Network construction type SVG control method suitable for multiple power grid intensities

Abstract

The invention relates to a power electronic technology, and aims to provide a network construction type SVG control method suitable for multiple power grid strengths. Comprising the following steps: obtaining a power grid angular frequency based on a phase-locked loop principle, and obtaining an internal frequency of SVG equipment based on capacitor voltage-frequency droop control; multiplying the two angular frequency values by respective corresponding power grid intensity adaptation parameters to obtain a phase-locked loop reference angular frequency and a droop reference angular frequency, and performing integral calculation on the phase-locked loop reference angular frequency and the droop reference angular frequency and a power grid nominal angular frequency to obtain a phase angle; and finally, a switching signal is generated in an SVG control link, so that control of SVG equipment is realized. According to the method, a more stable reference power grid phase angle is obtained, the broadband oscillation instability condition possibly occurring under a strong power grid can be suppressed, the network-forming SVG can work under different power grid intensities, and the operation stability is improved; the method can enhance the power grid synchronization stability of the network construction type control under the strong power grid, and is suitable for different system conditions.

Description

Technical Field

[0001] The invention relates to the field of power electronics technology and grid-connected reactive power compensation control technology, and in particular to a grid-forming SVG control method suitable for multiple power grid strengths. Background Art

[0002] With the rapid growth of new energy installed capacity, power quality issues are becoming increasingly prominent. In the power distribution system, more and more motors and new impact loads inject a large amount of reactive power and harmonic current into the power grid, causing voltage deviation, fluctuation and flicker, three-phase imbalance and other problems in the power grid. At the same time, in order to cope with energy shortages and ecological environmental protection needs, more and more green energy is connected to the power grid in a distributed form, making the power grid structure more complex and posing challenges to safe and reliable operation.

[0003] As a key device, the static VAR compensator (SVG) based on grid-type control plays an important role in improving the power quality and power supply reliability of the distribution network. Grid-type control can also provide inertia support and damping characteristics for weak power grids, thereby enhancing the stability of the power grid. Therefore, grid-type SVG has significant advantages and potential in solving the above problems.

[0004] However, the traditional grid-forming SVG control method has certain limitations when facing different grid strengths. Under weak grid conditions, the grid-forming control can provide inertia support for the system by establishing a voltage synchronization link on its own, so that the system maintains good stability. However, when connected to a strong grid, broadband oscillation instability may occur, and even cause equipment damage or system failure.

[0005] Therefore, it is necessary to propose new solutions to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a grid-forming SVG control method suitable for multiple grid strengths.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] A grid-forming SVG control method applicable to multiple grid strengths is provided, comprising the following steps:

[0009] Detect the q-axis component U of the voltage at the grid connection point of the static reactive power compensation device SVG PCC,q 、The total capacitance voltage V on the DC side of the SVG device dc , the line impedance on the grid side and the grid nominal angular frequency ω0;

[0010] According to the line impedance on the grid side, calculate the short circuit ratio SCR to determine the grid strength; according to the specific value of the short circuit ratio SCR, select the appropriate grid strength adaptation parameter K PLL and K PS ;

[0011] Let the q-axis component reference value of the grid-connected point voltage be is always 0, and then is related to the q-axis component U of the grid voltage PCC,q The calculated result is used as input to obtain the grid angular frequency based on the phase-locked loop principle; the angular frequency value is compared with the grid strength adaptation parameter K PLL Multiply them to get the phase-locked loop reference angular frequency ω PLL ;

[0012] The total capacitance voltage V on the DC side of the SVG device is used dc The total capacitance voltage reference value of the DC side The calculation result is used as input to obtain the internal frequency of the SVG device based on the capacitor voltage-frequency droop control; the internal frequency value is compared with the grid strength adaptation parameter K PS Multiply them to get the droop reference angular frequency ω VSG ;

[0013] Using the grid nominal angular frequency ω0 and the phase-locked loop reference angular frequency ω PLL and droop reference angular frequency ω VSG An integral calculation is performed to obtain a phase angle θ. The phase angle θ is used for Park transformation in the SVG control link, and then a switching signal is generated through intra-phase and inter-phase voltage balancing. The SVG device is controlled by controlling the on and off of the switch devices inside the SVG device.

[0014] As a preferred solution of the present invention, the grid strength adaptation parameter K is determined according to the following method: PLL and K PS The value of

[0015]

[0016] In the formula, SCR is the short-circuit ratio, which refers to the system short-circuit capacity divided by the equipment capacity; when SCR is less than 3, the power grid system is a weak grid; when SCR is greater than 3, the power grid system is a strong grid.

[0017] As a preferred embodiment of the present invention, the closed-loop transfer function of the phase-locked loop is shown as follows:

[0018]

[0019] In this formula, G PLL (s) is the closed-loop transfer function of the phase-locked loop; s is the complex variable in the transfer function; is the natural frequency; V m is the grid voltage amplitude; k i , k p They are the integral coefficient and proportional coefficient of the phase-locked loop PI controller respectively.

[0020] As a preferred solution of the present invention, the capacitor voltage-frequency droop control is based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor to simulate the synchronous characteristics of the synchronous machine; the transfer function used is as follows:

[0021]

[0022] In the formula, G VSG (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

[0023] As a preferred solution of the present invention, the d-axis and q-axis components of the output voltage amplitude reference value are obtained based on reactive power-voltage droop control, and the d-axis and q-axis components of the modulation voltage are obtained after being processed by virtual impedance voltage control and AC current inner loop control in sequence. It is then used together with the phase angle θ as the input of the Park transform.

[0024] As a preferred solution of the present invention, the SVG device is a cascaded H-bridge star topology structure or a triangle topology structure; each phase in the SVG device is composed of a filter inductor and N sub-modules with the same electrical structure and parameters in series; each sub-module is composed of a capacitor and 4 switching tubes forming an H-bridge, and the switching tubes are IGBTs or IGCTs.

[0025] The present invention also provides a device for implementing a grid-type SVG control method suitable for multiple grid strengths, the device comprising a grid strength adaptation parameter calculation module, a phase-locked loop module, a capacitor voltage-frequency droop control module, an integral calculation module and an SVG control module; wherein,

[0026] The grid strength adaptation parameter calculation module calculates the short circuit ratio SCR according to the line impedance on the grid side, and determines the appropriate grid strength adaptation parameter K according to the specific value of the short circuit ratio SCR. PLL and K PS ;

[0027] The phase-locked loop module sets the q-axis component reference value U of the grid-connected point voltage * PCC,q It is always 0 and is connected to the q-axis component U of the grid voltage. PCC,qThe difference is made, and the difference result is used as input to obtain the grid angular frequency based on the phase-locked loop principle; the angular frequency value is compared with the grid strength adaptation parameter K PLL Multiply them to get the phase-locked loop reference angular frequency ω PLL ;

[0028] The capacitor voltage-frequency droop control module uses the total capacitor voltage V on the DC side of the SVG device. dc The total capacitance voltage reference value of the DC side The difference is made, and the difference result is used as input to obtain the internal frequency of the SVG device based on the capacitor voltage-frequency droop control; the internal frequency value is compared with the grid strength adaptation parameter K PS Multiply them to get the droop reference angular frequency ω VSG ;

[0029] The integral calculation module uses the grid nominal angular frequency ω0 and the phase-locked loop reference angular frequency ω PLL and droop reference angular frequency ω VSG Perform integral calculation to obtain the phase angle θ used for Park transformation in the SVG control link;

[0030] The SVG control module uses the phase angle θ obtained by the integral calculation module to generate a switching signal based on reactive power-voltage droop control, virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing. The SVG device is controlled by controlling the on and off of the internal switching devices of the SVG device.

[0031] As a preferred solution of the present invention, the grid strength adaptation parameter calculation module determines the grid strength adaptation parameter K according to the following method: PLL and K PS The value of

[0032]

[0033] In the formula, SCR is the short-circuit ratio, which refers to the system short-circuit capacity divided by the equipment capacity; when SCR is less than 3, the power grid system is a weak grid; when SCR is greater than 3, the power grid system is a strong grid.

[0034] As a preferred solution of the present invention, the closed-loop transfer function used by the phase-locked loop module is shown as follows:

[0035]

[0036] In this formula, G PLL (s) is the closed-loop transfer function of the phase-locked loop; s is a complex variable in the transfer function; is the natural frequency; V m is the grid voltage amplitude; k i , kp They are the integral coefficient and proportional coefficient of the phase-locked loop PI controller respectively.

[0037] As a preferred solution of the present invention, the capacitor voltage-frequency droop control performed by the capacitor voltage-frequency droop control module is based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor to simulate the synchronous characteristics of the synchronous machine; the transfer function used is as follows:

[0038]

[0039] In the formula, G VSG (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

[0040] As a preferred solution of the present invention, the SVG control module obtains the d-axis and q-axis components of the output voltage amplitude reference value based on reactive power-voltage droop control; then the d-axis and q-axis components of the modulated voltage are obtained after being processed by virtual impedance voltage control and AC current inner loop control in sequence. It is then used together with the phase angle θ as the input of the Park transform.

[0041] The present invention also provides a computer device, comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes the aforementioned grid-forming SVG control method applicable to multiple grid strengths.

[0042] The present invention also provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the aforementioned grid-forming SVG control method applicable to multiple power grid strengths.

[0043] Compared with the prior art, the advantages of the present invention are:

[0044] 1. The present invention obtains a more stable reference grid phase angle by utilizing a phase-locked loop and a mesh-type control capacitor voltage-frequency link; thus, it can suppress the broadband oscillation instability that may occur under a strong grid, so that the mesh-type SVG can work under different grid strengths, thereby improving the operating stability of the SVG equipment.

[0045] 2. The present invention weakens the influence of a strong power grid on the grid configuration control by detecting the q-axis component of the grid connection point voltage and combining the DC side capacitor voltage and the grid nominal angular frequency. This approach flexibly utilizes the SVG control function and is an innovative design that breaks through the conventional technical ideas in this field.

[0046] 3. The present invention can enhance the grid synchronization stability of the grid-type control under a strong power grid, can adapt to different system conditions, and ensure the safe and reliable operation of the entire power grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the topological structure of a meshed SVG main circuit based on cascaded H-bridges in an embodiment of the present invention.

[0048] Figure 2 It is a control block diagram of the mesh-type SVG in an embodiment of the present invention.

[0049] Figure 3 It is the waveform diagram of active and reactive power output of the grid-type SVG when the short-circuit ratio is 8.

[0050] Figure 4 It is the waveform diagram of active and reactive power output of the grid-type SVG when the short-circuit ratio is 2.

[0051] Figure 5 It is the voltage and current waveform of the grid-connected point of the grid-forming SVG when the short-circuit ratio is 8.

[0052] Figure 6 It is the voltage and current waveform of the grid-connected point of the grid-forming SVG when the short-circuit ratio is 2. DETAILED DESCRIPTION

[0053] First of all, it should be explained that the present invention relates to circuit control technology, which is an application of computer technology in the field of electronic circuit technology. In the process of implementing the present invention, the application of multiple software function modules will be involved. The applicant believes that after carefully reading the application documents and accurately understanding the implementation principle and purpose of the present invention, in combination with the existing known technology, those skilled in the art can fully use the software programming skills they have mastered to implement the present invention. The aforementioned software function modules include but are not limited to: power grid strength adaptation parameter calculation module, phase-locked loop module, capacitor voltage-frequency droop control module, integral calculation module and SVG control module, etc. All those mentioned in the application documents of the present invention belong to this category, and the applicant will not list them one by one.

[0054] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0055] In the present invention, the static VAR compensation device (SVG) can be optionally based on a cascaded H-bridge star topology or a triangle topology; each phase in the SVG device is composed of a filter inductor and N sub-modules with the same electrical structure and parameters in series; each sub-module is composed of a capacitor and 4 switching tubes forming an H-bridge, and the switching tube is an IGBT or IGCT. Figure 1The main circuit topology of a meshed SVG based on a cascaded H-bridge is shown in FIG. 1 . The SVG consists of three phases (a, b, c) connected in a star configuration.

[0056] As an example, Figure 2 The process of implementing the grid-forming SVG control method is demonstrated. The SVG control method detects the q-axis component of the voltage at the grid-connected point of the SVG device and combines the DC side capacitor voltage and the nominal angular frequency of the grid to weaken the influence of the strong grid on the grid-forming control, enhance the grid synchronization stability of the grid-forming control under the strong grid, and enable the system to operate reliably under different grid strengths.

[0057] 1. Grid-type SVG control method applicable to multiple power grid strengths

[0058] For ease of understanding, a control cycle is used as an example for explanation. The control block diagram of this method is as follows: Figure 2 As shown, the specific steps include:

[0059] (1) Detect the q-axis component U of the voltage at the grid connection point where the SVG device is connected to the grid PCC,q 、The total capacitance voltage V on the DC side of the SVG device dc , the line impedance on the grid side and the grid nominal angular frequency ω0;

[0060] (2) Use the line impedance on the grid side to calculate the short-circuit ratio SCR to determine the grid strength, and then confirm the grid strength adaptation parameter K according to the following method PLL and K PS The value of

[0061]

[0062] In the formula, SCR is the short-circuit ratio, which refers to the system short-circuit capacity divided by the equipment capacity; when SCR is less than 3, the power grid system is a weak grid; when SCR is greater than 3, the power grid system is a strong grid.

[0063] (3) Let the q-axis component reference value of the grid-connected point voltage be is always 0, and then is related to the q-axis component U of the grid voltage PCC,q The calculated result is used as input to obtain the grid angular frequency based on the phase-locked loop principle; the angular frequency value is compared with the grid strength adaptation parameter K PLL Multiply them to get the phase-locked loop reference angular frequency ω PLL ;

[0064] The closed-loop transfer function of the phase-locked loop is shown below:

[0065]

[0066] In this formula, G PLL(s) is the closed-loop transfer function of the phase-locked loop; s is the complex variable in the transfer function; is the natural frequency; V m is the grid voltage amplitude; k i , k p They are the integral coefficient and proportional coefficient of the phase-locked loop PI controller respectively.

[0067] (4) Using the total capacitance voltage V on the DC side of the SVG device dc The total capacitance voltage reference value of the DC side The calculation result is used as input to obtain the internal frequency of the SVG device based on the capacitor voltage-frequency droop control; the internal frequency value is compared with the grid strength adaptation parameter K PS Multiply them to get the droop reference angular frequency ω VSG ;

[0068] Capacitor voltage-frequency droop control is based on the similarity between the dynamics of DC capacitors and the dynamics of generator rotors to simulate the synchronous characteristics of synchronous machines; the transfer function used is shown below:

[0069]

[0070] In the formula, G VSG (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

[0071] (5) Using the grid nominal angular frequency ω0 and the phase-locked loop reference angular frequency ω PLL and droop reference angular frequency ω VSG Perform integral calculation to obtain the phase angle θ;

[0072] (6) Based on reactive power-voltage droop control, the d-axis and q-axis components of the output voltage amplitude reference value are obtained, which are processed by the virtual impedance voltage control and AC current inner loop control of the SVG control link to obtain the d-axis and q-axis components of the modulated voltage. The phase angle θ is then used together as the input of the Park transformation, and a switching signal is finally generated after the intra-phase and inter-phase voltage balancing process, and the control of the SVG device is achieved by controlling the on and off of the switching devices inside the SVG device.

[0073] 2. To implement the above control method, the present invention provides a device for implementing a grid-type SVG control method applicable to multiple grid strengths, characterized in that the device includes a grid strength adaptation parameter calculation module, a phase-locked loop module, a capacitor voltage-frequency droop control module, an integral calculation module and an SVG control module; wherein the grid strength adaptation parameter calculation module is used to obtain a suitable grid strength adaptation parameter K PLL and K PS ; The phase-locked loop module obtains the grid angular frequency based on the phase-locked loop principle and adapts the parameter K to the grid strength PLL Multiply to get the phase-locked loop reference angular frequency ω PLL The capacitor voltage-frequency droop control module obtains the internal frequency of the SVG device based on the capacitor voltage-frequency droop control, and adapts to the grid strength parameter K PS Multiply to get the droop reference angular frequency ω VSG ; The integral calculation module uses the grid nominal angular frequency ω0 and the phase-locked loop reference angular frequency ω PLL and droop reference angular frequency ω VSG An integral calculation is performed to obtain the phase angle θ used for Park transformation in the SVG control link; the SVG control module obtains the calculation result based on reactive power-voltage droop control, and uses the result together with the phase angle θ as the input of Park transformation in the SVG control link, and finally generates a switching signal to control the on and off of the switching device inside the SVG device, thereby realizing the control of the SVG device.

[0074] The present invention also provides a computer device, comprising: at least one processor, and a memory connected to the at least one processor, wherein the memory stores instructions executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes the aforementioned grid-forming SVG control method applicable to multiple grid strengths. The calculation logic diagram of some modules is shown in FIG. Figure 2 shown.

[0075] Furthermore, the present invention also provides corresponding computer equipment and computer-readable storage media, which implement the aforementioned grid-forming SVG control method applicable to multiple power grid strengths by executing the stored computer program.

[0076] Effect verification experiment:

[0077] For ease of understanding, this embodiment constructs a cascaded H-bridge network-based SVG and control model in the PLECS simulation software, in order to verify the specific feasibility and corresponding technical effects of the present invention.

[0078] The grid voltage is set to 35kV, the DC side capacitor voltage is set to 40kV, the short-circuit ratios are set to 8 and 2 respectively, the grid-type SVG works under constant reactive conditions, and the output reactive power is -4.2MVar.

[0079] The simulation results are as follows Figures 3 to 6 As shown in the figures, it can be seen that under different grid strengths, the control scheme of the present invention can work according to the rated power without the problem of broadband oscillation instability. Therefore, the method can realize the grid-type control under different grid strengths while ensuring the safe and reliable operation of the system.

[0080] In addition, SVG equipment mainly relies on outputting reactive power to improve current quality and does not have the ability to directly control output active power. Figure 3 , 4 The active power output curve shown in shows that the SVG device under the simulation condition is in normal working condition and does not output active power.

[0081] In summary, the technical solution of the present invention comprehensively considers the grid-connected scenarios of different grid strengths, calculates a more stable phase angle through a phase-locked loop and a DC side capacitor voltage-frequency link, suppresses the broadband oscillation problem that may occur in the grid-connected type under a strong grid to a certain extent, and improves the operating stability of the grid-connected SVG under different grid strengths.

Claims

1. A control method for a static reactive power compensation device SVG suitable for multiple power grid strengths, characterized in that: The following steps are involved: Detect the q-axis component U of the voltage at the grid connection point of the static reactive power compensation device SVG PCC,q 、The total capacitance voltage V on the DC side of the SVG device dc , the line impedance on the grid side and the grid nominal angular frequency ω0; According to the line impedance on the grid side, the short-circuit ratio SCR is calculated to determine the grid strength; according to the specific value of the short-circuit ratio SCR, the adaptive parameter K is selected according to the grid strength. PLL and K PS ; Let the q-axis component reference value of the grid-connected point voltage be is always 0, and then is related to the q-axis component U of the grid voltage PCC,q The calculated result is used as input to obtain the grid angular frequency based on the phase-locked loop principle; the angular frequency value is compared with the grid strength adaptation parameter K PLL Multiply them to get the phase-locked loop reference angular frequency ω PLL ; The total capacitance voltage V on the DC side of the SVG device is used dc The total capacitance voltage reference value of the DC side The calculated result is used as input to obtain the internal frequency of the SVG device based on the capacitor voltage-frequency droop control; the internal frequency value is compared with the grid strength adaptation parameter K PS Multiply them to get the droop reference angular frequency ω VSG ; Using the grid nominal angular frequency ω0 and the phase-locked loop reference angular frequency ω PLL and droop reference angular frequency ω VSG An integral calculation is performed to obtain a phase angle θ. The phase angle θ is used for Park transformation in the SVG control link, and then a switching signal is generated through intra-phase and inter-phase voltage balancing. The SVG device is controlled by controlling the on and off of the switch devices inside the SVG device.

2. The method according to claim 1, characterized in that Determine the grid strength adaptation parameter K according to the following method PLL and K PS The value of In the formula, SCR is the short-circuit ratio, which refers to the system short-circuit capacity divided by the equipment capacity; when SCR is less than 3, the power grid system is a weak grid; when SCR is greater than 3, the power grid system is a strong grid.

3. The method according to claim 1, characterized in that The closed-loop transfer function of the phase-locked loop is shown below: In this formula, G PLL (s) is the closed-loop transfer function of the phase-locked loop; s is a complex variable in the transfer function; is the natural frequency; V m is the grid voltage amplitude; k i , k p They are the integral coefficient and proportional coefficient of the phase-locked loop PI controller respectively.

4. The method according to claim 1, characterized in that: The capacitor voltage-frequency droop control is based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor to simulate the synchronous characteristics of the synchronous machine; the transfer function used is as follows: In the formula, G VSG (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

5. The method according to claim 1, characterized in that: Based on reactive power-voltage droop control, the d-axis and q-axis components of the output voltage amplitude reference value are obtained, and the d-axis and q-axis components of the modulation voltage are obtained after being processed by virtual impedance voltage control and AC current inner loop control in turn. It is then used together with the phase angle θ as the input of the Park transform.

6. The method according to claim 1, characterized in that The SVG device is a cascaded H-bridge star topology structure or a triangle topology structure; each phase in the SVG device is composed of a filter inductor and N sub-modules with the same electrical structure and parameters in series; each sub-module is composed of a capacitor and 4 switching tubes forming an H-bridge, and the switching tubes are IGBTs or IGCTs.

7. A device for implementing a grid-forming SVG control method applicable to multiple grid strengths, characterized in that: The device includes a power grid strength adaptation parameter calculation module, a phase-locked loop module, a capacitor voltage-frequency droop control module, an integral calculation module and an SVG control module; wherein, The grid strength adaptation parameter calculation module calculates the short circuit ratio SCR according to the line impedance on the grid side, and determines the grid strength adaptation parameter K according to the specific value of the short circuit ratio SCR. PLL and K PS ; The phase-locked loop module sets the q-axis component reference value U of the grid-connected point voltage * PCC,q It is always 0 and is connected to the q-axis component U of the grid voltage. PCC,q The difference is made, and the difference result is used as input to obtain the grid angular frequency based on the phase-locked loop principle; the angular frequency value is compared with the grid strength adaptation parameter K PLL Multiply them to get the phase-locked loop reference angular frequency ω PLL ; The capacitor voltage-frequency droop control module uses the total capacitor voltage V on the DC side of the SVG device. dc The total capacitance voltage reference value of the DC side The difference is made, and the difference result is used as input to obtain the internal frequency of the SVG device based on the capacitor voltage-frequency droop control; the internal frequency value is compared with the grid strength adaptation parameter K PS Multiply them to get the droop reference angular frequency ω VSG ; The integral calculation module uses the grid nominal angular frequency ω0 and the phase-locked loop reference angular frequency ω PLL and droop reference angular frequency ω VSG Perform integral calculation to obtain the phase angle θ used for Park transformation in the SVG control link; The SVG control module uses the phase angle θ obtained by the integral calculation module to generate a switching signal based on reactive power-voltage droop control, virtual impedance voltage control, AC current inner loop control, Park transformation and intra-phase and inter-phase voltage balancing. The SVG device is controlled by controlling the on and off of the internal switching devices of the SVG device.

8. The device according to claim 7, characterized in that The grid strength adaptation parameter calculation module determines the grid strength adaptation parameter K according to the following method: PLL and K PS The value of In the formula, SCR is the short-circuit ratio, which refers to the system short-circuit capacity divided by the equipment capacity; when SCR is less than 3, the power grid system is a weak grid; when SCR is greater than 3, the power grid system is a strong grid.

9. The device according to claim 7, characterized in that The closed-loop transfer function used by the phase-locked loop module is shown below: In this formula, G PLL (s) is the closed-loop transfer function of the phase-locked loop; s is a complex variable in the transfer function; is the natural frequency; V m is the grid voltage amplitude; k i , k p They are the integral coefficient and proportional coefficient of the phase-locked loop PI controller respectively.

10. The device according to claim 7, characterized in that The capacitor voltage-frequency droop control performed by the capacitor voltage-frequency droop control module is based on the similarity between the dynamics of the DC capacitor and the dynamics of the generator rotor to simulate the synchronous characteristics of the synchronous machine; the transfer function used is as follows: In the formula, G VSG (s) is the transfer function of the square difference of the total capacitance voltage on the DC side-frequency; s is the complex variable in the transfer function; K J is the inertia simulation coefficient; K D is the damping coefficient.

11. The device according to claim 7, characterized in that The SVG control unit obtains the d-axis and q-axis components of the output voltage amplitude reference value based on reactive power-voltage droop control; then the d-axis and q-axis components of the modulated voltage are obtained after being processed by virtual impedance voltage control and AC current inner loop control in sequence. It is then used together with the phase angle θ as the input of the Park transform.

12. A computer device, characterized in that: include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor executes the grid-forming SVG control method suitable for multiple grid strengths as described in any one of claims 1 to 6.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the grid-type SVG control method applicable to multiple power grid strengths according to any one of claims 1 to 6.

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