Network construction converter control method

Abstract

The invention provides a network construction converter control method, which comprises the following steps: decoupling an original transient damping coefficient and an original primary frequency modulation coefficient which are mutually coupled in an original VSG control system to obtain an active steady-state primary frequency modulation coefficient K [omega] and an active transient damping coefficient KD, and further respectively establishing active steady-state and transient independent regulation channels; active control steady-state deviation is realized through an active steady-state primary frequency modulation coefficient K [omega], response speed control is realized by combining a controller function Gdamp (s), active transient damping coefficient KD is adjusted to be combined with a second-order filter function GLPF (s) to control active low-frequency oscillation suppression, and independent control and adjustment of active steady state and transient state are realized. The adaptability of a network-forming converter control strategy to different power grid intensities, system inertias and load characteristics is further improved, and the problems that in an existing VSG control method, the control effect coupling of an original transient damping coefficient and an original primary frequency modulation coefficient is too high, and the requirement for independent adjustment of active power dynamic and steady-state characteristics cannot be met are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected converter control, and in particular to a grid-connected converter control method. Background Art

[0002] With the large-scale access of new energy sources, the power grid has gradually shown the characteristics of a weak grid with a “low short-circuit ratio and low inertia”, and conventional current-controlled grid-connected converters are difficult to adapt to the weak grid environment [1]. Domestic and foreign experts and scholars have paid close attention to and conducted in-depth research on voltage-type grid-connected converters using virtual synchronous generator control (VSG). Virtual synchronous control simulates the droop and inertia characteristics of synchronous generators and can spontaneously change their active and reactive outputs according to the amplitude and phase changes of the grid voltage to achieve support for the grid. It is also called a grid-connected converter control method [2]. However, the transfer function of the grid-connected control is a second-order system with two negative complex poles close to the imaginary axis. Therefore, it is an underdamped system. When the active power output of the converter changes stepwise, there is obvious overshoot and oscillation, which will lead to instability of the converter system. By increasing its fixed damping coefficient, power overshoot can be reduced and power oscillation can be suppressed. However, the coupling relationship between the fixed damping coefficient and the primary frequency modulation coefficient will jointly affect the active power-frequency droop characteristics, and the frequency offset is restricted by relevant standards and should not be too large, which greatly limits the adjustment range of the fixed damping coefficient [3]. Therefore, the active power overshoot and low-frequency oscillation suppression method based on the fixed damping coefficient is difficult to meet the steady-state and dynamic characteristic adjustment requirements of the active power primary frequency modulation and damping suppression oscillation.

[0003] Currently, there are numerous achievements in damping enhancement technology for grid-connected converter control. Numerous papers and patents have proposed transient damping schemes to improve the suppression of active power low-frequency oscillations without affecting the steady-state characteristics of the active power. These schemes employ feedforward compensation after applying a lead-lag correction to the output active power and the deviation between the output active power and the output active power of the virtual synchronous generator[4-5], or feedback compensation after applying a lead-lag correction to the output angular frequency of the virtual synchronous generator[6-7], thereby enhancing transient damping and suppressing low-frequency oscillations.

[0004] In their patent application number CN119518840A, entitled "A Damping Enhanced Control Method for Energy Storage Converters Based on Feedforward Control," Li Xing, Zhang Long, Liang Shuchao, et al., add a feedforward controller with additional degrees of freedom to improve the active power flow model of the energy storage converter, enhancing the converter's damping control effectiveness. In their patent application number CN119518849A, entitled "A Method for Suppressing Active Low-Frequency Oscillations of Virtual Synchronous Generators Based on Power Feedback Compensation," Su Jianming, Wang Xiaoming, Zhao Wenguang, et al., construct a negative feedback component of instantaneous active power and superimpose it on the virtual inertia link. This effectively reduces active power dynamic overshoot and enhances low-frequency oscillation suppression without increasing the output active power control order or steady-state error. However, as the feedback compensation coefficient increases, the damping effect increases, but the patent also notes that this increases the active power response time and adjustment time.

[0005] In the article "Improved VSG Control Strategy Based on Transient Damping Enhancement," Jiang Shiming and Tang Jie, Power System Protection and Control, Vol. 51, No. 19, 2023, pp. 144-154, improve the damping characteristics of VSG control by introducing high-frequency components of active power and angular frequency. Derivation proves that the added damping term does not affect the active steady-state error. In the article "A Novel Power System Power Difference Feedforward Oscillation Suppression Method Based on Virtual Inertia Control," Wang Xue, Liu Lin, Zhuo Qingdong, et al., China Electric Power, Vol. 57, No. 4, 2024, pp. 68-76, compared to conventional power difference differential feedforward control damping enhancement methods, this method adds a first-order integral term based on inertia control. Consequently, the addition of zeros and poles to the active closed-loop system improves active transients. However, when using first-order differential combined with first-order low-pass filtering for damping optimization, the high-frequency perturbations introduced by the differential cannot be ignored. In an article titled "Strategy for Suppressing Active Power Oscillations in VSG Parallel Systems Based on Frequency Advance Correction," Miao Changxin, Zhao Wenpeng, Liu Jiaming, et al., Power System Protection and Control, Vol. 52, No. 15, 2024, pp. 24-35, the VSG output active power is fed back to the angular frequency deviation through a proportional link, achieving the suppression effect of over-oscillations by connecting a proportional differential link in series with the VSG output active power circuit, and effectively avoiding the influence of high-frequency noise caused by the differential. In existing research, we found that most scholars have revealed the contradiction between the active power oscillation problem and the steady-state deviation characteristics of the output power, and have achieved the suppression of power oscillations without affecting the steady-state active power-frequency droop control characteristics of the system by enhancing transient damping. However, many studies have not decoupled the damping regulation and primary frequency regulation in the control of grid-connected converters to establish independent regulation channels for the two.

[0006] In summary, transient damping enhancement methods that construct active power feedforward or frequency feedback compensation have been widely used in existing research. This compensation-based transient damping enhancement method can increase the damping ratio and effectively suppress power oscillations without affecting the steady-state deviation of the VSG output active power. However, it does not achieve decoupling of the active power-frequency droop characteristic and the damping characteristic.

[0007] [1]Y.Xu, H.Nian, B.Hu and D.Sun, "Impedance Modeling and StabilityAnalysis of VSG Controlled Type-IV Wind Turbine System," in IEEE Transactionson Energy Conversion, vol.36, no.4, pp.3438-3448, Dec.2021

[0008] [2] Y.Ma, J.Xu, C.Gao, G.Li and K.Wang, "Low-Frequency Oscillations andResonance Analysis of VSG-Controlled PMSG-based Wind Generation Systems," inJournal of Modern Power Systems and Clean Energy, vol.13, no.1, pp.115-127, January 2025

[0009] [3] J.Yang, S.Zhao, Y.Wang, R.Mao, X.Yao and X.Su, "Three-level VSGfeedforward control strategy based on transient damping enhancement," 20243rdInternational Conference on Energy, Power and Electrical Technology (ICEPET), Chengdu, China, 2024, pp.1782-1785

[0010] [4] Shi Rongliang, Wang Guobin, Lan Caihua, et al. Active power oscillation suppression strategy for diesel-storage microgrid based on active power proportional differential feedforward VSG[J]. Renewable Energy, 2024, 42(08): 1074-1082.

[0011] [5] Bai Wenyuan, Zhuang Guofeng, Luo Xuemei, et al. Power oscillation suppression method of VSG parallel system based on dynamic damping enhancement[J]. Smart Power, 2024, 52(11): 16-22+113.

[0012] [6] SHUAI ZK, HUANG W, SHEN ZJ, et al. Active power oscillation and suppression techniques between two parallel synchronverters during loadfluctuations[J]. IEEE Transactions on Power Electronics, 2020, 35(4): 4127-4145.

[0013] [7] Su Can, Wang Lei, Zhou Wen, et al. Decentralized coordinated suppression strategy for low-frequency power oscillations in VSG parallel systems based on transient damping enhancement [J / OL]. Journal of Power Supply, 1-13 [2025-03-14]. Summary of the Invention

[0014] The purpose of the technical solution of the present invention is to design a grid converter control method with decoupling of active power-frequency droop and damping characteristics based on the existing transient damping enhancement technology to meet the independent regulation requirements of active power steady-state and dynamic characteristics.

[0015] The technical solution of the present invention provides a grid-connected converter control method, which decouples the original transient damping coefficient and the original primary frequency modulation coefficient that are coupled to each other in the original VSG control system, and obtains the active steady-state primary frequency modulation coefficient K ω and active transient damping coefficient K D , achieving independent regulation of active steady-state and transient states, thereby reducing steady-state errors while suppressing power oscillations.

[0016] Preferably, a controller function G with a steady-state gain of 1 is introduced damp (s), combined with the active steady-state primary frequency modulation coefficient K ω , based on the independent regulation of the active steady state, the power response speed is improved and the problem of harmonic amplification is avoided.

[0017] Preferably, the controller function G damp The formula for (s) is as follows:

[0018]

[0019] Where K d K is the differential coefficient used to improve the power response speed. pis the bandwidth factor to control, and ξ is the damping factor used to avoid harmonic amplification.

[0020] Preferably, a second-order filter function G is introduced LPF (s) Remove the high-frequency noise to obtain the steady-state component, and take the difference between the original signal and the steady-state component as the transient component, combined with the active transient damping coefficient K D Independent regulation of the active transient state is achieved to suppress power oscillations.

[0021] Preferably, the active steady-state primary frequency modulation coefficient K ω and active transient damping coefficient K D After achieving independent regulation of steady-state and transient power, the transfer function of active output power affected by grid-side frequency and active output command is as follows:

[0022]

[0023] Where G LPF (s) is the second-order filter function, ω LPF1 is the cutoff frequency of the filter, ξ1 is the filter damping coefficient, P e ' is the active output power after decoupling, K is the synchronous voltage coefficient, P ref is the active power output instruction in the virtual synchronous machine strategy, K ω is the active steady-state primary frequency modulation coefficient, K D is the active transient damping adjustment coefficient, G damp (s) is the controller function, ω0 is the rated angular frequency of the grid converter output voltage, J is the given inertia coefficient, ω grid is the rated angular frequency of the remote ideal power grid.

[0024] Preferably, through the transfer function, it is obtained that there is a steady-state error in the active output of the VSG control system in steady state, and the steady-state error is only related to the active steady-state primary frequency modulation coefficient.

[0025] Preferably, the formula for the steady-state error is as follows:

[0026] ΔP' e | s→0 =(P' e -P ref )| s→0 =K ω (ω0-ω grid ).

[0027] The technical solution of the present invention proposes a grid-connected converter control method, which decouples the original transient damping coefficient and the original primary frequency modulation coefficient in the original VSG control system to obtain the active steady-state primary frequency modulation coefficient K ω and active transient damping coefficient KD , and then establish independent regulation channels for active steady state and transient state respectively, through the active steady state primary frequency modulation coefficient K ω Realize active power control steady-state deviation, combined with controller function G damp (s) Realize the control of response speed and adjust the active transient damping coefficient K D Combined with the second-order filter function G LPF (s) Control the suppression of active low-frequency oscillations, realize independent control and regulation of active steady-state and transient states, further improve the adaptability of the grid-type converter control strategy to different grid strengths, system inertias and load characteristics, and solve the problem that the control effects of the original transient damping coefficient and the original primary frequency modulation coefficient in the existing VSG control method are too strongly coupled and cannot meet the independent regulation requirements of the dynamic and steady-state characteristics of active power. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the circuit principle of the existing grid-connected converter control system;

[0029] Figure 2 This is the block diagram of the traditional VSG active closed-loop control structure;

[0030] Figure 3 A block diagram of the VSG active closed-loop control structure with independent regulation of active steady-state and transient states provided in an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of transient changes in the output power of the grid converter when the reference active power suddenly changes with the traditional VSG and the embodiment of the present invention;

[0032] Figure 5 Schematic diagram of grid-side frequency changes during low-frequency small disturbances for a traditional VSG and an embodiment of the present invention;

[0033] Figure 6 Schematic diagram of the active output power changes of a traditional VSG and an embodiment of the present invention when the frequency changes suddenly with a small disturbance. DETAILED DESCRIPTION

[0034] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0035] An embodiment of the present invention provides a grid-connected converter control method that decouples the active primary frequency modulation coefficient and the transient damping coefficient to achieve independent control and adjustment of active control steady-state deviation, response speed, and low-frequency oscillation suppression, including the following steps:

[0036] (1) Basic model of grid-connected converter

[0037] Sampling the three-phase output voltage u of the grid-connected converter abc And the three-phase output current i abc , and perform coordinate changes respectively to obtain the output voltage u in the synchronous rotating coordinate system d ,u q And the output current i in the synchronous rotating coordinate system d ,i q Wherein, the subscripts d and q represent the d-axis and q-axis of the synchronous rotating coordinate system, respectively, d being the active axis and q being the reactive axis. It should be understood that the grid-connected converter control method provided in the embodiments of the present invention is not limited to application to VSG grid-connected converters of various power levels, but can also be applied to new energy converters such as energy storage converters and photovoltaic / power generation converters.

[0038] According to the output voltage u in the synchronous rotating coordinate system d ,u q And the output current i in the synchronous rotating coordinate system d ,i q , calculate the instantaneous output active power P of the grid converter e And the instantaneous output reactive power Q e , and use a second-order low-pass filter to filter the instantaneous output active power and instantaneous output reactive power respectively to obtain the average output active power P of the grid converter eLPF The average output reactive power Q of the grid converter is eLPF , as shown in formula (1):

[0039]

[0040] Where, ω LPF is the cutoff frequency of the second-order low-pass filter, and ξ is the filter damping coefficient.

[0041] According to the reference angular frequency ω of the grid converter output voltage vsg , the rated angular frequency ω0 of the grid converter output voltage and the given primary frequency modulation coefficient, calculate the active power P required for primary frequency modulation ω , P ω =(ω0-ω vsg )k p ; Given the active power instruction P in the virtual synchronous machine strategy ref , and according to the active power instruction P ref , average output active power P eLPF And the active power P required for primary frequency regulation ω , we get the input power ΔP of the virtual inertia link, ΔP=Pref -P eLPF +P ω According to the input power ΔP of the virtual inertia link, the given inertia coefficient J and the rated angular frequency ω0 of the output voltage of the grid converter, the output angular frequency ω is obtained. Δv The active-frequency rotor motion equation can be obtained as follows:

[0042]

[0043] Further obtain the reference angular frequency ω of the grid converter output voltage vsg , as shown in formula (3):

[0044] ω vsg =ω Δv +ω0 ​​(3)

[0045] Given reactive power command Q ref , according to the rated amplitude of the grid converter output voltage U ref , the average output reactive power Q of the grid converter eLPF And the given reactive-voltage droop coefficient K q , get the reference amplitude of the grid converter output voltage U vsg , as shown in formula (4):

[0046] U vsg =U ref +K q (Q ref -Q eLPF ) (4)

[0047] (2) Active closed-loop transient control model

[0048] In actual power systems, the equivalent inductive reactance of the power grid is usually much larger than the equivalent impedance of the power grid. Therefore, in the following analysis, the line equivalent impedance Z L Equivalent to X L To reduce the amount of calculation; in addition, the grid voltage is set to zero phase, and the vector method can be used to represent the grid-connected point voltage of the grid converter and the remote ideal grid voltage, which are expressed as and Since the line impedance is usually small, the voltage drop it produces is small, so it can be approximately considered that U pcs =U grid ; and, the power angle δ of the grid converter pcs Usually the value is small, sinδ pcs Equivalent to δ pcs To simplify the model. Figure 1According to the line structure and power transmission principle of the circuit, the active power and power angle injected by the grid converter into the grid can be equivalent to:

[0049]

[0050] According to formula (1)-formula (6), we can get Figure 2 The energy storage VSG active closed-loop control structure block diagram is shown. Define K as the synchronous voltage coefficient, according to Figure 2 , get the unfiltered output active power P e The transfer function affected by the grid-side frequency and active power output command is shown below:

[0051]

[0052] For large power grids, ω0 = ω grid , but for weak power grids that lack frequency support from large power grids, ω0 and ω grid There is an inequality, in which case the active output of the VSG will have a steady-state error ΔP e | s→0 , as shown in (8):

[0053] ΔP e | s→0 =(P e -P ref )| s→0 =(D p ω0+k p )(ω0-ω grid ) (8)

[0054] Therefore, the original transient damping coefficient (D p ω0) and the original primary frequency modulation coefficient (k p ) There is mutual coupling. The larger the original transient damping coefficient, the larger the steady-state error of active power. A smaller transient damping coefficient can reduce the steady-state error, but it cannot effectively suppress power oscillation. This patent decouples the primary frequency modulation coefficient from the transient damping coefficient to achieve independent regulation of active steady-state and transient without affecting each other. The improved active control structure is as follows Figure 3 shown.

[0055] (3) Active power steady-state regulation design

[0056] The control link of active power frequency-droop regulation is mainly divided into two parts, such as Figure 3 As shown, the front part is a controller function G with a numerator of a first-order differential link and a denominator of a second-order integral link. damp (s), as shown in formula (9). Where, K ωThe second-order integral link controller provided by the embodiment of the present invention is not limited to the transfer function shown in formula (9), and can also be a multi-order integral link controller well known in the industry.

[0057]

[0058] Where K d is the differential coefficient used to improve the power response speed (the numerator is equivalent to the differential coefficient K of the first-order differential link d ), K p To control the bandwidth factor, ξ is the damping coefficient used to avoid harmonic amplification (the denominator is equivalent to the damping coefficient ξ of a second-order low-pass filter).

[0059] In addition, since it is not desirable to introduce additional control gain, when the control reaches a steady state, G damp The gain of (s) is 1, as shown in formula (10):

[0060]

[0061] The introduction of the first-order differential link is mainly used to improve the power response speed, while the second-order integral link can be equivalent to a second-order low-pass filter to avoid the problem of harmonic amplification caused by the active power deviation after passing through the first-order differential link.

[0062] (4) Active power transient regulation design

[0063] like Figure 3 As shown, the high-frequency noise is removed by the second-order filtering link to obtain the steady-state component, and the transient component is obtained by subtracting the steady-state component from the original signal. D is the active transient damping coefficient.

[0064] (5) After decoupling the active steady-state and transient regulation, the active output power P e The transfer function affected by the grid side frequency and active output command is as follows:

[0065]

[0066] Where G LPF (s) is the second-order filter function, ω LPF1 is the cutoff frequency of the filter, and ξ1 is the damping coefficient of the filter.

[0067] In steady state, the active output of VSG will have a steady-state error ΔP e '| s→0 , as shown in (12):

[0068] ΔP' e | s→0=(P' e -P ref )| s→0 =K ω (ω0-ω grid ) (12)

[0069] It can be seen from the formula that under the active power control method proposed in this patent, the output power stability error is only related to the primary frequency modulation coefficient K ω This is related to the fact that the transient and steady states of active power can be adjusted independently without affecting each other.

[0070] In order to verify that the VSG control method (FVSG) proposed in this patent has a certain degree of improvement over the traditional VSG control method (CVSG), a simulation test experiment of power and frequency response was designed, and the parameter design is shown in Table 1.

[0071] Table 1 Simulation model related parameters

[0072] variable parameter Rated active power 750kW Rated AC line voltage 690V Rated DC voltage 1300V Rated angular frequency 100π Switching frequency 6400Hz Inertia coefficient J 35 AC side short-circuit impedance ratio 5

[0073] right Figure 1 The simulation verification experiment of a 750kW energy storage converter grid-connected system is shown. It should be understood that the method provided in the embodiment of the present invention is not limited to Figure 1 The control structure shown can also be the grid-connected system and control structure of the grid-connected converter known in the industry. ref When the power steps from 450kW to 750kW, the active output of the converter follows the command value response, such as Figure 4 As shown. Figure 4 Comparing Curve 2 with Curve 1, we can see that the traditional VSG control method has a response time of 0.56s to active power changes, while the proposed method has a response time of 0.14s. This result shows that the proposed method has better performance in terms of active power response speed.

[0074] Construct a low-frequency small disturbance source with an amplitude of ±0.1Hz and a frequency of 5Hz. Figure 5 The grid-side frequency changes at 5 seconds after the disturbance. Simulation results show that both the traditional VSG control method and the method proposed in this patent have a certain degree of suppression effect on low-frequency disturbances. We note that the proposed method increases the freedom of VSG control adjustment, thus providing an additional damping effect and better suppression of low-frequency disturbances.

[0075] When the grid-side frequency changes from 50Hz to 50.1Hz in 3s, the active power of the converter changes with the frequency. Figure 6 As shown. Figure 4 The results are similar, Figure 6Compared with Curve 1, Curve 2 has a response speed increased by about 80% under the same steady-state damping coefficient, indicating that the method proposed in this patent has a faster active power-frequency response speed.

[0076] In addition, if Figure 6 As shown in Curve 1, due to the coupling between the primary frequency modulation coefficient and the damping coefficient of the traditional VSG active control, when the system damping characteristics are required to be maintained, there will be an inherent active output frequency modulation difference ΔP. However, this difference causes the output to fail to reach the expected rated power, which is usually reflected in the system power shortage, which is not conducive to the safe and stable operation of the system. At 7s, the low-frequency disturbance source constructed above is added to the grid-side frequency, and the transient damping coefficients of the two methods are set to be the same. The simulation results show that, under the premise of not affecting the damping suppression effect, the method proposed in this patent can realize the regulation decoupling of active primary frequency modulation and transient damping, by adjusting the primary frequency modulation coefficient K ω Independent regulation to eliminate active output frequency modulation difference, such as Figure 6 As shown in curve 3.

[0077] In summary, by comparing with the traditional VSG control method, it is shown that the method proposed in this patent can adjust the primary frequency modulation coefficient K ω and damping coefficient K D Independent adjustment is performed to increase the freedom of active steady-state adjustment, better suppress low-frequency oscillations, and speed up active response.

[0078] The beneficial effects of the embodiments of the present invention are as follows:

[0079] The active power control method for grid-type converters proposed in this patent can achieve independent adjustment of the active output power-frequency droop steady-state characteristics and the transient damping oscillation suppression characteristics. In addition, compared with the existing transient damping enhancement method, the method proposed in this patent can further improve the active power response speed while enhancing transient damping without affecting the active output power deviation, and the adjustment of the two is independent and decoupled. In order to verify the performance of this method, simulation test experiments of power and frequency response were designed. The results show that the method proposed in this patent can effectively suppress active power overshoot and oscillation, and can independently accelerate the active power-frequency droop steady-state response speed, reducing the mutual constraints between the traditional transient damping coefficient and the primary frequency modulation coefficient.

Claims

1. A grid-connected converter control method, characterized in that: Decouple the original transient damping coefficient and the original primary frequency modulation coefficient that are coupled to each other in the original VSG control system to obtain the active steady-state primary frequency modulation coefficient K ω and active transient damping coefficient K D , achieving independent regulation of active steady-state and transient states, thereby reducing steady-state errors while suppressing power oscillations.

2. A grid-connected converter control method according to claim 1, characterized in that: Introduce a controller function G with a steady-state gain of 1 damp (s), combined with the active steady-state primary frequency modulation coefficient K ω , based on the independent regulation of the active steady state, the power response speed is improved and the problem of harmonic amplification is avoided.

3. A grid-connected converter control method according to claim 2, characterized in that: The controller function G damp The formula for (s) is as follows: Where K d K is the differential coefficient used to improve the power response speed. p is the bandwidth factor to control, and ξ is the damping factor used to avoid harmonic amplification.

4. A grid-connected converter control method according to claim 1, characterized in that: Introducing the second-order filter function G LPF (s) Remove the high-frequency noise to obtain the steady-state component, and take the difference between the original signal and the steady-state component as the transient component, combined with the active transient damping coefficient K D The independence of the active transient regulation is achieved to suppress power oscillation.

5. A grid-connected converter control method according to claim 1, characterized in that: In the active steady-state primary frequency modulation coefficient K ω and active transient damping coefficient K D After achieving independent regulation of steady-state and transient power, the transfer function of active output power affected by grid-side frequency and active output command is as follows: Where G LPF (s) is the second-order filter function, ω LPF1 is the cutoff frequency of the filter, ξ1 is the filter damping coefficient, P e ' is the active output power after decoupling, K is the synchronous voltage coefficient, P ref is the active power output instruction in the virtual synchronous machine strategy, K ω is the active steady-state primary frequency modulation coefficient, K D is the active transient damping adjustment coefficient, G damp (s) is the controller function, ω0 is the rated angular frequency of the grid converter output voltage, J is the given inertia coefficient, ω grid is the rated angular frequency of the remote ideal power grid.

6. A grid-connected converter control method according to claim 5, characterized in that: Through the transfer function, it is found that there is a steady-state error in the active output of the VSG control system in steady state, and the steady-state error is only related to the active steady-state primary frequency modulation coefficient.

7. A grid-connected converter control method according to claim 6, characterized in that: The formula for the steady-state error is as follows: ΔP' e | s→0 =(P' e -P ref )| s→0 =K ω (ω0-ω grid )。

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