calculated by the following formula: In the formula, u qgrid is the first voltage q-axis component; u qvsc is the second voltage q-axis component; k p is the proportional coefficient of the PI controller; k i is the integral coefficient of the PI controller; s is the Laplace operator; P * is the active power reference value; P is the active power measured at the grid-connected point of the converter; D is the virtual synchronous droop coefficient; T J is the virtual synchronous inertia time constant; ω0 is the reference angular frequency; ω * is the updated virtual synchronous angular frequency reference value.

9. A terminal device, characterized in that: include: one or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the pre-synchronization grid-connected method based on virtual synchronization control as described in any one of claims 1 to 4.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the pre-synchronization grid-connection method based on virtual synchronization control as described in any one of claims 1 to 4 is implemented.

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