Adaptive virtual resistance control method and system based on power feedback switching

Abstract

The application belongs to the technical field of VSG control, and specifically discloses a self-adaptive virtual resistance control method and system based on power feedback switching, which comprises the following steps: monitoring the state of an electric network in real time, and judging the running state of a control system of a virtual synchronous generator; according to the running state of the control system of the virtual synchronous generator, switching actual active power or virtual active power at a grid-connected point of the virtual synchronous generator as a feedback quantity of an active power control loop of the control system of the virtual synchronous generator, so that the mathematical effect of the virtual resistance in a transient process is equivalent to the effect of a real grid line resistance, and self-adaptive virtual resistance control is completed. The application solves the conflict problem between small signal stability improvement and transient stability deterioration caused by the virtual resistance.

Description

Technical Field

[0001] This invention belongs to the field of VSG control technology, specifically relating to an adaptive virtual resistance control method and system based on power feedback switching. Background Technology

[0002] As the global energy structure shifts towards cleaner and lower-carbon energy, new energy sources, such as wind and solar power, are being integrated into modern power grids in large quantities. New energy power generation devices are primarily connected to the grid via power electronic inverters, resulting in a high proportion of power electronic characteristics in the grid. However, traditional inverters typically employ a phase-locked loop (PLL)-based grid-connected control strategy, which is essentially a grid-following (GFL) current source, lacking inertia support and voltage regulation capabilities. With the increasing penetration rate of new energy sources at inverter interfaces, the proportion of traditional synchronous generators in the grid is correspondingly decreasing, leading to a significant reduction in the inertia of the entire power system and posing serious challenges to frequency and voltage stability.

[0003] To address this challenge, Virtual Synchronous Generator (VSG) control was proposed. The core idea of ​​VSG control is to simulate the rotor motion equations and excitation regulation characteristics of a traditional synchronous generator in the control algorithm of the grid-connected inverter, so that it exhibits the inertia, damping, and voltage support characteristics of a synchronous generator.

[0004] Despite the significant advantages of VSG control technology, it still faces a series of stability issues in practical applications. Small-signal stability and transient synchronization stability are two crucial aspects. Small-signal stability primarily focuses on the system's dynamic response to minor disturbances. A typical VSG small-signal instability phenomenon is synchronous resonance (SR). This problem stems from the inherent interaction between the VSG's power control loop and the grid-side inductance, especially in scenarios with high line reactance / resistance (X / R). Insufficient system damping easily leads to sustained power oscillations near the synchronization frequency, which can severely cause system runaway. To effectively suppress synchronous resonance, the introduction of a virtual resistance (VR) into the control loop is commonly used in engineering. By simulating a series resistor, VR can significantly increase the system's equivalent damping, and compared to a physical series resistor, it does not generate additional power loss, thus becoming an efficient and economical SR suppression solution.

[0005] However, the voltage-resonance ratio (VR) used to improve small-signal stability negatively impacts the transient synchronization stability of the VSG. Transient synchronization stability refers to the VSG's ability to maintain synchronization with the grid after experiencing large disturbances such as grid voltage drops and line faults. Studies show that the presence of VR worsens the VSG's power angle characteristics and reduces its maximum power transfer capability during transient processes. This leads to a contraction of the system's transient stability domain and a shortened critical clearing time. Therefore, the larger the introduced VR, the weaker the VSG's ability to resist large disturbances, and the more prone it is to losing synchronization and disconnecting from the grid during faults. However, actual line resistance is beneficial to transient stability. Therefore, existing VSG VR control technology presents the following contradiction: to ensure stable small-signal operation, VR must be introduced to suppress synchronous resonance; however, to ensure transient stability under large disturbances, it is desirable to reduce or even remove VR. This contradiction limits the performance and reliability of VSGs in complex grid environments.

[0006] To address this issue, researchers have proposed several strategies to enhance transient stability, such as transient damping control, adaptive inertia adjustment, mode switching control, and optimization of power angle characteristics. However, most of these methods compensate for or improve transient stability under the assumption that virtual resistance exists, and do not fundamentally solve the negative transient stability effects inherent in VR itself. Other methods, such as instantaneous VR technology, while attempting to distinguish between high-frequency and low-frequency disturbances, have limited effectiveness in improving transient stability.

[0007] In summary, an innovative VSG control method is needed to resolve the inherent conflict between small-signal stability and transient synchronization stability caused by VR. Utilizing VR can effectively suppress SR while simultaneously enhancing the system's transient synchronization stability. This has significant theoretical and engineering value for improving the maturity and widespread application of VSG technology. Summary of the Invention

[0008] The purpose of this invention is to resolve the conflict between the improvement in small-signal stability and the deterioration in transient stability caused by virtual resistance, and to propose an adaptive virtual resistance control method and system based on power feedback switching.

[0009] The technical solution of the present invention is as follows: Firstly, an adaptive virtual resistance control method based on power feedback switching, comprising the following steps: Real-time monitoring of the power grid status to determine the operating status of the virtual synchronous generator's control system; Based on the operating status of the virtual synchronous generator's control system, the actual active power or virtual active power at the virtual synchronous generator's grid connection point is switched as the feedback quantity of the active power control loop of the virtual synchronous generator's control system, so that the mathematical effect of the virtual resistance in the transient process is equivalent to the effect of the real power grid line resistance, thus completing adaptive virtual resistance control.

[0010] Preferably, the operating status includes normal operating mode and fault operating mode; Real-time monitoring of the power grid status and determination of the operating status of the virtual synchronous generator control system specifically includes the following steps: Collect the instantaneous three-phase voltage values ​​at the PCC point; Transform the instantaneous values ​​of the three-phase voltages to the dq coordinate system to obtain the d-axis voltage components and q-axis voltage components, and calculate the effective amplitude of the PCC voltage based on the d-axis voltage components and q-axis voltage components. The effective amplitude of the PCC voltage is compared with the preset fault start threshold and fault recovery threshold to determine whether the control system of the virtual synchronous generator has failed.

[0011] Preferably, the effective amplitude of the PCC voltage | V PCC The formula for calculating | is:

[0012] in, V d Represents the d-axis voltage component. V q This represents the q-axis voltage component.

[0013] Preferably, based on the operating status of the virtual synchronous generator's control system, the actual active power or virtual active power at the grid connection point of the virtual synchronous generator is switched as the feedback quantity of the active power control loop of the virtual synchronous generator's control system, specifically: In normal operating mode, the actual active power is used as the feedback quantity of the active power control loop; In fault operation mode, virtual active power is used as the feedback quantity of active power control loop. The virtual resistance parameter is adjusted by calculating the adaptive virtual resistance increment according to the fault degree, so that the influence of virtual resistance on transient characteristics is equivalent to grid resistance. This achieves simultaneous improvement of small signal damping enhancement and transient stability, thus completing adaptive virtual resistance control.

[0014] As a preferred method, the virtual resistance parameters are adjusted by calculating the adaptive virtual resistance increment based on the fault severity, specifically as follows: Set the basic virtual resistance value to ensure small-signal stability; The deviation between the rated voltage amplitude and the effective amplitude of the PCC voltage is calculated in real time to obtain the voltage deviation factor characterizing the severity of the fault. Multiplying the voltage deviation factor by the virtual resistance gain coefficient yields the adaptive virtual resistance increment; The total virtual resistance value under different fault conditions is obtained by adding the adaptive virtual resistance increment and the basic virtual resistance value, thus completing the adjustment of the virtual resistance parameter.

[0015] Preferably, the effective amplitude of the PCC voltage is compared with preset fault initiation thresholds and fault recovery thresholds to determine whether the control system of the virtual synchronous generator has failed. Specifically: If the effective amplitude of the PCC voltage is greater than or equal to the preset fault initiation threshold, then no fault has occurred. If the effective amplitude of the PCC voltage is less than the preset fault initiation threshold, a suspected fault signal is output. If the duration of the suspected fault signal exceeds the first preset delay, it is determined that the control system of the virtual synchronous generator has failed. If the effective amplitude of the PCC voltage is greater than the fault recovery threshold, a fault clearing signal is output. If the duration of the fault clearing signal exceeds the second preset delay, it is determined that the control system of the virtual synchronous generator has been cleared.

[0016] As a preferred option, the formula for calculating actual active power is:

[0017] in, Indicates actual active power. Represents the d-axis voltage component. Represents the q-axis voltage component. Indicates the current flowing into the power grid I g d-axis component, Indicates the current flowing into the power grid I g q-axis component; The formula for calculating virtual active power is:

[0018] in, Indicates virtual active power. This represents the reference voltage generated by the reactive voltage loop. V ref d-axis component, This represents the reference voltage generated by the reactive voltage loop. V ref The q-axis component.

[0019] The beneficial effects of this invention are: 1. This invention improves the power feedback in the VSG swing equation by replacing the traditional actual active power at the PCC point with virtual active power after a fault is detected. The virtual active power is calculated at a virtual PCC point before the introduction of virtual resistance. This invention makes the mathematical effect of the virtual resistance during system transients equivalent to the effect of the actual grid line resistance. Therefore, this invention can both enhance the VSG small-signal and be equivalent to line resistance during transients, thus enhancing transient stability.

[0020] 2. This invention simplifies parameter tuning; only one adaptive virtual resistance value needs to be set in the controller. This completely solves the problem in the prior art. R v The value needs to be limited to suppress synchronous resonance in order to ensure transient stability. R v The complexity of the control logic, such as the selection of values ​​or the addition of additional fault response measures, is greatly simplified, thereby simplifying the design and parameter tuning process of the controller.

[0021] 3. This invention has a simple structure, is easy to implement, and has high scalability. It only requires the addition of a fault detection module and a virtual power feedback signal, without the need for complex adaptive algorithms. This modification requires minimal alteration to existing VSG control systems, increases computational burden very little, and is easily implemented on existing hardware platforms. Furthermore, the framework of this invention is fundamental and can be combined with other existing transient stability enhancement methods (such as transient damping, adaptive inertia, etc.) to further improve system performance, exhibiting strong technical compatibility and scalability.

[0022] Secondly, an adaptive virtual resistance control system based on power feedback switching includes: The fault detection module is used to monitor the power grid status in real time and determine the operating status of the virtual synchronous generator's control system. The control switching module is used to switch the actual active power or virtual active power at the grid connection point of the virtual synchronous generator as the feedback quantity of the active power control loop of the virtual synchronous generator control system according to the operating status of the virtual synchronous generator control system. This makes the mathematical effect of the virtual resistance in the transient process equivalent to the effect of the real power grid line resistance, thus completing adaptive virtual resistance control.

[0023] Preferably, the fault detection module includes: The signal acquisition unit is used to acquire the instantaneous values ​​of the three-phase voltage at the PCC point; The feature calculation unit is used to transform the instantaneous values ​​of the three-phase voltage to the dq coordinate system to obtain the d-axis voltage component and the q-axis voltage component, and calculate the effective amplitude of the PCC voltage based on the d-axis voltage component and the q-axis voltage component. The logic judgment unit is used to compare the effective amplitude of the PCC voltage with the preset fault start threshold and fault recovery threshold to determine whether the control system of the virtual synchronous generator has failed.

[0024] Thirdly, a non-transitory computer-readable storage medium is provided that stores computer instructions for causing a computer to perform the method as described in the first aspect. Attached Figure Description

[0025] Figure 1 The diagram shows a flowchart of an adaptive virtual resistance control method based on power feedback switching.

[0026] Figure 2 The diagram shows the VSG grid topology and control structure.

[0027] Figure 3 The diagram shows the equivalent circuit of the VSG grid-connected system after adding a virtual resistor.

[0028] Figure 4 The following are different R v , R g Down P e and θ Gg Relationship curve.

[0029] Figure 5 The diagram shown is a schematic of the fault detection module.

[0030] Figure 6 The figure shows the active power response of the VSG with and without virtual resistors.

[0031] Figure 7 The figure shows the frequency response of VSG with and without virtual resistors.

[0032] Figure 8 The figure shows the active power transient response of the traditional virtual resistor and the adaptive virtual resistor in VSG.

[0033] Figure 9 The figure shows the frequency transient response of the traditional virtual resistor and the adaptive virtual resistor in VSG.

[0034] Figure 10 The figure shows the transient response of the power angle of the traditional virtual resistor and the adaptive virtual resistor in VSG. Detailed Implementation

[0035] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0036] Example 1: This invention provides an adaptive virtual resistance control method based on power feedback switching. By introducing a virtual power and grid connection point power feedback switching mechanism into the virtual synchronous generator control loop, the virtual resistance during faults is made equivalent to the grid resistance, thereby achieving simultaneous improvement in small-signal damping and transient stability. Furthermore, a virtual resistance that adaptively varies according to the severity of the fault is designed to enhance stability under various operating conditions. Figure 1 As shown, an adaptive virtual resistance control method based on power feedback switching includes the following steps: S1. Monitor the power grid status in real time and determine the operating status of the virtual synchronous generator's control system; the operating status includes normal operation mode and fault operation mode; S2. Based on the operating status of the virtual synchronous generator's control system, switch between the actual active power or virtual active power at the virtual synchronous generator's grid connection point as the feedback quantity of the active power control loop of the virtual synchronous generator's control system, so that the mathematical effect of the virtual resistance in the transient process is equivalent to the effect of the real power grid line resistance, thus completing adaptive virtual resistance control; in normal operating mode, the actual active power is used as the feedback quantity of the active power control loop. In fault operation mode, virtual active power is used as the feedback quantity of active power control loop. The virtual resistance parameter is adjusted by calculating the adaptive virtual resistance increment according to the fault degree, so that the influence of virtual resistance on transient characteristics is equivalent to grid resistance. This achieves simultaneous improvement of small signal damping enhancement and transient stability, thus completing adaptive virtual resistance control.

[0037] In this embodiment, real-time monitoring of the power grid status and determination of the operating status of the virtual synchronous generator control system specifically includes the following steps: Collect the instantaneous three-phase voltage values ​​at the PCC point; Transforming the instantaneous values ​​of the three-phase voltages to the dq coordinate system yields the d-axis voltage components. V d and q-axis voltage component V q ; Based on the d-axis voltage component V d and q-axis voltage component V q The effective amplitude of the PCC voltage is calculated. V PCC |:

[0038] in, V d Represents the d-axis voltage component. V q Represents the q-axis voltage component; The effective amplitude of the PCC voltage | V PCC |With preset fault trigger threshold V fault With fault recovery threshold V rec By comparing the results, it can be determined whether the control system of the virtual synchronous generator has malfunctioned.

[0039] In this embodiment, as Figure 2 The diagram shows the overall structure of the control method for enhancing the small-signal and transient stability of a VSG proposed in this invention. The upper part represents the main circuit topology of the VSG, and the lower part is its control structure block diagram. The system employs a per-unit modeling and analysis method, where all electrical variables and control parameters are expressed in per-unit values.

[0040] In the main circuit section, the VSG outputs voltage via an LC filter and is connected to the mains side through the line impedance. The filter inductor and filter capacitor are denoted as follows: L f and C f The circuit section consists of inductors. L g With resistance R g Its structure, its impedance is denoted as Z g The inverter DC side voltage is V dc The voltage across the filter capacitor is denoted as V PCC The grid voltage is denoted as V g The corresponding current variables are: current on the filter inductor side. I L Grid-connected side current I g .

[0041] The VSG generates a reference phase from an external active and reactive power control loop. θ ref and reference voltage V ref The external power control loop is represented as follows:

[0042]

[0043]

[0044] in, J and D For VSG virtual inertia and damping parameters, k q This is the droop coefficient of the reactive power control loop. P 0 and Q 0 is a reference value for active and reactive power. P VSG exist k =0 (normal operating mode) is P e , k =1 (fault mode) P vir .in, P e This represents the actual active power at the PCC point. P vir This represents the active power at the virtual PCC point. P e and P vir It can be calculated using the following formula:

[0045]

[0046] in, V d and V q These are the d-axis and q-axis components of the voltage detected at the PCC point. V refd and V refq It is the reference voltage generated by the reactive voltage loop. V ref The d-axis and q-axis components, I gd and I gq It is the current flowing into the power grid. I g The d-axis and q-axis components. Through the active power loop switching control structure, when a fault is detected, the actual power feedback... P e Switch to virtual power P vir feedback.

[0047] Figure 3 The display shows the virtual PCC point, the actual PCC point, and the power of the virtual PCC point. P virActual PCC point power P e The relationship between them. Add a virtual resistor. R v Then, the reference voltage becomes V new = V ref - I g R v PCC point voltage tracks new reference voltage V new Virtual resistance R v It does not consume actual power. R v The power output is effectively changed by influencing the inner loop control output of the VSG voltage.

[0048] In this embodiment, the virtual resistance is... R v With grid-side resistance R g The impact of VSG on stability is analyzed. Assuming the VSG is connected to a high-voltage power grid, the line inductance is much greater than the line resistance, and the actual power at the PCC point is... P e Mainly composed of VSG power angle θ VSG Decide, Q e Mainly composed of voltage V PCC Decision. The actual PCC point power can be derived. P e about θ VSG transfer function and Q e about V PCC transfer function for:

[0049]

[0050] in, Represents the complex frequency domain variables in the Laplace transform; By transfer function G Pθ , G EQ A pair of conjugate poles can be obtained. p 1, p 2 are respectively:

[0051]

[0052] in, To represent a complex unit, Indicates the power grid reference frequency; Therefore, when R g Very small L g When the value is large, the pole is close to the imaginary axis, making it easier to trigger the synchronization frequency. ω Oscillations near 0. Add a virtual resistor. R v This can effectively increase the line resistance and move the poles away from the virtual axis, which is beneficial for suppressing synchronous oscillations.

[0053] Set the VSG's power angle relative to the power grid as follows: θ Gg = θ VSG - θ grid .according to Figure 3 Equivalent circuit, derivation P e With relative work angle θ Gg The relationship is:

[0054] according to P e With relative work angle θ Gg Draw the different relationships. R v , R g Down P e and θ Gg Relationship curve, such as Figure 4 As shown. R v and R g right P e The effects are different. R g Get bigger P e The increase in the maximum value and the increase in the distance between the balance point and the unbalanced point mean that the active power transmission capacity of the PCC point increases and the deceleration area increases during VSG faults. R v Get bigger P eThe smaller the maximum value, the smaller the distance between the equilibrium and unbalanced points, means a decrease in the active power transmission capacity of the PCC point and a reduction in the deceleration area during VSG faults. Therefore, R v This increases the risk of VSG transient stability. R g This is beneficial to the transient stability of VSG.

[0055] In summary, joining R v This is beneficial for suppressing synchronous oscillations but detrimental to transient stability. This invention switches the actual PCC power feedback during transient faults. P e Virtual PCC power feedback point P vir , making virtual resistance R v The effect on transient characteristics is equivalent to the grid resistance. R g This improves transient synchronization stability while retaining the damping of small-signal oscillations.

[0056] In this embodiment, a fault detection module is provided, which is integrated into the control system of the VSG. It is used to monitor the power grid status in real time and generate a switching signal according to preset logic to control the VSG to switch between normal operation mode and fault operation mode.

[0057] like Figure 5 As shown, the fault detection module includes: a signal acquisition unit, a feature calculation unit, a logic judgment unit, and a signal output unit. The signal acquisition unit acquires the instantaneous values ​​of the three-phase voltage at the PCC point, and the feature calculation unit transforms the instantaneous values ​​of the three-phase PCC voltage to the dq coordinate system to obtain the voltage components. V d and V q The effective amplitude of the PCC voltage is calculated based on the dq components. V PCC |. Among them | V PCC The calculation formula is:

[0058] The logic judgment unit will determine the real-time voltage amplitude. V PCC |With preset fault trigger threshold V fault With fault recovery threshold V rec Compare. When | V PCC |< Vfault When the comparator outputs a suspected fault signal, it is then processed by a delay timer. If the suspected fault signal lasts longer than the delay, a fault is confirmed; if | V PCC |> V rec When the fault is cleared, the comparator outputs a fault clear signal, which is then processed by a delay timer. If the fault clear signal lasts longer than the delay, the fault is confirmed to be cleared.

[0059] The signal output unit outputs the mode switching signal generated by the logic judgment unit. k It is directly connected to the corresponding input terminal of the VSG active power control loop for switching between normal operation and fault periods.

[0060] In this embodiment, a virtual resistance adaptive adjustment method is provided, which enables the virtual resistance parameter to be adaptively adjusted based on the PCC point voltage and VSG frequency, ensuring small signal stability while achieving adaptive enhancement of the transient stability of VSG under different operating conditions.

[0061] First, set a constant base virtual resistance value. R v,base The selection of this value is mainly based on the small-signal stability analysis of the system, ensuring that it is sufficient to suppress synchronous resonance under normal operating conditions. Then, the current voltage amplitude is calculated. V PCC |with rated voltage amplitude V rated The deviation is used to quantify the severity of the fault. A voltage deviation factor is defined. V falut = V rated -| V PCC | Quantify the severity of the fault. Based on the assessed fault severity, an adaptive virtual resistance increment is calculated in real time, which is proportional to the voltage deviation factor. The base virtual resistance is added to the adaptive virtual resistance increment to obtain the total virtual resistance value under different fault conditions:

[0062] in, This represents the total virtual resistance value. This represents the virtual resistance gain coefficient.

[0063] Example 2: Based on Example 1, this embodiment of the invention builds a simulation platform based on MATLAB / Simulink. Figure 2A VSG system model with consistent structure is shown to verify the effectiveness of the proposed adaptive virtual resistance control method based on power feedback switching in suppressing VSG synchronous resonance and improving transient stability. The simulation system is run in a 20kW / 380V three-phase power grid environment. The VSG is connected to the infinite power grid through an LC filter and line impedance. The key circuits and control parameters used in the simulation are shown in Table 1, and these parameters refer to typical configurations in the prior art.

[0064] Table 1 Simulation Parameters

[0065] 1. Small signal stability verification To verify the effectiveness of the method of this invention in suppressing synchronous resonance caused by an increase in the X / R ratio of the grid parameters and ensuring the small-signal stability of the system under normal operating conditions, the basic virtual resistance Rv,base of the method of this invention was set to 0.05 pu under the conditions of SCR=10 and X / R ratio of 10:1, and the active power command was increased by 0.1 pu at 2s of simulation time. The active power response and frequency response were observed and compared with the case without virtual resistance. The simulation results are as follows. Figure 6 and Figure 7 As shown. By Figure 6 and Figure 7 As can be seen, without the virtual resistor, the system damping is severely insufficient, and the VSG output active power and frequency waveform exhibit obvious and continuous oscillations close to 50Hz, which is a typical synchronous resonance phenomenon. Under the same disturbance, with the addition of the virtual resistor Rv,base, the power and frequency waveforms show a brief dynamic process at the moment of disturbance, but quickly reach a steady state afterward, without power or frequency oscillations, and the synchronous resonance phenomenon is effectively suppressed. The simulation results of this scenario demonstrate that by setting a reasonable base virtual resistor Rv,base, this invention fully retains the core function of virtual resistor in suppressing synchronous resonance, ensuring the stable operation of the VSG under normal and small disturbance conditions.

[0066] 2. Verification of the Enhanced Transient Synchronization Stability To further verify the transient stability capability of the method of the present invention compared with the traditional virtual resistance method, an equivalent large power grid voltage was set at a simulation time t=2s. V g The voltage dropped to 0.2 pu of the rated value. The fault was cleared after 1 second, and the mains voltage returned to normal. V g Returned to normal. Figure 8 , Figure 9 and Figure 10It can be seen that during the fault, the VSG using traditional virtual resistance control cannot overcome the fault, the output active power fails to stabilize, the frequency gradually accelerates, and the power angle loses synchronization. The VSG using adaptive virtual resistance control can overcome the fault, the output active power can stabilize, the frequency stabilizes at the rated value, and the power angle does not become unstable.

[0067] Based on the simulation results of the two scenarios above, the following conclusions can be drawn: The adaptive virtual resistance control method for enhancing the small-signal and transient stability of VSG proposed in this invention successfully resolves the contradictory impact of traditional virtual resistance control on small-signal stability and transient stability. Simulations demonstrate that this method can enhance the transient synchronization stability of VSG under severe grid faults without sacrificing small-signal stability, and its performance is significantly better than that of traditional virtual resistance control schemes.

[0068] Example 3: Based on Embodiment 1, this embodiment of the invention provides an adaptive virtual resistance control system based on power feedback switching, which can be used to implement the adaptive virtual resistance control method based on power feedback switching as described in the foregoing embodiments. The system includes: The fault detection module is used to monitor the power grid status in real time and determine the operating status of the virtual synchronous generator's control system. The control switching module is used to switch the actual active power or virtual active power at the grid connection point of the virtual synchronous generator as the feedback quantity of the active power control loop of the virtual synchronous generator control system according to the operating status of the virtual synchronous generator control system. This makes the mathematical effect of the virtual resistance in the transient process equivalent to the effect of the real power grid line resistance, thus completing adaptive virtual resistance control.

[0069] The fault detection module includes: The signal acquisition unit is used to acquire the instantaneous values ​​of the three-phase voltage at the PCC point; The feature calculation unit is used to transform the instantaneous values ​​of the three-phase voltage to the dq coordinate system to obtain the d-axis voltage component and the q-axis voltage component, and calculate the effective amplitude of the PCC voltage based on the d-axis voltage component and the q-axis voltage component. The logic judgment unit is used to compare the effective amplitude of the PCC voltage with the preset fault start threshold and fault recovery threshold to determine whether the control system of the virtual synchronous generator has failed.

[0070] According to embodiments of the present invention, the present invention also provides an electronic device, a readable storage medium, and a computer program product.

[0071] In an exemplary embodiment, an electronic device includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the adaptive virtual resistance control method based on power feedback switching as described in Embodiment 1 above.

[0072] In an exemplary embodiment, the readable storage medium may be a non-transient computer-readable storage medium storing computer instructions for causing a computer to execute the adaptive virtual resistance control method based on power feedback switching as described in Embodiment 1 above.

[0073] In an exemplary embodiment, the computer program product includes a computer program that, when executed by a processor, implements the adaptive virtual resistance control method based on power feedback switching as described in Embodiment 1 above.

[0074] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0075] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0076] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor); and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0077] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with embodiments of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0078] Computer systems can include clients and servers. Clients and servers are generally located far apart and typically interact via communication networks. Client-server relationships are created by computer programs running on the respective computers and having a client-server relationship with each other. Servers can be cloud servers, servers in distributed systems, or servers incorporating blockchain technology.

[0079] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An adaptive virtual resistance control method based on power feedback switching, characterized in that, Includes the following steps: Real-time monitoring of the power grid status to determine the operating status of the virtual synchronous generator's control system; Based on the operating status of the virtual synchronous generator's control system, the actual active power or virtual active power at the virtual synchronous generator's grid connection point is switched as the feedback quantity of the active power control loop of the virtual synchronous generator's control system, so that the mathematical effect of the virtual resistance in the transient process is equivalent to the effect of the real power grid line resistance, thus completing adaptive virtual resistance control.

2. The adaptive virtual resistance control method based on power feedback switching according to claim 1, characterized in that, Operating status includes normal operating mode and fault operating mode; Real-time monitoring of the power grid status and determination of the operating status of the virtual synchronous generator control system specifically includes the following steps: Collect the instantaneous three-phase voltage values ​​at the PCC point; Transform the instantaneous values ​​of the three-phase voltages to the dq coordinate system to obtain the d-axis voltage components and q-axis voltage components, and calculate the effective amplitude of the PCC voltage based on the d-axis voltage components and q-axis voltage components. The effective amplitude of the PCC voltage is compared with the preset fault start threshold and fault recovery threshold to determine whether the control system of the virtual synchronous generator has failed.

3. The adaptive virtual resistance control method based on power feedback switching according to claim 2, characterized in that, Effective amplitude of PCC voltage | V PCC The formula for calculating | is: in, V d Represents the d-axis voltage component. V q This represents the q-axis voltage component.

4. The adaptive virtual resistance control method based on power feedback switching according to claim 2, characterized in that, Based on the operating status of the virtual synchronous generator's control system, the actual active power or virtual active power at the virtual synchronous generator's grid connection point is switched as the feedback quantity for the active power control loop of the virtual synchronous generator's control system. Specifically: In normal operating mode, the actual active power is used as the feedback quantity of the active power control loop; In fault operation mode, virtual active power is used as the feedback quantity of active power control loop. The virtual resistance parameter is adjusted by calculating the adaptive virtual resistance increment according to the fault degree, so that the influence of virtual resistance on transient characteristics is equivalent to grid resistance. This achieves simultaneous improvement of small signal damping enhancement and transient stability, thus completing adaptive virtual resistance control.

5. The adaptive virtual resistance control method based on power feedback switching according to claim 4, characterized in that, The virtual resistance parameters are adjusted by calculating the adaptive virtual resistance increment based on the fault severity. Set the basic virtual resistance value to ensure small-signal stability; The deviation between the rated voltage amplitude and the effective amplitude of the PCC voltage is calculated in real time to obtain the voltage deviation factor characterizing the severity of the fault. Multiplying the voltage deviation factor by the virtual resistance gain coefficient yields the adaptive virtual resistance increment; The total virtual resistance value under different fault conditions is obtained by adding the adaptive virtual resistance increment and the basic virtual resistance value, thus completing the adjustment of the virtual resistance parameter.

6. The adaptive virtual resistance control method based on power feedback switching according to claim 2, characterized in that, The effective amplitude of the PCC voltage is compared with the preset fault initiation threshold and fault recovery threshold to determine whether the control system of the virtual synchronous generator has failed. Specifically: If the effective amplitude of the PCC voltage is greater than or equal to the preset fault initiation threshold, then no fault has occurred. If the effective amplitude of the PCC voltage is less than the preset fault initiation threshold, a suspected fault signal is output. If the duration of the suspected fault signal exceeds the first preset delay, it is determined that the control system of the virtual synchronous generator has failed. If the effective amplitude of the PCC voltage is greater than the fault recovery threshold, a fault clearing signal is output. If the duration of the fault clearing signal exceeds the second preset delay, it is determined that the control system fault of the virtual synchronous generator has been cleared.

7. The adaptive virtual resistance control method based on power feedback switching according to claim 2, characterized in that, The formula for calculating actual active power is: in, Indicates actual active power. Represents the d-axis voltage component. Represents the q-axis voltage component. Indicates the current flowing into the power grid I g d-axis component, Indicates the current flowing into the power grid I g q-axis component; The formula for calculating virtual active power is: in, Indicates virtual active power. This represents the reference voltage generated by the reactive voltage loop. V ref d-axis component, This represents the reference voltage generated by the reactive voltage loop. V ref The q-axis component.

8. An adaptive virtual resistance control system based on power feedback switching, characterized in that, include: The fault detection module is used to monitor the power grid status in real time and determine the operating status of the virtual synchronous generator's control system. The control switching module is used to switch the actual active power or virtual active power at the grid connection point of the virtual synchronous generator as the feedback quantity of the active power control loop of the virtual synchronous generator control system according to the operating status of the virtual synchronous generator control system. This makes the mathematical effect of the virtual resistance in the transient process equivalent to the effect of the real power grid line resistance, thus completing adaptive virtual resistance control.

9. The adaptive virtual resistance control system based on power feedback switching according to claim 8, characterized in that, The fault detection module includes: The signal acquisition unit is used to acquire the instantaneous values ​​of the three-phase voltage at the PCC point; The feature calculation unit is used to transform the instantaneous values ​​of the three-phase voltage to the dq coordinate system to obtain the d-axis voltage component and the q-axis voltage component, and calculate the effective amplitude of the PCC voltage based on the d-axis voltage component and the q-axis voltage component. The logic judgment unit is used to compare the effective amplitude of the PCC voltage with the preset fault start threshold and fault recovery threshold to determine whether the control system of the virtual synchronous generator has failed.

10. A non-transitory computer-readable storage medium storing computer instructions, characterized in that, The computer instructions are used to cause the computer to perform the method according to any one of claims 1-7.

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