An angular frequency amplitude limiting setting method and system for ensuring global stability of a network device

Abstract

This invention relates to the field of transient stability assessment technology for converters, providing a method and system for angular frequency limiting tuning to ensure the global stability of grid-connected converters. The method includes extending the single-pendulum deceleration process of a virtual synchronous machine into a multi-pendulum deceleration process, and determining the upper limit of the angular frequency limiting based on the stability conditions of the multi-pendulum. During the single-pendulum deceleration process of the virtual synchronous machine, the effects of potential energy and damping dissipation energy are considered simultaneously, and the damping dissipation energy is approximated and quantified using the concavity and convexity of the angular frequency trajectory. Based on the potential energy and the approximate quantified damping dissipation energy, the maximum upper limit of the required angular frequency limiting is solved using the deceleration critical stability condition of the last pendulum in the multi-pendulum deceleration process, thus completing the transient stability assessment technology of angular frequency limiting tuning to ensure the global stability of the grid-connected converter. It can use angular frequency limiting control to ensure that the virtual synchronous machine recovers synchronous and stable operation at least within the period of a single pendulum, while simultaneously considering the damping effect to obtain a larger upper limit of the angular frequency limiting tuning.

Description

Technical Field

[0001] This invention relates to the field of transient stability assessment technology for converters, and in particular to an angular frequency limiting tuning method and system for ensuring the global stability of a grid-connected device. Background Technology

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

[0003] During grid voltage dips, the fault current in grid-connected inverters can exceed the withstand capability of power electronic devices. Therefore, grid-connected devices are equipped with current-limiting strategies to prevent damage to semiconductor devices. Grid-connected inverters using virtual synchronous machine (VSM) control are currently the mainstream approach for grid control. The introduction of current-limiting devices significantly reduces power output during VSM faults, worsening the transient stability of the grid-connected system.

[0004] To improve the transient stability of a virtual synchronous machine grid-connected system, one can focus on reducing the system's kinetic energy and increasing its potential energy. Currently, most strategies to enhance transient stability involve increasing the potential energy, such as adjusting current-limiting parameters to increase the output power after a fault. However, this method is limited to priority strategies and lacks universality. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an angular frequency limiting tuning method and system that ensures the global stability of a network-building device. This method utilizes angular frequency limiting control to ensure that the virtual synchronizing machine recovers synchronous and stable operation at least within the period of a single pendulum, while also taking into account damping effects to obtain a larger upper limit for angular frequency limiting tuning.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides an angular frequency limiting tuning method to ensure global stability of a network-forming device.

[0007] In one or more embodiments, an angular frequency limiting tuning method is provided to ensure the global stability of a network-forming device, including: Under normal circumstances, a power synchronization circuit containing an integrator is used to simulate a virtual synchronous machine to control the grid-type converter in constant voltage mode. During a fault, a virtual impedance current limiting strategy is used to control the grid-type converter in current limiting mode, and when the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is used. Based on the system current equation of the grid-type converter, the mode switching power angle range corresponding to the switch from constant voltage mode to virtual impedance current limiting mode is determined; based on the fact that the integrator input of the power synchronization link is less than zero, the departure power angle range for exiting angular frequency limiting is determined. Based on the duration of the fault, the relationship between the fault clearing angle and the range of the mode switching power angle and the range of the departure power angle is matched to determine the corresponding pendulum deceleration process of the virtual synchronizer. The single pendulum deceleration process of the virtual synchronizer is extended to a multi-pendulum deceleration process, and the upper limit of the angular frequency limit is set based on the stability condition of the multi-pendulum. During the deceleration process of a single pendulum in a virtual synchronous machine, the effects of potential energy and damping dissipation energy are considered simultaneously, and the damping dissipation energy is approximated by the concavity and convexity of the angular frequency trajectory. Based on potential energy and approximate quantization of damped dissipation energy, the critical stability condition of the last pendulum deceleration process in the multi-pendulum deceleration process is used to solve the upper limit of the maximum angular frequency limit required for tuning, thereby completing the technical field of transient stability assessment of angular frequency limit tuning to ensure the global stability of grid converter.

[0008] As one implementation method, when the power angle Belongs to set When the virtual impedance current limiting strategy is triggered: ; In the formula, k For any integer, and The first k The lower and upper limits of the power angle range of the effect of periodic virtual impedance.

[0009] As one implementation method, the exit condition for angular frequency limiting is: ; in, and These are the active power reference value and actual output value of the grid-type converter, respectively. The damping coefficient; This is the upper limit of the angular frequency limit.

[0010] As one implementation method, when the integrator input of the power synchronization link is less than zero, the virtual synchronizing machine exits the angular frequency limiting in two different modes: constant voltage and constant current. By solving the conditions for exiting the angular frequency limiting in these two modes and taking the union of the two sets obtained from the solution, the range of the power angle at which the angular frequency limiting is exited can be obtained.

[0011] As one implementation method, if the fault duration is less than the set duration, the fault clearing angle is the intersection of the operating power angle range of the virtual synchronous machine in constant voltage mode and the departure power angle range of exiting the angular frequency limit. At the moment of fault clearing, the virtual synchronous machine switches back to constant voltage mode and exits the angular frequency limit. When the power angle exceeds the upper limit of the mode switching boundary, the virtual synchronous machine switches from constant voltage mode to constant current mode. The angular frequency gradually decelerates to 0 in constant current mode. In this case, part of the deceleration area of ​​the virtual synchronous machine is enclosed by the constant voltage curve and the active power reference value of the grid-type converter, and the other part is enclosed by the constant current curve and the active power reference value of the grid-type converter.

[0012] As one implementation method, if the fault duration is greater than or equal to the set duration, the fault clearing angle is the intersection of the power angle range triggered by the virtual impedance current limiting strategy and the departure power angle range of the exit angular frequency limiting. At the moment of fault clearing, the virtual synchronous machine maintains operation in constant current mode and exits angular frequency limiting. Subsequently, the angular frequency gradually decelerates to 0 in constant current mode. In this case, the deceleration area of ​​the virtual synchronous machine is enclosed by the constant current curve and the active power reference value of the grid-type converter.

[0013] As one implementation method, the transient description of the global critical stability of the grid converter is as follows: after the virtual synchronous machine exits the angular frequency limiting mode in constant voltage mode, its dynamic process can recover stability in the last swing; from an energy perspective, it can be expressed as: the kinetic energy after exiting the angular frequency limiting mode is completely converted into potential energy and damped dissipation energy before reaching the unstable equilibrium point of the current limiting mode.

[0014] A second aspect of the present invention provides an angular frequency limiting tuning system that ensures the global stability of a network-forming device.

[0015] In one or more embodiments, an angular frequency limiting tuning system for ensuring global stability of a network-forming device includes: The mode control module is used to simulate a virtual synchronous machine using a power synchronization link containing an integrator under normal conditions to control the grid-type converter in constant voltage mode control; during faults, a virtual impedance current limiting strategy is used to control the grid-type converter in current limiting mode, and when the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is used. The switching power angle determination module is used to determine the mode switching power angle range corresponding to the switch from constant voltage mode to virtual impedance current limiting mode based on the system current equation of the grid-type converter; and to determine the departure power angle range for exiting angular frequency limiting based on the integrator input of the power synchronization link being less than zero. The pendulum deceleration determination module is used to determine the corresponding pendulum deceleration process of the virtual synchronizer by matching the relationship between the fault clearing angle, the mode switching power angle range, and the departure power angle range based on the fault duration. The angular frequency limiting preliminary setting module is used to extend the single pendulum deceleration process of the virtual synchronizer into a multi-pendulum deceleration process, and set the upper limit of the angular frequency limiting based on the stability conditions of the multi-pendulum. The potential energy and dissipated energy calculation module is used to simultaneously consider the effects of potential energy and damped dissipated energy during the deceleration process of a single pendulum in a virtual synchronous machine, and to approximate the damped dissipated energy by utilizing the concavity and convexity of the angular frequency trajectory. The angular frequency limiting global tuning module is used to solve for the maximum angular frequency limiting limit required by the deceleration critical stability condition of the last pendulum in the multi-pendulum deceleration process based on potential energy and approximate quantized damping dissipation energy, thereby completing the technical field of angular frequency limiting tuning transient stability assessment to ensure the global stability of the grid converter.

[0016] A third aspect of the present invention provides a computer-readable storage medium.

[0017] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the angular frequency limiting tuning method for ensuring global stability of a network device as described above.

[0018] A fourth aspect of the present invention provides an electronic device.

[0019] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the angular frequency limiting tuning method for ensuring global stability of a network device as described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention combines the power synchronization link containing the integrator to simulate a virtual synchronous machine with a virtual impedance current limiting strategy, and controls the normal state and fault state of the grid-type converter respectively. During the fault, the virtual synchronous machine is used to accelerate to the upper limit of the angular frequency to realize the angular frequency limiting action, which improves the transient stability of the virtual synchronous machine. It is also found that by reasonably setting the upper limit of the angular frequency limiting, not only can the first swing transient stability of the virtual synchronous machine be enhanced, but also the transient synchronization stability of the virtual synchronous machine can be ensured, which provides a feasible strategy for solving the transient instability problem of the virtual synchronous machine.

[0021] (2) This invention solves for the first time the power angle range of the virtual impedance current limiting strategy and the angular frequency limiting action and exit, and analyzes the transient process of the multi-limited virtual synchronous machine. It not only involves a single pendulum, but also the transient stability of multiple pendulums under severe fault conditions, providing a theoretical basis for the parameter tuning of the multi-limited virtual synchronous machine.

[0022] (3) The angular frequency limiting method proposed in this invention takes into account the influence of potential energy and damping dissipation energy during deceleration, which effectively reduces the conservatism of the upper limit setting of angular frequency limiting and can provide guidance for the setting of the upper limit of angular frequency limiting of virtual synchronizer. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 This is a flowchart of an angular frequency limiting adjustment method for ensuring global stability of a network structure device according to an embodiment of the present invention.

[0025] Figure 2 This is a block diagram of a standalone network-connected virtual synchronous machine system according to an embodiment of the present invention.

[0026] Figure 3 This is a control structure for a virtual synchronous machine power synchronization link with added angular frequency limiting, as described in an embodiment of the present invention.

[0027] Figure 4 This is the power angle curve of the multi-amplitude virtual synchronizer in an embodiment of the present invention.

[0028] Figure 5 These are two transient stability conditions of active power and angular frequency within the range of a simple pendulum according to an embodiment of the present invention.

[0029] Figure 6 This describes the transient stability of active power and angular frequency across multiple pendulum ranges in an embodiment of the present invention.

[0030] Figure 7 This is a simplified linear schematic diagram of the damping effect of the transient stability of multiple pendulums according to an embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] Figure 1 A schematic diagram of the angular frequency limiting tuning method for ensuring global stability of the network structure device according to an embodiment of the present invention is provided. Figure 1 The angular frequency limiting tuning method for ensuring the global stability of the network-forming device in this embodiment may include the following steps: Step 1: Under normal circumstances, a virtual synchronous machine is simulated using a power synchronization link containing an integrator to control the grid-type converter in constant voltage mode control; during a fault, a virtual impedance current limiting strategy is used to control the grid-type converter in current limiting mode, and when the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is used.

[0035] In practice, under normal circumstances, the grid-type converter uses virtual synchronous machine control, achieving constant voltage mode control through a dual closed-loop voltage and current control. During fault periods, a virtual impedance current limiting strategy is employed to prevent overcurrent damage to the grid-type equipment. When the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is activated to avoid transient synchronization instability.

[0036] The power synchronization element of a grid-connected converter simulates the second-order rotor motion equation of a synchronous machine. Combined with an energy storage system, it can provide inertia and damping support for the power system, such as... Figure 2 The governing equation shown can be expressed as: (1) (2) In the formula, d is the differential operator; The phase angle is the difference between the virtual synchronous machine and the power grid. For time; and These are the per-unit virtual synchronous machine and the angular frequency of the power grid, respectively. This is the reference value for angular frequency; This is virtual inertia; and These are the active power reference value and actual output value of the grid-type converter, respectively. is the damping coefficient.

[0037] The virtual impedance current limiting device achieves current limiting by lowering the grid connection point voltage reference value. Therefore, the virtual synchronous machine can maintain its voltage source characteristics during faults. The specific method for setting the virtual impedance is as follows: (3) In the formula, and These are virtual resistance and virtual reactance, respectively; The current output by the virtual synchronous machine; This is the set trigger threshold for the current limiting device. When the actual output current of the grid-connected converter exceeds the threshold, the virtual impedance is activated. Otherwise, the virtual impedance is set to 0.

[0038] Under normal circumstances, the virtual synchronous machine operates in constant voltage mode, and its external characteristics are equivalent to a constant voltage source, therefore its equivalent internal resistance is very small. Ignoring the dynamic process of the inner current loop, the output current can be calculated from the main circuit structure and Ohm's law: (4) In the formula, and For the grid voltage vector and magnitude; and These are the reference voltage vector and magnitude at the grid connection point, respectively. Equivalent reactance of the power grid; It is an imaginary number; For the angle of attack.

[0039] The set of work angles that satisfy equation (4) is defined as When the angle Belongs to set When the virtual impedance current limiting strategy is triggered: ; In the formula, k For any integer, and The first k The lower and upper limits of the power angle range of the effect of periodic virtual impedance.

[0040] Step 2: Based on the system current equation of the grid converter, determine the mode switching power angle range corresponding to the switch from constant voltage mode to virtual impedance current limiting mode; based on the fact that the integrator input of the power synchronization link is less than zero, determine the departure power angle range for exiting angular frequency limiting.

[0041] like Figure 3 As shown, angular frequency limiting control is directly applied to the integrator of the power synchronization circuit. During the angular frequency limiting period, the input quantity of the integrator... The output is always greater than 0 and remains at the upper limit of the angular frequency limit. However, as the output power decreases, once the input quantity... If the value is less than 0, the integrator's output value will immediately drop from the upper limit. Upon impact, the angular frequency limiting function is deactivated. From the above analysis, the deactivation condition for the angular frequency limiting is: (6) When the integrator input of the power synchronization link is less than zero, the virtual synchronizing machine exits the angular frequency limiting in two different modes: constant voltage and constant current. By solving the conditions for exiting the angular frequency limiting in these two modes and taking the union of the two sets obtained from the solution, the range of the power angle at which the angular frequency limiting is exited can be obtained.

[0042] Specifically, the virtual synchronous machine may exit angular frequency limiting in two different modes: constant voltage and constant current. The conditions for exiting angular frequency limiting in the two modes are as follows: (7) (8) In the formula, The magnitude of the voltage at the grid connection point; This indicates the operating power angle range of the virtual synchronous machine in constant voltage mode.

[0043] Solving equations (7) and (8) and taking the union of the two sets yields the following results: Figure 4 As shown, the departure power angle range T for exiting angular frequency limiting: (9) In the formula, T represents the range of departure work angles. and These are the lower and upper limits of the departure power angle range for the k-th cycle, respectively.

[0044] Step 3: Based on the duration of the fault, match the relationship between the fault clearing angle and the range of the mode switching power angle and the range of the departure power angle to determine the corresponding pendulum deceleration process of the virtual synchronizer.

[0045] Under the combined effect of multiple limiting conditions, the operating conditions of the virtual synchronous machine exhibit partitioning characteristics, therefore its pendulum transient process also needs to be discussed on a case-by-case basis.

[0046] If the fault duration is less than the set duration, such as Figure 5 As shown in Figure (a), the fault clearing angle That is, the fault clearing angle is the intersection of the operating power angle range of the virtual synchronous machine in constant voltage mode and the departure power angle range of the exit angular frequency limit. At the moment of fault clearing, the virtual synchronous machine switches back to constant voltage mode and exits angular frequency limit. When the power angle exceeds the upper limit of the mode switching boundary, the virtual synchronous machine switches from constant voltage mode to constant current mode. The angular frequency gradually decelerates to 0 in constant current mode. In this case, part of the deceleration area of ​​the virtual synchronous machine is enclosed by the constant voltage curve and the active power reference value of the grid-type converter, and the other part is enclosed by the constant current curve and the active power reference value of the grid-type converter.

[0047] If the fault duration is greater than or equal to the set duration, such as Figure 5 As shown in Figure (b), the fault clearing angle That is, the fault clearing angle is the intersection of the power angle range triggered by the virtual impedance current limiting strategy and the departure power angle range of the exit angular frequency limiting. At the moment of fault clearing, the virtual synchronous machine maintains operation in constant current mode and exits angular frequency limiting. Subsequently, the angular frequency gradually decelerates to 0 in constant current mode. In this case, the deceleration area of ​​the virtual synchronous machine is enclosed by the constant current curve and the active power reference value of the grid-type converter.

[0048] Step 4: Extend the single pendulum deceleration process of the virtual synchronizer into a multi-pendulum deceleration process, and set the upper limit of the angular frequency limit based on the stability conditions of the multi-pendulum.

[0049] As shown in equation (6), a larger output active power is beneficial for exiting the angular frequency limiting effect. Output power of the virtual synchronous machine in constant current mode. The frequency limit decreases as the power angle increases. Therefore, if the virtual synchronizer does not exit the angular frequency limit at the fault clearing time, it will be unable to exit the angular frequency limit during the entire first swing, and the transient process will extend to the multi-swing range.

[0050] The transient stability process of multiple pendulums under severe fault conditions is analyzed, and the upper limit of the angular frequency limit is set based on the critical condition of the stability of multiple pendulums.

[0051] Analysis of the transient stability process of a simple pendulum shows that if the fault is very severe, it will lead to a fault clearance angle. Therefore, within the first swing range, the virtual synchronizer cannot exit the angular frequency limiting. The power angle continues to increase until it reaches the boundary of the second swing's departure range, after which deceleration begins. For example... Figure 6 As shown, the deceleration process is similar to the transient process of a simple pendulum. During deceleration, a mode switch occurs, and the deceleration slows down to a certain point before reaching the unstable equilibrium point. And eventually stabilizes at the stable equilibrium point of the second pendulum. Therefore, through proper tuning No matter how long the fault lasts, the virtual synchronous machine under angular frequency limiting can always recover stability at least in the next swing.

[0052] During the deceleration process of the pendulum, kinetic energy is converted into potential energy and damped dissipated energy. This energy conversion can be expressed as follows: (10) In the formula, This is the upper limit of the angular frequency limiting setting. This represents the unstable equilibrium point for the virtual synchronizer operating in rate-limited mode. and These represent the output power of the virtual synchronous machine in constant voltage mode and current-limiting mode, respectively.

[0053] Step 5: During the deceleration process of the pendulum in the virtual synchronizer, the effects of potential energy and damping dissipation energy are considered simultaneously, and the damping dissipation energy is approximated by the concavity and convexity of the angular frequency trajectory.

[0054] To obtain the accurate magnitude of damping dissipation energy during deceleration, one method is to use numerical integration. However, this method only calculates the numerical value of the damping dissipation energy and cannot reveal its impact mechanism on transient stability. Therefore, the calculation of damping dissipation energy is linearized by utilizing the concavity and convexity of the angular frequency trajectory, thus avoiding numerical integration.

[0055] Based on the concavity and convexity of the angular frequency trajectory during deceleration, and considering the conservatism of transient stability analysis, the damped deceleration area is simplified to approximately linear. For example... Figure 7 As shown, the deceleration area in constant voltage mode is equivalent to a trapezoid, and the deceleration area in current-limiting mode is equivalent to a triangle. This approximation can be expressed by the equation: (11) (12) In the formula, This represents the deceleration area under constant voltage mode. This refers to the deceleration area under current-limiting mode. This refers to the angular frequency of the virtual synchronizer when the current limiting mode switches during deceleration.

[0056] Step 6: Based on potential energy and approximate quantization of damped dissipation energy, and utilizing the critical stability condition of the last pendulum in the multi-pendulum deceleration process, solve for the maximum angular frequency limit upper limit required for tuning, thereby completing the technical field of transient stability assessment for angular frequency limit tuning to ensure the global stability of the grid converter.

[0057] The transient description of the global critical stability of the type converter is as follows: After the virtual synchronous machine exits the angular frequency limiting mode in constant voltage mode, its dynamic process can recover stability in the last swing; from an energy perspective, it can be expressed as: the kinetic energy after exiting the angular frequency limiting mode is completely converted into potential energy and damped dissipation energy before reaching the unstable equilibrium point of the current limiting mode.

[0058] The change in potential energy during deceleration can be directly calculated using the following formula: (13) In the formula, The potential energy deceleration area represents the change in potential energy.

[0059] The damping dissipation energy during deceleration can be calculated using equations (11) and (12), where the unknowns are: , and .

[0060] The angular frequency limiting exit condition can be expressed as follows: (14) The conversion relationship between kinetic energy, potential energy, and damping dissipation energy during the deceleration process can be expressed as follows: (15) The damping area in equation (153) also needs to be solved by integration, but to avoid integration, the damping area is... Enlarging the area to a rectangle makes the solution easier. The value is less than the actual value, thus ensuring the conservatism of the parameter tuning. Equation (15) can be written as (16) By using equations (14) and (16) and Represented as The function.

[0061] In summary, the critical stability condition for the virtual synchronizer to achieve synchronization stability under multiple limiting effects can be expressed as follows: (17) Equation (17) contains only variables Therefore, the maximum setting value of the angular frequency limiting element can be obtained by solving the critical stability condition.

[0062] In one or more embodiments, an angular frequency limiting tuning system for ensuring the global stability of a network-building device is also provided. This system can be implemented in software and includes the following software modules: a mode control module, a switching power angle determination module, a pendulum deceleration determination module, an angular frequency limiting preliminary tuning module, a potential energy and dissipated energy calculation module, and an angular frequency limiting global tuning module.

[0063] The functions of each software module in the angular frequency limiting tuning system that ensures the global stability of the network-connected device are described below: The mode control module is used to simulate a virtual synchronous machine using a power synchronization link containing an integrator under normal conditions to control the grid-type converter in constant voltage mode control; during faults, a virtual impedance current limiting strategy is used to control the grid-type converter in current limiting mode, and when the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is used. The switching power angle determination module is used to determine the mode switching power angle range corresponding to the switch from constant voltage mode to virtual impedance current limiting mode based on the system current equation of the grid-type converter; and to determine the departure power angle range for exiting angular frequency limiting based on the integrator input of the power synchronization link being less than zero. The pendulum deceleration determination module is used to determine the corresponding pendulum deceleration process of the virtual synchronizer by matching the relationship between the fault clearing angle, the mode switching power angle range, and the departure power angle range based on the fault duration. The angular frequency limiting preliminary setting module is used to extend the single pendulum deceleration process of the virtual synchronizer into a multi-pendulum deceleration process, and set the upper limit of the angular frequency limiting based on the stability conditions of the multi-pendulum. The potential energy and dissipated energy calculation module is used to simultaneously consider the effects of potential energy and damped dissipated energy during the deceleration process of a single pendulum in a virtual synchronous machine, and to approximate the damped dissipated energy by utilizing the concavity and convexity of the angular frequency trajectory. The angular frequency limiting global tuning module is used to solve for the maximum angular frequency limiting limit required by the deceleration critical stability condition of the last pendulum in the multi-pendulum deceleration process based on potential energy and approximate quantized damping dissipation energy, thereby completing the technical field of angular frequency limiting tuning transient stability assessment to ensure the global stability of the grid converter.

[0064] It should be noted that each module in the angular frequency limiting tuning system for ensuring global stability of the network device in the embodiments of the present invention corresponds one-to-one with each step in the angular frequency limiting tuning method for ensuring global stability of the network device in the above embodiments, and their specific implementation processes are the same, so they will not be repeated here.

[0065] The structure of the electronic device according to embodiments of the present invention will be described in detail below. The electronic device provided in the embodiments of the present invention includes: at least one processor, a memory, a user interface, and at least one network interface. The various components in the angular frequency limiting tuning system that ensures the global stability of the network device are coupled together through a bus system. It can be understood that the bus system is used to realize the connection and communication between these components. In addition to a data bus, the bus system also includes a power bus, a control bus, and a status signal bus. The user interface may include a display, keyboard, mouse, trackball, click wheel, buttons, a touchpad, or a touch screen, etc.

[0066] It is understood that the memory can be volatile memory or non-volatile memory, or both. The memory in this embodiment of the invention is capable of storing data to support the operation of the terminal. Examples of this data include any computer programs used to operate on the terminal, such as operating systems and applications. The operating system includes various system programs, such as the framework layer, core library layer, driver layer, etc., used to implement various basic services and handle hardware-based tasks. Applications can include various applications.

[0067] In some embodiments, the angular frequency limiting system for ensuring global stability of a network-building device provided in this invention can be implemented using a combination of hardware and software. For example, the angular frequency limiting system for ensuring global stability of a network-building device provided in this invention can be a processor in the form of a hardware decoding processor, programmed to execute the angular frequency limiting method for ensuring global stability of a network-building device provided in this invention. For instance, the processor in the form of a hardware decoding processor can employ one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), or other electronic components.

[0068] As an example, a processor can be an integrated circuit chip with signal processing capabilities, such as a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., where a general-purpose processor can be a microprocessor or any conventional processor, etc.

[0069] As an example of the hardware implementation of the angular frequency limiting system for ensuring global stability of a network device provided in this embodiment of the invention, the device provided in this embodiment of the invention can be directly executed by a processor in the form of a hardware decoding processor. For example, it can be executed by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), or other electronic components to implement the angular frequency limiting system for ensuring global stability of a network device provided in this embodiment of the invention.

[0070] The memory in this embodiment of the invention is used to store various types of data to support the operation of the angular frequency limiting tuning system that ensures the global stability of the network-forming device, or to store data for execution. Figure 1 The program code for the method shown. Examples of this data include: any executable instructions for operation on an angular frequency limiting tuning system that ensures global stability of a network-forming device, such as executable instructions. A program implementing the angular frequency limiting tuning method for ensuring global stability of a network-forming device according to embodiments of the present invention may be included in the executable instructions.

[0071] Specifically, according to embodiments of this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program including functions for executing... Figure 1 The program code for the method shown. In such an embodiment, the computer program can be downloaded and installed from a network via a communication component, and / or installed from a removable medium. When the computer program is executed by the central processing unit, it performs the various functions defined in the apparatus of this application.

[0072] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for angular frequency limiting tuning to ensure global stability of a network-forming device, characterized in that, include: Under normal circumstances, a virtual synchronous machine is simulated using a power synchronization circuit containing an integrator to control the grid-type converter in constant voltage mode. During a fault, a virtual impedance current limiting strategy is used to control the grid-type converter to be in current limiting mode, and when the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is used. Based on the system current equation of the grid-type converter, the mode switching power angle range corresponding to the switch from constant voltage mode to virtual impedance current limiting mode is determined; based on the fact that the integrator input of the power synchronization link is less than zero, the departure power angle range for exiting angular frequency limiting is determined. Based on the duration of the fault, the relationship between the fault clearing angle and the range of the mode switching power angle and the range of the departure power angle is matched to determine the corresponding pendulum deceleration process of the virtual synchronizer. The single pendulum deceleration process of the virtual synchronizer is extended to a multi-pendulum deceleration process, and the upper limit of the angular frequency limit is set based on the stability condition of the multi-pendulum. During the deceleration process of a single pendulum in a virtual synchronous machine, the effects of potential energy and damping dissipation energy are considered simultaneously, and the damping dissipation energy is approximated by the concavity and convexity of the angular frequency trajectory. Based on potential energy and approximate quantization of damped dissipation energy, the critical stability condition of the last pendulum deceleration process in the multi-pendulum deceleration process is used to solve the upper limit of the maximum angular frequency limit required for tuning, thereby completing the technical field of transient stability assessment of angular frequency limit tuning to ensure the global stability of grid converter.

2. The angular frequency limiting tuning method for ensuring global stability of a network-forming device as described in claim 1, characterized in that, When the angle Belongs to set When the virtual impedance current limiting strategy is triggered: ； In the formula, k For any integer, and The first k The lower and upper limits of the power angle range of the effect of periodic virtual impedance.

3. The angular frequency limiting tuning method for ensuring global stability of a network-forming device as described in claim 1, characterized in that, The exit condition for angular frequency limiting is: ； in, and These are the active power reference value and actual output value of the grid-type converter, respectively. The damping coefficient; This is the upper limit of the angular frequency limit.

4. The angular frequency limiting tuning method for ensuring global stability of a network-forming device as described in claim 1, characterized in that, When the integrator input of the power synchronization link is less than zero, the virtual synchronizing machine exits the angular frequency limiting in two different modes: constant voltage and constant current. By solving the conditions for exiting the angular frequency limiting in these two modes and taking the union of the two sets obtained from the solution, the range of the power angle at which the angular frequency limiting is exited can be obtained.

5. The angular frequency limiting tuning method for ensuring global stability of a network-forming device as described in claim 1, characterized in that, If the fault duration is less than the set duration, the fault clearing angle is the intersection of the operating power angle range of the virtual synchronous machine in constant voltage mode and the departure power angle range of the exit angular frequency limiting. At the moment the fault is cleared, the virtual synchronous machine switches back to constant voltage mode and exits angular frequency limiting. When the power angle exceeds the upper limit of the mode switching boundary, the virtual synchronous machine switches from constant voltage mode back to constant current mode. The angular frequency gradually decelerates to 0 in constant current mode. In this case, part of the deceleration area of ​​the virtual synchronous machine is enclosed by the constant voltage curve and the active power reference value of the grid-type converter, and the other part is enclosed by the constant current curve and the active power reference value of the grid-type converter.

6. The angular frequency limiting tuning method for ensuring global stability of a network-forming device as described in claim 1, characterized in that, If the fault duration is greater than or equal to the set duration, the fault clearing angle is the intersection of the power angle range triggered by the virtual impedance current limiting strategy and the departure power angle range of the exit angular frequency limiting. At the moment of fault clearing, the virtual synchronous machine maintains operation in constant current mode and exits angular frequency limiting. Subsequently, the angular frequency gradually decelerates to 0 in constant current mode. In this case, the deceleration area of ​​the virtual synchronous machine is enclosed by the constant current curve and the active power reference value of the grid-type converter.

7. The angular frequency limiting tuning method for ensuring global stability of a network-forming device as described in claim 1, characterized in that, The transient description of the global critical stability of the grid converter is as follows: After the virtual synchronous machine exits the angular frequency limiting mode in constant voltage mode, its dynamic process can recover stability in the last swing; from an energy perspective, it can be expressed as: the kinetic energy after exiting the angular frequency limiting mode is completely converted into potential energy and damped dissipation energy before reaching the unstable equilibrium point of the current limiting mode.

8. An angular frequency limiting tuning system for ensuring global stability of a network-forming device, characterized in that, The angular frequency limiting tuning method for ensuring global stability of a network-building device, as described in any one of claims 1-7, includes: The mode control module is used to simulate a virtual synchronous machine using a power synchronization link containing an integrator under normal conditions to control the grid-type converter in constant voltage mode control; during faults, a virtual impedance current limiting strategy is used to control the grid-type converter in current limiting mode, and when the virtual synchronous machine accelerates to the upper limit of the angular frequency, the angular frequency limiting action is used. The switching power angle determination module is used to determine the mode switching power angle range corresponding to the switch from constant voltage mode to virtual impedance current limiting mode based on the system current equation of the grid-type converter; and to determine the departure power angle range for exiting angular frequency limiting based on the integrator input of the power synchronization link being less than zero. The pendulum deceleration determination module is used to determine the corresponding pendulum deceleration process of the virtual synchronizer by matching the relationship between the fault clearing angle, the mode switching power angle range, and the departure power angle range based on the fault duration. The angular frequency limiting preliminary setting module is used to extend the single pendulum deceleration process of the virtual synchronizer into a multi-pendulum deceleration process, and set the upper limit of the angular frequency limiting based on the stability conditions of the multi-pendulum. The potential energy and dissipated energy calculation module is used to simultaneously consider the effects of potential energy and damped dissipated energy during the deceleration process of a single pendulum in a virtual synchronous machine, and to approximate the damped dissipated energy by utilizing the concavity and convexity of the angular frequency trajectory. The angular frequency limiting global tuning module is used to solve for the maximum angular frequency limiting limit required by the deceleration critical stability condition of the last pendulum in the multi-pendulum deceleration process based on potential energy and approximate quantized damping dissipation energy, thereby completing the technical field of angular frequency limiting tuning transient stability assessment to ensure the global stability of the grid converter.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the angular frequency limiting tuning method for ensuring global stability of the network structure as described in any one of claims 1-7.

10. 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 steps in the angular frequency limiting tuning method for ensuring global stability of the network structure device as described in any one of claims 1-7.

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