A control method for grid-type SVG based on DC voltage synchronization

Abstract

The invention discloses a control method for a grid-type SVG based on direct current voltage synchronization, which belongs to the technical field of reactive power compensation control for grid-connected new energy, and comprises the following steps: step S1: introducing a q-axis voltage synchronous control compensation link of the grid-type SVG into the direct current voltage synchronous control link of the grid-type SVG, and updating the initial reference wave phase angle to obtain a final reference wave phase angle; step S2: collecting the three-phase voltage and three-phase current of the grid-connected point of the grid-type SVG, calculating the reactive power value based on the three-phase voltage and the three-phase current, and determining the reference wave amplitude of the SVG; step S3: obtaining a modulation reference wave of the SVG based on the final reference wave phase angle and the reference wave amplitude; step S4: in a PWM modulation link, performing PWM modulation on the modulated reference wave to obtain a control signal for controlling a main circuit of the grid-type SVG; compared with a grid-following control strategy, this method has better stability in a weak grid, and compared with other grid-connecting control strategies, this method is simple to implement and has good stability in a weak grid.

Description

Technical Field

[0001] The present invention relates to the technical field of reactive power compensation control for new energy grid-connected systems, and in particular to a grid-connected SVG control method based on direct current voltage synchronization. Background Art

[0002] In recent years, my country's new energy power production capacity has expanded rapidly, and the construction scale of new energy power generation facilities and their proportion in the energy structure are growing rapidly. The development of new energy power generation not only helps to reduce dependence on fossil fuels and reduce environmental pollution, but also has important significance for optimizing energy structure and achieving energy security. With the advancement of technology and the reduction of costs, new energy power generation methods will occupy a more important position in the future energy supply. New energy power generation methods include solar photovoltaic power generation, wind power generation, hydropower generation, etc. Among them, solar photovoltaic power generation (a power generation method that directly converts sunlight into electrical energy through photovoltaic cells) has its unique advantages compared with other new energy power generation methods. It has the advantages of less geographical restrictions, short construction period, small footprint, low maintenance cost, etc., and the total amount of solar energy is huge. Solar energy is unlimited and will not be exhausted. It is an ideal renewable energy source and is suitable for long-term sustainable development in the future. Therefore, solar photovoltaic power generation technology has developed rapidly and has become one of the main options for replacing fossil fuels. my country has a unique geographical advantage in the photovoltaic power generation industry. More than two-thirds of my country's land area has an annual sunshine time of more than 2,000 hours and an annual average radiation of more than 6,000 GJ / m2. China's terrain is complex and changeable, from plateaus to deserts, from mountains to plains. Different terrains provide diverse installation conditions for photovoltaic power generation, which is conducive to the diversified layout of photovoltaic power generation systems. It can be seen that solar photovoltaic power generation has huge development space and is an extremely important energy supply method in the future.

[0003] As the capacity of photovoltaic power generation increases, the output power of photovoltaic power generation will be affected by environmental factors such as light intensity and temperature, and will be intermittent and volatile, which will cause reactive power flow in the power grid. The flow of reactive power will cause voltage fluctuations and line losses, thus affecting the stability of the power grid and the quality of power supply. SVG (static VAR generator) as a static VAR compensation device can efficiently compensate for the reactive power of the power grid, compensate for the voltage fluctuations caused by photovoltaics, and improve the stability of the power system. At present, most SVGs adopt a grid-following control strategy, which uses PLL (phase-locked loop) to synchronize SVG with the power grid to ensure that its output is consistent with the voltage phase of the power grid. Studies have shown that power electronic converters using a grid-following control strategy may encounter stability problems in weak power grids, especially when the power grid is disturbed. SVG may not be able to provide sufficient reactive support due to the limitations of the control strategy, and it is very easy to vibrate and become unstable, affecting the normal operation of photovoltaic power generation equipment, and even causing oscillation problems in photovoltaic stations, causing large-scale disconnection of photovoltaic generators and serious power grid accidents.

[0004] Different from the grid-following control strategy, the grid-building control strategy uses the control algorithm to generate the grid-connected phase angle, and its grid-connected synchronization process is the spontaneous behavior of the control strategy. Therefore, the power electronic converter using the grid-building control strategy has good adaptability in weak power grids. Relevant researchers from the China Electric Power Research Institute proposed an SVG control strategy based on the grid-building converter. This grid-building control strategy adds DC voltage control on the basis of the VSG control strategy, indirectly controlling the voltage stability of the DC bus capacitor, but it has the disadvantages of complex control strategy, difficult control parameter setting and slow response speed. Relevant researchers from the Economic and Technological Research Institute of State Grid Zhejiang Electric Power Co., Ltd. and Zhejiang University proposed another SVG control strategy based on the grid-building converter. This control strategy essentially controls the energy stored in the DC bus capacitor, thereby achieving voltage stability of the DC bus capacitor. Since the proposed control strategy collects the square value of the DC bus voltage, the small fluctuations of the DC bus voltage will be amplified in the control strategy, which increases the difficulty of parameter setting of the control strategy.

[0005] Therefore, it is necessary to propose a grid-type SVG control method with strong stability in weak power grids and simple control structure. Summary of the invention

[0006] In view of the above-mentioned prior art, the present invention provides a grid-type SVG control method based on DC voltage synchronization, which mainly solves the technical problems existing in the above-mentioned background technology.

[0007] To achieve the above object, the technical solution of the embodiment of the present invention is implemented as follows:

[0008] A method for controlling a grid-type SVG based on DC voltage synchronization includes the following steps:

[0009] Step S1: In the DC voltage synchronization control link of the network type SVG, the q-axis voltage synchronization control compensation link of the network type SVG is introduced to update the initial reference wave phase angle to obtain the final reference wave phase angle;

[0010] Step S2: In the reactive power control link, the three-phase voltage and the three-phase current of the grid connection point of the grid-forming SVG are collected, the reactive power value is calculated based on the three-phase voltage and the three-phase current, and the reference amplitude value of the SVG is determined;

[0011] Step S3: In the reference wave generation link, the modulation reference wave of SVG is obtained based on the final reference wave phase angle and the reference wave amplitude;

[0012] Step S4: In the PWM modulation link, the modulation reference wave of the SVG generated in S3 is subjected to PWM modulation to obtain a control signal for controlling the main circuit of the meshed SVG.

[0013] Optionally, the calculation formula of the initial reference wave phase angle is:

[0014]

[0015] in, is the initial reference wave phase angle of the meshed SVG, is the DC bus voltage reference value, is the DC bus voltage, is the rated value of the angular velocity of the mesh-type SVG, is the DC voltage PI controller transfer function of the meshed SVG, is the proportional control parameter of the DC voltage PI controller, is the integral control parameter of the DC voltage PI controller, is the Laplace operator, For the points segment.

[0016] Optionally, the calculation formula of the q-axis voltage synchronous control compensation link is:

[0017]

[0018] in, is the grid connection point voltage of the grid-type SVG, is the d-axis component of the grid-connected point voltage of the grid-type SVG, is the q-axis component of the grid-connected point voltage of the grid-type SVG, is the transfer function of the variable from the abc coordinate system to the dq coordinate system.

[0019] Optionally, the calculation formula of the final reference wave phase angle is:

[0020]

[0021] in, is the final reference wave phase angle of the meshed SVG, is the q-axis component of the grid-connected point voltage of the grid-type SVG.

[0022] Optionally, in step S1, the initial reference wave phase angle of the meshed SVG is obtained, specifically:

[0023] The DC bus voltage of the meshed SVG is collected, the DC bus voltage is compared with a DC bus voltage reference value and then sent to a DC voltage PI controller, the output signal of the DC voltage PI controller is summed with the angular velocity rated value of the meshed SVG and then sent to an integration link to obtain the initial reference wave phase angle.

[0024] Optionally, in step S1, determining the final reference wave phase angle is specifically:

[0025] The grid-connected point voltage of the grid-forming SVG is collected, and the grid-connected point voltage is sent to a transfer function that converts the abc coordinate system to the dq coordinate system to obtain the q-axis component of the grid-connected point voltage of the grid-forming SVG. The output signal of the DC voltage PI controller is summed with the q-axis component of the grid-connected point voltage and the rated value of the angular velocity of the grid-forming SVG, and then sent to an integration link to obtain the final reference wave phase angle.

[0026] Optionally, the calculation formula of the reactive power control link is:

[0027]

[0028] in, is the reference amplitude value of the mesh-type SVG, is the reactive power value of the grid-type SVG, Reactive power reference value of grid-type SVG, is the rated value of the reference amplitude of the mesh-type SVG, is the transfer function of the reactive power PI controller of the networked SVG, is the proportional control parameter of the reactive power PI controller, is the integral control parameter of the reactive power PI controller, For the points segment.

[0029] Optionally, the determining of the reference amplitude value of SVG is specifically:

[0030] The three-phase voltage and the three-phase current of the grid-connected point of the grid-forming SVG are collected, and a reactive power value is calculated based on the three-phase voltage and the three-phase current. The reactive power value is compared with a reactive power reference value and then sent to a reactive power PI controller. The reference amplitude value is obtained by summing the output signal of the reactive power PI controller with the rated value of the reference amplitude value of the grid-forming SVG.

[0031] The beneficial effects of the present invention are as follows: a meshing type SVG control method based on DC voltage synchronization provided by the present invention obtains an initial reference wave phase angle based on a DC voltage synchronization control link, introduces a q-axis voltage synchronization control compensation link to obtain a final reference wave phase angle, and obtains a reference wave amplitude in a reactive power control link, and obtains a modulated reference wave through the obtained final reference wave phase angle and reference wave amplitude, and the obtained modulated reference wave is modulated by PWN to obtain a control signal of the meshing type SVG to control the main circuit of the meshing type SVG; a meshing type SVG control method based on DC voltage synchronization provided by the present invention, compared with a grid-following control strategy, the meshing type SVG control method provided by the present invention has better stability in a weak power grid, and in addition, compared with other meshing type control strategies, the meshing type SVG control method based on DC voltage synchronization provided by the present invention has the advantages of simple control structure, few control parameters, and fast response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of a meshed SVG control method based on DC voltage synchronization in an embodiment of the present invention;

[0033] Figure 2 This is a main circuit topology diagram of a meshed SVG control method based on DC voltage synchronization in an embodiment of the present invention;

[0034] Figure 3 It is a structural schematic diagram of a DC voltage synchronous control link of a meshed SVG and a q-axis voltage synchronous control compensation link of a meshed SVG in an embodiment of the present invention;

[0035] Figure 4 1 is a schematic structural diagram of a reactive power control link of a meshed SVG in an embodiment of the present invention;

[0036] Figure 5 It is an overall block diagram of a network-type SVG control method based on DC voltage synchronization in an embodiment of the present invention;

[0037] Figure 6 It is a structural diagram of the traditional mesh-type SVG control method;

[0038] Figure 7 is a grid-connected SVG waveform in the embodiment of the present invention;

[0039] Figure 8 It is a grid-following SVG grid-connected waveform in the prior art. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings and specific embodiments of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, the expression "some embodiments" is related to, which describes a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0041] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0042] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and the scope of the present invention will be fully conveyed to those skilled in the art. And the purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms of "one", "one" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "compose" and / or "include" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0043] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0044] In order to fully understand the present invention, a detailed structure will be proposed in the following description to illustrate the technical solution proposed by the present invention. The optional embodiments of the present invention are described in detail as follows, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0045] Please refer to the attached Figure 2 , Figure 2 The figure shows a main circuit topology of a meshed SVG based on DC voltage synchronization. is the DC bus capacitance, and They are the filter inductor and filter capacitor of the LC filter respectively. and are the equivalent resistance and equivalent inductance of the power grid respectively. The voltage across the DC bus capacitor is the DC bus voltage The current flowing through the filter inductor is the three-phase current of the grid-connected point of the grid-type SVG. The connection point of the filter inductor and the filter capacitor is the three-phase voltage of the grid connection point of the grid-type SVG , the grid voltage is .

[0046] Please refer to the attached Figure 1 The present invention provides a grid-type SVG control method based on DC voltage synchronization, comprising the following steps:

[0047] Step S1: In the DC voltage synchronization control link of the network type SVG, the q-axis voltage synchronization control compensation link of the network type SVG is introduced to update the initial reference wave phase angle to obtain the final reference wave phase angle;

[0048] Specifically, the calculation formula of the initial reference wave phase angle is:

[0049]

[0050] in, is the initial reference wave phase angle of the meshed SVG, is the DC bus voltage reference value, is the DC bus voltage, is the rated value of the angular velocity of the mesh-type SVG, is the DC voltage PI controller transfer function of the meshed SVG, is the proportional control parameter of the DC voltage PI controller, is the integral control parameter of the DC voltage PI controller, is the Laplace operator, For the points link;

[0051] Please refer to the attached Figure 3 , obtain the initial reference wave phase angle of the grid-type SVG, the specific method is:

[0052] The DC bus voltage of the meshed SVG is collected, the DC bus voltage is compared with a DC bus voltage reference value and then sent to a DC voltage PI controller, the output signal of the DC voltage PI controller is summed with the angular velocity rated value of the meshed SVG and then sent to an integration link to obtain the initial reference wave phase angle;

[0053] The q-axis voltage synchronous control compensation link is expressed as:

[0054]

[0055] in, is the grid connection point voltage of the grid-type SVG, is the d-axis component of the grid-connected point voltage of the grid-type SVG, is the q-axis component of the grid-connected point voltage of the grid-type SVG, is the transfer function of the variable from the abc coordinate system to the dq coordinate system;

[0056] The calculation formula of the final reference wave phase angle is:

[0057]

[0058] in, is the final reference wave phase angle of the meshed SVG, is the q-axis component of the grid-connected point voltage of the grid-type SVG;

[0059] Please refer to the attached Figure 3 , determine the final reference wave phase angle, the specific method is:

[0060] The grid-connected point voltage of the grid-forming SVG is collected, and the grid-connected point voltage is sent to a transfer function that converts the abc coordinate system to the dq coordinate system to obtain the q-axis component of the grid-connected point voltage of the grid-forming SVG. The output signal of the DC voltage PI controller is summed with the q-axis component of the grid-connected point voltage and the rated value of the angular velocity of the grid-forming SVG, and then sent to an integration link to obtain the final reference wave phase angle.

[0061] The process of generating the final reference wave phase angle includes generating the initial reference wave phase angle in the DC voltage synchronous control link and introducing the q-axis voltage synchronous control compensation link to generate the final reference wave phase angle, specifically: the DC bus voltage is compared with the DC bus voltage reference value and then sent to the DC voltage PI controller, and then the output signal of the DC voltage PI controller is summed with the angular velocity rated value and then integrated to obtain the initial reference wave phase angle, and then the initial reference wave phase angle and the grid-connected point voltage are sent to the transfer function converted from the abc coordinate system to the dq coordinate system to obtain the q-axis component of the grid-connected point voltage of the grid-connected SVG; and then the q-axis component of the grid-connected point voltage, the output signal of the DC voltage PI controller, and the angular velocity rated value are summed and then integrated to obtain the final reference wave phase angle;

[0062] By first obtaining the initial reference wave phase angle, and then updating the reference wave phase angle to obtain the final reference wave phase angle, the purpose is to use the DC voltage control link as the main generation path of the reference wave phase angle to achieve the stability of the grid voltage. The q-axis voltage synchronous control compensation link further updates the reference wave phase angle as an auxiliary method to stabilize the grid voltage, further achieving the synchronization of the grid-type SVG output voltage and the grid voltage to ensure the stable operation of the grid. By generating the initial reference wave phase angle and the final reference wave phase angle, it can further ensure that the output voltage is consistent with the grid voltage phase, maintaining the stability and reliability of the grid voltage.

[0063] The DC bus voltage is the voltage on the DC side of the grid-type SVG device. After being adjusted by the DC voltage PI controller, the DC bus voltage can be maintained stable so that the DC bus voltage can be stabilized at the DC bus voltage reference value. The grid connection point voltage is the voltage at the connection point between the grid-type SVG and the grid. It is necessary to ensure that the grid connection point voltage is synchronized with the grid voltage to ensure that the grid-type SVG can smoothly exchange energy with the grid. The collected grid connection point voltage is converted into the d-axis component of the grid connection point voltage and the q-axis component of the grid connection point voltage through coordinate transformation. Then, the output signal of the DC voltage PI controller, the q-axis component of the grid connection point voltage, and the angular velocity rated value of the grid-type SVG are summed up, and the final reference wave phase angle is obtained through the integral link. The final reference wave phase angle determines the phase of the output voltage of the grid-type SVG to achieve synchronization with the grid voltage. By using the DC voltage synchronization control link and the q-axis voltage synchronization control compensation link, the grid-type SVG can achieve synchronization with the grid voltage without the help of a phase-locked loop.

[0064] Step S2: In the reactive power control link, the three-phase voltage and the three-phase current of the grid connection point of the grid-forming SVG are collected, the reactive power value is calculated based on the three-phase voltage and the three-phase current, and the reference amplitude value of the SVG is determined;

[0065] The calculation formula of the reactive power control link is:

[0066]

[0067] in, is the reference amplitude value of the mesh-type SVG, is the reactive power value of the grid-type SVG, Reactive power reference value of grid-type SVG, is the rated value of the reference amplitude of the mesh-type SVG, is the transfer function of the reactive power PI controller of the networked SVG, is the proportional control parameter of the reactive power PI controller, is the integral control parameter of the reactive power PI controller, For the points segment.

[0068] Please refer to the attached Figure 4 , the specific method for determining the reference amplitude value is as follows:

[0069] Collecting the three-phase voltage and the three-phase current of the grid connection point of the grid-forming SVG, calculating reactive power based on the three-phase voltage and the three-phase current, performing a difference comparison between the reactive power and a reactive power reference value and then sending the difference to a reactive power PI controller, and performing a summation between the output signal of the reactive power PI controller and the rated value of the reference amplitude value of the grid-forming SVG to obtain the reference amplitude value;

[0070] After comparing the calculated reactive power with the reactive power reference value, an error signal is generated. After the error signal is sent to the reactive power PI controller, the PI controller adjusts its output according to the error signal, thereby reducing the reactive power deviation and maintaining the voltage stability of the power grid. The output signal of the reactive power PI controller is added to the rated value of the reference amplitude of the grid-forming SVG to obtain the reference amplitude value. The reference amplitude value of the final output is adjusted in the above manner to control the reactive power value that needs to be compensated by the SVG output, thereby ensuring that the output of the grid-forming SVG matches the demand of the power grid and realizing dynamic reactive power compensation.

[0071] Please refer to the attached Figure 5 , step S3: in the reference wave generation link, based on the final reference wave phase angle and the reference wave amplitude to obtain the modulation reference wave of SVG;

[0072] Step S4: In the PWM modulation link, the modulation reference wave is subjected to PWM modulation to obtain a control signal for controlling the main circuit of the meshed SVG;

[0073] The control signal of the main circuit is generated through PWM modulation. The control signal is used to control the switching state of the main circuit of the grid-forming SVG to achieve effective conversion and control of electric energy while reducing harmonics and grid losses.

[0074] Please refer to the attached Figure 6 To Attachment Figure 8 In order to further demonstrate the implementation effect of the present invention, a comparative simulation is performed between the mesh-forming SVG control method proposed in the present invention and the traditional mesh-following SVG control method. Figure 6 The figure shows the traditional grid-following SVG control method, setting the grid equivalent inductance Increase, simulating the transformation of the power grid from a strong power grid to a weak power grid, Figure 7 The grid-connected voltage and current waveforms of the grid-connected SVG control method based on DC voltage synchronization provided by the present invention are as follows: Figure 8 The grid-connected voltage and current waveforms of the traditional grid-following SVG control method are shown in Figure 2. Figure 7 It can be seen that the grid-type SVG control method based on DC voltage synchronization provided by the present invention is that as time goes by, the grid waveform and the current waveform are very stable, and Figure 8 In the traditional grid-following SVG control method, as time goes by, the voltage waveform and current waveform become obviously chaotic, indicating that the control effect of the grid-following SVG is not good. The output of the grid-following SVG cannot keep pace with the grid voltage, resulting in unstable voltage and current waveforms. Therefore, through Figure 7 and Figure 8 From the comparison waveforms, it can be seen that the grid-type SVG control method provided by the present invention has better stability in a weak power grid.

[0075] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. The protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for controlling a grid-type SVG based on DC voltage synchronization, characterized in that: The following steps are involved: Step S1: In the DC voltage synchronization control link of the network type SVG, the q-axis voltage synchronization control compensation link of the network type SVG is introduced to update the initial reference wave phase angle to obtain the final reference wave phase angle; Step S2: In the reactive power control link, the three-phase voltage and the three-phase current of the grid connection point of the grid-forming SVG are collected, the reactive power value is calculated based on the three-phase voltage and the three-phase current, and the reference amplitude value of the SVG is determined; Step S3: In the reference wave generation link, the modulation reference wave of SVG is obtained based on the final reference wave phase angle and the reference wave amplitude; Step S4: In the PWM modulation link, the modulation reference wave is subjected to PWM modulation to obtain a control signal for controlling the main circuit of the meshed SVG; The calculation formula of the initial reference wave phase angle is: in, is the initial reference wave phase angle of the meshed SVG, is the DC bus voltage reference value, is the DC bus voltage, is the rated value of the angular velocity of the mesh-type SVG, is the DC voltage PI controller transfer function of the meshed SVG, is the proportional control parameter of the DC voltage PI controller, is the integral control parameter of the DC voltage PI controller, is the Laplace operator, For the points link; The calculation formula of the q-axis voltage synchronous control compensation link is: in, is the grid connection point voltage of the grid-type SVG, is the d-axis component of the grid-connected point voltage of the grid-type SVG, is the q-axis component of the grid-connected point voltage of the grid-type SVG, is the transfer function of the variable from the abc coordinate system to the dq coordinate system; The calculation formula of the final reference wave phase angle is: in, is the final reference wave phase angle of the meshed SVG, is the q-axis component of the grid-connected point voltage of the grid-type SVG.

2. A method for controlling a meshed SVG based on DC voltage synchronization according to claim 1, characterized in that: In step S1, the initial reference wave phase angle of the meshed SVG is obtained, specifically: The DC bus voltage of the meshed SVG is collected, the DC bus voltage is compared with a DC bus voltage reference value and then sent to a DC voltage PI controller, the output signal of the DC voltage PI controller is summed with the angular velocity rated value of the meshed SVG and then sent to an integration link to obtain the initial reference wave phase angle.

3. A method for controlling a meshed SVG based on DC voltage synchronization according to claim 2, characterized in that: In step S1, the final reference wave phase angle is determined, specifically: The grid-connected point voltage of the grid-forming SVG is collected, and the grid-connected point voltage is sent to a transfer function that converts the abc coordinate system to the dq coordinate system to obtain the q-axis component of the grid-connected point voltage of the grid-forming SVG. The output signal of the DC voltage PI controller is summed with the q-axis component of the grid-connected point voltage and the rated value of the angular velocity of the grid-forming SVG, and then sent to an integration link to obtain the final reference wave phase angle.

4. A method for controlling a meshed SVG based on DC voltage synchronization according to claim 1, characterized in that: The calculation formula of the reactive power control link is: in, is the reference amplitude value of the mesh-type SVG, is the reactive power value of the grid-type SVG, Reactive power reference value of grid-type SVG, is the rated value of the reference amplitude of the mesh-type SVG, is the transfer function of the reactive power PI controller of the networked SVG, is the proportional control parameter of the reactive power PI controller, is the integral control parameter of the reactive power PI controller, For the points segment.

5. A method for controlling a meshed SVG based on DC voltage synchronization according to claim 4, characterized in that: The reference amplitude value of SVG is determined as follows: The three-phase voltage and the three-phase current of the grid-connected point of the grid-forming SVG are collected, and a reactive power value is calculated based on the three-phase voltage and the three-phase current. The reactive power value is compared with a reactive power reference value and then sent to a reactive power PI controller. The reference amplitude value is obtained by summing the output signal of the reactive power PI controller with the rated value of the reference amplitude value of the grid-forming SVG.

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