Virtual synchronous machine active low-frequency oscillation suppression method based on power feedback compensation

Abstract

The invention discloses a virtual synchronous machine active low-frequency oscillation suppression method based on power feedback compensation, and belongs to the field of new energy grid-connected converter control under large-scale new energy access. According to the method, the output voltage and current of the new energy converter are sampled, the instantaneous output active power and reactive power are calculated, and the average output active power and reactive power are obtained through a first-order low-pass filter; and then virtual synchronous machine active outer loop control based on output power feedback compensation and reactive outer loop control based on reactive-voltage droop are adopted to obtain reference values of a d-axis voltage amplitude and a voltage phase angle of new energy converter voltage inner loop control, and output voltage closed loop control is carried out. Under the condition that the output active control order and the steady-state characteristic are not increased, the output active dynamic overshoot and low-frequency oscillation suppression of the new energy converter based on the network construction control type virtual synchronous machine are effectively realized, the parameter value range is slightly constrained by the system stability, and the engineering application is simple.

Description

Technical Field

[0001] The present invention belongs to the field of new energy grid-connected converter control under large-scale new energy access, and specifically relates to a method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation. Background Art

[0002] In recent years, renewable energy power generation has gradually become the main power source of the power system. With the large-scale access of renewable energy, the power grid has gradually shown the weak grid characteristics of "low short-circuit ratio and low inertia". Conventional current-controlled grid-connected converters are difficult to operate stably under weak grids. In order to improve the system stability and equivalent synchronous inertia under weak grids, the voltage-controlled virtual synchronous machine strategy has received close attention and in-depth research from experts and scholars at home and abroad, and has been widely used in demonstration projects at home and abroad. Although the virtual synchronous machine strategy adopted by the new energy converter can achieve stable operation under weak grids and improve the synchronous inertia of the system, it also causes problems similar to the low-frequency oscillation of the active power of synchronous generators. The main reason is that when the new energy converter based on the conventional voltage-controlled virtual synchronous machine strategy is connected to the grid, its output active closed-loop control is a typical second-order system. In order to improve the synchronous inertia of the system and reduce the frequency change rate of the system under load disturbance, the virtual inertia in the virtual synchronous machine strategy cannot be set too small, which leads to a decrease in the system damping ratio. The second-order system is an underdamped system with serious active overshoot and oscillation.

[0003] Adding a damping term with a fixed damping coefficient in the virtual synchronous machine control to simulate the damping winding characteristics can reduce power overshoot and suppress power oscillation, but the fixed damping coefficient can lead to an increase in the output active power deviation of the new energy converter when the grid angular frequency deviates from the rated angular frequency of the system. In addition, since the fixed damping coefficient and the primary frequency modulation coefficient are coupled and superimposed to jointly affect the active-frequency droop characteristics, and the frequency offset under the droop effect is restricted by relevant standards and should not be too large, the adjustment range of the fixed damping coefficient is greatly limited. Therefore, the active overshoot and low-frequency oscillation suppression method based on the fixed damping coefficient is difficult to meet the steady-state and dynamic characteristics of active power regulation requirements.

[0004] At present, in order to enhance the damping and suppress the active low-frequency oscillation of the voltage-controlled virtual synchronous machine strategy, many papers and patents at home and abroad have proposed transient damping solutions, which improve the output active closed-loop control damping by feedforward or feedback compensation of the active power of the new energy converter without affecting its steady-state output characteristics, thereby achieving decoupling and independent adjustment of the damping control. For example:

[0005] 1. Lan Zheng, Long Yang, Zeng Jinhui, Tu Chunming, Xiao Fan, Guo Qi, “Transient Power Oscillation Suppression Strategy of Virtual Synchronous Generator Considering Overshoot”, Automation of Electric Power Systems, Vol. 46, No. 11, 2022, pp. 131-141; Jiang Shiming, Tang Jie, “Improved VSG Control Strategy Based on Transient Damping Enhancement”, Power System Protection and Control, Vol. 51, No. 19, 2023, pp. 144-154; and Zhengguo Piao, Dingding Fei, Changbin Hu, Shanna Luo, Lianming Jing, Aliev Sukhrab, 2024IEEE 2nd International Conference on Power Science and Technology Technology", 2024, 276-281 ("Improved transient damping control strategy for virtual synchronous machine for improving grid voltage support capability", "2024 IEEE Second International Conference on Electric Power Science and Technology", 2024 Conference Proceedings, pp. 276-281), transient damping control is achieved by correcting the output active power and output active power deviation of the virtual synchronous machine through the lead-lag link and then performing feedforward compensation, and correcting the output angular frequency of the virtual synchronous machine through the lead-lag link and then performing feedback compensation. However, the transient damping scheme based on lead-lag link correction and compensation increases the closed-loop control order of the virtual synchronous machine output active power, and the lead-lag link coefficients are relatively large, making the control and parameter design more complicated. In addition, affected by the limitations of parameter design, the output active power of the virtual synchronous machine based on the above transient damping scheme is prone to overshoot.

[0006] 2. In the article entitled “A Self-Adaptive Inertia and Damping Combination Control of VSG to Support Frequency Stability” by D. Li, Q. Zhu, S. Lin and X. Y. Bian., IEEE Transactions on Energy Conversion, 2017, 32(1): 397-398 and the article entitled “Analysis of the Influence of Main Control Parameters of Flexible Virtual Synchronous Machine on System Frequency Stability” by Zou Peigen, Meng Jianhui, Wang Yi and Lei Xi, High Voltage Technology, 2018, 44, No. 04, 1335-1342, the virtual inertia and damping coefficient in the virtual synchronous machine strategy are set as piecewise functions that change adaptively with the angular frequency deviation and the angular frequency change rate, so that the virtual inertia and damping coefficient are adaptively adjusted according to the system operating status to achieve dynamic optimization of output active power. However, the nonlinear characteristics introduced by the piecewise function in the above scheme affect the stability of the system, and the threshold selection of the piecewise function is difficult, the functional relationship is complex, and the engineering applicability is poor.

[0007] 3. In the patent entitled "A control method for improving the active response speed of virtual synchronous machines under weak power grids" by Shi Rongliang, Lu Dongping, Lan Caihua, Zhong Zhixian, and Wei Qiguan, the invention patent application number is 202310211322.X. The feedforward compensation of the active deviation after the first-order low-pass filter is superimposed on the virtual synchronous machine output phase angle and the grid voltage phase angle difference to speed up the output active response speed. However, the grid voltage phase angle used in this scheme needs to be obtained through phase-locked loop control, and the performance of the phase-locked loop control is seriously reduced under weak power grid conditions. Therefore, this scheme is not suitable for the active control of virtual synchronous machines under weak power grids. Summary of the invention

[0008] The technical problem to be solved by the present invention is that in the weak power grid scenario formed by the access of large-scale new energy power generation, when the new energy converter based on the voltage-controlled virtual synchronous machine strategy is connected to the grid and operated, its output active power is prone to power overshoot and low-frequency oscillation under the action of large virtual inertia. The present invention provides a method for suppressing low-frequency oscillation of the output active power of a virtual synchronous machine, so as to enhance the transient damping of the output active power control of the virtual synchronous machine, reduce power overshoot, and suppress power low-frequency oscillation, and when the grid frequency deviates from the rated value, the proposed method does not affect the steady-state deviation of the output active power. In addition, the proposed method should not increase the control order of the output active power of the virtual synchronous machine, and has good engineering application value.

[0009] To achieve the above object, the present invention provides a method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation, wherein the virtual synchronous machine includes a new energy converter, the DC side of which is connected to a new energy DC power supply provided by photovoltaic or wind power or energy storage, and the AC side outputs a three-phase voltage and is connected to a three-phase power grid through a contact switch; the suppression method comprises the following steps:

[0010] Step 1: Sample the three-phase output voltage e of the new energy converter a ,e b ,e c And the three-phase output current i a ,i b ,i c , and coordinate transformation is performed respectively to obtain the output voltage E in the synchronous rotating coordinate system d ,E q And the output current I in the synchronous rotating coordinate system d ,I q ; Wherein, subscript d and subscript q represent the d-axis and q-axis of the synchronous rotating coordinate system respectively, d is the active axis, and q is the reactive axis;

[0011] Step 2: According to the output voltage E in the synchronous rotating coordinate system d ,E q And the output current I in the synchronous rotating coordinate system d ,I q , calculate the instantaneous output active power P of the new energy converter e And the instantaneous output reactive power Q e , and use a first-order low-pass filter to filter the instantaneous output active power P e And the instantaneous output reactive power Q e Filter to obtain the average output active power of the new energy converter and the average output reactive power of the new energy converter

[0012] Step 3: Based on the reference angular frequency ω of the output voltage of the new energy converter obtained in the previous shot P 、Rated angular frequency of output voltage of new energy converter ω 0 And the given primary frequency modulation coefficient K ω , calculate the active power P required for primary frequency modulation ω , P ω =(ω 0 -ω P )K ω ; Given the active power instruction P in the virtual synchronous machine strategy ref , and according to the active power instruction P ref , the average output active power of the new energy converter obtained in step 2 And the active power P required for primary frequency modulation ω , we get the input power ΔP of the virtual inertia link,

[0013] Step 4: According to the input power ΔP of the virtual inertia link and the given virtual inertia J ω and the rated angular frequency of the output voltage of the new energy converter ω 0 , and get the output angular frequency ω′;

[0014] Step 5: According to the output angular frequency ω′ and the average output active power of the new energy converter Given the feedback compensation coefficient k p and rated angular frequency ω 0 , get the reference angular frequency ω of the output voltage of the new energy converter,

[0015] The reference angular frequency ω of the output voltage of the new energy converter is used for the next beat calculation and forms a closed loop;

[0016] Step 6: Integrate the reference angular frequency ω of the output voltage of the new energy converter to obtain the reference phase angle θ of the output voltage of the new energy converter, θ=∫ω;

[0017] Step 7: According to the rated amplitude E of the output voltage of the new energy converter 0 , the average output reactive power of new energy converter And the given reactive power-voltage droop coefficient K U , get the reference amplitude E of the output voltage of the new energy converter,

[0018] Step 8: Use the reference amplitude E of the output voltage of the new energy converter and the reference phase angle θ of the output voltage of the new energy converter as reference values ​​of the d-axis voltage amplitude and voltage phase angle of the voltage inner loop control of the new energy converter, respectively, to perform output voltage closed-loop control.

[0019] Preferably, the average output active power of the new energy converter in step 2 is and average output reactive power The calculation formula is:

[0020]

[0021] Where, T f is the time constant of the first-order low-pass filter, and s is the Laplace operator.

[0022] Preferably, the calculation process of the output angular frequency ω′ in step 4 is:

[0023] First, the expression of the rotor mechanical motion equation of the synchronous generator is given as:

[0024]

[0025] Therefore, the calculation formula of the output angular frequency ω′ can be obtained as follows:

[0026]

[0027] Where s is the Laplace operator.

[0028] Compared with the existing virtual synchronous machine output active low-frequency oscillation suppression method based on fixed damping and transient damping based on active power feedforward and feedback, the virtual synchronous machine output active low-frequency oscillation suppression method based on power feedback compensation disclosed by the present invention has the following beneficial effects:

[0029] 1. This control method superimposes the negative feedback component of the output active power on the output of the virtual inertia link of the conventional voltage-controlled virtual synchronous machine strategy without fixed damping, does not increase the output active power control order, has a simple control structure, and only introduces a negative feedback coefficient, requiring a small number of design parameters;

[0030] 2. This control method has no nonlinear characteristics. When designing parameters, a small signal model near the steady-state operating point can be established, and the design can be performed based on the established model. Since the system is still a second-order system, there is no need to reduce the order of the model. The parameter design is simple, which is conducive to engineering application.

[0031] 3. This control method does not require differential operations, grid voltage angular frequency and phase angle, and still has good stability and dynamic characteristics under weak grid conditions. In addition, since the range of the feedback coefficient is less restricted by the system stability, it has better output active low-frequency oscillation suppression capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a diagram of a new energy converter grid-connected system and converter control structure according to an embodiment of the present invention.

[0033] Figure 2 This is a control structure diagram of a method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation according to an embodiment of the present invention.

[0034] Figure 3 When the output active feedback compensation coefficient of the virtual synchronous machine strategy of the embodiment of the present invention takes different values, the active power instruction P ref New energy converter output active power waveform under step. Figure 4 The waveform of the active power output by the new energy converter under the sudden increase of the grid angular frequency is shown when the output active feedback compensation coefficient of the virtual synchronous machine strategy of the embodiment of the present invention takes different values. DETAILED DESCRIPTION

[0035] The present embodiment is described in detail below with reference to the accompanying drawings.

[0036] Figure 1 This is the new energy converter grid-connected system and converter control structure diagram. Figure 1 It can be seen that the virtual synchronous machine includes a new energy converter, the DC side of which is connected to a new energy DC power supply provided by photovoltaic or wind power or energy storage, and the AC side outputs a three-phase voltage and is connected to a three-phase grid through a contact switch.

[0037] In this embodiment, the voltage of the new energy DC power supply is 600V, the rated phase voltage of the AC side output three-phase voltage is 220V / 50Hz, and the rated capacity of the new energy converter is S rate =100KVA. The voltage reference amplitude E and voltage reference phase angle θ output by the network control type virtual synchronous machine strategy are used as the reference values ​​of the d-axis voltage amplitude and voltage phase angle of the voltage inner loop control of the new energy converter to perform output voltage closed-loop control. The output signal of the output voltage closed-loop control is used as the modulation wave of the output three-phase voltage, which is compared with the carrier to generate a drive signal to drive the power switch device to operate.

[0038] Figure 2 FIG. 1 is a control structure diagram of a method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation according to an embodiment of the present invention. Figure 2 It can be seen that the method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation of the present invention comprises the following steps:

[0039] Step 1: Sample the three-phase output voltage e of the new energy converter a ,e b ,e c And the three-phase output current i a ,i b ,i c , and coordinate transformation is performed respectively to obtain the output voltage E in the synchronous rotating coordinate system d ,E q And the output current I in the synchronous rotating coordinate system d ,I q ; Wherein, the subscript d and subscript q represent the d-axis and q-axis of the synchronous rotating coordinate system respectively, d is the active axis and q is the reactive axis.

[0040] Step 2: According to the output voltage E in the synchronous rotating coordinate system d ,E q And the output current I in the synchronous rotating coordinate system d ,I q , calculate the instantaneous output active power P of the new energy converter e And the instantaneous output reactive power Q e, and use a first-order low-pass filter to filter the instantaneous output active power P e And the instantaneous output reactive power Q e Filter to obtain the average output active power of the new energy converter and the average output reactive power of the new energy converter

[0041] In this embodiment, the average output active power of the new energy converter is and average output reactive power The calculation formula is:

[0042]

[0043] Where, T f is the time constant of the first-order low-pass filter, and s is the Laplace operator.

[0044] The first-order low-pass filter is used to filter out the harmonic components in the instantaneous output active power and the instantaneous output reactive power to avoid the harmonic power causing the output voltage angular frequency distortion. In addition, the delay effect of the first-order low-pass filter can play a role in widening the control bandwidth of the power loop and the voltage loop. In this embodiment, the filtering effect and dynamic response of the first-order low-pass filter are comprehensively considered, and the cutoff frequency of the first-order low-pass filter is set to 100Hz. The corresponding T f =1 / (2π×100)=0.0016s.

[0045] Step 3: Based on the reference angular frequency ω of the output voltage of the new energy converter obtained in the previous shot P 、Rated angular frequency of output voltage of new energy converter ω 0 And the given primary frequency modulation coefficient K ω , calculate the active power P required for primary frequency modulation ω , P ω =(ω 0 -ω P )K ω ; Given the active power instruction P in the virtual synchronous machine strategy ref , and according to the active power instruction P ref , the average output active power of the new energy converter obtained in step 2 And the active power P required for primary frequency modulation ω , we get the input power ΔP of the virtual inertia link,

[0046] Given a primary frequency modulation coefficient K ωIt is manifested as the droop relationship between the output active power of the new energy converter and the output voltage angular frequency deviation in steady state. According to relevant national standards, the voltage angular frequency deviation shall not exceed 1% of the rated angular frequency. The corresponding maximum value of the converter output active power is the rated capacity. Therefore, in this embodiment, ω 0 =2π×50Hz=314.159rad / s, K ω =S rate / 1%ω 0 =31831.012W·s / rad.

[0047] When the new energy converter based on the grid control type virtual synchronous machine strategy is connected to the grid and operated, if the grid angular frequency is the rated angular frequency, the output power of the new energy converter in the steady state is the active power instruction P ref In this embodiment, the active power instruction P is set in the initial state. ref =20kW.

[0048] Step 4: According to the input power ΔP of the virtual inertia link and the given virtual inertia J ω and the rated angular frequency of the output voltage of the new energy converter ω 0 , and get the output angular frequency ω′.

[0049] In this embodiment, the calculation process of the output angular frequency ω′ is:

[0050] First, the expression of the rotor mechanical motion equation of the synchronous generator is given as:

[0051]

[0052] Therefore, the calculation formula of the output angular frequency ω′ can be obtained as follows:

[0053]

[0054] Where s is the Laplace operator.

[0055] Virtual inertia J ω The size determines the active support capability of the virtual synchronous machine for the grid frequency when the grid frequency fluctuates. The larger the virtual inertia, the stronger the active frequency support capability of the virtual synchronous machine. However, it also leads to the weakening of the closed-loop control damping of the grid-connected output of the virtual synchronous machine, and the aggravation of power overshoot and oscillation. Considering the requirements for the initial frequency change rate under load disturbance in the power system, the virtual inertia J in the initial state in this embodiment is ω =10k g ·m 2 .

[0056] Step 5: According to the output angular frequency ω′ and the average output active power of the new energy converter Given the feedback compensation coefficient k p and rated angular frequency ω 0 , get the reference angular frequency ω of the output voltage of the new energy converter,

[0057] The reference angular frequency ω of the output voltage of the new energy converter is used for the next beat calculation to form a closed loop.

[0058] k p The larger the value, the greater the damping effect of the active closed-loop control formed by the output active power feedback compensation, and the better the dynamic overshoot and low-frequency oscillation suppression effect of the output active power of the new energy converter. p =4.71e-5rad / (s·kW).

[0059] Step 6: Integrate the reference angular frequency ω of the output voltage of the new energy converter to obtain the reference phase angle θ of the output voltage of the new energy converter, θ=∫ω.

[0060] Step 7: According to the rated amplitude E of the output voltage of the new energy converter 0 , the average output reactive power of new energy converter And the given reactive power-voltage droop coefficient K U , get the reference amplitude E of the output voltage of the new energy converter,

[0061] In this embodiment, the rated amplitude of the output voltage of the new energy converter is E 0 =311V. In addition, referring to the relevant provisions of voltage amplitude deviation in power system, K U When the average output reactive power of the new energy converter is the rated capacity, the corresponding maximum deviation of the voltage amplitude is set to 5% of the rated value, so K U =5%E 0 / S rate =1.55e-4V / Var.

[0062] Step 8: Use the reference amplitude E of the output voltage of the new energy converter and the reference phase angle θ of the output voltage of the new energy converter as reference values ​​of the d-axis voltage amplitude and voltage phase angle of the voltage inner loop control of the new energy converter, respectively, to perform output voltage closed-loop control.

[0063] The invention in this embodiment is applicable to the optimization of the output active power dynamic characteristics and the suppression of low-frequency oscillation of a new energy converter based on a voltage-controlled virtual synchronous machine.

[0064] To prove the technical effect of the present invention, Figure 1 The grid-connected system of a 100kW three-phase new energy converter is simulated. Figure 2The figure shows the active low-frequency oscillation suppression strategy of the virtual synchronous machine based on output power feedback compensation.

[0065] Figure 3 For Figure 1 The simulation of a 100kW three-phase new energy converter grid-connected system is carried out, and the output active feedback compensation coefficient k p When taking different values, the active power instruction P ref The output active power waveform of the new energy converter when the step is from 20kW to 80kW. It can be seen that as the virtual inertia J ω Increase, the overshoot in the dynamic response process of the output active power increases, the adjustment time becomes longer, and even low-frequency oscillation is caused. When the output active power feedback compensation is introduced, the damping in the dynamic response process of the output active power increases, the power overshoot and oscillation are effectively suppressed, and the damping effect is enhanced as the feedback compensation coefficient increases. In addition, the output active power feedback compensation does not affect the active power steady-state characteristics. The output active power remains unchanged before and after the introduction of the output active power feedback compensation and under different feedback compensation coefficients.

[0066] Figure 4 for Figure 1 As shown in the figure, for a 100kW three-phase new energy converter grid-connected system, when the grid angular frequency suddenly increases by 0.2rad / s at 2.5s, the output active feedback compensation coefficient k p Take different values ​​of the new energy converter output active power waveform. It can be seen that when no output power feedback compensation control is added, due to the virtual inertia J ω The overshoot in the dynamic response process of the output active power is also large, the adjustment time is long, and even low-frequency oscillation is caused. When the output active power feedback compensation is introduced, the damping in the dynamic response process of the output active power increases, and the power overshoot and oscillation are effectively suppressed. As the feedback compensation coefficient increases, the damping effect is enhanced, the power response changes from under-damping to over-damping, and the active power has no oscillation, but the response time and adjustment time are both longer.

Claims

1. A method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation, wherein the virtual synchronous machine includes a new energy converter, the DC side of which is connected to a new energy DC power supply provided by photovoltaic or wind power or energy storage, and the AC side outputs a three-phase voltage and is connected to a three-phase power grid through a contact switch; characterized in that: The inhibition method comprises the following steps: Step 1: Sample the three-phase output voltage e of the new energy converter a ,e b ,e c And the three-phase output current i a ,i b ,i c , and coordinate transformation is performed respectively to obtain the output voltage E in the synchronous rotating coordinate system d ,E q And the output current I in the synchronous rotating coordinate system d ,I q ; Wherein, subscript d and subscript q represent the d-axis and q-axis of the synchronous rotating coordinate system respectively, d is the active axis, and q is the reactive axis; Step 2: According to the output voltage E in the synchronous rotating coordinate system d ,E q And the output current I in the synchronous rotating coordinate system d ,I q , calculate the instantaneous output active power P of the new energy converter e And the instantaneous output reactive power Q e , and use a first-order low-pass filter to filter the instantaneous output active power P e And the instantaneous output reactive power Q e Filter to obtain the average output active power of the new energy converter and the average output reactive power of the new energy converter Step 3: Based on the reference angular frequency ω of the output voltage of the new energy converter obtained in the previous shot P , the rated angular frequency ω0 of the output voltage of the new energy converter and the given primary frequency modulation coefficient K ω , calculate the active power P required for primary frequency modulation ω , P ω =(ω0-ω P )K ω ; Given the active power instruction P in the virtual synchronous machine strategy ref , and according to the active power instruction P ref , the average output active power of the new energy converter obtained in step 2 And the active power P required for primary frequency modulation ω , we get the input power ΔP of the virtual inertia link, Step 4: According to the input power ΔP of the virtual inertia link and the given virtual inertia J ω And the rated angular frequency ω0 of the output voltage of the new energy converter, the output angular frequency ω′ is obtained; Step 5: According to the output angular frequency ω′ and the average output active power of the new energy converter Given the feedback compensation coefficient k p And the rated angular frequency ω0, the reference angular frequency ω of the output voltage of the new energy converter is obtained, The reference angular frequency ω of the output voltage of the new energy converter is used for the next beat calculation and forms a closed loop; Step 6: Integrate the reference angular frequency ω of the output voltage of the new energy converter to obtain the reference phase angle θ of the output voltage of the new energy converter, θ=∫ω; Step 7: According to the rated amplitude E0 of the output voltage of the new energy converter and the average output reactive power of the new energy converter And the given reactive power-voltage droop coefficient K U , get the reference amplitude E of the output voltage of the new energy converter, Step 8: Use the reference amplitude E of the output voltage of the new energy converter and the reference phase angle θ of the output voltage of the new energy converter as reference values ​​of the d-axis voltage amplitude and voltage phase angle of the voltage inner loop control of the new energy converter, respectively, to perform output voltage closed-loop control.

2. The method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation according to claim 1 is characterized in that: The average output active power of the new energy converter in step 2 and average output reactive power The calculation formula is: Where, T f is the time constant of the first-order low-pass filter, and s is the Laplace operator.

3. The method for suppressing active low-frequency oscillation of a virtual synchronous machine based on power feedback compensation according to claim 1, characterized in that: The calculation process of the output angular frequency ω′ in step 4 is: First, the expression of the rotor mechanical motion equation of the synchronous generator is given as: Therefore, the calculation formula of the output angular frequency ω′ can be obtained as follows: Where s is the Laplace operator.

Images