Stable control method and system for high-voltage direct-current power transmission grid-connected system

Abstract

The invention discloses a high-voltage direct-current power transmission grid-connected system stability control method and system, and relates to the technical field of power system control, and the method comprises the following steps: collecting the numerical information of a high-voltage direct-current power transmission system, and calculating the numerical information to obtain a receiving end output d-axis current reference value and a receiving end output q-axis current reference value; calculating a d-axis current control value through the d-axis current reference value, and then obtaining a d-axis modulation signal; calculating a q-axis current control value through the q-axis current reference value, and then obtaining a q-axis modulation signal; and performing grid-connected current control according to the d-axis modulation signal and the q-axis modulation signal, and driving a receiving-end converter of the high-voltage direct-current power transmission grid-connected system. According to the method, the new energy side output impedance remodeling can be realized without introducing an additional device, the dynamic performance of the high-voltage direct-current power transmission system is not influenced, and the stability of the high-voltage direct-current power transmission grid-connected system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and in particular to a method and system for stabilizing and controlling a high-voltage direct current transmission grid-connected system. Background Art

[0002] As the proportion of renewable energy such as wind power and photovoltaic power in the power system gradually increases, the intermittent and unstable nature of these new energy sources has brought great challenges to the stable operation of the power grid. In particular, when reactive power compensation devices participate in the process of new energy grid connection via high-voltage direct current transmission, the stability of the system is particularly prominent.

[0003] High-voltage direct current transmission technology has become one of the key technologies for large-scale transmission of new energy due to its advantages such as low transmission loss over long distances, flexible control, and the ability to solve grid-connected problems that AC systems cannot solve. However, the dynamic characteristics of the high-voltage direct current transmission system and the high-frequency switching action of power electronic devices may cause instability in the system in the low-frequency band. The stability of the power system can be analyzed by the impedance characteristics of the system, which are generally determined by the physical characteristics of the transmission line and power electronic devices. However, in the direct current transmission grid-connected system, the dynamic behavior of the power electronic converter has a significant impact on the impedance characteristics of the system. Especially under weak grid conditions, the low-frequency impedance characteristics of the direct current transmission system may cause system resonance, which in turn causes stability problems. Therefore, the stability of the system can be effectively improved by adjusting the impedance characteristics of the system. The low-frequency impedance reshaping technology adjusts the impedance characteristics of the system by changing the control parameters of the inverter or introducing active damping and other measures. The core of this method is to improve the phase margin and gain margin of the system by reshaping the impedance characteristics of the low-frequency band, thereby improving the dynamic response capability and stability of the system. The high-voltage direct current transmission grid-connected system stability control method based on low-frequency impedance reshaping improves the stability and robustness of the system by adjusting the system impedance characteristics, especially the characteristics of the low-frequency band. This method has important theoretical significance and practical application value in solving the low-frequency oscillation problem in the process of renewable energy grid connection. Summary of the invention

[0004] In view of the existing stable control of high-voltage direct current transmission grid-connected systems and the problems existing in the systems, the present invention is proposed.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a method for stabilizing a high voltage direct current transmission grid-connected system, which comprises the following steps:

[0007] Collect the numerical information of the high-voltage direct current transmission system, and obtain the output d-axis current reference value i of the receiving end by calculating the numerical information drefand the receiving end output q-axis current reference value i qref ;

[0008] Through the d-axis current reference value i dref Calculate the d-axis current control value, and then obtain the d-axis modulation signal m d ;

[0009] Through the q-axis current reference value i qref Calculate the q-axis current control value, and then obtain the q-axis modulation signal m q ;

[0010] According to the d-axis modulation signal m d and the q-axis modulation signal m q Carry out grid-connected current control and drive the receiving-end converter of the high-voltage DC transmission grid-connected system.

[0011] As a preferred solution of the high voltage direct current transmission grid-connected system stability control method of the present invention, wherein: obtaining the receiving end output d-axis current reference value i dref When the DC voltage at the receiving end is given, first obtain the given value u dcref And the actual voltage value u on the DC side dc , calculate the error value between the two, the calculation method includes:

[0012] e=u dcref -u dc ;

[0013] In the formula, e represents the error value;

[0014] By comparing the error value e with the HVDC transmission system outer loop controller G 1(s) Multiply them to obtain the output d-axis current reference value i of the receiving end dref , which can be expressed by the calculation formula:

[0015] i dref =G 1(s) ·e.

[0016] As a preferred solution of the high voltage direct current transmission grid-connected system stability control method of the present invention, wherein: obtaining the receiving end output q-axis current reference value i qref , determined by the control strategy.

[0017] As a preferred solution of the high-voltage direct current transmission grid-connected system stability control method of the present invention, wherein: the d-axis modulation signal m d The calculation steps include:

[0018] First, calculate the output d-axis current reference value i of the receiving end dref The actual value of the d-axis current output at the receiving end is i d The difference is expressed as follows:

[0019] e d =i dref -i d ;

[0020] In the formula, e d Expressed as difference;

[0021] Then the difference is compared with the inner loop controller G of the HVDC transmission system 2(s) Multiply them to obtain the control value of the d-axis current. The calculation formula is:

[0022] u dconteol =G 2(s) ·e d ;

[0023] In the formula, u dconteol It is expressed as the control value of d-axis current;

[0024] Finally, the actual value of the d-axis current i is outputted by the receiving end. d Multiply the product of the reference angular frequency ω and the inductance L of the filter circuit, and then add the resulting value to the grid-connected voltage d-axis component u d The control value u of the d-axis current is subtracted from the sum dconteol , subtract the virtual voltage d-axis component u from the obtained value dvir , and then divided by the DC voltage given value u on the receiving side dcref , get the d-axis modulation signal m d , expressed by the formula:

[0025]

[0026] In the formula, u dtotal Represented as the summed value in calculations.

[0027] As a preferred solution of the high-voltage direct current transmission grid-connected system stability control method of the present invention, wherein: the q-axis modulation signal m q The calculation steps include:

[0028] First, the receiving end output q-axis current reference value i qref The actual value of the q-axis current output at the receiving end is i q The value obtained by subtracting the value is the same as the inner loop controller G of the HVDC transmission system. 2(s) Multiply them together to get the control value of the q-axis current, which is expressed by the calculation formula:

[0029]

[0030] In the formula, u qconteol Expressed as the control value of the q-axis current;

[0031] Then the q-axis component u of the grid-connected point voltage qSubtract the actual value of the d-axis current output at the receiving end i d The product of the reference angular frequency ω and the inductance L of the filter circuit is subtracted from the control value of the q-axis current, and the virtual voltage q-axis component u is subtracted from the obtained value qvir , and then divided by the DC voltage given value u on the receiving side dcref , and get the q-axis modulation signal m q , expressed by the formula:

[0032]

[0033] As a preferred solution of the high voltage direct current transmission grid-connected system stability control method of the present invention, wherein: the virtual voltage d-axis component u dvir The calculation formula is expressed as:

[0034] u dvir =SL vir ·i d ;

[0035] Where, L vir Expressed as virtual inductance value.

[0036] As a preferred solution of the high voltage direct current transmission grid-connected system stability control method of the present invention, wherein: the virtual voltage q-axis component u qv ir The calculation formula is expressed as:

[0037] u qvir =SL vir ·i q .

[0038] In a second aspect, an embodiment of the present invention provides a high-voltage direct current transmission grid-connected system stability control system, which includes a data acquisition module, a data calculation module, and a modulation signal generation module;

[0039] The data acquisition module is used to collect numerical information of the high-voltage direct current transmission system as a basis for subsequent calculation and control;

[0040] The data calculation module is used to calculate reference values, control values, and component values;

[0041] The modulation signal generating module is used to generate a modulation signal.

[0042] In a third aspect, an embodiment of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the processor executes the computer program, it implements any step of the above-mentioned high-voltage direct current transmission grid-connected system stability control method.

[0043] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, any step of the above-mentioned high-voltage direct current transmission grid-connected system stability control method is implemented.

[0044] The beneficial effects of the present invention are as follows: in order to improve the output impedance characteristics of the receiving end of the high-voltage direct current transmission system and suppress the DC side oscillation that may be caused when connected to the weak power grid, a virtual impedance link is introduced into the receiving end converter control strategy. By introducing virtual impedance, the output impedance of the receiving end converter of the high-voltage direct current transmission system can be improved at the control level, so that the loop gain of the coupling system composed of the reactive compensation device, the receiving end converter and the weak power grid meets the generalized Nyquist stability criterion, thereby enhancing the system stability and improving the system stability margin. The present invention effectively improves the output impedance characteristics of the receiving end of the high-voltage direct current transmission system, improves the stability of the coupling system, and contributes to the further development of high-penetration new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0046] Figure 1 A structural diagram of a receiving end of a high voltage direct current transmission system for a stable control method of a high voltage direct current transmission grid-connected system.

[0047] Figure 2 This is the control structure diagram of the stability control method for the high voltage direct current transmission grid-connected system.

[0048] Figure 3 Nyquist curves before and after impedance reshaping for the HVDC grid-connected system stability control method.

[0049] Figure 4 This is the simulation waveform of the three-phase voltage at the common coupling point before impedance reshaping of the high-voltage direct current transmission grid-connected system stability control method.

[0050] Figure 5 This is the simulation waveform of the three-phase voltage at the common coupling point after impedance reshaping of the high-voltage direct current transmission grid-connected system stability control method. DETAILED DESCRIPTION

[0051] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0052] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0053] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0054] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0055] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0056] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or 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 present invention can be understood according to specific circumstances.

[0057] Example 1

[0058] First, Figure 1As shown, it should be understood that: the AC power grid, the resistance and inductance on the grid side, the receiving-end converter of the HVDC transmission system, the filter inductance on the AC side of the converter and the supporting capacitor on the DC side of the converter, the sending-end and DC-side capacitor of the HVDC transmission system can be regarded as ideal voltage sources, where C dc is the DC side support capacitor of the converter, u dc is the actual voltage on the DC side, L is the inductance of the filter circuit, u pcc is the voltage at the common coupling point, Lg is the equivalent inductance of the AC grid, R g is the equivalent resistance of the AC grid.

[0059] In this embodiment, the reference angular frequency is 314 rad / s, the equivalent inductance of the AC grid is 12 mH, the equivalent resistance of the AC grid is 1.1 Ω, the system switching frequency is 10000 Hz, the DC side support capacitance of the converter is 20 mF, the actual DC side voltage is 700 V, and the inductance of the filter circuit is 2 mH.

[0060] Reference Figure 1 and Figure 2 , which is the first embodiment of the present invention, and provides a method for stabilizing and controlling a high-voltage direct current transmission grid-connected system, comprising the following steps:

[0061] S1. Collect the numerical information of the high-voltage direct current transmission system and obtain the output d-axis current reference value i of the receiving end by calculating the numerical information. dref and the receiving end output q-axis current reference value i qref .

[0062] Get the output d-axis current reference value i of the receiving end dref When the DC voltage at the receiving end is given, first obtain the given value u dcref And the actual voltage value u on the DC side dc , calculate the error value between the two, the calculation method includes:

[0063] e=u dcref -u dc ;

[0064] In the formula, e represents the error value;

[0065] By comparing the error value e with the HVDC transmission system outer loop controller G 1(s) Multiply them to obtain the output d-axis current reference value i of the receiving end dref , expressed by the calculation formula:

[0066] i dref =G 1(s) ·e.

[0067] HVDC transmission system outer loop controller G 1(s) The expression is:

[0068] G 1(s) =k p1 +k i1 / s;

[0069] Among them, k p1 is the proportional coefficient of the PI controller, k i1 is the integral coefficient of the PI controller, s is the complex frequency, in this embodiment, u dcref =700V, k p1 =61, k i1 =1.3.

[0070] Get the output q-axis current reference value i of the receiving end qref , determined by the control strategy.

[0071] S2, through the d-axis current reference value i dref Calculate the d-axis current control value, and then obtain the d-axis modulation signal m d .

[0072] The d-axis modulation signal m d The calculation steps include:

[0073] First, calculate the output d-axis current reference value i of the receiving end dref The actual value of the d-axis current output at the receiving end is i d The difference is expressed as follows:

[0074] e d =i dref -i d ;

[0075] In the formula, e d Expressed as difference;

[0076] Then the difference is compared with the inner loop controller G of the HVDC transmission system 2(s) Multiply them to obtain the control value of the d-axis current. The calculation formula is:

[0077] u dconteol =G 2(s) ·e d ;

[0078] In the formula, u dconteol It is expressed as the control value of d-axis current;

[0079] Finally, the actual value of the d-axis current i is outputted by the receiving end. d Multiply the product of the reference angular frequency ω and the inductance L of the filter circuit, and then add the resulting value to the grid-connected voltage d-axis component u d The control value u of the d-axis current is subtracted from the sum dconteol , subtract the virtual voltage d-axis component u from the obtained value dvir, and then divided by the DC voltage given value u on the receiving side dcref , get the d-axis modulation signal m d , expressed by the formula:

[0080]

[0081] In the formula, u dtotal Represented as the summed value in calculations.

[0082] S3, through the q-axis current reference value i qref Calculate the q-axis current control value, and then obtain the q-axis modulation signal m q .

[0083] First, the receiving end output q-axis current reference value i qref The actual value of the q-axis current output at the receiving end is i q The value obtained by subtracting the value is the same as the inner loop controller G of the HVDC transmission system. 2(s) Multiply them together to get the control value of the q-axis current, which is expressed by the calculation formula:

[0084]

[0085] In the formula, u qconteol Expressed as the control value of the q-axis current;

[0086] Then the q-axis component u of the grid-connected point voltage q Subtract the actual value of the d-axis current output at the receiving end i d The product of the reference angular frequency ω and the inductance L of the filter circuit is subtracted from the control value of the q-axis current, and the virtual voltage q-axis component u is subtracted from the obtained value qvir , and then divided by the DC voltage given value u on the receiving side dcref , and get the q-axis modulation signal m q , expressed by the formula:

[0087]

[0088] Among them, the inner loop controller G of the HVDC transmission system 2(s) The expression is:

[0089] G2(s)=k p2 +k i2 / s;

[0090] k p2 is the proportional coefficient of the PI controller, k i2 is the integral coefficient of the PI controller, s is the complex frequency, in this embodiment, i qref =0, k p2 =14, k i2 =6000.

[0091] The virtual voltage d-axis component u dvir The calculation formula is expressed as:

[0092] u dvir =SL vir ·i d ;

[0093] Where, L vir Expressed as virtual inductance value.

[0094] The virtual voltage q-axis component u qv i The calculation formula of r is expressed as,

[0095] u qvir =SL vir ·i q .

[0096] S4, according to the d-axis modulation signal m d and the q-axis modulation signal m q Carry out grid-connected current control and drive the receiving-end converter of the high-voltage DC transmission grid-connected system.

[0097] In summary, in order to improve the output impedance characteristics of the receiving end of the high-voltage direct current transmission system and suppress the DC side oscillation that may be caused when connected to the weak power grid, a virtual impedance link is introduced into the receiving end converter control strategy. By introducing virtual impedance, the output impedance of the receiving end converter of the high-voltage direct current transmission system can be improved at the control level, so that the loop gain of the coupling system composed of the reactive compensation device, the receiving end converter and the weak power grid meets the generalized Nyquist stability criterion, thereby enhancing the system stability and improving the system stability margin. The present invention effectively improves the output impedance characteristics of the receiving end of the high-voltage direct current transmission system, improves the stability of the coupling system, and contributes to the further development of high-penetration new energy.

[0098] Example 2

[0099] On the basis of the first embodiment, this embodiment further provides a high-voltage direct current transmission grid-connected system stability control system, comprising a data acquisition module, a data calculation module, and a modulation signal generation module;

[0100] The data acquisition module is used to collect numerical information of the high-voltage direct current transmission system as a basis for subsequent calculation and control;

[0101] The data calculation module is used to calculate reference values, control values, and component values;

[0102] The modulation signal generating module is used to generate a modulation signal.

[0103] This embodiment also provides a computer device, which is applicable to the case of a high-voltage direct current transmission grid-connected system stability control method, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the high-voltage direct current transmission grid-connected system stability control method proposed in the above embodiment.

[0104] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0105] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for realizing the stability control of a high-voltage direct current transmission grid-connected system as proposed in the above embodiment is implemented.

[0106] The storage medium proposed in this embodiment and the data storage method proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be found in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0107] Example 3

[0108] Reference Figure 3 to Figure 5 Based on the previous two embodiments, this embodiment provides a high-voltage direct current transmission grid-connected system stability control method. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0109] Figure 3The Nyquist curves before and after impedance reshaping provided in an embodiment of the present invention, when the proposed control strategy is not adopted, the Nyquist curve of the coupled system consisting of the static VAR generator, the receiving end of the high voltage direct current transmission system and the weak power grid surrounds the point (-1, j0), and the system is in an unstable state at this time; when the proposed control strategy is adopted, the curve no longer surrounds the point (-1, j0), and the system is stable at this time. It can be seen that the proposed control strategy can effectively improve the negative damping characteristics of the receiving end converter of the high voltage direct current transmission system and improve the system stability.

[0110] Figure 4 The three-phase voltage simulation waveform at the common coupling point before impedance reshaping provided by an embodiment of the present invention shows that the instability of the interaction of the coupling system is repeated. The voltage amplitude changes dramatically and the oscillation frequency is low, indicating that the coupling system is unstable at this time and the voltage at the common coupling point has low-frequency oscillation.

[0111] Figure 5 The three-phase voltage simulation waveform of the common coupling point after impedance reshaping provided by an embodiment of the present invention is relatively stable in voltage amplitude, indicating that the method suppresses the oscillation of the common coupling point voltage and verifies the effectiveness of the proposed control strategy.

[0112] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A method for stabilizing and controlling a high voltage direct current transmission grid-connected system, characterized in that: The following steps are included: Collect the numerical information of the high-voltage direct current transmission system, and obtain the output d-axis current reference value i of the receiving end by calculating the numerical information dref and the receiving end output q-axis current reference value i qref ; Through the d-axis current reference value i dref Calculate the d-axis current control value, and then obtain the d-axis modulation signal m d ; Through the q-axis current reference value i qref Calculate the q-axis current control value, and then obtain the q-axis modulation signal m q ; According to the d-axis modulation signal m d and the q-axis modulation signal m q Carry out grid-connected current control and drive the receiving-end converter of the high-voltage DC transmission grid-connected system.

2. The method for controlling the stability of a high-voltage direct current transmission grid-connected system according to claim 1, characterized in that: Get the output d-axis current reference value i of the receiving end dref When the DC voltage at the receiving end is given, first obtain the given value u dcref And the actual voltage value u on the DC side dc , calculate the error value between the two, the calculation method includes: e=u dcref -in dc ; In the formula, e represents the error value; By comparing the error value e with the HVDC transmission system outer loop controller G 1(s) Multiply them to obtain the output d-axis current reference value i of the receiving end dref , expressed by the calculation formula: and dref =G 1(s) ·e.

3. The method for stabilizing and controlling a high voltage direct current transmission grid-connected system according to claim 1 or 2, characterized in that: Get the output q-axis current reference value i of the receiving end qref , determined by the control strategy.

4. The method for stabilizing and controlling a high voltage direct current transmission grid-connected system according to claim 3, characterized in that: The d-axis modulation signal m d The calculation steps include: First, calculate the receiving end output d-axis current reference value i dref The actual value of the d-axis current output at the receiving end is i d The difference is expressed as follows: yes d =i dref -i d ; In the formula, e d Expressed as difference; Then the difference is compared with the inner loop controller G of the HVDC transmission system 2(s) Multiply them to obtain the control value of the d-axis current. The calculation formula is: you dconteol =G 2(s) ·e d ; In the formula, u dconteol It is expressed as the control value of d-axis current; Finally, the actual value of the d-axis current i is outputted by the receiving end. d Multiply the product of the reference angular frequency ω and the inductance L of the filter circuit, and then add the resulting value to the grid-connected voltage d-axis component u d The control value u of the d-axis current is subtracted from the sum dconteol , subtract the virtual voltage d-axis component u from the obtained value dvir , and then divided by the DC voltage given value u on the receiving side dcref , get the d-axis modulation signal m d , expressed by the formula: In the formula, u dtotal Represented as the summed value in calculations.

5. The method for controlling the stability of a high-voltage direct current transmission grid-connected system according to claim 4, characterized in that: The q-axis modulation signal m q The calculation steps include: First, the receiving end output q-axis current reference value i qref The actual value of the q-axis current i q The value obtained by subtracting the value is the same as the inner loop controller G of the HVDC transmission system. 2(s) Multiply them together to get the control value of the q-axis current, which is expressed by the calculation formula: In the formula, u qconteol Expressed as the control value of the q-axis current; Then the q-axis component u of the grid-connected point voltage q Subtract the actual value of the d-axis current output at the receiving end i d The product of the reference angular frequency ω and the inductance L of the filter circuit is subtracted from the control value of the q-axis current, and the virtual voltage q-axis component u is subtracted from the obtained value qvir , and then divided by the DC voltage given value u on the receiving side dcref , and get the q-axis modulation signal m q , expressed by the formula:

6. The method for controlling the stability of a high voltage direct current transmission grid-connected system according to claim 5, characterized in that: The virtual voltage d-axis component u dvir The calculation formula is expressed as: in dvir =SL vir ·and d ; Where, L vir Expressed as virtual inductance value.

7. The method for controlling the stability of a high voltage direct current transmission grid-connected system according to claim 6, characterized in that: The virtual voltage q-axis component u qvir The calculation formula is expressed as: in qvir =SL vir ·and q 。 8. A high-voltage direct current transmission grid-connected system stability control system, based on the high-voltage direct current transmission grid-connected system stability control method according to any one of claims 1 to 7, characterized in that: It includes a data acquisition module, a data calculation module, and a modulation signal generation module; The data acquisition module is used to collect numerical information of the high-voltage direct current transmission system as a basis for subsequent calculation and control; The data calculation module is used to calculate reference values, control values, and component values; The modulation signal generating module is used to generate a modulation signal.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the high-voltage direct current transmission grid-connected system stability control method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the high-voltage direct current transmission grid-connected system stability control method according to any one of claims 1 to 7 are implemented.

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