A Virtual Synchronous Machine-Based Active Power Optimization Method Based on Frequency Feedforward Compensation

Abstract

This invention discloses a method for optimizing the active power of a virtual synchronous machine connected to the grid based on frequency feedforward compensation. This optimization method, based on the traditional equivalent control block diagram of the active power of a virtual synchronous machine connected to the grid, improves the transient damping of the virtual synchronous machine and its ability to suppress dynamic oscillations of the active power during grid connection by adding a frequency feedforward compensation stage. It solves the problem that the dynamic characteristics of the active power during grid connection and the primary frequency regulation characteristics cannot be simultaneously considered in the process of providing a certain amount of virtual inertia support to the grid during the operation of a traditional virtual synchronous machine connected to the grid. It also has the advantages of not affecting the primary frequency regulation characteristics, simple control parameter design, not increasing the order of the control system, and avoiding overshoot in the output frequency. It is applicable to the field of virtual synchronous machine grid connection control in power electronics technology.

Description

Technical Field

[0001] This invention relates to the field of virtual synchronous machine control technology, and in particular to a method for optimizing the active power of a virtual synchronous machine connected to the grid based on frequency feedforward compensation, applicable to the field of virtual synchronous machine grid-connected control in power electronics technology. Background Technology

[0002] The virtual inertia control element of a traditional virtual synchronous machine transforms its active power-frequency closed-loop control system into a typical second-order oscillatory system. Therefore, its grid-connected active power inevitably exhibits dynamic oscillations and power overshoot under active power reference command disturbances. Furthermore, increasing the primary frequency regulation coefficient can enhance the suppression of dynamic oscillations in the grid-connected active power of a traditional virtual synchronous machine, but it also affects the primary frequency regulation characteristics of the system's active power-frequency response. Therefore, directly adjusting the virtual inertia coefficient and primary parameter coefficients makes it difficult to guarantee that the grid-connected active power of a traditional virtual synchronous machine possesses both good dynamic characteristics and steady-state performance.

[0003] To this end, various studies have been conducted, such as the article entitled "An improved virtual inertia algorithm of virtual synchronous generator", XU HZ, YU CZ, LIU C, et al, Journal of Modern Power Systems and Clean Energy, 2019, 8(2), 377–386 (“An improved virtual inertia algorithm of virtual synchronous generator”, Journal of Modern Power Systems and Clean Energy, 2019, Vol. 8, No. 2, pp. 377–386). This article proposes to increase the equivalent damping of the virtual synchronous generator grid-connected system by introducing a first-order differential feedforward compensation link of grid-connected active power and angular frequency in the traditional equivalent control structure of the grid-connected active power of the virtual synchronous generator. This can effectively suppress the dynamic oscillation of the grid-connected active power of the virtual synchronous generator. However, the differential operation will also introduce high-frequency harmonics that affect the stable operation of the grid-connected system of the virtual synchronous generator.

[0004] The article, titled "d-axis current differential feedforward control for optimizing the dynamic characteristics of energy storage VSG," published in *Power System Technology*, Vol. 46, No. 07, 2022, pp. 2510-2523, proposes a transient damping control scheme that incorporates the first-order differential of the active current of the virtual synchronous machine (VSM) plus a first-order low-pass filter feedforward link into the VSM active-frequency control loop. This scheme effectively suppresses the dynamic oscillations of the VSM's grid-connected active current and eliminates the adverse effects of high-frequency harmonics introduced by the differential operation on the system. However, the first-order low-pass filter increases the order of the VSM grid-connected active current closed-loop system to the third order, which leads to increased difficulty in system parameter design and output frequency overshoot.

[0005] The article, titled "VSG Control Strategy Introducing Transient Electromagnetic Power Compensation," published in *Power System Technology*, Vol. 46, No. 04, 2022, pp. 1421-1429, proposes a grid-connected active power dynamic oscillation suppression strategy based on Power Feedforward Compensation-Virtual Synchronous Generator (PFC-VSG). This PFC-VSG control strategy improves the transient damping of the grid-connected virtual synchronous generator system by using the difference operation of the first-order lag element of electromagnetic power, avoiding the differential operation element. However, the order of the grid-connected active power closed-loop system of the virtual synchronous generator is still third-order, and there is a risk of overshoot in the output frequency of the virtual synchronous generator under the active power reference command step.

[0006] The article, titled “A reference-feedforward-based damping method for virtual synchronous generator control”, by YUY, CHAUDHARY SK, TINAJERO GDA, et al., IEEE Transactions on Power Electronics, 2022, 37(7), 7566–7571 (“Virtual Synchronous Generator Damping Control Strategy Based on Active Reference Command Feedforward”, IEEE Journal of Power Electronics, 2022, Vol. 37, No. 7, pp. 7566–7571), proposes a transient damping control strategy based on active reference command differential feedforward. It designs the grid-connected active closed-loop system of the virtual synchronous generator as a typical second-order system, which has the advantage of intuitive system control parameter design. However, it does not consider the response performance of the virtual synchronous generator output frequency under active reference command disturbance.

[0007] As can be seen from the above, although the existing technology has solved the problems of power overshoot and dynamic oscillation in the grid-connected active power of traditional virtual synchronous machines under active power reference command disturbance conditions, there are still problems such as harmonic amplification caused by differential operation, difficulty in designing control parameters due to the increase in system order, and risk of overshoot in output frequency. Summary of the Invention

[0008] In view of the above, it is necessary to provide a method for optimizing the grid-connected active power of a virtual synchronous machine based on frequency feedforward compensation, so as to solve the problem that it is difficult to balance the grid-connected active power dynamic characteristics and primary frequency regulation characteristics of traditional virtual synchronous machines. This optimization method can effectively eliminate the grid-connected active power dynamic oscillation of the virtual synchronous machine, without affecting the primary frequency regulation characteristics, without the risk of output frequency overshoot, without the need for differential calculations and without increasing the order of the control system, and has a fast response and good control effect.

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

[0010] A method for optimizing the active power of a virtual synchronous machine connected to the grid based on frequency feedforward compensation is characterized by the following main steps:

[0011] Step 1, the primary frequency modulation control section, sets the output angular frequency ω of the virtual synchronizer to... s Subtracting the rated angular frequency ω0 of the power grid, the frequency difference Δω is obtained and used as the input for primary frequency regulation control. The frequency difference Δω is then processed by the primary frequency regulation coefficient D. p The active power regulation P of the primary frequency regulation control is obtained by multiplying the product of the power grid's rated angular frequency ω0 and the proportional element. d ;

[0012] Step 2, Virtual Inertia Control Section, converts the active power reference command P of the virtual synchronous machine... ref Subtract the grid-connected active power P of the virtual synchronous machine e The active power regulation P obtained in step 1 for primary frequency regulation control d Then, after passing through a virtual inertia control loop that includes the virtual inertia coefficient J and the grid's rated angular frequency ω0, the output angular frequency ω of the virtual synchronizer is obtained. s ;

[0013] Step 3, calculate the feedforward compensation amount, and pass the grid rated angular frequency ω0 through the active power reference command P. ref Virtual inertia coefficient J, primary frequency modulation coefficient D p Frequency feedforward compensation element G with the rated angular frequency ω0 of the power grid F (s) then yields the compensation amount ω for feedforward compensation control. c ;

[0014] Step 4, the output angular frequency ω of the virtual synchronizer obtained in Step 2 is... s Add the compensation amount ω obtained in step 3 for feedforward compensation control c The sum of the angular frequencies ω of the two is then obtained. m The sum of angular frequencies ω m Subtract the grid angular frequency ω g The power factor angle δ of the virtual synchronous machine is then obtained through integration.

[0015] Step 5: Multiply the power factor angle δ of the virtual synchronous machine obtained in Step 4 by the synchronization voltage coefficient K to obtain the grid-connected active power P of the virtual synchronous machine. e ;

[0016] Step 6, sum the angular frequencies ω obtained in Step 4. mThe output phase θ of the virtual synchronizer is obtained through integration. This output phase θ is used as the phase for dq coordinate transformation to obtain the voltage reference command E in the dq coordinate system for the reactive power control loop. * dq The three-phase voltage modulation signal E in the abc coordinate system is obtained by performing a dq coordinate transformation. * abc Then, the three-phase voltage modulation signal E * abc The drive signals for the inverter bridge switching transistors of the converter are generated through the SVPWM modulation stage.

[0017] Preferably, the formula used to calculate the frequency difference Δω in step 1 is:

[0018] Δω=ω s -ω0,

[0019] Active power regulation P of primary frequency control d The calculation formula used is:

[0020] P d =D p ω0Δω=D p ω0(ω s -ω0).

[0021] Preferably, the output angular frequency ω of the virtual synchronizer in step 2 s The calculation formula used is:

[0022]

[0023] In the formula, s is the Laplace operator.

[0024] Preferably, the compensation amount ω in the feedforward compensation control in step 3 is... c The calculation formula used is:

[0025] ω c =G F (s)ω0,

[0026] The frequency feedforward compensation stage G F The formula used to calculate (s) is:

[0027]

[0028] The expressions for m1, m2, n1, and n2 are as follows:

[0029]

[0030] In the formula, U g Here, E represents the grid voltage amplitude, E represents the output voltage amplitude of the virtual synchronous machine, and X represents the line equivalent inductive reactance. Let K = 1.5U be the natural oscillation angular frequency of the virtual synchronizer. g E / X is the synchronization voltage coefficient. Let be the damping ratio of the virtual synchronizer, and s be the Laplace operator.

[0031] Preferably, the sum of angular frequencies ω in step 4 m The calculation formula used is:

[0032] ω m =ω s +ω c ,

[0033] The formula for calculating the power factor angle δ of a virtual synchronizer is:

[0034]

[0035] In the formula, s is the Laplace operator.

[0036] Preferably, the grid-connected active power P of the virtual synchronous machine in step 5 e The calculation formula used is:

[0037]

[0038] In the formula, U g E is the voltage amplitude of the grid, E is the voltage amplitude of the virtual synchronous machine output, and X is the equivalent inductive reactance of the line.

[0039] Preferably, the formula used to calculate the output phase θ of the virtual synchronizer in step 6 is:

[0040]

[0041] In the formula, s is the Laplace operator.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention provides a method for optimizing the active power of a virtual synchronous machine grid-connected system based on frequency feedforward compensation. This optimization method improves the transient damping of the virtual synchronous machine grid-connected system and its ability to suppress dynamic oscillations of the grid-connected active power by adding a frequency feedforward compensation stage, based on the traditional equivalent control block diagram of the virtual synchronous machine grid-connected system. This method has the advantages of not affecting the primary frequency regulation characteristics, simple control parameter design, not increasing the order of the control system, and avoiding overshoot of the output frequency. It can be applied to the field of virtual synchronous machine grid-connected control in power electronics technology. Attached Figure Description

[0044] Figure 1 This is an equivalent control structure diagram of the virtual synchronous machine grid-connected active power closed loop according to an embodiment of the present invention.

[0045] Figure 2 This is a schematic diagram illustrating the calculation of the compensation amount in feedforward compensation control.

[0046] Figure 3 This is a schematic diagram of coordinate transformation and modulation according to an embodiment of the present invention.

[0047] Figure 4 This is a comparison of the simulation waveforms of the virtual synchronizer before and after adopting this invention.

[0048] Figure 5 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] See Figure 1 The present invention proposes a method for optimizing the active power of a virtual synchronous machine based on frequency feedforward compensation, characterized by the following main steps:

[0051] Step 1, the primary frequency modulation control section, sets the output angular frequency ω of the virtual synchronizer to... s Subtracting the rated angular frequency ω0 of the power grid, the frequency difference Δω is obtained and used as the input for primary frequency regulation control. The frequency difference Δω is then processed by the primary frequency regulation coefficient D. p The active power regulation P of the primary frequency regulation control is obtained by multiplying the product of the power grid's rated angular frequency ω0 and the proportional element. d .

[0052] The formula used to calculate the frequency difference Δω is as follows:

[0053] Δω=ω s -ω0,

[0054] Active power regulation P of primary frequency control d The calculation formula used is:

[0055] P d =D p ω0Δω=D p ω0(ω s -ω0).

[0056] Step 2, Virtual Inertia Control Section, converts the active power reference command P of the virtual synchronous machine... ref Subtract the grid-connected active power P of the virtual synchronous machine e The active power regulation P obtained in step 1 for primary frequency regulation control d Then, after passing through a virtual inertia control loop that includes the virtual inertia coefficient J and the grid's rated angular frequency ω0, the output angular frequency ω of the virtual synchronizer is obtained. s .

[0057] The output angular frequency ω of the virtual synchronizer. s The calculation formula used is:

[0058]

[0059] In the formula, s is the Laplace operator.

[0060] Step 3, calculate the feedforward compensation amount, such as Figure 2 As shown, the rated angular frequency ω0 of the power grid is passed through a circuit containing the active power reference command P. ref Virtual inertia coefficient J, primary frequency modulation coefficient D p Frequency feedforward compensation element G with the rated angular frequency ω0 of the power grid F (s) then yields the compensation amount ω for feedforward compensation control. c .

[0061] Among them, the compensation amount ω of feedforward compensation control c The calculation formula used is:

[0062] ω c =G F (s)ω0,

[0063] The frequency feedforward compensation stage G F The formula used to calculate (s) is:

[0064]

[0065] The expressions for m1, m2, n1, and n2 are as follows:

[0066]

[0067] In the formula, U g Here, E represents the grid voltage amplitude, E represents the output voltage amplitude of the virtual synchronous machine, and X represents the line equivalent inductive reactance. Let K = 1.5U be the natural oscillation angular frequency of the virtual synchronizer. g E / X is the synchronization voltage coefficient. Let be the damping ratio of the virtual synchronizer, and s be the Laplace operator.

[0068] Step 4, the output angular frequency ω of the virtual synchronizer obtained in Step 2 is... s Add the compensation amount ω obtained in step 3 for feedforward compensation control c The sum of the angular frequencies ω of the two is then obtained. m The sum of angular frequencies ω m Subtract the grid angular frequency ω g The power factor angle δ of the virtual synchronizer is then obtained through integration.

[0069] Among them, the sum of angular frequencies ω m The calculation formula used is:

[0070] ω m =ω s +ω c ,

[0071] The formula for calculating the power factor angle δ of a virtual synchronizer is:

[0072]

[0073] In the formula, s is the Laplace operator.

[0074] Step 5: Multiply the power factor angle δ of the virtual synchronous machine obtained in Step 4 by the synchronization voltage coefficient K to obtain the grid-connected active power P of the virtual synchronous machine. e .

[0075] Among them, the grid-connected active power P of the virtual synchronous machine e The calculation formula used is:

[0076]

[0077] In the formula, U g E is the voltage amplitude of the grid, E is the voltage amplitude of the virtual synchronous machine output, and X is the equivalent inductive reactance of the line.

[0078] Step 6, as follows Figure 3 As shown, the sum of the angular frequencies ω obtained in step 4 is... m The output phase θ of the virtual synchronizer is obtained through integration. This output phase θ is used as the phase for dq coordinate transformation to obtain the voltage reference command E in the dq coordinate system for the reactive power control loop. * dq The three-phase voltage modulation signal E in the abc coordinate system is obtained by performing a dq coordinate transformation. * abc Then, the three-phase voltage modulation signal E * abc The drive signals for the inverter bridge switching transistors of the converter are generated through the SVPWM modulation stage.

[0079] The formula for calculating the output phase θ of the virtual synchronizer is as follows:

[0080]

[0081] In the formula, s is the Laplace operator.

[0082] Example

[0083] To verify the control effect of the proposed active power optimization method based on frequency feedforward compensation virtual synchronous machine (hereinafter referred to as FFC-VSG) for grid connection, this embodiment compares the proposed FFC-VSG active power optimization method with an existing active power dynamic oscillation suppression method based on electromagnetic power feedforward compensation virtual synchronous machine (hereinafter referred to as PFC-VSG) (this suppression method is mentioned in the background art in the article entitled "VSG Control Strategy Introducing Transient Electromagnetic Power Compensation", Vol. 46, No. 04, pp. 1421-1429, "Power System Technology", 2022) through simulation and experiments. The main comparison is in response to the active power reference command P ref Grid-connected active power P under step disturbance conditions e And its dynamic response performance at the output frequency.

[0084] In this embodiment, the relevant parameter settings are as follows:

[0085] The virtual synchronous machine has a rated capacity of 100kVA and an active power reference command P. ref The power supply is 20kW, the grid's rated angular frequency ω0 is 314.16 rad / s, and the virtual inertia coefficient J is 2.5 kg·m. 2 The primary frequency modulation coefficient D p It is 50.66 J / rad, and the grid voltage amplitude U g Given a voltage of 311V, a virtual synchronous machine output voltage amplitude E of 311V, and a line equivalent inductive reactance X of 0.1Ω, then the synchronization voltage coefficient K = 1.5U. g The E / X value is 1450815.

[0086] It is worth noting that, on the one hand, the closed-loop equivalent control system for the grid-connected active power of the virtual synchronous machine is set as a critically damped or overdamped system to ensure that the grid-connected active power of the virtual synchronous machine is within the active power reference command P. ref Under step disturbances, there is neither dynamic oscillation nor power overshoot; on the other hand, the virtual synchronous machine grid-connected active power equivalent closed-loop control system has a relatively large control bandwidth to ensure that the grid-connected active power of the virtual synchronous machine is within the active power reference command P. ref It still exhibits good dynamic response performance under step disturbances; therefore, in this embodiment, the damping ratio ξ and its natural oscillation angular frequency ω of the virtual synchronizer are used. n The values ​​were set to 1 and 35.1 rad / s respectively, and the control parameters of the proposed method for optimizing the active power of a virtual synchronous machine based on frequency feedforward compensation were then tuned.

[0087] Based on the above parameter settings, simulation and experimental comparison tests were conducted, as follows:

[0088] The simulation and experimental test conditions were set as follows: at the initial moment, the virtual synchronous machine stably outputs 20kW of grid-connected active power, and at 4s, the active power reference command P...ref The power output jumped from 20kW to 60kW.

[0089] Based on the above working conditions, the following results were obtained: Figure 4 and Figure 5 The simulation and experimental test comparison chart shown below. Figure 4 , Figure 5 In this invention, FFC-VSG represents the active power optimization method for grid-connected virtual synchronous machines based on frequency feedforward compensation, and PFC-VSG represents the existing active power dynamic oscillation suppression method for grid-connected virtual synchronous machines based on active power transient feedforward compensation. Specifically, the curve pointed to by PFC-VSG is the test waveform before the application of this invention, and specifically, the dynamic response test waveform of the existing active power dynamic oscillation suppression method for grid-connected virtual synchronous machines based on active power transient feedforward compensation. The curve pointed to by FFC-VSG is the test waveform after the application of this invention, and specifically, the dynamic response test waveform of the proposed active power optimization method for grid-connected virtual synchronous machines based on frequency feedforward compensation.

[0090] according to Figure 4 It can be seen that the active power of existing PFC-VSG and the FFC-VSG proposed in this invention is based on the active power reference command P. ref There was no dynamic oscillation or power overshoot during the jump from 20kW to 60kW. However, the overshoot amplitude of the virtual synchronous machine output frequency corresponding to the existing PFC-VSG is 0.27Hz, which is much higher than the 0.04Hz corresponding to the FFC-VSG proposed in this invention.

[0091] And from Figure 5 It can be concluded that both the existing PFC-VSG and the FFC-VSG proposed in this invention can effectively suppress the virtual synchronizer in the active power reference instruction P. ref Dynamic oscillation under step disturbance, but the overshoot amplitude of the virtual synchronous machine output frequency corresponding to the existing PFC-VSG is 0.32Hz, which is much higher than the 0.05Hz corresponding to the FFC-VSG proposed in this invention.

[0092] Will Figure 5 and Figure 4 A comparison of the results clearly shows that this implementation method... Figure 5 The experimental test results were compared with Figure 4 The simulation test results show a one-to-one correspondence, both fully demonstrating that the FFC-VSG proposed in this invention can effectively avoid the risk of output frequency overshoot present in existing PFC-VSGs. Therefore, the FFC-VSG proposed in this invention can effectively avoid the risk of output frequency overshoot in the active power reference command P. ref It exhibits superior frequency dynamic response performance under step disturbances.

[0093] 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 method for active power optimization of a virtual synchronous machine based on frequency feed-forward compensation, characterized in that, Mainly includes the following steps: Step 1, primary frequency control part, subtract the rated angular frequency ω0 of the power grid from the output angular frequency ω of the virtual synchronous machine to obtain the frequency difference Δω of the two as the input quantity of the primary frequency control, and multiply the frequency difference Δω by the primary frequency coefficient D s to obtain the active regulation quantity P of the primary frequency control after passing through the proportional link constituted by the primary frequency coefficient D p and the rated angular frequency ω0 of the power grid d ; Step 2, virtual inertia control part, subtracting the grid-connected active power P of the virtual synchronous machine ref from the active reference instruction P of the virtual synchronous machine e and the active regulation amount P of the primary frequency modulation control obtained in step 1 d , and then passing through a virtual inertia control link containing a virtual inertia coefficient J and a grid rated angular frequency ω0 to obtain the output angular frequency ω of the virtual synchronous machine s ; Step 3, feedforward compensation amount calculation, the grid rated angular frequency ω0 through the active reference instruction P ref , virtual inertia coefficient J, primary frequency modulation coefficient D p and the grid rated angular frequency ω0 frequency feedforward compensation element G F (s) after the feedforward compensation control compensation amount ω c ; Step 4, the output angular frequency ω of the virtual synchronous machine obtained in Step 2 is added to the compensation amount ω of the feedforward compensation control obtained in Step 3 s to obtain the sum ω of the angular frequencies of both c Step 5, the sum ω of the angular frequencies is multiplied by the angular frequency ω of the power grid m to obtain the power factor angle δ of the virtual synchronous machine m Step 6, the power factor angle δ of the virtual synchronous machine is subtracted from the angular frequency ω of the power grid g to obtain the power factor angle δ of the virtual synchronous machine after the integral operation Step 5, multiply the power factor angle δ of the virtual synchronous machine obtained in step 4 by the synchronous voltage coefficient K to obtain the grid-connected active power P of the virtual synchronous machine e ; Step 6, the sum of the angular frequency ω m The output phase θ of the virtual synchronous machine is obtained through integral operation, and the output phase θ is used as the phase for dq coordinate transformation, so as to obtain the voltage reference instruction E in the dq coordinate system for the reactive power control loop * dq The three-phase voltage modulation signal E in the abc coordinate system is obtained through dq coordinate transformation * abc The three-phase voltage modulation signal E in the abc coordinate system is obtained through dq coordinate transformation * abc The drive signal of the inverter bridge switch tube is generated through the SVPWM modulation link.

2. The frequency feed-forward compensation based virtual synchronous machine grid- connected active power optimization method according to claim 1, characterized in that, The calculation formula of the frequency difference delta omega in step 1 is: Δω = ω s - ω0, The active regulation amount P of the primary frequency control d The calculation formula used is: P d = D p ω0Δω = D p ω0(ω s -ω0).

3. The frequency feed-forward compensation based virtual synchronous machine grid- connected active power optimization method according to claim 1, characterized in that, The output angular frequency ω of the virtual synchronous machine in step 2 s The used calculation formula is: In the formula, s is Laplace operator.

4. The frequency feed forward compensation based virtual synchronous machine grid- connected active power optimization method according to claim 1, characterized in that, The compensation amount ω of the feedforward compensation control in step 3 c The calculation formula used is: ω c = G F (s) ω0, And the frequency feed-forward compensation link G F The calculation formula used is: Wherein, the expression of m1, m2, n1, n2 is respectively: wherein U g is the grid voltage amplitude, E is the VSM output voltage amplitude, X is the line equivalent inductance, is the natural oscillation angular frequency of the VSM, K = 1.5U g E / X is the synchronous voltage coefficient, is the damping ratio of the VSM, s is the Laplace operator.

5. The frequency feed forward compensation based virtual synchronous machine grid- connected active power optimization method according to claim 1, characterized in that, The sum of the angular frequencies in step 4 ω m The formula used is: ω m = ω s + ω c , The calculation formula of the power factor angle delta of the virtual synchronous machine is: In the formula, s is Laplace operator.

6. The frequency feed forward compensation based virtual synchronous machine grid-tie active power optimization method according to claim 1, wherein, Step 5: The virtual synchronous machine's grid-connected active power P e The calculation formula used is: In the formula, U g is the grid voltage amplitude, E is the virtual synchronous machine output voltage amplitude, and X is the line equivalent inductance.

7. The frequency feed forward compensation based virtual synchronous machine grid-tie active power optimization method according to claim 1, wherein, The calculation formula of the output phase theta of the virtual synchronous machine in step 6 is: In the formula, s is Laplace operator.

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