Method and system for analyzing oscillation transmission effect of network-constructed virtual synchronous machine system

Abstract

This invention provides a method for analyzing the oscillation transfer effect in a network-type virtual synchronous generator system, belonging to the field of virtual synchronous generator control. It establishes a small-signal model of the GFM-VSG system; based on this model, it establishes coupling transfer functions between various electrical quantities and an oscillation transfer model for the GFM-VSG system, where each electrical quantity includes active power, reactive power, frequency, and voltage; based on the amplitude-frequency characteristics of the oscillation transfer model, it evaluates whether the oscillation transfer effect between electrical quantities is an amplification or suppression effect; and based on the gain ratio of the oscillation transfer between electrical quantities, it determines the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions. The invention also provides a system capable of assessing the strength of the oscillation transfer effect between electrical quantities, identifying whether the oscillation effect exacerbates or suppresses system oscillation, and using the gain ratio of the oscillation transfer between electrical quantities as a basis for determining the trend of oscillation amplitude changes in different electrical quantities.

Description

Technical Field

[0001] This invention relates to the field of virtual synchronous generator control technology, and in particular to a method and system for analyzing the oscillation transmission effect of a grid-type virtual synchronous generator system. Background Technology

[0002] With the accelerated transformation of the global energy structure, the penetration rate of power electronic equipment in the generation, consumption, and transmission and distribution sectors continues to increase. The dynamic characteristics of new power systems exhibit low inertia, weak damping, and strong coupling, posing new challenges to the dynamic stability of the power grid under disturbance conditions. Grid-Forming Virtual Synchronous Generator (GFM-VSG) simulates the rotor inertia and damping characteristics of a synchronous machine at the control level, which can enhance the system's frequency support capability and disturbance rejection capability to a certain extent, thereby helping to improve the safe, stable, and reliable operation of the power system.

[0003] However, after GFM-VSG is connected to the power grid, under specific grid connection conditions and control parameter configurations, there is still a risk of subsynchronous oscillation instability. Furthermore, there is a risk of oscillations propagating and transmitting between different electrical quantities and between multiple devices and nodes, thus adversely affecting the stable operation of the system. Existing research on the stability of GFM-VSG systems mainly focuses on analysis from the perspectives of frequency stability, voltage stability, and power coupling mechanisms.

[0004] Regarding frequency stability, related research mainly focuses on impedance modeling, eigenvalue analysis, transient response modeling, and stability criteria. For example, some studies have proposed impedance modeling methods for multi-GFM-VSG grid-connected systems considering power coupling effects and analyzed the impact of parameter changes on frequency oscillation characteristics. Other studies have used eigenvalue analysis to evaluate the impact of voltage loops on grid adaptability and frequency support performance, and further analyzed damping characteristics using the eigenvalue method, providing the impact of grid connection conditions and control parameters on system damping and corresponding safety constraints. To address the problem of insufficient damping, existing methods propose control strategies based on virtual impedance frequency adaptation from the perspective of damping compensation and improved control applicability to improve frequency stability under different operating conditions. In addition, some studies have constructed transient frequency response models of virtual synchronous generators, analyzed the impact of different control parameters on frequency stability, and proposed corresponding dynamic frequency stability identification approaches using methods such as amplitude-phase motion equations.

[0005] Regarding voltage stability, existing research has proposed a second-order linear active disturbance rejection control (ADRC) method incorporating an error-robust integral tracking module to achieve stable output voltage control. Building upon this, further research has proposed adaptive adjustment strategies for virtual impedance and voltage compensation coefficients, enhancing voltage support capabilities by reducing virtual impedance, reactive voltage droop coefficients, or increasing voltage compensation coefficients. For transient voltage stability issues, research has also proposed data-driven methods for screening key influencing nodes, or by determining the voltage stability domain boundary to assess voltage support capabilities, providing new analytical perspectives for suppressing voltage fluctuations and improving voltage stability.

[0006] Regarding power coupling mechanisms, some studies have established wide-frequency-domain dynamic power coupling models for virtual synchronous generators, indicating that the coupling effect between active and reactive power may exacerbate synchronous resonance. However, the understanding of the resonance generation mechanism and its propagation path remains insufficient. Other studies have analyzed the active power loop control characteristics of GFM-VSG from the perspective of modeling and parameter design, but have not fully considered the oscillation transmission effect between power loops. Recent research shows that the coupling between active and reactive power control in GFM-VSG systems significantly affects synchronous stability and leads to changes in the maximum transferable active power and its corresponding power angle. However, the analysis of the coupling effect between voltage and active power remains relatively insufficient. Furthermore, some studies have indicated a strong coupling relationship between voltage control and active power control, but the impact mechanism of this coupling and its oscillation transmission law among multiple electrical quantities lacks a systematic explanation. In addition, existing research has discussed the oscillation transmission mechanism under frequency and voltage coupling conditions, but the analysis of the oscillation transmission mechanism under the interactive coupling effects between active, reactive, frequency, and voltage still needs improvement.

[0007] In summary, while existing technologies have studied the stability of GFM-VSG systems from the perspectives of frequency, voltage, and power coupling, such as the Chinese invention patent application CN121355938A, "Stability and Oscillation Transmission Analysis System and Method for Grid-Type Converter Systems," these studies primarily analyze the oscillation transmission relationship between active and reactive power. The transmission types are relatively singular, and there is no specific, quantifiable analysis or determination of the magnitude (strength) of the oscillation transmission effect. Existing methods still have shortcomings in areas such as "the transmission law of oscillations between different electrical quantities in the system, the influence of coupling effects on the oscillation transmission path and intensity, and the construction of oscillation transmission analysis models that can be used for engineering evaluation." Therefore, it is necessary to propose an oscillation transmission evaluation modeling and analysis method for GFM-VSG systems to reveal the oscillation transmission effect between various electrical quantities, providing a basis for stability assessment, parameter tuning, and operation control. Summary of the Invention

[0008] The technical problem to be solved by this invention is: how to solve the problem that the stability analysis of existing GFM-VSG systems is difficult to analyze the oscillation transmission effect between different electrical quantities.

[0009] This invention solves the above-mentioned technical problems through the following technical solution: a method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system, comprising:

[0010] A small-signal model of the GFM-VSG system is established. Based on the small-signal model, the coupling transfer function between various electrical quantities is established, and an oscillation transfer model of the GFM-VSG system is also established. These electrical quantities include active power. reactive power ,frequency ,Voltage Based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, the oscillation transfer effect between various electrical quantities is evaluated as either an amplification effect or a suppression effect. Based on the gain ratio of the oscillation transfer between various electrical quantities, the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions is determined.

[0011] This invention establishes an active power model based on a small-signal model of a GFM-VSG system. reactive power ,frequency ,Voltage The coupling transfer function between electrical quantities is analyzed, and an oscillation transfer model is established based on the amplitude-frequency characteristic analysis method. The strength of the oscillation transfer effect between electrical quantities is quantitatively evaluated by the frequency response analysis method to identify whether the oscillation effect is aggravated or suppressed. The oscillation transfer effect is quantified by the gain ratio calculation method, and the ratio is used as the basis for judging the trend of oscillation amplitude change of different electrical quantities. This allows for a systematic analysis of the oscillation propagation characteristics of the GFM-VSG system under different operating conditions, revealing the potential impact of the oscillation transfer effect on the instability of the subsynchronous oscillation (SSO) phenomenon, and providing a theoretical basis for the stability optimization of the system.

[0012] Preferably, the process of establishing a small-signal model for a GFM-VSG system includes: Kirchhoff's voltage law and Kirchhoff's current law are used to analyze and establish the AC side loop equations of the inverter; The inverter output voltage and current are transformed using the dq transformation method; A small-signal model of the GFM-VSG system is established based on the AC side output power of the GFM-VSG system.

[0013] Preferably, the AC side loop equation of the inverter is:

[0014] By performing coordinate transformation on the inverter output voltage and current using the dq transformation method, we obtain:

[0015] in, , The inverter output voltages are respectively of axis, Axial components, , The inverter output current is respectively of axis, Axial components, , These are the grid voltages. of axis, Axial components.

[0016] The preferred equation for the small-signal model of the GFM-VSG system is:

[0017] in, For active power small signal quantity, For reactive power small signal quantity, The inverter-side voltage is the d-axis steady-state component. This represents the q-axis steady-state component of the inverter-side voltage. The steady-state d-axis component of the inverter-side current. This represents the q-axis steady-state component of the inverter-side current. This refers to the small signal quantity of the d-axis component of the inverter-side voltage. Small signal quantity of the q-axis component of the inverter-side voltage.

[0018] Preferably, the coupling transfer function between electrical quantities is:

[0019] , , , The expression is:

[0020] in, The voltage amplitude output by the converter. This is the effective value of the rated voltage of the power grid. , , , For filter inductance and parasitic resistance, , For the equivalent resistance and inductance of the power grid, The phase angle difference between the converter and the power grid. The rated angular frequency, It is a complex number.

[0021] The preferred oscillation transfer model for the GFM-VSG system is: Active power Transmitted to frequency oscillatory transfer function ,frequency Transfer to active power oscillatory transfer function They are respectively:

[0022] Active power Transmitted to voltage oscillatory transfer function ,Voltage Transfer to active power oscillatory transfer function They are respectively:

[0023] reactive power Transmitted to frequency oscillatory transfer function ,frequency Transfer to reactive power oscillatory transfer function They are respectively:

[0024] reactive power Transmitted to voltage oscillatory transfer function ,Voltage Transfer to reactive power oscillatory transfer function They are respectively:

[0025] frequency Transmitted to voltage oscillatory transfer function ,Voltage Transmitted to frequency oscillatory transfer function They are respectively:

[0026] reactive power Transfer to active power oscillatory transfer function Active power Transfer to reactive power oscillatory transfer function They are respectively:

[0027] in, , , The rated angular frequency, The active loop inertia coefficient. This is the active power loop damping coefficient. The reactive loop inertia coefficient, This is the reactive power ring damping coefficient. It is a complex number.

[0028] By constructing an oscillation propagation model to reveal the mechanism of the oscillation propagation phenomenon discovered in this invention, it is found that the amplitude of subsynchronous oscillations does not necessarily exhibit a "synchronization effect" among various electrical quantities. This phenomenon is attributed to the oscillation propagation effect mechanism among electrical quantities. If the oscillation propagation effect is an amplified propagation effect, the dynamic response of the output electrical quantity will be amplified, thereby leading to intensified oscillations and increasing the risk of system instability. Conversely, a suppressed propagation effect helps to reduce the risk of system instability due to oscillation propagation.

[0029] Preferably, the method for evaluating whether the oscillation transfer effect between various electrical quantities is an amplification transfer effect or a suppression transfer effect, based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, is as follows: If electrical quantity Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is that the amplitude is greater than 0 at the oscillation frequency point, and the electrical quantity Transmitted to electrical quantities The oscillation transmission effect is an amplification transmission effect; otherwise, the electrical quantity... Transmitted to electrical quantities The oscillation transmission effect is a suppression transmission effect, electrical quantity Electrical quantities Active power reactive power ,frequency ,Voltage Any electrical quantity in, and electrical quantity Electrical quantities For different electrical quantities.

[0030] The oscillation transfer model constructed in this invention can quantitatively evaluate the intensity of the oscillation transfer effect based on the amplitude of the oscillation transfer function at the oscillation frequency. A larger amplitude indicates a stronger oscillation transfer effect between different electrical quantities: when the amplitude is greater than 0, it indicates a higher risk of oscillation transfer between different electrical quantities; when the amplitude is less than 0, it indicates a lower risk of oscillation transfer between different electrical quantities. This criterion provides a new perspective for quantitatively evaluating the interactive influence between electrical quantities, exhibiting good adaptability and versatility, and can provide a theoretical basis for the parameter design of virtual synchronous machine controllers.

[0031] Preferably, the expression for the gain ratio of oscillation transmission between various electrical quantities is:

[0032] in, Electrical quantity Electrical quantities The gain ratio of the oscillations between them. Electrical quantity Transmitted to electrical quantities The oscillatory transfer function, Electrical quantity Transmitted to electrical quantities The oscillatory transfer function, It is a complex number. This is the dominant oscillation frequency point of the system.

[0033] Preferably, the method for determining the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions based on the gain ratio of oscillation transmission between various electrical quantities is as follows: like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude; like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude , Operating conditions Operating conditions China Electric Power Electrical quantities The gain ratio of the oscillation transmission between them.

[0034] By calculating the gain ratio of the oscillation transmission model, the magnitude of the electrical quantity oscillation amplitude under different operating conditions can be determined.

[0035] This invention also provides a system for analyzing the oscillation transfer effect of a network-type virtual synchronous machine system, comprising: The small-signal modeling module is used to build a small-signal model of the GFM-VSG system. The oscillation transfer modeling module is used to establish the coupling transfer function between various electrical quantities in the small-signal model of the GFM-VSG system, and to establish the oscillation transfer model of the GFM-VSG system. These electrical quantities include active power. reactive power ,frequency ,Voltage ; The oscillation transfer analysis module is used to evaluate whether the oscillation transfer effect between various electrical quantities is an amplification or suppression effect based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, and to determine the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions based on the gain ratio of the oscillation transfer between various electrical quantities. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0037] Figure 1 This is a schematic diagram of the topology and control strategy of the GFM-VSG system in the prior art; Figure 2 This is a schematic diagram of the open-loop model of the GFM-VSG system in the oscillation transfer effect analysis method of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the oscillation transfer model of the GFM-VSG system in the oscillation transfer effect analysis method of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 4 This is a flowchart of the oscillation transfer effect of the GFM-VSG system in the oscillation transfer effect analysis method of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the active power-frequency oscillation transfer effect analysis using the oscillation transfer effect analysis method for the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 6This is a schematic diagram of the reactive-voltage oscillation transmission effect analysis using the oscillation transmission effect analysis method for the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the active-voltage oscillation transfer effect analysis using the oscillation transfer effect analysis method for the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 8 This is a schematic diagram illustrating the frequency-voltage oscillation transfer effect analysis using the oscillation transfer effect analysis method for the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 9 This is a schematic diagram of the reactive-frequency oscillation transfer effect analysis using the oscillation transfer effect analysis method for the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 10 This is a schematic diagram of the active-reactive oscillation transmission effect analysis using the oscillation transmission effect analysis method for the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention; Figure 11(a) shows the analysis of oscillation transfer effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 5 Experimental results of active power-frequency oscillation transfer effect analysis under medium working condition 1; Figure 11(b) shows the analysis of oscillation transfer effect in a network-type virtual synchronous machine system using the method provided in Embodiment 1 of the present invention. Figure 5 Experimental results of active power-frequency oscillation transfer effect analysis under medium working condition 2; Figure 12(a) shows the analysis of oscillation transmission effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 6 Experimental results of reactive power-voltage oscillation transfer effect analysis under medium operating condition 3; Figure 12(b) shows the analysis of oscillation transfer effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 6 Experimental results of reactive power-voltage oscillation transfer effect analysis under medium operating condition 4; Figure 13(a) shows the analysis of oscillation transmission effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 7 Experimental results of active power-voltage oscillation transfer effect analysis under medium operating condition 3; Figure 13(b) shows the analysis of oscillation transfer effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 7 Experimental results of active-voltage oscillation transfer effect analysis under medium operating condition 4; Figure 14(a) shows the analysis of oscillation transmission effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 8 Experimental results of frequency-voltage oscillation transfer effect analysis under medium operating condition 3; Figure 14(b) shows the analysis of oscillation transfer effect in a network-type virtual synchronous machine system using the method provided in Embodiment 1 of the present invention. Figure 8 Experimental results of frequency-voltage oscillation transfer effect analysis under medium operating condition 4; Figure 15(a) shows the analysis of oscillation transfer effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 9 Experimental results of reactive-frequency oscillation transfer effect analysis under medium working condition 5; Figure 15(b) shows the analysis of oscillation transfer effect in a network-type virtual synchronous machine system using the method provided in Embodiment 1 of the present invention. Figure 9 Experimental results of reactive-frequency oscillation transfer effect analysis under medium working condition 6; Figure 16(a) shows the analysis of oscillation transfer effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 10 Experimental results of active-reactive oscillation transmission effect analysis under medium working condition 5; Figure 16(b) shows the analysis of oscillation transfer effect of the network-type virtual synchronous machine system provided in Embodiment 1 of the present invention. Figure 10 Experimental results of active-reactive oscillation transmission effect analysis under medium working condition 6.

[0038] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] Figure 1 This is a schematic diagram illustrating the topology and control strategy of a network-type virtual synchronous machine (GFM-VSG) system. , For filter inductance and parasitic resistance, , The equivalent resistance and inductance of the power grid are represented by DC and AC. DC / AC represents DC-AC conversion. , , , , , It consists of six IGBT transistors. , , They are respectively Mutually, Mutually, Phase filter resistor, , , They are respectively Mutually, Mutually, Phase filter inductor, Ground Indicates grounding. , , They are respectively Mutually, Mutually, Phase grid resistance, , , They are respectively Mutually, Mutually, Phase grid inductance, , , These are the three-phase voltage components output by the inverter. , , These are the three-phase current components output by the inverter. , , These are the three-phase voltages of the power grid. For filtering capacitors, The inverter outputs three-phase current. This provides the three-phase output voltage for the inverter. For inverter output dq Under-shaft current, For inverter output dq Under-shaft voltage. The grid voltage is represented by PCC, which is the grid connection point. , , These are the three-phase components of the three-phase modulated wave. P Active power Q Reactive power This is a reference value for active power. This is the reactive power reference value; SPWM stands for sinusoidal pulse width modulation. The angular frequency of the power grid. It is a complex number. This refers to the output voltage amplitude of the GFM-VSG, in volts (V). The active loop inertia coefficient, in units of , This is the active power loop damping coefficient, in units of... , The reactive loop inertia coefficient, in units of , This is the reactive power loop damping coefficient, in units of... Since LC filters can filter out high-frequency electrical quantities and exhibit low conduction characteristics at low frequencies, the effect of capacitance can be ignored in the subsynchronous oscillation analysis of GFM-VSG systems. For grid-connected current, This is the rated voltage of the power grid. Control section ( Figure 1 The VSG control section includes an active power loop and a reactive power loop. The active power loop outputs the GFM-VSG power angle. The amplitude of the reactive power loop output GFM-VSG voltage . The rated angular frequency, and Reference values ​​are given for the active power and reactive power of the converter, respectively. The voltage amplitude output by the converter. This represents the phase angle difference between the converter and the power grid. The active power output by the inverter. This refers to the reactive power output of the inverter.

[0041] The GFM-VSG system provides inertial damping support for the power grid by simulating the operating mechanism and dynamic characteristics of a traditional synchronous generator. However, the GFM-VSG system suffers from subsynchronous oscillation instability risk and oscillation propagation. To address this issue, this invention aims to construct an oscillation propagation effect model and evaluation method to reveal the oscillation propagation mechanism and deeply analyze the root causes of subsynchronous oscillation instability. Research reveals that the subsynchronous oscillation phenomenon in the GFM-VSG system is not entirely due to insufficient system stability margin, but also attributed to the oscillation propagation effect between different electrical quantities. Based on the proposed oscillation propagation effect evaluation framework and analysis method, the oscillation propagation effect of the GFM-VSG system can be quantitatively evaluated. The proposed modeling method and evaluation framework provide a theoretical basis for grid-connected stability and active support of grid-connected virtual synchronous generator systems. Finally, experiments verify the effectiveness and feasibility of the proposed modeling method and evaluation framework. The specific scheme is described below: Example 1 This embodiment provides a method for analyzing the oscillation transmission effect in a network-type virtual synchronous machine system, including the following steps: Step 1: Establish the small-signal model of the GFM-VSG system, which includes the following steps: Step 1.1: Analyze and establish the AC side loop equations of the inverter using Kirchhoff's Voltage Law (KVL) and Current Law (KCL): (1) In formula (1), The inverter output three-phase voltage, in volts (V). This refers to the three-phase AC current on the inverter side, expressed in amperes (A). This is the rated three-phase AC voltage of the power grid, expressed in volts (V).

[0042] Step 1.2: Perform coordinate transformation on the inverter output voltage and current using the dq transformation method, that is, perform dq transformation on formula (1) to obtain formula (2): (2) In formula (2), , These are the inverter output voltages. axis, Axial components, in units of V. , These are the inverter output currents. axis, Axial components, in units of A. , These are the mains voltages. axis, Axial component, unit: V.

[0043] Step 1.3: Based on the AC side output power of the GFM-VSG system, establish a small-signal model of the GFM-VSG system.

[0044] The expression for the AC side output power of the GFM-VSG system is: (3) In formula (3), The active power output by the inverter. This refers to the reactive power output of the inverter.

[0045] Combining equations (1) to (3), we obtain the equation for the small-signal model of the GFM-VSG system as follows: (4) In formula (4), the subscript 0 represents the steady-state value. For active power small signal quantity, For reactive power small signal quantity, The inverter-side voltage is the d-axis steady-state component. This represents the q-axis steady-state component of the inverter-side voltage. The steady-state d-axis component of the inverter-side current. This represents the q-axis steady-state component of the inverter-side current. This refers to the small signal quantity of the d-axis component of the inverter-side voltage. Small signal quantity of the q-axis component of the inverter-side voltage.

[0046] Step 2: Based on the small-signal model of the GFM-VSG system, establish the coupling transfer function between various electrical quantities, and establish the oscillation transfer model of the GFM-VSG system. Each electrical quantity includes active power. reactive power ,frequency ,Voltage By establishing the coupling transfer function between various electrical quantities, active power is quantitatively analyzed. reactive power ,frequency ,Voltage Based on the established small-signal model, an oscillation propagation analysis framework for the coupling effect of multiple electrical quantities is formed to evaluate the stability margin and oscillation characteristics of the GFM-VSG system under different operating conditions.

[0047] The motion equations of the virtual synchronous machine rotor can be described as follows: (5) In formula (5), This refers to the output angular frequency of the GFM-VSG, expressed in rad / s. This refers to the angular frequency of the power grid, measured in rad / s. The rated angular frequency, This refers to the output voltage amplitude of the GFM-VSG, in volts (V). The active loop inertia coefficient, in units of , This is the active power loop damping coefficient, in units of... , The reactive loop inertia coefficient, in units of , This is the reactive power loop damping coefficient, in units of... .

[0048] The active power can be obtained from formulas (4) and (5). reactive power ,frequency ,Voltage The coupling transfer function between them is: (6) In formula (6), , , , The expression is:

[0049] in, The voltage amplitude output by the converter. This is the effective value of the rated voltage of the power grid. , , , For filter inductance and parasitic resistance, , For the equivalent resistance and inductance of the power grid, The phase angle difference between the converter and the power grid. The rated angular frequency, It is a complex number.

[0050] According to formulas (5) and (6), the open-loop power model of the GFM-VSG system can be obtained as follows: Figure 2 As shown, the open-loop power model of the GFM-VSG system includes a feedforward control channel and a feedback control channel, used to achieve coordinated regulation of system frequency and power, as well as stable operation control. The feedforward control channel includes a frequency-phase angle generation unit and a power coupling regulation unit. The frequency-phase angle generation unit consists of a virtual inertia element and two stages of cascaded single-integral elements, used to simulate the inertial response characteristics and primary frequency regulation behavior of a synchronous generator, enabling the system to have a fast and smooth dynamic response capability when encountering frequency disturbances. The virtual inertia element is used to calculate the rate of change of the system's output angular frequency. This rate of change characterizes the dynamic evolution of frequency over time and is an important indicator of the system's equivalent inertial response level. The frequency offset is obtained by integration through the first-stage single-integral stage. This is used to reflect the magnitude of the deviation between the actual system frequency and the reference frequency (preferably the grid angular frequency). Subsequently, With grid angular frequency The system output angular frequency is obtained by superposition. Finally, angular frequency The virtual synchronous generator output phase angle is generated by integration through the second-stage single-integral stage. .

[0051] Output phase angle The phase change of the VSG relative to the power grid during dynamic processes is a key state variable for measuring synchronization capability and stability characteristics.

[0052] The power coupling regulation unit establishes a comprehensive transmission relationship between phase angle and active power, phase angle and reactive power, voltage and active power, and voltage and reactive power, so as to achieve coordinated regulation and reasonable allocation of active and reactive power, thereby improving the overall performance and adaptability of power control.

[0053] The feedback control channel enhances the damping effect and improves the VSG output frequency stability by introducing unity negative feedback to the active power. Similarly, unity negative feedback is introduced to the reactive power to enhance the damping effect and improve the dynamic characteristics of the system, thereby improving the VSG output voltage stability and further enhancing the overall stability and disturbance rejection capability.

[0054] The GFM-VSG system power open-loop model aims to determine the stability margin of the system control loop under the influence of coupling between various electrical quantities. According to... Figure 2 The coupling relationships of the various electrical quantities shown are such that the open-loop relationships of active power and frequency essentially belong to the same loop, therefore their open-loop models are identical; the same applies to the reactive power loop and voltage loop. Therefore, separate open-loop models can be established. and The open-loop model is as follows: (7) In formula (7), Let be the open-loop transfer function of active power. Let be the open-loop transfer function for reactive power. The active power stabilization loop transfer function is... Let the transfer function be the frequency stabilization loop. The transfer function of the reactive power stabilization loop. This is the transfer function of the voltage stabilization loop.

[0055]

[0056]

[0057] By constructing an oscillation transmission model, the mechanism of the oscillation transmission phenomenon discovered in this invention is revealed: the amplitude of subsynchronous oscillations does not necessarily exhibit a "synchronization effect" among the various electrical quantities. This phenomenon is attributed to the oscillation transmission effect mechanism among the electrical quantities. If the oscillation transmission effect is an amplified transmission effect, the dynamic response of the output electrical quantity will be amplified, leading to intensified oscillations and increasing the risk of system instability. Conversely, a suppressed transmission effect helps reduce the risk of system instability due to oscillation transmission. The oscillation transmission effect among the various electrical quantities is as follows: Figure 3 As shown.

[0058] Active power With frequency The oscillation transmission model between them can be expressed as: (8) In formula (8), Indicates active power Transmitted to frequency The oscillatory transfer function, Represents frequency Transfer to active power The oscillatory transfer function.

[0059] Active power With voltage The oscillation transmission model between them can be expressed as: (9) In formula (9), Indicates active power Transmitted to voltage The oscillatory transfer function, Indicates voltage Transfer to active power The oscillatory transfer function.

[0060] reactive power With frequency The oscillation transmission model between them can be expressed as: (10) In formula (10), Represents reactive power Transmitted to frequency The oscillatory transfer function, Represents frequency Transfer to reactive power The oscillatory transfer function.

[0061] reactive power With voltage The oscillation transmission model between them can be expressed as: (11) In formula (11), Represents reactive power Transmitted to voltage The oscillatory transfer function, Indicates voltage Transfer to reactive power The oscillatory transfer function.

[0062] frequency With voltage The oscillation transmission model between them can be expressed as: (12) In formula (12), Represents frequency Transmitted to voltage The oscillatory transfer function, Indicates voltage Transmitted to frequency The oscillatory transfer function.

[0063] reactive power With active power The oscillation transmission model between them can be expressed as: (13) In formula (13), Represents reactive power Transfer to active power The oscillatory transfer function, Indicates active power Transfer to reactive power The oscillatory transfer function.

[0064] This invention addresses the problem that existing technical solutions have limited analytical dimensions and struggle to characterize the dynamic interaction characteristics between different electrical quantities in grid-connected converter systems. It constructs an analytical framework for the oscillation propagation of different electrical quantities in grid-connected converters. This framework, starting from the perspective of oscillation propagation of different electrical quantities, systematically reveals the formation mechanism of low-frequency oscillations in grid-connected converter systems and verifies that system instability may be caused not only by insufficient stability margins but also by the effects of oscillation propagation of different electrical quantities. The proposed analytical framework provides a new analytical approach for suppressing low-frequency oscillations in grid-connected converter systems and offers a scientific basis for optimizing system control strategies and tuning parameters.

[0065] Step 3: Based on the amplitude-frequency characteristics of the oscillation transmission model of the GFM-VSG system (the model of formula (8) to formula (13), evaluate whether the oscillation transmission effect between each electrical quantity is an amplification transmission effect or a suppression transmission effect, and based on the gain ratio of the oscillation transmission between each electrical quantity, determine the magnitude of the oscillation amplitude of the corresponding electrical quantity under different operating conditions.

[0066] See Figure 4 Based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, the method for evaluating whether the oscillation transfer effect between various electrical quantities is an amplification transfer effect or a suppression transfer effect is as follows: If electrical quantity Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is that the amplitude is greater than 0 at the oscillation frequency point, and the electrical quantity Transmitted to electrical quantities The oscillation transmission effect is an amplification transmission effect; otherwise (i.e., electrical quantity) Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is less than or equal to 0 at the oscillation frequency point (electrical quantity). Transmitted to electrical quantities The oscillatory transmission effect is a suppression transmission effect.

[0067] Similarly, if electrical quantities Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is that the amplitude is greater than 0 at the oscillation frequency point, and the electrical quantity Transmitted to electrical quantities The oscillation transmission effect is an amplification transmission effect; otherwise (i.e., electrical quantity) Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is less than or equal to 0 at the oscillation frequency point (electrical quantity). Transmitted to electrical quantities The oscillatory transmission effect is a suppression transmission effect.

[0068] electrical quantities Electrical quantities Active power reactive power ,frequency ,Voltage Any electrical quantity in, and electrical quantity Electrical quantities For different electrical quantities.

[0069] The expression for the gain ratio of oscillation transmission between various electrical quantities is as follows: (14) In formula (14), Electrical quantity Electrical quantities The gain ratio of the oscillation transmission between them.

[0070] Based on the gain ratio of oscillation transmission between various electrical quantities, the method for determining the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions is as follows: like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude.

[0071] like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude.

[0072] Traditional VSG stability analysis typically relies on the stability margin of the open-loop transfer function. However, this method struggles to analyze the oscillation propagation effect between different electrical quantities, thus failing to accurately assess the system's stability risk. Specifically, the oscillation propagation effect between different electrical quantities impacts the stability of GFM-VSG systems. To address this, this invention proposes an oscillation propagation effect analysis method for network-type virtual synchronous machine systems. This method aims to reveal the oscillation propagation mechanism and deeply analyze the root causes of subsynchronous oscillation instability, thereby overcoming the shortcomings of traditional open-loop stability analysis methods.

[0073] This invention linearizes the small-signal model of the GFM-VSG system to obtain the electrical quantity differential equations under VSG steady state; establishes an oscillation transfer model based on amplitude-frequency characteristic analysis, and quantitatively evaluates the strength of the oscillation transfer effect between various electrical quantities through frequency response analysis to identify whether the oscillation effect is aggravated or suppressed. The oscillation transmission effect is quantified using a gain ratio calculation method, and this ratio is used as the basis for determining the trend of oscillation amplitude changes in different electrical quantities. Based on the gain ratio of oscillation transmission between various electrical quantities, the magnitude of the corresponding electrical quantity oscillation amplitude under different operating conditions is determined. This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude; like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude , Operating conditions Operating conditions China Electric Power Electrical quantities The gain ratio of the oscillation transmission between them.

[0074] Based on this evaluation framework, the oscillation propagation characteristics of the GFM-VSG system under different operating conditions can be systematically analyzed, revealing the potential impact of oscillation transfer effects on the instability of subsynchronous oscillation (SSO) phenomena, and providing a theoretical basis for system stability optimization. By comparing the changes in the strength of oscillation transfer effects, the influence of the type of oscillation transfer (amplification or suppression effect) on system stability is analyzed in depth, and improved control strategies are proposed to enhance system stability.

[0075] Furthermore, the oscillation transfer model constructed in this invention can quantitatively evaluate the intensity of the oscillation transfer effect based on the amplitude of the oscillation transfer function at the oscillation frequency. A larger amplitude indicates a stronger oscillation transfer effect between different electrical quantities: when the amplitude is greater than 0, it indicates a higher risk of oscillation transfer between different electrical quantities; when the amplitude is less than 0, it indicates a lower risk of oscillation transfer between different electrical quantities. The above criteria have good adaptability and universality, and can provide a theoretical basis for the parameter design of virtual synchronous machine controllers.

[0076] This invention proposes a method for analyzing the oscillation transmission effect between different electrical quantities in a network-type virtual synchronous machine system, mainly reflected in the following aspects: (1) The subsynchronous oscillation phenomenon in the network-type virtual synchronous machine (GFM-VSG) system is not unique. It may be attributed to the insufficient stability margin of the system itself, or to the oscillation transmission effect caused by the coupling between various electrical quantities.

[0077] (2) Traditional stability analysis models and methods often fail to adequately consider the oscillation transmission effect between electrical quantities. Based on this, the established oscillation transmission framework reveals the coupling effect mechanism between electrical quantities, thereby suppressing subsynchronous oscillations of the system and enhancing the system's stability.

[0078] (3) The strength of the oscillation transmission effect caused by the coupling effect between various electrical quantities can be reflected by the amplitude of the amplitude-frequency characteristic at the oscillation frequency point of the oscillation transmission model. Under different operating conditions, the gain ratio of the oscillation transmission model can also be used to determine the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions.

[0079] This invention is also applicable to the determination of the oscillation transmission effect between different electrical quantities in a network-type VSG system under any other control technology.

[0080] Example 2 This embodiment provides a system for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system, including: The small-signal modeling module is used to establish a small-signal model of the GFM-VSG system; the specific process includes: The inverter's AC side loop equations are analyzed and established using Kirchhoff's voltage law and current law; the inverter's AC side loop equations are as follows:

[0081] The inverter output voltage and current are transformed using the dq transformation method to obtain:

[0082] in, , The inverter output voltages are respectively of axis, Axial components, , The inverter output current is respectively of axis, Axial components, , These are the grid voltages. of axis, Axial components.

[0083] Based on the AC-side output power of the GFM-VSG system, a small-signal model of the GFM-VSG system is established. The equations of the small-signal model of the GFM-VSG system are:

[0084] In this context, the subscript 0 indicates the steady-state value. For active power small signal quantity, For reactive power small signal quantity, The inverter-side voltage is the d-axis steady-state component. This represents the q-axis steady-state component of the inverter-side voltage. The steady-state d-axis component of the inverter-side current. This represents the q-axis steady-state component of the inverter-side current. This refers to the small signal quantity of the d-axis component of the inverter-side voltage. Small signal quantity of the q-axis component of the inverter-side voltage.

[0085] The oscillation transfer modeling module is used to establish the coupling transfer function between various electrical quantities in the small-signal model of the GFM-VSG system, and to establish the oscillation transfer model of the GFM-VSG system. These electrical quantities include active power. reactive power ,frequency ,Voltage The coupling transfer function between electrical quantities is:

[0086] , , , The expression is:

[0087] in, The voltage amplitude output by the converter. This is the effective value of the rated voltage of the power grid. , , , For filter inductance and parasitic resistance, , For the equivalent resistance and inductance of the power grid, The phase angle difference between the converter and the power grid. The rated angular frequency, It is a complex number.

[0088] The oscillation transfer analysis module is used to evaluate whether the oscillation transfer effect between various electrical quantities is an amplification or suppression effect based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, and to determine the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions based on the gain ratio of the oscillation transfer between various electrical quantities.

[0089] The oscillation transfer model of the GFM-VSG system includes: active power With frequency Oscillation transmission model and active power between them With voltage Oscillation transmission model and reactive power With frequency Oscillation transmission model and reactive power With voltage The oscillation transmission model and frequency between them With voltage Oscillation transmission model and reactive power With active power The oscillation transmission model between them.

[0090] Among them, active power Transmitted to frequency oscillatory transfer function ,frequency Transfer to active power oscillatory transfer function They are respectively:

[0091] Active power Transmitted to voltage oscillatory transfer function ,Voltage Transfer to active power oscillatory transfer function They are respectively:

[0092] reactive power Transmitted to frequency oscillatory transfer function ,frequency Transfer to reactive power oscillatory transfer function They are respectively:

[0093] reactive power Transmitted to voltage oscillatory transfer function ,Voltage Transfer to reactive power oscillatory transfer function They are respectively:

[0094] frequency Transmitted to voltage oscillatory transfer function ,Voltage Transmitted to frequency oscillatory transfer function They are respectively:

[0095] reactive power Transfer to active power oscillatory transfer function Active power Transfer to reactive power oscillatory transfer function They are respectively:

[0096] in, , , The rated angular frequency, The active loop inertia coefficient. This is the active power loop damping coefficient. The reactive loop inertia coefficient, This is the reactive power ring damping coefficient. It is a complex number.

[0097] Based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, the method for evaluating whether the oscillation transfer effect between various electrical quantities is an amplification or suppression of the transfer effect is as follows: If electrical quantity Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is that the amplitude is greater than 0 at the oscillation frequency point, and the electrical quantity Transmitted to electrical quantities The oscillation transmission effect is an amplification transmission effect; otherwise, the electrical quantity... Transmitted to electrical quantities The oscillation transmission effect is a suppression transmission effect, electrical quantity Electrical quantities Active power reactive power ,frequency ,Voltage Any electrical quantity in, and electrical quantity Electrical quantities For different electrical quantities.

[0098] The expression for the gain ratio of oscillation transmission between various electrical quantities is:

[0099] in, Electrical quantity Electrical quantities The gain ratio of the oscillations between them. Electrical quantity Transmitted to electrical quantities The oscillatory transfer function, Electrical quantity Transmitted to electrical quantities The oscillatory transfer function, It is a complex number.

[0100] Based on the gain ratio of oscillation transmission between various electrical quantities, the method for determining the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions is as follows: like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude; like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude , Operating conditions Operating conditions China Electric Power Electrical quantities The gain ratio of the oscillation transmission between them.

[0101] Experimental Analysis To verify the effectiveness of the proposed framework and analysis method, this invention conducts an analysis of the oscillation transfer effect mechanism of the GFM-VSG system, setting up six operating conditions for analysis. Operating conditions 1 and 2 are used to analyze the oscillation transfer effect between active power and frequency; operating conditions 3 and 4 are used to analyze the oscillation transfer effects between reactive power and voltage, active power and voltage, and frequency and voltage; operating conditions 5 and 6 are used to analyze the oscillation transfer effect between reactive power and frequency, and active power and reactive power. Some system parameters are the same in the above operating conditions, as shown in Table 1.

[0102] Table 1 Control and Circuit Parameter Table

[0103] like Figure 5 As shown, in operating conditions 1 and 2, f to P The transfer function has an amplitude greater than 0 at the oscillation frequency, indicating an amplified oscillation transfer effect. Furthermore, in operating condition 2... f to P The amplitude is greater than that in operating condition 1 f to P The amplitude indicates that under operating condition 2 f to P The oscillation transmission effect is stronger in condition 2, and the active power oscillation amplitude is more pronounced in condition 2. Similarly, in conditions 1 and 2... P to f The transfer function amplitude at the oscillation frequency is less than 0, indicating a suppressed oscillation transfer effect. Therefore, the oscillation amplitude of active power is more pronounced than that of frequency. Compared to operating condition 1, operating condition 2... P to f The amplitude is smaller, and therefore, the frequency oscillation amplitude is smaller in operating condition 2. For example... Figure 5 In the middle, working condition 2 f to P and P tof The gain ratio of the transfer function at the oscillation frequency ( When the value is greater than that of operating condition 1, the oscillation transmission effect between P and f exacerbates the oscillation between the frequency of operating condition 1 and the active power of operating condition 2, while suppressing the oscillation between the active power of operating condition 1 and the frequency of operating condition 2.

[0104] like Figure 6 As shown, in operating conditions 3 and 4, the transfer function from Q to E exhibits a suppressed oscillation transfer effect at the oscillation frequency point with an amplitude less than 0, while the transfer function from E to Q exhibits an amplified oscillation transfer effect at the oscillation frequency point with an amplitude greater than 0. In this case, the reactive power oscillation amplitude is more pronounced compared to the voltage oscillation. Compared to operating condition 3, the amplitude of Q to E is smaller in operating condition 4, while the amplitude of E to Q is larger. Therefore, in operating condition 4, the voltage oscillation amplitude is smaller, while the reactive power oscillation amplitude is larger. Figure 6 In condition 4, the gain ratio of the transfer function at the oscillation frequency point between E and Q is ( ). When the value is greater than that of operating condition 3, the oscillation transmission effect between Q and E exacerbates the oscillation between reactive power in operating condition 4 and voltage in operating condition 3, while suppressing the oscillation between reactive power in operating condition 3 and voltage in operating condition 4.

[0105] like Figure 7 As shown, in operating conditions 3 and 4, the transfer function from P to E exhibits a suppressed oscillation transfer effect at the oscillation frequency point with an amplitude less than 0, while the transfer function from E to P exhibits an amplified oscillation transfer effect at the oscillation frequency point with an amplitude greater than 0. In this case, the oscillation amplitude of active power is more pronounced compared to voltage. Compared to operating condition 3, the amplitude of P to E is smaller in operating condition 4, while the amplitude of E to P is larger. Therefore, in operating condition 4, the voltage oscillation amplitude is smaller, while the active power oscillation amplitude is larger. Figure 7 In condition 4, the gain ratio of the transfer function at the oscillation frequency point between E and P and between P and E ( When the voltage is greater than that of operating condition 3, the oscillation transmission effect between P and E exacerbates the oscillation between voltage in operating condition 3 and active power in operating condition 4, while suppressing the oscillation between active power in operating condition 3 and voltage in operating condition 4.

[0106] like Figure 8 As shown, the amplitude of f to E at the oscillation frequency point under operating condition 4 is smaller than that under operating condition 3, indicating that the oscillation transmission effect of f to E is weaker under operating condition 4. Therefore, the voltage oscillation under operating condition 4 is suppressed. Figure 8 In condition 4, the gain ratio of the transfer function at the oscillation frequency point between E and f and between f and E ( When the value is greater than that of operating condition 3, there is an oscillation transmission effect between f and E, which exacerbates the oscillation between the frequency of operating condition 3 and the voltage of operating condition 4, and suppresses the oscillation between the voltage of operating condition 3 and the frequency of operating condition 4.

[0107] like Figure 9 As shown, in operating conditions 5 and 6, the transfer function from Q to f exhibits a suppressed oscillation transfer effect when the amplitude is less than 0 at the oscillation frequency point, while the transfer function from f to Q exhibits an amplified oscillation transfer effect when the amplitude is greater than 0 at the oscillation frequency point. In this case, the oscillation amplitude of reactive power is more pronounced than that of frequency. Compared to operating condition 5, the amplitude of f to Q is larger in operating condition 6, while the amplitude of Q to f is smaller. Therefore, the frequency oscillation amplitude is smaller in operating condition 6, while the reactive power oscillation amplitude is larger. Figure 9 In condition 5, the gain ratio of the transfer function at the oscillation frequency point between f and Q is ( ). When the value is greater than that of operating condition 6, the oscillation transmission effect between Q and f exacerbates the oscillation of the frequency of operating condition 5 and the reactive power of operating condition 6, while suppressing the oscillation of the reactive power of operating condition 5 and the frequency of operating condition 6.

[0108] like Figure 10 As shown, the amplitude of Q to P at the oscillation frequency point in operating condition 5 is smaller than that in operating condition 6, indicating that the oscillation transmission effect of Q to P is stronger in operating condition 6. Therefore, the reactive power oscillation amplitude in operating condition 6 is more pronounced. Figure 10 In condition 6, the gain ratio of the transfer function at the oscillation frequency point between Q and P and between P and Q is ( When the value is greater than that of operating condition 5, the oscillation transmission effect between Q and P exacerbates the oscillation between active power in operating condition 5 and reactive power in operating condition 6, while suppressing the oscillation between reactive power in operating condition 5 and active power in operating condition 6.

[0109] To further verify the correctness of the analytical framework, this invention includes an experimental verification section. The circuit parameters and control parameters are consistent with the simulation parameters, as shown in Table 1. The parameters for operating conditions 1 to 6 are shown in Table 2. An integrated semi-physical experimental platform was built, including a host PC, a host computer, a rapid prototyping controller (RCP), a hardware-in-the-loop (HIL) circuit, and an oscilloscope, among other experimental equipment. Based on the actual operating parameters of the GFM-VSG system (such as the grid rated voltage, filter inductance, and resistance), six different operating conditions were set to simulate different situations of oscillation transfer effects in the system. Based on the above experimental platform, the correlation between oscillation transfer effects and system stability was verified by analyzing the oscillation amplitude and frequency response of the experimental data. The experimental results were compared with the theoretical analysis results to further verify the effectiveness and accuracy of the proposed oscillation transfer model and evaluation framework, providing a reliable experimental basis for the stability analysis and optimization of the GFM-VSG system.

[0110] Table 2 Parameter Table for Operating Conditions 1-6

[0111] The experimental verification of the method is as follows: To further verify the accuracy and robustness of the proposed power grid impedance disturbance model, this invention conducts experimental verification on a Hardware-in-the-Loop (HIL) experimental platform. The experimental system mainly consists of a HIL real-time simulation model, a controller, an I / O board, an oscilloscope, and a host computer for system configuration and data recording. The real-time simulator uses a 1... The simulation step size is used to model the power circuit in real time, thereby enabling high-precision capture of the system's dynamic response characteristics. Meanwhile, the GFM inverter controller is implemented with a sampling frequency of 10kHz, ensuring that the control algorithm can be executed in real time, stably, and accurately during the HIL experiment, thus providing reliable experimental support for verifying the effectiveness of the proposed model.

[0112] As shown in Figures 11(a), 11(b), 12(a), 12(b), 13(a), 13(b), 14(a), 14(b), 15(a), 15(b), 16(a), and 16(b), the experimental results for operating conditions 1 to 6 correspond to the theoretical analysis results. The experimental results show that the frequency oscillation amplitude in operating condition 1 is greater than that in operating condition 2, while the active power oscillation amplitude in operating condition 1 is smaller than that in operating condition 2. This experimental result is consistent with… Figure 5 The theoretical analysis results further validated the effectiveness and accuracy of the model.

[0113] Similarly, in operating condition 3, the voltage oscillation amplitude is greater than in operating condition 4, but the reactive power oscillation amplitude is smaller in operating condition 3 than in operating condition 4. Likewise, in operating condition 3, the active power oscillation amplitude is greater than in operating condition 4, while the reactive power oscillation amplitude is smaller in operating condition 4. In operating condition 4, the frequency oscillation amplitude is greater than in operating condition 3, but the voltage oscillation amplitude is smaller in operating condition 3. These experimental results are respectively... Figure 6 , Figure 7 and Figure 8 The theoretical analysis results correspond.

[0114] In operating condition 5, the frequency oscillation amplitude is greater than in operating condition 6, but the reactive power oscillation amplitude is smaller than in operating condition 6. Similarly, in operating condition 5, the active power oscillation amplitude is greater than in operating condition 6, but the reactive power oscillation amplitude is smaller than in operating condition 6. These experimental results are consistent with... Figure 9 and Figure 10 The results correspond to the theoretical analysis.

[0115] The above results show that, due to the influence of oscillation transmission effect, the variation trend of oscillation amplitude between the same two electrical quantities is not consistent under different operating conditions, verifying the effectiveness of the proposed modeling method and analysis framework. Furthermore, the magnitude of the amplitude-frequency characteristic at the oscillation frequency point of the oscillation transmission model can intuitively reflect the strength of the oscillation transmission effect between the corresponding electrical quantities, and the experimental results are consistent with this characteristic.

[0116] Experimental and simulation results demonstrate that this method has good applicability and engineering practical value in new energy power generation systems, effectively revealing the generation mechanism and transmission law of oscillations between different electrical quantities. To verify the effectiveness of the proposed method, six different operating conditions were set up to verify the oscillation transmission effect between the following variable pairs: frequency-active power, active power-voltage, frequency-voltage, frequency-reactive power, and active power-reactive power. The results show that oscillation transmission effects are prevalent between different electrical quantities, leading to changes in the dynamic state of the relevant electrical quantities. The results of each example demonstrate the universality of the proposed modeling and analysis method, and the method was verified through hardware-in-the-loop (HIL) experiments. This provides a theoretical basis and engineering guidance for the parameter design of grid-type virtual synchronous machine controllers and the improvement of system robustness.

[0117] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing the oscillation transmission effect in a network-type virtual synchronous machine system, characterized by: include: A small-signal model of the GFM-VSG system is established. Based on the small-signal model, the coupling transfer function between various electrical quantities is established, and an oscillation transfer model of the GFM-VSG system is also established. These electrical quantities include active power. reactive power ,frequency ,Voltage Based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, the oscillation transfer effect between various electrical quantities is evaluated as either an amplification effect or a suppression effect. Based on the gain ratio of the oscillation transfer between various electrical quantities, the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions is determined.

2. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 1, characterized in that: The process of establishing a small-signal model for a GFM-VSG system includes: Kirchhoff's voltage law and Kirchhoff's current law are used to analyze and establish the AC side loop equations of the inverter; The inverter output voltage and current are transformed using the dq transformation method; A small-signal model of the GFM-VSG system is established based on the AC side output power of the GFM-VSG system.

3. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 2, characterized in that: The inverter AC side loop equation is: By performing coordinate transformation on the inverter output voltage and current using the dq transformation method, we obtain: in, , The inverter output voltages are respectively of axis, Axial components, , The inverter output current is respectively of axis, Axial components, , These are the grid voltages. of axis, Axial components.

4. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 3, characterized in that: The equations for the small-signal model of the GFM-VSG system are: in, For active power small signal quantity, For reactive power small signal quantity, The inverter-side voltage is the d-axis steady-state component. This represents the q-axis steady-state component of the inverter-side voltage. The steady-state d-axis component of the inverter-side current. This represents the q-axis steady-state component of the inverter-side current. This refers to the small signal quantity of the d-axis component of the inverter-side voltage. Small signal quantity of the q-axis component of the inverter-side voltage.

5. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 1, characterized in that: The coupling transfer function between electrical quantities is: , , , The expression is: in, The voltage amplitude output by the converter. This is the effective value of the rated voltage of the power grid. , , , For filter inductance and parasitic resistance, , For the equivalent resistance and inductance of the power grid, The phase angle difference between the converter and the power grid. The rated angular frequency, It is a complex number.

6. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 5, characterized in that: The oscillation transfer model of the GFM-VSG system is: Active power Transmitted to frequency oscillatory transfer function ,frequency Transfer to active power oscillatory transfer function They are respectively: Active power Transmitted to voltage oscillatory transfer function ,Voltage Transfer to active power oscillatory transfer function They are respectively: reactive power Transmitted to frequency oscillatory transfer function ,frequency Transfer to reactive power oscillatory transfer function They are respectively: reactive power Transmitted to voltage oscillatory transfer function ,Voltage Transfer to reactive power oscillatory transfer function They are respectively: frequency Transmitted to voltage oscillatory transfer function ,Voltage Transmitted to frequency oscillatory transfer function They are respectively: reactive power Transfer to active power oscillatory transfer function Active power Transfer to reactive power oscillatory transfer function They are respectively: in, , , The rated angular frequency, The active loop inertia coefficient. This is the active power loop damping coefficient. The reactive loop inertia coefficient, This is the reactive power ring damping coefficient. It is a complex number.

7. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 1, characterized in that: Based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, the method for evaluating whether the oscillation transfer effect between various electrical quantities is an amplification or suppression of the transfer effect is as follows: If electrical quantity Transmitted to electrical quantities oscillatory transfer function The amplitude-frequency characteristic is that the amplitude is greater than 0 at the oscillation frequency point, and the electrical quantity Transmitted to electrical quantities The oscillation transmission effect is an amplification transmission effect; otherwise, the electrical quantity... Transmitted to electrical quantities The oscillation transmission effect is a suppression transmission effect, electrical quantity Electrical quantities Active power reactive power ,frequency ,Voltage Any electrical quantity in, and electrical quantity Electrical quantities For different electrical quantities.

8. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 1, characterized in that: The expression for the gain ratio of oscillation transmission between various electrical quantities is: in, Electrical quantity Electrical quantities The gain ratio of the oscillations between them. Electrical quantity Transmitted to electrical quantities The oscillatory transfer function, Electrical quantity Transmitted to electrical quantities The oscillatory transfer function, It is a complex number.

9. The method for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system according to claim 1, characterized in that: Based on the gain ratio of oscillation transmission between various electrical quantities, the method for determining the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions is as follows: like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude; like This indicates that the oscillation transmission causes the operating condition to... China Electric Power The oscillation amplitude is less than that of the operating condition. China Electric Power Oscillation amplitude, oscillation transmission affects operating conditions China Electric Power The oscillation amplitude is greater than that of the operating condition. China Electric Power Oscillation amplitude , Operating conditions Operating conditions China Electric Power Electrical quantities The gain ratio of the oscillation transmission between them.

10. A system for analyzing the oscillation transmission effect of a network-type virtual synchronous machine system, characterized in that: include: The small-signal modeling module is used to build a small-signal model of the GFM-VSG system. The oscillation transfer modeling module is used to establish the coupling transfer function between various electrical quantities in the small-signal model of the GFM-VSG system, and to establish the oscillation transfer model of the GFM-VSG system. These electrical quantities include active power. reactive power ,frequency ,Voltage ; The oscillation transfer analysis module is used to evaluate whether the oscillation transfer effect between various electrical quantities is an amplification or suppression effect based on the amplitude-frequency characteristics of the oscillation transfer model of the GFM-VSG system, and to determine the magnitude of the oscillation amplitude of the corresponding electrical quantities under different operating conditions based on the gain ratio of the oscillation transfer between various electrical quantities.

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