Virtual synchronous machine grid connection control method and device and readable storage medium

Abstract

The application provides a virtual synchronous machine grid-connected control method and device and a readable storage medium, and relates to the technical field of electric power. The method comprises the following steps: calculating grid-connected active power and actual reactive power according to inverter parameters and grid parameters of previous grid-connected control; determining the output voltage of the inverter according to the actual reactive power and reference reactive power; inputting the grid-connected active power, reference active power and rated angular frequency into a first-order low-pass filter module to obtain a frequency deviation and a frequency change rate, and adaptively adjusting the virtual inertia according to a power difference and the frequency deviation; updating the output angular frequency of the inverter according to the sum of the frequency deviation and the rated angular frequency; performing voltage-current double closed-loop control on the output voltage and the output angular frequency to obtain a modulation wave signal, performing sinusoidal pulse width modulation based on the modulation wave signal to obtain a switching control signal of the inverter. In this way, active power oscillation is eliminated, active steady-state deviation is reduced, and the frequency deviation and the frequency change rate are effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of power technology, and more specifically, to a virtual synchronous machine grid-connected control method, apparatus, and readable storage medium. Background Technology

[0002] With the continuous development of new energy technologies, distributed energy sources such as photovoltaics, wind power, and energy storage are increasingly being connected to the power system through inverters. Unlike synchronous generators, inverters cannot provide inertia and damping support to the system when distributed energy sources experience fluctuations, thus affecting the stable operation of the system.

[0003] To address the aforementioned issues, some scholars have proposed the Virtual Synchronous Generator (VSG) and its related control strategies. By simulating the rotor motion characteristics of a synchronous generator, the inverter acquires inertial and damping characteristics, thereby enhancing the stability of system power and frequency.

[0004] VSG improves transient response characteristics by introducing virtual inertia, but it also transforms the system into a second-order system, leading to oscillations and overshoot. VSG addresses these oscillations by introducing damping. However, when grid-side frequency disturbances occur, greater damping increases the system's active power steady-state deviation, while less damping cannot effectively suppress oscillations in the system's output active power and output frequency. Summary of the Invention

[0005] The present invention aims to at least solve the technical problems existing in the prior art or related technologies, where large damping will increase the steady-state deviation of the system's active power when the grid-side frequency is disturbed, while small damping cannot effectively suppress the oscillation of the system's output active power and output frequency.

[0006] Therefore, the first aspect of the present invention is to propose a virtual synchronous machine grid-connected control method.

[0007] A second aspect of the present invention is to provide a virtual synchronous machine grid-connected control device.

[0008] A third aspect of the present invention is to provide another virtual synchronous machine grid-connected control device.

[0009] A fourth aspect of the present invention is to provide a readable storage medium.

[0010] In view of this, according to a first aspect of the present invention, a virtual synchronous machine grid-connected control method is proposed, the method comprising: calculating the grid-connected active power of the virtual synchronous machine based on the inverter parameters and grid parameters of the previous grid-connected control process. and actual reactive power Inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency After obtaining the frequency difference, the frequency difference is then integrated; based on the actual reactive power... and reference reactive power Determine the output voltage of the inverter. ; The active power connected to the grid Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency In the first-order low-pass filter module, the virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation Perform adaptive adjustments; based on frequency deviation With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. ; Regarding the output voltage and output angular frequency Voltage and current dual closed-loop control is performed to obtain a modulation wave signal. Based on the modulation wave signal, sinusoidal pulse width modulation is performed to obtain the inverter's switching control signal, which is used to drive the switching transistors in the inverter.

[0011] In the virtual synchronous machine grid-connected control method provided by this invention, during each grid-connected control process, the grid-connected active power of the virtual synchronous machine is calculated based on the inverter parameters and grid parameters from the previous grid-connected control. and actual reactive power The inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency After obtaining the frequency difference, it is then integrated. Further, based on the actual reactive power... and reference reactive power Determine the output voltage of the inverter. Furthermore, the active power connected to the grid... Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency Among them, virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation Adaptive adjustments are made. Furthermore, based on the frequency deviation... With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Updated output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. Furthermore, the output voltage and the updated output angular frequency Through voltage and current dual closed-loop control and SPWM (Sinusoidal Pulse Width Modulation), the switching control signal of the inverter for each grid-connected control is obtained. Specifically, for the output voltage... and output angular frequency A novel active power control structure is proposed, which utilizes voltage and current dual closed-loop control to obtain a modulation wave signal. Based on this signal, sinusoidal pulse width modulation is performed to generate the inverter's switching control signal, which drives the switching transistors in the inverter. This structure eliminates active power oscillations, reduces active power steady-state deviation, and effectively suppresses frequency deviation and rate of frequency change through transient compensation and virtual inertia adaptive control.

[0012] In some technical solutions, optionally, the rotor motion equation corresponding to the first-order low-pass filter module is: ;in, Represents virtual inertia. Indicates the rated angular frequency. Indicates the rate of change of frequency. Indicates the reference active power. Indicates the power compensation coefficient. Let s denote the transient compensation time constant, s denote the differential operator, and m denote the frequency compensation coefficient. Indicates the active power connected to the grid. This represents the active power droop coefficient. Indicates the damping coefficient. This indicates frequency deviation.

[0013] In this technical solution, the rotor motion equation corresponding to the first-order low-pass filter module is:

[0014] ;

[0015] in, Represents virtual inertia. Indicates the rated angular frequency. Indicates the rate of change of frequency. Indicates the reference active power. Indicates the power compensation coefficient. Let s denote the transient compensation time constant, s denote the differential operator, and m denote the frequency compensation coefficient. Indicates the active power connected to the grid. This represents the active power droop coefficient. Indicates the damping coefficient. This indicates frequency deviation.

[0016] Based on the above rotor motion equations, when the system approaches steady state, i.e., when s approaches 0, The steady-state value is 0, which has no effect on the steady state of the system.

[0017] Thus, from the perspective of changing the active power control structure, a novel active power control structure based on transient compensation is proposed. By using a first-order lag module, a transiently existing power is constructed to compensate for the active power output of the inverter, thereby reducing power overshoot. Furthermore, the output frequency is compensated through proportional calculation to reduce frequency overshoot.

[0018] In some technical solutions, optionally, the active closed-loop response small-signal transfer function corresponding to the first-order low-pass filter module is: ;in, Indicates the steady-state deviation of grid-connected active power. Indicates the reference active power deviation. The frequency deviation of the power grid is represented by s, the differential operator is represented by s, and a, b, and c are calculation coefficients. , , K is the synchronization voltage coefficient. , This refers to the voltage amplitude of the power grid. For output voltage, This is the equivalent reactance of the line.

[0019] In this technical solution, the active closed-loop response small-signal transfer function corresponding to the first-order low-pass filter module is:

[0020] ;

[0021] in, Indicates the steady-state deviation of grid-connected active power. Indicates the reference active power deviation. The frequency deviation of the power grid is represented by s, the differential operator is represented by s, and a, b, and c are calculation coefficients. , , K is the synchronization voltage coefficient. , This refers to the voltage amplitude of the power grid. For output voltage, This is the equivalent reactance of the line.

[0022] Based on the above active closed-loop response small-signal transfer function, active power and grid frequency disturbances will not affect the steady-state error of the system.

[0023] In some technical solutions, optionally, frequency deviation The calculation formula is: Rate of change of frequency The calculation formula is: ; where s represents the differential operator.

[0024] In this technical solution, frequency deviation The calculation formula is:

[0025] .

[0026] Furthermore, the rate of change of frequency The calculation formula is:

[0027] .

[0028] Where s represents the differential operator.

[0029] Based on the above calculation formula, it can suppress more effectively than traditional VSG. and Furthermore, when virtual inertia When adaptively increased, it will further suppress and .

[0030] In some technical solutions, virtual inertia may optionally be used. Based on reference active power With grid-connected active power power difference Frequency deviation Adaptive adjustments are made, including: in power difference Frequency deviation If the product is greater than 0, increase the virtual inertia. ; in power difference Frequency deviation When the product is less than or equal to 0, reduce the virtual inertia. .

[0031] In this technical solution, based on the reference active power With grid-connected active power power difference Frequency deviation For virtual inertia When performing adaptive adjustment, at power difference Frequency deviation If the product is greater than 0, increase the virtual inertia. To reduce the rate of change of frequency At the same time, suppress frequency deviation Furthermore, in the power difference Frequency deviation When the product is less than or equal to 0, reduce the virtual inertia. To increase the rate of change of frequency This accelerates the frequency recovery to a stable value, allowing the output frequency to return to its stable value as quickly as possible. By incorporating virtual inertia adaptive control and appropriately adjusting the parameters of the virtual inertia, the frequency change rate can be reduced while further minimizing frequency overshoot, thus improving the frequency abrupt changes and overshoot problems caused by fluctuations in reference active power.

[0032] In some technical solutions, virtual inertia may optionally be used. The calculation formula is: ;in, This represents the virtual inertia of the system during stable operation, where e is the natural constant. This represents the virtual inertia adjustment coefficient. Indicates reference active power With grid-connected active power The power difference.

[0033] In this technical solution, virtual inertia The calculation formula is:

[0034] ;

[0035] in, This represents the virtual inertia of the system during stable operation, where e is the natural constant. This represents the virtual inertia adjustment coefficient. Indicates reference active power With grid-connected active power The power difference.

[0036] Based on the above calculation formula, virtual inertia adaptive control can be carried out. By reasonably adjusting the parameters of virtual inertia, the frequency overshoot can be further reduced while reducing the frequency change rate, thus improving the frequency mutation and overshoot problems caused by the fluctuation of reference active power.

[0037] In some technical solutions, virtual inertia may optionally be used. satisfy: ;in, Pi This indicates the maximum output power of the inverter. This represents the maximum rate of change of frequency.

[0038] In this technical solution, virtual inertia satisfy:

[0039] ;

[0040] in, Pi This indicates the maximum output power of the inverter. This represents the maximum rate of change of frequency.

[0041] Based on the above limitations, the virtual inertia for stable system operation should be set. Then, a suitable virtual inertia adjustment coefficient can be selected. This is to make full use of the inverter's output power.

[0042] According to a second aspect of the present invention, a virtual synchronous machine grid-connected control device is provided, the device comprising: a processing unit, configured to calculate the grid-connected active power of the virtual synchronous machine based on the inverter parameters and grid parameters of the previous grid-connected control during each grid-connected control process. and actual reactive power Inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency After obtaining the frequency difference, the frequency difference is then integrated to obtain the result; the processing unit is also used to determine the actual reactive power. and reference reactive power Determine the output voltage of the inverter. The processing unit is also used to process the grid-connected active power. Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency In the first-order low-pass filter module, the virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation The processing unit also performs adaptive adjustments based on frequency deviations. With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. The processing unit is also used to process the output voltage. and output angular frequency Voltage and current dual closed-loop control is performed to obtain a modulation wave signal. Based on the modulation wave signal, sinusoidal pulse width modulation is performed to obtain the inverter's switching control signal, which is used to drive the switching transistors in the inverter.

[0043] In the virtual synchronous machine grid-connected control device provided by this invention, the processing unit calculates the grid-connected active power of the virtual synchronous machine based on the inverter parameters and grid parameters from the previous grid-connected control process. and actual reactive power The inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency After obtaining the frequency difference, it is then integrated. Further, the processing unit determines the frequency difference based on the actual reactive power. and reference reactive power Determine the output voltage of the inverter. Furthermore, the processing unit will connect the grid-connected active power. Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency Among them, virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation Adaptive adjustments are made. Furthermore, the processing unit adjusts based on the frequency deviation. With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. Furthermore, the processing unit will output voltage. and the updated output angular frequency Through voltage and current dual closed-loop control and SPWM, the switching control signal of the inverter for each grid-connected control is obtained. Specifically, for the output voltage... and output angular frequency A novel active power control structure is proposed, which utilizes voltage and current dual closed-loop control to obtain a modulation wave signal. Based on this signal, sinusoidal pulse width modulation is performed to generate the inverter's switching control signal, which drives the switching transistors in the inverter. This structure eliminates active power oscillations, reduces active power steady-state deviation, and effectively suppresses frequency deviation and rate of frequency change through transient compensation and virtual inertia adaptive control.

[0044] According to a third aspect of the present invention, another virtual synchronous machine grid-connected control device is proposed, comprising a processor and a memory. The memory stores a program or instructions executable on the processor. When the program or instructions are executed by the processor, they implement the steps of the virtual synchronous machine grid-connected control method as described in any of the above-described technical solutions. Therefore, the virtual synchronous machine grid-connected control device proposed in the third aspect of the present invention possesses all the beneficial effects of the virtual synchronous machine grid-connected control method in any of the technical solutions of the first aspect described above, which will not be elaborated further here.

[0045] According to a fourth aspect of the present invention, a readable storage medium is provided, on which a program or instructions are stored, which, when executed by a processor, implement the virtual synchronous machine grid-connected control method as described in any of the above-described technical solutions. Therefore, the readable storage medium proposed in the fourth aspect of the present invention possesses all the beneficial effects of the virtual synchronous machine grid-connected control method in any of the technical solutions of the first aspect, and will not be elaborated further here.

[0046] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0047] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0048] Figure 1 A flowchart illustrating the virtual synchronous machine grid-connected control method according to an embodiment of the present invention is shown;

[0049] Figure 2 The topology of a traditional three-phase VSG grid-connected inverter is shown.

[0050] Figure 3 The block diagram of a traditional VSG active power closed-loop control system is shown.

[0051] Figure 4 One of the pole distribution diagrams of a traditional VSG active power closed-loop system is shown;

[0052] Figure 5 The second pole distribution diagram of a traditional VSG active power closed-loop system is shown.

[0053] Figure 6 The diagram shows a block diagram of the VSG active power closed-loop control based on active power transient compensation according to an embodiment of the present invention.

[0054] Figure 7 The power angle curve of the synchronous generator is shown;

[0055] Figure 8 The frequency oscillation curve of the synchronous generator is shown.

[0056] Figure 9 One of the simulation results of the virtual synchronous machine grid-connected control method according to an embodiment of the present invention is shown;

[0057] Figure 10 The second schematic diagram shows the simulation results of the virtual synchronous machine grid-connected control method according to an embodiment of the present invention;

[0058] Figure 11 This figure shows one of the structural block diagrams of a virtual synchronous machine grid-connected control device according to an embodiment of the present invention;

[0059] Figure 12 The second structural block diagram of the virtual synchronous machine grid-connected control device according to an embodiment of the present invention is shown. Detailed Implementation

[0060] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0061] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0062] The following is combined Figures 1 to 12 The present application provides a detailed description of the virtual synchronous machine grid-connected control method, apparatus, and readable storage medium provided in the embodiments of this application through specific implementation methods and application scenarios.

[0063] In one embodiment of the present invention, such as Figure 1 As shown, the virtual synchronous machine grid-connected control method may specifically include the following steps 102 to 110:

[0064] Step 102: During each grid connection control process, calculate the grid-connected active power and actual reactive power of the virtual synchronous machine based on the inverter parameters and grid parameters of the previous grid connection control.

[0065] Step 104: Determine the output voltage of the inverter based on the actual reactive power and the reference reactive power;

[0066] Step 106: Input the grid-connected active power, reference active power, and rated angular frequency into a first-order low-pass filter module containing damping coefficient, virtual inertia, active power droop coefficient, transient compensation time constant, power compensation coefficient, and frequency compensation coefficient. Calculate the frequency deviation and frequency change rate of the virtual synchronous machine based on the first-order low-pass filter module. In the first-order low-pass filter module, the virtual inertia is adaptively adjusted according to the power difference and frequency deviation between the reference active power and the grid-connected active power.

[0067] Step 108: Update the inverter's output angular frequency based on the sum of the frequency deviation and the rated angular frequency, and synchronize the output angular frequency with the grid frequency.

[0068] Step 110: Perform voltage and current dual closed-loop control on the output voltage and output angular frequency to obtain the modulation wave signal. Based on the modulation wave signal, perform sinusoidal pulse width modulation to obtain the inverter's switching control signal. The switching control signal is used to drive the switching transistors in the inverter to work.

[0069] In the virtual synchronous machine grid-connected control method provided by this invention, during each grid-connected control process, the grid-connected active power of the virtual synchronous machine is calculated based on the inverter parameters and grid parameters from the previous grid-connected control. and actual reactive power The inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency After obtaining the frequency difference, it is then integrated. Further, based on the actual reactive power... and reference reactive power Determine the output voltage of the inverter. Furthermore, the active power connected to the grid... Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency Among them, virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation Adaptive adjustments are made. Furthermore, based on the frequency deviation... With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. Furthermore, the output voltage and the updated output angular frequency Through voltage-current dual closed-loop control and SPWM, the inverter's switching control signal for each grid-connected control is obtained. Specifically, voltage-current dual closed-loop control is performed on the output voltage and output angular frequency to obtain a modulation wave signal. Based on the modulation wave signal, sinusoidal pulse width modulation is performed to obtain the inverter's switching control signal, which is used to drive the switching transistors in the inverter. Thus, a novel active power control structure is proposed. Through transient compensation and virtual inertia adaptive control, active power oscillations are eliminated, active power steady-state deviation is reduced, and frequency deviation and frequency change rate are effectively suppressed.

[0070] Understandably, the main circuit topology and control structure diagram of a traditional three-phase VSG inverter can be as follows: Figure 2 As shown. Among them, as Figure 2 As shown, the main circuit topology is a three-phase full-bridge inverter. It is a DC voltage source. For DC bus capacitors, and These are the filter inductor and its parasitic resistance, respectively. For filtering capacitors, For the inductance of the power grid line, For the resistance of the power grid line, For VSG output current, The voltage at the grid connection point. The voltage is the grid voltage. S1, S2, S3, S4, S5, and S6 are all power switching devices. Furthermore, the control structure includes an active power control section and a reactive voltage control section. The active power control section includes an active power droop control section and a rotor motion equation section. Among them, and 1 / These are all related terms in the rotor motion equation, used to simulate the rotor motion characteristics of a synchronous generator, enabling the inverter to have characteristics such as frequency regulation similar to those of a synchronous generator.

[0071] Specifically, the active power control section combines active power droop control and VSG inertia damping control. Active power droop control, by simulating the governor of a synchronous generator, achieves primary frequency regulation for the distributed power source. The rotor motion equation introduces virtual inertia and damping coefficients into the active power control, enabling the VSG to simulate the inertial and damping characteristics of a traditional synchronous generator. This enhances the system's ability to suppress small disturbances, reduces system oscillations, and improves the system's dynamic stability.

[0072] The active power droop control equation can be expressed as:

[0073] (1)

[0074] in, For mechanical power, For reference active power, This is the active power droop coefficient. The inverter's output angular frequency. This is the rated angular frequency.

[0075] The rotor motion equation of a traditional VSG can be expressed as:

[0076] (2)

[0077] in, For virtual inertia, The rate of change of frequency, For grid-connected active power, is the damping coefficient.

[0078] Combining equations (1) and (2), the active power control equation for the VSG can be obtained as follows:

[0079] (3)

[0080] Furthermore, the reactive voltage control is controlled by the excitation controller, and its control equation can be expressed as:

[0081] (4)

[0082] in, For output voltage, This represents the actual reactive power. For reference reactive power, This is the reference amplitude of the rated voltage. This is the reactive power droop coefficient.

[0083] Furthermore, based on the principle of line power transmission, neglecting the equivalent impedance between the inverter and the grid, the grid-connected active power delivered by the inverter to the grid... It can be represented as:

[0084] (5)

[0085] in, This is the grid voltage. For output voltage, For the line equivalent reactance, The power factor angle, Synchronization voltage coefficient, , The inverter's output angular frequency. For the power grid frequency, This represents the differential operator. When the system is in steady state... .

[0086] Furthermore, combining equations (1), (2), and (4) and Figure 2 The block diagram of the active power control section in the VSG system can be used to derive the block diagram of the traditional VSG active power closed-loop control system, such as... Figure 3 As shown.

[0087] Depend on Figure 3 Therefore, the traditional VSG active power closed-loop control is based on the reference active power. and grid frequency When a disturbance occurs, the grid-connected active power The expression for the closed-loop small-signal transfer function is:

[0088] (6)

[0089] in, For active power deviation, For reference, active power deviation, For the frequency deviation of the power grid, It is a differential operator.

[0090] Furthermore, when the grid frequency fluctuates, the traditional VSG active power closed-loop control system, in order to maintain synchronization with the grid frequency, will cause a steady-state deviation in the active power output of the inverter. When the system tends to a steady state, the expression for the active power deviation in the steady state can be obtained from equation (6):

[0091] (7)

[0092] From equation (7), it can be seen that when the power grid frequency When changes occur, the steady-state deviation of the active power output of the inverter and the damping coefficient and active droop coefficient They are positively correlated. Therefore, in order to reduce steady-state deviation, the damping coefficient should be minimized as much as possible. .

[0093] As can be seen from equation (6), virtual inertia The introduction of this technology transforms the system into a second-order system, giving the VSG power oscillation characteristics similar to those of a synchronous machine. The natural oscillation angular frequency corresponding to this second-order system... Damping ratio The expression is:

[0094] (8)

[0095] From equation (8), we can obtain the natural oscillation angular frequency. Only with virtual inertia Negative correlation, damping ratio and damping coefficient They are positively correlated, and the damping ratio and virtual inertia There is a negative correlation. When the damping coefficient When the inertia remains constant, increase the virtual inertia. This will lead to the natural oscillation angular frequency Damping ratio All decrease, thus slowing down the dynamic response of VSG grid-connected active power, making active power oscillation more severe, and increasing active power overshoot; while when virtual inertia When the damping coefficient remains constant, increase the damping coefficient. This will lead to a natural oscillation angular frequency. Constant, damping ratio This increases the active power oscillation, thereby reducing the active power overshoot and improving system stability.

[0096] Furthermore, virtual inertia and damping coefficient The parameter settings affect the pole locations of the closed-loop small-signal transfer function. The main parameters of a traditional VSG grid-connected inverter are shown in Table 1 below. Substituting these parameters into... Figure 2 In the relevant formulas, virtual inertia is set. and damping coefficient By setting the parameters and varying them according to a set step size, the virtual inertia can be obtained. and damping coefficient When the dynamic changes occur, the pole distribution diagram of a traditional VSG active power closed-loop system is as follows: Figure 4 and Figure 5 As shown.

[0097] in, Figure 4 Damping coefficient Invariant, virtual inertia When the pole distribution changes, the pole distribution diagram of the traditional VSG active power closed-loop system is as follows: Figure 4 As shown, at the damping coefficient With the virtual inertia remaining unchanged, As the virtual inertia increases, the pair of conjugate poles S1 and S2 move closer to the imaginary axis. According to automatic control theory, the closer the poles are to the imaginary axis, the more pronounced the system oscillations become; that is, as the virtual inertia increases... As the magnitude of the oscillation increases, the dynamic oscillation of the system also increases, the overshoot becomes larger, and the system stability decreases.

[0098] Furthermore, Figure 5 Damping coefficient Changes, virtual inertia When the pole distribution remains unchanged, the pole distribution diagram of the traditional VSG active power closed-loop system is as follows: Figure 5 As shown, in virtual inertia With the damping coefficient remaining constant, As the value increases, poles S1 and S2 move away from the imaginary axis and gradually approach the negative real axis, eventually becoming negative real poles that tend to move away from and towards the imaginary axis. The damping ratio... As the damping increases, the system changes from an underdamped state to an overdamped state, suppressing dynamic oscillations and improving system stability.

[0099] Table 1

[0100]

[0101] Based on the above analysis, it can be seen that for traditional VSG grid-connected control systems, virtual inertia... and damping coefficient It has a direct impact on the dynamic performance and stability of the system. Among these, when the virtual inertia... If the virtual inertia is set too low, the VSG's regulation effect on the grid frequency will weaken, leading to an increase in transient frequency deviation when the grid is disturbed. Conversely, if the virtual inertia is set too low... Setting the damping coefficient too high increases the dynamic oscillation amplitude of the system, reducing its stability and increasing the time it takes for the system to return to equilibrium. Furthermore, when the damping coefficient... If the damping coefficient is set too low, it will be difficult to suppress the dynamic oscillations of the system; and the damping coefficient... Setting it too high will increase the steady-state deviation of active power when the grid changes frequency, and will also slow down the system response speed, resulting in poor system stability. Therefore, directly adjusting the virtual inertia... and damping coefficient The parameters cannot resolve the contradiction between the dynamic and static performance of VSG, and cannot effectively alleviate the active power oscillation problem of the system.

[0102] In other words, based on the above analysis of the basic control principle of traditional energy storage VSG and the grid-connected active power response characteristics of traditional VSG, it can be seen that: VSG improves transient response characteristics by introducing virtual inertia, but it also turns the system into a second-order system, thus causing oscillations and overshoot problems. VSG introduces damping to suppress oscillation problems. However, when grid-side frequency disturbances occur, larger damping will increase the system's active power steady-state deviation, while smaller damping cannot effectively suppress oscillations in system output active power and output frequency. To address this issue, one control strategy involves using algorithms to dynamically adjust the parameters of virtual inertia and damping coefficients, achieving adaptive control of virtual inertia and damping coefficients to reduce active power overshoot and frequency error. While this strategy can eliminate active power oscillations and reduce frequency error, the presence of damping increases the steady-state error of active power during frequency fluctuations. Another control strategy starts by modifying the active power control structure, proposing a transient equivalent damping method. By increasing the equivalent damping ratio during the transient process, the transient characteristics of the VSG are improved, addressing both the problems of excessive active power oscillations and frequency error while eliminating the impact of damping on the steady-state error of active power.

[0103] Based on this, this invention proposes a VSG grid-connected active power oscillation suppression strategy based on transient compensation and virtual inertia adaptation. This strategy focuses on addressing the problem of the difficulty in simultaneously controlling dynamic oscillations and steady-state deviations of output active power in grid systems using virtual synchronous generator technology under active power commands and grid frequency disturbances. Specifically, in the virtual synchronous generator grid-connected control method provided by this invention, on the one hand, from the perspective of changing the active power control structure, a novel active power control structure based on transient compensation is proposed, such as... Figure 6 As shown, using the damping coefficient Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The first-order lag module with frequency compensation coefficient m constructs a transient power in the original VSG active power control structure to compensate for the inverter output active power, reducing power overshoot. It also compensates for inverter output frequency through proportional calculation, reducing frequency overshoot. Furthermore, virtual inertia adaptive control is added. By reasonably adjusting the parameters of the virtual inertia, it reduces the frequency change rate and further reduces frequency overshoot, improving the frequency abrupt changes and overshoot problems caused by reference active power fluctuations. Thus, compared to traditional VSG control strategies, the virtual synchronous machine grid-connected control method provided by this invention, through transient compensation and virtual inertia adaptive control, eliminates active power oscillations, effectively suppresses frequency deviation and frequency change rate, reduces frequency deviation, eliminates damping in the VSG, and reduces the steady-state error of active power caused by frequency fluctuations.

[0104] In some embodiments of the present invention, optionally, based on Figure 6 The active power control structure, the rotor motion equation corresponding to the first-order low-pass filter module is:

[0105] (9)

[0106] in, Represents virtual inertia. Indicates the rated angular frequency. Indicates the rate of change of frequency. Indicates the reference active power. Indicates the power compensation coefficient. Let s denote the transient compensation time constant, s denote the differential operator, and m denote the frequency compensation coefficient. Indicates the active power connected to the grid. This represents the active power droop coefficient. Indicates the damping coefficient. This represents the frequency deviation. Based on the above rotor motion equations, when the system approaches steady state, i.e., when s approaches 0, The steady-state value is 0, which has no effect on the steady state of the system.

[0107] Thus, from the perspective of changing the active power control structure, a novel active power control structure based on transient compensation is proposed. By using a first-order lag module, a transiently existing power is constructed to compensate for the active power output of the inverter, thereby reducing power overshoot. Furthermore, the output frequency is compensated through proportional calculation to reduce frequency overshoot.

[0108] In some embodiments of the present invention, optionally, based on Figure 6 The active power control structure, the small-signal transfer function of the virtual synchronous machine under active power and grid frequency disturbances is:

[0109] (10)

[0110] in, Indicates the steady-state deviation of grid-connected active power. Indicates the reference active power deviation. The frequency deviation of the power grid is represented by s, the differential operator is represented by s, and a, b, and c are calculation coefficients. , , K is the synchronization voltage coefficient. , This refers to the voltage amplitude of the power grid. For output voltage, This represents the line's equivalent reactance. Based on the above active power closed-loop response small-signal transfer function, disturbances in active power and grid frequency will not affect the system's steady-state error.

[0111] In some embodiments of the present invention, optionally, frequency deviation The calculation formula is:

[0112] (11)

[0113] Furthermore, the rate of change of frequency The calculation formula is:

[0114] (12)

[0115] Where s represents the differential operator.

[0116] Based on the above calculation formula, it can suppress more effectively than traditional VSG. and Furthermore, when virtual inertia When adaptively increased, it will further suppress and .

[0117] In some embodiments of the present invention, optionally, virtual inertia. Based on reference active power With grid-connected active power power difference Frequency deviation When performing adaptive adjustment, at the power difference Frequency deviation If the product is greater than 0, increase the virtual inertia. ; in power difference Frequency deviation When the product is less than or equal to 0, reduce the virtual inertia. .

[0118] From equation (10) above, we can obtain that when the system tends to steady state, the grid-connected active power steady-state deviation of the VSG is:

[0119] (13)

[0120] From equation (13), it can be seen that the steady-state deviation of the grid-connected active power is... In the middle, the damping coefficient With active droop coefficient There is coupling; this can be addressed by setting the damping coefficient. This can eliminate the coupling relationship between the two and reduce the steady-state deviation of grid-connected active power. Become This reduces the active steady-state deviation of the system when the frequency changes.

[0121] Furthermore, this can be achieved by appropriately setting the virtual inertia. The value of the virtual inertia can be used to further adjust the dynamic performance and stability of the system. In the virtual synchronous machine grid-connected control method provided by this invention, virtual inertia adaptive control is proposed, which can adjust the virtual inertia appropriately. The parameter values ​​are adjusted to enhance the frequency support capability of the VSG, thereby further reducing the active power oscillation amplitude.

[0122] Specifically, let , Arrange equation (3) to obtain:

[0123] (14)

[0124] Furthermore, the power angle curve and frequency oscillation curve of the synchronous generator are respectively as follows: Figure 7 and Figure 8 As shown, where, Indicates the angle of action. , and All The specific values, , Both P and t represent specific values ​​of active power, and t represents time, where t0, t1, t2, t3, and t4 are specific values ​​of t. , and Both are output angular frequencies The specific value to be taken. For example Figure 7 and Figure 8 As shown, active power from Increase to The process is not instantaneous, but involves a process from oscillation to stability, and the increase in active power will also cause a change in the VSG output angular frequency. Based on this, the oscillation process is divided into four intervals, namely interval ①, interval ②, interval ③ and interval ④, and analyzed in conjunction with equation (14). Specifically, in interval ①, >0, >0, <0, in order to suppress This can be achieved by increasing the virtual inertia. To reduce In order to slow down the frequency change while making This reduces the frequency deviation, thus suppressing it; in interval ②, >0, <0, If the value is less than 0, the virtual inertia can be reduced to bring the output angular frequency back to a stable value as quickly as possible. ,make Increasing the value accelerates the rate at which the frequency recovers to a stable value. The selection principle for virtual inertia in intervals ③ and ④ is similar to that in intervals ① and ②.

[0125] Based on this, virtual inertia The adaptive adjustment rules are shown in Table 2 below.

[0126] Table 2

[0127]

[0128] It should be noted that in the above virtual inertia In the adaptive adjustment rule, the frequency change rate is... As a means of adjusting virtual inertia The reference index introduces both harmonics and noise into the system, and further amplifies the interference of the differential term when large disturbances occur. As shown in Table 2, the reference active power... With grid-connected active power power difference With the rate of change of frequency Since the changing trends are the same, the virtual synchronous machine grid-connected control method provided by this invention utilizes the power difference. Replace the rate of change of frequency To avoid introducing the rate of change of frequency The resulting harmonics and noise.

[0129] Specifically, in the virtual synchronous machine grid-connected control method provided by this invention, based on the reference active power... With grid-connected active power power difference Frequency deviation For virtual inertia When performing adaptive adjustment, at power difference Frequency deviation If the product is greater than 0, increase the virtual inertia. To reduce the rate of change of frequency At the same time, suppress frequency deviation Furthermore, in the power difference Frequency deviation When the product is less than or equal to 0, reduce the virtual inertia. To increase the rate of change of frequency This accelerates the frequency recovery to a stable value, allowing the output frequency to return to its stable value as quickly as possible. By incorporating virtual inertia adaptive control and appropriately adjusting the parameters of the virtual inertia, the frequency change rate can be reduced while further minimizing frequency overshoot, thus improving the frequency abrupt changes and overshoot problems caused by fluctuations in reference active power.

[0130] In some embodiments of the present invention, optionally, virtual inertia. The specific calculation formula for adaptive control can be as follows:

[0131] (15)

[0132] in, This represents the virtual inertia of the system during stable operation, where e is the natural constant. This represents the virtual inertia adjustment coefficient. Indicates reference active power With grid-connected active power The power difference.

[0133] Based on the above calculation formula, virtual inertia adaptive control can be carried out. By reasonably adjusting the parameters of virtual inertia, the frequency overshoot can be further reduced while reducing the frequency change rate, thus improving the frequency mutation and overshoot problems caused by the fluctuation of reference active power.

[0134] In some embodiments of the present invention, optionally, virtual inertia. satisfy:

[0135] (16)

[0136] in, Pi This indicates the maximum output power of the inverter. This represents the maximum rate of change of frequency.

[0137] Based on the above limitations, the virtual inertia for stable system operation should be set. Then, a suitable virtual inertia adjustment coefficient can be selected. This is to make full use of the inverter's output power.

[0138] In summary, this invention proposes a VSG grid-connected active power oscillation suppression strategy based on transient compensation and virtual inertia adaptation. Compared with the traditional VSG control strategy, it can more effectively suppress frequency deviation and frequency change rate, eliminate active power oscillation, and reduce active power steady-state deviation.

[0139] To verify the effectiveness of the method of this invention, a simulation model was built in the simulation tools MATLAB or Simulink. Simulation condition 1: At 1 second, due to changes in illumination, the VSG active power command (i.e., the reference active power) increases from 10 kW to 20 kW, while the grid frequency remains at 50 Hz. Simulation condition 2: At 2 seconds, the VSG active power command remains unchanged, but due to a grid fault, the grid frequency fluctuates, decreasing from 50 Hz to 49.9 Hz.

[0140] Furthermore, the simulation results are as follows:

[0141] Under simulation condition 1, the curves showing the changes in virtual inertia, output angular frequency, and active power over time are as follows: Figure 9 As shown in the figure. Using the method of this invention, under simulation condition 1, active power overshoot is eliminated, and frequency overshoot is also significantly suppressed. Furthermore, the addition of virtual inertia adaptive control suppresses the rate of frequency change, preventing short-term frequency surges from damaging electrical equipment, while further suppressing frequency overshoot. At this point, the maximum frequency overshoot is 0.13Hz, with fluctuations within 0.2Hz, meeting the standard requirements, and the system stabilization time is 0.42s.

[0142] Under simulation condition 2, the curves showing the changes in output angular frequency and active power over time are as follows: Figure 10 As shown. Through the method of the present invention (in...) Under the conditions of simulation condition 2, the grid frequency drops by 0.1Hz, the VSG increases its transmitted active power, and the active steady-state deviation decreases. At this time, the active steady-state deviation is only 1.26kW, the frequency overshoot is 0.006Hz, and the system settling time is 0.34s.

[0143] In one embodiment of the present invention, a virtual synchronous machine grid-connected control device is also proposed. For example... Figure 11 As shown, Figure 11 A structural block diagram of a virtual synchro grid-connected control device 200 according to an embodiment of the present invention is shown. Specifically, the virtual synchro grid-connected control device 200 may include the following processing unit 202:

[0144] Processing unit 202 is used to calculate the grid-connected active power of the virtual synchronous machine based on the inverter parameters and grid parameters from the previous grid-connection control process during each grid-connection control operation. and actual reactive power Inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency The frequency difference is obtained by integrating the frequency difference.

[0145] Processing unit 202 is also used to determine the actual reactive power. and reference reactive power Determine the output voltage of the inverter. ;

[0146] Processing unit 202 is also used to process grid-connected active power Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency In the first-order low-pass filter module, the virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation Perform adaptive adjustments;

[0147] Processing unit 202 is also used to determine the frequency deviation. With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. ;

[0148] The processing unit 202 is also used to perform voltage and current dual closed-loop control on the output voltage and output angular frequency to obtain a modulation wave signal, and to perform sinusoidal pulse width modulation on the modulation wave signal to obtain the switching control signal of the inverter. The switching control signal is used to drive the switching transistors in the inverter to work.

[0149] In the virtual synchronous machine grid-connected control device 200 provided by the present invention, the processing unit 202 calculates the grid-connected active power of the virtual synchronous machine based on the inverter parameters and grid parameters of the previous grid-connected control process during each grid-connected control operation. and actual reactive power The inverter parameters include the inverter's output angular frequency. Grid parameters include grid frequency. Grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angles Output angular frequency Subtract the power grid frequency After obtaining the frequency difference, it is then integrated. Further, the processing unit 202 determines the frequency difference based on the actual reactive power. and reference reactive power Determine the output voltage of the inverter. Furthermore, the processing unit 202 will connect the grid-connected active power... Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency Among them, virtual inertia Based on reference active power With grid-connected active power power difference Frequency deviation Adaptive adjustments are made. Furthermore, the processing unit 202 adjusts based on the frequency deviation. With the rated angular frequency The sum of these values ​​updates the inverter's output angular frequency. Output angular frequency With power grid frequency Synchronization, output angular frequency Used to update the grid-connected active power for the next grid-connection control. Furthermore, the processing unit 202 outputs the voltage. and the updated output angular frequency Through voltage and current dual closed-loop control and SPWM, the switching control signal of the inverter for each grid-connected control is obtained. Specifically, for the output voltage... and output angular frequency A novel active power control structure is proposed, which utilizes voltage and current dual closed-loop control to obtain a modulation wave signal. Based on this signal, sinusoidal pulse width modulation is performed to generate the inverter's switching control signal, which drives the switching transistors in the inverter. This structure eliminates active power oscillations, reduces active power steady-state deviation, and effectively suppresses frequency deviation and rate of frequency change through transient compensation and virtual inertia adaptive control.

[0150] The virtual synchronous machine grid-connected control device 200 provided by the present invention can implement the steps of the virtual synchronous machine grid-connected control method in any of the above embodiments and achieve the same technical effect, which will not be described in detail here.

[0151] In one embodiment of the present invention, another virtual synchronous machine grid-connected control device is also proposed. For example... Figure 12 As shown, Figure 12 A structural block diagram of a virtual synchro grid-connected control device 300 provided in an embodiment of the present invention is shown. The virtual synchro grid-connected control device 300 includes:

[0152] Memory 302, on which programs or instructions are stored;

[0153] The processor 304 executes the above-described program or instructions to implement the steps of the virtual synchronous machine grid-connected control method as described in any of the above embodiments.

[0154] The virtual synchronous machine grid-connected control device 300 provided in this embodiment includes a memory 302 and a processor 304. When the program or instructions in the memory 302 are executed by the processor 304, they implement the steps of the virtual synchronous machine grid-connected control method as described in any of the above embodiments. Therefore, the virtual synchronous machine grid-connected control device 300 has all the beneficial effects of the virtual synchronous machine grid-connected control method in any of the above embodiments, which will not be elaborated here.

[0155] Specifically, the memory 302 and the processor 304 can be connected via a bus or other means. The processor 304 may include one or more processing units, and the processor 304 may be a chip such as a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA).

[0156] In one embodiment of the present invention, a readable storage medium is also provided. A program or instructions are stored thereon, which, when executed by a processor, implement the steps of the virtual synchronous machine grid-connected control method as described in any of the above embodiments.

[0157] The readable storage medium provided in this embodiment of the invention stores programs or instructions that, when executed by a processor, can implement the steps of the virtual synchronous machine grid-connected control method as described in any of the above embodiments. Therefore, this readable storage medium possesses all the beneficial effects of the virtual synchronous machine grid-connected control method in any of the above embodiments, which will not be elaborated further here.

[0158] Specifically, the aforementioned readable storage media can include any medium capable of storing or transmitting information. Examples of readable storage media include electronic circuits, semiconductor memory devices, read-only memory (ROM), random access memory (RAM), compact disc read-only memory (CD-ROM), flash memory, erasable ROM (EROM), magnetic tape, floppy disk, optical disk, hard disk, fiber optic media, radio frequency (RF) links, optical data storage devices, etc. Code segments can be downloaded via computer networks such as the Internet and intranets.

[0159] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, unless otherwise expressly specified and limited. The terms "connection," "installation," and "fixing," etc., should be interpreted broadly. For example, "connection" can mean a fixed connection, a detachable connection, or an integral connection; it can mean a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0160] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0161] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0162] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A virtual synchronous machine grid-connected control method, characterized in that, include: During each grid connection control process, the grid-connected active power of the virtual synchronous machine is calculated based on the inverter parameters and grid parameters from the previous grid connection control. and actual reactive power The inverter parameters include the inverter's output angular frequency. The power grid parameters include the power grid frequency. The grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angle The output angular frequency Subtract the power grid frequency The frequency difference is obtained by integrating the frequency difference. Based on the actual reactive power and reference reactive power Determine the output voltage of the inverter. ; The grid-connected active power Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency In the first-order low-pass filter module, the virtual inertia According to the reference active power With the grid-connected active power power difference The frequency deviation Perform adaptive adjustments; According to the frequency deviation With the rated angular frequency The sum of these values ​​updates the output angular frequency of the inverter. The output angular frequency With the power grid frequency Synchronization, the output angular frequency Used to update the grid-connected active power for the next grid-connection control. ; For the output voltage and the output angular frequency Voltage and current dual closed-loop control is performed to obtain a modulation wave signal. Based on the modulation wave signal, sinusoidal pulse width modulation is performed to obtain the switching control signal of the inverter. The switching control signal is used to drive the switching transistors in the inverter to work.

2. The virtual synchronous machine grid-connected control method according to claim 1, characterized in that, The rotor motion equation corresponding to the first-order low-pass filter module is: ； in, Represents virtual inertia. Indicates the rated angular frequency. Indicates the rate of change of frequency. Indicates the reference active power. Indicates the power compensation coefficient. Let s denote the transient compensation time constant, s denote the differential operator, and m denote the frequency compensation coefficient. Indicates the active power connected to the grid. This represents the active power droop coefficient. Indicates the damping coefficient. This indicates frequency deviation.

3. The virtual synchronous machine grid-connected control method according to claim 1, characterized in that, The active closed-loop response small-signal transfer function corresponding to the first-order low-pass filter module is: ； in, Indicates the steady-state deviation of grid-connected active power. Indicates the reference active power deviation. The frequency deviation of the power grid is represented by s, the differential operator is represented by s, and a, b, and c are calculation coefficients. , , K is the synchronization voltage coefficient. , This refers to the voltage amplitude of the power grid. For output voltage, This is the equivalent reactance of the line.

4. The virtual synchronous machine grid-connected control method according to claim 1, characterized in that, Frequency deviation The calculation formula is: ； Rate of change of frequency The calculation formula is: ； Where s represents the differential operator.

5. The virtual synchronous machine grid-connected control method according to any one of claims 1 to 4, characterized in that, The virtual inertia According to the reference active power With the grid-connected active power power difference The frequency deviation Adaptive adjustments are made, including: In the power difference With the frequency deviation If the product is greater than 0, increase the virtual inertia. ; In the power difference With the frequency deviation If the product is less than or equal to 0, decrease the virtual inertia. .

6. The virtual synchronous machine grid-connected control method according to claim 5, characterized in that, The virtual inertia The calculation formula is: ； in, This represents the virtual inertia of the system during stable operation, where e is the natural constant. This represents the virtual inertia adjustment coefficient. The reference active power is indicated With the grid-connected active power The power difference.

7. The virtual synchronous machine grid-connected control method according to claim 6, characterized in that, The virtual inertia satisfy: ； in, Pi This indicates the maximum output power of the inverter. This represents the maximum rate of change of frequency.

8. A virtual synchronous machine grid-connected control device, characterized in that, include: The processing unit is used to calculate the grid-connected active power of the virtual synchronous machine based on the inverter parameters and grid parameters from the previous grid-connection control process during each grid-connection control operation. and actual reactive power The inverter parameters include the inverter's output angular frequency. The power grid parameters include the power grid frequency. The grid-connected active power Power factor angle With synchronization voltage coefficient The product of the power factor angle The output angular frequency Subtract the power grid frequency The frequency difference is obtained by integrating the frequency difference. The processing unit is further configured to determine the actual reactive power. and reference reactive power Determine the output voltage of the inverter. ; The processing unit is also used to process the grid-connected active power. Reference active power and rated angular frequency The input includes the damping coefficient. Virtual inertia Active droop coefficient Transient compensation time constant Power compensation coefficient The frequency deviation of the virtual synchronizer is calculated based on the first-order low-pass filter module with frequency compensation coefficient m. and rate of change of frequency In the first-order low-pass filter module, the virtual inertia According to the reference active power With the grid-connected active power power difference The frequency deviation Perform adaptive adjustments; The processing unit is further configured to, based on the frequency deviation With the rated angular frequency The sum of these values ​​updates the output angular frequency of the inverter. The output angular frequency With the power grid frequency Synchronization, the output angular frequency Used to update the grid-connected active power for the next grid-connection control. ; The processing unit is also used to process the output voltage. and the output angular frequency Voltage and current dual closed-loop control is performed to obtain a modulation wave signal. Based on the modulation wave signal, sinusoidal pulse width modulation is performed to obtain the switching control signal of the inverter. The switching control signal is used to drive the switching transistors in the inverter to work.

9. A virtual synchronous machine grid-connected control device, characterized in that, It includes a processor and a memory, the memory storing programs or instructions that can run on the processor, the programs or instructions being executed by the processor to implement the steps of the virtual synchronous machine grid-connected control method as described in any one of claims 1 to 7.

10. A readable storage medium, characterized in that, The readable storage medium stores a program or instructions that, when executed by a processor, implement the steps of the virtual synchronous machine grid-connected control method as described in any one of claims 1 to 7.

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