A method and device for equivalent inertia support based on a direct current transmission system

Abstract

The application discloses a kind of equivalent inertia support control method and device based on direct current transmission system, it is related to power system operation and control technical field, the problem that control strategy can cause system oscillation in prior art is solved, its technical solution key points are: the power model and rotation equation of alternating current and direct current transmission system are established, the expression of the equivalent inertia support capacity of direct current transmission system is obtained in combination with the first preset formula;The expression of the equivalent inertia support capacity is combined with the second preset formula, the expression of the equivalent inertia support capacity based on constant droop coefficient is obtained, for providing time-varying equivalent inertia support for alternating current system by constant droop coefficient;By adjusting the equivalent inertia support provided to alternating current transmission system by droop coefficient, it can avoid introducing similar synchronous machine control dynamics, and further avoid causing system oscillation.

Description

Technical Field

[0001] This invention relates to the field of power system operation and control technology, and more specifically, to an equivalent inertia support control method and device based on a DC transmission system. Background Technology

[0002] With the widespread application of new energy power generation technologies and the implementation of numerous DC transmission projects, my country's power grid is gradually exhibiting "dual high" characteristics: a high proportion of new energy and a high proportion of power electronics. Consequently, the dynamic characteristics of the power system are more complex, and the safe and stable operation of the system faces new threats and challenges. One important challenge is how to address the insufficient system inertia caused by the inflow of new energy and power electronic devices. The DC transmission system (LCC-HVDC System) possesses rapid adjustability and short-term overload capability. In an AC / DC system environment, the DC transmission system can be considered a rapid and flexible adjustment resource under emergency fault conditions. Therefore, researching control methods that utilize the equivalent inertia support provided by the DC transmission system can alleviate the problem of insufficient system inertia and optimize the system's frequency dynamic response characteristics.

[0003] Existing inertia control methods for flexible resources mainly fall into two categories: inertia control strategies based on virtual synchronous machines (VSGs) and inertia control strategies based on proportional-derivative (PD) equations. Numerous scholars have extensively studied the application of these two control strategies in various flexible resources (e.g., energy storage systems, new energy power generation systems). Essentially, these two control strategies simulate the rotation equations of a synchronous machine to provide inertia support for the system. However, if the control parameters are not set properly, these two control strategies may induce system oscillations.

[0004] In summary, existing technologies have the problem that control strategies may cause system oscillations. Summary of the Invention

[0005] The purpose of this application is to provide an equivalent inertia support control method and device based on a DC transmission system, in order to solve the defects of existing control strategies that may cause system oscillations, and to achieve constant inertia support for the system while avoiding system oscillations.

[0006] This invention provides an equivalent inertia support control method based on a DC transmission system, comprising:

[0007] Establish the power model and rotation equation of the AC / DC transmission system, and combine it with the first preset formula to obtain the expression of the equivalent inertia support capacity of the DC transmission system;

[0008] By combining the expression for equivalent inertia support capacity with the second preset formula, an expression for equivalent inertia support capacity based on a constant droop coefficient is obtained, which is used to provide time-varying equivalent inertia support for AC systems through a constant droop coefficient.

[0009] By employing the above technical solution, the expression for the equivalent inertia support capability of the DC transmission system is determined through a first preset formula. An expression for the equivalent inertia support capability based on a constant droop coefficient is obtained according to a second preset formula, enabling the provision of time-varying equivalent inertia support to the AC transmission system through a constant droop coefficient. An expression for the time-varying droop coefficient based on constant equivalent inertia support is obtained according to a third preset formula, which is used to provide constant equivalent inertia support to the AC transmission system through a time-varying droop coefficient. By adjusting the droop coefficient to provide equivalent inertia support to the AC transmission system, the introduction of control dynamics similar to those of a synchronous machine can be avoided, thereby preventing system oscillations.

[0010] Furthermore, it also includes: combining the expression for the equivalent inertia support capability based on a constant droop coefficient with a third preset formula to obtain an expression for the time-varying droop coefficient based on constant equivalent inertia support, which is used to provide constant equivalent inertia support for the AC system through the time-varying droop coefficient.

[0011] Furthermore, combining the first preset formula, the expression for the equivalent inertia support capacity of the DC transmission system is obtained, including:

[0012]

[0013]

[0014] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP is the frequency change rate of the DC transmission system. f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the DC transmission system. J The increase in the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity of the DC transmission system; ΔP D This refers to the change in active power output of a DC transmission system.

[0015] Furthermore, by combining the expression for the equivalent inertia support capacity with the second preset formula, an expression for the equivalent inertia support capacity based on a constant sag coefficient is obtained, including:

[0016] ΔP D =-k D ω

[0017]

[0018] Where, ΔP D k represents the change in active power output of a DC transmission system. D ω is the droop coefficient of the DC transmission system; ω is the frequency deviation of the DC transmission system; ΔT J The increase in the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity; t is the operating time of the DC transmission system; T J is the total inertial time constant of the AC / DC transmission system; e is the base of the natural logarithm.

[0019] Furthermore, by combining the expression for the equivalent inertia support capacity based on a constant droop coefficient with the third preset formula, an expression for the time-varying droop coefficient based on constant equivalent inertia support is obtained, including:

[0020]

[0021]

[0022] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the AC / DC transmission system. J To increase the inertial time constant of AC / DC transmission systems, i.e., the equivalent inertia support capacity; k D This represents the droop coefficient of the DC transmission system.

[0023] Furthermore, it also includes setting the upper and lower limits of the time-varying droop coefficient based on the actual engineering project, and obtaining the optimized expression for the time-varying droop coefficient:

[0024]

[0025] Where, ΔP D ω represents the change in active power output of the DC transmission system; k represents the frequency deviation of the DC transmission system. D The droop coefficient of the DC transmission system; This represents the upper limit of the droop coefficient for a DC transmission system; k D，opt ΔT represents the lower limit of the droop coefficient of the DC transmission system; t represents the operating time of the DC transmission system; ΔT J This increases the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity.

[0026] The present invention also provides an equivalent inertia support control device based on a DC transmission system, comprising:

[0027] The first determining unit is used to establish the power model and rotation equation of the AC / DC transmission system, and combined with the first preset formula, to obtain the expression of the equivalent inertia support capacity of the DC transmission system.

[0028] The second determining unit is used to combine the expression of the equivalent inertia support capability with the second preset formula to obtain the expression of the equivalent inertia support capability based on the constant droop coefficient, and to provide time-varying equivalent inertia support for the AC system through the constant droop coefficient.

[0029] The third determining unit is used to combine the expression of the equivalent inertia support capability based on the constant droop coefficient with the third preset formula to obtain the expression of the time-varying droop coefficient based on the constant equivalent inertia support, and to provide constant equivalent inertia support for the AC system through the time-varying droop coefficient.

[0030] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the equivalent inertia support control method based on a DC transmission system as described above.

[0031] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the equivalent inertia support control method based on a DC transmission system as described above.

[0032] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the equivalent inertia support control method based on a DC transmission system as described above.

[0033] Compared with the prior art, this application has the following beneficial effects:

[0034] This invention provides an equivalent inertia support control method and apparatus based on a DC transmission system. The method determines the expression for the equivalent inertia support capability of the DC transmission system using a first preset formula, obtains an expression for the equivalent inertia support capability based on a constant droop coefficient using a second preset formula, thereby providing time-varying equivalent inertia support to the AC transmission system using a constant droop coefficient, and obtains an expression for the time-varying droop coefficient based on constant equivalent inertia support using a third preset formula, which is used to provide constant equivalent inertia support to the AC transmission system using a time-varying droop coefficient.

[0035] This invention provides equivalent inertia support for AC transmission systems by adjusting the droop coefficient, and provides constant equivalent inertia support for AC transmission systems by using a time-varying droop coefficient. Furthermore, this invention can avoid introducing control dynamics similar to those of a synchronous machine, thereby avoiding system oscillations. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0037] Figure 1 This is a flowchart illustrating an equivalent inertia support control method based on a DC transmission system provided by the present invention.

[0038] Figure 2 This is a schematic diagram of the characteristic curves of droop control, which is common in power systems in existing technologies.

[0039] Figure 3 This is a schematic diagram of the structure of an equivalent inertia support control device based on a DC transmission system provided by the present invention;

[0040] Figure 4 This is a schematic diagram of the structure of the electronic device provided by the present invention.

[0041] The attached diagram shows the markings and corresponding component names:

[0042] 310: First determining unit; 320: Second determining unit; 330: Third determining unit;

[0043] 410: Processor; 420: Communication interface; 430: Memory; 440: Communication bus. Detailed Implementation

[0044] In the following, the terms “comprising” or “may include” as used in the various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in the various embodiments of this application, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or the possibility of adding one or more combinations of the foregoing.

[0045] In various embodiments of this application, the expression "or" or "at least one of B and / or C" includes any combination or all combinations of the words listed simultaneously. For example, the expression "B or C" or "at least one of B and / or C" may include B, may include C, or may include both B and C.

[0046] The terms used in the various embodiments of this application (such as "first," "second," etc.) may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above terms do not limit the order and / or importance of the elements. The above terms are only used for the purpose of distinguishing one element from other elements. For example, a first user device and a second user device refer to different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of this application, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0047] The terminology used in the various embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0049] In existing power systems, methods for providing inertia support include: proportional-derivative inertia control strategies, with specific steps including:

[0050] First, based on the actual controlled object and control objective, a proportional-derivative inertia control strategy is designed, and the control parameters are tuned. This control strategy exhibits dynamics similar to the rotation equations of a synchronous machine.

[0051] Then, in practical applications, by measuring the system frequency, taking the proportional and differential terms of the system frequency, the active power output of the flexible adjustment resources is changed to provide inertia support for the system.

[0052] The existing methods have two main shortcomings:

[0053] (1) The essence of the existing control strategy is to simulate the rotation equation of a synchronous machine to provide inertia support for the system. However, due to the introduction of control dynamics similar to those of a synchronous machine, the existing control strategy may cause system oscillations if the control parameters are not set properly.

[0054] (2) The existing control strategies for flexible resource adjustment have not been analyzed for their applicability to DC transmission systems. Since the control characteristics of DC transmission systems are complex and variable, the mechanism of how to provide equivalent inertia support to the AC side by controlling the DC transmission system in emergency situations is still unclear and needs further analysis.

[0055] To address the above shortcomings, this invention proposes an equivalent inertia support control method and device based on a DC transmission system.

[0056] The following is combined Figures 1-2 This invention describes an equivalent inertia support control method based on a DC transmission system. Figure 1 This is a flowchart illustrating an equivalent inertia support control method for a DC transmission system provided by the present invention, as shown below. Figure 1 As shown, this embodiment of the invention provides an equivalent inertia support control method based on a DC transmission system, comprising:

[0057] S100: Establish the power model and rotation equation of the AC / DC transmission system, and combine it with the first preset formula to obtain the expression of the equivalent inertia support capacity of the DC transmission system;

[0058] S200: By combining the expression for equivalent inertia support capability with the second preset formula, an expression for equivalent inertia support capability based on a constant droop coefficient is obtained, which is used to provide time-varying equivalent inertia support for AC systems through a constant droop coefficient.

[0059] Specifically, based on the power model and rotation equation of the AC / DC transmission system, and in conjunction with the first preset formula, the equivalent inertia support capability of the DC transmission system is determined; based on the equivalent inertia support capability, and in conjunction with the second preset formula, the droop control coefficient of the DC transmission system is determined; and the equivalent inertia support control of the AC transmission system is performed through the droop control coefficient.

[0060] The following is a detailed explanation of step S100:

[0061] Step S110: Establish the power model and rotation equations of the AC / DC transmission system, including:

[0062] The rotation equation of a power system containing multiple synchronous generators can be expressed as follows:

[0063]

[0064] in, dP is the total inertial time constant of a DC transmission system (characterizing the total inertia of the system). f =P m -P eThis represents the magnitude of the unbalanced power caused by the fault, ω is the frequency deviation of the DC transmission system; G is the set of synchronous generators, and P... m =∑ i∈G P mi It is the total mechanical power of the DC transmission system, P e =∑ i∈G P ei It is the total electromagnetic power of the DC transmission system, T Ji S i P mi P ei The inertial time constant, rated capacity, mechanical power, and electromagnetic power of synchronous generator i are respectively, S. sys This refers to the rated capacity of the DC transmission system.

[0065] We can obtain:

[0066]

[0067] The above equation shows that the rate of change of frequency (RoCoF) of a DC transmission system is not only related to the total inertial time constant T of the DC transmission system. J It is also related to the total unbalanced power dP of the DC transmission system. f related.

[0068] S120: Considering the combination of the first preset formula, the expression for the equivalent inertia support capacity of the DC transmission system is obtained, including:

[0069] The equivalent inertia support capability of a DC system is evaluated by assuming the same rate of change of system frequency in the following two scenarios: 1) The actual inertial time constant of the system increases by ΔT. J ;2) Change in active power output ΔP of DC transmission system D This yields the first preset formula:

[0070]

[0071] It can be deduced that:

[0072]

[0073] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP is the frequency change rate of the DC transmission system. f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the DC transmission system. J Increase the inertial time constant of the DC transmission system by ΔP D This refers to the change in active power output of a DC transmission system.

[0074] In other words, in the event of an emergency failure, the DC transmission system can provide equivalent inertia support to the AC transmission system by changing the way its active power output is generated.

[0075] Furthermore, considering the droop control of the DC transmission system, through step S200, the expression for the equivalent inertia support capacity is combined with the second preset formula to obtain the expression for the equivalent inertia support capacity based on a constant droop coefficient:

[0076] The second preset formula is:

[0077] ΔP D =-k D ω

[0078] Where, k D k is the time-varying droop coefficient of a DC transmission system. A DC transmission system has multiple time parameters. D This represents the total droop coefficient for multiple DC transmission systems. Substituting the above formula into... We can obtain:

[0079]

[0080] According to the Laplace transform, we can obtain:

[0081]

[0082] We can obtain:

[0083]

[0084] By performing the inverse Laplace transform, we can obtain:

[0085]

[0086] Substituting the above equation into... We can obtain:

[0087]

[0088] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP is the frequency change rate of the DC transmission system. f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the DC transmission system. J Increase the inertial time constant of the DC transmission system by ΔP D k represents the change in active power output of a DC transmission system. D is the time-varying droop coefficient of the DC transmission system; e is the base of the natural logarithm; s is the complex frequency.

[0089] The above expression for the equivalent inertia support capability based on a constant droop coefficient is used to provide time-varying equivalent inertia support for AC systems using a constant droop coefficient.

[0090] The method proposed in this invention is based on active power-frequency droop control (P-fDroop Control) for DC transmission systems. Droop control, also known as droop rate control, utilizes the correlation between two variables to implement distributed control logic. It has a simple structure and does not contain control dynamics. Common droop control in power systems utilizes the primary droop characteristic similar to that of traditional generators, obtaining stable frequency and voltage through the active power / frequency (Pf) droop curve and the reactive power / voltage (QV) droop curve, respectively, thereby achieving parameter control of the target system. The characteristic curves of droop control are shown below. Figure 2 As shown. Steps S100-S200 study and design a method for the DC transmission system to provide power support to the AC side system through droop control when an emergency fault occurs in the power system. Based on the droop control of the DC transmission system in steps S100-S200, this invention further designs a time-varying droop coefficient in step S300 so that the DC system can provide constant equivalent inertia support capability.

[0091] Step S300: Combine the expression for the equivalent inertia support capability based on the constant droop coefficient with the third preset formula to obtain the expression for the time-varying droop coefficient based on constant equivalent inertia support, which is used to provide constant equivalent inertia support for the AC system through the time-varying droop coefficient.

[0092] To enable the DC transmission system to provide a constant equivalent inertia support, assume ΔT J The droop coefficient k is a constant. D For variables. Under this setting, by The third preset formula can be obtained, which includes:

[0093]

[0094] Substituting the above equation into... We can obtain:

[0095] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the DC transmission system. J Increase the inertial time constant of the DC transmission system; k D This represents the time-varying droop coefficient of the DC transmission system.

[0096] This is the expression for the time-varying droop coefficient based on constant equivalent inertia support. It shows that if the droop coefficient of the DC transmission system changes according to this law after a fault occurs, the DC transmission system will provide constant equivalent inertia support ΔT to the AC side. J Furthermore, a desirable property of this control strategy is k. D The expression for (t) and the unbalanced power dP of the system f Since it is unrelated to power imbalance, this control strategy can be deployed in advance and can cope with various power imbalances during actual system operation.

[0097] The equivalent inertia support control method based on DC transmission system provided by this invention does not introduce control dynamics similar to a synchronous machine, under the premise of providing constant equivalent inertia support for the AC side, thus avoiding problems such as system oscillation.

[0098] Furthermore, considering some limitations in practical engineering applications, the expression for the time-varying sag coefficient based on constant equivalent inertia support is improved through step s500, mainly in two aspects:

[0099] 1) According to the expression for the time-varying droop coefficient, as t approaches 0, k D (t) approaches infinity. Considering the physical constraints in practical engineering, the droop coefficient k D (t) should have an upper limit value.

[0100] 2) As t approaches infinity, k D (t) approaches 0. Considering that the designed equivalent inertia control strategy can balance steady-state and transient performance, the droop coefficient k D (t) should have a lower limit value, which can generally be taken as the optimal value k of the droop coefficient. D，opt .

[0101] In summary, considering practical engineering applications, the optimized expression for the time-varying droop coefficient is obtained as follows:

[0102]

[0103] Where, ΔP D ω represents the change in active power output of the DC transmission system; k represents the frequency deviation of the DC transmission system. D The droop coefficient of the DC transmission system; This represents the upper limit of the droop coefficient for a DC transmission system; k D，opt ΔT represents the lower limit of the droop coefficient of the DC transmission system; t represents the operating time of the DC transmission system; ΔT J To increase the inertial time constant of AC / DC transmission systems,

[0104] That is, the equivalent inertia support capacity.

[0105] The equivalent inertia support control method based on DC transmission systems provided by this invention can be applied to DC transmission systems, and has been improved accordingly for engineering applications, so as to better adapt to actual engineering scenarios.

[0106] In the above specific embodiments, the present invention provides an equivalent inertia support control method based on a DC transmission system. By creating a power model and rotation equations for the DC transmission system, and combining them with a first preset formula, an expression for the equivalent inertia support capability of the DC transmission system is obtained. Based on this expression and a second preset formula, an expression for the equivalent inertia support capability based on a constant droop coefficient is obtained. This constant droop coefficient provides time-varying equivalent inertia support to the AC system. Furthermore, by combining this constant droop coefficient with a third preset formula, an expression for the time-varying droop coefficient based on constant equivalent inertia support is obtained. This time-varying droop coefficient provides constant equivalent inertia support to the AC system. The equivalent inertia support control method for DC transmission systems provided by the present invention adjusts the equivalent inertia support by changing the droop coefficient, thus providing constant inertia support while avoiding the introduction of control dynamics similar to a synchronous machine, thereby preventing system oscillations.

[0107] In another aspect of this embodiment, an equivalent inertia support control device based on a DC transmission system is provided. The equivalent inertia support control device based on a DC transmission system described below can be referred to in correspondence with the equivalent inertia support control device based on a DC transmission system described above.

[0108] Figure 3 This is a schematic diagram of the structure of an equivalent inertia support control device based on a DC transmission system provided in an embodiment of the present invention, as shown below. Figure 3 As shown, this embodiment of the invention provides an equivalent inertia support control device based on a DC transmission system, comprising: a first determining unit 310, a second determining unit 320, and a third determining unit;

[0109] The first determining unit is used to establish the power model and rotation equation of the AC / DC transmission system, and, in conjunction with the first preset formula, to obtain the expression for the equivalent inertia support capacity of the DC transmission system.

[0110] The second determining unit is used to combine the expression of the equivalent inertia support capability with the second preset formula to obtain the expression of the equivalent inertia support capability based on the constant droop coefficient, and to provide time-varying equivalent inertia support for the AC system through the constant droop coefficient.

[0111] The third determining unit is used to combine the expression of the equivalent inertia support capability based on the constant droop coefficient with the third preset formula to obtain the expression of the time-varying droop coefficient based on the constant equivalent inertia support, and to provide constant equivalent inertia support for the AC system through the time-varying droop coefficient.

[0112] Based on the above embodiments, in this device, the expression for the equivalent inertia support capacity of the DC transmission system is obtained through a first preset formula;

[0113] The first preset formula and the expression for the equivalent inertia support capability are as follows:

[0114]

[0115]

[0116] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP is the frequency change rate of the DC transmission system. f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the DC transmission system. J The increase in the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity of the DC transmission system; ΔP D This refers to the change in active power output of a DC transmission system.

[0117] Based on the above embodiments, in this device, the expression for the equivalent inertia support capacity of the DC transmission system is obtained through a second preset formula;

[0118] The second preset formula and the expression for the equivalent inertia support capacity of the DC transmission system are as follows:

[0119] ΔP D =-k D ω

[0120]

[0121] Where, ΔP D k represents the change in active power output of a DC transmission system. D ω is the droop coefficient of the DC transmission system; ω is the frequency deviation of the DC transmission system; ΔT J The increase in the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity; t is the operating time of the DC transmission system; T J is the total inertial time constant of the AC / DC transmission system; e is the base of the natural logarithm.

[0122] Based on the above embodiments, in this device, the expression for the time-varying sag coefficient based on constant equivalent inertia support is obtained through a third preset formula:

[0123] The third preset formula and the expression for the time-varying sag coefficient based on constant equivalent inertia support include:

[0124]

[0125]

[0126] Where ω is the frequency deviation of the DC transmission system; t is the operating time of the DC transmission system; dP f T represents the total unbalanced power of the DC transmission system. J ΔT is the total inertial time constant of the AC / DC transmission system. J To increase the inertial time constant of AC / DC transmission systems, i.e., the equivalent inertia support capacity; k D This represents the droop coefficient of the DC transmission system.

[0127] Based on the above embodiments, in this device, the upper and lower limits of the time-varying droop coefficient are set according to the actual engineering settings to obtain the optimized expression for the time-varying droop coefficient:

[0128]

[0129] Where, ΔP D ω represents the change in active power output of the DC transmission system; k represents the frequency deviation of the DC transmission system. D For the coefficients of the DC transmission system; This represents the upper limit of the droop coefficient for a DC transmission system; k D，opt ΔT represents the lower limit of the time-varying droop coefficient of the DC transmission system; t represents the operating time of the DC transmission system; ΔT J This increases the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity.

[0130] In the above specific embodiments, the present invention provides an equivalent inertia support control device based on a DC transmission system. By creating a power model and rotation equations for the DC transmission system, and combining them with a first preset formula, an expression for the equivalent inertia support capability of the DC transmission system is obtained. Based on this expression and a second preset formula, an expression for the equivalent inertia support capability based on a constant droop coefficient is obtained. This constant droop coefficient provides time-varying equivalent inertia support to the AC system. Furthermore, by combining a third preset formula, an expression for the time-varying droop coefficient based on constant equivalent inertia support is obtained. This time-varying droop coefficient provides constant equivalent inertia support to the AC system. The equivalent inertia support control method based on a DC transmission system provided by the present invention adjusts the equivalent inertia support by changing the droop coefficient, thus providing constant inertia support while avoiding the introduction of control dynamics similar to a synchronous machine, thereby preventing system oscillations.

[0131] Figure 4 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 4 As shown, the electronic device may include a processor 410, a communication interface 420, a memory 430, and a communication bus 440. The processor 410, communication interface 420, and memory 430 communicate with each other via the communication bus 440. The processor 410 can call logic instructions in the memory 430 to execute an equivalent inertia support control method based on a DC transmission system. This method includes: determining the equivalent inertia support capability of the DC transmission system based on a pre-created power model and rotation equations of the DC transmission system; determining the time-varying droop control coefficients of the DC transmission system based on the equivalent inertia support capability to determine an equivalent inertia control strategy based on time-varying droop in the DC transmission system. The equivalent inertia control strategy is used to perform equivalent inertia support control on the DC transmission system.

[0132] Furthermore, the logical instructions in the aforementioned memory 430 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0133] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the equivalent inertia support control method based on the above-described methods for DC transmission systems. The method includes: determining the equivalent inertia support capability of the DC transmission system based on a pre-created power model and rotation equations of the DC transmission system; determining the time-varying droop control coefficient of the DC transmission system according to the equivalent inertia support capability, so as to determine the equivalent inertia control strategy based on time-varying droop in the DC transmission system, wherein the equivalent inertia control strategy is used to perform equivalent inertia support control on the DC transmission system.

[0134] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the equivalent inertia support control method based on a DC transmission system provided by the above methods. The method includes: determining the equivalent inertia support capability of the DC transmission system based on a pre-created power model and rotation equations of the DC transmission system; determining the time-varying droop control coefficient of the DC transmission system according to the equivalent inertia support capability, thereby determining an equivalent inertia control strategy based on time-varying droop in the DC transmission system, wherein the equivalent inertia control strategy is used to perform equivalent inertia support control on the DC transmission system.

[0135] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0136] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An equivalent inertia-supported control method based on a DC transmission system, characterized by: including... A power model and rotation equations for the AC / DC transmission system are established. Combined with the first pre-defined formula, the expression for the equivalent inertia support capacity of the DC transmission system is obtained; it is expressed as: in, This refers to the frequency deviation of the DC transmission system. This refers to the operating time of the DC transmission system. The rate of frequency change of a DC transmission system; This represents the total unbalanced power of the DC transmission system. The total inertial time constant of the DC transmission system; This increases the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity of the DC transmission system. This refers to the change in active power output of the DC transmission system. Combining the expression for equivalent inertia support capacity with the second preset formula, we obtain the expression for equivalent inertia support capacity based on a constant sag coefficient; expressed as: in, This refers to the change in active power output of the DC transmission system. The droop coefficient of the DC transmission system; For the frequency deviation of the DC transmission system; for the increase in the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity. This refers to the operating time of the DC transmission system. The total inertial time constant of the AC / DC transmission system; is the base of the natural logarithm; By combining the expression for the equivalent inertia support capability based on a constant droop coefficient with the third preset formula, an expression for the time-varying droop coefficient based on constant equivalent inertia support is obtained. This expression is used to provide constant equivalent inertia support for the AC system through a time-varying droop coefficient; it is expressed as: Wherein, is the frequency deviation of the DC transmission system; This refers to the operating time of the DC transmission system. This represents the total unbalanced power of the DC transmission system. The total inertial time constant of the AC / DC transmission system; The increase in the inertial time constant of the AC / DC transmission system is the equivalent inertia support capacity; the droop coefficient of the DC transmission system is the droop coefficient.

2. The equivalent inertia support control method based on a DC transmission system according to claim 1, characterized in that: It also includes setting the upper and lower limits of the droop coefficient based on the actual engineering project, and obtaining the expression for the optimized time-varying droop coefficient. in, This refers to the change in active power output of the DC transmission system. This refers to the frequency deviation of the DC transmission system. For the coefficients of the DC transmission system; This represents the upper limit of the droop coefficient for a DC transmission system. This represents the lower limit of the time-varying droop coefficient for DC transmission systems. This refers to the operating time of the DC transmission system. This increases the inertial time constant of the AC / DC transmission system, i.e., the equivalent inertia support capacity.

3. A control device based on the equivalent inertia support of a DC transmission system, used to implement the equivalent inertia support control method based on a DC transmission system as described in claim 1 or 2, characterized in that: include: The first determining unit is used to establish the power model and rotation equation of the AC / DC transmission system, and combined with the first preset formula, to obtain the expression of the equivalent inertia support capacity of the DC transmission system. The second determining unit is used to combine the expression of the equivalent inertia support capability with the second preset formula to obtain the expression of the equivalent inertia support capability based on the constant droop coefficient, and to provide time-varying equivalent inertia support for the AC system through the constant droop coefficient. The third determining unit is used to combine the expression of the equivalent inertia support capability based on the constant droop coefficient with the third preset formula to obtain the expression of the time-varying droop coefficient based on the constant equivalent inertia support, and to provide constant equivalent inertia support for the AC system through the time-varying droop coefficient.

4. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the equivalent inertia support control method based on a DC transmission system as described in any one of claims 1 to 2.

5. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the equivalent inertia support control method based on a DC transmission system as described in any one of claims 1 to 2.

6. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the equivalent inertia support control method based on a DC transmission system as described in any one of claims 1 to 2.

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