Virtual synchronous machine grid-connected control method based on fractional order lead filter correction

Abstract

The application discloses a virtual synchronous machine grid-connected control method based on fractional order lead filter correction, which is obtained by reconstructing a traditional virtual synchronous machine rotor motion equation, namely, replacing an integer order virtual inertia link with a fractional order virtual inertia link, and additionally adding two control degrees of freedom, namely, active power feedforward compensation parameters and forward channel proportional correction parameters, to form the virtual synchronous machine grid-connected control method based on the fractional order lead filter correction, so as to improve the response performance of active power and output frequency of the virtual synchronous machine grid-connected system, effectively solve the dynamic oscillation problem of the active power and output frequency of the traditional virtual synchronous machine grid-connected system under internal active power instructions, external grid frequency and other disturbances, shorten the adjustment time of the active power and output frequency and reduce the overshoot of the active power, and be applicable to the field of virtual synchronous machine grid-connected control in power electronic technology.

Description

Technical Field

[0001] This invention relates to the field of virtual synchronous machine control technology, and in particular to a virtual synchronous machine grid-connected control method based on fractional-order lead filter correction, applicable to the field of virtual synchronous machine grid-connected control in power electronics technology. Background Technology

[0002] The rapid development of wind and solar energy, along with the large-scale grid connection of new energy-consuming equipment, is transforming the traditional power system into a new "dual-high" power system characterized by a high proportion of renewable energy and a high proportion of power electronic equipment. This poses a severe challenge to the safe and stable operation of the power grid. Against this backdrop, Virtual Synchronous Generators (VSGs), by introducing integer-order virtual inertia control and primary voltage regulation, can provide inertia and voltage support to the grid. However, the active power and output frequency of VSG-connected systems are prone to dynamic oscillations and overshoot under active power reference commands or grid frequency disturbances. Furthermore, the Fractional Order Virtual Synchronous Generator (FOVSG) replaces the integer-order virtual inertia control loop in the VSG with a fractional-order virtual inertia control loop. By adjusting the introduced fractional-order integral parameter, the dynamic oscillation of the grid-connected active power can be effectively suppressed. However, there is a problem that it is difficult to balance the grid-connected active power response performance and the inertia response performance. That is, it is necessary to weigh the suppression effect of grid-connected active power dynamic oscillation and output frequency overshoot / overshoot to compromise the value of the fractional-order integral parameter.

[0003] To address this, various studies have been conducted, such as the article titled "Virtual Synchronous Generator Control Technology for Fractional-Order Virtual Inertia of Grid-Connected Inverters," published in Control and Decision, Vol. 36, No. 2, 2021, pp. 463-468. This article replaces the integer-order virtual inertia control loop in the VSG with a fractional-order virtual inertia control loop to form an FOVSG. By adjusting the fractional-order integral parameter, it can effectively suppress the dynamic oscillation of the grid-connected active power and output frequency of the VSG. However, it has the disadvantages of being difficult to balance grid-connected active power response performance and inertia response performance, having overshoot in the grid-connected active power response, and having only one adjustable parameter.

[0004] The article, titled "Active Response Strategy for VSG Grid Connection Based on Active Fractional-Order Differential Correction," published in *Electric Power Automation Equipment*, Vol. 44, No. 2, 2024, pp. 204-210, proposes an optimized control strategy for the active response of VSG grid connection based on active fractional-order differential correction. This strategy achieves control performance comparable to FOVSG, effectively solving the problem of VSG grid connection struggling to maintain good dynamic and steady-state response performance under both active reference command and grid frequency disturbances. However, it suffers from drawbacks such as slow dynamic response speed, the inclusion of only one control parameter, and insufficient flexibility in parameter selection.

[0005] The article, titled “Fractional-order virtual synchronous generator”, YUY, GUAN YJ, KANG WF, et al., IEEE Transactions on Power Electronics, 2023, 38(6), 6874-6879, introduces a double fractional-order virtual inertia control loop into the FOVSG grid-connected control structure. This effectively eliminates the dynamic oscillation phenomenon of VSG grid-connected active power and output frequency under step disturbances such as active power command and grid frequency, and increases the system's control degree of freedom and the flexibility of control parameter selection. However, its ability to suppress VSG grid-connected active power and output frequency overshoot is still insufficient.

[0006] The article, titled "Improved Grid-Connected Strategy for VSG Based on Triple Fractional Inertia," published in *Electric Power Automation Equipment*, Vol. 45, No. 7, 2025, pp. 1833-189+224, proposes an improved grid-connected control strategy for VSG based on triple fractional virtual inertia. This strategy can effectively suppress the dynamic oscillation and overshoot of VSG grid-connected active power and output frequency under step disturbances such as active power reference command and grid frequency. It has the advantages of increasing the system's control degrees of freedom and the flexibility of control parameter selection. However, it has the disadvantages of high control structure complexity, parameter tuning dependence on experience and insufficient accuracy, and difficulty in digital implementation.

[0007] As can be seen from the above, the existing technology can provide some improvement ideas and technical support for suppressing the dynamic oscillation and overshoot of VSG grid-connected active power and output frequency under disturbances such as active power reference command and grid frequency. However, there is still much room for improvement in terms of control freedom, parameter flexibility and suppression effect. Specifically, the increased control freedom is limited, the parameter adjustment flexibility is insufficient, and the control effect of suppressing VSG grid-connected active power and output frequency overshoot still needs to be further enhanced. Summary of the Invention

[0008] To overcome the limitations of various technical solutions presented in the background art, this invention addresses the problems of insufficient dynamic oscillation suppression and large overshoot in the active power and output frequency of virtual synchronous machines under internal and external disturbances such as active power reference commands and grid frequency. It provides a virtual synchronous machine grid-connected control method based on fractional-order lead filter correction. This control method reconstructs the rotor motion equation of the traditional virtual synchronous machine by replacing the integer-order virtual inertia element with a fractional-order virtual inertia element and adding two additional control degrees of freedom: active power feedforward compensation parameters and forward channel proportional correction parameters. This constitutes a virtual synchronous machine grid-connected control method based on fractional-order lead filter correction, thereby improving the response performance of the active power and output frequency of the virtual synchronous machine. It effectively solves the dynamic oscillation problem of active power and output frequency in traditional virtual synchronous machine grid-connected systems under disturbances such as internal active power commands and external grid frequency. Furthermore, it has advantages such as shortening the settling time of active power and output frequency, reducing active power overshoot, providing more control degrees of freedom, more flexible control parameter selection, and easier parameter tuning.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for grid-connected control of a virtual synchronous machine based on fractional-order lead filter correction includes the following steps:

[0011] Step 1, Power Calculation Section: Sample the three-phase grid-connected current i of the virtual synchronous machine. a i b i c and three-phase output voltage u a u b u c The dq-axis components I of the three-phase grid-connected current, oriented based on the output phase angle θ of the virtual synchronizing machine, are obtained by single-synchronization rotating coordinate transformation. d I q and the dq component U of the three-phase output voltage d U q Then, through the power calculation stage, the grid-connected active power P of the virtual synchronous machine is obtained. e And grid-connected reactive power Q e ;

[0012] Step 2, the primary voltage regulation equation, is based on the grid-connected reactive power Q of the virtual synchronous machine obtained in Step 1. e The reactive power reference instruction Q of the virtual synchronous machine ref Primary voltage regulation coefficient k q Using the voltage reference command E0, the dq axis output voltage reference command E of the virtual synchronizer is obtained through a voltage adjustment equation. d E q ;

[0013] Step 3: Based on the rotor motion equation corrected by the fractional-order lead filter, the active power reference command P of the virtual synchronizer is used. ref Subtract the grid-connected active power P of the virtual synchronous machine obtained in step 1 e The power difference ΔP is obtained, and then the power difference ΔP is combined with the virtual inertia J, virtual damping D, rated angular frequency ω0, fractional order μ, and active power feedforward compensation parameter K of the virtual synchronous machine. d , and forward channel proportional correction parameter K p The angular frequency deviation Δω of the virtual synchronizer is obtained by applying the rotor motion equations corrected by a fractional-order lead filter.

[0014] Step 4, Output phase angle calculation and generation section: Add the rated angular frequency ω0 to the angular frequency deviation Δω of the virtual synchronizer obtained in step 3 to obtain the output angular frequency ω of the virtual synchronizer. Then, perform an integration operation on the output angular frequency ω to obtain the output phase angle θ of the virtual synchronizer.

[0015] Step 5: First, based on the output phase angle θ of the virtual synchronizer obtained in Step 4, and the dq axis output voltage reference command E of the virtual synchronizer obtained in Step 2... d E q The three-phase bridge arm voltage modulation signal E of the virtual synchronous machine is obtained through inverse transformation of the single synchronous rotating coordinates. a E b E c Then, the three-phase bridge arm voltage modulation signal E a E b E c The SVPWM modulation stage generates the drive signals for the switching transistors of the virtual synchronous machine inverter bridge.

[0016] Furthermore, the grid-connected active power P in step 1 e The calculation formula used is:

[0017] P e =1.5(U d I d +U q I q ),

[0018] Grid-connected reactive power Q e The calculation formula used is:

[0019] Q e =1.5(U q I d -U d I q ).

[0020] Furthermore, the output voltage reference command E in step 2 dThe calculation formula used is:

[0021] E d =E0+(Q ref -Q e )k q ,

[0022] Output voltage reference command E q The calculation formula used is:

[0023] E q =0.

[0024] Furthermore, the formula used to calculate the power difference ΔP in step 3 is as follows:

[0025] ΔP=P ref -P e ,

[0026] The equation used for the angular frequency deviation Δω is:

[0027]

[0028] In the formula, s is the Laplace operator.

[0029] Furthermore, the formula for calculating the output angular frequency ω in step 4 is as follows:

[0030] ω = Δω + ω0,

[0031] The formula for calculating the output phase angle θ is:

[0032]

[0033] In the formula, s is the Laplace operator.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention discloses a virtual synchronous machine grid-connected control method based on fractional-order lead filter correction. This control method reconstructs the rotor motion equations of the traditional virtual synchronous machine by replacing integer-order virtual inertia elements with fractional-order virtual inertia elements, and adds two additional control degrees of freedom: active power feedforward compensation parameters and forward channel proportional correction parameters. This constitutes a virtual synchronous machine grid-connected control method based on fractional-order lead filter correction, improving the response performance of the virtual synchronous machine's active power and output frequency. It effectively solves the dynamic oscillation problem of active power and output frequency in traditional virtual synchronous machine grid-connected systems under disturbances such as internal active power reference commands and external grid frequencies. Furthermore, it has advantages such as shortened active power and output frequency settling time, reduced active power overshoot, more control degrees of freedom, more flexible control parameter selection, and easier parameter tuning. It is applicable to the field of virtual synchronous machine grid-connected control in power electronics technology. Attached Figure Description

[0036] Figure 1 This is a diagram of the virtual synchronous machine grid-connected control structure according to an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram illustrating the calculation of the rotor motion equation of the virtual synchronous machine according to an embodiment of the present invention.

[0038] Figure 3 This is an equivalent control structure diagram of the virtual synchronous machine grid-connected active power closed loop according to an embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of coordinate transformation and modulation according to an embodiment of the present invention.

[0040] Figure 5 This is a Bode plot comparing the virtual synchronizer before and after adopting this invention.

[0041] Figure 6 This is a comparison of the simulation waveforms of the virtual synchronizer before and after adopting this invention.

[0042] Figure 7 This is a comparison of experimental waveforms before and after the virtual synchronizer was implemented using this invention. Detailed Implementation

[0043] The following detailed embodiments will be further described in conjunction with the above-mentioned figures, as follows:

[0044] Please see Figure 1 The present invention proposes a virtual synchronous machine grid-connected control method based on fractional-order lead filter correction, comprising the following steps:

[0045] Step 1, Power Calculation Section: Sample the three-phase grid-connected current i of the virtual synchronous machine. a i b ic and three-phase output voltage u a u b u c The dq-axis components I of the three-phase grid-connected current, oriented based on the output phase angle θ of the virtual synchronizing machine, are obtained by single-synchronization rotating coordinate transformation. d I q and the dq-axis component U of the three-phase output voltage d U q Then, the grid-connected active power P of the virtual synchronous machine is obtained through the power calculation equation. e And grid-connected reactive power Q e ;

[0046] Among them, grid-connected active power P e The calculation formula used is:

[0047] P e =1.5(U d I d +U q I q ),

[0048] Grid-connected reactive power Q e The calculation formula used is:

[0049] Q e =1.5(U q I d -U d I q ).

[0050] Step 2, the primary voltage regulation equation, is based on the grid-connected reactive power Q of the virtual synchronous machine obtained in Step 1. e The reactive power reference instruction Q of the virtual synchronous machine ref Primary voltage regulation coefficient k q The voltage reference command E0 is used to obtain the dq axis output voltage reference command E of the virtual synchronizer through a voltage adjustment equation. d E q ;

[0051] Among them, the output voltage reference command E d The calculation formula used is:

[0052] E d =E0+(Q ref -Q e )k q ,

[0053] Output voltage reference command E q The calculation formula used is:

[0054] E q =0.

[0055] Step 3, the rotor motion equation based on fractional-order lead filter correction, such as... Figure 2 As shown, the active power reference command P of the virtual synchronizer is... ref Subtract the grid-connected active power P obtained in step 1 e The power difference ΔP is obtained, and then the power difference ΔP is combined with the virtual inertia J, virtual damping D, rated angular frequency ω0, fractional order μ, and active power feedforward compensation parameter K. d , and forward channel proportional correction parameter K p The angular frequency deviation Δω of the virtual synchronizer is obtained by applying the rotor motion equations corrected by a fractional-order lead filter.

[0056] That is, the formula used to calculate the power difference ΔP is:

[0057] ΔP=P ref -P e ,

[0058] The equation used for the angular frequency deviation Δω is:

[0059]

[0060] In the formula, s is the Laplace operator.

[0061] Step 4, Output phase angle calculation and generation section: Add the rated angular frequency ω0 to the angular frequency deviation Δω of the virtual synchronizer obtained in step 3 to obtain the output angular frequency ω of the virtual synchronizer. Then, perform an integration operation on the output angular frequency ω to obtain the output phase angle θ of the virtual synchronizer.

[0062] The formula for calculating the output angular frequency ω is as follows:

[0063] ω = Δω + ω0,

[0064] The formula for calculating the output phase angle θ is:

[0065]

[0066] In the formula, s is the Laplace operator.

[0067] Combination Figure 1 Based on the above calculations, the equivalent control structure of the grid-connected active power closed loop of the virtual synchronous machine based on fractional-order lead filter correction described in this invention can be obtained as follows: Figure 3 As shown in (a), and for Figure 3 (a) By performing an equivalent transformation, we can obtain Figure 3 (b) Figure 3 In this context, δ represents the power factor angle; K represents the synchronization voltage coefficient.

[0068] The formula used to calculate the power factor angle δ is as follows:

[0069]

[0070] The formula used to calculate the synchronization voltage coefficient K is:

[0071]

[0072] In the formula, ω g U is the grid angular frequency. g Let X be the grid voltage amplitude, E be the output voltage amplitude, X be the line equivalent inductive reactance, and s be the Laplace operator.

[0073] Step 5, as follows Figure 4 As shown, first, based on the output phase angle θ of the virtual synchronizer obtained in step 4, and the dq axis output voltage reference command E of the virtual synchronizer obtained in step 2... d E q The three-phase bridge arm voltage modulation signal E of the virtual synchronous machine is obtained through inverse transformation of the single synchronous rotating coordinates. a E b E c Then, the three-phase bridge arm voltage modulation signal E a E b E c The SVPWM modulation stage generates the drive signals for the switching transistors of the virtual synchronous machine inverter bridge.

[0074] Example

[0075] To verify the control effect of the proposed virtual synchronous machine grid-connected control method based on fractional-order lead filter correction, the proposed virtual synchronous machine grid-connected control method based on fractional-order lead filter correction (hereinafter referred to as FOLFC-VSG) is compared with the existing traditional virtual synchronous machine (hereinafter referred to as VSG) grid-connected control method (the VSG grid-connected control method is mentioned in the background art as "Active Response Strategy of Energy Storage VSG Grid-Connected Based on Active Fractional-Order Differential Correction", "Electric Power Automation Equipment", Vol. 44, No. 2, 2024, pp. 204-210) and the existing fractional-order virtual synchronous machine (hereinafter referred to as FOVSG) grid-connected control method (the FOVSG grid-connected control method is mentioned in the background art as "Virtual Synchronous Generator Control Technology of Fractional-Order Virtual Inertia of Grid-Connected Inverter", "Control and Decision", Vol. 36, No. 2, pp. 463-468, 2021). The three grid-connected control methods are compared through simulation and experiments, mainly focusing on their performance in responding to the active power reference command P. ref and grid frequency f g Grid-connected active power P under step disturbance conditions e And the dynamic response performance at the output frequency f. Specifically:

[0076] First, the relevant parameters are set. In this embodiment, the relevant parameter settings in the FOLFC-VSG grid-connected control method of the present invention are as follows:

[0077] The virtual synchronous machine has a rated capacity of 100kVA and an active power reference command P. ref It has a power output of 20kW, a rated angular frequency ω0 of 314.16 rad / s, and a virtual inertia J of 6 kg·m. 2 The virtual damping D is 50.66 J / rad, and the grid voltage amplitude U g The voltage is 311V, and the primary voltage regulation coefficient is k. q 1.4×10 -4 V / var, the output voltage amplitude E of the virtual synchronizer is 311V, the equivalent inductive reactance X of the line is 0.1Ω, that is, the synchronization voltage coefficient K = 1.5U g E / X = 1450815. It is worth noting that if the forward channel proportional correction parameter K in the FOLFC-VSG is set... p =1. Active power feedforward compensation parameter K d If the ratio of the forward channel to the given value is 0 and the fractional order μ = 1, then FOLFC-VSG can be equivalent to VSG, indicating that VSG is only a special case of FOLFC-VSG; if the forward channel proportional correction parameter K in FOLFC-VSG is set... p =1 and active power feedforward compensation parameter K d If = 0, then FOLFC-VSG is equivalent to FOVSG, which shows that FOVSG is only a special case of FOLFC-VSG. Meanwhile, combining... Figure 3 Through a series of formula derivations, the active power reference command P of the existing VSG grid-connected system can be obtained. ref To grid-connected active power P e The closed-loop transfer function is The expression for the damping ratio of the VSG grid-connected active power closed-loop control system can be derived from G(s) as follows: Substituting the above parameters into the expression, we get ξ = 0.152 << 1, meaning the VSG grid-connected active power closed-loop control system is an underdamped system. Therefore, the VSG's grid-connected active power P e With output frequency f in active reference command P ref and grid frequency f g Under step disturbance conditions, dynamic oscillations and overshoot will inevitably occur. Similarly, the active power reference command P of the existing FOVSG grid-connected system... ref To grid-connected active power P e The closed-loop transfer function is Substitute the above parameters into G1(s), and set the fractional order μ in G1(s) to 0.6 to ensure the grid-connected active power P of FOVSG. eWith output frequency f in active reference command P ref and grid frequency f g No dynamic oscillation phenomenon occurs under step disturbance conditions.

[0078] In this embodiment, the active power feedforward compensation parameter K will be optimized. d With forward channel proportional correction parameter K p The value of [value] is selected to further optimize the grid-connected active power P of FOLFC-VSG. e With output frequency f in active reference command P ref and grid frequency f g Dynamic response performance under a step disturbance. Similarly, according to Figure 3 Through a series of formula derivations, the active power reference command P of the FOLFC-VSG grid-connected system can be obtained. ref To grid-connected active power P e The closed-loop transfer function is Therefore, the grid-connected active power dynamic response performance of VSG, FOVSG, and FOLFC-VSG can be directly compared and analyzed using the closed-loop transfer functions G(s), G1(s), and G2(s). To further simplify the theoretical analysis, the fractional order of FOLFC-VSG is set to μ = 0.6, and the forward channel proportional correction parameter K is set to... p =1.005 and active power feedforward compensation parameter K d =5.3×10 -5 The fractional order in FOVSG is μ = 0.6. Substituting the above parameters into G2(s), G1(s), and G(s) respectively, we can obtain the active power reference command step disturbance ΔP of the grid-connected active power closed-loop control system of FOLFC-VSG, FOVSG, and VSG. ref To the grid-connected active power response ΔP e (ΔP e / ΔP ref For a comparison of the Bode plot, see [link / reference]. Figure 5 (a). Similarly, the grid angular frequency step disturbance Δω of the grid-connected active power closed-loop control system of FOLFC-VSG, FOVSG and VSG can be obtained respectively. g To the grid-connected active power response ΔP e (ΔP e / Δω g Active reference command step disturbance ΔP ref Output angular frequency response Δω(Δω / ΔP) ref ) and the step disturbance of the power grid angular frequency Δω g Output angular frequency response Δω(Δω / Δω) g For a comparison of the Bode plot, see [link / reference]. Figure 5 (b) Figure 5 (c) and Figure 5 (d). Among them, Figure 5 In this context, VSG represents the existing traditional VSG grid-connected control method, meaning the curve indicated corresponds to the Bode plot of the traditional VSG grid-connected control method before the adoption of this invention; FOVSG represents the existing FOVSG grid-connected control method, meaning the curve indicated corresponds to the Bode plot of the existing FOVSG grid-connected control method before the adoption of this invention; and FOLFC-VSG represents the FOLFC-VSG grid-connected control method proposed in this invention, meaning the curve indicated corresponds to the FOLFC-VSG grid-connected control method proposed in this invention.

[0079] according to Figure 5 It can be seen that: 1. Both existing VSG and existing FOVSG grid-connected systems exhibit significant resonance peaks before the cutoff frequency. This phenomenon indicates that the active power P of existing VSG and existing FOVSG grid-connected systems is... e With the output angular frequency f in the active reference command P ref and the angular frequency ω of the power grid g Dynamic oscillations or overshoot will occur under step disturbance conditions; secondly, the ΔP of the grid-connected system of the FOLFC-VSG proposed in this invention... e / ΔP ref ΔP e / Δω g , Δω / Δω g The absence of significant resonance peaks and the large bandwidth before the cutoff frequency indicate that the grid-connected active power P of the FOLFC-VSG is... e In the active reference instruction P ref and the angular frequency ω of the power grid g There is no dynamic oscillation problem under step disturbance conditions, and the output angular frequency f is at the grid angular frequency ω. g There is no dynamic oscillation problem under step disturbance conditions; 3. The ΔP of the FOLFC-VSG grid-connected system proposed in this invention e / ΔP ref ΔP e / Δω g , Δω / Δω g Compared to existing VSGs and existing FOVSGs, it has a smaller resonance peak. This phenomenon indicates that the grid-connected active power P corresponding to the FOLFC-VSG is smaller. e In the active reference instruction P ref and the angular frequency ω of the power grid g It exhibits smaller grid-connected active power oscillations and overshoot under step disturbance conditions, and its output angular frequency f is within the grid angular frequency ω. gIt exhibits a lower output frequency response overshoot amplitude under step disturbance conditions. Notably, compared to VSG and FOVSG, FOLFC-VSG also offers advantages such as more control parameters and more flexible parameter selection. For example, by selecting appropriate fractional order μ and active power feedforward compensation parameter K... d With forward channel proportional correction parameter K p The value of P is selected to flexibly optimize the grid-connected active power P of FOLFC-VSG. e The dynamic response performance with respect to the output angular frequency f will not be listed in detail due to space limitations.

[0080] Based on the above parameter settings, simulation and experimental comparison tests were conducted, as follows:

[0081] The simulation and experimental test conditions were set as follows: at the initial moment, the virtual synchronous machine stably outputs 20kW of grid-connected active power. e , grid frequency f g Maintaining a constant 50Hz, the active power reference command P is available at 4.0s. ref The power grid frequency f jumps from 20kW to 60kW in 7.0s. g The frequency jumps from 50Hz to 49.95Hz.

[0082] Based on the above working conditions, the following results were obtained: Figure 6 and Figure 7 The simulation and experimental test comparison chart shown below, in which Figure 6 and Figure 7 In this context, VSG represents the existing traditional VSG grid-connected control method, FOVSG represents the existing FOVSG grid-connected control method, and FOLFC-VSG represents the FOLFC-VSG grid-connected control method proposed in this invention. Specifically, the curve pointed to by VSG is the test waveform diagram before the application of this invention, specifically the dynamic response test waveform diagram of the existing traditional VSG grid-connected control method; the curve pointed to by FOVSG is the test waveform diagram before the application of this invention, specifically the dynamic response test waveform diagram of the existing FOVSG grid-connected control method; and the curve pointed to by FOLFC-VSG is the test waveform diagram after the application of this invention, specifically the test waveform diagram of the FOLFC-VSG grid-connected control method proposed in this invention.

[0083] according to Figure 6 (a) It can be observed that: 1. The grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention is... e There is no dynamic oscillation with the output frequency f, and the corresponding grid-connected active power P of the VSG is already available. e Both the output frequency f and the FOVSG exhibit significant dynamic oscillations and overshoot. Although existing FOVSGs have achieved grid-connected active power P... e There is some improvement in oscillation suppression with respect to the output frequency f, but its grid-connected active power P eBoth the output frequency f and the output frequency f still exhibit significant overshoot; secondly, the grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention... e The power overshoot is 0.32%, which is less than the 40.97% corresponding to the existing VSG and the 8.3% corresponding to the existing FOVSG. Furthermore, the grid-connected active power P corresponding to the FOLFC-VSG is... e The time required to reach steady state is 0.04s, which is less than the 0.94s required by the existing VSG and the 0.14s required by the existing FOVSG. Therefore, the FOLFC-VSG proposed in this invention, compared with the existing VSG and FOVSG, achieves better performance under the active power reference command P. ref During the jump from 20kW to 60kW, the grid-connected active power P e Both the output frequency f and the output frequency f exhibit no dynamic oscillation and have a smaller P. e Overshoot and shorter grid-connected active power P e Adjust the time.

[0084] And according to Figure 6 (b) It can be observed that: 1. The grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention e With no dynamic oscillation or overshoot at the output frequency f, the corresponding grid-connected active power P of the VSG is already available. e Both the output frequency f and the FOVSG exhibit significant dynamic oscillations and overshoot. Although existing FOVSGs have achieved grid-connected active power P... e While there has been some improvement in output frequency oscillation suppression, its grid-connected active power P e Both the output frequency f and the output frequency f exhibit significant overshoot; secondly, the grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention... e The overshoot is 0.42%, which is less than the 19.29% of the existing VSG and the 5.74% of the existing FOVSG. Furthermore, the time required for the output frequency f of the FOLFC-VSG to reach steady state is 0.056s, which is less than the 1.05s of the existing VSG and the 0.14s of the existing FOVSG. Therefore, compared to existing VSGs and FOVSGs, the FOLFC-VSG proposed in this invention achieves better performance at the grid frequency f. g The grid-connected active power P during the jump from 50Hz to 49.95Hz e Both the output frequency f and the output frequency f exhibit no dynamic oscillation or overshoot, and the output frequency f has a shorter settling time.

[0085] according to Figure 7 (a) It can be found that: 1. The grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention is... e There is no dynamic oscillation with the output frequency f, and the corresponding grid-connected active power P of the VSG is already available. e There is significant dynamic oscillation and power overshoot with respect to the output frequency f. The existing grid-connected active power P corresponding to FOVSG is... eThere is a significant overshoot with respect to the output frequency f; secondly, the grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention... e The power overshoot is 0.34%, which is less than the 41.2% corresponding to the existing VSG and the 8.9% corresponding to the existing FOVSG. Furthermore, the grid-connected active power P corresponding to the FOLFC-VSG is... e The time required to reach steady state is 0.05s, which is less than the 0.97s required by the existing VSG and the 0.15s required by the existing FOVSG. Therefore, the FOLFC-VSG proposed in this invention, compared to the existing VSG and FOVSG, has a faster active power reference command P... ref During the jump from 20kW to 60kW, the grid-connected active power P e Both the output frequency f and the output frequency f exhibit no dynamic oscillation and have a smaller P. e Overshoot and shorter grid-connected active power P e Adjust the time.

[0086] And according to Figure 7 (b) It can be found that: 1. The grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention e There is no dynamic oscillation or overshoot with the output frequency f, and the corresponding grid-connected active power P of the VSG is already available. e Both the output frequency f and the FOVSG exhibit significant dynamic oscillations and overshoot. While existing FOVSGs have improved oscillation suppression, their corresponding grid-connected active power P... e Both the output frequency f and the output frequency f exhibit significant overshoot; secondly, the grid-connected active power P corresponding to the FOLFC-VSG proposed in this invention... e The overshoot is 0.53%, which is less than the 20.1% of the existing VSG and 5.9% of the existing FOVSG. Furthermore, the time required for the output frequency f of the FOLFC-VSG to reach steady state is 0.06s, which is less than the 1.07s of the existing VSG and 0.15s of the existing FOVSG. Therefore, it can be seen that the FOLFC-VSG proposed in this invention, compared to existing VSGs and FOVSGs, achieves better performance at the grid frequency f. g The grid-connected active power P during the jump from 50Hz to 49.95Hz e Both the output frequency f and the output frequency f exhibit no dynamic oscillation or overshoot, and the output frequency f has a shorter settling time.

[0087] Depend on Figure 7 (a) and Figure 6 As can be seen from the comparison of the results in (a), in this embodiment... Figure 7 (a) Experimental test results and Figure 6 (a) The simulation test results show a one-to-one correspondence, and both results fully demonstrate that, compared with existing VSGs and existing FOVSGs, the FOLFC-VSG proposed in this invention has a higher performance in active power reference command P. refGrid-connected active power P under step disturbance e Both the output frequency f and the output frequency f exhibit no dynamic oscillation and have a smaller P. e Overshoot and shorter settling time. Therefore, the FOLFC-VSG proposed in this invention has better control performance compared to existing VSGs and existing FOVSGs.

[0088] And again Figure 7 (b) and Figure 6 After comparing the results in (b), it is not difficult to see that in this embodiment... Figure 7 (b) Experimental test results and Figure 6 (b) The simulation test results show a one-to-one correspondence, and both results fully demonstrate that, compared with existing VSGs and existing FOVSGs, the FOLFC-VSG proposed in this invention has a better performance at the grid frequency f. g Grid-connected active power P under step disturbance e Both the output frequency f and the current exhibit no dynamic oscillation or overshoot, and the settling time is the shortest. Therefore, compared to existing VSGs and existing FOVSGs, the FOLFC-VSG proposed in this invention has better control performance.

[0089] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A virtual synchronous machine grid-connected control method based on fractional-order lead filter correction, characterized in that, Includes the following steps: Step 1, Power Calculation Section: Sample the three-phase grid-connected current i of the virtual synchronous machine. a i b i c and three-phase output voltage u a u b u c The dq-axis components I of the three-phase grid-connected current, oriented based on the output phase angle θ of the virtual synchronizing machine, are obtained by single-synchronization rotating coordinate transformation. d I q and the dq-axis component U of the three-phase output voltage d U q Then, the grid-connected active power P of the virtual synchronous machine is obtained through the power calculation equation. e And grid-connected reactive power Q e ; Step 2, the primary voltage regulation equation, is based on the grid-connected reactive power Q of the virtual synchronous machine obtained in Step 1. e The reactive power reference instruction Q of the virtual synchronous machine ref Primary voltage regulation coefficient k q The voltage reference command E0 is used to obtain the dq axis output voltage reference command E of the virtual synchronizer through a voltage adjustment equation. d E q ; Step 3: Based on the rotor motion equation corrected by the fractional-order lead filter, the active power reference command P of the virtual synchronizer is used. ref Subtract the grid-connected active power P of the virtual synchronous machine obtained in step 1 e The power difference ΔP is obtained, and then the power difference ΔP is combined with the virtual inertia J, virtual damping D, rated angular frequency ω0, fractional order μ, and active power feedforward compensation parameter K of the virtual synchronous machine. d , and forward channel proportional correction parameter K p The angular frequency deviation Δω of the virtual synchronizer is obtained by applying the rotor motion equations corrected by a fractional-order lead filter. Step 4, Output phase angle calculation and generation section: Add the rated angular frequency ω0 to the angular frequency deviation Δω of the virtual synchronizer obtained in step 3 to obtain the output angular frequency ω of the virtual synchronizer. Then, perform an integration operation on the output angular frequency ω to obtain the output phase angle θ of the virtual synchronizer. Step 5: First, based on the output phase angle θ of the virtual synchronizer obtained in Step 4, and the dq axis output voltage reference command E of the virtual synchronizer obtained in Step 2... d E q The three-phase bridge arm voltage modulation signal E of the virtual synchronous machine is obtained through inverse transformation of the single synchronous rotating coordinates. a E b E c Then, the three-phase bridge arm voltage modulation signal E a E b E c The SVPWM modulation stage generates the drive signals for the switching transistors of the virtual synchronous machine inverter bridge.

2. The virtual synchronous machine grid-connected control method based on fractional-order lead filter correction according to claim 1, characterized in that, The grid-connected active power P in step 1 e The calculation formula used is: P e =1.5(U d AND d +U q AND q ), Grid-connected reactive power Q e The calculation formula used is: Q e =1.5(U q I d -U d I q )。 3. The virtual synchronous machine grid-connected control method based on fractional-order lead filter correction according to claim 1, characterized in that, Output voltage reference command E in step 2 d The calculation formula used is: E d =(Q ref -Q e )k q +E0, Output voltage reference command E q The calculation formula used is: E q ＝0。 4. The virtual synchronous machine grid-connected control method based on fractional-order lead filter correction according to claim 1, characterized in that, The formula used to calculate the power difference ΔP in step 3 is: ΔP=P ref -P e , The formula for calculating the angular frequency deviation Δω is: In the formula, s is the Laplace operator.

5. The virtual synchronous machine grid-connected control method based on fractional-order lead filter correction according to claim 1, characterized in that, The formula used to calculate the output angular frequency ω in step 4 is: ω = Δω + ω0, The formula for calculating the output phase angle θ is: In the formula, s is the Laplace operator.

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