Fractional order virtual synchronous machine control method based on lead-lag correction

Abstract

The invention discloses a fractional order virtual synchronous machine control method based on lead-lag correction, and the method comprises the steps: replacing a rotor motion equation in the fractional order virtual synchronous machine control method with a rotor motion equation based on lead-lag correction, and adjusting a lead correction coefficient and a lag correction coefficient which are introduced. The dynamic response performance of the grid-connected active power and the output frequency of the fractional order virtual synchronous machine under the disturbance of the active reference instruction, the power grid frequency and the like is optimized, and the problem that the grid-connected active power response performance and the inertia response performance of the fractional order virtual synchronous machine are difficult to consider at the same time can be effectively solved. The method has the advantages of being capable of restraining dynamic oscillation and power overshoot of grid-connected active power, reducing output frequency response overshoot amplitude, having more control parameters and being more flexible in control parameter selection, and can be suitable for the field of fractional order virtual synchronous machine grid-connected control in the power electronic technology.

Description

Technical Field

[0001] The present invention relates to the technical field of virtual synchronous machine control, and particularly to a fractional-order virtual synchronous machine control method based on lead-lag compensation, which is applicable to the grid-connected control field of fractional-order virtual synchronous machines in power electronics technology and the control field of microgrids including such fractional-order virtual synchronous machines connected to the distribution network. Background Art

[0002] By introducing an integer-order virtual inertia control link, a virtual synchronous generator (VSG) can improve the voltage regulation ability and inertia support level of the connected power grid or microgrid. However, due to the introduction of the integer-order virtual inertia link, the active power closed-loop control system of VSG grid connection becomes a second-order oscillation system, which is prone to dynamic oscillation problems of the grid-connected active power and output frequency of VSG under disturbances such as active power reference commands and grid frequency. In addition, a fractional-order virtual synchronous generator (FOVSG) replaces the integer-order virtual inertia control link in VSG with a fractional-order virtual inertia control link. By adjusting the introduced fractional-order coefficient μ, the dynamic oscillation of the grid-connected active power of VSG can be effectively suppressed. However, there is a problem that it is difficult to balance the active power response performance and inertia response performance, that is, it is necessary to weigh the suppression effects of the dynamic oscillation of the grid-connected active power and the overshoot of the output frequency, and make a compromise choice for the value of μ.

[0003] Therefore, various studies have been conducted, such as the article "Virtual Synchronous Generator Control Technology for Fractional-Order Virtual Inertia of Grid-Connected Inverters", published in the 36th volume, No. 02, 2021, pages 463-468 of "Control and Decision". This article proposes an improved control strategy for a fractional-order virtual synchronous generator (FOVSG), which replaces the integer-order virtual inertia control link in VSG with a fractional-order virtual inertia control link and can effectively suppress the dynamic oscillation of the grid-connected active power and output frequency of VSG by adjusting the fractional-order coefficient μ. However, it has the disadvantages of difficult to balance the active power response performance and inertia response performance, not considering the overshoot of the output frequency response, and only having one additional adjustable parameter.

[0004] Article titled "Frequency stability enhancement of an islanded microgrid:A fractional-order virtual synchronous generator", LONG B, LI X Y, RODRIGUEZ J, et al., 《International Journal of Electrical Power and Energy Systems》, 2023, 147, 108896 ("A method for enhancing the frequency stability control of an islanded microgrid: Fractional-order virtual synchronous machine", Article No. 108896, Volume 147, 2023, 《International Journal of Electrical Power and Energy Systems》); This article proposes an improved control method for FOVSG based on a new fractional-order model predictive controller. On the basis of using the fractional-order model predictive controller to improve the accuracy of the prediction model, it can effectively suppress the dynamic oscillation of the active power output and output frequency of the VSG during the process of coping with system disturbances. However, it does not consider too much the problem of overshoot in the output frequency of the VSG under grid-connected conditions, and only adds one adjustable parameter.

[0005] Article titled "Active power response strategy of energy storage VSG grid connection based on active fractional-order differential correction", 《Automation of Electric Power Systems》, 2024, Vol. 44, No. 02, pp. 204 - 210; This article proposes an optimized control strategy for the active power response of VSG grid connection based on active fractional-order differential correction, which has a control effect equivalent to that of FOVSG, that is, it effectively solves the problem that it is difficult to balance good dynamic and steady-state response performance of the active power of VSG grid connection under two disturbances: active reference instruction and grid frequency. However, it has the disadvantages of obvious overshoot in the output frequency response, only one additional control parameter, and inflexible selection of control parameters.

[0006] The article titled "Fractional-order virtual synchronous generator" by YU Y, GUAN Y J, KANG W F, et al., published in 《IEEE Transactions on Power Electronics》, 2023, 38(6), 6874-6879 (in "Fractional-order virtual synchronous generator", pages 6874 - 6879, Volume 38, Issue 6, 2023 of 《IEEE Transactions on Power Electronics》); this article proposes an improved control method for FOVSG based on double fractional-order virtual inertia, replacing the integer-order virtual inertia control link in VSG with a double fractional-order virtual inertia control link, which can effectively suppress the dynamic oscillation of the grid-connected active power and output frequency of VSG, and has the advantages of more adjustable parameters and more flexible selection of control parameters. However, it does not consider the response optimization problem under grid frequency disturbance, and there is also the disadvantage that the output frequency response is prone to overshoot.

[0007] As can be seen from the above, although the existing technology has solved the problem of dynamic oscillation of the grid-connected active power and output frequency of the virtual synchronous generator under disturbances such as active reference commands and grid frequency, there are still disadvantages such as fewer adjustable parameters, limited flexibility in parameter selection, and the output frequency response performance still needs to be further improved. Summary of the Invention

[0008] In order to overcome the limitations of various technical solutions in the background technology, the present invention provides a control method for a fractional-order virtual synchronous generator based on lead-lag correction, aiming at the problem that it is difficult to balance the grid-connected active power response performance and inertia response performance of the fractional-order virtual synchronous generator under disturbances such as active reference commands and grid frequency. This control method can simultaneously improve the grid-connected active power response performance and inertia response performance of the fractional-order virtual synchronous generator, and has the advantages of suppressing the dynamic oscillation and power overshoot of the grid-connected active power, reducing the overshoot amplitude of the output frequency response, more control parameters, and more flexible selection of control parameters.

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

[0010] A control method for a fractional-order virtual synchronous generator based on lead-lag correction, comprising the following steps:

[0011] Step 1, power calculation part, first collect the output current i a , i b , i c and the output voltage u a , u b , u c, the dq components I of the output current oriented by the output phase angle θ of the fractional-order virtual synchronous machine are obtained through single synchronous rotation coordinate transformation d , I q and the dq components U of the output voltage d , U q , and then the grid-connected active power P of the fractional-order virtual synchronous machine is obtained through the power calculation link e and the grid-connected reactive power Q e ;

[0012] Step 2, the primary voltage regulation part. According to the grid-connected reactive power Q of the fractional-order virtual synchronous machine obtained in Step 1 e and the reactive power reference command Q of the fractional-order virtual synchronous machine ref , the primary voltage regulation coefficient k q , the voltage reference command E of the fractional-order virtual synchronous machine 0 , the dq-axis output voltage reference command E of the fractional-order virtual synchronous machine is obtained through the primary voltage regulation control equation d , E q ;

[0013] Step 3, the rotor motion equation part based on lead-lag correction. According to the grid-connected active power P of the fractional-order virtual synchronous machine obtained in Step 1 e and the active power reference command P ref , the virtual inertia coefficient J, the fractional-order coefficient μ, the virtual damping coefficient D, and the rated angular frequency ω 0 , the angular frequency deviation Δω of the fractional-order virtual synchronous machine is obtained through the rotor motion equation based on lead-lag correction;

[0014] Step 4, the output phase angle generation part. The angular frequency deviation Δω of the fractional-order virtual synchronous machine obtained in Step 3 is added to the rated angular frequency ω 0 to obtain the output angular frequency ω of the fractional-order virtual synchronous machine, and the output angular frequency ω is passed through an integral operation link to obtain the output phase angle θ of the fractional-order virtual synchronous machine;

[0015] Step 5, first, according to the output phase angle θ of the fractional-order virtual synchronous machine obtained in Step 4, and the dq-axis output voltage reference command E of the fractional-order virtual synchronous machine obtained in Step 2 d , E q , the three-phase voltage modulation signals E of the fractional-order virtual synchronous machine are obtained through single synchronous rotation coordinate inverse transformation a , E b , E c , and then the three-phase voltage modulation signals E a , E b , E c are used to generate the drive signals of the switching tubes of the fractional-order virtual synchronous machine through the SVPWM modulation link.

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

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

[0018] The grid-connected reactive power Q e The calculation equation used is:

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

[0020] Preferably, the output voltage reference command E in step 2 d The calculation equation used is:

[0021] E d = (Q ref - Q e )k q + E 0 ,

[0022] The output voltage reference command E q The calculation equation used is:

[0023] E q = 0.

[0024] Preferably, the calculation equation for the angular frequency deviation Δω in step 3 is:

[0025]

[0026] Wherein, T 1 is the lead correction coefficient, T 2 is the lag correction coefficient, and s is the Laplace operator.

[0027] Preferably, the calculation equation for the output angular frequency ω in step 4 is:

[0028] ω = Δω + ω 0 ,

[0029] The calculation equation for the output phase angle θ is:

[0030]

[0031] Wherein, s is the Laplace operator.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention discloses a fractional-order virtual synchronous machine control method based on lead-lag compensation. This method replaces the rotor motion equation in the fractional-order virtual synchronous machine control method with a rotor motion equation based on lead-lag compensation. By adjusting the introduced lead compensation coefficient and lag compensation coefficient, 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 reference commands and grid frequencies is optimized. It can effectively solve the problem that it is difficult to balance the grid-connected active power response performance and inertia response performance of the fractional-order virtual synchronous machine. It has the advantages of suppressing the dynamic oscillation and power overshoot of the grid-connected active power, reducing the overshoot amplitude of the output frequency response, having more control parameters and more flexible control parameter selection, and is applicable to the field of grid-connected control of fractional-order virtual synchronous machines in power electronics technology and the field of microgrid incorporating such fractional-order virtual synchronous machines into the distribution grid control. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the control structure diagram of the fractional-order virtual synchronous machine according to the embodiment of the present invention.

[0035] Figure 2 is the calculation schematic diagram of the rotor motion equation based on lead-lag compensation.

[0036] Figure 3 is the closed-loop equivalent control structure diagram of the grid-connected active power of the fractional-order virtual synchronous machine according to the embodiment of the present invention.

[0037] Figure 4 is the coordinate transformation and modulation schematic diagram according to the embodiment of the present invention.

[0038] Figure 5 is the comparative Bode diagram of the virtual synchronous machine before and after adopting the present invention.

[0039] Figure 6 is the comparative diagram of the simulation waveforms of the virtual synchronous machine before and after adopting the present invention.

[0040] Figure 7 is the comparative diagram of the experimental waveforms of the virtual synchronous machine before and after adopting the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The following detailed description will be further described in conjunction with the above drawings, specifically as follows:

[0042] Please refer to Figure 1 , a fractional-order virtual synchronous machine control method based on lead-lag compensation proposed by the present invention includes the following steps:

[0043] Step 1, power calculation part, first collect the output current i of the fractional-order virtual synchronous machinea , i b , i c and the output voltage u a , u b , u c , after single synchronous rotation coordinate transformation, the dq components I of the output current oriented by the output phase angle θ of the fractional-order virtual synchronous machine are obtained d , I q and the dq components U of the output voltage d , U q , and then through the power calculation link, the grid-connected active power P of the fractional-order virtual synchronous machine is obtained e and the grid-connected reactive power Q e ;

[0044] That is, the calculation equation used for the grid-connected active power P e is as follows:

[0045] P e = 1.5(U d I d + U q I q ),

[0046] The calculation formula used for the grid-connected reactive power Q e is as follows:

[0047] Q e = 1.5(U q I d - U d I q ).

[0048] Step 2, the primary voltage regulation part. According to the grid-connected reactive power Q of the fractional-order virtual synchronous machine obtained in Step 1 e and the reactive power reference command Q of the fractional-order virtual synchronous machine ref , the primary voltage regulation coefficient k q , and the voltage reference command E of the fractional-order virtual synchronous machine 0 , through the primary voltage regulation control equation, the dq-axis output voltage reference command E of the fractional-order virtual synchronous machine is obtained d , E q ;

[0049] That is, the calculation equation used for the output voltage reference command E d is as follows:

[0050] E d = (Q ref - Q e )k q + E 0 ,

[0051] The output voltage reference command Eq The calculation equation used is as follows:

[0052] E q = 0.

[0053] Step 3: Based on the rotor motion equation part of the lead-lag correction, as Figure 2 shown, according to the grid-connected active power P of the fractional-order virtual synchronous machine obtained in Step 1 e and the active power reference command P ref , virtual inertia coefficient J, fractional-order coefficient μ, virtual damping coefficient D, and rated angular frequency ω 0 , the angular frequency deviation Δω of the fractional-order virtual synchronous machine is obtained through the rotor motion equation based on the lead-lag correction;

[0054] That is, the calculation equation for the angular frequency deviation Δω is as follows:

[0055]

[0056] where T 1 is the lead correction coefficient, T 2 is the lag correction coefficient, and s is the Laplace operator.

[0057] Step 4: Output phase angle generation part. Add the angular frequency deviation Δω of the fractional-order virtual synchronous machine obtained in Step 3 to the rated angular frequency ω 0 to obtain the output angular frequency ω of the fractional-order virtual synchronous machine. Pass the output angular frequency ω through an integral operation link to obtain the output phase angle θ of the fractional-order virtual synchronous machine;

[0058] That is, the calculation equation for the output angular frequency ω is as follows:

[0059] ω = Δω + ω 0 ,

[0060] The calculation equation for the output phase angle θ is as follows:

[0061]

[0062] where s is the Laplace operator.

[0063] According to Figure 1 the power transmission model given, and combining the above calculation equations, the closed-loop equivalent control structure diagram of the grid-connected active power of the fractional-order virtual synchronous machine as shown in Figure 3 can be obtained. Figure 3 Among them, δ is the power factor angle of the fractional-order virtual synchronous machine; K is the synchronous voltage coefficient of the fractional-order virtual synchronous machine;

[0064] That is, the calculation equation for the power factor angle δ is as follows:

[0065]

[0066] The calculation equation for the synchronous voltage coefficient K is as follows:

[0067]

[0068] In the formula, U g is the amplitude of the grid voltage, ω g is the angular frequency of the grid, E is the output voltage amplitude of the fractional-order virtual synchronous machine, X is the equivalent inductive reactance of the grid line, and s is the Laplace operator.

[0069] Step 5, as Figure 4 shown, first, according to the output phase angle θ of the fractional-order virtual synchronous machine obtained in Step 4, and the dq-axis output voltage reference commands E d , E q obtained in Step 2, through the inverse transformation of the single synchronous rotating coordinate, the three-phase voltage modulation signals E a , E b , E c of the fractional-order virtual synchronous machine are obtained. Then, from the three-phase voltage modulation signals E a , E b , E c through the SVPWM modulation link, the drive signals of the switching tubes of the fractional-order virtual synchronous machine are generated.

[0070] Embodiment

[0071] To verify the control effect of the control method of the fractional-order virtual synchronous machine based on lead-lag correction proposed in the present invention, the control method of the fractional-order virtual synchronous machine based on lead-lag correction proposed in the present invention (hereinafter referred to as LLC-FOVSG) and the existing virtual synchronous machine (hereinafter referred to as VSG) control method (the VSG control method is given in the article titled "Active Power Response Strategy of Energy Storage VSG Grid-Connected Based on Active Power Fractional-Order Differential Correction", Vol. 44, No. 2, 2024, pp. 204-210 of Electric Power Automation Equipment) and the existing fractional-order virtual synchronous machine (hereinafter referred to as FOVSG) control method (the FOVSG control method is given in the article titled "Virtual Synchronous Generator Control Technology for Fractional-Order Virtual Inertia of Grid-Connected Inverters", Vol. 36, No. 02, 2021, pp. 463-468 of Control and Decision) are compared through simulation and experiment. The main comparison is the grid-connected active power P e of the virtual synchronous machine and the dynamic response performance of the output frequency f under the condition of step disturbance of the active power reference command P ref and the grid frequency f g . Specifically as follows:

[0072] First, set the relevant parameters. In this embodiment, the relevant parameter settings in a fractional-order virtual synchronous generator (FOVSG) control method based on lead-lag correction are as follows:

[0073] The rated capacity of the virtual synchronous generator is 100 kVA, and the active power reference command P ref is 20 kW, and the rated angular frequency ω 0 is 314.16 rad / s. The virtual inertia coefficient J is 6 kg·m 2 , and the primary voltage regulation coefficient k q is 1.4×10 -4 V / var. The grid voltage amplitude U g is 311 V, the output voltage amplitude E of the virtual synchronous generator is 311 V, and the equivalent inductive reactance X of the grid line is 0.1 Ω. Then the synchronous voltage coefficient K = 1.5U g E / X is 1450815. It is worth noting that if the fractional-order coefficient μ in FOVSG is set to 1, then FOVSG will be equivalent to VSG, which shows that VSG is only a special case of FOVSG; if the lead correction coefficient T 1 = 0 and the lag correction coefficient T 2 = 0 in LLC-FOVSG, then LLC-FOVSG will be equivalent to FOVSG, which shows that FOVSG is only a special case of LLC-FOVSG. At the same time, by combining Figure 3 and through a series of formula derivation processes, the closed-loop transfer function from the active power reference command P ref to the grid-connected active power P e of the existing VSG grid-connected system can be obtained as The damping ratio of the corresponding VSG grid-connected active power closed-loop control system is 0.152, which is less than 1. That is, the VSG grid-connected active power closed-loop control system is an underdamped system. Therefore, the grid-connected active power P e and the output frequency f of VSG will inevitably have the problem of dynamic oscillation under the step disturbance conditions of the active power reference command P ref and the grid frequency f g . Also, according to Figure 3 and through a series of formula derivation processes, the closed-loop transfer function from the active power reference command P ref to the grid-connected active power P e of the existing FOVSG grid-connected system can be obtained as And set the fractional-order coefficient μ in the closed-loop transfer function G 1 (s) to 0.2, that is, μ = 0.2, to ensure that the grid-connected active power P e and the output frequency f of FOVSG are under the active power reference command P ref and the grid frequency f gThere is no dynamic oscillation phenomenon under the condition of step disturbance.

[0074] In this embodiment, by reasonably setting the fractional-order coefficient μ, the lead compensation coefficient T 1 and the lag compensation coefficient T 2 values, the dynamic response performance of the LLC-FOVSG grid-connected system is optimized to achieve the grid-connected active power P e and the output frequency f under the active power reference command P ref and the grid frequency f g There is no dynamic oscillation phenomenon under the step disturbance condition. Similarly, according to Figure 3 and through a series of formula derivation processes, the active power reference command P ref to the grid-connected active power P e closed-loop transfer function is Therefore, the closed-loop transfer functions G(s), G 1 (s) and G 2 (s) can be directly used to compare and analyze the dynamic response performance of the grid-connected active power of VSG, FOVSG and LLC-FOVSG. To further simplify the theoretical analysis process, the fractional-order coefficient μ = 0.6, the lead compensation coefficient T 1 = 0.9, and the lag compensation coefficient T 2 = 0.4 in LLC-FOVSG are set. Substitute the above parameters into the closed-loop transfer functions G 2 (s), G 1 (s) and G(s) respectively, and the step disturbance amount ΔP ref of the active power reference command to the grid-connected active power response amount ΔP e (ΔP c / ΔP ref ) comparison Bode plot can be obtained, as shown in detail in Figure 5 (a). Similarly, the step disturbance amount Δω g of the grid frequency to the grid-connected active power response amount ΔP e (ΔP e / Δω g ), the step disturbance amount ΔP ref of the active power reference command to the output angular frequency response amount Δω (Δω / ΔP ref ) and the step disturbance amount Δω g of the grid frequency to the output angular frequency response amount Δω (Δω / Δω g ) comparison Bode plots can be obtained respectively, as shown in detail in Figure 5 (b), Figure 5(c) and Figure 5 (d).

[0075] According to Figure 5 it can be found that: First, there is a resonance peak in the grid-connected active power closed-loop control system of the existing VSG in the low-frequency band. This phenomenon indicates that there is a problem of dynamic oscillation in the grid-connected active power P e of the VSG and the output angular frequency ω under the step disturbance conditions of the active reference command P ref and the grid angular frequency ω g ; Second, there is no obvious resonance peak in the low-frequency band of the grid-connected active power closed-loop control systems of the LLC-FOVSG proposed in the present invention and the existing FOVSG. This phenomenon indicates that there is no problem of dynamic oscillation in the grid-connected active power P e of the LLC-FOVSG and the FOVSG and the output angular frequency ω under the step disturbance conditions of the active reference command P ref and the grid angular frequency ω g ; Third, the Δω / ΔP ref and Δω / Δ ωg of the grid-connected active power closed-loop control system of the LLC-FOVSG proposed in the present invention have smaller resonance peaks compared with the existing FOVSG. This phenomenon indicates that the grid-connected active power closed-loop control system corresponding to the LLC-FOVSG has smaller overshoot amplitudes of the output frequency under the step disturbance conditions of the active reference command P ref and the grid angular frequency ω g . It is worth pointing out that the LLC-FOVSG proposed in the present invention also has more adjustable parameters and more flexible parameter selection. For example, by selecting reasonable values of the fractional-order coefficient μ, the lead correction coefficient T 1 and the lag correction coefficient T 2 , the dynamic response performance of the grid-connected active power P e of the LLC-FOVSG and the output angular frequency ω can be flexibly optimized. Due to space limitations, they are not listed one by one.

[0076] Based on the above parameter settings, simulation and experimental comparative tests were carried out as follows:

[0077] The simulation and experimental test conditions were set as follows: At the initial moment, the virtual synchronous machine stably outputs 20 kW of grid-connected active power. At 4.0 s, the active reference command P ref steps from 20 kW to 60 kW, and at 7.0 s, the grid frequency f g steps down from 50 Hz to 49.95 Hz.

[0078] According to the above conditions, the simulation and experimental test comparison diagrams shown in Figure 6 and Figure 7 were obtained respectively. Among them, Figure 6 andFigure 7 In it, LLC-FOVSG represents a fractional-order virtual synchronous generator control method proposed in the present invention based on lead-lag correction. FOVSG represents an existing fractional-order virtual synchronous generator control method. That is, the curve pointed to by FOVSG is the test waveform diagram before the present invention is adopted, specifically the dynamic response test waveform diagram of the existing fractional-order virtual synchronous generator control method. VSG represents an existing virtual synchronous generator control method. That is, the curve pointed to by VSG is the test waveform diagram before the present invention is adopted, specifically the dynamic response test waveform diagram of the existing virtual synchronous generator control method. The curve pointed to by LLC-FOVSG is the test waveform diagram after the present invention is adopted, specifically the dynamic response test waveform diagram of a fractional-order virtual synchronous generator control method proposed in the present invention based on lead-lag correction.

[0079] According to Figure 6 (a), it can be seen that: First, for the grid-connected active power P corresponding to LLC-FOVSG proposed in the present invention e and the output frequency f, there are no dynamic oscillations. For the grid-connected active power P corresponding to the existing VSG e there are large dynamic oscillations and power overshoots, and the dynamic response speed is the slowest. Second, for the grid-connected active power P corresponding to LLC-FOVSG proposed in the present invention e it has the smallest power overshoot. For the grid-connected active power P corresponding to the existing FOVSG e although it has the fastest dynamic response speed, there are large power overshoots. Third, the overshoot amplitude of the output frequency f corresponding to LLC-FOVSG proposed in the present invention is 0.09 Hz, which is lower than 0.14 Hz corresponding to the existing FOVSG. It can be seen that, on the one hand, for the grid-connected active power P and the output frequency f corresponding to LLC-FOVSG proposed in the present invention compared with the existing VSG e both have smaller dynamic oscillations during the process of the active power reference command P ref stepping from 20 kW to 60 kW. On the other hand, for LLC-FOVSG proposed in the present invention compared with the existing FOVSG during the process of the active power reference command P ref stepping from 20 kW to 60 kW, it has a smaller grid-connected active power overshoot and output frequency response overshoot amplitude.

[0080] Also according to Figure 6 (b), it can be seen that: First, for the grid-connected active power P corresponding to LLC-FOVSG proposed in the present invention e and the output frequency f, there are no dynamic oscillations. For the grid-connected active power P corresponding to the existing VSG e and the output frequency f, there are large dynamic oscillations. Second, for the grid-connected active power P corresponding to LLC-FOVSG proposed in the present invention ehas a similar power overshoot to the existing FOVSG, but the output frequency f corresponding to the existing FOVSG has a larger output frequency overshoot; Third, the output frequency f corresponding to the LLC-FOVSG proposed in the present invention has a smaller frequency change rate compared to the existing FOVSG. It can be seen that, on the one hand, the LLC-FOVSG proposed in the present invention has smaller dynamic oscillations in the grid-connected active power P e and the output frequency f during the process of the grid frequency f g stepping from 50 Hz to 49.95 Hz compared to the existing VSG; on the other hand, the LLC-FOVSG proposed in the present invention has a smaller output frequency overshoot and output frequency change rate compared to the existing FOVSG during the process of the grid frequency f g stepping from 50 Hz to 49.95 Hz.

[0081] According to Figure 7 (a), it can be seen that: First, there are no dynamic oscillations in the grid-connected active power P e and the output frequency f corresponding to the LLC-FOVSG proposed in the present invention. There are large dynamic oscillations and power overshoots in the grid-connected active power P e corresponding to the existing VSG, and the dynamic response speed is the slowest; Second, the grid-connected active power P e corresponding to the LLC-FOVSG proposed in the present invention has the smallest power overshoot. Although the grid-connected active power P e corresponding to the existing FOVSG has the fastest dynamic response speed, there is a large power overshoot; Third, the overshoot amplitude of the output frequency f corresponding to the LLC-FOVSG proposed in the present invention is 0.08 Hz, which is lower than 0.13 Hz corresponding to the existing FOVSG. It can be seen that, on the one hand, the LLC-FOVSG proposed in the present invention has smaller dynamic oscillations in the grid-connected active power P e and the output frequency f during the process of the active power reference command P ref stepping from 20 kW to 60 kW compared to the existing VSG; on the other hand, the LLC-FOVSG proposed in the present invention has a smaller grid-connected active power overshoot and output frequency response overshoot amplitude compared to the existing FOVSG during the process of the active power reference command P ref stepping from 20 kW to 60 kW.

[0082] Also according to Figure 7 (b), it can be seen that: First, there are no dynamic oscillations in the grid-connected active power P e and the output frequency f corresponding to the LLC-FOVSG proposed in the present invention. There are large dynamic oscillations in both the grid-connected active power P e and the output frequency f corresponding to the existing VSG; Second, the grid-connected active power P ehas a similar power overshoot to the existing FOVSG, but the output frequency f corresponding to the existing FOVSG has a larger output frequency overshoot; Third, the output frequency f of the LLC-FOVSG proposed in the present invention has a smaller frequency change rate compared to the existing FOVSG. It can be seen from this that on the one hand, the LLC-FOVSG proposed in the present invention has smaller dynamic oscillations in the grid-connected active power P e and the output frequency f during the process of the grid frequency f g stepping from 50 Hz to 49.95 Hz; on the other hand, the LLC-FOVSG proposed in the present invention has a smaller output frequency overshoot and output frequency change rate compared to the existing FOVSG during the process of the grid frequency f g stepping from 50 Hz to 49.95 Hz.

[0083] After comparing the results of Figure 7 (a) and Figure 6 (a), it is not difficult to see that the experimental test comparison results in Figure 7 (a) of this embodiment can correspond one by one with the simulation test comparison results in Figure 6 (a). Both fully demonstrate that on the one hand, the LLC-FOVSG proposed in the present invention can solve the problem of dynamic oscillations that easily occur in the grid-connected active power P e and the output frequency f of the existing VSG under the step disturbance of the active power reference command P ref ; on the other hand, the LLC-FOVSG proposed in the present invention has the advantages of smaller grid-connected active power overshoot and smaller overshoot amplitude of the output frequency response compared to the existing FOVSG under the step disturbance of the active power reference command P ref . Therefore, compared with the existing VSG and FOVSG, the LLC-FOVSG proposed in the present invention has better control effects.

[0084] After comparing the results of Figure 7 (b) and Figure 6 (b), it is not difficult to see that the experimental test comparison results in Figure 7 (b) of this embodiment can correspond one by one with the simulation test comparison results in Figure 6 (b). Both fully demonstrate that on the one hand, the LLC-FOVSG proposed in the present invention can solve the problem of dynamic oscillations that easily occur in the grid-connected active power P e and the output frequency f of the existing VSG under the step disturbance of the grid frequency f g ; on the other hand, the LLC-FOVSG proposed in the present invention has a smaller output frequency overshoot and output frequency change rate compared to the existing FOVSG under the step disturbance of the grid frequency f gUnder a step disturbance, it has the advantages of a smaller overshoot of the output frequency and a smaller change rate of the output frequency. Therefore, compared with the existing VSG and FOVSG, the LLC-FOVSG proposed in the present invention has better control effects. In summary, the LLC-FOVSG proposed in the present invention can effectively solve the problem that it is difficult to balance the grid-connected active power response performance and the inertia response performance of the existing FOVSG, that is, the LLC-FOVSG proposed in the present invention has a smaller overshoot of the grid-connected active power reference command P compared with the existing FOVSG ref Under a step disturbance, it has a smaller overshoot of the grid-connected active power and an overshoot amplitude of the output frequency response, and at the grid frequency f g Under a step disturbance, it has a smaller overshoot of the output frequency and a change rate of the output frequency.

[0085] The above description is a detailed description of the preferred feasible embodiment of the present invention, but the embodiment is not intended to limit the patent application scope of the present invention. Any equivalent changes or modifications made under the technical spirit disclosed by the present invention shall fall within the patent scope covered by the present invention.

Claims

1. A fractional-order virtual synchronous machine control method based on lead-lag correction, characterized in that: The steps include: Step 1, power calculation part, first collect the output current i of the fractional-order virtual synchronous machine a ,i b ,i c And the output voltage u a ,u b ,u c , the dq component I of the output current oriented by the output phase angle θ of the fractional-order virtual synchronous machine is obtained through single synchronous rotating coordinate transformation d , I q And the dq component of the output voltage U d , U q , and then the grid-connected active power P of the fractional-order virtual synchronous machine is obtained through the power calculation link e and grid-connected reactive power Q e ; Step 2, the primary voltage regulation part, according to the fractional-order virtual synchronous machine grid-connected reactive power Q obtained in step 1 e and the reactive power reference command Q of the fractional-order virtual synchronous machine ref , primary voltage regulation coefficient k q , the voltage reference command E0 of the fractional-order virtual synchronous machine, and the dq-axis output voltage reference command E of the fractional-order virtual synchronous machine is obtained through a voltage regulation control equation d , E q ; Step 3: Based on the rotor motion equation part with lead-lag correction, the fractional-order virtual synchronous machine grid-connected active power P obtained in step 1 is calculated. e and active reference command P ref , virtual inertia coefficient J, fractional-order coefficient μ, virtual damping coefficient D, and rated angular frequency ω0, the angular frequency deviation Δω of the fractional-order virtual synchronous machine is obtained through the rotor motion equation based on lead-lag correction; Step 4, the output phase angle generation part, adds the fractional-order virtual synchronous machine angular frequency deviation Δω obtained in step 3 to the rated angular frequency ω0 to obtain the output angular frequency ω of the fractional-order virtual synchronous machine, and obtains the output phase angle θ of the fractional-order virtual synchronous machine by subjecting the output angular frequency ω to an integral operation link; Step 5: first, according to the fractional-order virtual synchronous machine output phase angle θ obtained in step 4 and the fractional-order virtual synchronous machine dq axis output voltage reference instruction E obtained in step 2, d , E q , the three-phase voltage modulation signal E of the fractional-order virtual synchronous machine is obtained by single synchronous rotating coordinate inverse transformation a , E b , E c , and then the three-phase voltage modulation signal E a , E b , E c The driving signal of the fractional-order virtual synchronous machine switch tube is generated through the SVPWM modulation link.

2. The fractional-order virtual synchronous machine control method based on lead-lag correction according to claim 1, characterized in that: The grid-connected active power P in step 1 c The calculation equation used is: P e =1.5(U d AND d +U q AND q ), Grid-connected reactive power 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 lead-lag correction according to claim 1, characterized in that: The output voltage reference instruction E in step 2 d The calculation equation used is: E d =(Q ref -Q e )k q +E0, Output voltage reference command E q The calculation equation used is: E q ＝0。 4. The fractional-order virtual synchronous machine control method based on lead-lag correction according to claim 1, characterized in that: The calculation equation for the angular frequency deviation Δω in step 3 is: Where T1 is the leading correction coefficient, T2 is the lagging correction coefficient, and s is the Laplace operator.

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

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