A network-configuration type converter control method and system for improving small-signal stability

Abstract

The application belongs to the technical field of power electronic equipment and converter control, and specifically discloses a network-constructed converter control method and system for improving small disturbance stability. The application constructs an adaptive threshold judgment mechanism based on a deviation index: the maximum deviation index of the system in the stable parameter domain is determined according to various typical active control strategies, and the adaptive threshold is set by taking the intermediate value; in actual control, the maximum deviation index corresponding to the current control strategy is compared with the threshold, and the converter model considering or ignoring the reactive dynamic coupling is adaptively selected for controller parameter setting. Since the mechanism can dynamically evaluate the influence degree of the reactive dynamic coupling on the stability, the small disturbance stability analysis accuracy is ensured, the model complexity and the calculation efficiency are effectively balanced, the stability misjudgment caused by excessive simplification of the model is avoided, and the system stability margin misjudgment problem caused by ignoring the reactive dynamic coupling in the prior art is solved.

Description

Technical Field

[0001] This application belongs to the field of power electronic equipment and converter control technology, and more specifically, relates to a control method and system for grid-type converters that improves stability under small disturbances. Background Technology

[0002] With the rapid development of high-proportion new energy power systems represented by wind power and photovoltaics, grid-connected converters have become key technical equipment for improving the stability and reliability of power systems because they can autonomously establish and support grid voltage and frequency. The core of grid-connected control lies in simulating the physical characteristics of synchronous generators, and its control strategy typically includes an active-frequency loop and a reactive-voltage loop.

[0003] In existing technologies, to simplify system analysis and controller parameter design, researchers often employ a key model simplification technique when analyzing network-based control strategies (such as small-disturbance stability): ignoring the dynamic equations of reactive power. This involves assuming the reactive power loop responds extremely quickly or directly ignoring its dynamic process, retaining only the dynamic equations of the active power loop for analysis. While this simplification reduces model order and analytical complexity, in real physical systems, active and reactive power dynamics are closely related through grid impedance, load, and cross-coupling terms within the converter. Ignoring reactive power dynamics can lead to misjudgments of the system's actual stability margin; for example, it might misjudge an unstable system as stable, or significantly deviate from the assessment of stability boundaries and damping characteristics.

[0004] Currently, academia and industry lack a unified, quantitative tool to assess the analytical errors introduced by model simplification (ignoring reactive power dynamics), and even more so, to compare the coupling strength between active and reactive power under different network configurations and active power control strategies. This results in a lack of clear quantitative basis for control strategy selection, parameter tuning, and system-level stability assessment, affecting the accuracy, safety, and economy of system design. Therefore, there is an urgent need for a unified quantitative assessment method that can cross control strategies and system orders to accurately measure the stability analysis deviations caused by the simplification of ignoring reactive power dynamics under different control methods, and to reveal the inherent laws of active-reactive power coupling in different active power control strategies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a control method and system for grid-type converters that improves stability under small disturbances. This aims to solve the problem that when analyzing grid-type converter control strategies in existing technologies, the commonly used simplification method of directly ignoring reactive dynamics may lead to misjudgment of the actual stability margin of the system, potentially misjudging an unstable system as stable, or causing significant deviations in the evaluation of stability boundaries and damping characteristics.

[0006] To achieve the above objectives, in a first aspect, this application provides a control method for a grid-connected converter to improve stability under small disturbances. The power system and the grid-connected converter form a grid-connected system. The control method includes:

[0007] Obtain the network model parameters of the power system, the electrical parameters and control parameters of the converter, and the operating status parameters of the grid-connected system;

[0008] The state-space model of the grid-connected system corresponding to various typical active power control strategies is associated with all the obtained parameters. The maximum value of the deviation index of the grid-connected system in the stable parameter domain under each typical active power control strategy is determined. The median value of all the maximum deviation indices is used as the adaptive threshold of the deviation index. The deviation index is the relative error between the attenuation factor considering the dynamic coupling of reactive power and the attenuation factor ignoring the dynamic coupling of reactive power.

[0009] The state-space model of the grid-connected system corresponding to the current active power control strategy is associated with all the acquired parameters to determine the maximum value of the deviation exponent of the grid-connected system in the stability parameter domain under the current active power control strategy.

[0010] Based on the comparison between the maximum deviation index of the active power control strategy and the adaptive threshold, a grid-type converter modeling method is selected. The control parameters are tuned based on the selected model to achieve stable control of the grid-type converter: if the maximum deviation index exceeds the adaptive threshold, a grid-type converter model considering reactive power dynamic coupling is established; otherwise, a grid-type converter model ignoring reactive power dynamic coupling is adopted.

[0011] Preferably, if the grid-connected system is simplified to a second-order system with respect to angle, the state-space model of the grid-connected system corresponding to the active power control strategy is as follows:

[0012] ;

[0013] in, These are second-order, first-order, and zero-order coefficients, determined based on the obtained converter and power system parameters. Their values ​​differ depending on whether reactive power dynamics are considered or ignored. The output phase angle of the power control loop. These are the output phase angles of the power control loop. The small perturbation, the first derivative of the small perturbation, and the second derivative of the small perturbation.

[0014] Preferably, if the grid-connected system is simplified to a second-order system with respect to angle, the attenuation factor is calculated as follows:

[0015] ;

[0016] in, This is the attenuation factor.

[0017] Preferably, if the grid-connected system is simplified to a third-order system with respect to angle, the state-space model of the grid-connected system corresponding to the active power control strategy is as follows:

[0018] ;

[0019] in, These are third-order, second-order, first-order, and zero-order coefficients, determined based on the obtained converter and power system parameters. Their values ​​differ depending on whether reactive power dynamics are considered or ignored. The output phase angle of the power control loop. These are the output phase angles of the power control loop. Small perturbation, the first derivative of the small perturbation, the second derivative of the small perturbation, and the third derivative of the small perturbation.

[0020] Preferably, if the grid-connected system is simplified to a third-order system with respect to angle, the attenuation factor is calculated as follows:

[0021] ;

[0022] Among them, the equivalent first-order coefficients Equivalent second-order coefficients , This is the attenuation factor.

[0023] Preferably, within the stable parameter domain, feasible parameter combinations are iterated and calculated. For each feasible parameter combination, the deviation index is calculated, and then the maximum deviation index is determined.

[0024] ;

[0025] in, To account for the attenuation factor of reactive dynamic coupling, To ignore the attenuation factor of reactive dynamic coupling, the deviation index The larger the value, the more significant the impact of reactive power dynamics on stability assessment.

[0026] Preferably, the typical active power control strategies are pre-stored in the controller, including the following five types: droop control, proportional-derivative droop control, droop control with second-order derivative terms, virtual synchronous generator control, and virtual synchronous generator control with feedforward.

[0027] Preferably, the current active power control strategy is one of the typical active power control strategies or is different from the typical active power control strategy.

[0028] To achieve the above objectives, in a second aspect, this application provides a grid-type converter control system for improving stability under small disturbances, including a memory and one or more processors; the memory is coupled to the one or more processors, the memory is used to store computer program code, the computer program code including computer instructions; the one or more processors invoke the computer instructions to cause the system to execute the control method as described in the first aspect.

[0029] To achieve the above objectives, in a third aspect, this application provides a computer-readable storage medium including instructions that, when executed on an electronic device, cause the electronic device to perform the control method as described in the first aspect.

[0030] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0031] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:

[0032] This application proposes a control method for networked converters to improve stability under small disturbances. By constructing an adaptive threshold judgment mechanism based on the "deviation index," the method associates the coupled system state-space model corresponding to five typical active power control strategies with system parameters, determines the maximum value of the deviation index in the stability parameter domain under each strategy, and uses the median of these maximum values ​​as the adaptive threshold. In actual control, since the impact of reactive power dynamic coupling on system stability varies under different active power control strategies, the method compares the maximum deviation index corresponding to the current strategy with this threshold to dynamically determine whether to use a model considering reactive power dynamic coupling or ignoring it for controller parameter tuning. This effectively balances model complexity and computational efficiency while ensuring the accuracy of small disturbance stability analysis, avoiding potential stability misjudgments caused by oversimplification of the model. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating a grid-type converter control method for improving stability under small disturbances, provided in an embodiment of this application.

[0034] Figure 2 This refers to the different active power control strategies provided in the embodiments of this application. Calculated value. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0037] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0038] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0039] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0040] For ease of understanding, the relevant technical terms involved in the embodiments of this application will be explained and described below.

[0041] Small disturbances refer to a tiny, local disturbance applied to a system, and have the following characteristics: (1) small amplitude: the amplitude of a small disturbance is usually much smaller than the signal amplitude when the system is running normally; (2) locality: small disturbances usually act on a local part of the system, rather than a major global disturbance.

[0042] Small-disturbance stability refers to a system's ability to maintain stable operation under minor disturbances. For grid-type inverters, small-disturbance stability analysis primarily focuses on their operational stability in weak grid environments.

[0043] The embodiments of this application are described below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, this application provides a control method for grid-connected converters to improve stability under small disturbances. The power system and the grid-connected converter form a grid-connected system. The control method includes:

[0045] Obtain the network model parameters of the power system, the electrical parameters and control parameters of the converter, and the operating status parameters of the grid-connected system;

[0046] The state-space model of the grid-connected system corresponding to various typical active power control strategies is associated with all the obtained parameters. The maximum value of the deviation index of the grid-connected system in the stable parameter domain under each typical active power control strategy is determined. The median value of all the maximum deviation indices is used as the adaptive threshold of the deviation index. The deviation index is the relative error between the attenuation factor considering the dynamic coupling of reactive power and the attenuation factor ignoring the dynamic coupling of reactive power.

[0047] The state-space model of the grid-connected system corresponding to the current active power control strategy is associated with all the acquired parameters to determine the maximum value of the deviation exponent of the grid-connected system in the stability parameter domain under the current active power control strategy.

[0048] Based on the comparison between the maximum deviation index of the active power control strategy and the adaptive threshold, a grid-type converter modeling method is selected. The control parameters are tuned based on the selected model to achieve stable control of the grid-type converter: if the maximum deviation index exceeds the adaptive threshold, a grid-type converter model considering reactive power dynamic coupling is established; otherwise, a grid-type converter model ignoring reactive power dynamic coupling is adopted.

[0049] This application selects several typical network-type active power control strategies as the analysis objects. For each strategy, it establishes separate models considering reactive power control and neglecting reactive power control, and uses unified parameter notation to express the state equation coefficients of different strategies, forming a unified mathematical expression form, laying the foundation for subsequent unified analysis. The network model parameters of the power system include network topology, line impedance, etc.; the electrical parameters of the converter include the rated capacity of the converter, filter parameters, DC side voltage, etc.; the regulation parameters of the converter control system include the control parameters of the power control loop (active / reactive power), time constant, coupling coefficient, virtual inertia constant, etc.; the operating state parameters of the grid-connected system include the current active / reactive power output, grid connection point voltage, frequency, etc.

[0050] Preferably, if the grid-connected system is simplified to a second-order system with respect to angle, the state-space model of the grid-connected system corresponding to the active power control strategy is as follows:

[0051] ;

[0052] in, These are second-order, first-order, and zero-order coefficients, determined based on the obtained converter and power system parameters. Their values ​​differ depending on whether reactive power dynamics are considered or ignored. The output phase angle of the power control loop. These are the output phase angles of the power control loop. The small perturbation, the first derivative of the small perturbation, and the second derivative of the small perturbation.

[0053] Preferably, if the grid-connected system is simplified to a second-order system with respect to angle, the attenuation factor is calculated as follows:

[0054] ;

[0055] in, This is the damping factor, i.e., the damping ratio of the system.

[0056] Preferably, if the grid-connected system is simplified to a third-order system with respect to angle, the state-space model of the grid-connected system corresponding to the active power control strategy is as follows:

[0057] ;

[0058] in, These are third-order, second-order, first-order, and zero-order coefficients, determined based on the obtained converter and power system parameters. Their values ​​differ depending on whether reactive power dynamics are considered or ignored. The output phase angle of the power control loop. These are the output phase angles of the power control loop. Small perturbation, the first derivative of the small perturbation, the second derivative of the small perturbation, and the third derivative of the small perturbation.

[0059] It should be noted that, based on the physical equilibrium relationship revealed by the Routh stability criterion, the original third-order system is mapped to an equivalent second-order system with the same net damping characteristics. Furthermore, an equivalent damping factor is defined from this equivalent second-order system. This method has mathematical uniformity: when the coefficient of the third-order term is zero, the equivalent damping factor automatically degenerates into the damping ratio of the second-order system.

[0060] Preferably, if the grid-connected system is simplified to a third-order system with respect to angle, the attenuation factor is calculated as follows:

[0061] ;

[0062] Among them, the equivalent first-order coefficients Equivalent second-order coefficients , This is the attenuation factor.

[0063] Preferably, within the stable parameter domain, feasible parameter combinations are iterated and calculated. For each feasible parameter combination, the deviation index is calculated, and then the maximum deviation index is determined.

[0064] ;

[0065] in, To account for the attenuation factor of reactive dynamic coupling, To ignore the attenuation factor of reactive dynamic coupling, the deviation index The larger the value, the more significant the impact of reactive power dynamics on stability assessment.

[0066] Preferably, the typical active power control strategies are pre-stored in the controller, including the following five types: droop control, proportional-derivative droop control, droop control with second-order derivative terms, virtual synchronous generator control, and virtual synchronous generator control with feedforward.

[0067] Preferably, the current active power control strategy is one of the typical active power control strategies or is different from the typical active power control strategy.

[0068] Example

[0069] This embodiment selects five typical active power control strategies for grid-connected inverters as evaluation objects, namely droop control, scaling control, and flexural control. Control, proportional-derivative droop control Droop control containing second-order differential terms Virtual synchronous generator control and virtual synchronous generator control with feedforward These five control strategies are all for active power. and power control loop output phase angle The control transfer function between them is used to convert it into active power. With the power control loop output angular frequency After the transfer functions in the Laplace domain between them, they are as follows: , , , , ,in, The droop coefficient is... These are the coefficients of the first derivative term in proportional-derivative droop control. These are the coefficients of the first-order differential term in a control system containing second-order differentials. These are the coefficients of the second-order differential term. Forward coefficients, For differential operators, It is a virtual inertial constant. This is the reference angular frequency.

[0070] The above five typical active power control strategies can be expressed in a unified standard form as follows: , These are constant coefficients.

[0071] The following will use The standard form of the active power control parameters is used to derive the dynamic equation expressions for completely ignoring the reactive power loop and considering the first-order dynamics of the reactive power loop.

[0072] On the one hand, the dynamic equation for the phase angle when reactive power is completely ignored is as follows:

[0073] ;

[0074] in, ;

[0075] in, These are the constant coefficients used to determine the active power control transfer function for different categories. and The intermediate coefficients introduced in obtaining this dynamic equation are only used for simplifying expressions during formula derivation or calculation and do not constitute independent physical parameters. Rated power per unit, Indicates the rated power. Indicates the power reference value. This indicates the cutoff frequencies of the active and reactive power filters. , , These represent the voltage, phase angle, and frequency values ​​output by the power control loop, respectively. and These represent the grid voltage and frequency values, respectively. All frequency values ​​are in rad / s. These are the resistance and inductance of the transmission line, respectively.

[0076] On the other hand, a reactive power control model considering reactive power dynamics is also available:

[0077] ;

[0078] in, ;

[0079] in, Based on system rated parameters and intermediate coefficients The calculated equivalent coefficients, For the intermediate coefficient The equivalent gain parameter obtained by combining it with the system's rated parameters, and These are intermediate coefficients determined by electrical parameters, used only to express relevant terms in the system model or control law, and do not constitute adjustable control parameters. Indicates the per-unit rated power. The reactive power control droop coefficient is used. This is the cutoff frequency of the reactive power filter. , , These represent the voltage, phase angle, and frequency values ​​output by the power control loop, respectively. and These represent the grid voltage and frequency values, respectively. All frequency values ​​are in rad / s. These are the resistance and inductance of the transmission line, respectively.

[0080] For the five typical active power control strategies mentioned above, this application establishes high-fidelity state-space models (considering reactive power and voltage dynamics) and simplified state-space models (ignoring reactive power and voltage dynamics) of their grid-connected systems. Following the method described in this application, the closed-loop characteristic differential equations characterizing the dominant dynamics of the system are further derived, as shown in Tables 1 and 2, respectively.

[0081] Table 1. Equations for five active power control strategies that directly neglect reactive power dynamics.

[0082]

[0083] Table 2 Dynamic equations considering reactive power under five active power control strategies

[0084]

[0085] Based on the unified method defined in this application, the equivalent attenuation factor of each active power control strategy is calculated under both reactive power control model and reactive power control model.

[0086] The spatial state differential equations under different active power control strategies fall into two categories: second-order and third-order. To unify the evaluation index of second-order and third-order systems, a decay factor is defined. .

[0087] The second-order differential equation can be written in general form:

[0088] ;

[0089] The attenuation factor is defined as the damping ratio in the second-order differential equation, and the damping ratio is selected. As a description of the damping characteristics of a second-order differential equation, when the coefficients of the constant term in the general formula... The condition for system stability is that the decay factor is positive. Greater than 0. The specific form is as follows:

[0090] ;

[0091] Rewrite the third-order differential equation in general form:

[0092] ;

[0093] Unlike second-order differential equations, third-order systems do not have an explicit definition of a decay factor index. For third-order systems, higher-order dynamics... The presence of higher-order effects often introduces phase lag, thereby weakening the overall damping characteristics of the system. To quantify the impact of these higher-order effects on system stability and establish a unified quantization framework with second-order systems, this application constructs an equivalent reduced-order model based on the Routh criterion. Specifically, the stability boundary of a third-order system is satisfied by the coefficients of its characteristic equation. This algebraic relationship reveals the physical mechanism of system stability. We map the third-order system to an equivalent second-order system that preserves this net damping characteristic:

[0094] ;

[0095] Based on this, the equivalent attenuation factor is defined. :

[0096] ;

[0097] in, , Equivalent attenuation factor In mathematical form, it is consistent with the second-order index, when It degenerates into a second-order form when the condition is met. When this is the case, the stability principle described in the Routh criterion naturally holds true, thus constructing a unified evaluation dimension across orders.

[0098] For a second-order system, taking the first type of pure active power droop control method as an example, the reactive power neglect control model is as follows:

[0099] ;

[0100] The reactive power control model considering reactive power coupling is as follows:

[0101] ;

[0102] in, This represents the grid voltage amplitude, which is a parameter in the power system network model. This refers to the per-unit rated power, which is an electrical parameter of the converter. , These are the regulating parameters of the converter control system; , , These are parameters related to the operating status of the grid-connected system. It belongs to the derived quantity obtained by coupling and simplifying the basic parameters.

[0103] Ignore reactive power Denotes the attenuation factor, where

[0104] ;

[0105] Considering reactive power Denotes the attenuation factor, where

[0106] ;

[0107] For a third-order system, taking the fourth virtual synchronous generator control method as an example, the reactive power neglect control model is as follows:

[0108] ;

[0109] The reactive power control model considering reactive power coupling is as follows:

[0110] ;

[0111] in, , , These are runtime status parameters; , , These are the regulating parameters of the converter control system; Characteristic parameters belonging to the converter, This represents the grid voltage amplitude, which is a parameter in the power system's network model. It belongs to the derived quantity obtained by coupling and simplifying the basic parameters.

[0112] Ignore reactive power Denotes the equivalent attenuation factor, where:

[0113] ;

[0114] Considering reactive power Denotes the equivalent attenuation factor, where:

[0115] ;

[0116] To quantify the bias in stability analysis caused by the simplification of modeling by ignoring reactive power equations, a normalized error index is defined. as follows:

[0117] ;

[0118] in, To account for the attenuation factor of reactive dynamic coupling, To ignore the attenuation factor of reactive dynamic coupling. If A smaller value indicates that the reactive power-ignoring control model can reproduce the damping characteristics of the real system with high fidelity; conversely, if... A large value indicates that ignoring reactive power dynamics will lead to significant stability assessment errors. In this case, a reactive power control model should be used for analysis. Based on this, a normalized error index based on the equivalent attenuation factor is employed. This allows for a quantitative assessment of the impact of the simplification strategy of ignoring reactive power equations on system stability, as well as a quantitative analysis of the dynamic coupling strength between active and reactive power.

[0119] To ensure the fairness and relevance of the assessment to the project, a parameter range that meets the requirements for stable operation of the project is defined for each control strategy, including but not limited to: droop coefficient. Differential gain and Reasonable range of values ​​for parameters.

[0120] Within the stable parameter domain of each strategy, parameter traversal calculations are performed. For each control strategy, the corresponding indices are calculated under different feasible parameter combinations. Find the values ​​and identify the maximum value, denoted as . .Should This characterizes the maximum upper bound that the stability assessment error may reach under this strategy when ignoring reactive dynamics, which reflects the modeling bias under the worst operating conditions.

[0121] Through the above systematic calculations, the five active power control strategies were calculated separately, resulting in the five control strategies. Values ​​such as Figure 2 As shown. The first control strategy is drooping. Control, within the stable parameter range The maximum value of the indicator is 5.1185; the second control strategy is... Compared to , introduced Parameters make The maximum increase in the indicator was 10.3544; the third control strategy was to introduce... The parameters are reduced compared to the second method. The indicator was reduced to 10.3369; the fourth control strategy used... Controlled within a stable parameter range The maximum value of the indicator is 5.1185; the fifth control strategy introduces a coefficient based on VSG. Mid-to-late indicators It will drop to 5.7488. The smaller the indicator, the less the impact of ignoring reactive power on active power control, and the weaker the coupling between active and reactive power. The five control methods are ranked from largest to smallest impact as follows: This embodiment fully demonstrates the implementation process of the evaluation method proposed in this invention and its application value in comparing the active and reactive power coupling strength under different active power control strategies, verifying the effectiveness and practicality of the method.

[0122] Furthermore, the median value of all maximum deviation indices is used as the adaptive threshold for the deviation index. Based on the comparison between the maximum deviation index of the active power control strategy and the adaptive threshold, the modeling method of the grid-type converter is selected. The control parameters are tuned based on the selected model to achieve stable control of the grid-type converter: if the maximum deviation index exceeds the threshold, a grid-type converter model considering reactive power dynamic coupling is established; otherwise, a grid-type converter model ignoring reactive power dynamic coupling is adopted.

[0123] It should be understood that the above-described device is used to execute the methods in the above embodiments. The implementation principle and technical effect of the corresponding program modules in the device are similar to those described in the above methods. The working process of the device can be referred to the corresponding process in the above methods, and will not be repeated here.

[0124] Based on the methods in the above embodiments, this application provides an electronic device that may include a processor, a communications interface, a memory, and a communication bus, wherein the processor, communications interface, and memory communicate with each other via the communication bus. The processor may invoke logical instructions stored in the memory to execute the methods in the above embodiments.

[0125] Furthermore, the logical instructions in the aforementioned memory 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 this application, in essence, or the part that contributes to the prior art, or a portion 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 this application.

[0126] Based on the methods in the above embodiments, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0127] Based on the methods in the above embodiments, this application provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0128] It is understood that the processor in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0129] The method steps in this application embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0130] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0131] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0132] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for improving small-signal stability of a network-forming converter control, characterized in that, The power system and the grid-connected converter form a grid-connected system. The control method includes: Obtain the network model parameters of the power system, the electrical parameters and control parameters of the converter, and the operating status parameters of the grid-connected system; The state-space model of the grid-connected system corresponding to various typical active power control strategies is associated with all the obtained parameters. The maximum value of the deviation index of the grid-connected system in the stable parameter domain under each typical active power control strategy is determined. The median value of all the maximum deviation indices is used as the adaptive threshold of the deviation index. The deviation index is the relative error between the attenuation factor considering the dynamic coupling of reactive power and the attenuation factor ignoring the dynamic coupling of reactive power. The state-space model of the grid-connected system corresponding to the current active power control strategy is associated with all the acquired parameters to determine the maximum value of the deviation exponent of the grid-connected system in the stable parameter domain under the current active power control strategy. Based on the comparison between the maximum value of the deviation index of the grid-connected system in the stable parameter domain and the adaptive threshold of the deviation index under the current active power control strategy, a grid-type converter modeling method is selected. Based on the selected model, the control parameters are tuned to achieve stable control of the grid-type converter: if the maximum value of the deviation index of the grid-connected system in the stable parameter domain under the current active power control strategy exceeds the adaptive threshold of the deviation index, a grid-type converter model considering reactive power dynamic coupling is established; otherwise, a grid-type converter model ignoring reactive power dynamic coupling is adopted.

2. The control method according to claim 1, characterized by, If the grid-connected system is simplified to a second-order system with respect to angle, the state-space model of the grid-connected system corresponding to the active power control strategy is as follows: ； in, These are second-order, first-order, and zero-order coefficients, determined based on the obtained converter and power system parameters. Their values ​​differ depending on whether reactive power dynamics are considered or ignored. The output phase angle of the power control loop. These are the output phase angles of the power control loop. The small perturbation, the first derivative of the small perturbation, and the second derivative of the small perturbation.

3. The control method according to claim 2, characterized by, If the grid-connected system is simplified to a second-order system with respect to angle, the attenuation factor is calculated as follows: ； wherein is an attenuation factor.

4. The control method according to claim 1, characterized by, If the grid-connected system is simplified to a third-order system with respect to angle, the state-space model of the grid-connected system corresponding to the active power control strategy is as follows: ； in, These are third-order, second-order, first-order, and zero-order coefficients, determined based on the obtained converter and power system parameters. Their values ​​differ depending on whether reactive power dynamics are considered or ignored. The output phase angle of the power control loop. These are the output phase angles of the power control loop. Small perturbation, the first derivative of the small perturbation, the second derivative of the small perturbation, and the third derivative of the small perturbation.

5. The control method as described in claim 4, characterized in that, If the grid-connected system is simplified to a third-order system with respect to angle, the attenuation factor is calculated as follows: ； where the equivalent first order coefficient , the equivalent second order coefficient , is a decay factor.

6. The control method according to claim 1, characterized by, Within the stable parameter domain, feasible parameter combinations are iterated and calculated. For each feasible parameter combination, the deviation index is calculated, and then the maximum deviation index is determined. ； in, To account for the attenuation factor of reactive dynamic coupling, To ignore the attenuation factor of reactive dynamic coupling, the deviation index The larger the value, the more significant the impact of reactive power dynamics on stability assessment.

7. The control method according to claim 1, characterized by, The typical active power control strategies are pre-stored in the controller, including the following five types: droop control, proportional-derivative droop control, droop control with second-order derivative terms, virtual synchronous generator control, and virtual synchronous generator control with feedforward.

8. The control method according to claim 7, characterized by, The current active power control strategy is one of the typical active power control strategies or is different from the typical active power control strategy.

9. A networked converter control system with improved small signal stability, comprising: Includes memory and one or more processors; The memory is coupled to the one or more processors, and the memory is used to store computer program code, the computer program code including computer instructions; The one or more processors invoke the computer instructions to cause the system to perform the control method as described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that, Includes instructions that, when executed on an electronic device, cause the electronic device to perform the control method as described in any one of claims 1-8.

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