Method for suppressing wide frequency oscillation and frequency support of GFM device based on double time scale

Abstract

The application provides a wide-frequency oscillation suppression and frequency support method for a GFM device based on a double time scale, which realizes the functions of wide-frequency oscillation suppression and accurate frequency support through the cooperative control of a dynamic virtual impedance module and a composite virtual inertia module. The dynamic virtual impedance module adjusts the virtual impedance parameters based on frequency segmentation, effectively eliminating sub / super-synchronous oscillation and high-frequency harmonics; the composite virtual inertia module allocates virtual inertia weights in real time according to the dynamic inertia capacity, SOC state and power angle characteristics of the device, thereby optimizing the power distribution among the devices and playing a role in frequency support for the system. The oscillation and frequency response capabilities of the dynamic virtual impedance module and the composite virtual inertia module for the GFM device are dynamically optimized under different time scales, the contradiction between oscillation suppression and frequency maintenance is coordinated, the adaptability of the device and the stability of the system are improved, and the method is suitable for the cooperative operation control of multiple GFM devices in the grid-forming power supply scenarios such as wind power, photovoltaic power and energy storage.

Description

Technical Field

[0001] This invention relates to a novel power system GFM (Grid Forming) control technology, specifically a method for coordinated control of dynamic virtual impedance and composite virtual inertia under dual time scales, applicable to grid-type scenarios of new energy power plants such as wind power and photovoltaic power. Background Technology

[0002] With the continuous increase in renewable energy penetration and the large-scale application of power electronic devices, the power system is undergoing a structural transformation from a traditional synchronous machine-dominated grid to a power electronic grid. During this transition, the grid's inertia support capability is significantly weakened, and its disturbance rejection performance declines, leading to increased risks of frequency instability and broadband oscillations. GFM technology, as a key means to address these issues, provides voltage source support and active inertia response for weak grids by simulating the operating characteristics of synchronous machines, and has become an important choice for the stable operation of grids with a high proportion of renewable energy.

[0003] However, a prominent technical contradiction exists in the practical application of GFM devices: on the one hand, the system relies on GFM devices to provide second-level inertia support to maintain frequency stability; on the other hand, the interaction between new energy units and power electronic equipment easily induces sub- / supersynchronous oscillations (frequency range typically 2-150 Hz), urgently requiring GFM devices to suppress broadband oscillations at the millisecond level through virtual impedance adjustment. Traditional single-layer control architectures struggle to meet both requirements, exhibiting the following three typical drawbacks:

[0004] (1) Time scale conflict: Oscillation suppression requires the virtual impedance module to respond quickly (<20ms), while inertia support needs to be maintained for several seconds to tens of seconds. These two requirements will restrict the parameter tuning of a single control loop. For example, increasing the virtual damping can suppress oscillation, but it will affect the speed of inertia response; decreasing it will accelerate frequency tuning, but it may amplify the risk of resonance.

[0005] (2) Resource allocation contradiction: This problem is particularly likely to occur in GFM energy storage devices, whose limited capacity needs to meet two objectives: oscillation suppression at the millisecond level requires the absorption of resonant energy, while frequency support at the s level requires the release of energy; dynamic competition for power resources will exacerbate the aging of the equipment and may even trigger protection actions.

[0006] (3) Parameter coupling instability: The strong coupling characteristics of virtual impedance and virtual inertia may trigger positive feedback oscillation. For example, the power mutation during the inertia support process may excite subsynchronous resonance, while the rapid adjustment of virtual impedance may interfere with the frequency recovery trajectory, forming a vicious cycle of "oscillation-frequency modulation".

[0007] Therefore, it is evident that the existing control architecture design for oscillation suppression and frequency modulation in GFM equipment suffers from a focus on optimizing a single function (such as improving virtual impedance algorithms or inertia allocation strategies) and lacks a collaborative mechanism across time scales. Furthermore, methods attempting joint optimization are mostly based on static weight allocation, which cannot adapt to the dynamic coupling scenarios of broadband oscillations and frequency disturbances. For example, when the system simultaneously encounters subsynchronous oscillations (such as 26 Hz resonance caused by wind farms) and sudden load changes, existing technologies struggle to coordinate impedance reshaping in the high-frequency band with inertia output in the low-frequency band. Summary of the Invention

[0008] Given the limitations and shortcomings of existing control architectures for oscillation suppression and frequency modulation in GFM devices, this invention aims to propose a control method that can balance broadband oscillation suppression and frequency support. It constructs a control system architecture for broadband oscillation suppression and frequency support in GFM devices based on dual time scales. The method utilizes a dynamic virtual impedance module and a composite virtual inertia module to respectively achieve broadband oscillation suppression and frequency modulation. Furthermore, it employs a dynamic boundary constraint mechanism and a hierarchical response strategy to address conflicts, thereby resolving the inherent contradictions between these two functions. This achieves millisecond-level broadband oscillation suppression through dynamic virtual impedance, providing a stable environment for second-level frequency modulation; and second-level precise frequency support through composite virtual inertia, avoiding the "oscillation-frequency modulation-oscillation" cycle.

[0009] According to a first aspect of the present invention, a method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales is proposed, comprising the following steps:

[0010] Step 1: Construct a dual-time-scale control system for the GFM device, including a dynamic virtual impedance module with millisecond-level response and a composite virtual inertia module with second-level response, forming a hierarchical collaborative control.

[0011] Step 2: Design a three-band dynamic virtual impedance module to divide the frequency f into low, medium, and high bands, and determine the impedance Z of each band. low (s), Z mid (s) and Z high (s), corresponding to inertia support, damping optimization and coordinated control harmonic suppression respectively, and a fast Fourier transform module is introduced to extract the system harmonic components and resonant frequency, and dynamically adjust the impedance parameters of each frequency band.

[0012] Step 3: Construct a composite virtual inertia module and obtain the dynamic inertia gain coefficient K of the GFM device based on frequency deviation, SOC state, and device power angle. v And according to the weight ω allocated to each GFM device inertia i Dynamically allocate virtual inertia across multiple devices;

[0013] Step 4: Based on the control structure and hardware constraints of the GFM device, modify the mathematical models and constraints of the dynamic virtual impedance module and the composite virtual inertia module to obtain parameter expressions and boundary constraints suitable for network-type devices.

[0014] Step 5: Design a damping observer to obtain the real-time damping value ζ. obs Furthermore, a damping-inertia adaptive coordinator module is added after the composite virtual inertia module, using the real-time observed damping value ζ. obs To avoid system oscillations caused by inertia adjustment, the upper limit of the virtual inertia is adjusted, and the Lyapunov energy function is used as a constraint; and

[0015] Step 6: Set the objective function based on frequency stability, economy and damping lower limit, and set a three-layer emergency response mechanism to avoid the conflict between the two-layer control of the dynamic virtual impedance module and the composite virtual inertia module.

[0016] In an optional embodiment, the frequency is divided into three control frequency bands from low to high, corresponding to different control strategies: the low frequency band focuses on inertia support and frequency recovery, the mid frequency band focuses on damping optimization and oscillation suppression, and the high frequency band focuses on resonance elimination and harmonic filtering.

[0017] In an optional embodiment, dynamic impedance adjustment is achieved by introducing FFT sensing. The FFT module performs spectral analysis on the grid voltage / current signal to obtain the amplitude and corresponding frequency components of each harmonic, enabling the identification of oscillations or distortions at various frequencies in the current system. Based on the actual detected harmonic energy, the proportional-derivative coefficients (control coefficients) are dynamically adjusted to reshape the virtual impedance across the three frequency bands, achieving adaptive shaping of the virtual impedance's frequency-amplitude characteristics and avoiding blindly increasing K. d To suppress harmonics across all frequency bands, which can cause excessive high-frequency impedance, leading to voltage distortion or power oscillations, or if K... d The problem of high-frequency harmonics not being filtered out when the frequency is too low is addressed, while the target frequency is provided for the subsequent response (active damping injection).

[0018] In an optional embodiment, parameter coupling constraints are set for the dynamic virtual impedance module as an auxiliary standard to assist in adjusting the virtual impedance and improve its adaptability. Specifically, this includes:

[0019] 1) Frequency-impedance mapping

[0020] The frequency deviation is mapped to the proportional-derivative coefficients by an exponential function, and the impedance amplitude is dynamically adjusted using the updated proportional-derivative coefficients to suppress subsynchronous / supersynchronous oscillations.

[0021] 2) Power-impedance feedback

[0022] The impedance correction is generated using the power deviation (ΔP, ΔQ) and the virtual impedance is dynamically adjusted based on the impedance correction, where ΔP and ΔQ represent the active power deviation and reactive power deviation of the system, respectively.

[0023] This enhances the adaptability to subsynchronous / supersynchronous oscillations. By incorporating steady-state deviations into impedance adjustment through two types of coupling, the virtual impedance can not only suppress oscillations but also participate in the steady-state regulation of power / frequency. Furthermore, it avoids the negative interaction between the virtual impedance and the power loop. If the virtual impedance is determined solely by FFT, the response may be too slow or the direction may be incorrect during power surges. Power-impedance feedback directly utilizes the power error signal, enabling rapid impedance correction and preventing power oscillations from being amplified.

[0024] In an optional embodiment, for the GFM device, the dynamic virtual impedance expression model is updated by combining the transfer function of the grid-connected converter to obtain the updated virtual impedance. Simultaneously, considering that the GFM device employs numerous power electronic components, the amplitude of the virtual impedance is limited by the switching frequency and heat dissipation. Therefore, considering the hardware amplitude limitations of the GFM device, the dynamic virtual impedance expression model is constrained based on the maximum power of the switch, the on-resistance of the components, the loss coefficient related to the component type, the switching frequency of the components, and the measured DC bus voltage and converter-side current parameters. This allows for correction based on the characteristics of the GFM device. By multiplying by the converter transfer function and hardware constraints, the ideal model is mapped to the real physical device, avoiding hardware over-limits during system adjustment and ensuring system stability.

[0025] In an optional embodiment, the constructed composite virtual inertia module takes the dynamic inertia gain coefficient of each GFM device as input and dynamically adjusts the virtual inertia weight allocation of multiple devices to achieve second-level precise support for the power grid frequency; wherein, the dynamic inertia gain coefficient of each GFM device is used to provide real-time feedback on its adjustable inertia capacity, providing a decision basis for the inertia allocation strategy.

[0026] In an optional embodiment, the inertia allocation of each GFM device is adjusted to minimize system frequency deviation and device loss. The total inertia required by the system and the maximum virtual inertia capacity of each device are combined, and the upper limit of the inertia contribution of each device is constrained by weight. The weight of the inertia allocation of the n GFM devices in the system is tuned according to the real-time status coefficient of the device (characterizing the availability and health of the device).

[0027] In an optional embodiment, to avoid excessively low damping of the device during the adjustment of virtual inertia, which could lead to system oscillation and instability, a damping observer is designed to obtain real-time damping values. A damping-inertia adaptive coordinator module is added after the composite virtual inertia module to achieve dynamic coupling of parameters, actively limit the uncontrolled increase of inertia, and avoid oscillation-frequency modulation positive feedback. When the coordinator detects low damping, it immediately compresses the inertia output, cuts off the positive feedback transmission, and resolves the inherent contradiction between inertia and damping. At the same time, a smooth transition (nonlinear decay) is achieved through the tanh function to avoid the impact caused by hard switching.

[0028] In an optional embodiment, an objective function is set based on frequency stability, economy, and damping lower limit, and a three-layer emergency response mechanism is established to avoid conflicts between the dual-layer control of the dynamic virtual impedance module and the composite virtual inertia module. On the one hand, losses and damping health are explicitly incorporated into the optimization, making the control decision more in line with actual operation and maintenance needs. On the other hand, by injecting impedance fluctuations with opposite phases at the resonant frequency point, active oscillation suppression of impedance reshaping is achieved. Overall, the three-layer response priority achieves the complementarity of damping priority, frequency priority, and control under composite crisis.

[0029] The proposed method for broadband oscillation suppression and frequency support based on dual-timescale GFM devices is mainly implemented through two modules: a dynamic virtual impedance module and a composite virtual inertia module. The dynamic virtual impedance module primarily suppresses broadband oscillations and eliminates resonance. It constructs the virtual impedance of the GFM device using a three-band decoupling method, separating the device's inertia support and oscillation suppression functions to address key issues under different operating conditions. FFT and parameter coupling functions are added to this module to adjust device parameters in real time. The composite virtual inertia module primarily supports frequency and maintains the stability of the system containing the GFM device. It calculates the device's dynamic inertia gain coefficient and allocates all the required inertia to the system according to reasonable standards and weights, thereby enabling the GFM devices to cooperate and stabilize the frequency.

[0030] In the design of this invention, considering the interaction between the two modules, the real-time damping value of the damping observer is set and the actual observed damping value is applied to the damping-inertia adaptive module and the final objective function to ensure that the damping value is maintained above the minimum value during the adjustment of the virtual inertia.

[0031] Finally, given the two control methods and their coordination, three conflict avoidance strategies are established to coordinate the functions of the two modules in the control architecture. This ensures that oscillation suppression and frequency support are decoupled under the premise of coordination, economy, and safety, thereby achieving global coordinated regulation and preventing system collapse and oscillation or protection shutdown under extreme conditions.

[0032] As can be seen from the above technical solutions of the present invention, compared with the prior art, the significant advantages of the present invention are:

[0033] (1) The dynamic virtual impedance module (ms level) quickly suppresses wideband oscillations, providing a stable environment for the composite virtual inertia module (s level); the latter achieves precise second-level frequency support through dynamic inertia allocation. The two modules work together to solve the contradiction between oscillation suppression and frequency stability, breaking through the limitations of single time scale control.

[0034] (2) A three-band dynamic virtual impedance design is adopted, combined with FFT real-time harmonic analysis, to dynamically adjust the impedance parameters; adaptive coupling of parameters is achieved through frequency-impedance mapping and power-impedance feedback, which significantly improves the adaptability to sub / supersynchronous oscillation and multi-harmonic scenarios.

[0035] (3) Introduce dynamic inertia gain coefficient to quantify the equipment adjustment potential, and design a weight allocation strategy in combination with constraints such as SOC, switching margin and power angle difference; and design a three-layer emergency response mechanism based on the collaborative architecture of the two control modules to solve the power contention problem between virtual resistor frequency modulation response and oscillation suppression, reduce the risk of equipment aging, and improve system robustness.

[0036] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below may be considered part of the subject matter of this disclosure, provided that such concepts do not contradict each other. Furthermore, all combinations of the claimed subject matter are considered part of the subject matter of this disclosure.

[0037] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and beneficial effects of exemplary embodiments, will become apparent from the following description, or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0038] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings.

[0039] Figure 1 This is a schematic diagram of the overall logic of the GFM device control method based on dual time scales according to an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of the dynamic virtual impedance module according to an embodiment of the present invention.

[0041] Figure 3This is a schematic diagram of the composite virtual inertia module according to an embodiment of the present invention.

[0042] Figure 4 This is a schematic diagram of a three-layer emergency response mechanism according to an embodiment of the present invention.

[0043] Figure 5 A comparison chart of frequency regulation and total harmonic distortion (THD) between traditional control and dual-layer control. Detailed Implementation

[0044] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0045] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0046] According to an embodiment of the present invention, in combination Figures 1-5 As shown, the method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales includes the following steps:

[0047] Step 1: Construct a dual-time-scale control system for the GFM device, including a dynamic virtual impedance module with millisecond-level response and a composite virtual inertia module with second-level response, forming a hierarchical collaborative control.

[0048] Step 2: Design a three-band dynamic virtual impedance module to divide the frequency f into low, medium, and high bands, and determine the impedance Z of each band. low (s), Z mid (s) and Z high (s), corresponding to inertia support, damping optimization and coordinated control harmonic suppression respectively, and a fast Fourier transform module is introduced to extract the system harmonic components and resonant frequency, and dynamically adjust the impedance parameters of each frequency band.

[0049] Step 3: Construct a composite virtual inertia module and obtain the dynamic inertia gain coefficient K of the GFM device based on frequency deviation, SOC state, and device power angle. v And according to the weight ω allocated to each GFM device inertia i Dynamically allocate virtual inertia across multiple devices;

[0050] Step 4: Based on the control structure and hardware constraints of the GFM device, modify the mathematical models and constraints of the dynamic virtual impedance module and the composite virtual inertia module to obtain parameter expressions and boundary constraints suitable for network-type devices.

[0051] Step 5: Design a damping observer to obtain the real-time damping value ζ. obs Furthermore, a damping-inertia adaptive coordinator module is added after the composite virtual inertia module, using the real-time observed damping value ζ. obs To avoid system oscillations caused by inertia adjustment, the upper limit of the virtual inertia is adjusted, and the Lyapunov energy function is used as a constraint; and

[0052] Step 6: Set the objective function based on frequency stability, economy and damping lower limit, and set a three-layer emergency response mechanism to avoid the conflict between the two-layer control of the dynamic virtual impedance module and the composite virtual inertia module.

[0053] As an optional implementation, in step 2, the frequency f is divided into three control frequency bands from low to high as follows:

[0054] 1) In the low-frequency range f ∈ [0.1, 1.5) Hz, the focus is on inertia support and frequency recovery;

[0055] 2) In the mid-frequency range f ∈ [2,50)Hz, the focus is on damping optimization and oscillation suppression;

[0056] 3) In the high-frequency band f ∈ [50, +∞) Hz, the focus is on coordinated control of resonance elimination and harmonic filtering.

[0057] Furthermore, based on the low, medium, and high control frequency bands, the expression model for dynamic virtual impedance is modified as follows:

[0058] Z v (s)= R v +jX v

[0059] = W L (f) ·Z low (s)+[1- W L (f)- W H (f)] ·Z mid (s)+ W H (f)·Z high (s);

[0060] Among them, Z low (s), Z mid (s) and Z high (s) represent the impedances for the low, mid, and high frequency bands, respectively; W L (f) and W H(f) are the continuously adjustable frequency domain weighting coefficients for low and high frequencies, respectively, as expressed below:

[0061] ;

[0062] Where k∈(0,1), it represents the transition speed controlling the change of the weight coefficient; f L and f H These represent the center frequencies for low-frequency and high-frequency weight switching, respectively; in this example, f is set to... L For 0.1Hz, f H 50Hz;

[0063] The system's harmonic components and resonant frequencies are extracted in real time using a Fast Fourier Transform (FFT) module, and the impedance parameters for each frequency band are dynamically adjusted. The proportional-differential coefficient K... p (f) and K d (f):

[0064] ;

[0065] Where |H(k)| is the amplitude of the k-th harmonic obtained through FFT analysis; W(f k H(f) is the frequency weighting function for the k-th harmonic; α and β are normalization coefficients, determined by the Lyapunov stability criterion; H(f) represents the system response amplitude under a frequency perturbation of f.

[0066] Based on the dynamically adjusted proportional-differential coefficient K p (f) and K d (f) Dynamically update the impedance Z of each frequency band low (s), Z mid (s) and Z high (s):

[0067] ;

[0068] Among them, T low This represents the time constant used to simulate physical inertia; in this example, T low =0.5s; Z low (s) is used to provide inertial support; For virtual resistance, K h Z represents the impedance gain coefficient in the high-frequency band; s is the Laplace operator; Z mid (s) is used to optimize damping; ω high =2π×10rad / s;Z high (s) is used to actively enhance high-frequency impedance in order to absorb resonant energy.

[0069] As an optional implementation, in step 4, parameter coupling constraints are set for the dynamic virtual impedance module as an auxiliary standard to assist in adjusting the virtual impedance and improve its adaptability. Specifically, this includes:

[0070] 1) Frequency-impedance mapping

[0071] Through exponential function Mapping the frequency deviation Δf to the proportional-differential coefficient K p (f) and K d (f), and utilize the updated K p (f) and K d (f) Dynamically adjust the impedance amplitude to suppress sub / supersynchronous oscillations; for example, when Δf is detected to be greater than 0.5 Hz, by... To reduce the impedance amplitude; K p0 (f) represents the proportional coefficient before adjustment;

[0072] 2) Power-impedance feedback

[0073] Impedance correction is generated using power deviation (ΔP, ΔQ). And dynamically adjust the virtual impedance based on the impedance correction amount:

[0074] ;

[0075] Where γ is the power sensitivity coefficient, and ΔP and ΔQ represent the active power deviation and reactive power deviation of the system, respectively. For example, when ΔP exceeds 10P... rated At that time, according to Increase the resistance value to absorb excess power.

[0076] As an optional implementation, in step 4, for the GFM device, the dynamic virtual impedance expression model is updated by combining the transfer function of the grid-type converter to obtain the updated virtual impedance, as shown below:

[0077] ;

[0078] Among them, G droop (s) and G VSG (s) are the transfer functions for droop control and VSG control, respectively, and are specifically expressed as follows:

[0079] ;

[0080] Among them, D p T is the active droop coefficient; droop T is the time constant of the droop response, used to smooth power distribution; vir D is the virtual inertial time constant. vir ω is the virtual damping coefficient.n This is the rated angular frequency;

[0081] Considering the numerous power electronic devices used in GFM equipment, and taking into account the hardware amplitude limitations of GFM equipment, including the switching frequency and heat dissipation limitations of the power electronic devices, the dynamic virtual impedance expression model is constrained to satisfy:

[0082] ;

[0083] Among them, V dc I is the DC bus voltage; rms P is the converter-side current measured in real time. sw,max R is the maximum power of the switch; on k is the on-resistance of the device; sw The loss factor, which is related to the device type, is calibrated through loss testing; f sw This is the switching frequency of the device.

[0084] As an optional implementation, in step 3, the constructed composite virtual inertia module uses the dynamic inertia gain coefficient K of each GFM device. v As input, and dynamically adjust the virtual inertia weight allocation of multiple devices to achieve second-level precise support for power grid frequency;

[0085] Among them, the dynamic inertia gain coefficient K of each GFM device v K is used to provide real-time feedback on its adjustable inertia capacity, providing a basis for decision-making regarding inertia allocation strategies. v The expression model is as follows:

[0086] ;

[0087] Where Δf represents the frequency deviation, and α·Δf is used for the direct response frequency deviation; the coefficient α = (2H sys ) / Δf max H sys Let Δf be the total inertia required by the system. max This represents the maximum allowable frequency deviation of the system.

[0088] Used to suppress abrupt gain changes caused by high-frequency disturbances (such as rapid frequency fluctuations) and improve stability; β represents the control damping strength, β = 1 / (2πf c ) 2 , f c The cutoff frequency;

[0089] Among them, γ·SOC 0.5 This represents the SOC (State of Charge) feedback item, which limits over-discharge of stored energy and extends equipment lifespan through SOC feedback. For example, when SOC < 30%, γ·SOC 0.5Rapid decay significantly reduces gain and avoids over-discharge.

[0090] As an optional implementation, in step 4, the inertia allocation of each GFM device is adjusted to minimize system frequency deviation and device losses, and this is done through weight ω. i The upper limit of the inertia contribution of each device is constrained as follows:

[0091] ;

[0092] Among them, K v,i Describe the dynamic inertia gain coefficient of device i; For K v,i The lower limit;

[0093] For the n GFM devices in the system, the inertia weight allocation is as follows:

[0094] ;

[0095] Wherein: H n H is the total inertia required by the system. v,i The maximum virtual inertia capacity of device i, and the weights ω of each device. i Adjust as follows:

[0096] ;

[0097] Wherein: S i (t) is the real-time state coefficient of device i, with a value range of [0,1], used to characterize the availability and health of the device, where 0≤S i (t) ≤1.

[0098] For example, for energy storage SOC, For fans, when the speed exceeds the limit, S WT (t) decreases from 1 to 0.5; for photovoltaics, S PT (t)=1-0.2·(T(t)-T rated It decays linearly when the temperature exceeds the limit.

[0099] In an optional embodiment, in step 4, for network-type devices, a unique weighting factor is added based on the switching frequency margin to adjust the dynamic inertia gain coefficient K. v The following corrections are made:

[0100] ;

[0101] Among them, T sw T is the converter switching cycle margin. sw =1 / f swf represents the limit of hardware response. sw The switching frequency; This is the maximum value allowed during the switching cycle; It is the switching frequency margin term, when the switching frequency f sw Approaching the upper limit, i.e., f sw Approaching At that time, T sw Approaching At this point, K is forcibly reduced. v To avoid the switching losses reaching their limit.

[0102] In an optional embodiment, when multiple GFM devices are connected in parallel, if the power angle difference... If the value is too large, it may cause circulating current or oscillation. Therefore, in step 4, for the case of multiple GFM devices connected in parallel, the weight ω of the inertia allocation of the GFM devices is adjusted. i Make the following corrections:

[0103] ;

[0104] in, The work angle penalty term; Δθ i κ is the power angle difference between device i and a typical reference node (such as the master VSG); κ is the penalty coefficient used to control the weight decay rate; in this embodiment, the penalty coefficient κ is between 5 and 10.

[0105] in, As an economic adjustment factor, C i (K v,i Let be the loss function of device i.

[0106] Taking lithium batteries as an example, their loss function is as follows:

[0107] ;

[0108] Where: θ1 and θ2 are aging coefficients, calibrated through accelerated life testing; I rms The effective value of the battery current, and K v,ESS Positive correlation; ξ is a SOC-sensitive factor, and the lower the SOC, the more exponentially the loss cost increases.

[0109] To avoid insufficient real-time damping of the device when adjusting the virtual inertia, in step 5, a damping observer is first designed to obtain the real-time observed damping value ζ. obs :

[0110] ;

[0111] Where: A1 and A2 are the amplitudes of adjacent oscillations, obtained through the time-domain envelope; τ ζ Here is the filter constant;

[0112] Then, a damping-inertia adaptive coordinator module is added after the composite virtual inertia module to monitor the damping value ζ in real time. obs This is used to adjust the upper limit of the virtual inertia, achieving dynamic parameter fitting. The final adjusted virtual inertia output is:

[0113] ;

[0114] Where, ζ min This indicates the minimum allowable damping value of the system; the output range of tanh is always between [-1, 1].

[0115] If ζ obs >>ζ min Then tanh(·)≈1, allowing the maximum virtual inertia output;

[0116] If ζ obs <<ζ min If tanh(·)≈0, then inertia regulation is forcibly turned off;

[0117] The Lyapunov energy function is used as a constraint to ensure that the system remains in a stable state during parameter adjustment.

[0118] ;

[0119] The stability criterion requires that the time derivative of the energy function is non-positive, that is:

[0120] ;

[0121] Where α and β are normalization coefficients. It should be understood that these normalization coefficients α and β are also used in the calculation of the proportional-differential coefficients in the aforementioned steps.

[0122] In an example of the present invention, take , , It leaves a certain margin of stability.

[0123] In an optional embodiment, in step 6, an objective function is set based on frequency stability, economy, and damping lower limit, and a three-layer emergency response mechanism is established to avoid conflicts between the dual-layer control of the dynamic virtual impedance module and the composite virtual inertia module, including:

[0124] Taking into account both frequency stability and economic efficiency, and incorporating dynamic damping ratio constraints, the objective function is set as follows:

[0125] ;

[0126] in: To optimize frequency stability, the system is ensured to quickly return to a stable frequency by minimizing the square integral of the frequency deviation. Considering economic optimization, the goal is to extend equipment life by minimizing the total cost of equipment wear and tear; Considering the damping ratio constraint of the equipment, limit the range of the damping ratio to prevent oscillation;

[0127] Where ρ = 10 λ represents the weight based on the higher damping ratio constraint; λ and η are the weighting coefficients:

[0128] When λ>>η, the focus is on frequency stability, which is suitable for frequency regulation in emergency grid conditions, such as emergency grid conditions when large-capacity units are disconnected from the grid, but may still lead to equipment overload.

[0129] When λ << η, the focus is on economy, which is suitable for steady-state operation, but may prolong the frequency recovery time.

[0130] To reduce mutual interference between the two-layer structure, a three-layer emergency response mechanism is set up, as follows:

[0131] 1) Damping priority layer

[0132] In ζ obs <ζ min When Δf > 0.5Hz, forced priority is applied:

[0133] ;

[0134] Among them, H v,i This represents the maximum virtual inertia capacity of device i. Represents the reference virtual inertia of device i; and These represent the increased virtual resistance and decreased virtual inertia after adjustment, respectively.

[0135] Thus, it can be seen that the damping priority layer means that when the observed real-time damping is too small, the upper limit of inertia is actively compressed, while the virtual resistance is exponentially enhanced.

[0136] 2) Frequency Priority Layer

[0137] When the frequency deviation Δf satisfies: Δf > 0.5Hz and ζ obs ≥ζ min hour:

[0138] ;

[0139] in, This represents the increase in virtual inertia after adjustment;

[0140] Therefore, the frequency priority layer indicates that the value of the provided virtual inertia should be increased when frequency fluctuations are too large; verification is required before startup. That is, the damping attenuation rate limit;

[0141] 3) Complex Crisis Layer

[0142] When the frequency deviation Δf satisfies Δf > 0.5Hz, ζ obs <ζ min And when the damping priority layer and frequency priority layer actions are not triggered:

[0143] ;

[0144] in, and These represent the upper limits of dynamic impedance and virtual inertia under a compound crisis, respectively; f res ΔZ represents the resonant frequency of the injected impedance; ΔZ represents the amplitude of the impedance fluctuation; τ represents the time constant of the exponential decay of the inertia.

[0145] Therefore, when both excessive frequency deviation and insufficient damping occur simultaneously, the inertia is actively reduced through exponential decay, breaking the resonant positive feedback, and an impedance fluctuation with opposite phase is injected at the resonant frequency point to form active damping.

[0146] The following simulation examples, combined with appendices, demonstrate this approach. Figures 1 to 5 The technical solutions provided by the above embodiments of the invention will be further described.

[0147] Combination Figure 1 The example demonstrates the overall framework design of a dual-timescale GFM device control method, divided into two layers: millisecond-level control and sigma-level control, which respectively implement oscillation suppression and frequency stabilization. The upper-level millisecond-level control module receives real-time signals (frequency and time), modifies the impedance model through dynamic virtual impedance modeling and GFM characteristics to achieve rapid response, and enhances the transient performance of GFM through FFT transformation, dynamic constraints, and parameter coupling. The lower-level sigma-level control module maintains frequency stability through dynamic inertia gain and a cooperative allocation mechanism, and achieves overall system optimization through a joint optimization function. The two layers complement each other: millisecond-level control provides a stable operating environment for sigma-level control, while sigma-level control avoids error accumulation and optimizes long-term performance.

[0148] Combination Figure 2The dynamic virtual impedance module structure is divided into low-frequency (0.1–1.5 Hz), mid-frequency (2–50 Hz), and high-frequency (>50 Hz) bands, each with different control objectives: the low-frequency band is mainly used for inertia support and frequency recovery; the mid-frequency band achieves oscillation suppression through optimized damping; and the high-frequency band enhances impedance to eliminate resonance and filter noise. Overall, the dynamic virtual impedance module obtains harmonic amplitudes through FFT analysis, calculates proportional-differential coefficients and frequency domain weighting functions, and finally synthesizes multi-band virtual impedances. This enables adaptive adjustment of dynamic characteristics at different frequencies, thus balancing stability, disturbance rejection, and dynamic response performance across the entire frequency domain.

[0149] Combination Figure 3 The composite virtual inertia module structure shown is divided into two parts: an input layer and a calculation layer. The input layer collects system parameters, equipment operating data, and power grid signals, including real-time information such as system inertia requirements, frequency deviation, equipment SOC status, and fan speed. The calculation layer calculates the inertia gain coefficient of the equipment based on the system parameters, forming a weighted virtual inertia response. Subsequently, the composite virtual inertia module allocates weights according to the overall system inertia requirements and the adjustment capabilities of each device, achieving coordinated control among multiple source devices. Simultaneously, considering the power angle deviation, the weights are corrected to conform to the characteristics of the GFM devices to ensure system frequency stability and dynamic balance. Overall, the composite virtual inertia module achieves adaptive inertia support and frequency stability control among different devices through dynamic allocation and coordinated adjustment.

[0150] Combination Figure 4 The figure illustrates a three-layer emergency response mechanism designed according to an embodiment of the present invention. As shown in the figure, the two-layer control mentioned in this invention will coordinate and control according to the different levels of urgency. For example, when there is a damping emergency or a frequency emergency with similar levels of urgency, the emergency response mechanism will adjust the response intensity of the virtual inertia module and the virtual impedance module, thereby giving priority to responding to the emergency state. When a compound emergency occurs, the emergency response mechanism will actively reduce the inertia through exponential decay, break the resonant positive feedback, and inject impedance fluctuations with opposite phase at the resonant frequency point to form active damping.

[0151] Combination Figure 5This figure compares the frequency regulation and THD of traditional control and two-layer control to characterize the superiority of the GFM (Geometric Flow Modulation) control method under dual time scales in terms of frequency stability, oscillation suppression capability, and dynamic response speed. The two solid blue lines in the figure represent the frequency characteristic curves of each control method, and the two dotted green lines represent the THD changes. Devices with hollow markers are those using a two-layer control architecture, while those without markers are those using a traditional control architecture. The model is simulated based on typical power grid disturbances, with an initial state of f=50Hz and THD=1.5%. A three-phase short-circuit fault occurs at t=5s, a 2Hz harmonic is injected at t=10s inducing subsynchronous oscillation, and a 65Hz harmonic is injected at t=20s inducing supersynchronous oscillation. Observation... Figure 5 It can be observed that the control method using the dual-layer control architecture proposed in this invention has significantly improved frequency modulation capability and broadband oscillation suppression capability compared with the traditional control architecture. The rate of change of frequency (RoCoF) is lower, the frequency nadir (FN) is higher, and the THD returns to the normal level more quickly when the system is at risk of oscillation.

[0152] The details not described in this specification are existing knowledge known to those skilled in the art. While the invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of this invention is determined by the claims.

Claims

1. A method for broadband oscillation suppression and frequency support in GFM devices based on dual time scales, characterized in that, Includes the following steps: Step 1: Construct a dual-time-scale control system for the GFM device, including a dynamic virtual impedance module with millisecond-level response and a composite virtual inertia module with second-level response, forming a hierarchical collaborative control. Step 2: Design a three-band dynamic virtual impedance module to divide the frequency f into low, medium, and high bands, and determine the impedance Z of each band. low (s), Z mid (s) and Z high (s), corresponding to inertia support, damping optimization and coordinated control harmonic suppression respectively, and a fast Fourier transform module is introduced to extract the system harmonic components and resonant frequency, and dynamically adjust the impedance parameters of each frequency band. Step 3: Construct a composite virtual inertia module and obtain the dynamic inertia gain coefficient K of the GFM device based on frequency deviation, SOC state, and device power angle. v And according to the weight ω allocated to each GFM device inertia i Dynamically allocate virtual inertia across multiple devices; Step 4: Based on the control structure and hardware constraints of the GFM device, modify the mathematical models and constraints of the dynamic virtual impedance module and the composite virtual inertia module to obtain parameter expressions and boundary constraints suitable for network-type devices. Step 5: Design a damping observer to obtain the real-time damping value ζ. obs Furthermore, a damping-inertia adaptive coordinator module is added after the composite virtual inertia module, using the real-time observed damping value ζ. obs The upper limit of the virtual inertia is adjusted, and the Lyapunov energy function is used as a constraint to avoid system oscillation caused by inertia adjustment; as well as Step 6: Set the objective function based on frequency stability, economy and damping lower limit, and set a three-layer emergency response mechanism to avoid the conflict between the two-layer control of the dynamic virtual impedance module and the composite virtual inertia module.

2. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 1, characterized in that, In step 2, based on the low, medium, and high control frequency bands, the expression model of the dynamic virtual impedance is modified as follows: Z v (s)= W L (f) ·Z low (s)+[1- W L (f)- W H (f)] ·Z mid (s)+ W H (f)·Z high (s); Among them, Z low (s), Z mid (s) and Z high (s) represent the impedances for the low, medium, and high frequency bands, respectively; W L (f) and W H (f) are the continuously adjustable frequency domain weighting coefficients for low and high frequencies, respectively, as expressed below: ; Where k∈(0,1), it represents the transition speed controlling the change of the weight coefficient; f L and f H These represent the center frequencies for low-frequency and high-frequency weight switching, respectively; The system's harmonic components and resonant frequencies are extracted in real time using a Fast Fourier Transform module, and the impedance parameters of each frequency band are dynamically adjusted. The proportional-differential coefficient K... p (f) and K d (f): ； Where |H(k)| is the amplitude of the k-th harmonic obtained from the fast Fourier transform analysis; W(f k H(f) is the frequency weighting function for the k-th harmonic; α and β are normalization coefficients, determined by the Lyapunov stability criterion; H(f) represents the system response amplitude under a frequency perturbation of f. Based on the dynamically adjusted proportional-differential coefficient K p (f) and K d (f) Dynamically update the impedance Z of each frequency band low (s), Z mid (s) and Z high (s): ； Among them, T low Z represents the time constant used to simulate physical inertia. low (s) is used to provide inertial support; For virtual resistance, K h Z represents the impedance gain coefficient in the high-frequency band; s is the Laplace operator; Z mid (s) is used to optimize damping; ω high =2π×10rad / s;Z high (s) is used to actively enhance high-frequency impedance in order to absorb resonant energy.

3. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 2, characterized in that, In step 4, parameter coupling constraints are set for the dynamic virtual impedance module as an auxiliary standard to assist in adjusting the virtual impedance and improve its adaptability. Specifically, this includes: 1) Frequency-impedance mapping Through exponential function Mapping the frequency deviation Δf to the proportional-differential coefficient K p (f) and K d (f), and utilize the updated K p (f) and K d (f) Dynamically adjust the impedance amplitude to suppress subsynchronous / supersynchronous oscillations; 2) Power-impedance feedback Impedance correction is generated using power deviation (ΔP, ΔQ). And dynamically adjust the virtual impedance based on the impedance correction amount: ； Where γ is the power sensitivity coefficient, and ΔP and ΔQ represent the active power deviation and reactive power deviation of the system, respectively.

4. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 1, characterized in that, In step 4, for the GFM device, the dynamic virtual impedance expression model is updated by combining the transfer function of the grid-type converter to obtain the updated virtual impedance, as shown below: ； Among them, G droop (s) and G VSG (s) are the transfer functions for droop control and VSG control, respectively, and are specifically expressed as follows: ； Among them, D p T is the active droop coefficient; droop T is the time constant of the droop response, used to smooth power distribution; vir D is the virtual inertial time constant. vir ω is the virtual damping coefficient. n This is the rated angular frequency; In conjunction with the hardware amplitude limitations of GFM devices, including the switching frequency and heat dissipation limitations of power electronic devices, the dynamic virtual impedance expression model is constrained to satisfy: ； Among them, V dc I is the DC bus voltage; rms P is the converter-side current measured in real time. sw,max R is the maximum power of the switch; on k is the on-resistance of the device; sw The loss factor, which is related to the device type, is calibrated through loss testing; f sw This is the switching frequency of the device.

5. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to any one of claims 1-4, characterized in that, In step 3, the constructed composite virtual inertia module uses the dynamic inertia gain coefficient K of each GFM device. v As input, and dynamically adjust the virtual inertia weight allocation of multiple devices to achieve second-level precise support for power grid frequency; Among them, the dynamic inertia gain coefficient K of each GFM device v K is used to provide real-time feedback on its adjustable inertia capacity, providing a basis for decision-making regarding inertia allocation strategies. v The expression model is as follows: ； Where Δf represents the frequency deviation, and α·Δf is used for the direct response frequency deviation; the coefficient α = (2H sys ) / Δf max H sys Let Δf be the total inertia required by the system. max This represents the maximum allowable frequency deviation of the system. Used to suppress gain abrupt changes caused by high-frequency disturbances; β represents the control damping strength, β = 1 / (2πf c ) 2 ,f c The cutoff frequency; Among them, γ·SOC 0.5 This represents the SOC status feedback item, which limits the over-discharge of energy storage through SOC feedback.

6. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 5, characterized in that, In step 4, the inertia distribution of each GFM device is adjusted to minimize system frequency deviation and device losses, and this is done through weight ω. i The upper limit of the inertia contribution of each device is constrained as follows: ； Among them, K v,i Describe the dynamic inertia gain coefficient of device i; For K v,i The lower limit; For the n GFM devices in the system, the inertia weight allocation is as follows: ； Wherein: H n H is the total inertia required by the system. v,i The maximum virtual inertia capacity of device i, and the weights ω of each device. i Adjust as follows: ； Wherein: S i (t) is the real-time state coefficient of device i, with a value range of [0,1], used to characterize the availability and health of the device.

7. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 6, characterized in that, In step 4, for network-type devices, a unique weighting factor is added based on the switching frequency margin to adjust the dynamic inertia gain coefficient K. v The following corrections are made: ； Among them, T sw T is the converter switching cycle margin. sw =1 / f sw f represents the limit of hardware response. sw The switching frequency; This is the maximum value allowed during the switching cycle; It is the switching frequency margin term, when the switching frequency f sw Approaching the upper limit, i.e., f sw Approaching At that time, T sw Approaching At this point, K is forcibly reduced. v To avoid the switching losses reaching their limit.

8. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 5, characterized in that, In step 4, when multiple GFM devices are connected in parallel, the weight ω for the inertia allocation of the GFM devices is determined. i Make the following corrections: ； in, The work angle penalty term; Δθ i κ is the power angle difference between device i and the typical reference node; κ is the penalty coefficient used to control the weight decay rate. in, As an economic adjustment factor, C i (K v,i Let be the loss function of device i.

9. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 1, characterized in that, In step 5, a damping observer is first designed to obtain the real-time observed damping value ζ. obs : ； Where: A1 and A2 are the amplitudes of adjacent oscillations, obtained through the time-domain envelope; τ ζ Here is the filter constant; Then, a damping-inertia adaptive coordinator module is added after the composite virtual inertia module to monitor the damping value ζ in real time. obs This is used to adjust the upper limit of the virtual inertia, achieving dynamic parameter fitting. The final adjusted virtual inertia output is: ； Where, ζ min This indicates the minimum allowable damping value of the system; the output range of tanh is always between [-1, 1]. If ζ obs >>ζ min Then tanh(·)≈1, allowing the maximum virtual inertia output; If ζ obs <<ζ min If tanh(·)≈0, then inertia regulation is forcibly turned off; The Lyapunov energy function is used as a constraint to ensure that the system remains in a stable state during parameter adjustment. ； The stability criterion requires that the time derivative of the energy function is non-positive, that is: ； Where α and β are normalization coefficients.

10. The method for broadband oscillation suppression and frequency support of GFM devices based on dual time scales according to claim 1, characterized in that, In step 6, the objective function is set based on frequency stability, economy, and damping lower limit, and a three-layer emergency response mechanism is established to avoid conflicts between the two-layer control of the dynamic virtual impedance module and the composite virtual inertia module, including: Taking into account both frequency stability and economic efficiency, and incorporating dynamic damping ratio constraints, the objective function is set as follows: ； in: To optimize frequency stability, the system is ensured to quickly return to a stable frequency by minimizing the square integral of the frequency deviation. Considering economic optimization, the goal is to extend equipment life by minimizing the total cost of equipment wear and tear; Considering the damping ratio constraint of the equipment, limit the range of the damping ratio to prevent oscillation; Where ρ = 10 λ represents the weight based on the higher damping ratio constraint; λ and η are the weighting coefficients: When λ >> η, the focus is on frequency stability, which is suitable for frequency regulation in emergency power grid conditions; When λ << η, the focus is on economy, which is suitable for steady-state operation; The three-tiered emergency response mechanism is defined as follows: 1) Damping priority layer In ζ obs <ζ min When Δf > 0.5Hz, forced priority is applied: ； Among them, H v,i This represents the maximum virtual inertia capacity of device i. Represents the reference virtual inertia of device i; and These represent the increased virtual resistance and decreased virtual inertia after adjustment, respectively. 2) Frequency Priority Layer When the frequency deviation Δf satisfies: Δf > 0.5Hz and ζ obs ≥ζ min hour: ； in, This represents the increase in virtual inertia after adjustment; 3) Complex Crisis Layer When the frequency deviation Δf satisfies Δf > 0.5Hz, ζ obs <ζ min And when the damping priority layer and frequency priority layer actions are not triggered: ； in, and These represent the upper limits of dynamic impedance and virtual inertia under a compound crisis, respectively; f res ΔZ represents the resonant frequency of the injected impedance; ΔZ represents the amplitude of the impedance fluctuation; τ represents the time constant of the exponential decay of the inertia.

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