A VSG control method based on active dynamic feedforward and fractional order lead correction

Abstract

The application discloses a kind of based on active dynamic feedforward and fractional order advance correction Virtual Synchronous Generator (VSG) control method.The control method improves the rotor motion equation of traditional VSG, that is, high-pass filter is introduced in active feedforward channel, and the rotor angular velocity deviation signal is dynamically compensated by fractional order advance correction link, four control degrees of freedom are introduced, including the time constant of high-pass filter, the two time constants of fractional order advance link and fractional order order, and by flexibly adjusting the above four control degrees of freedom, the dynamic oscillation and overshoot problem of active and output frequency of VSG grid-connected system caused by active reference instruction change or power grid frequency disturbance can be effectively inhibited.The method has the advantages of high control degree of freedom, flexible parameter adjustment, can shorten the output frequency regulation time and effectively reduce the output frequency overshoot, and is suitable for VSG grid-connected control field in power electronics technology.

Description

Technical Field

[0001] This invention relates to the field of Virtual Synchronous Generator (VSG) control technology, and particularly to a VSG control method based on active dynamic feedforward and fractional-order lead correction. It is applicable to the field of VSG grid-connected control in power electronics technology, as well as the field of microgrid grid-connected control that includes this type of VSG. Background Technology

[0002] With the rapid development of wind and solar power, a large number of new energy power electronic devices have been connected to the grid, leading to a decrease in the proportion of traditional synchronous machine power sources. This has resulted in significant changes in the dynamic characteristics of the power system, highlighting the increasingly prominent problems of low disturbance immunity and weak inertia support in the power grid. Against this backdrop, VSG (Variable Voltage Grid) systems, by introducing virtual inertia control and primary voltage regulation, can provide voltage and inertia support to the grid. However, traditional VSG grid-connected systems are prone to dynamic oscillations and overshoot in their active power and output frequency when faced with changes in active power reference commands or grid frequency disturbances. To address these issues, existing research focuses on improving the transient damping and dynamic control performance of the system. However, under conventional control architectures, limitations exist due to insufficient system control degrees of freedom and a lack of dynamic compensation mechanisms for specific channels. Therefore, in recent years, many scholars have conducted further research on traditional VSGs and related improved control strategies, as detailed below:

[0003] For example, in the article titled "VSG Control Strategy Based on Lead-Lag Element with Added Feedforward Damping," published in *High Voltage Engineering*, Vol. 50, No. 1, 2024, pp. 138-147, an improved method based on angular frequency lead-lag with added feedforward is proposed. This method successfully suppresses the dynamic oscillation of the VSG grid-connected system and effectively improves the dynamic response speed by adjusting the time constant of the integer-order lead-lag element and the added feedforward damping gain. However, since this algorithm relies on frequency differentiation, it is prone to introducing high-frequency harmonic interference, which may lead to overshoot in the output frequency. Furthermore, this single integer-order element lacks the multi-degree-of-freedom advantage of fractional calculus, making it difficult to achieve refined compensation for the system's dynamic response.

[0004] To further optimize the feedforward compensation effect, a high-pass filter transient damping control strategy based on active power reference command feedforward was proposed in the article entitled "A referenCe-feedforward-based damping method for virtual synchronous generator control" (IEEE Transactions on Power Electronics, Vol. 37, No. 7, pp. 7566-7571, 2022). This strategy extracts the transient changes of the active power reference command through a high-pass filter for feedforward compensation, effectively suppressing the dynamic oscillations of the VSG grid-connected system. However, this method is still limited to the traditional integer-order control scope in dynamic compensation, lacking a higher-dimensional correction mechanism, resulting in limited freedom of control parameter adjustment, and its parameter design heavily depends on line impedance parameters, thus making it unsuitable for application scenarios where the grid frequency is disturbed.

[0005] Unlike the control methods mentioned above, the introduction of fractional-order theory provides another approach to suppressing VSG power frequency oscillations. On one hand, in the article titled "Virtual Synchronous Generator Control Technology for Fractional-Order Virtual Inertia in Grid-Connected Inverters," published in *Control and Decision*, Vol. 36, No. 2, 2021, pp. 463-468, this paper replaces the integer-order virtual inertia control loop in the VSG with a fractional-order virtual inertia control loop to form a FOVSG. By adjusting the fractional-order integral parameter, it can effectively suppress the dynamic oscillations of grid-connected active power and output frequency. However, it suffers from the drawback of difficulty in simultaneously achieving grid-connected active power response performance and inertia response performance; the system still exhibits grid-connected active power overshoot, and only one new adjustable parameter is added.

[0006] Building upon this foundation, to further enrich the control degrees of freedom of FOVSG, an article titled "Fractional-order virtual synchronous generator," published in IEEE Transactions on Power Electronics, Vol. 38, No. 6, 2023, pp. 6874-6879, introduces a double fractional-order virtual inertia control loop into the FOVSG grid-connected control structure. This scheme can reduce 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 increase the system's control degrees of freedom and the flexibility of control parameter selection. However, its ability to suppress grid-connected active power and output frequency overshoot remains insufficient.

[0007] On the other hand, introducing a fractional-order correction stage can further improve the power frequency dynamic response characteristics of the system. In 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, this paper proposes an optimized control strategy for the active response of VSG grid connection based on active fractional-order differential correction. This strategy effectively solves the problem that VSG grid-connected systems struggle to balance dynamic and steady-state response performance under both active power reference commands and grid frequency disturbances. However, it has limitations such as slow dynamic response speed, limited new control parameters, and inflexible parameter selection.

[0008] As can be seen from the above, existing technologies can provide some basic ideas and technical support for suppressing the dynamic oscillations and overshoot problems of VSG grid-connected active power and output frequency under disturbances such as active power reference command and grid frequency. However, their overall control effect still has considerable room for improvement. Specific areas for improvement include: the limited number of adjustable parameters added, insufficient flexibility in the selection of adjustable parameters, insufficient applicability to application scenarios where grid frequency disturbances occur, and the need to further enhance the ability to suppress grid-connected active power overshoot and output frequency overshoot. Summary of the Invention

[0009] To overcome the limitations of various technical solutions presented in the background art, this invention addresses the problems of insufficient dynamic oscillation suppression and excessive overshoot in VSG grid-connected active power and output frequency when faced with internal and external disturbances such as changes in active power reference commands or grid frequency. It provides a VSG control method based on active power dynamic feedforward and fractional-order lead compensation. This control method introduces a high-pass filter into the active power feedforward channel and combines it with a fractional-order lead compensation stage to dynamically compensate for the rotor angular velocity deviation signal, introducing four degrees of freedom into the system. Through flexible adjustment of these parameters, this method can not only effectively suppress the dynamic oscillations of grid-connected active power and output frequency caused by internal and external disturbances, but also has the advantages of high control freedom and flexible parameter adjustment, significantly shortening the output frequency settling time and effectively reducing frequency overshoot.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A VSG control method based on active power dynamic feedforward and fractional-order lead compensation includes the following steps:

[0012] Step 1, Power Calculation Section: Collect the grid-connected current i of the VSG. a i b i c and output voltage u a u b u cThe dq component I of the output current oriented by the VSG output phase angle θ is obtained through single synchronous rotating coordinate transformation. d I q and the dq component of the output voltage U d U q The grid-connected active power P of the VSG is then obtained through a power calculation process. e and grid-connected reactive power Q e ;

[0013] Step 2, primary voltage regulation section, based on the grid-connected reactive power Q of the VSG obtained in Step 1. e and the reactive power reference command Q of the VSG ref Primary voltage regulation coefficient k q The dq axis output voltage reference command E0 is obtained by applying a voltage adjustment equation to the voltage reference command E0. d E q ;

[0014] Step 3: Based on the rotor motion equation part of the active power dynamic feedforward and fractional-order lead correction, the active power reference command P of the VSG is... ref Subtract the grid-connected active power P of the VSG obtained in step 1 e The power difference ΔP is obtained, and then combined with the virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D of the VSG, and high-pass filter time parameter T. f The angular frequency deviation Δω of the VSG is obtained by taking the lead compensation numerator time constant T1, the lead compensation denominator time constant T2, and the fractional order α through the rotor motion equation.

[0015] Step 4, Output phase angle calculation and generation section: Add the rated angular frequency ω0 to the angular frequency deviation Δω of the VSG obtained in step 3 to obtain the output angular frequency ω of the VSG, and then perform an integration operation on the output angular frequency ω to obtain the output phase angle θ of the VSG;

[0016] Step 5: First, based on the output phase angle θ of the VSG obtained in Step 4, and the dq-axis output voltage reference command E of the VSG obtained in Step 2... d E q The three-phase bridge arm voltage modulation signal E of the VSG is obtained through single-synchronous rotating coordinate inverse transformation. a E b E c Then, the three-phase bridge arm voltage modulated signal E a E b E c The drive signal for the inverter bridge switch of the VSG is generated through the SVPWM modulation stage.

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

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

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

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

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

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

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

[0024] E q =0.

[0025] Preferably, the formula used to calculate the angular frequency deviation Δω in step 3 is:

[0026]

[0027] In the formula, s is the Laplace operator.

[0028] Preferably, the formula used to calculate the output angular frequency ω in step 4 is:

[0029] ω = Δω + ω0,

[0030] The formula for calculating the output phase angle θ is:

[0031]

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

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention discloses a VSG control method based on active power dynamic feedforward and fractional-order lead compensation. This control method improves the rotor motion equation of the traditional VSG by introducing a high-pass filter into the active power feedforward channel and dynamically compensating for the rotor angular velocity deviation signal using a fractional-order lead compensation stage, thereby reconstructing the VSG rotor motion equation. Based on this, the method introduces four control degrees of freedom: a high-pass filter time constant, two time constants of the fractional-order lead stage, and the fractional-order order. By flexibly adjusting these four control degrees of freedom, this invention can effectively suppress the dynamic oscillation and overshoot of active power and output frequency in the VSG grid-connected system caused by changes in active power reference commands or grid frequency disturbances. This method has the advantages of high control degrees of freedom and flexible parameter adjustment, which can further shorten the output frequency adjustment time and effectively reduce output frequency overshoot, making it suitable for VSG grid-connected control in power electronics technology. Attached Figure Description

[0035] Figure 1 This is a diagram of the VSG grid-connected control structure according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram illustrating the calculation of the VSG rotor motion equation according to an embodiment of the present invention.

[0037] Figure 3 This is a diagram of the closed-loop equivalent control structure of the VSG grid-connected active power according to an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram of coordinate transformation and modulation according to an embodiment of the present invention.

[0039] Figure 5 This is a block diagram of the grid-connected active power closed-loop control structure of an existing double fractional-order VSG (DFOVSG).

[0040] Figure 6 This is a Bode plot comparing VSG before and after adopting this invention.

[0041] Figure 7 This is a comparison of the simulation waveforms of VSG before and after adopting this invention.

[0042] Figure 8 This is a comparison of experimental waveforms before and after VSG adopted 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 VSG control method based on active dynamic feedforward and fractional-order lead correction, comprising the following steps:

[0045] Step 1, Power Calculation Section: Collect the grid-connected current i of the VSG. 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 VSG output phase angle θ is obtained through single synchronous rotating coordinate transformation. d I q and the dq component of the output voltage U d U q The grid-connected active power P of the VSG is then obtained through a power calculation process. e and grid-connected reactive power Q e ;

[0046] Among them, the 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, primary voltage regulation section, based on the grid-connected reactive power Q of the VSG obtained in Step 1. e and the reactive power reference command Q of the VSG ref Primary voltage regulation coefficient k q The dq axis output voltage reference command E0 is obtained by applying a voltage adjustment equation to the voltage reference command E0. 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 active dynamic feedforward and fractional-order lead correction, such as... Figure 2 As shown, the active reference command P of the VSG is... ref Subtract the grid-connected active power P of the VSG obtained in step 1 e The power difference ΔP is obtained, and then combined with the virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D of the VSG, and high-pass filter time parameter T. f The angular frequency deviation Δω of the VSG is obtained by taking the lead compensation numerator time constant T1, the lead compensation denominator time constant T2, and the fractional order α through the rotor motion equation.

[0056] That is, the equation used to calculate the angular frequency deviation Δω is:

[0057]

[0058] In the formula, s is the Laplace operator.

[0059] Step 4, Output phase angle calculation and generation section: Add the rated angular frequency ω0 to the angular frequency deviation Δω of the VSG obtained in step 3 to obtain the output angular frequency ω of the VSG, and then perform an integration operation on the output angular frequency ω to obtain the output phase angle θ of the VSG;

[0060] The formula for calculating the output angular frequency ω is as follows:

[0061] ω = Δω + ω0,

[0062] The formula for calculating the output phase angle θ is:

[0063]

[0064] In the formula, s is the Laplace operator.

[0065] Combination Figure 1 Based on the above calculations, the grid-connected active power closed-loop equivalent control structure diagram of the VSG described in this invention can be obtained as follows: Figure 3 As shown. Figure 3 In this context, δ represents the power factor angle; K represents the synchronization voltage coefficient.

[0066] The formula used to calculate the power factor angle δ is as follows:

[0067]

[0068] The formula used to calculate the synchronization voltage coefficient K is:

[0069]

[0070] 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.

[0071] Step 5, as follows Figure 4 As shown, first, based on the output phase angle θ of the VSG obtained in step 4, and the dq-axis output voltage reference command E of the VSG obtained in step 2... d E q The three-phase bridge arm voltage modulation signal E of the VSG is obtained through single-synchronous rotating coordinate inverse transformation. a E b E c Then, the three-phase bridge arm voltage modulated signal E a E b E c The drive signal for the inverter bridge switch of the VSG is generated through the SVPWM modulation stage.

[0072] Example

[0073] To verify the control effect of the proposed VSG grid-connected control method based on active dynamic feedforward and fractional-order lead correction, the proposed VSG control method based on active dynamic feedforward and fractional-order lead correction (hereinafter referred to as HPF-FOLC-VSG) was compared with the existing traditional VSG (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", "Electric Power Automation Equipment", 2024, Vol. 44, No. 2, pp. 204-21). The article on page 0 gives the answer to the question. The existing fractional-order VSG (hereinafter referred to as FOVSG) control method (the FOVSG control method is mentioned in the background technology in the article entitled "Fractional-order virtual synchronous generator control technology for grid-connected inverters", "Control and Decision", Vol. 36, No. 2, 2021, pp. 463-468) and the existing dual fractional-order VSG (hereinafter referred to as DFOVSG) control method (the DFOVSG control method is mentioned in the background technology in the article entitled "Fractional-order virtual synchronous generator", "IEEE Transactions on Power Electronics", 2023, 38(6), 6874-6879, "Fractional-order virtual synchronous generator", "IEEE Power Electronics Journal", Vol. 38, No. 6, 2023, pp. 6874-6879) are compared. Through simulation and experimentation on the grid-connected system using the above four control methods, the main comparison is made in the response to the active power reference command P ref and grid frequency f g Under step disturbance conditions, the grid-connected active power P of each system e And the dynamic response performance at the output frequency f. Specifically:

[0074] First, the relevant parameters are set. In this embodiment, the parameter settings in the HPF-FOLC-VSG control method of the present invention are as follows:

[0075] The VSG has a rated capacity of 100kVA and an active power reference command P. ref It has a power rating of 20 kW, a rated angular frequency ω0 of 314.16 rad / s, and a virtual inertia coefficient J of 8 kg·m. 2 The virtual damping coefficient 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, VSG output voltage amplitude E is 311V, line equivalent inductive reactance X is 0.1Ω, i.e., synchronization voltage coefficient K = 1.5U gE / X = 1450815. The existing active power reference instruction P for a traditional VSG grid-connected system. ref Grid-connected active power P e The closed-loop transfer function is The damping ratio expression for the VSG grid-connected active power closed-loop control system can be derived from G(s) as follows: Substituting the above parameters into the formula, we get ξ = 0.132 << 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 the grid-connected active power P e The closed-loop transfer function is Substitute the above parameters into G1(s) and set the fractional-order coefficient u in G1(s) to 0.6 to ensure the grid-connected active power P of FOVSG. e With output frequency f in active reference command P ref and grid frequency f g No dynamic oscillations occur under step disturbance conditions. Furthermore, based on... Figure 5 The derivation of the control structure shown indicates that the active power reference command P of the existing DFOVSG grid-connected system is... ref To the grid-connected active power P e The closed-loop transfer function is When λ = μ, γ = 0, D1 = D and D2 = 0, DFOVSG can be equivalently replaced by FOVSG, and G2(s) is correspondingly transformed into G1(s). Substituting the above parameters into G2(s) and setting the double fractional order coefficients λ and γ in G2(s) to 0.57 and 0.43 respectively, and the virtual damping coefficients D1 and D2 to 25.6 J / rad and 50.66 J / rad respectively, it is possible to ensure that DFOVSG, FOVSG, and VSG have the same grid-connected active power steady-state response performance, while also suppressing the grid-connected active power P of DFOVSG. e With output frequency f in active reference command P ref and grid frequency f g Dynamic oscillations existing under step disturbances.

[0076] In this embodiment, the high-pass filter time constant T will be optimized. f The values ​​of the time constant T1 in the numerator of the lead compensation, the time constant T2 in the denominator of the lead compensation, and the fractional order α are selected to further optimize the grid-connected active power P of the HPF-FOLC-VSG. eWith 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 HPF-FOLC-VSG grid-connected system can be obtained. ref To the grid-connected active power P e The closed-loop transfer function is Therefore, the grid-connected active power dynamic response performance of VSG, FOVSG, DFOVSG, and HPF-FOLC-VSG can be directly compared and analyzed using the closed-loop transfer functions G(s), G1(s), G2(s), and G3(s). To further simplify the theoretical analysis process, the time constant T of the high-pass filter in HPF-FOLC-VSG is set here. f＝ The time constants of the lead compensation numerator (T1) and denominator (T2) are 0.05 and 0.8, respectively, and the fractional order (α) is 0.8. Substituting these parameters into the closed-loop transfer functions G3(s), G2(s), G1(s), and G(s) respectively, we can obtain the active power reference command step disturbance ΔP for the grid-connected active power closed-loop control systems of HPF-FOLC-VSG, DFOVSG, FOVSG, and VSG. ref Grid-connected active power response ΔP e (ΔP e / ΔP ref For a comparison of the Bode plot, see [link / reference]. Figure 6 (a). Similarly, the grid frequency step disturbance Δω of the grid-connected active power closed-loop control system of HPF-FOLC-VSG, DFOVSG, FOVSG and VSG can be obtained respectively. g 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 grid frequency step disturbance Δω g Output angular frequency response Δω(Δω / Δω) g For comparison with the Bode plot, please refer to the details below. Figure 6 (b) Figure 6 (c) and Figure 6 (d). Among them, Figure 6The curves indicated by VSG in the diagram correspond to the Bode plots of existing traditional VSG control methods; the curves indicated by FOVSG correspond to the Bode plots of existing fractional-order VSG control methods; the curves indicated by DFOVSG correspond to the Bode plots of existing double fractional-order VSG control methods; and the curves indicated by HPF-FOLC-VSG correspond to the Bode plots of the VSG grid-connected control method based on active power dynamic feedforward and fractional-order lead correction proposed in this invention.

[0077] according to Figure 6 It can be seen that: First, the traditional VSG grid-connected active power closed-loop control system exhibits obvious resonance peaks in the low-to-medium frequency range (10–100 rad / s). This phenomenon indicates that the grid-connected active power P of the VSG... e With output frequency f in active reference command P ref and the angular frequency ω of the power grid g Under step disturbance conditions, there are obvious dynamic oscillations and overshoot problems; II. From Figure 6 The frequency domain analysis results of (a) and 6(c) show that, compared with the traditional VSG, the existing FOVSG and DFOVSG have a certain suppression effect on the resonance peak, but they have not completely eliminated it. This phenomenon indicates that the grid-connected active power P of the above two is affected. e With output frequency f in active reference command P ref Under step disturbance conditions, no dynamic oscillations were observed, but a small amount of overshoot remained. Furthermore, no resonance peaks were found in the amplitude-frequency curves of the HPF-FOLC-VSG, and the bandwidth was relatively large. This phenomenon indicates that the grid-connected active power P of the HPF-FOLC-VSG... e With output frequency f in active reference command P ref There is no dynamic oscillation under step disturbance conditions, and while improving the system phase margin, it more effectively suppresses active power overshoot in the FOVSG grid-connected system and has a faster dynamic response speed; III. From Figure 6 The frequency domain analysis results in (b) and 6(d) show that, compared to traditional VSGs, existing FOVSGs and DFOVSGs exhibit a smoother trend in their amplitude-frequency curves. However, significant resonance peaks still exist in the mid-frequency range. This phenomenon indicates that the grid-connected active power P of the above two types of VSGs is relatively stable. e With the output frequency f at the grid angular frequency ω g There is no dynamic oscillation under step disturbance conditions, but its grid-connected active power P e At the grid angular frequency ω g Under step disturbance conditions, a significant overshoot phenomenon is observed. Simultaneously, the HPF-FOLC-VSG grid-connected system exhibits no resonance peaks on its amplitude-frequency curves and possesses a large phase margin. This phenomenon indicates that the grid-connected active power P of the HPF-FOLC-VSG is... e With output frequency f in active reference command P refNo dynamic oscillations or overshoot are observed under step disturbance conditions. It is worth noting that the HPF-FOLC-VSG has more adjustable control parameters compared to VSG and FOVSG. Compared to DFOVSG, HPF-FOLC-VSG not only offers more flexible parameter tuning but also achieves a better balance between control performance and implementation complexity. For example, by selecting appropriate high-pass filter time constants, the two time constants of the fractional-order lead element, and the fractional-order order, the grid-connected active power P of the HPF-FOLC-VSG can be flexibly optimized. e The dynamic response performance with respect to the output frequency f will not be listed in detail due to space limitations.

[0078] Based on the above parameter settings, simulation and experimental comparison tests were conducted, as follows:

[0079] The simulation and experimental test conditions were set as follows: at the initial moment, the VSG stably outputs 20kW of grid-connected active power, and the 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.

[0080] Based on the above working conditions, the following results were obtained: Figure 7 and Figure 8 The simulation and experimental test comparison chart is shown below. Figure 7 Different line types are used for identification. Figure 8 They are identified by numbers 1, 2, 3, 4 and the curves they point to. The specific control methods represented by each identifier are as follows: VSG (i.e., Figure 8 The curve indicated by number 1 corresponds to the dynamic response test waveform of the existing traditional VSG control method; FOVSG (i.e. Figure 8 The curve indicated by number 2 corresponds to the dynamic response test waveform of the existing fractional-order VSG control method; DFOVSG (i.e. Figure 8 The curve indicated by number 3 corresponds to the dynamic response test waveform of the existing double fractional-order VSG control method; HPF-FOLC-VSG (i.e. Figure 8 The curve indicated by reference numeral 4 corresponds to the dynamic response test waveform of the VSG grid-connected control method based on active dynamic feedforward and fractional-order lead correction proposed in this invention.

[0081] according to Figure 7 (a) It can be seen that: 1. The grid-connected active power P corresponding to the HPF-FOLC-VSG proposed in this invention e With no dynamic oscillation or overshoot at the output frequency f, the grid-connected active power P corresponding to a traditional VSG is... eBoth the output frequency f and the FOVSG exhibit significant dynamic oscillations and overshoot. While existing FOVSG and DFOVSG technologies have improved oscillation suppression, they still exhibit noticeable overshoot. II. The grid-connected active power P corresponding to the HPF-FOLC-VSG proposed in this invention... e The power overshoot is 0%, which is less than the 36.5% corresponding to the traditional VSG, the 9.3% corresponding to the existing FOVSG, and the 16.4% corresponding to the existing DFOVSG. Therefore, the HPF-FOLC-VSG proposed in this invention, compared with the traditional VSG, FOVSG, and DFOVSG, has a higher power overshoot under the active power reference command P. ref During the jump from 20kW to 60kW, its grid-connected active power P e No dynamic oscillations or overshoot were observed. Third, the overshoot amplitude of the output frequency f corresponding to the HPF-FOLC-VSG proposed in this invention is 0.044Hz, which is smaller than the 0.073Hz corresponding to the traditional VSG, the 0.149Hz corresponding to the existing FOVSG, and the 0.045Hz corresponding to the DFOVSG. Therefore, compared with the traditional VSG, FOVSG, and DFOVSG, the HPF-FOLC-VSG proposed in this invention exhibits 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 or overshoot, and the output frequency overshoot is relatively small.

[0082] According to Figure 7 (b) It can be observed that: 1. The grid-connected active power P corresponding to the HPF-FOLC-VSG proposed in this invention e With no dynamic oscillation or overshoot at the output frequency f, the grid-connected active power P corresponding to a traditional VSG is... e Both the output frequency f and the FOVSG exhibit significant dynamic oscillations and overshoot. While existing FOVSG and DFOVSG technologies 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 overshoot of the HPF-FOLC-VSG proposed in this invention is 0%, which is less than the 16.5% of the traditional VSG, the 6.3% of the existing FOVSG, and the 10.3% of the existing DFOVSG. Therefore, compared to the traditional VSG, existing FOVSG, and DFOVSG, the HPF-FOLC-VSG proposed in this invention exhibits significant overshoot at the grid frequency f. g During the jump from 50Hz to 49.95Hz, the grid-connected active power P e Both the output frequency f and the frequency f exhibit no dynamic oscillation or overshoot, and the output frequency recovery speed is relatively fast.

[0083] according to Figure 8 (a) It can be observed that in the active reference instruction P refIn the process of jumping from 20kW to 60kW: 1. The grid-connected active power P corresponding to the HPF-FOLC-VSG proposed in this invention e Both the output frequency f and the output frequency f exhibit no dynamic oscillation or overshoot; while traditional VSGs suffer from significant dynamic oscillation and power overshoot. Although existing FOVSGs and DFOVSGs have improved oscillation suppression, they still exhibit considerable overshoot. II. The grid-connected active power P corresponding to the HPF-FOLC-VSG proposed in this invention. e The power overshoot is 0%, which is less than the 37.1% of the traditional VSG, 9.6% of the existing FOVSG, and 17.1% of the existing DFOVSG. Furthermore, the overshoot amplitude of the output frequency f is 0.045Hz, which is less than the 0.074Hz of the traditional VSG, 0.151Hz of the existing FOVSG, and 0.046Hz of the existing DFOVSG. Therefore, compared to the traditional VSG, existing FOVSG, and DFOVSG, the grid-connected active power P of the HPF-FOLC-VSG proposed in this invention is significantly higher. e Both the output frequency f and the output frequency f exhibit no dynamic oscillation or overshoot, and the output frequency overshoot is smaller.

[0084] According to Figure 8 (b) It can be found that at the grid frequency f g During the jump from 50Hz to 49.95Hz: 1. The grid-connected active power P corresponding to the HPF-FOLC-VSG proposed in this invention. e Both the output frequency f and the output frequency f show no dynamic oscillation or overshoot; while traditional VSGs exhibit significant dynamic oscillation and overshoot. Although existing FOVSGs and DFOVSGs 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 overshoot of the HPF-FOLC-VSG proposed in this invention is 0%, which is less than the 16.6% of the traditional VSG, the 6.4% of the existing FOVSG, and the 10.4% of the DFOVSG. Therefore, compared to the traditional VSG, the existing FOVSG, and the DFOVSG, the grid-connected active power P of the HPF-FOLC-VSG proposed in this invention... e There is no dynamic oscillation or overshoot at the output frequency f.

[0085] Depend on Figure 8 (a) and Figure 7 As can be seen from the comparison of results in (a), in this embodiment... Figure 8 (a) Experimental test results and Figure 7 (a) The simulation test results show a one-to-one correspondence, and both results fully demonstrate that: compared with the traditional VSG, the existing FOVSG and DFOVSG, the HPF-FOLC-VSG proposed in this invention has a higher performance in active power reference command P.ref During a step disturbance, the grid-connected active power P e Both the output frequency f and the output frequency exhibit no dynamic oscillation or overshoot, and the output frequency overshoot is small. Therefore, compared with the three existing methods mentioned above, the HPF-FOLC-VSG proposed in this invention has better control performance.

[0086] And again Figure 8 (b) and Figure 7 After comparing the results in (b), it is not difficult to see that in this embodiment... Figure 8 (b) Experimental test results and Figure 7 (b) The simulation test results show a one-to-one correspondence, and both results fully demonstrate that: compared with traditional VSG, existing FOVSG and DFOVSG, the HPF-FOLC-VSG proposed in this invention has a higher voltage drop frequency than the grid frequency f. g During a step disturbance, the grid-connected active power P e There is no dynamic oscillation or overshoot at the output frequency f. Therefore, compared with the three existing methods mentioned above, the HPF-FOLC-VSG proposed in this invention has better control performance.

[0087] 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 VSG control method based on active power dynamic feedforward and fractional-order lead compensation, characterized in that, Includes the following steps: Step 1, Power Calculation Section: Collect the grid-connected current i of the VSG. 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 output phase angle θ of the VSG is obtained through a single synchronous rotating coordinate transformation. d I q and the dq component of the output voltage U d U q The grid-connected active power P obtained after the power calculation process e and grid-connected reactive power Q e ; Step 2, primary voltage regulation section, based on the grid-connected reactive power Q of the VSG obtained in Step 1. e and the reactive power reference command Q of the VSG ref Primary voltage regulation coefficient k q The dq axis output voltage reference command E0 is obtained by applying a voltage adjustment equation to the voltage reference command E0. d E q ; Step 3, Rotor Motion Equation Part: The active power reference command P of the VSG is... ref Subtract the grid-connected active power P of the VSG obtained in step 1 e The power difference ΔP is obtained, and then combined with the virtual inertia coefficient J, rated angular frequency ω0, virtual damping coefficient D of the VSG, and high-pass filter time parameter T. f The angular frequency deviation Δω of the VSG is obtained by taking the lead compensation numerator time constant T1, the lead compensation denominator time constant T2, and the fractional order α through the rotor motion equation. Step 4, Output phase angle calculation and generation section: Add the rated angular frequency ω0 to the angular frequency deviation Δω of the VSG obtained in step 3 to obtain the output angular frequency ω of the VSG, and then perform an integration operation on the output angular frequency ω to obtain the output phase angle θ of the VSG; Step 5: First, based on the output phase angle θ of the VSG obtained in Step 4, and the dq-axis output voltage reference command E of the VSG obtained in Step 2... d E q The three-phase bridge arm voltage modulation signal E of the VSG is obtained through single-synchronous rotating coordinate inverse transformation. a E b E c Then, the three-phase bridge arm voltage modulated signal E a E b E c The drive signal for the inverter bridge switch of the VSG is generated through the SVPWM modulation stage.

2. The VSG control method 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 ), The formula for calculating the grid-connected reactive power Qe is: Q e =1.5(U q I d -U d I q )。 3. The VSG control method according to claim 1, characterized in that, Output voltage reference command E in step 2 d The calculation formula used is: E d <E0+(Q ref -Q e )k q , Output voltage reference command E q The calculation formula used is: E q ＝0。 4. The VSG control method according to claim 1, characterized in that, The equation used for the angular frequency deviation Δω in step 3 is: In the formula, s is the Laplace operator.

5. The VSG control method 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.

Images