Voltage source converter grid-connected control method and system under weak grid connection conditions

Abstract

The present invention discloses a voltage source type converter grid-connected control method and system under weak grid connection conditions, including: establishing a mathematical model according to the typical topology of the voltage source type converter grid-connected system, linearizing and simplifying the mathematical model, and obtaining the output current small signal mathematical model of the voltage source type converter grid-connected system; for the output current small signal mathematical model, extracting the control current reference value compensation loop gain; adding the current reference value compensation loop gain to the current loop reference value, decoupling the voltage source type converter grid-connected system into a first-order loop related only to the current loop parameters, and realizing the voltage source type converter grid-connected control. The present invention can compensate for the dynamic error introduced by the phase-locked loop dynamics and the AC system impedance by adding feedforward control to the current loop reference value of the converter grid-connected system, thereby realizing the decoupling of the d-axis control and the q-axis control of the converter grid-connected system, and effectively improving the stability of the grid-connected system.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic equipment grid-connected system control, and in particular to a voltage source converter grid-connected control method and system under weak grid connection conditions. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] A weak power grid refers to a system with an AC system equivalent impedance that is too large, and a short-circuit ratio is usually used. It is generally believed that an AC system with a short-circuit ratio of 2 to 3 is a weak AC system, also known as a weak power grid; an AC system with a short-circuit ratio lower than 2 is an extremely weak AC system, also known as an extremely weak power grid. When a voltage source converter is connected to a weak AC system, there is a strong interaction between its typical control link and the weak AC system. In severe cases, it will cause the grid-connected system to become unstable, endangering the safe and stable operation of the grid-connected system.

[0004] The phase-locked loop is the key control link that causes the instability of the voltage source converter connected to the AC system. By optimizing the control parameters and control structure to weaken or compensate the output error of the phase-locked loop after the grid-connected system is disturbed, the stability of the grid-connected system can be effectively improved. Existing studies generally propose control parameter and structure optimization methods to enhance the stability of the grid-connected system from three aspects: control parameter optimization, phase-locked loop structure optimization, and additional feedforward compensation control.

[0005] The core idea of ​​the control parameter optimization method is to reshape the converter output characteristics by optimizing the control link parameters, thereby enhancing the grid-connected stability of the voltage source converter system. Its advantage is that it does not need to change the classic double closed-loop control strategy and phase-locked loop control structure of the voltage source converter control, but it needs to balance the relationship between the control system response speed and stability and consider the relationship between the various control links of the converter;

[0006] The core idea of ​​the control structure optimization method is to enhance the grid-connected stability of the voltage source converter system by reshaping the impedance characteristics of the phase-locked loop control link or designing reasonable additional control. Among them, the method of reshaping the phase-locked loop output characteristics mainly enhances the self-stability of the phase-locked loop to improve the overall stability of the grid-connected system. It can be achieved by adding active damping to the phase-locked loop, using a symmetrical structure phase-locked loop, or using virtual synchronous control. Its advantage is that it only needs to re-adjust the phase-locked loop control parameters without changing the overall structure of the dual closed-loop control; the additional control law is to compensate for the phase-locked loop dynamics by adding virtual impedance or feedforward compensation structures to the dual closed-loop control structure, and by improving the stability of the entire grid-connected system. However, since the additional control link changes the control structure of the grid-connected system, the control parameters of the grid-connected system need to be redesigned.

[0007] The main problems of existing feedforward compensation control methods are: high control design complexity and relatively complex parameter design. Existing additional feedforward compensation control methods generally change the control structure of the system, resulting in changes in the amplitude-frequency characteristics of the entire control loop, increasing the complexity of the control system, and requiring the control parameters of the grid-connected system to be redesigned. Summary of the invention

[0008] In order to solve the above problems, the present invention proposes a voltage source converter grid-connected control method and system under weak grid connection conditions. By adding a feedforward link to the current loop reference value to compensate for the dynamic error of the phase-locked loop, the feedback branch error caused by the phase-locked loop dynamics and the AC system impedance can be directly compensated, and then the voltage source converter grid-connected system is decoupled into two independent first-order systems, meeting the requirements of safe and stable operation of the converter when it is connected to a weak AC system.

[0009] In some embodiments, the following technical solutions are adopted:

[0010] A voltage source converter grid-connected control method under weak grid connection conditions, comprising:

[0011] A mathematical model is established according to a typical topology of a voltage source converter grid-connected system, and the mathematical model is linearized and simplified to obtain a small signal mathematical model of an output current of the voltage source converter grid-connected system;

[0012] For the output current small signal mathematical model, extracting the control current reference value compensation loop gain;

[0013] The current reference value compensation loop gain is added to the current loop reference value, and the voltage source converter grid-connected system is decoupled into a first-order loop only related to the current loop parameters, thereby realizing the voltage source converter grid-connected control.

[0014] As an optional implementation, a small signal mathematical model of the output current of the voltage source converter grid-connected system is obtained, specifically:

[0015]

[0016]

[0017] Where s represents the Laplace operator; the superscripts “gf” and “cf” represent the electrical signals in the main circuit coordinate system and the control coordinate system, respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll G is the phase angle disturbance of the phase-locked loop output; CL represents the current loop transfer function; Id0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system.

[0018] As an optional implementation, for the output current small signal mathematical model, the control current reference value compensation loop gain is extracted, specifically:

[0019]

[0020] Among them, K pgsc With K igsc Represent the current loop proportional coefficient and integral coefficient respectively, s represents the Laplace operator; R eq Represents the equivalent resistance of the AC system, I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively.

[0021] As an optional implementation, the current reference value compensation loop gain is added to the current loop reference value, specifically:

[0022]

[0023]

[0024] Where s represents the Laplace operator; the superscripts “gf” and “cf” represent the electrical signals in the main circuit coordinate system and the control coordinate system, respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll G is the phase angle disturbance of the phase-locked loop output; CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system, G dcd , G dcq The control current reference values ​​for the d-axis and q-axis are compensation loop gains respectively.

[0025] As an optional implementation, before establishing a mathematical model based on a typical topology of a voltage source converter grid-connected system, the following settings are made:

[0026] The voltage feedforward filter time constant and the converter control link equivalent delay are very small, and it is approximately considered that the voltage feedforward filter transfer function and the converter delay equivalent link G f ≈1, G d ≈1;

[0027] Since the outer loop control bandwidth is generally much smaller than the inner loop control bandwidth, it can be considered that the outer loop control of the grid-connected converter has not responded within the current loop bandwidth time scale, so the impact of the outer loop dynamics on the grid-connected system is ignored.

[0028] In other embodiments, the following technical solutions are adopted:

[0029] The voltage source converter grid-connected control system under weak grid connection conditions includes:

[0030] A mathematical modeling module is used to establish a mathematical model according to a typical topology of a voltage source converter grid-connected system, linearize and simplify the mathematical model, and obtain a small signal mathematical model of an output current of the voltage source converter grid-connected system;

[0031] A compensation loop gain calculation module, used for extracting a control current reference value compensation loop gain for the output current small signal mathematical model;

[0032] The grid-connected control module is used to add the current reference value compensation loop gain to the current loop reference value, decouple the voltage source converter grid-connected system into a first-order loop related only to the current loop parameters, and realize the voltage source converter grid-connected control.

[0033] In other embodiments, the following technical solutions are adopted:

[0034] The current reference value is added to the current loop reference value to compensate for the loop gain, specifically:

[0035]

[0036]

[0037] Where s represents the Laplace operator; the superscripts “gf” and “cf” represent the electrical signals in the main circuit coordinate system and the control coordinate system, respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll G is the phase angle disturbance of the phase-locked loop output; CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; Req , L eq Represents the equivalent resistance and equivalent inductance of the AC system, G dcd , G dcq The control current reference values ​​for the d-axis and q-axis are compensation loop gains respectively.

[0038] In other embodiments, the following technical solutions are adopted:

[0039] A terminal device includes a processor and a memory, wherein the processor is used to implement various instructions; the memory is used to store multiple instructions, and the instructions are suitable for being loaded by the processor and executing the above-mentioned voltage source converter grid-connected control method under weak grid connection conditions.

[0040] In other embodiments, the following technical solutions are adopted:

[0041] A computer-readable storage medium stores a plurality of instructions, wherein the instructions are suitable for being loaded by a processor of a terminal device and executing the above-mentioned voltage source converter grid-connected control method under weak grid connection conditions.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention adds feedforward control to the current loop reference value of the inverter grid-connected system, thereby compensating for the dynamic error introduced by the phase-locked loop dynamics and the AC system impedance, thereby achieving decoupling of the d-axis control and the q-axis control of the inverter grid-connected system, and effectively improving the stability of the grid-connected system.

[0044] At the same time, the current reference value feedforward compensation control also has the advantage of not requiring parameter design and only requiring the addition of compensation branches to enhance the stability of the grid-connected system. This is of great significance for optimizing the control structure to ensure the safe and stable operation of the converter when connected to a weak power grid.

[0045] Other features and advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of a typical voltage source converter grid-connected system;

[0047] Figure 2 It is the small signal block diagram of the current inner loop;

[0048] Figure 3 It is a small signal block diagram of a grid-connected system using a feedforward compensation decoupling method in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0051] Embodiment 1

[0052] In one or more embodiments, a voltage source converter grid-connected control method under weak grid connection conditions is disclosed. For the voltage source converter grid-connected system, an analytical transfer function model and an output current small signal model are established, the feedback loop gain caused by the phase-locked loop dynamics and the AC system impedance coupling is extracted, and a feedforward compensation loop is added to the reference value to enhance the stability of the grid-connected system.

[0053] The method of this embodiment specifically includes the following process:

[0054] (1) A mathematical model is established based on the typical topology of the voltage source converter grid-connected system, and the mathematical model is linearized and simplified to obtain a small signal mathematical model of the output current of the voltage source converter grid-connected system;

[0055] Typical voltage source converter grid-connected systems are as follows: Figure 1 As shown in the figure, the typical structure of the voltage source converter grid-connected system is divided into a main circuit module, a phase-locked loop module, a current loop module and a modulation module. Among them, the phase-locked loop module is used to extract the frequency of the AC system; the current loop is used to generate a modulation signal to achieve the control target of the grid-connected system; the modulation module generates a trigger pulse from the modulation signal to control the voltage prototype converter to output an AC voltage.

[0056] Before establishing a mathematical model based on the typical topology of the inverter grid-connected system, the following assumptions need to be made:

[0057] The voltage feedforward filter time constant and the converter control link equivalent delay are very small, and it is approximately considered that the voltage feedforward filter transfer function and the converter delay equivalent link G f ≈1, G d ≈ 1 ;

[0058] Since the outer loop control bandwidth is generally much smaller than the inner loop control bandwidth, it can be considered that the outer loop control of the grid-connected converter has not responded within the current loop bandwidth time scale, so the impact of the outer loop dynamics on the grid-connected system is ignored.

[0059] According to the typical topological structure mathematical model of the inverter grid-connected system, it is easy to obtain the output current small signal model of the inverter grid-connected system:

[0060]

[0061] Where s represents the Laplace operator; the superscripts “gf” and “cf” represent the electrical signals in the main circuit coordinate system and the control coordinate system, respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll G is the phase angle disturbance of the phase-locked loop output; CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system.

[0062] According to the output current small signal model of the inverter grid-connected system, the corresponding current closed-loop small signal block diagram can be obtained, as shown in Figure 2 shown.

[0063] Depend on Figure 2 It can be seen that if the current loop reference value fluctuates Δi cfsdref , Δi cfsqref When the disturbance signal passes through the current loop transfer function link and the main circuit parameters, it is fed back and input through the A loop and B loop respectively in the AC system impedance and phase-locked loop.

[0064] This is because the phase-locked loop will have a phase angle tracking error after the system is disturbed, and there will be a relative phase angle error between the control coordinate system established by the phase angle of the phase-locked loop output and the main circuit coordinate system established by the actual voltage phase angle of the grid-connected point. Under the action of the equivalent impedance of the AC system, the coordinate system offset caused by the phase angle output error of the phase-locked loop will act on the corresponding current control loop through the dq axis feedback loop A and feedback loop B respectively. The smaller the strength of the AC grid, the larger the equivalent impedance of the corresponding AC grid. Therefore, under the same control parameters, the current feedback branch has a greater impact on the output current. This is also the reason why the phase-locked loop control link is prone to interaction when the AC system impedance is large, causing system instability.

[0065] (2) For the output current small signal mathematical model, extract the control current reference value compensation loop gain;

[0066] In this embodiment, according to the grid-connected converter output current model, the dq axis control current reference value compensation loop gain G of the converter grid-connected system is calculated respectively. dcd With G dcq , the feedforward compensation control model of voltage source converter under weak grid connection condition is obtained:

[0067]

[0068] Among them, K pgsc With K igsc They represent the proportional coefficient and integral coefficient of the current loop respectively.

[0069] (4) Combination Figure 3 , add the current reference compensation loop gain G to the input d-axis current reference value and q-axis current reference value respectively dcd With G dcq , directly compensates for the coupling effect caused by the interaction between the AC system and the phase-locked loop, and then decouples the voltage source converter grid-connected system control link into a current loop transfer function G CL The equivalent resistance and inductance R of the converter eq , L eq The associated first-order decoupled loop.

[0070] Specifically, the current reference value is added to the current loop reference value to compensate for the loop gain, specifically:

[0071]

[0072]

[0073] Since the last two terms in the above two equations are essentially the same, they can be canceled out. Adding the current reference to the current loop reference to compensate for the loop gain becomes:

[0074]

[0075] When the operating status of the grid-connected system is known, the voltage source converter grid-connected system can be decoupled into a first-order loop related only to the current loop parameters by adding feedforward compensation branches to the dq axis control loops.

[0076] Without the need to redesign control system parameters, the stability of the grid-connected system is effectively improved.

[0077] Embodiment 2

[0078] In one or more embodiments, a voltage source converter grid-connected control system under weak grid connection conditions is disclosed, comprising:

[0079] A mathematical modeling module is used to establish a mathematical model according to a typical topology of a voltage source converter grid-connected system, linearize and simplify the mathematical model, and obtain a small signal mathematical model of an output current of the voltage source converter grid-connected system;

[0080] A compensation loop gain calculation module, used for extracting a control current reference value compensation loop gain for the output current small signal mathematical model;

[0081] The grid-connected control module is used to add the current reference value compensation loop gain to the current loop reference value, decouple the voltage source converter grid-connected system into a first-order loop related only to the current loop parameters, and realize the voltage source converter grid-connected control.

[0082] In this embodiment, the current reference value is added to the current loop reference value to compensate for the loop gain, specifically:

[0083]

[0084]

[0085] Where s represents the Laplace operator; the superscripts “gf” and “cf” represent the electrical signals in the main circuit coordinate system and the control coordinate system, respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll G is the phase angle disturbance of the phase-locked loop output; CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system, G dcd , G dcq The control current reference values ​​for the d-axis and q-axis are compensation loop gains respectively.

[0086] Embodiment 3

[0087] In one or more embodiments, a terminal device is disclosed, including a server, the server including a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the voltage source converter grid-connected control method under weak grid connection conditions in Example 1 when executing the program. For the sake of brevity, it will not be described here.

[0088] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0089] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0090] In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or an instruction in the form of software.

[0091] Embodiment 4

[0092] In one or more embodiments, a computer-readable storage medium is disclosed, in which a plurality of instructions are stored, wherein the instructions are suitable for being loaded by a processor of a terminal device and executing the voltage source converter grid-connected control method under weak grid connection conditions described in Example 1.

[0093] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A voltage source converter grid-connected control method under weak grid connection conditions, characterized in that: include: A mathematical model is established according to the typical topology of the voltage source converter grid-connected system, and the mathematical model is linearized and simplified to obtain the output current small signal mathematical model of the voltage source converter grid-connected system, which is specifically: Where s represents the Laplace operator; the superscripts "gf" and "cf" represent the electrical signals in the main circuit coordinate system and the control coordinate system respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll is the phase angle disturbance of the phase-locked loop output; G CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system; For the output current small signal mathematical model, the control current reference value compensation loop gain is extracted, specifically: Among them, K pgsc With K igsc Represent the current loop proportional coefficient and integral coefficient respectively, s represents the Laplace operator; R eq Represents the equivalent resistance of the AC system, I d0 ,I q0 Represent the steady-state components of d-axis current and q-axis current respectively; The current reference value is added to the current loop reference value to compensate for the loop gain, specifically: Where s represents the Laplace operator; the superscripts "gf" and "cf" represent the electrical signals in the main circuit coordinate system and the control coordinate system respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll is the phase angle disturbance of the phase-locked loop output; G CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system, G dcd , G dcq are the control current reference value compensation loop gains of the d-axis and q-axis respectively; The voltage source converter grid-connected system is decoupled into a first-order loop only related to the current loop parameters, so as to realize the voltage source converter grid-connected control.

2. The method for controlling the voltage source converter connected to the grid under the condition of weak grid connection according to claim 1, characterized in that: Before establishing a mathematical model based on the typical topology of the voltage source converter grid-connected system, the following settings are made: The voltage feedforward filter time constant and the converter control link equivalent delay are very small, and it is approximately considered that the voltage feedforward filter transfer function and the converter delay equivalent link G f ≈1, G d ≈1; Since the outer loop control bandwidth is generally much smaller than the inner loop control bandwidth, it can be considered that the outer loop control of the grid-connected converter has not responded within the current loop bandwidth time scale, so the impact of the outer loop dynamics on the grid-connected system is ignored.

3. A voltage source converter grid-connected control system under weak grid connection conditions, characterized in that: include: The mathematical modeling module is used to establish a mathematical model according to the typical topology of the voltage source converter grid-connected system, linearize and simplify the mathematical model, and obtain the output current small signal mathematical model of the voltage source converter grid-connected system, which is specifically: Where s represents the Laplace operator; the superscripts "gf" and "cf" represent the electrical signals in the main circuit coordinate system and the control coordinate system respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll is the phase angle disturbance of the phase-locked loop output; G CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system; The compensation loop gain calculation module is used to extract the control current reference value compensation loop gain for the output current small signal mathematical model, specifically: Among them, K pgsc With K igsc Represent the current loop proportional coefficient and integral coefficient respectively, s represents the Laplace operator; R eq Represents the equivalent resistance of the AC system, I d0 ,I q0 Represent the steady-state components of d-axis current and q-axis current respectively; The grid-connected control module is used to add the current reference value to the current loop reference value to compensate for the loop gain, specifically: Where s represents the Laplace operator; the superscripts "gf" and "cf" represent the electrical signals in the main circuit coordinate system and the control coordinate system respectively; Δi cfsdref , Δi cfsqref , Δi gfsd and Δi gfsq Respectively represent the d-axis and q-axis current reference values ​​in the reference coordinate system and the d-axis and q-axis current responses in the main circuit coordinate system; Δθ pll is the phase angle disturbance of the phase-locked loop output; G CL represents the current loop transfer function; I d0 ,I q0 Represent the steady-state components of the d-axis current and the q-axis current respectively; R eq , L eq Represents the equivalent resistance and equivalent inductance of the AC system, G dcd , G dcq are the control current reference value compensation loop gains of the d-axis and q-axis respectively; The voltage source converter grid-connected system is decoupled into a first-order loop only related to the current loop parameters, so as to realize the voltage source converter grid-connected control.

4. A terminal device, comprising a processor and a memory, wherein the processor is used to implement each instruction; and the memory is used to store multiple instructions, characterized in that: The instructions are suitable for being loaded by a processor and executing the voltage source converter grid-connected control method under weak grid connection conditions as described in any one of claims 1-2.

5. A computer-readable storage medium storing a plurality of instructions, characterized in that: The instructions are suitable for being loaded by a processor of a terminal device and executing the voltage source converter grid-connected control method under weak grid connection conditions as described in any one of claims 1-2.

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