Frequency-voltage coupling modeling method and device for network construction converter equipment

Abstract

The invention relates to the technical field of power grid dynamic analysis, in particular to a frequency-voltage coupling modeling method and device for network construction converter equipment, and the method comprises the steps: obtaining network construction converter equipment data considering a current inner ring in a target power system, establishing a steady-state power and voltage equation of the network construction converter equipment based on the data of the network construction converter equipment; based on the steady-state power and voltage equation, constructing a power-frequency-voltage coupling matrix of the network construction converter equipment; on the basis of the power-frequency-voltage coupling matrix, determining a disturbance-response relationship after the network construction converter equipment is accessed to the target power system; and according to the disturbance-response relationship, obtaining a frequency-voltage coupling model used for obtaining a disturbance result after the network construction converter equipment accesses the target power system. Therefore, the problem that the analysis result does not conform to the actual situation due to the fact that the influence of the dynamic access power grid voltage on the frequency response is not considered and the influence of the current inner loop of the network construction type converter equipment is not considered in the related technology is solved.

Description

Technical Field

[0001] The present application relates to the technical field of power grid dynamic analysis, and in particular to a frequency-voltage coupling modeling method and device for a grid-connected current conversion device. Background Art

[0002] In order to achieve the goal of "carbon peak and carbon neutrality", the installed capacity of new energy power sources continues to increase, and the power grid presents the "double high" characteristics of a high proportion of new energy and a high proportion of power electronics. Among them, grid-following converters rely on phase-locked loops for grid connection, which have poor stability in weak grid conditions and limited frequency and voltage support capabilities. In order to improve the stability of weak grids, grid-building converters are increasingly being used.

[0003] Related technologies: In order to analyze the frequency, voltage support and active and reactive responses of grid-type converters, the electromechanical transients of the grid-type energy storage system can be modeled by ignoring the coupling effect, or the stability analysis can be performed through the droop control of the grid-type inverter with consistent differential passivity. For converter-dominated power systems, the transient stability of the grid-type converter can be analyzed by considering the coupled impedance matching, or by considering the transient stability of the virtual impedance effect.

[0004] However, the related technology does not consider the impact of the grid voltage dynamics on the frequency response, and the related technical analysis does not consider the impact of the current inner loop of the grid-type converter equipment, which makes the analysis results too optimistic and inconsistent with the actual situation, and urgently needs to be improved. Summary of the invention

[0005] The present application provides a frequency-voltage coupling modeling method and device for a grid-connected current converter device, so as to solve the problems in the related art that the influence of the voltage dynamics of the access grid on the frequency response is not considered, and the influence of the current inner loop of the grid-connected current converter device is not considered, thereby making the analysis results too optimistic and inconsistent with the actual situation.

[0006] The first aspect of the present application provides a frequency-voltage coupling modeling method for a grid-connected power converter, comprising the following steps: obtaining grid-connected power converter data taking into account a current inner loop in a target power system, and establishing a steady-state power equation and a steady-state voltage equation for the grid-connected power converter based on the grid-connected power converter data; constructing a power-frequency-voltage coupling matrix for the grid-connected power converter based on the steady-state power equation and the steady-state voltage equation; determining a disturbance-response relationship after the grid-connected power converter is connected to the target power system based on the power-frequency-voltage coupling matrix; and obtaining a frequency-voltage coupling model for obtaining a disturbance result after the grid-connected power converter is connected to the target power system according to the disturbance-response relationship.

[0007] Optionally, in one embodiment of the present application, the data of the grid-connecting converter device taking into account the inner loop of the current in the target power system is obtained, and the steady-state power equation and the steady-state voltage equation of the grid-connecting converter device are established based on the data of the grid-connecting converter device, including: obtaining the voltage relationship between the target power system and the grid-connecting converter device based on the target power system and the grid-connecting converter device data; obtaining the steady-state d-axis and q-axis current equations of the grid-connecting converter device based on the voltage relationship; and obtaining the steady-state power equation and the steady-state voltage equation of the grid-connecting converter device using the steady-state d-axis and q-axis current equations.

[0008] Optionally, in one embodiment of the present application, the expression of the steady-state power equation may be, but is not limited to,:

[0009]

[0010] Among them, U sys is the voltage amplitude of the grid d axis, ω0 is the rated angular frequency of the grid, s is the complex frequency, k p , k i is the proportional integral parameter of the current inner loop, R v , L v are the virtual resistance and virtual inductance of the virtual impedance link, V poi is the voltage measurement value at the point where the grid-connected converter equipment is connected to the grid, E ref is the voltage reference value generated by the virtual synchronous machine link, δ is the phase angle reference value θ of the grid-connected converter generated by the virtual synchronous machine link ref The actual phase angle θ with the power grid sys The difference, P e , Q e is the active power and reactive power output by the network equipment, Z is the system power flow and parameter matrix;

[0011] The expression of the steady-state voltage equation may be, but is not limited to,:

[0012]

[0013] Among them, V ref is the reference voltage amplitude of the network converter port, Z V is the impedance value of the virtual impedance.

[0014] Optionally, in one embodiment of the present application, the expression of the power-frequency-voltage coupling matrix may be, but is not limited to,:

[0015]

[0016] Among them, ΔP e , ΔQ eare the changes in active power and reactive power of the grid-connected converter equipment after the disturbance, Δδ is the change in the difference between the phase angle reference value of the grid-connected converter equipment and the grid phase angle after the disturbance, ΔV ref is the voltage amplitude variation of the network converter port, M is the coupling matrix, including M Pδ (s), M PV (s), M Qδ (s), M QV (s) Four active-phase angle, active-voltage, reactive-phase angle, and reactive-voltage coupling functions.

[0017] Optionally, in one embodiment of the present application, the expression of the closed-form solution of the frequency-voltage coupling model may be, but is not limited to,:

[0018]

[0019] Where Δf sys is the grid frequency change, ΔP d is the grid disturbance power, H sys , D sys are the equivalent inertia and equivalent damping of the power grid, T J , D P is the virtual inertia and damping coefficient in the virtual synchronous machine control, ξ(s) is the intermediate function, F V (s) is ΔV ref With ΔQ e The corresponding relationship function.

[0020] The second aspect of the present application provides a frequency-voltage coupling modeling device for a grid-connected power converter, comprising: an establishment module for acquiring grid-connected power converter data taking into account the current inner loop in a target power system, and establishing a steady-state power equation and a steady-state voltage equation for the grid-connected power converter based on the grid-connected power converter data; a construction module for constructing a power-frequency-voltage coupling matrix for the grid-connected power converter based on the steady-state power equation and the steady-state voltage equation; a determination module for determining a disturbance-response relationship after the grid-connected power converter is connected to the target power system based on the power-frequency-voltage coupling matrix; and a generation module for obtaining a frequency-voltage coupling model for obtaining a disturbance result after the grid-connected power converter is connected to the target power system according to the disturbance-response relationship.

[0021] Optionally, in one embodiment of the present application, the establishment module includes: a generation unit, used to obtain the voltage relationship between the target power system and the grid-connecting power conversion device based on the target power system and the grid-connecting power conversion device data; an acquisition unit, used to obtain the steady-state d-axis and q-axis current equations of the grid-connecting power conversion device based on the voltage relationship; and an establishment unit, used to use the steady-state d-axis and q-axis current equations to obtain the steady-state power equation and steady-state voltage equation of the grid-connecting power conversion device.

[0022] Optionally, in one embodiment of the present application, the expression of the steady-state power equation may be, but is not limited to,:

[0023]

[0024] Among them, U sys is the voltage amplitude of the grid d axis, ω0 is the rated angular frequency of the grid, s is the complex frequency, k p , k i is the proportional integral parameter of the current inner loop, R v , L v are the virtual resistance and virtual inductance of the virtual impedance link, V poi is the voltage measurement value at the point where the grid-connected converter equipment is connected to the grid, E ref is the voltage reference value generated by the virtual synchronous machine link, δ is the phase angle reference value θ of the grid-connected converter generated by the virtual synchronous machine link ref The actual phase angle θ with the power grid sys The difference, P e , Q e is the active power and reactive power output by the network equipment, Z is the system power flow and parameter matrix;

[0025] The expression of the steady-state voltage equation may be, but is not limited to,:

[0026]

[0027] Among them, V ref is the reference voltage amplitude of the network converter port, Z V is the impedance value of the virtual impedance.

[0028] Optionally, in one embodiment of the present application, the expression of the power-frequency-voltage coupling matrix may be, but is not limited to,:

[0029]

[0030] Among them, ΔP e , ΔQ eare the changes in active power and reactive power of the grid-connected converter equipment after the disturbance, Δδ is the change in the difference between the phase angle reference value of the grid-connected converter equipment and the grid phase angle after the disturbance, ΔV ref is the voltage amplitude variation of the network converter port, M is the coupling matrix, including M Pδ (s), M PV (s), M Qδ (s), M QV (s) Four active-phase angle, active-voltage, reactive-phase angle, and reactive-voltage coupling functions.

[0031] Optionally, in one embodiment of the present application, the expression of the closed-form solution of the frequency-voltage coupling model may be, but is not limited to,:

[0032]

[0033] Where Δf sys is the grid frequency change, ΔP d The power generated by the grid is, H sys , D sys are the equivalent inertia and equivalent damping of the power grid, T J , D P is the virtual inertia and damping coefficient in the virtual synchronous machine control, ξ(s) is the intermediate function, F V (s) is ΔV ref With ΔQ e The corresponding relationship function.

[0034] The third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the frequency-voltage coupling modeling method of the grid-connected converter device as described in the above embodiment.

[0035] The fourth aspect of the present application provides a computer-readable storage medium, which stores a computer program. When the program is executed by a processor, it implements the frequency-voltage coupling modeling method of the above-mentioned grid-connected converter device.

[0036] The fifth aspect of the present application provides a computer program product, including a computer program, which, when executed, implements the frequency-voltage coupling modeling method of the above-mentioned grid-connected converter device.

[0037] The embodiment of the present application first establishes a steady-state power equation and a steady-state voltage equation of a grid-forming converter device taking into account the inner loop of the current, and on this basis constructs a power-frequency-voltage coupling matrix of the grid-forming converter device, and obtains a frequency-voltage coupling model of the grid-forming converter device taking into account the inner loop of the current by determining the disturbance-response relationship after the grid-forming converter device is connected to the target power system and its closed-form solution, comprehensively considering the virtual synchronous machine control, virtual impedance control, inner loop control and other links of the grid-forming converter device, and being able to comprehensively and accurately describe the dynamic response and frequency and voltage support capabilities of the grid-forming converter device, more accurately describing the voltage formation and change process of the grid-forming converter device, and being easy to quickly calculate and solve the response results, and being suitable for scenarios of quickly and massively evaluating the frequency and voltage support capabilities of the grid-forming converter device. Thus, the problems in the related art that the influence of the voltage dynamics of the access grid on the frequency response is not considered, and the influence of the inner loop of the current of the grid-forming converter device is not considered, and thus the analysis results are too optimistic and do not conform to the actual situation are solved.

[0038] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0040] Figure 1 A flowchart of a frequency-voltage coupling modeling method for a grid-connected current conversion device provided according to an embodiment of the present application;

[0041] Figure 2 A block diagram of a typical grid-connected current conversion device control strategy and grid connection according to an embodiment of the present application;

[0042] Figure 3 It is a block diagram of a frequency-voltage coupling model of a grid-connected current conversion device obtained according to an embodiment of the present application;

[0043] Figure 4 A block diagram of the difference between the model results of taking the inner current loop into account and ignoring the inner current loop corresponding to different short-circuit ratios and different virtual impedances provided according to an embodiment of the present application;

[0044] Figure 5 A flowchart of the working principle of a frequency-voltage coupling modeling method for a grid-connected current conversion device provided according to an embodiment of the present application;

[0045] Figure 6 A block diagram of a frequency-voltage coupling modeling device for a grid-connected current conversion device provided according to an embodiment of the present application;

[0046] Figure 7 It is a schematic diagram of the structure of an electronic device provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0048] The following describes the frequency-voltage coupling modeling method and device of the grid-forming converter equipment of the embodiment of the present application with reference to the accompanying drawings. In view of the problem mentioned in the above background technology that the influence after access to the power grid is not considered, and the influence of the current inner loop of the grid-forming converter equipment is not considered, so that the analysis result is too optimistic and does not conform to the actual situation, the present application provides a frequency-voltage coupling modeling method of the grid-forming converter equipment, in which the steady-state power equation and steady-state voltage equation of the grid-forming converter equipment taking into account the current inner loop are first established, and on this basis, the power-frequency-voltage coupling matrix of the grid-forming converter equipment is constructed, and the disturbance-response relationship after the grid-forming converter equipment is connected to the target power system is determined. The frequency-voltage coupling model of the grid-forming converter equipment taking into account the current inner loop and its closed-form solution are obtained, and the virtual synchronous machine control, virtual impedance control, current inner loop control and other links of the grid-forming converter equipment are fully considered, and the dynamic response and frequency and voltage support capabilities of the grid-forming converter equipment can be comprehensively and accurately described, and the voltage formation and change process of the grid-forming converter equipment are more accurately described, and the response results are easy to quickly calculate and solve, which is suitable for fast and large-scale evaluation of the frequency and voltage support capabilities of the grid-forming converter equipment. This solves the problem that the related technology does not consider the impact of the grid voltage dynamics on the frequency response, nor does it consider the impact of the current inner loop of the grid-type converter equipment, which makes the analysis results too optimistic and inconsistent with the actual situation.

[0049] Specifically, Figure 1 The present invention is a flowchart of a frequency-voltage coupling modeling method for a grid-connected current conversion device provided according to an embodiment of the present application.

[0050] like Figure 1 As shown, the frequency-voltage coupling modeling method of the grid-connected current conversion device includes the following steps:

[0051] In step S101, the data of the grid-connecting converter equipment taking into account the inner current loop in the target power system is obtained, and the steady-state power equation and the steady-state voltage equation of the grid-connecting converter equipment are established based on the data of the grid-connecting converter equipment.

[0052] As a possible implementation method, the embodiment of the present application can extract the grid-connected power conversion equipment data taking into account the current inner loop from the target power system, and establish its steady-state power equation and steady-state voltage equation based on these grid-connected power conversion equipment data.

[0053] Optionally, in one embodiment of the present application, the data of the grid-connecting converter device taking into account the inner current loop in the target power system is obtained, and the steady-state power equation and the steady-state voltage equation of the grid-connecting converter device are established based on the data of the grid-connecting converter device, including: obtaining the voltage relationship between the target power system and the grid-connecting converter device based on the target power system and the grid-connecting converter device data; obtaining the steady-state d-axis and q-axis current equations of the grid-connecting converter device based on the voltage relationship; and obtaining the steady-state power equation and the steady-state voltage equation of the grid-connecting converter device using the steady-state d-axis and q-axis current equations, wherein the expression of the steady-state power equation may be, but is not limited to, as follows:

[0054]

[0055] Among them, U sys is the voltage amplitude of the grid d axis, ω0 is the rated angular frequency of the grid, s is the complex frequency, k p , k i is the proportional integral parameter of the current inner loop, R v , L v are the virtual resistance and virtual inductance of the virtual impedance link, V poi is the voltage measurement value at the point where the grid-connected converter equipment is connected to the grid, E ref is the voltage reference value generated by the virtual synchronous machine link, δ is the phase angle reference value θ of the grid-connected converter generated by the virtual synchronous machine link ref The actual phase angle θ with the power grid sys The difference, P e , Q e is the active power and reactive power output by the network equipment, Z is the system power flow and parameter matrix;

[0056] The expression of the steady-state voltage equation can be, but is not limited to:

[0057]

[0058] Among them, V ref is the reference voltage amplitude of the network converter port, Z V is the impedance value of the virtual impedance.

[0059] During the actual execution process, the embodiment of the present application can obtain the voltage relationship between the target power system and the grid-connected power conversion equipment based on the target power system and the grid-connected power conversion equipment data, and then obtain the steady-state d and q-axis current equations of the grid-connected power conversion equipment, and use the steady-state d and q-axis current equations to obtain the steady-state power equation and the steady-state voltage equation.

[0060] Specifically, the embodiments of the present application Figure 2 A typical control strategy for grid-connected current converter equipment and a schematic diagram for grid connection are shown. Taking this as an example, the embodiment of the present application establishes steady-state power and voltage equations for the grid-connected current converter equipment taking into account the inner current loop.

[0061] First, the embodiment of the present application takes the grid voltage as the phase reference, and the grid d-axis voltage is the voltage amplitude U sys , the q-axis voltage is 0. According to the system power flow relationship, the reference voltage v odref 、v oqref The relationship with the grid voltage can be expressed as, but not limited to:

[0062]

[0063] Where ω0 is the rated angular frequency of the grid, s is the complex frequency, R and L are the total resistance and total inductance from the port of the grid-forming converter to the grid, respectively. d 、i q They are the d-axis and q-axis currents of the grid-connected converter equipment respectively.

[0064] In addition, according to the current inner loop control strategy of the grid-connected current conversion device, v odref 、v oqref The relationship can be expressed as but not limited to:

[0065]

[0066] Among them, k p , k i is the proportional integral parameter of the current inner loop, i dref 、i qref is the d and q axis current reference value of the grid conversion equipment, generated by the virtual impedance link, L f is the filter inductance value. In particular, the current inner loop of the grid-connected converter also needs to input the d and q axis voltage measurement values ​​of the grid access point, that is, v poid 、v poiq .

[0067] Furthermore, the embodiment of the present application can obtain i according to the virtual impedance link control strategy. dref 、i qref The relationship can be expressed as, but not limited to:

[0068]

[0069] Among them, R v , L v are the virtual resistance and virtual inductance of the virtual impedance link, V poi is the voltage measurement value at the point where the grid-connected converter equipment is connected to the grid, Eref is the voltage reference value generated by the virtual synchronous machine link, δ is the phase angle reference value θ of the grid-connected converter generated by the virtual synchronous machine link ref The actual phase angle θ with the power grid sys difference.

[0070] Furthermore, the embodiment of the present application can obtain E according to the virtual synchronous machine link control strategy. ref , δ, θ ref The relationship can be expressed as, but not limited to:

[0071]

[0072] Among them, T J , D P is the virtual inertia and damping coefficient in the virtual synchronous machine control, P0 and Q0 are the initial reference values ​​of active power and reactive power, P e , Q e K is the active power and reactive power output by the network equipment. pQ , K iQ is the PI parameter of the voltage formation link in the virtual synchronous machine control, D U is the voltage droop coefficient, and V0 is the voltage rating of the access point of the networking equipment.

[0073] Furthermore, the embodiment of the present application can obtain the steady-state d-axis and q-axis current values ​​of the grid-connected current conversion device by combining equations (1)-(4), which can be expressed as but not limited to:

[0074]

[0075] Where Z is the system power flow and parameter matrix, which is determined by the system and can be expressed as but not limited to:

[0076]

[0077] Furthermore, the embodiment of the present application can obtain the steady-state power equation of the grid-connected converter device according to the steady-state d-axis and q-axis current equations of formula (6), which can be but is not limited to being expressed as shown in the following formula (7), which includes the voltage and phase angle reference values ​​generated by the virtual impedance and virtual synchronous machine control, and also includes the voltage measurement value of the access grid point.

[0078]

[0079] Furthermore, in the embodiment of the present application, Z and U can be converted into steady-state d-axis and q-axis current equations according to equation (6). sys The term is moved to the left side of the equation, and the d-axis and q-axis equations are converted into amplitude equations. Then, the steady-state voltage equation of the grid-connected converter can be obtained, which can be expressed as, but not limited to:

[0080]

[0081] In step S102, based on the steady-state power equation and the steady-state voltage equation, a power-frequency-voltage coupling matrix of the grid-connected converter is constructed. The expression of the power-frequency-voltage coupling matrix can be, but is not limited to,:

[0082]

[0083] Among them, ΔP e , ΔQ e are the changes in active power and reactive power of the grid-connected converter equipment after the disturbance, Δδ is the change in the difference between the phase angle reference value of the grid-connected converter equipment and the grid phase angle after the disturbance, ΔV ref is the voltage amplitude variation of the network converter port, M is the coupling matrix, including M Pδ (s), M PV (s), M Qδ (s), M QV (s) Four active-phase angle, active-voltage, reactive-phase angle, and reactive-voltage coupling functions.

[0084] As a possible implementation method, the embodiment of the present application can use small disturbance analysis based on the steady-state power equation and the steady-state voltage equation to construct a power-frequency-voltage coupling matrix of the grid-connected converter device.

[0085] Specifically, the embodiment of the present application uses the steady-state power equation obtained by formula (7) and uses small perturbation analysis to respectively calculate the phase angle δ and the voltage reference value V in formula (7): ref By taking partial derivatives, we can obtain the dynamic power-frequency-voltage coupling matrix of the grid-forming converter equipment after the grid disturbance occurs. The expression of the power-frequency-voltage coupling matrix can be, but is not limited to, as follows:

[0086]

[0087] Among them, ΔP e , ΔQ e are the changes in active power and reactive power of the grid-connected converter equipment after the disturbance, Δδ is the change in the difference between the phase angle reference value of the grid-connected converter equipment and the grid phase angle after the disturbance, ΔV ref is the voltage amplitude variation of the network converter port, M is the coupling matrix, including M Pδ (s), M PV (s), M Qδ (s), M QV (s) Four active-phase angle, active-voltage, reactive-phase angle, and reactive-voltage coupling functions.

[0088] Further, in the embodiment of the present application, the expression of the M matrix can be, but is not limited to, expressed as:

[0089]

[0090] In addition, in order to simplify the representation, the embodiment of the present application defines the inner loop PI parameter expression as I(s), then I(s) and M Pδ (s), M PV (s), M Qδ (s), M QV The expression of (s) is shown in formula (11), which can be expressed as but not limited to:

[0091]

[0092] Among them, U sys0 is the grid voltage amplitude immediately before the disturbance occurs, E0, V poi0 They are the voltage reference value generated by the virtual synchronous machine link and the voltage amplitude at the access point of the networking equipment just before the disturbance occurs, and δ0 is the difference between the phase angle reference value of the networking converter equipment and the grid phase angle just before the disturbance occurs.

[0093] In step S103, based on the power-frequency-voltage coupling matrix, a disturbance-response relationship after the grid-connected converter device is connected to the target power system is determined.

[0094] It will be understood by those skilled in the art that, based on the power-frequency-voltage coupling matrix in the above-mentioned steps, in order to analyze the frequency and voltage support capability of the grid-connected power conversion equipment to the power grid and solve the frequency and voltage changes, it is necessary to determine the disturbance-response relationship after the grid-connected power conversion equipment is connected to the target power system.

[0095] Specifically, first, the relationship between the power and frequency of the target power system in the embodiment of the present application is as shown in formula (12), which can be expressed as but not limited to:

[0096] (2H sys s+D sys )Δf sys =ΔP d +Δ P e, (12)

[0097] Among them, H sys , D sys are the equivalent inertia and equivalent damping of the power grid, Δf sys is the frequency change of the power grid after the disturbance, ΔP d is the disturbance power, which is used to describe the system power imbalance.

[0098] In the embodiment of the present application, the power response ΔP of the grid-connected converter device in formula (12) ise According to the power-frequency-voltage coupling matrix (9), ΔP e The satisfied relationship can be expressed as, but not limited to:

[0099] ΔP e =M Pδ (s)Δδ+M PV (s)ΔV ref , (13)

[0100] In formula (12) of the embodiment of the present application, for Δδ, according to the virtual synchronous machine control of the grid-connected converter equipment and the definition of Δδ, the relationship satisfied can be, but is not limited to, expressed as:

[0101]

[0102] In addition, for the ΔV in formula (12), ref According to the steady-state voltage equation of the grid-connected converter, the relationship it satisfies after the disturbance can be expressed as, but not limited to:

[0103]

[0104] Among them, ΔE ref , ΔV po i are the changes in the voltage reference value generated by the virtual synchronous machine link after the disturbance and the changes in the voltage amplitude at the access point of the networking equipment.

[0105] In addition, according to the virtual synchronous machine control of the network conversion equipment and the reactive power-voltage change relationship of the access point, ΔE ref , ΔV poi It can be further expressed as:

[0106]

[0107] Among them, SCR is the short-circuit ratio of the grid connection point, is the line impedance angle.

[0108] Therefore, the embodiment of the present application ΔE ref , ΔV poi , ΔV ref can be expressed as ΔQ e The present embodiment defines F V (s) is ΔV ref With ΔQ e The corresponding relationship function is: according to the power-frequency-voltage coupling matrix and the relationship between equations (15) and (16), ΔV ref 、F V (s), ΔQ e The expression of can be, but is not limited to, expressed as:

[0109]

[0110] In step S104, a frequency-voltage coupling model for obtaining the disturbance result after the grid-connected converter is connected to the target power system is obtained according to the disturbance-response relationship. The closed-form solution of the frequency-voltage coupling model may be, but is not limited to,:

[0111]

[0112] Where Δf sys is the grid frequency change, ΔP d is the grid disturbance power, H sys , D sys are the equivalent inertia and equivalent damping of the power grid, T J , D P is the virtual inertia and damping coefficient in the virtual synchronous machine control, ξ(s) is the intermediate function, F V (s) is ΔV ref With ΔQ e The corresponding relationship function.

[0113] In some embodiments, the embodiment of the present application determines the disturbance-response relationship of the grid-forming converter device connected to the target power system according to equations (12)-(17), and then obtains a frequency-voltage coupling model of the grid-forming converter device considering the current inner loop, such as Figure 3 In the embodiment of the present application, the model includes the active and reactive responses of the grid-forming converter equipment after the disturbance and the frequency and voltage changes of the grid.

[0114] Specifically, the embodiments of the present application can Figure 3 Further simplifying and combining equations (13)-(17), we can obtain the active power change ΔP of the grid-connected converter equipment: e With the grid frequency change Δf sys The only corresponding analytical expression, reactive power change ΔQ e The port voltage changes with ΔV poi The only corresponding analytical expression can be expressed as but not limited to:

[0115]

[0116] Based on this, the embodiment of the present application combines equations (12)-(18) to finally obtain the power generated by the power grid as ΔP d The closed-form solution of the frequency-voltage coupling model of the grid-connected converter after the disturbance includes the disturbance-response analytical expressions of frequency and voltage, which can be expressed as but not limited to:

[0117]

[0118] Among them, ξ(s) is the intermediate function.

[0119] In summary, the embodiment of the present application obtains the frequency-voltage coupling model of the grid-connected converter and its closed-form solution. For any disturbance power, it can be calculated according to Figure 3 The closed-form solutions of equations (18) and (19) establish the frequency-voltage coupling model of the grid-connected converter equipment taking into account the current inner loop. The closed-form solution includes the frequency and voltage changes after the disturbance and the corresponding active power and reactive power support expressions of the grid-connected converter equipment.

[0120] For example, it can be seen from formula (15) in the embodiment of the present application that if the current inner loop is ignored, the port voltage of the network conversion device is completely determined by the virtual synchronous control link, and the model taking into account the current inner loop and ignoring the current inner loop satisfies the formula shown in formula (20), which can be expressed as but not limited to:

[0121]

[0122] It can be seen from formula (20) that in the embodiment of the present application, when D U = 0, ignoring the ΔV obtained by the current inner loop model ref It has nothing to do with the voltage change at the grid connection point, that is, it has nothing to do with the short-circuit ratio SCR parameter at the grid connection point. In this case, the embodiment of the present application can compare the model results of taking into account the current inner loop and ignoring the current inner loop corresponding to different short-circuit ratios and different virtual impedances. The effect diagram is as follows Figure 4 shown. Figure 4 (a) to Figure 4 (d) shows the virtual impedance Z V When the disturbance is 0.2, 0.4, 0.6, and 0.8 pu, the frequency response results of the current inner loop model are ignored and taken into account. Figure 4 (a) is Z provided according to one embodiment of the present application V Schematic diagram of the difference between the model results of taking into account the inner current loop and ignoring the inner current loop at 0.2; Figure 4 (b) is Z provided according to one embodiment of the present application V The block diagram of the difference between the model results of taking into account the inner current loop and ignoring the inner current loop is 0.4; Figure 4 (c) is Z provided according to one embodiment of the present application V Schematic diagram of the difference between the model results of taking into account the inner current loop and ignoring the inner current loop at 0.6; Figure 4 (d) is Z provided according to one embodiment of the present application V Schematic diagram of the difference between the results of the model with and without taking into account the inner current loop of 0.8.

[0123] The present application embodiment is Figure 4It can be seen that when the short circuit ratio is high or the virtual impedance is small, the difference between ignoring and taking into account the inner loop model is not much; on the contrary, when the virtual impedance is large and the short circuit ratio is low, there is a difference between ignoring and taking into account the inner loop model, and it increases with the decrease of the short circuit ratio and the increase of the virtual impedance. And the result of ignoring the inner loop model may be too optimistic when the virtual impedance is large and the short circuit ratio is low.

[0124] Furthermore, the values ​​of various parameters of the frequency-voltage coupling model of the embodiment of the present application are shown in Table 1, wherein Table 1 is a schematic table of frequency-voltage coupling model parameters and values ​​provided according to an embodiment of the present application, and the unit is pu.

[0125] Table 1

[0126] parameter <![CDATA[H sys ]]> <![CDATA[D sys ]]> <![CDATA[T J ]]> <![CDATA[D p ]]> <![CDATA[k p ]]> <![CDATA[k i ]]> <![CDATA[K pQ ]]> <![CDATA[K iq ]]> R L <![CDATA[ω0]]> Numeric 1 1 1 30 1.5 0.5 0.1 0.01 0.05 0.002 314

[0127] Furthermore, the embodiment of the present application is Figure 4 As can be seen from Table 1, the influence of short-circuit ratio and virtual impedance on the frequency-voltage coupling model of grid-connected converter equipment verifies the difference between the two models taking into account the inner current loop and ignoring the inner current loop, reflecting the necessity of modeling and analysis taking into account the inner current loop and the innovativeness of the proposed frequency-voltage coupling modeling method for grid-connected converter equipment.

[0128] The working principle of the frequency-voltage coupling modeling method for the grid-connected converter device proposed in the embodiment of the present application is described in detail below in conjunction with a specific embodiment.

[0129] in, Figure 5 The present invention is a flowchart of the working principle of a frequency-voltage coupling modeling method for a grid-connected current conversion device provided according to an embodiment of the present application.

[0130] Step S501: Establish steady-state power and voltage equations of the grid-connected current conversion equipment taking into account the inner current loop.

[0131] That is to say, the embodiment of the present application can establish a steady-state power equation as shown in equation (7) and a steady-state voltage equation as shown in equation (8).

[0132] Step S502: constructing a power-frequency-voltage coupling matrix of the grid-connected converter equipment using small disturbance analysis.

[0133] That is to say, the embodiment of the present application can construct a power-frequency-voltage coupling matrix as shown in formula (9).

[0134] Step S503: Determine the disturbance-response relationship of the grid-connected converter device connected to the target power system.

[0135] That is to say, the embodiments of the present application can obtain the disturbance-response relationship shown in equations (12) to (17).

[0136] Step S504: obtaining a frequency-voltage coupling model of a grid-connected current converter device taking into account the inner current loop and its closed-form solution.

[0137] That is to say, the embodiment of the present application can obtain the frequency-voltage coupling model of the grid-connected current conversion equipment taking into account the current inner loop as shown in formula (19) and its closed-form solution.

[0138] According to the frequency-voltage coupling modeling method of the grid-forming converter equipment proposed in the embodiment of the present application, the steady-state power equation and steady-state voltage equation of the grid-forming converter equipment taking into account the inner loop of the current are first established, and on this basis, the power-frequency-voltage coupling matrix of the grid-forming converter equipment is constructed. By determining the disturbance-response relationship after the grid-forming converter equipment is connected to the target power system, the frequency-voltage coupling model of the grid-forming converter equipment taking into account the inner loop of the current and its closed-form solution are obtained, which can comprehensively and accurately describe the dynamic response and frequency and voltage support capabilities of the grid-forming converter equipment, more accurately describe the voltage formation and change process of the grid-forming converter equipment, and is easy to quickly calculate and solve the response results. It is suitable for scenarios where the frequency and voltage support capabilities of the grid-forming converter equipment are quickly and massively evaluated. Therefore, the problems in the related art that the influence of the voltage dynamics of the access grid on the frequency response and the influence of the inner loop of the current of the grid-forming converter equipment are not considered, and the analysis results are too optimistic and do not conform to the actual situation are solved.

[0139] Next, a frequency-voltage coupling modeling device for a grid-connected current converter device according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0140] Figure 6 A block diagram of a frequency-voltage coupling modeling device for a grid-connected current conversion device provided according to an embodiment of the present application.

[0141] like Figure 6 As shown, the frequency-voltage coupling modeling device 10 of the grid-connected current conversion device includes: an establishing module 100, a constructing module 200, a determining module 300 and a generating module 400.

[0142] The establishment module 100 is used to obtain the grid-connecting converter equipment data taking into account the current inner loop in the target power system, and to establish the steady-state power equation and steady-state voltage equation of the grid-connecting converter equipment based on the grid-connecting converter equipment data.

[0143] The construction module 200 is used to construct a power-frequency-voltage coupling matrix of the grid-connected converter device based on the steady-state power equation and the steady-state voltage equation.

[0144] The determination module 300 is used to determine the disturbance-response relationship after the grid-forming converter device is connected to the target power system based on the power-frequency-voltage coupling matrix.

[0145] The generation module 400 is used to obtain a frequency-voltage coupling model for obtaining a disturbance result after the grid-connected converter device is connected to the target power system according to the disturbance-response relationship.

[0146] Optionally, in one embodiment of the present application, the establishment module 100 includes: a generation unit, an acquisition unit and an establishment unit.

[0147] The generating unit is used to obtain the voltage relationship between the target power system and the grid-forming converter device based on the target power system and the grid-forming converter device data.

[0148] The acquisition unit is used to acquire the steady-state d-axis and q-axis current equations of the grid-forming converter device based on the voltage relationship.

[0149] A unit is established for obtaining a steady-state power equation and a steady-state voltage equation of a grid-forming converter device using steady-state d-axis and q-axis current equations.

[0150] Optionally, in one embodiment of the present application, the expression of the steady-state power equation may be, but is not limited to:

[0151]

[0152] Among them, U sys is the voltage amplitude of the grid d axis, ω0 is the rated angular frequency of the grid, s is the complex frequency, k p , k i is the proportional integral parameter of the current inner loop, R v , L v are the virtual resistance and virtual inductance of the virtual impedance link, V poi is the voltage measurement value at the point where the grid-connected converter equipment is connected to the grid, E ref is the voltage reference value generated by the virtual synchronous machine link, δ is the phase angle reference value θ of the grid-connected converter generated by the virtual synchronous machine link ref The actual phase angle θ with the power grid sys The difference, P e , Q e is the active power and reactive power output by the network equipment, Z is the system power flow and parameter matrix;

[0153] The expression of the steady-state voltage equation can be, but is not limited to:

[0154]

[0155] Among them, V ref is the reference voltage amplitude of the network converter port, Z V is the impedance value of the virtual impedance.

[0156] Optionally, in one embodiment of the present application, the expression of the power-frequency-voltage coupling matrix may be, but is not limited to,:

[0157]

[0158] Among them, ΔP e , ΔQ e are the changes in active power and reactive power of the grid-connected converter equipment after the disturbance, Δδ is the change in the difference between the phase angle reference value of the grid-connected converter equipment and the grid phase angle after the disturbance, ΔV ref is the voltage amplitude variation of the network converter port, M is the coupling matrix, including M Pδ (s), M PV (s), M Qδ (s), M QV (s) Four active-phase angle, active-voltage, reactive-phase angle, and reactive-voltage coupling functions.

[0159] Optionally, in one embodiment of the present application, the expression of the closed-form solution of the frequency-voltage coupling model may be, but is not limited to,:

[0160]

[0161] Where Δf sys is the grid frequency change, ΔP d is the grid disturbance power, H sys , D sys are the equivalent inertia and equivalent damping of the power grid, T J , D P is the virtual inertia and damping coefficient in the virtual synchronous machine control, ξ(s) is the intermediate function, F V (s) is ΔV ref With ΔQ e The corresponding relationship function.

[0162] It should be noted that the above explanation of the embodiment of the frequency-voltage coupling modeling method of the grid-connecting converter device is also applicable to the frequency-voltage coupling modeling device of the grid-connecting converter device of this embodiment, and will not be repeated here.

[0163] According to the frequency-voltage coupling modeling device of the grid-forming converter equipment proposed in the embodiment of the present application, the steady-state power equation and steady-state voltage equation of the grid-forming converter equipment taking into account the inner loop of the current are first established, and on this basis, the power-frequency-voltage coupling matrix of the grid-forming converter equipment is constructed. By determining the disturbance-response relationship after the grid-forming converter equipment is connected to the target power system, the frequency-voltage coupling model of the grid-forming converter equipment taking into account the inner loop of the current and its closed-form solution are obtained, which can comprehensively and accurately describe the dynamic response and frequency and voltage support capabilities of the grid-forming converter equipment, more accurately describe the voltage formation and change process of the grid-forming converter equipment, and is easy to quickly calculate and solve the response results. It is suitable for scenarios where the frequency and voltage support capabilities of the grid-forming converter equipment are quickly and massively evaluated. Therefore, the problems in the related art that the influence of the voltage dynamics of the access grid on the frequency response and the influence of the inner loop of the current of the grid-forming converter equipment are not considered, and the analysis results are too optimistic and do not conform to the actual situation are solved.

[0164] Figure 7 This is a schematic diagram of the structure of an electronic device provided according to an embodiment of the present application. The electronic device may include:

[0165] A memory 701 , a processor 702 , and a computer program stored in the memory 701 and executable on the processor 702 .

[0166] When the processor 702 executes the program, the frequency-voltage coupling modeling method of the grid-connected converter device provided in the above embodiment is implemented.

[0167] Furthermore, the electronic device further comprises:

[0168] The communication interface 703 is used for communication between the memory 701 and the processor 702 .

[0169] The memory 701 is used to store computer programs that can be executed on the processor 702 .

[0170] The memory 701 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0171] If the memory 701, the processor 702 and the communication interface 703 are implemented independently, the communication interface 703, the memory 701 and the processor 702 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 7 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0172] Optionally, in a specific implementation, if the memory 701, the processor 702 and the communication interface 703 are integrated on a chip, the memory 701, the processor 702 and the communication interface 703 can communicate with each other through an internal interface.

[0173] The processor 702 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0174] An embodiment of the present application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the frequency-voltage coupling modeling method of the grid-connected converter device as described above.

[0175] An embodiment of the present application also provides a computer program product, including a computer program, which, when executed, implements the frequency-voltage coupling modeling method of the grid-connected current conversion device as described above.

[0176] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0177] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0178] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0179] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or N wirings (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways as necessary and then storing it in a computer memory.

[0180] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented by hardware, as in another embodiment, it can be implemented by any one or a combination of multiple of the following technologies known in the art: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0181] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0182] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0183] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A frequency-voltage coupling modeling method for a grid-connected current conversion device, characterized in that: The following steps are involved: Acquire data of a grid-forming converter device taking into account a current inner loop in a target power system, and establish a steady-state power equation and a steady-state voltage equation of the grid-forming converter device based on the data of the grid-forming converter device; Based on the steady-state power equation and the steady-state voltage equation, construct a power-frequency-voltage coupling matrix of the grid-forming converter device; Based on the power-frequency-voltage coupling matrix, determining a disturbance-response relationship after the grid-forming converter device is connected to the target power system; A frequency-voltage coupling model for obtaining a disturbance result after the grid-connected converter device is connected to the target power system is obtained according to the disturbance-response relationship.

2. The method according to claim 1, characterized in that: The step of obtaining the grid-forming converter equipment data taking into account the inner current loop in the target power system, and establishing the steady-state power equation and the steady-state voltage equation of the grid-forming converter equipment based on the grid-forming converter equipment data, includes: Based on the target power system and the grid-forming converter data, a voltage relationship between the target power system and the grid-forming converter is obtained; Based on the voltage relationship, obtaining steady-state d-axis and q-axis current equations of the grid-forming converter device; The steady-state d-axis and q-axis current equations are used to obtain the steady-state power equation and the steady-state voltage equation of the grid-forming converter.

3. The method according to claim 2, characterized in that in, The expression of the steady-state power equation is: Among them, U sys is the voltage amplitude of the grid d axis, ω0 is the rated angular frequency of the grid, s is the complex frequency, k p , k i is the proportional integral parameter of the current inner loop, R v , L v are the virtual resistance and virtual inductance of the virtual impedance link, V poi is the voltage measurement value at the point where the grid-connected converter equipment is connected to the grid, E ref is the voltage reference value generated by the virtual synchronous machine link, δ is the phase angle reference value θ of the grid-connected converter generated by the virtual synchronous machine link ref The actual phase angle θ with the power grid sys The difference, P e , Q e is the active power and reactive power output by the network equipment, Z is the system power flow and parameter matrix; The expression of the steady-state voltage equation is: Among them, V ref is the reference voltage amplitude of the network converter port, Z V is the impedance value of the virtual impedance.

4. The method according to claim 1, characterized in that The expression of the power-frequency-voltage coupling matrix is: Among them, ΔP e , ΔQ e are the changes in active power and reactive power of the grid-connected converter equipment after the disturbance, Δδ is the change in the difference between the phase angle reference value of the grid-connected converter equipment and the grid phase angle after the disturbance, ΔV ref is the voltage amplitude variation of the network converter port, M is the coupling matrix, including M Pδ (S), M PV (S), M Qδ (s), M QV (s) Four active-phase angle, active-voltage, reactive-phase angle, and reactive-voltage coupling functions.

5. The method according to claim 1, characterized in that The closed-form solution of the frequency-voltage coupling model is expressed as: Where Δf sys is the grid frequency change, ΔP d is the grid disturbance power, H sys , D sys are the equivalent inertia and equivalent damping of the power grid, T J , D P is the virtual inertia and damping coefficient in the virtual synchronous machine control, ξ(s) is the intermediate function, F V (s) is ΔV ref With ΔQ e The corresponding relationship function.

6. A frequency-voltage coupling modeling device for a grid-connected current conversion device, characterized in that: include: Establishing a module for acquiring data of a grid-forming converter device taking into account a current inner loop in a target power system, and establishing a steady-state power equation and a steady-state voltage equation of the grid-forming converter device based on the data of the grid-forming converter device; A construction module, used to construct a power-frequency-voltage coupling matrix of the grid-forming converter device based on the steady-state power equation and the steady-state voltage equation; A determination module, used to determine the disturbance-response relationship after the grid-forming converter device is connected to the target power system based on the power-frequency-voltage coupling matrix; A generation module is used to obtain a frequency-voltage coupling model for obtaining a disturbance result after the grid-forming converter device is connected to the target power system according to the disturbance-response relationship.

7. The device according to claim 6, characterized in that The establishment module comprises: A generating unit, configured to obtain a voltage relationship between the target power system and the grid-forming converter device based on the target power system and the grid-forming converter device data; An acquisition unit, used for acquiring steady-state d-axis and q-axis current equations of the grid-forming converter device based on the voltage relationship; A unit is established, which is used to obtain the steady-state power equation and the steady-state voltage equation of the grid-forming converter device by using the steady-state d-axis and q-axis current equations.

8. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the frequency-voltage coupling modeling method for a grid-connected current conversion device as described in any one of claims 1 to 5.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the frequency-voltage coupling modeling method of a grid-connected current conversion device as described in any one of claims 1 to 5.

10. A computer program product, characterized in that It comprises a computer program, which, when executed, is used to implement the frequency-voltage coupling modeling method of the grid-connected current conversion device as described in any one of claims 1 to 5.

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