Fractional order virtual synchronous machine control method based on active fractional order feedforward

Abstract

The invention discloses a fractional order virtual synchronous machine control method based on active fractional order feedforward, and the method comprises the steps: enabling an active deviation to pass through a fractional order low-pass filtering link containing a feedforward compensation coefficient, a virtual inertia coefficient and a virtual damping coefficient, and then carrying out the feedforward of the active deviation to a grid-connected active closed-loop control loop of a fractional order virtual synchronous machine; by adjusting a feedforward compensation coefficient and a fractional order low-pass filtering coefficient, the dynamic response performance of the grid-connected active power and output frequency of the fractional order virtual synchronous machine under the disturbance of an active power instruction, a power grid frequency and the like is optimized, and the problems of dynamic oscillation and overshoot existing in the grid-connected active power and output frequency of the fractional order virtual synchronous machine can be effectively solved. The method has the advantages that more control parameters are provided, parameter selection is more flexible, the grid-connected active response speed can be increased, the response overshoot amplitude of the output frequency and the frequency change rate of the output frequency can be reduced, and the method can be applied to the field of fractional order virtual synchronous machine grid-connected control in the power electronic technology.

Description

Technical Field

[0001] This invention relates to the field of virtual synchronous machine control technology, and in particular to a fractional-order virtual synchronous machine control method based on active fractional-order feedforward. It is applicable to the field of grid-connected control of fractional-order virtual synchronous machines in power electronics technology, as well as the field of microgrid integration into distribution networks containing such fractional-order virtual synchronous machines. Background Technology

[0002] Virtual Synchronous Generators (VSGs) can provide a certain amount of inertia and voltage support to the power grid by simulating the rotor motion equations and primary voltage regulation equations of synchronous generators. However, the grid-connected active power and output frequency of VSGs are prone to dynamic oscillations under disturbances such as active power commands and grid frequency. Furthermore, Fractional Order VSGs (FOVSGs) introduce fractional-order virtual inertia control into the rotor motion equations of the VSG. By optimizing and adjusting the introduced fractional-order control parameters, they can effectively suppress the dynamic oscillations of grid-connected active power and output frequency. However, their ability to suppress grid-connected active power and output frequency overshoot still needs further improvement.

[0003] To address this, various studies have been conducted, such as the article entitled "Active Response Strategy for FOVSG Grid Connection Based on Active Fractional-Order Differential Correction," published in "Electric Power Automation Equipment," Vol. 44, No. 02, 2024, pp. 204-210. This article proposes a strategy for suppressing active oscillations in FOVSG grid connection based on active fractional-order differential correction, which can effectively suppress the dynamic oscillations of active power and output frequency of energy storage VSG grid connection. However, it has the disadvantages of only one added control parameter, a limited range of parameter selection, and the need for further improvement in the control effect of eliminating overshoot of active power and output frequency of energy storage VSG grid connection.

[0004] The article titled “Fractional-order virtual inertia control and parameter tuning for energy-storage system in low-inertia power grid”, ZENG YK, YANG QF, LIN YJ, et al., Protection and Control of Modern Power Systems, 2024, 9(5), 70-83 (“Fractional-order virtual inertia control and parameter tuning for energy-storage system in low-inertia power grid”, Modern Power System Protection and Control, 2024, Vol. 9, No. 5, pp. 70-83) proposes a fractional-order virtual synchronous generator (FOVSG) control technology based on fractional-order virtual inertia. It can effectively suppress the dynamic oscillation of VSG grid-connected active power and output frequency. However, it has the disadvantages of limited ability to suppress VSG grid-connected active power and output frequency overshoot, only adding one control parameter, and insufficient flexibility in parameter selection.

[0005] The article, titled "Frequency stability enhancement of an islanded microgrid: Afractional-order virtual synchronous generator," by LONG B, LI XY, RODRIGUEZ J, et al., *International Journal of Electrical Power and Energy Systems*, 2023, 147, 108896, proposes a FOVSG control method based on model predictive control. This method can effectively suppress the dynamic oscillation of VSG output active power and output frequency under system load disturbance conditions. However, it has drawbacks such as high difficulty in parameter design, strong dependence on system parameters, and the addition of only one control parameter. Furthermore, it does not explain the applicability of FOVSG under grid-connected conditions.

[0006] The article, titled “Fractional-order virtual synchronous generator”, YU Y, GUAN YJ, KANG WF, et al., IEEE Transactions on Power Electronics, 2023, 38(6), 6874-6879 (“Fractional-order virtual synchronous generator”, IEEE Journal of Power Electronics, Vol. 38, No. 6, 2023, pp. 6874-6879), introduces a double fractional-order virtual inertia control loop into the rotor motion equation of the VSG. This can increase the number of control parameters of the grid-connected system and their adjustable range, and can also effectively solve the dynamic oscillation problem of the active power and output frequency of the VSG. However, its ability to suppress the overshoot of the active power and output frequency of the VSG still needs to be further enhanced.

[0007] As can be seen from the above, although the existing technology can effectively solve the dynamic oscillation problem of VSG grid-connected active power and output frequency under different disturbances, it has the disadvantages of limited number of added control parameters, insufficient flexibility in the selection of control parameters, high difficulty in parameter design, and the ability to suppress VSG grid-connected active power and output frequency overshoot still need to be further strengthened. Summary of the Invention

[0008] To overcome the limitations of existing technical solutions described in the background section, this invention addresses the technical problems of limited dynamic oscillation suppression capability and excessive overshoot in the grid-connected active power and output frequency of fractional-order virtual synchronous machines. It provides a control method for fractional-order virtual synchronous machines based on active power fractional-order feedforward. This control method optimizes the dynamic response performance of the grid-connected active power and output frequency of the fractional-order virtual synchronous machine under disturbances such as active power commands and grid frequency. It effectively solves the dynamic oscillation and overshoot problems in the grid-connected active power and output frequency of the fractional-order virtual synchronous machine, and has advantages such as more control parameters, more flexible parameter selection, improved grid-connected active power response speed, and reduced output frequency response overshoot amplitude and frequency change rate.

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

[0010] A control method for a fractional-order virtual synchronous machine based on active fractional-order feedforward includes the following steps:

[0011] Step 1, power calculation section: First, collect the output current i of the fractional-order virtual synchronous machine. a i b i c and output voltage u a u b u cThe dq component I of the output current oriented by the phase angle θ of the output phase angle based on the fractional-order virtual synchronous machine is obtained by single-synchronous rotating coordinate transformation. d I q and the dq component of the output voltage U d U q Then, through the power calculation stage, the grid-connected active power P of the fractional-order virtual synchronous machine is obtained. e And grid-connected reactive power Q e ;

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

[0013] Step 3: Calculate the active power fractional-order feedforward quantity, and input the active power command P from the fractional-order virtual synchronizer. ref Subtract the grid-connected active power P of the fractional-order virtual synchronous machine obtained in step 1. e The power difference ΔP between the two is obtained as the input of the active power fractional-order feedforward control. The power difference ΔP is then processed through a circuit containing the feedforward compensation coefficient k. a The feedforward quantity δ for active fractional-order feedforward control is obtained after fractional-order low-pass filtering of virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D, and fractional-order low-pass filter coefficient λ. a ;

[0014] Step 4, Fractional order rotor motion equation: Based on the power difference ΔP obtained in Step 3 and the virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D and fractional order coefficient μ of the fractional order virtual synchronizer, the angular frequency deviation Δω of the fractional order virtual synchronizer is obtained through the fractional order rotor motion equation.

[0015] Step 5: Output phase angle generation section. The fractional-order virtual synchronizer angular frequency deviation Δω obtained in Step 4 is added to the rated angular frequency ω0 to obtain the output angular frequency ω of the fractional-order virtual synchronizer. The output angular frequency ω is then integrated to obtain the phase δ of the fractional-order virtual synchronizer. The phase δ is then added to the feedforward amount δ obtained in Step 3. a The output phase angle θ of the fractional-order virtual synchronizer is obtained;

[0016] Step 6: First, based on the fractional-order virtual synchronizer output phase angle θ obtained in Step 5, and the fractional-order virtual synchronizer dq-axis output voltage command E obtained in Step 2... d E qThe three-phase voltage modulation signal E of the fractional-order virtual synchronous machine is obtained through inverse rotational coordinate transformation of a single synchronous machine. a E b E c Then, the three-phase voltage modulation signal E a E b E c The SVPWM modulation stage generates the drive signal for the fractional-order virtual synchronous machine switch.

[0017] Preferably, the grid-connected active power P in step 1 e The calculation equation used is:

[0018] P e =1.5(U d I d +U q I q ),

[0019] Grid-connected reactive power Q e The calculation equation used is:

[0020] Q e =1.5(U q I d -U d I q ).

[0021] Preferably, the output voltage command E in step 2 d The calculation equation used is:

[0022] E d =(Q ref -Q e )k q +E0,

[0023] Output voltage command E q The calculation equation used is:

[0024] E q =0.

[0025] Preferably, the formula used to calculate the input power difference ΔP of the active power fractional feedforward control in step 3 is:

[0026] ΔP=P ref -P e ,

[0027] Feedforward quantity δ of active fractional-order feedforward control a The calculation formula used is:

[0028]

[0029] In the formula, k ais the feedforward compensation coefficient, and s is the Laplace operator.

[0030] Preferably, the formula used to calculate the angular frequency deviation Δω in step 4 is:

[0031]

[0032] In the formula, s is the Laplace operator.

[0033] Preferably, the equation used to calculate the output angular frequency ω in step 5 is:

[0034] ω = Δω + ω0,

[0035] The equation used to calculate phase δ is:

[0036]

[0037] The formula for calculating the output phase angle θ is:

[0038] θ=δ+δ a .

[0039] In the formula, s is the Laplace operator.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] This invention discloses a fractional-order virtual synchronous machine control method based on active power fractional-order feedforward. This method utilizes the active power deviation, which is fed forward to the grid-connected active power closed-loop control loop of the fractional-order virtual synchronous machine after passing through a fractional-order low-pass filter containing feedforward compensation coefficients, virtual inertia coefficients, and virtual damping coefficients. By adjusting the feedforward compensation coefficients and fractional-order low-pass filter coefficients, the dynamic response performance of the grid-connected active power and output frequency of the fractional-order virtual synchronous machine under disturbances such as active power commands and grid frequency is optimized. This effectively solves the dynamic oscillation and overshoot problems of the grid-connected active power and output frequency of the fractional-order virtual synchronous machine. It has advantages such as more control parameters, more flexible parameter selection, improved grid-connected active power response speed, and reduced output frequency response overshoot amplitude and frequency change rate. It is applicable to the field of grid-connected control of fractional-order virtual synchronous machines in power electronics technology. Attached Figure Description

[0042] Figure 1 This is a control structure diagram of a fractional-order virtual synchronous machine according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of feedforward calculation based on active fractional-order feedforward control.

[0044] Figure 3 This is an equivalent control structure diagram of the grid-connected active power closed loop of a fractional-order virtual synchronous machine according to an embodiment of the present invention.

[0045] Figure 4 This is a schematic diagram of coordinate transformation and modulation according to an embodiment of the present invention.

[0046] Figure 5 This is a Bode plot comparing the virtual synchronizer before and after adopting this invention.

[0047] Figure 6 This is a comparison of the simulation waveforms of the virtual synchronizer before and after adopting this invention.

[0048] Figure 7 This is a comparison of experimental waveforms before and after the virtual synchronizer was implemented using this invention. Detailed Implementation

[0049] The following detailed embodiments will be further described in conjunction with the above-mentioned figures, as follows:

[0050] Please see Figure 1 The present invention proposes a fractional-order virtual synchronous machine control method based on active fractional-order feedforward, comprising the following steps:

[0051] Step 1, power calculation section: First, collect the output current i of the fractional-order virtual synchronous machine. a i b i c and output voltage u a u b u c The dq component I of the output current oriented by the phase angle θ of the output phase angle based on the fractional-order virtual synchronous machine is obtained by single-synchronous rotating coordinate transformation. d I q and the dq component of the output voltage U d U q Then, through the power calculation stage, the grid-connected active power P of the fractional-order virtual synchronous machine is obtained. e And grid-connected reactive power Q e ;

[0052] That is, the calculation equation used for the grid-connected active power Pe is:

[0053] P e =1.5(U d I d +U q I q ),

[0054] Grid-connected reactive power Q e The calculation formula used is:

[0055] Q e =1.5(U q I d -U d I q ).

[0056] Step 2, primary voltage regulation section, based on the fractional-order virtual synchronous machine grid-connected reactive power Q obtained in Step 1. e The reactive power instruction Q of the fractional-order virtual synchronizer ref Primary voltage regulation coefficient k q The voltage command E0, after passing through a voltage regulation control equation, yields the dq axis output voltage command E of the fractional-order virtual synchronizer. d E q ;

[0057] That is, the output voltage command E d The calculation equation used is:

[0058] E d =(Q ref -Q e )k q +E0,

[0059] Output voltage command E q The calculation equation used is:

[0060] E q =0.

[0061] Step 3, calculate the fractional active power feedforward, such as... Figure 2 As shown, the active power instruction P of the fractional-order virtual synchronizer is... ref Subtract the grid-connected active power P of the fractional-order virtual synchronous machine obtained in step 1. e The power difference ΔP between the two is obtained as the input of the active power fractional-order feedforward control. The power difference ΔP is then processed through a circuit containing the feedforward compensation coefficient k. a The feedforward quantity δ for active fractional-order feedforward control is obtained after fractional-order low-pass filtering of virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D, and fractional-order low-pass filter coefficient λ. a ;

[0062] That is, the formula for calculating the input power difference ΔP in the fractional-order feedforward control is:

[0063] ΔP=P ref -P e ,

[0064] Feedforward quantity δ of active fractional-order feedforward control a The calculation formula used is:

[0065]

[0066] In the formula, k a is the feedforward compensation coefficient, and s is the Laplace operator.

[0067] Step 4, Fractional order rotor motion equation: Based on the power difference ΔP obtained in Step 3 and the virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D and fractional order coefficient μ of the fractional order virtual synchronizer, the angular frequency deviation Δω of the fractional order virtual synchronizer is obtained through the fractional order rotor motion equation.

[0068] That is, the formula used to calculate the angular frequency deviation Δω is:

[0069]

[0070] In the formula, s is the Laplace operator.

[0071] Step 5: Output phase angle generation section. The fractional-order virtual synchronizer angular frequency deviation Δω obtained in Step 4 is added to the rated angular frequency ω0 to obtain the output angular frequency ω of the fractional-order virtual synchronizer. The output angular frequency ω is then integrated to obtain the phase δ of the fractional-order virtual synchronizer. The phase δ is then added to the feedforward amount δ obtained in Step 3. a The output phase angle θ of the fractional-order virtual synchronizer is obtained;

[0072] That is, the equation used to calculate the output angular frequency ω is:

[0073] ω = Δω + ω0,

[0074] The equation used to calculate phase δ is:

[0075]

[0076] The formula for calculating the output phase angle θ is:

[0077] θ=δ+δ a ,

[0078] In the formula, s is the Laplace operator.

[0079] according to Figure 1 The given grid-connected control structure, combined with the above calculation equations, can yield the following results: Figure 3 The diagram shows the equivalent control structure of the grid-connected active power closed loop of the fractional-order virtual synchronous machine. Figure 3 In this context, δ represents the phase of the fractional-order virtual synchronizer; K represents the synchronization voltage coefficient of the fractional-order virtual synchronizer.

[0080] That is, the equation used to calculate the phase δ is:

[0081]

[0082] The equation used to calculate the synchronization voltage coefficient K is:

[0083]

[0084] In the formula, U g ω represents the voltage amplitude of the power grid. g denoted as the grid angular frequency, E as the output voltage amplitude of the fractional-order virtual synchronous machine, X as the equivalent inductive reactance of the grid line, and s as the Laplace operator.

[0085] Step 6, as follows Figure 4 As shown, first, based on the fractional-order virtual synchronizer output phase angle θ obtained in step 5, and the fractional-order virtual synchronizer dq-axis output voltage command E obtained in step 2... d E q The three-phase voltage modulation signal E of the fractional-order virtual synchronous machine is obtained through inverse rotational coordinate transformation of a single synchronous machine. a E b E c Then, the three-phase voltage modulation signal E a E b E c The SVPWM modulation stage generates the drive signal for the fractional-order virtual synchronous machine switch.

[0086] Example

[0087] To verify the control effect of the fractional-order virtual synchronous machine control method based on active fractional-order feedforward proposed in this invention, the proposed fractional-order virtual synchronous machine (hereinafter referred to as AFF-FOVSG) control method, the existing virtual synchronous machine (hereinafter referred to as VSG) control method (the VSG control method is mentioned in the background art as "Active Response Strategy of Energy Storage VSG Grid Connection Based on Active Fractional-Order Differential Correction", Vol. 44, No. 2, 2024, pp. 204-210), and the existing fractional-order virtual synchronous machine (hereinafter referred to as FOVSG) control method (the FOVSG control method is mentioned in the background art as "Frequency stability enhancement of an islanded microgrid: A fractional-order virtual synchronous generator", International Journal of Electrical Power and Energy) were compared. The article "An Enhanced Frequency Stability Control Method for Independent Microgrids: Fractional-Order Virtual Synchronous Machine" (International Journal of Power and Energy Systems, 2023, Vol. 147, No. 108896) presents a simulation and experimental comparison, primarily focusing on the performance in handling active power command P. ref and grid frequency f g Grid-connected active power P under step disturbance conditions eAnd the dynamic response performance at the output frequency f. Specifically:

[0088] First, the relevant parameters are set. In this embodiment, the relevant parameter settings in the fractional-order virtual synchronous machine control method based on active fractional-order feedforward of the present invention are as follows:

[0089] The virtual synchronous machine has a rated capacity of 100kVA and an active power command P. ref It has a power output of 20kW, a rated angular frequency ω0 of 314.16 rad / s, and a virtual inertia coefficient J of 6 kg·m. 2 The virtual damping coefficient D = 50.66, and the primary voltage regulation coefficient k q 1.4×10 -4 V / var, grid voltage amplitude U g Given a voltage of 311V, an output voltage amplitude E of 311V for the virtual synchronizer, and an equivalent inductive reactance X of the power grid line of 0.1Ω, the synchronization voltage coefficient K = 1.5U. g E / X is 1450815. It is worth noting that if the fractional-order coefficient μ = 1 and the feedforward compensation coefficient k in AFF-FOVSG are set... a If the value is 0, then AFF-FOVSG will be equivalent to VSG, which shows that VSG is only a special case of AFF-FOVSG; if the feedforward compensation coefficient k in AFF-FOVSG is set... a If the expression = 0, then AFF-FOVSG is equivalent to FOVSG, which shows that FOVSG is only a special case of AFF-FOVSG. At the same time, combined with... Figure 3 Through a series of formula derivations, the active power command P of the VSG grid-connected system at this time can be obtained. ref To grid-connected active power P e The closed-loop transfer function is The damping ratio of the corresponding VSG grid-connected active power closed-loop control system That is, the VSG grid-connected active power closed-loop control system is an underdamped system, therefore the VSG grid-connected active power P e With output frequency f in active power command P ref and grid frequency f g Under step disturbance conditions, dynamic oscillations will inevitably occur. Furthermore, according to... Figure 3 Through a series of formula derivations, the active power command P of the FOVSG grid-connected system can be obtained. ref To grid-connected active power P e The closed-loop transfer function is The first-order fractional coefficients in G1(s) are set to μ = 0.6, and the virtual inertia coefficient is set to J = 6 kg·m. 2The virtual damping coefficient is set to D = 50.66 to ensure that FOVSG and VSG have the same grid-connected active power steady-state response performance, while also effectively suppressing the grid-connected active power P of FOVSG. e With output frequency f in active power command P ref and grid frequency f g Dynamic oscillations existing under step disturbances.

[0090] In this embodiment, the feedforward compensation coefficient k will be optimized. a The values ​​of the fractional-order low-pass filter coefficient λ are used to further optimize the grid-connected active power P of the AFF-FOVSG. e With output frequency f in active power 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 command P of the AFF-FOVSG grid-connected system can be obtained. ref To grid-connected active power P e The closed-loop transfer function is

[0091] Therefore, the grid-connected active power dynamic response performance of VSG, FOVSG, and AFF-FOVSG can be directly analyzed by comparing and contrasting the closed-loop transfer functions G(s), G1(s), and G2(s). To further simplify the theoretical analysis process, the fractional-order coefficients in AFF-FOVSG are set to μ = 0.6, and the virtual inertia coefficient is set to J = 6 kg·m. 2 The virtual damping coefficient is set to D = 50.66, the fractional-order low-pass filter coefficient is set to λ = 0.5, and the feedforward compensation coefficient is set to k. a =0.1. Substituting the above parameters into the closed-loop transfer functions G2(s), G1(s), and G(s) respectively, we can obtain the active power command step disturbance ΔP of the grid-connected active power closed-loop control systems of AFF-FOVSG, 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 frequency step disturbance Δω of the grid-connected active power closed-loop control system of AFF-FOVSG, 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 frequency Δωg Output angular frequency response Δω(Δω / Δω) g For comparison with the Bode plot, please refer to the details below. Figure 5 (b) Figure 5 (c) and Figure 5 (d)

[0092] according to Figure 5 It can be observed that both the grid-connected active power closed-loop control system of VSG and the grid-connected active power closed-loop control system of FOVSG exhibit resonance peaks before the cutoff frequency. This phenomenon indicates that the grid-connected active power P of VSG and FOVSG... e With the output angular frequency circle in the active power command P ref and the angular frequency ω of the power grid g Both present dynamic oscillation and overshoot problems under step disturbance conditions; secondly, the AFF-FOVSG grid-connected active power closed-loop control system proposed in this invention does not have a significant resonance peak before the cutoff frequency. This phenomenon indicates that the grid-connected active power P of AFF-FOVSG... e With the output angular frequency ω in the active power command P ref and the angular frequency ω of the power grid g There is no dynamic oscillation problem under step disturbance conditions; III. Δω / ΔP of the AFF-FOVSG grid-connected active power closed-loop control system ref , Δω / Δω g Compared to FOVSG, AFF-FOVSG exhibits smaller resonance peaks and superior amplitude and phase responses in the low-to-mid frequency range. This phenomenon indicates that the grid-connected active power closed-loop control system corresponding to AFF-FOVSG responds better to active power commands P. ref and the angular frequency ω of the power grid g Under step disturbance conditions, it exhibits smaller output frequency overshoot amplitude and smaller output frequency change rate. It is worth noting that AFF-FOVSG also has the advantages of more control parameters and more flexible parameter selection, for example, by selecting appropriate fractional-order coefficient μ, fractional-order low-pass filter coefficient λ, and feedforward compensation coefficient k. a The value of is selected to flexibly optimize the grid-connected active power P of AFF-FOVSG. e The dynamic response performance with respect to the output angular frequency ω will not be listed in detail due to space limitations.

[0093] Based on the above parameter settings, simulation and experimental comparison tests were conducted, as follows:

[0094] The simulation and experimental test conditions were set as follows: initially, the virtual synchronous machine stably outputs 20kW of grid-connected active power; at 4.0s, the active power command P... ref The power output jumps from 20kW to 60kW, while the grid frequency f changes at 7.0s. g The frequency drops from 50Hz to 49.95Hz in a step.

[0095] 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 paper, AFF-FOVSG represents a fractional-order virtual synchronous machine control method based on active fractional-order feedforward proposed in this invention; FOVSG represents an existing fractional-order virtual synchronous machine control method; that is, the curve pointed to by FOVSG is the test waveform before using this invention, specifically the dynamic response test waveform of the existing fractional-order virtual synchronous machine control method; VSG represents an existing virtual synchronous machine control method; that is, the curve pointed to by VSG is the test waveform before using this invention, specifically the dynamic response test waveform of the existing virtual synchronous machine control method; and the curve pointed to by AFF-FOVSG is the test waveform after using this invention, specifically the dynamic response test waveform of the fractional-order virtual synchronous machine control method based on active fractional-order feedforward proposed in this invention.

[0096] according to Figure 6 (a) It can be seen that, firstly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention e There are no dynamic oscillations or overshoot issues with the output frequency f. The corresponding grid-connected active power P of the VSG is already available. e There is significant dynamic oscillation and power overshoot; the grid-connected active power P corresponding to FOVSG is already known. e It also suffers from dynamic oscillations and power overshoot, and has a slow dynamic response speed; secondly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention is... e It has the fastest dynamic response speed and grid-connected active power P e The power overshoot is 0%, far lower than the 8.27% corresponding to the existing FOVSG. The maximum output frequency response overshoot amplitude of the existing FOVSG at the output frequency f is 0.13Hz, far higher than the 0.03Hz corresponding to the proposed AFF-FOVSG. Therefore, it can be seen that the grid-connected active power P of the proposed AFF-FOVSG is significantly higher than that of the existing VSG and FOVSG. e With output frequency f in active power command P ref The AFF-FOVSG exhibits smaller dynamic oscillations and overshoot during the jump from 20kW to 60kW; compared to existing FOVSGs, the AFF-FOVSG demonstrates better performance in terms of active power command P. ref In the process of jumping from 20kW to 60kW, it has smaller grid-connected active power overshoot, faster grid-connected active power dynamic response speed and smaller output frequency response overshoot.

[0097] And according to Figure 6 (b) It can be seen that, firstly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention... eThere are no dynamic oscillations or overshoot issues with the output frequency f. The corresponding grid-connected active power P of VSG and FOVSG is already available. e Both the output frequency f and the output frequency exhibit significant dynamic oscillations and overshoot; secondly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention... e Compared to existing FOVSGs, the AFF-FOVSG exhibits smaller power overshoot, and its output frequency f has a smaller rate of change compared to existing FOVSGs. Therefore, the AFF-FOVSG proposed in this invention has a higher grid-connected active power P compared to existing VSGs and FOVSGs. e With output frequency f at grid frequency f g The AFF-FOVSG exhibits smaller dynamic oscillations and overshoot during the step transition from 50Hz to 49.95Hz; compared to existing FOVSGs, the AFF-FOVSG achieves better performance at the grid frequency f. g It exhibits smaller grid-connected active power overshoot and smaller output frequency change rate during the step transition from 50Hz to 49.95Hz.

[0098] according to Figure 7 (a) It can be seen that, firstly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention e There are no dynamic oscillations or overshoot issues with the output frequency f. The corresponding grid-connected active power P of the VSG is already available. e There is significant dynamic oscillation and power overshoot; the grid-connected active power P corresponding to FOVSG is already known. e It also suffers from dynamic oscillations and power overshoot, and has a slow dynamic response speed; secondly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention is... e It has the fastest dynamic response speed and grid-connected active power P e The power overshoot is 0%, far lower than the 8.29% corresponding to the existing FOVSG. The maximum output frequency response overshoot amplitude of the existing FOVSG at the output frequency f is 0.13Hz, far higher than the 0.025Hz corresponding to the proposed AFF-FOVSG. Therefore, it can be seen that the grid-connected active power P of the proposed AFF-FOVSG is significantly higher than that of the existing VSG and FOVSG. e With output frequency f in active power command P ref The AFF-FOVSG exhibits smaller dynamic oscillations and overshoot during the jump from 20kW to 60kW; compared to existing FOVSGs, the AFF-FOVSG demonstrates better performance in terms of active power command P. ref In the process of jumping from 20kW to 60kW, it has smaller grid-connected active power overshoot, faster grid-connected active power dynamic response speed and smaller output frequency response overshoot.

[0099] And according to Figure 7 (b) It can be seen that, firstly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention...e There are no dynamic oscillations or overshoot issues with the output frequency f. The corresponding grid-connected active power P of VSG and FOVSG is already available. e Both the output frequency f and the output frequency exhibit significant dynamic oscillations and overshoot; secondly, the grid-connected active power P corresponding to the AFF-FOVSG proposed in this invention... e Compared to existing FOVSGs, the AFF-FOVSG exhibits smaller power overshoot, and its output frequency f has a smaller rate of change compared to existing FOVSGs. Therefore, the AFF-FOVSG proposed in this invention has a higher grid-connected active power P compared to existing VSGs and FOVSGs. e With output frequency f at grid frequency f g The AFF-FOVSG exhibits smaller dynamic oscillations and overshoot during the step transition from 50Hz to 49.95Hz; compared to existing FOVSGs, the AFF-FOVSG achieves better performance at the grid frequency f. g It exhibits smaller grid-connected active power overshoot and smaller output frequency change rate during the step transition from 50Hz to 49.95Hz.

[0100] Will Figure 7 (a) and Figure 6 Comparing the results of (a), it is not difficult to see that this implementation method Figure 7 The experimental test results in (a) can be compared with those in (a) Figure 6 The simulation test results in (a) maintain a one-to-one correspondence, both of which fully demonstrate that, on the one hand, the AFF-FOVSG proposed in this invention can solve the grid-connected active power P of existing VSG and FOVSG. e With output frequency f in active power command P ref Dynamic oscillations and overshoot problems are prone to occur under step disturbances; on the other hand, the AFF-FOVSG proposed in this invention has a higher efficiency than the existing FOVSG in terms of active power command P. ref Under step disturbances, the AFF-FOVSG proposed in this invention has the advantages of smaller grid-connected active power overshoot, faster grid-connected active power dynamic response speed and smaller output frequency response overshoot amplitude. Therefore, compared with the existing VSG and FOVSG, the control effect of the AFF-FOVSG proposed in this invention is better.

[0101] And again Figure 7 (b) and Figure 6 (b) Comparing the results, it is not difficult to see that this implementation method Figure 7 The experimental test results in (b) can be compared with those in [the other two] Figure 6 (b) shows a one-to-one correspondence between the simulation test results and the actual results, both of which fully demonstrate that the AFF-FOVSG proposed in this invention can solve the grid-connected active power P of existing VSG and FOVSG. e With output frequency f at grid frequency f gDynamic oscillations and overshoot problems are prone to occur under step disturbances; on the other hand, the AFF-FOVSG proposed in this invention has better performance than existing FOVSGs at the grid frequency f g It has the advantages of smaller grid-connected active power overshoot and smaller output frequency change rate under step disturbance. Therefore, compared with the existing VSG and FOVSG, the AFF-FOVSG proposed in this invention has better control effect.

[0102] 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 fractional-order virtual synchronous machine control method based on active fractional-order feedforward, characterized in that, Comprising the following steps: Step 1, power calculation part, first collect the output current i a , i b , i c and output voltage u a , u b , u c , through single synchronous rotating coordinate transformation to obtain the dq component I d , I q of the output current and the dq component U d , U q of the output voltage based on the output phase angle θ of the fractional order virtual synchronous machine, and then through the power calculation link to obtain the grid-connected active power P e and grid-connected reactive power Q e of the fractional order virtual synchronous machine; Step 2, primary voltage regulation part, according to the fractional order virtual synchronous machine obtained in step 1, grid-connected reactive power Q e and the reactive power instruction Q of the fractional order virtual synchronous machine ref , the primary voltage regulation coefficient k q , and the voltage instruction E0, the dq axis output voltage instruction E of the fractional order virtual synchronous machine obtained through the primary voltage regulation control equation d , E q ; Step 3, active fractional order feedforward quantity calculation, the active instruction P of the fractional order virtual synchronous machine is divided by the active instruction P of the actual synchronous machine ref Subtract the grid-connected active P of the fractional order virtual synchronous machine obtained in step 1 e , obtain the power difference ΔP as the input quantity of the active fractional order feedforward control, and pass the power difference ΔP through the fractional order low-pass filtering link containing the feedforward compensation coefficient k a , the virtual inertia coefficient J, the rated angular frequency ω0, the virtual damping coefficient D and the fractional order low-pass filtering coefficient λ to obtain the feedforward quantity δ of the active fractional order feedforward control a ; Step 4, fractional order rotor motion equation part, according to the power difference ΔP obtained in step 3 and the virtual inertia coefficient J of the fractional order virtual synchronous machine, the rated angular frequency ω0, the virtual damping coefficient D and the fractional order coefficient μ, the angular frequency deviation Δω of the fractional order virtual synchronous machine is obtained through the fractional order rotor motion equation; Step 5, an output phase angle generating section, adds the fractional order virtual synchronous machine angle frequency deviation Δω obtained in Step 4 to the rated angle frequency ω0 to obtain an output angle frequency ω of the fractional order virtual synchronous machine, and obtains a phase δ of the fractional order virtual synchronous machine by integrating the output angle frequency ω, and adds the phase δ to the feedforward amount δ obtained in Step 3 to obtain an output phase angle θ of the fractional order virtual synchronous machine. a to the output phase angle θ of the fractional order virtual synchronous machine. Step 6, firstly, the phase angle θ of the fractional order virtual synchronous machine is output according to the score obtained in step 5, and the dq axis output voltage command E of the fractional order virtual synchronous machine obtained in step 2 d , q , The three-phase voltage modulation signal E of the fractional order virtual synchronous machine is obtained by single synchronous rotation coordinate inverse transformation a , b , c , The three-phase voltage modulation signal E is further modulated by the SVPWM modulation link to generate the drive signal of the fractional order virtual synchronous machine switch tube a , b , c .

2. The fractional order virtual synchronous machine control method based on active fractional order feedforward according to claim 1, characterized in that, The grid-connected active power P in step 1 e The used calculation equation is: P e = 1.5(U d I d + U q I q ), Grid-connected reactive Q e The calculation equation used is: Q e = 1.5(U q I d -U d I q ).

3. The fractional order virtual synchronous machine control method based on active fractional order feedforward according to claim 1, characterized in that, The output voltage command E in step 2 d The equation used was: E d = (Q ref - Q e )k q + E0, Output voltage command E q The calculation equation used is: E q ＝0。 4. The fractional order virtual synchronous machine control method based on active fractional order feedforward according to claim 1, characterized in that, The calculation formula of the input power difference ΔP of the active fractional order feedforward control in step 3 is: ΔP = P ref - P e , The feedforward quantity δ of the active fractional order feedforward control a The calculation formula used is: where k a is a feed-forward compensation coefficient and s is the Laplace operator.

5. The fractional order virtual synchronous machine control method based on active fractional order feedforward according to claim 1, characterized in that, The calculation formula of the angular frequency deviation Δω in step 4 is: In the formula, s is the Laplace operator.

6. The fractional order virtual synchronous machine control method based on active fractional order feedforward according to claim 1, characterized in that, The calculation equation of the output angular frequency ω in step 5 is: ω=Δω+ω0, The calculation equation of the phase δ is: The calculation formula of the output phase angle θ is: θ = δ + δ a . In the formula, s is the Laplace operator.

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