Control system for accessing networking type virtual synchronous machine to power grid

Abstract

The invention discloses a control system for accessing a network-forming type virtual synchronous machine to a power grid, and the method comprises the steps: considering adaptive parameter cooperative control in a virtual frequency modulation control link, and determining an active variable quantity initial value of a converter; in a virtual inertia and damping control and virtual frequency modulation control link, acquiring an internal potential virtual phase angle based on a set active power reference value and an actually output active power; in the virtual excitation control link, the internal potential amplitude of the converter is obtained based on the actual voltage signal and the reference voltage signal of the excitation voltage regulator; in the virtual impedance control link, the reference voltage of the voltage and current double-closed-loop control link is calculated based on the internal potential virtual phase angle and the internal potential amplitude; in the voltage and current double-closed-loop control link, the reference voltage of the converter is obtained based on the reference voltage; and controlling a switching tube of the converter by taking the reference voltage as a PWM (Pulse Width Modulation) signal of the converter. According to the invention, the grid-connected control of the network construction type power supply is realized, and the purposes of network voltage support, primary frequency modulation and autonomous inertia support are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to grid-forming control technology, and in particular to a control system for grid-forming virtual synchronous machine access to a power grid. BACKGROUND

[0002] Compared with the traditional grid-following (GFL) control strategy, the grid-forming (GFM) control technology can establish and maintain synchronization autonomously under the condition of no external grid reference signal, and realize island operation, due to its self-sustaining voltage source characteristics. Therefore, the grid-forming control technology is expected to provide more effective frequency support for stable operation of new power systems.

[0003] At present, the research on grid-forming converters mainly focuses on the application of virtual synchronous generators (VSG). The document (Meng Zhiwei, Hou Yuqiang, Fang Yongjie, et al. Strong damping voltage source type virtual synchronous generator large disturbance power angle stability analysis [J]. Power System Automation, 2018, 42 (09): 44-50) qualitatively analyzes the influence of strong damping coefficient on the transient stability of VSG equipment under large disturbance; the document (Qin Xiaohui, Su Lining, Chi Yongning, et al. Inertia support and primary frequency regulation function positioning of virtual synchronous generator in large power grid [J]. Power System Automation, 2018, 42 (09): 36-43) reveals the cooperative action mechanism of inertia response and primary frequency regulation in system frequency control through theoretical analysis and dynamic simulation; the document (Qoria T, Gruson F, Colas F, et al. Critical clearing time determination and enhancement of grid-forming converters embedding virtual impedance as current limitation algorithm [J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2020, 8 (2): 1050-1061) proposes a stable control method based on dynamic droop coefficient adjustment for the transient stability problem of droop control VSG. Research shows that by adjusting the droop coefficient K dThe transient process of the system can be significantly affected; the literature [Wang Jianwei, Meng Jianhui, Wang Yi, et al. Small-signal modeling and dynamic frequency support strategy of grid-connected direct-drive wind turbine [J]. Power System Technology, 2024, 36(05): 48-58] innovatively designed a set of adjustable parameter dynamic frequency regulation scheme, but its stability analysis model has significant shortcomings: this study simplifies the wind turbine as an ideal voltage source, which cannot accurately reflect the actual operating characteristics. Literature (Li Mei, Huang Wentao, Ai Nengling, et al. Adaptive inertia control strategy of virtual synchronous generator controlled distributed generation under frequency disturbance [J]. Power Grid Technology, 2020, 44(04): 1525-1533) strategy adaptively adjusts the virtual inertia according to the frequency deviation amplitude, solving the problem of fixed inertia constant under the output stability and response speed of inverter-type distributed energy difficult to optimize balance; Literature (Yu Jingrong, Sun Wen, Yu Jiaqi, et al. Virtual synchronous generator control of grid-connected inverter based on adaptive inertia [J]. Power System Protection and Control, 2022, 50(04): 137-144) introduces adaptive rotational inertia control in single-phase inverter grid-connected system, which can realize dynamic regulation of system frequency, significantly suppress power oscillation and avoid dynamic response overshoot; Literature (Zhang Fudong, Park Jung-guk, Guo Yuqi, et al. Research on adaptive control strategy of VSG rotational inertia [J]. Solar Energy, 2020, 41(10): 93-100) proposes to apply adaptive rotational inertia control strategy to multi-inverter parallel system, realizing autonomous frequency regulation under load disturbance condition; Literature (FANG H W, YU Z W. Control of virtual synchronous generator for frequency regulation using a coordinated self-adaptive method [J]. CSEE Journal of Power and Energy Systems, 2024, 10(1): 175-184) introduces a secondary frequency regulation link in the virtual synchronous generator (VSG) control architecture, combined with the coordinated adaptive optimization of virtual inertia, virtual damping and frequency regulation parameters, which can significantly improve the dynamic response characteristics of system frequency.

[0004] Based on existing research, the frequency support capability of the system can be enhanced to a certain extent by optimizing the virtual inertia and damping parameters, but this method still has obvious limitations. Documents (Yang Yin, Mei Fei, Zhang Chenyu, et al. Virtual synchronous generator inertia and damping coefficient cooperative adaptive control strategy [J]. Electric power automation equipment, 2019, 39(03): 125-131) and documents (Wei Zhi, Shen Qi, Ji Qiuhua, et al. Small signal modeling and stability analysis of virtual synchronous machine parallel system [J]. Power electronics technology, 2019, 53(08): 11-15) point out that such parameter adjustment may reduce the stability margin of the virtual synchronous machine while improving the inertia response capability, thereby adversely affecting the small signal stability of the system. In addition, documents (Zhao Dongmei, Pei Jiannan, Bai Junhui, et al. Research on frequency regulation capability improvement technology of grid-connected converter in weak and extremely weak grid scenarios [J]. Proceedings of the Chinese Society of Electrical Engineering, 2024, 44(S1): 215-226) further point out that the control performance of the grid-connected virtual synchronous generator may weaken during frequency regulation due to changes in actual operating conditions and scenarios, which may increase the active transient overshoot and prolong the power oscillation duration, thereby affecting the dynamic response quality and stable operation capability of the system. Therefore, the existing methods still have significant deficiencies in maintaining control consistency and dynamic stability when dealing with multi-condition switching and complex operating scenarios. SUMMARY

[0005] The present application aims at the deficiencies in the prior art and provides a control system for grid-connected virtual synchronous machines accessing power grids. The control system is used to solve the problem of limited stability margin of virtual synchronous machines caused by changes in control parameters on the basis of better frequency stability control.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: A control system for grid-connected virtual synchronous machines accessing power grids, comprising: a power calculation link for obtaining three-phase currents and three-phase voltages output by an inverter, performing Park transformation on the three-phase currents and three-phase voltages based on an internal electromotive force virtual phase angle to obtain currents and voltages in a dq rotating coordinate system, and calculating active power actually output by the inverter based on the currents and voltages in the dq rotating coordinate system P e and reactive power Q e ; a virtual governor control link for determining an active change amount initial value of the inverter; a virtual inertia and damping control and virtual frequency regulation control link for obtaining an active power reference value in combination with the active change amount initial value of the inverter and a preset active static operating point, and obtaining an internal electromotive force virtual phase angle based on the active power reference value and the active power actually output by the inverter. a virtual excitation control link for obtaining an internal potential amplitude of the converter based on an actual voltage signal of the excitation voltage regulator, a reference voltage signal and an actual reactive power output of the inverter; a virtual impedance control link for calculating a reference voltage of the voltage-current double closed loop control link based on the internal potential virtual phase angle and the internal potential amplitude; a voltage-current double closed loop control link for obtaining a reference voltage of the converter based on the reference voltage of the voltage-current double closed loop control link; a PWM modulation module for PWM modulating the reference voltage of the converter to obtain a PWM signal for controlling the switching device of the converter.

[0007] To optimize the above technical solutions, the specific measures taken further include: Further, the actual active power output of the inverter P e and the reactive power Q e are calculated as follows:

[0008] wherein, P e and Q e are the actual active power and the reactive power output of the inverter respectively, u td and u tq are the d-axis component and the q-axis component of the terminal voltage of the inverter respectively; i Ld and i Lq are the d-axis component and the q-axis component of the output current of the inverter respectively.

[0009] Further, the internal potential virtual phase angle obtained based on the active power reference value and the actual active power output of the inverter is specifically: The internal potential virtual phase angle is calculated by using the following formula:

[0010] wherein, is the internal potential virtual phase angle, ω n is the grid reference angular frequency; ω g is the grid angular frequency measurement value calculated from the grid-side collected voltage; J is the virtual inertia; P ref represents the active power reference value; Pe is the actual active power output by the inverter; K v is the virtual inertia control coefficient; K d is the virtual damping control coefficient; D p is the equivalent damping coefficient; s is a differential operator.

[0011] Further, the inner potential amplitude of the converter is calculated based on the actual voltage signal of the field voltage regulator, the reference voltage signal and the actual reactive power output by the inverter, and specifically is: The inner potential amplitude of the converter is calculated by using the following formula:

[0012] In the formula, E ref is the inner potential amplitude of the converter, Q set is the set reactive mechanical power; Q e is the actual reactive power output by the inverter; K pQ is the proportional control coefficient, K iQ is the integral control coefficient; D q is the virtual field coefficient; u t is the actual voltage signal of the field voltage regulator; u n is the reference voltage signal of the field voltage regulator; s is a differential operator.

[0013] Further, the reference voltage of the voltage-current double closed-loop control link is calculated based on the virtual phase angle of the inner potential and the inner potential amplitude, and specifically is:

[0014] In the formula, and are the d-axis component and the q-axis component of the reference voltage of the voltage-current double closed-loop control link in the dq coordinate respectively, E d and E q are the virtual phase angle of the inner potential of the converter and the inner potential amplitude of the converter respectively, E ref are the d-axis component and the q-axis component of the inner potential amplitude obtained through the abc / dq conversion; L v is the virtual impedance inductance parameter; ω ref is the inner potential reference angular frequency,​ and are the d-axis component and the q-axis component of the main line after the filtering link in the dq coordinate.

[0015] Further, the voltage-current double closed loop control link includes voltage inner loop control and current inner loop control, and the reference voltage obtained based on the voltage-current double closed loop control link is specifically: The reference voltage of the voltage-current double closed loop control link is subjected to voltage inner loop control to obtain the reference current output by the voltage inner loop in the dq coordinate system, and the reference current output by the voltage inner loop in the dq coordinate system is subjected to current inner loop control to obtain the reference voltage of the converter in the dq coordinate system.

[0016] Further, the reference current output by the voltage inner loop in the dq coordinate system is subjected to current inner loop control to obtain the reference voltage of the converter in the dq coordinate system, and the reference voltage of the voltage-current double closed loop control link is specifically:

[0017] wherein, and are the d-axis component and the q-axis component of the reference current output by the voltage inner loop in the dq coordinate system, K pv and K iv are the d-axis component and the q-axis component of the reference current output by the voltage inner loop in the dq coordinate system, and are the d-axis component and the q-axis component of the reference voltage of the voltage-current double closed loop control link in the dq coordinate, U td and U tq are the d-axis component and the q-axis component of the voltage value in the dq coordinate system obtained by Park transformation of the voltage measured at the grid-connected point; C f is the equivalent capacitance parameter of the control link; ω ref is the inner potential reference angular frequency, and are the d-axis component and the q-axis component of the main line after the filtering link in the dq coordinate.

[0018] Further, the reference current output by the voltage inner loop in the dq coordinate system is subjected to current inner loop control to obtain the reference voltage of the converter in the dq coordinate system, and the reference voltage of the voltage-current double closed loop control link is specifically:

[0019] wherein, and are respectively the d-axis component and the q-axis component of the reference voltage of the converter in the dq coordinate system, K pi and K ii are respectively the proportional control coefficient and the integral control coefficient of the current inner loop; s is a differential operator, and are respectively the d-axis component and the q-axis component of the reference current output by the voltage inner loop in the dq coordinate system, Ld , i Lq is the current value of the main circuit current in the dq coordinate system obtained by Park transformation, f is the equivalent inductance parameter of the control link, U td and U tq are respectively the d-axis component and the q-axis component of the voltage value in the dq coordinate system obtained by Park transformation of the voltage measured at the grid-connected point, ω ref is the reference angular frequency of the internal potential,

[0020] Further, the PWM modulation of the reference voltage of the converter is specifically as follows: taking the virtual angular frequency of the internal potential as the reference angular frequency obtaining the reference voltage for PWM modulation by dq / abc transformation of the reference voltage of the converter in the dq coordinate system, and obtaining the PWM signal after PWM modulation.

[0021] Further, the virtual inertia control coefficient is adaptively adjusted based on the frequency fluctuation, and the specific adjustment is as follows:

[0022] wherein, K v is the virtual inertia control coefficient, K v0 is the reference value of the virtual inertia coefficient; K d is the virtual damping coefficient, η is the differential control coefficient, f / Δ t is the frequency change rate in the time Δ t , Δ f is the frequency change amount, f 0 is the quasi-steady-state frequency deviation.

[0023] The present application has the following advantages: The technical scheme of the present application avoids the pain point of traditional grid-connected type control relying on a phase-locked loop, realizes grid-forming type power grid-connected control through autonomous generation of a reference phase, and achieves the purposes of power grid voltage support, primary frequency modulation and autonomous inertia support.

[0024] The present application improves the system stability margin and dynamic performance: compared with the problem of reducing the stability margin that the existing parameter optimization method may have, the present application can more accurately reveal the influence mechanism of inertia, damping and other parameters on system stability through the established single machine equivalent model and closed-form solution, thereby guiding parameter design, enhancing the frequency support capability, effectively protecting and improving the system stability margin, and suppressing power oscillation.

[0025] The present application significantly enhances the multi-working-condition adaptability and control robustness: in view of the problem that the control performance of the prior art weakens when the working condition or scene changes, the parameter adaptive cooperative control strategy proposed in the present application can adjust key control parameters according to the real-time running state of the system, effectively reduces the active transient overshoot, shortens the oscillation duration, and ensures that the system has good dynamic response quality and consistency performance under different operating conditions.

[0026] The present application takes into account the control effect and implementation complexity: the control strategy proposed in the present application has a simple structure, is easy to implement and digitize, and avoids the additional cost and reliability problems caused by complex algorithms. Through simulation verification, the strategy performs better in terms of key indicators such as maximum frequency drop depth, quasi-steady-state frequency deviation, rate of change of frequency (ROCOF), and improves the frequency stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The structure diagram of the control system for grid-forming type virtual synchronous machine access to the power grid proposed in the present application.

[0028] Figure 2 The frequency response change curve for cooperative control. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] Embodiment one The present application proposes a control system for grid-forming type virtual synchronous machine access to the power grid, the structure of the system is as shown in Figure 1 The system comprises: The power calculation link is used to acquire three-phase currents and three-phase voltages output by the inverter, perform Park transformation on the three-phase currents and three-phase voltages based on an internal electromotive force virtual phase angle, to acquire currents and voltages in a dq rotating coordinate system, and calculate active power P and reactive power Q actually output by the inverter based on the currents and voltages in the dq rotating coordinate system e and reactive power Q e ; the calculation process of the active power P e and reactive power Q e actually output by the inverter is as follows:

[0031] In the formula, P e and Q e are the active power and reactive power actually output by the inverter, u gd and u gq are the d-axis component and q-axis component of the terminal voltage of the inverter respectively; i Ld and i Lq are the d-axis component and q-axis component of the output current of the inverter respectively.

[0032] The virtual speed regulator control link is used to determine an active power change initial value of the converter; The virtual inertia and damping control and virtual frequency control link is used to obtain an active power reference value in combination of the active power change initial value of the converter and a preset active power static working point, and obtain an internal electromotive force virtual phase angle based on the active power reference value and the active power actually output by the inverter; the specific process of obtaining the internal electromotive force virtual phase angle based on the active power reference value and the active power actually output by the inverter is as follows: The internal electromotive force virtual phase angle is calculated by using the following formula:

[0033] In the formula, θ is the internal electromotive force virtual phase angle, ω n is a grid reference angular frequency; ω g is a grid angular frequency measurement value calculated from the voltage collected from the grid side; J is a virtual inertia; P ref represents the active power reference value; P e is the active power actually output by the inverter; K v is a virtual inertia control coefficient; K d is a virtual damping control coefficient; D pis the equivalent damping coefficient; s is a differential operator.

[0034] To suppress the frequency oscillation caused by large droop coefficient, an enhanced differential adaptive control quantity is configured. Based on the three major indicators of frequency stability (initial frequency change, maximum frequency drop, quasi-steady frequency), combined with the transient process overshoot, the influence of the control parameters in the virtual governor on the frequency fluctuation caused by power disturbance is analyzed, the cooperative control strategy is designed, and the virtual inertia control coefficient is adaptively adjusted based on the frequency fluctuation, as follows:

[0035] wherein, K v is the virtual inertia control coefficient, K v0 is the virtual inertia coefficient reference value; K d is the virtual damping coefficient; η is the differential control coefficient, which is 0.3 here, Δ f / Δ t is the frequency change rate in time Δ t , Δ t =0.1s, Δ f is the frequency change, Δ f 0 is the quasi-steady frequency deviation.

[0036] To verify the cooperative control effect, two working conditions are set according to whether the cooperative control is introduced, and the frequency dynamic response characteristics of the system are compared and analyzed when the droop control coefficient is 13 and 19 respectively. The system frequency dynamic response curve is shown in Figure 2 .

[0037] Figure 2 The simulation results show that the proposed differential cooperative control can effectively suppress the excessive transient oscillation caused by different frequency modulation coefficients, and improve the frequency minimum point and quasi-steady frequency deviation. The simulation verification results prove that compared with the traditional VSG control strategy, the proposed differential cooperative control strategy does not affect the original stability margin of the virtual synchronous machine, significantly improves the system frequency support capability and effectively suppresses the excessive oscillation of the frequency, which provides an effective solution to improve the frequency modulation performance of the high proportion of new energy access power grid.

[0038] The virtual excitation control link is used to obtain the internal potential amplitude of the converter based on the actual voltage signal, the reference voltage signal and the actual output reactive power of the inverter of the excitation voltage regulator; the internal potential amplitude of the converter is calculated by using the following formula:

[0039] wherein, E ref is the internal potential amplitude of the converter, Q setQ is the set reactive mechanical power; Q e K is the actual output reactive power of the inverter; K pQ K is the proportional control coefficient; K iQ D is the integral control coefficient; D q u is the virtual excitation coefficient; u t u is the actual voltage signal of the excitation voltage regulator; u n u is the reference voltage signal of the excitation voltage regulator; s is the differential operator.

[0040] A virtual impedance control link is used to calculate the reference voltage of the voltage-current double closed-loop control link based on the internal electromotive force virtual phase angle and the internal electromotive force amplitude; the calculation formula is as follows:

[0041] In the formula, and E d and E q are the d-axis component and the q-axis component of the reference voltage of the voltage-current double closed-loop control link in the dq coordinate system, respectively, E and E E ref are the d-axis component and the q-axis component of the internal electromotive force amplitude obtained through abc / dq transformation; L v L is the virtual impedance inductance parameter; ω ref is the internal electromotive force reference angular frequency, and are the d-axis component and the q-axis component of the main line current in the dq coordinate system after the filtering link.

[0042] A voltage-current double closed-loop control link is used to obtain the reference voltage of the converter based on the reference voltage of the voltage-current double closed-loop control link; the voltage-current double closed-loop control link includes a voltage inner loop control and a current inner loop control, the reference voltage of the voltage-current double closed-loop control link is subjected to the voltage inner loop control to obtain the reference current output by the voltage inner loop in the dq coordinate system, and the reference current output by the voltage inner loop in the dq coordinate system is subjected to the current inner loop control to obtain the reference voltage of the converter in the dq coordinate system.

[0043] The calculation formula is as follows:

[0044] In the formula, and are the d-axis component and the q-axis component of the reference current output by the voltage inner loop in the dq coordinate system, K pv and K ivis a proportional control coefficient of the inner voltage loop, and is an integral control coefficient of the inner voltage loop, and s is a differential operator, and are respectively a d-axis component and a q-axis component of the reference voltage of the voltage-current double closed loop control link in the dq coordinate system, U td and U tq are respectively a d-axis component and a q-axis component of the voltage value of the grid-connected point measured voltage obtained by Park transformation, C f is an equivalent capacitance parameter of the control link, ω ref is an inner potential reference angular frequency, and are respectively a d-axis component and a q-axis component of the main line current after the filtering link in the dq coordinate system.

[0045]

[0046] in the formula, and are respectively a d-axis component and a q-axis component of the reference voltage of the converter in the dq coordinate system, K pi and K ii is a proportional control coefficient of the inner current loop, and is an integral control coefficient of the inner current loop, and s is a differential operator, and are respectively a d-axis component and a q-axis component of the reference current output by the inner voltage loop in the dq coordinate system, i Ld , i Lq is the current value of the main line current obtained by Park transformation in the dq coordinate system, L f is an equivalent inductance parameter of the control link, U td and U tq are respectively a d-axis component and a q-axis component of the voltage value of the grid-connected point measured voltage obtained by Park transformation, ω ref is an inner potential reference angular frequency.

[0047] a PWM modulation module, configured to perform PWM modulation on the reference voltage of the converter to obtain a PWM signal for controlling a switching device of the converter, and specifically, taking the inner potential virtual angular frequency as a reference angular frequency , performing dq / abc transformation on the reference voltage of the converter in the dq coordinate system to obtain a reference voltage for PWM modulation, and performing PWM modulation on the reference voltage to obtain the PWM signal.

[0048] Those skilled in the art can understand that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software manner depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0049] The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall be considered as the protection scope of the present application.

Claims

1. A control system for connecting a grid-type virtual synchronous machine to a power grid, characterized in that, include: In the power calculation stage, the three-phase current and three-phase voltage of the inverter are obtained. The three-phase current and three-phase voltage are transformed by Park based on the virtual phase angle of the internal potential to obtain the current and voltage in the dq rotating coordinate system. Based on the current and voltage in the dq rotating coordinate system, the active power and reactive power of the inverter are calculated. The virtual speed governor control loop is used to determine the initial value of the active power change of the converter; The virtual inertia and damping control and virtual frequency regulation control loop is used to combine the initial value of the active power change of the converter and the preset active power static operating point to obtain the active power reference value, and to obtain the virtual phase angle of the internal potential based on the active power reference value and the actual active power output of the inverter. The virtual excitation control loop is used to obtain the internal potential amplitude of the converter based on the actual voltage signal of the excitation voltage regulator, the reference voltage signal, and the actual output reactive power of the inverter. The virtual impedance control loop is used to calculate the reference voltage of the voltage and current dual closed-loop control loop based on the virtual phase angle and amplitude of the internal potential. The voltage and current dual closed-loop control loop is used to obtain the reference voltage of the converter based on the reference voltage of the voltage and current dual closed-loop control loop; The PWM modulation module is used to modulate the reference voltage of the converter using PWM to obtain a PWM signal that controls the switching devices of the converter.

2. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 1, characterized in that, The actual active power output of the inverter P e and reactive power Q e The calculation process is as follows: In the formula, P e and Q e These represent the active power and reactive power actually output by the inverter, respectively. u td and u tq These are the d-axis and q-axis components of the inverter terminal voltage, respectively. i Ld and i Lq These are the d-axis and q-axis components of the inverter output current, respectively.

3. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 1, characterized in that, The specific method for obtaining the virtual phase angle of the internal potential based on the active power reference value and the actual active power output of the inverter is as follows: The virtual phase angle of the internal potential is calculated using the following formula: In the formula, The virtual phase angle of the internal potential. ω n This is the reference angular frequency for the power grid. ω g The measured value of the grid angular frequency is obtained by collecting voltage data from the grid side. J This is virtual inertia; P ref This represents the reference value for active power. P e This refers to the actual active power output of the inverter. K v These are virtual inertial control coefficients; K d This is the virtual damping control coefficient; D p is the equivalent damping coefficient; s is the differential operator.

4. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 1, characterized in that, The specific method for obtaining the converter's internal potential amplitude based on the actual voltage signal of the excitation voltage regulator, the reference voltage signal, and the actual output reactive power of the inverter is as follows: The amplitude of the internal potential of the converter can be calculated using the following formula: In the formula, E ref The internal potential amplitude of the converter. Q set The set reactive mechanical power; Q e This refers to the actual reactive power output of the inverter. K pQ This is the proportional control coefficient. K iQ These are integral control coefficients; D q This is the virtual excitation coefficient; u t This is the actual voltage signal of the excitation voltage regulator; u n is the reference voltage signal for the excitation voltage regulator; s is the differential operator.

5. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 1, characterized in that, The reference voltage for the voltage-current dual closed-loop control loop calculated based on the virtual phase angle and amplitude of the internal potential is specifically: In the formula, and These represent the d-axis and q-axis components of the reference voltage in the voltage-current dual closed-loop control loop, respectively, in the dq coordinate system. E d and E q These are the virtual phase angles of the converter's internal potential. and internal potential amplitude E ref The d-axis and q-axis components of the internal potential amplitude obtained by the abc / dq transformation; L v These are virtual impedance and inductance parameters; ω ref The internal potential reference angular frequency, and These represent the d-axis and q-axis components of the main line current in the dq coordinate system after filtering.

6. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 1, characterized in that, The voltage and current dual closed-loop control loop includes voltage inner loop control and current inner loop control. Specifically, the reference voltage of the converter is obtained based on the reference voltage obtained from the voltage and current dual closed-loop control loop as follows: The reference voltage of the voltage and current dual closed-loop control loop is used to obtain the reference current output by the voltage inner loop in the dq coordinate system. The reference current output by the voltage inner loop in the dq coordinate system is used to obtain the reference voltage of the converter in the dq coordinate system through the current inner loop control.

7. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 6, characterized in that, The reference voltage of the voltage-current dual closed-loop control loop is used to obtain the reference current output by the inner voltage loop in the dq coordinate system, which is specifically as follows: In the formula, and These represent the d-axis and q-axis components of the reference current output by the inner voltage loop in the dq coordinate system. K pv and K iv These are the proportional control coefficient and integral control coefficient for the voltage inner loop; s is a differential operator, and These represent the d-axis and q-axis components of the reference voltage in the voltage-current dual closed-loop control loop, respectively, in the dq coordinate system. U td and U tq These are the d-axis and q-axis components of the voltage value measured at the grid connection point and obtained by Park transformation in the dq coordinate system, respectively. C f To control the equivalent capacitance parameters of the circuit; ω ref The internal potential reference angular frequency, and These represent the d-axis and q-axis components of the main line current in the dq coordinate system after filtering.

8. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 6, characterized in that, The reference current output by the voltage inner loop in the dq coordinate system is used to obtain the reference voltage of the converter in the dq coordinate system through the current inner loop control. Specifically: In the formula, and These represent the d-axis and q-axis components of the converter's reference voltage in the dq coordinate system. K pi and K ii These are the proportional control coefficient and integral control coefficient for the inner current loop, respectively, and s is the differential operator. and These represent the d-axis and q-axis components of the reference current output by the inner voltage loop in the dq coordinate system. i Ld , i Lq The value of the main line current in the dq coordinate system obtained by Park transformation. L f To control the equivalent inductance parameters of the circuit, U td and U tq These represent the d-axis and q-axis components of the voltage value measured at the grid connection point and obtained through Park transformation in the dq coordinate system. ω ref The internal potential reference angular frequency.

9. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 1, characterized in that, The specific steps of PWM modulation of the converter's reference voltage are as follows: Using the virtual angular frequency of internal potential as the reference angular frequency The reference voltage of the converter in the dq coordinate system is transformed by dq / abc to obtain the reference voltage for PWM modulation, and then PWM modulation is performed on it to obtain the PWM signal.

10. The control system for grid-type virtual synchronous machine access to the power grid as described in claim 3, characterized in that, The virtual inertial control coefficients are adaptively adjusted based on frequency fluctuations, as follows: In the formula, K v These are virtual inertial control coefficients. K v0 This serves as the baseline value for the virtual inertia coefficient. K d This is the virtual damping coefficient; η The differential control coefficient, Δ f / Δ t For time Δ t Rate of change of frequency within, Δ f Δ is the frequency change. f 0 represents the quasi-steady-state frequency deviation.

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