Parameter design optimization method and device under transient working condition of network construction type converter

Abstract

The invention provides a parameter design optimization method and device under a transient condition of a network-constructing converter. The method comprises the following steps: constructing a traditional network-constructing converter model; obtaining a general expression for connecting the virtual synchronous machine control converter and the droop control converter based on the traditional network construction type converter model; building a unified network construction type converter model suitable for a transient state working condition; obtaining a virtual synchronous machine unified expression in different power loop forms based on the unified network construction type converter model; based on the general expression and the virtual synchronous machine unified expression, obtaining a network construction type unified standard expression suitable for the transient state working condition; and optimizing the parameter design under the transient working condition of the network construction type converter based on the unified standard expression of the network construction type. According to the method, the transient characteristics of the network construction type converter under different control strategies can be analyzed more accurately by establishing the unified network construction type converter model and obtaining the corresponding unified standard expression, so that the parameter design and the stability under the transient working condition are optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-type converters, and in particular to a parameter design optimization method and device for a grid-type converter under transient conditions. Background Art

[0002] With the continuous increase in the penetration rate of high-proportion new energy and its supporting converters, the access of new energy converters to the power system has caused certain harm to the safe and stable operation of the power grid. Specifically, the power grid presents a situation of low inertia and under-damped operating characteristics, which has caused new challenges such as broadband oscillation, small disturbance and large disturbance instability. At present, converter control is mainly divided into grid-following converters and grid-building converters. Among them, the converter with grid-building control structure simulates the external characteristics of the synchronous machine, provides "strong" damping and "high" inertia for the system, and can act as a "voltage source" to actively support the power grid. It is an excellent control that adapts to the current power system structure. However, there are certain differences in the control structures of grid-building converters produced by various manufacturers. Different types of grid-building converters exist in a power system. Due to the differences in control structures, the theoretical analysis results and actual working conditions will be different. Especially when analyzing transient stability problems, there is a high possibility of misjudgment of transient stability due to differences in control structures, which will lead to serious safety problems, which is unacceptable to the power system. Secondly, with the development of power systems, fault ride-through of converters has also become an important link that should be considered in control loop design.

[0003] There are many literatures on transient stability analysis and fault ride-through control methods of grid-type converters. Different analyses and methods improve the stability, power support and fault current limiting in the transient process by modifying control parameters and command variables. However, it is found that there are differences in the power loop in the control link of relevant literature. Therefore, the transient stability conclusions obtained are only applicable to the control structures in the literature due to the differences in control structures, and are not universal. In addition, there is no existing technology that compares the transient stability of virtual synchronous generators (VSG) with different control loop types.

[0004] Therefore, there is an urgent need for an analysis method that can jointly control grid-type converters under different power loops and reveal the inherent mechanism of the differences in the power loops of grid-type converters, so as to provide a practical basis for parameter design and fault ride-through control methods of grid-type converters under transient conditions. Summary of the invention

[0005] In view of this, the present invention provides a parameter design optimization method and device for a grid-connected converter under transient conditions to solve at least one of the above-mentioned problems.

[0006] To achieve the above object, the present invention adopts the following solutions:

[0007] According to the first aspect of the present invention, there is provided a method for optimizing the parameter design of a grid-forming converter under transient conditions. The method includes: building a traditional grid-forming converter model, the traditional grid-forming converter model including: an active frequency control loop, a reactive voltage control loop, a coordinate transformation system, a power calculation system, and a PWM modulation unit, the power calculation system being respectively connected to the active frequency control loop and the reactive voltage control loop, and the coordinate transformation system being respectively connected to the active frequency control loop, the reactive voltage control loop, and the PWM modulation unit; obtaining a general expression for connecting a virtual synchronous machine control type converter and a droop control type converter based on the traditional grid-forming converter model; building a unified grid-forming converter model suitable for transient conditions, the unified grid-forming converter model including: an active control loop unit, a reactive control loop unit, a voltage and current inner loop unit, and a PWM modulator, the voltage and current inner loop unit being respectively connected to the active control loop unit, the reactive control loop unit, and the voltage and current inner loop unit; obtaining a unified expression of the virtual synchronous machine in different power loop forms based on the unified grid-forming converter model; obtaining a unified grid-forming standard expression of the unified grid-forming converter model suitable for transient conditions based on the general expression and the unified expression of the virtual synchronous machine; and optimizing the parameter design of the grid-forming converter under transient conditions based on the unified grid-forming standard expression.

[0008] As an embodiment of the present invention, obtaining a general expression for connecting a virtual synchronous machine control type converter and a droop control type converter based on the traditional grid-forming converter model in the above method includes: respectively obtaining the mathematical expressions of the active loop and the reactive loop in traditional droop control, LPF type droop control, and virtual synchronous machine control in the traditional grid-forming converter model; and obtaining a general expression for connecting the virtual synchronous machine control type converter and the droop control type converter based on the mathematical expressions of the active loop and the reactive loop. The general expression is as follows:

[0009]

[0010] In the above formula, ω and V are respectively the output angular velocity and the grid connection point voltage, ω 0 and V 0 are respectively the angular velocity and the grid connection point voltage commands, P and Q are respectively the electromagnetic active power and the electromagnetic reactive power, P 0 and Q 0 are respectively the active power and the reactive power commands, s is the Laplace operator, and A, B, C, and D are respectively undetermined parameters.

[0011] As an embodiment of the present invention, the method of obtaining a unified expression of a virtual synchronous machine under different power ring forms based on the unified grid-type converter model includes: analyzing the differences and similarities of the active ring control of the virtual synchronous machine under different power ring forms in the unified grid-type converter model; establishing a unified active ring expression based on the differences and similarities analysis results of the active ring control, and the active ring expression is as follows:

[0012]

[0013] In the above formula, P ref is the active power command value, P e is the electromagnetic active power, D eq is the generalized damping, J eq is the generalized inertia;

[0014] The differences and similarities of the reactive loop control of the virtual synchronous machine under different power loop forms in the unified grid-type converter model are analyzed; based on the differences and similarities analysis results of the reactive loop control, a unified reactive loop expression is established, and the reactive loop expression is as follows:

[0015]

[0016] In the above formula, E is the output voltage, U is 0 is the output voltage command value, k ep is the generalized scale parameter, k ei is the generalized integral parameter, k ev is the generalized voltage correction parameter, Q ref is the reactive power command, Q e is the electromagnetic reactive power;

[0017] The active loop expression and the reactive loop expression are combined to obtain a unified expression of the virtual synchronous machine.

[0018] As an embodiment of the present invention, the unified standard expression of the unified grid-type converter model applicable to transient conditions in the above method is:

[0019]

[0020] As an embodiment of the present invention, in the above method, the parameter design of the network-forming converter under transient conditions based on the network-forming unified standard expression includes: analyzing the influence of the scaling of the generalized damping and generalized inertia on the frequency stability and power angle stability under transient conditions based on the network-forming unified standard expression, and obtaining the first parameter-stability correspondence table; analyzing the influence of the presence or absence of the generalized proportional parameter, generalized integral parameter, and generalized voltage correction parameter on the transient voltage stability under transient conditions based on the network-forming unified standard expression, and obtaining the second parameter-stability correspondence table; adjusting the values of the generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter, and generalized voltage correction parameter of the network-forming converter under transient conditions according to the first parameter-stability correspondence table and the second parameter-stability correspondence table to meet the design requirements.

[0021] As an embodiment of the present invention, in the above method, adjusting the values of the generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter, and generalized voltage correction parameter of the network-forming converter under transient conditions according to the first parameter-stability correspondence table and the second parameter-stability correspondence table to meet the design requirements includes: extracting the control code of the network-forming converter, analyzing the active loop and reactive loop expressions corresponding to the control code, and then extracting the parameters in the control code, where the parameters include damping, inertia, reactive loop ratio, integral, and voltage correction coefficient; comparing the extracted parameters with the network-forming unified standard expression, and equivalently converting them into generalized damping, generalized inertia, generalized proportion, generalized integral, and generalized voltage correction parameters; analyzing the transient stability of the equivalent parameters individually, and adjusting the equivalent parameters according to the first parameter-stability correspondence table and the second parameter-stability correspondence table; reversely equivalent the adjusted equivalent parameters into the form in the control code through the network-forming unified standard expression to improve the optimization of the working condition parameters of the control code to adapt to transient faults.

[0022] According to a second aspect of the present invention, there is provided a parameter design optimization device for a network-forming converter under transient conditions. The device includes: a traditional model construction unit for building a traditional network-forming converter model, the traditional network-forming converter model including: an active power-frequency control loop, a reactive power-voltage control loop, a coordinate transformation system, a power calculation system, and a PWM modulation unit, the power calculation system being respectively connected to the active power-frequency control loop and the reactive power-voltage control loop, and the coordinate transformation system being respectively connected to the active power-frequency control loop, the reactive power-voltage control loop, and the PWM modulation unit; a general correlation relationship acquisition unit for obtaining a general expression for connecting a virtual synchronous machine control type converter and a droop control type converter based on the traditional network-forming converter model; a unified model construction unit for building a unified network-forming converter model applicable to transient conditions, the unified network-forming converter model including: an active power control loop unit, a reactive power control loop unit, a voltage-current inner loop unit, and a PWM modulator, the voltage-current inner loop unit being respectively connected to the active power control loop unit, the reactive power control loop unit, and the voltage-current inner loop unit; a VSG unified relationship acquisition unit for obtaining a unified expression of a virtual synchronous machine under different power loop forms based on the unified network-forming converter model; a transient unified relationship acquisition unit for obtaining a network-forming unified standard expression of the unified network-forming converter model applicable to transient conditions based on the general expression and the unified expression of the virtual synchronous machine; and a parameter design optimization unit for optimizing the parameter design of the network-forming converter under transient conditions based on the network-forming unified standard expression.

[0023] As an embodiment of the present invention, the above general correlation relationship acquisition unit includes: an active-reactive power relationship acquisition module for respectively obtaining the mathematical expressions of the active power loop and the reactive power loop in the traditional droop control, LPF type droop control, and virtual synchronous machine control in the traditional network-forming converter model; a general correlation relationship acquisition module for obtaining a general expression for connecting a virtual synchronous machine control type converter and a droop control type converter based on the mathematical expressions of the active power loop and the reactive power loop, and the general expression is as follows:

[0024]

[0025] In the above formula, ω and V are respectively the output angular velocity and the grid connection point voltage, ω 0 and V 0 are respectively the angular velocity and the grid connection point voltage commands, P and Q are respectively the electromagnetic active power and the electromagnetic reactive power, P 0 and Q 0 are respectively the active power and the reactive power commands, s is the Laplace operator, and A, B, C, and D are respectively undetermined parameters.

[0026] As an embodiment of the present invention, the VSG unified relationship acquisition unit includes: an active analysis module, which is used to analyze the differences and similarities of the active ring control of the virtual synchronous machine under different power ring forms in the unified grid-type converter model; an active relationship establishment module, which is used to establish a unified active ring expression based on the difference and similarity analysis results of the active ring control, and the active ring expression is as follows:

[0027]

[0028] In the above formula, P ref is the active power command value, P e is the electromagnetic active power, D eq is the generalized damping, J eq is the generalized inertia;

[0029] The reactive power analysis module analyzes the differences and similarities of the reactive power loop control of the virtual synchronous machine under different power loop forms in the unified grid-type converter model; the reactive power relationship establishment module establishes a unified reactive power loop expression based on the difference and similarity analysis results of the reactive power loop control, and the reactive power loop expression is as follows:

[0030]

[0031] In the above formula, E is the output voltage, U is 0 is the output voltage command value, k ep is the generalized scale parameter, k ei is the generalized integral parameter, k ev is the generalized voltage correction parameter, Q ref is the reactive power command, Q e is the electromagnetic reactive power;

[0032] The VSG unified relationship building module is used to combine the active ring expression and the reactive ring expression to obtain a unified expression of a virtual synchronous machine.

[0033] As an embodiment of the present invention, the unified standard expression of the unified grid-type converter model applicable to transient conditions is:

[0034]

[0035] As an embodiment of the present invention, the above-mentioned parameter design optimization unit includes: a first relationship table acquisition module, configured to analyze the influence of the scaling of generalized damping and generalized inertia on the frequency stability and power angle stability under transient conditions based on the network-forming unified standard expression, and obtain a first parameter-stability correspondence table; a second relationship table acquisition module, configured to analyze the influence of the presence or absence of generalized proportional parameters, generalized integral parameters, and generalized voltage correction parameters on the transient voltage stability under transient conditions based on the network-forming unified standard expression, and obtain a second parameter-stability correspondence table; a parameter adjustment module, configured to adjust the values of the generalized damping, generalized inertia, generalized proportional parameters, generalized integral parameters, and generalized voltage correction parameters of the network-forming converter under transient conditions according to the first parameter-stability correspondence table and the second parameter-stability correspondence table, so as to meet the design requirements.

[0036] As an embodiment of the present invention, the above-mentioned parameter adjustment module includes: a parameter extraction sub-module, configured to extract the control code of the network-forming converter, analyze the active loop and reactive loop expressions corresponding to the control code, and further extract the parameter variables in the control code, where the parameter variables include damping, inertia, reactive loop ratio, integral, and voltage correction coefficient; an equivalent conversion sub-module, configured to compare the extracted parameter variables with the network-forming unified standard expression and equivalently convert them into generalized damping, generalized inertia, generalized proportion, generalized integral, and generalized voltage correction parameters; an adjustment sub-module, configured to analyze the transient stability of the equivalent parameters individually, and adjust the equivalent parameters according to the first parameter-stability correspondence table and the second parameter-stability correspondence table; a reverse equivalent sub-module, configured to reverse-equivalently convert the adjusted equivalent parameters into the form in the control code through the network-forming unified standard expression, so as to improve the optimization of the working condition parameters of the control code to adapt to transient faults.

[0037] According to the third aspect of the present invention, there is provided an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the computer program, the steps of the above method are implemented.

[0038] According to the fourth aspect of the present invention, there is provided a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0039] The parameter design optimization method and device for a network-forming converter under transient conditions proposed by the present invention can more accurately analyze the transient characteristics of the network-forming converter under different control strategies by establishing a unified network-forming converter model and obtaining the corresponding unified standard expression, thereby optimizing the parameter design, improving its stability under transient conditions, and reducing or even avoiding the instability phenomenon caused by transient disturbances. In addition, the parameter optimization method proposed in this application can effectively improve the fault ride-through ability of the network-forming converter under various faults, ensure that the system can quickly resume stable operation when a fault occurs, and improve the reliability and safety of the system. Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. In the drawings:

[0041] Figure 1 is a schematic flowchart of a parameter design optimization method for a network-forming converter under transient conditions provided by an embodiment of the present application;

[0042] Figure 2 is a schematic structural diagram of a traditional network-forming converter model provided by an embodiment of the present application;

[0043] Figure 3 is a control schematic diagram of the control of a network-forming converter provided by an embodiment of the present invention;

[0044] Figure 4 is a control block diagram in a traditional network-forming converter model corresponding to the general expression provided by an embodiment of the present application;

[0045] Figure 5 is a schematic diagram of a unified network-forming converter model applicable to transient conditions built in an embodiment of the present application;

[0046] Figure 6 is a schematic flowchart of obtaining the unified expression of a virtual synchronous machine under different power loop forms provided by an embodiment of the present application;

[0047] Figure 7 is a schematic flowchart of optimizing the parameter design of a network-forming converter under transient conditions provided by an embodiment of the present application;

[0048] Figure 8 is a schematic flowchart of adjusting the parameters of a network-forming converter under transient conditions provided by an embodiment of the present application;

[0049] Figure 9It is a schematic diagram showing the influence of the active loop expression provided by the embodiments of the present application on the power angle and grid-connected voltage under the same inertia and damping parameters;

[0050] Figure 10 It is a schematic diagram showing the influence of different reactive loop expressions provided by the embodiments of the present application on the power angle and grid-connected voltage under the same parameters;

[0051] Figure 11 It is a schematic diagram showing the influence of the active loop parameters on the change of the attack angle;

[0052] Figure 12 It is a schematic diagram showing the influence of the reactive loop parameters on the grid-connected point voltage;

[0053] Figure 13 It is a schematic diagram of the structure of a parameter design optimization device for a grid-forming converter under transient conditions provided by the embodiments of the present application;

[0054] Figure 14 It is a schematic diagram of the structure of the general association relationship acquisition unit provided by the embodiments of the present application;

[0055] Figure 15 It is a schematic diagram of the structure of the VSG unified relationship acquisition unit provided by the embodiments of the present application;

[0056] Figure 16 It is a schematic diagram of the structure of the parameter design optimization unit provided by the embodiments of the present application;

[0057] Figure 17 It is a schematic diagram of the structure of the parameter adjustment module provided by the embodiments of the present application;

[0058] Figure 18 It is a schematic diagram of the structure of an electronic device provided by the embodiments of the present invention. Detailed implementation manners

[0059] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer and more understandable, the following further describes the embodiments of the present invention in detail with reference to the accompanying drawings. Herein, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not limit the present invention.

[0060] At present, there are great differences in the control structures of the power loops of grid-type converters, which leads to the following problems: First, it is difficult to compare the transient characteristics of different control loops in the same power system, which may lead to transient analysis misjudgment and thus serious faults; second, the specific manifestations of the differences in the power loop structures of grid-type converters are still unknown, the impact on transient characteristics is still unknown, and the channels connecting the respective power loops have not been explored; third, the designed grid-type fault ride-through control method requires a relatively unified grid-type converter transient expression to improve the transient stability and fault ride-through capability of the grid-type converter. The purpose of the present invention is to provide a parameter design optimization method and device for grid-type converters under transient conditions, which can realize the mutual conversion of different power control loop structures through control parameters, and analyze their respective transient characteristics, thereby realizing a relatively unified grid-type converter transient expression, and providing a solid foundation for the parameter optimization and fault ride-through control method of grid-type converters.

[0061] like Figure 1 The figure is a flow chart of a parameter design optimization method for a grid-connected converter under transient conditions provided by an embodiment of the present application, the method comprising the following steps:

[0062] Step S101: construct a traditional grid-connected converter model, wherein the traditional grid-connected converter model includes: an active frequency control loop, a reactive voltage control loop, a coordinate transformation system, a power calculation system and a PWM modulation unit.

[0063] like Figure 2 As shown, the traditional grid-type converter model constructed in this step mainly includes an active frequency control loop (i.e., active power control in the figure), a reactive voltage control loop (i.e., reactive power control in the figure), a coordinate transformation system (i.e., abc / dq in the figure), a power calculation system, and a PWM modulation unit. The power calculation system is respectively connected to the active frequency control loop and the reactive voltage control loop, and the coordinate transformation system is respectively connected to the active frequency control loop, the reactive voltage control loop, and the PWM modulation unit. Among them, the active frequency control loop simulates the damping and inertia characteristics of the synchronous motor, and the reactive voltage control loop simulates the excitation regulation characteristics of the synchronous motor. The unity of the two makes the grid-type converter present the external characteristics of a synchronous generator, V abc and I abc are three-phase voltage and three-phase current, P, Q are electromagnetic active power and electromagnetic reactive power, I d , I q , V d , V q are the direct and quadrature axis current and voltage of the dq coordinate system, θ is the calculated power angle, and are the d-axis and q-axis voltage command values ​​respectively.

[0064] Step S102: Obtain a general expression for connecting a virtual synchronous generator (VSG) - controlled converter and a droop - controlled converter based on the traditional network - forming converter model.

[0065] Preferably, this step may further include: First, respectively obtain the mathematical expressions of the active loop and the reactive loop in traditional droop control, LPF - type droop control, and virtual synchronous generator control in the traditional network - forming converter model; then obtain a general expression for connecting the VSG - controlled converter and the droop - controlled converter based on the mathematical expressions of the active loop and the reactive loop.

[0066] Virtual synchronous generator (VSG) control and droop control are two typical types of network - forming converter control, and the control principles are as shown in the appendix Figure 3 as follows, Figure 3 where (a), (b), and (c) in it respectively introduce the control block diagrams of the two controls, and among them Figure 3 both (b) and (c) belong to droop control, Figure 3 The expressions corresponding to VSG control, droop control, and LPF droop control in it are as follows in equations (1), (2), and (3):

[0067] VSG control expression:

[0068]

[0069] Droop control expression:

[0070]

[0071] LPF - type droop control expression:

[0072]

[0073] In equations (1), (2), and (3), ω * is the output angular velocity of the active loop, V * is the output voltage of the reactive loop, θ * is the output power angle of the active loop, J is the inertia constant of the active loop, D p is the damping coefficient of the active loop, D q is the voltage correction coefficient of the reactive loop, t is the integration coefficient, ω 0 and V 0 are respectively the angular velocity and the grid - connected point voltage command, P 0 and Q 0 are respectively the active power and reactive power commands, K p and K q are respectively the active droop coefficient and the reactive droop coefficient, ω p and ω qThey are the active low-pass filter coefficient and the reactive low-pass filter coefficient respectively, and θ is the successful combination angle.

[0074] After transforming the forms of equations (1), (2) and (3), they are summarized in Table 1 below:

[0075] Table 1 Comparison of Mathematical Expressions of Grid-Forming Control

[0076]

[0077] The three mathematical expressions in Table 1 have similar forms. Their general expression is as follows in equation (4), and the control block diagram in the corresponding traditional grid-forming converter model is as Figure 4 shown.

[0078]

[0079] Among them, A, B, C, and D are undetermined coefficients respectively. According to the change of the expression form of the grid-forming converter, the A, B, C, and D in equations (1), (2) and (3) are case1, case2 and case3 respectively, as follows:

[0080]

[0081] Observing equation (5), it can be seen that the traditional VSG control has inertia and damping compared with the traditional droop control, and the droop control can present certain damping and inertia characteristics in form by adding a low-pass filter (LPF). Therefore, the droop control with LPF type and the VSG control can be converted into each other in form, and the droop control is a grid-forming control without damping and inertia.

[0082] Therefore, the above equation (4) is the general expression connecting the virtual synchronous generator control type converter and the droop control type converter. This application can use equation (4) to connect the VSG control type converter and the droop control type converter, so as to realize the unification of different control structures of the grid-forming converter under the same power loop.

[0083] Step S103: Build a unified grid-forming converter model applicable to transient conditions. The unified grid-forming converter model includes: an active control loop unit, a reactive control loop unit, a voltage and current inner loop unit, and a PWM modulator. The voltage and current inner loop unit is connected to the active control loop unit, the reactive control loop unit and the voltage and current inner loop unit respectively. As Figure 5 shown is the schematic diagram of the unified grid-forming converter model applicable to transient conditions built in the example of this application. The input of the active control loop unit is the active power command value P ref and the actual active power P; then compare P ref and P, and calculate the power deviation; the power deviation passes through an inertia controller (generalized inertia Jeq and the generalized damping D eq ) Adjust to output the frequency deviation Δω; the frequency deviation Δω and the reference frequency ω 0 are added to generate the reference angle θ ref to the voltage and current inner loop unit. The input of the reactive power control loop unit is the reactive power command Q ref and the actual reactive power Q; first compare the output voltage command value U 0 and the output voltage E, and after correction by the generalized voltage correction parameter k ev , then combine it with the reactive power deviation Q ref -Q, and after integral regulation k ei / s to generate the reference voltage U ref to the voltage and current inner loop unit, where k ei is, and s is the Laplace operator.

[0084] Step S104: Obtain the unified expression of the virtual synchronous machine under different power loop forms based on the unified network-forming converter model.

[0085] Preferably, as Figure 6 shown, this step can further include the following sub-steps:

[0086] Step S1041: Analyze the differences and similarities of the active power loop control of the virtual synchronous machine under different power loop forms in the unified network-forming converter model.

[0087] In this step, first analyze the differences and similarities of the VSG active power loop control under different power loop forms, give an example to compare and analyze the internal relationship of the VSG active power loop in different forms, and then incorporate the expressions corresponding to these several VSG active power loop controls into Table 2, where k f is the frequency modulation coefficient.

[0088] Table 2 Comparison of VSG active control loop expressions

[0089]

[0090]

[0091] In the above table, T ref is the torque command value, T e is the electromagnetic torque, D is the damping, J is the inertia, and P ref is the active power command value.

[0092] Step S1042: Establish a unified active power loop expression based on the analysis results of the differences and similarities of the active power loop control.

[0093] As can be seen from Table 2, the active power loop expressions under different power loop forms can establish a unified active power loop expression (12) among each other in the way of mutually converting parameters, where D eq and J eq are the generalized damping and inertia, and the different expressions only differ in magnitude but have the same meaning.

[0094]

[0095] For the active power loop control of VSG in different forms, only the generalized inertia J eq and the generalized damping D eq are changed in magnitude, that is, the active power loop parameters are scaled. Therefore, Equation (12) can achieve the unification of the active power loop under different VSG forms, and their differences can be presented uniformly by the generalized inertia J eq and the generalized damping D eq .

[0096] Step S1043: Analyze the differences and similarities of the reactive power loop control of the virtual synchronous generator under different power loop forms in the unified network-forming converter model.

[0097] Analyze the differences and similarities of the VSG reactive power loop control under different power loop forms in the same way as in Step S1041, give examples to compare and analyze the internal relationships of the VSG reactive power loop under different forms, and incorporate several control expressions into Table 3.

[0098] Table 3 Comparison of VSG Reactive Power Control Loop Expressions

[0099]

[0100]

[0101] In the above table, k v is the voltage correction coefficient, k p is the reactive power loop proportional coefficient, k i is the reactive power loop integral coefficient, U om is the filtered grid connection point voltage, K is the reactive power integral correction coefficient, J q is the reactive power inertia coefficient, D q is the reactive power damping coefficient, and U om is the actual grid connection voltage.

[0102] Step S1044: Establish a unified reactive power loop expression based on the analysis results of the differences and similarities of the reactive power loop control.

[0103] As can be seen from Table 3, there are internal relationships in the reactive power loops under different power loop forms, that is, one is whether to add the voltage correction coefficient variable k v , and the other is whether to change the control loop parameters k p , ki , whether the three are approximately equivalent to U om =E. Therefore, a unified reactive loop expression (19) can be established, where k ep , k ei is the generalized reactive loop proportional and integral parameter, k ev is the generalized voltage correction factor.

[0104]

[0105] For different forms of VSG reactive loop control, the only difference is the generalized proportional parameter k. ep , generalized integral parameter k ei and the generalized voltage correction parameter k ev The presence or absence of (k v , k q , J q and K can be transformed into the first three). Therefore, the use of the unified reactive loop expression (19) can achieve the unification of reactive loops in different forms, and their differences can be expressed by the generalized ratio k ep 、Generalized integral k ei and generalized voltage correction k ev Unified presentation.

[0106] Step S1045: Combining the active loop expression and the reactive loop expression to obtain a unified expression of the virtual synchronous machine.

[0107] Combining equation (12) and equation (19), the unified standard expression (20) of VSG in different forms is:

[0108]

[0109] Formula (20) is an extension of formula (1), that is, the unified standard expression of VSG can be equivalent to the VSG model in a certain specific case through variation, by adjusting the scaling of active loop parameters and the presence or absence of reactive loop parameters.

[0110] Step S105: obtaining a unified standard grid-type expression of a unified grid-type converter model suitable for transient conditions based on the general expression and the unified expression of the virtual synchronous machine.

[0111] Since equation (4) connects the droop control and VSG control, and equation (20) expands the VSG control to different power loop forms, by combining equations (4) and (20), we can get the unified standard expression of the network type. The Laplace expression of equation (20) is (21):

[0112]

[0113] Formula (21) adds an imaginary coefficient E to the reactive loop numerator based on formula (4), where E is generated due to the reactive proportional parameter k ep As a result, in most cases k ep Small and approximately zero, this application ignores the generalized scale parameter k for duality considerations ep , the generalized ratio k will be analyzed in detail through simulation later ep The influence on transient characteristics and the rationality of ignoring it, the unified standard expression of the network type applicable to transient conditions is formula (22):

[0114]

[0115] The unified standard expression of the grid-type (Equation (22)) combines the grid-type converter control under different power loops, providing a theoretical model and transformation basis for the transient analysis of the grid-type converter and the subsequent parameter optimization design and fault ride-through control.

[0116] Step S106: Optimizing parameter design of the grid-type converter under transient conditions based on the grid-type unified standard expression.

[0117] Preferably, Figure 7 As shown, this step may further include the following sub-steps:

[0118] Step S1061: Based on the mesh-type unified standard expression, the influence of scaling of generalized damping and generalized inertia on frequency stability and power angle stability under transient conditions is analyzed to obtain a first parameter-stability correspondence table.

[0119] In this step, the influence of the active loop difference of the grid-type converter on the transient characteristics is first analyzed. The active loop difference is specifically manifested in the active loop parameter J eq and D eq Scaling, analysis J eq and D eq The impact on transient characteristics is to analyze the impact of active loop differences on transient characteristics.

[0120] The active loop expression of equation (22) is changed to equation (23), where Δw = w 0 -w, ΔP = P m -P e , solve the differential equation for Δw to get equation (24), and then further integrate Δw to get the power angle deviation as equation (25):

[0121]

[0122] Based on the generalized damping D eq The derivative of Δw is as shown in equations (26), (27), and (28), assuming that at the initial time t = 0, Δw(0) = 0.

[0123]

[0124] In equation (27), as the generalized damping coefficient D eq increases, the decay rate of the exponential term speeds up, and the frequency deviation tends to the steady state faster. In equation (28), the frequency deviation at steady state is smaller. Therefore, the larger D eq is, the more beneficial it is to the frequency stability under transient conditions.

[0125] Based on the generalized inertia J eq Taking the derivative of Δw, the forms are as shown in equations (29), (30), and (31). Let the initial time t = 0 and Δw(0) = 0.

[0126]

[0127] In equation (30), as the generalized inertia J eq increases, the decay rate of the exponential term slows down, the dynamic response of the frequency deviation becomes slower, the system response is smoother, but the recovery time is extended. In equation (31), the frequency deviation at steady state is independent of J eq Equation (32) shows that increasing J eq reduces the frequency deviation at the moment of fault.

[0128] Further taking the derivative of the rate of change of frequency RocoF based on J eq At t = 0, RocoF is respectively as shown in equations (33) and (34).

[0129]

[0130] Among them, equations (33) and (34) show that the larger J eq is, the smaller the change in RocoF is, and the slower the speed of frequency change is. In summary, the larger J eq is, the more beneficial it is to the frequency stability under transient conditions.

[0131] Based on the generalized damping D eq Taking the derivative of Δδ, the form is as shown in equation (35). Let the initial time t = 0 and Δw(0) = 0.

[0132]

[0133] When D eq increases, Δδ as a whole decreases, and it will accelerate the decay process of the frequency deviation and shorten the dynamic recovery time. Therefore, the larger D eq is, the more beneficial it is to the power angle stability under transient conditions.

[0134] Based on the generalized damping D eqDerive with respect to Δδ, in the form of Equation (36). Let the initial time t = 0 and Δw(0) = 0.

[0135]

[0136] When J eq increases, Δδ increases, which will slow down the attenuation process of the frequency deviation and increase the dynamic recovery time. Therefore, the larger J eq is, the more unfavorable it is to the power angle stability under transient conditions.

[0137] Therefore, the difference in the active power loop of the network-forming converter is reflected in the scaling of the active power loop parameters J eq and D eq . However, the frequency stability and power angle stability under transient conditions are affected differently by the changes in J eq and D eq , resulting in different transient characteristics of the active power loop difference of the network-forming converter. Incorporate the transient effects of the active power loop parameters J eq and D eq into Table 4 below. Table 4 is the first parameter-stability correspondence table obtained in this step.

[0138] Table 4 Transient Characteristics of the Difference in the Active Power Loop Control Structure

[0139]

[0140] In the above table, the smaller Δδ is, the better the transient power angle stability; the smaller Δw is, the better the transient frequency stability. Therefore, increasing J eq is unfavorable to the transient power angle stability but favorable to the transient frequency stability; while increasing D eq is beneficial to both the transient power angle and frequency.

[0141] Step S1062: Analyze the influence of the presence or absence of the generalized proportional parameter, generalized integral parameter, and generalized voltage correction parameter on the transient voltage stability under transient conditions based on the network-forming unified standard expression, and obtain the second parameter-stability correspondence table.

[0142] Similarly, analyze the influence of the reactive power loop of the network-forming converter on the transient characteristics. The difference in the reactive power loop is specifically reflected in the presence or absence of the reactive power loop parameters generalized proportional k ep , generalized integral k ei , and generalized voltage correction k ev . Analyzing the influence of the changes in k ep , k ei , and k ev on the transient characteristics is to analyze the influence of the difference in the reactive power loop control structure on the transient characteristics.

[0143] The reactive power loop expression of Equation (22) is transformed into Equation (37). When the order of magnitude of k ev k ei >> 1, it can be further transformed into Equation (38).

[0144]

[0145] The active power and reactive power of the network-forming converter are written as Equation (39).

[0146]

[0147] Substitute the reactive power Q e into Equation (38) and transform it into a quadratic equation about E, which can be obtained as Equation (40).

[0148]

[0149] Let Then E can be transformed into an equation about m, Equation (41), that is:

[0150]

[0151] Where

[0152] Solve the derivative of E with respect to m as Equation (42):

[0153]

[0154] Obviously, E is an increasing function of m. It can be analyzed that m is a function of the change of k ev , as shown in Equation (43) below.

[0155]

[0156] m increases linearly with the increase of k ev . Further analyze the influence of k ev on E, which is mainly divided into two aspects. One is that the increase of m directly leads to the linear increase of E. The other is that it affects E through the square root term. When m in the square root term is small, the linear term dominates and the change of E with m is small. When m is large, the square term dominates and the change of E with m is large; Generally speaking, the increase of k ev can increase E, play an instantaneous voltage support role, and improve the transient voltage stability.

[0157] Regarding the transient characteristics of k ei and k ep , the analysis is as follows.

[0158] Write the reactive power loop expression without the voltage correction coefficient k ev as follows:

[0159]

[0160] Substitute the reactive power Q e into Equation (44) and expand it into an expression about E as Equation (45):

[0161]

[0162] Under the steady-state condition (s = 1, that is, ignoring the integral term k ei / s, that is, only considering the influence of k ep , the equation at this time is:

[0163]

[0164] Use the quadratic formula to solve for the solution of E, and take the positive sign according to the physical meaning:

[0165]

[0166] Solve for the derivative of E with respect to k ep , and denote where

[0167]

[0168] Analyzing Equation (47), it can be seen that an increase in k ep will decrease the inverse term, thus reducing E as a whole; f 1 increases linearly with the increase of k ep , thus increasing E; f 2 is the square root term of k ep , and the overall growth rate slows down or even tends to be stable. Therefore, through comprehensive analysis, when k ep is small, E can be rapidly increased, improving the transient voltage stability to a certain extent, while when k ep is moderate or large, due to the decrease of the inverse term, E is reduced, significantly reducing the transient voltage stability. Therefore, the value of the generalized proportional parameter k ep should be as small as possible or eliminated.

[0169] Then analyze the influence of the change of k ei on the transient characteristics. Since k ei is the integral coefficient, from the perspective of engineering definition and effect, for the steady state, an increase in k ei will significantly improve the ability of the system to eliminate the steady-state error, and the voltage is closer to the error; while for the transient state, an increase will accelerate the voltage response, but too large an increase will introduce dynamic oscillations. Therefore, the k ei designed in this paper only needs to satisfy k ev k eiWhen the order of magnitude is >> 1.

[0170] In summary, the reactive loop parameter k caused by the difference in reactive loop structure is ep , k ei and k ev The change of will further affect the transient voltage stability of the grid-connected converter.

[0171] Therefore, the difference of reactive loop of grid-connected converter is reflected in the reactive loop parameter k ep , k ei and k ev The presence or absence of k ep , k ei and k ev The voltage stability under transient conditions has different effects on its changes, which makes the reactive loop of the grid-connected converter show different transient characteristics. ep , k ei and k ev The transient impact is summarized in the following Table 5, which is the second parameter-stability correspondence table obtained in this step.

[0172] Table 5 Transient characteristics of reactive loop control structure differences

[0173]

[0174] Step S1063: According to the first parameter-stability correspondence table and the second parameter-stability correspondence table, the values ​​of the generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter and generalized voltage correction parameter of the grid-type converter under transient conditions are adjusted to meet the design requirements.

[0175] Preferably, Figure 8 As shown, this step may further include the following sub-steps:

[0176] Step S10631: extract the control code of the grid-type converter, analyze the active loop and reactive loop expressions corresponding to the control code, and then extract the parameters in the control code, the parameters including damping, inertia, reactive loop ratio, integral and voltage correction coefficient.

[0177] Step S10632: perform parameter comparison between the extracted parameter variables and the unified standard expression of the network type, and convert them into generalized damping, generalized inertia, generalized proportion, generalized integral and generalized voltage correction parameters.

[0178] Step S10633: Transient stability of single analysis equivalent parameters (generalized damping, generalized inertia, generalized ratio, generalized integral, and generalized voltage correction parameter) is analyzed, and the equivalent parameters are adjusted according to the first parameter-stability correspondence table and the second parameter-stability correspondence table.

[0179] Step S10634: The adjusted equivalent parameters are reversely equivalent to the form in the control code through the network-forming unified standard expression, so as to optimize the working condition parameters of the control code to adapt to transient faults.

[0180] As can be seen from the above technical solutions, the parameter design optimization method for the network-forming converter under transient conditions proposed by the present invention enables the present application to more accurately analyze the transient characteristics of the network-forming converter under different control strategies by establishing a unified network-forming converter model and obtaining the corresponding unified standard expression, thereby optimizing the parameter design, improving its stability under transient conditions, and reducing or even avoiding the instability phenomenon caused by transient disturbances. In addition, the parameter optimization method proposed by the present application can effectively improve the fault ride-through ability of the network-forming converter under various faults, ensure that the system can quickly restore stable operation when a fault occurs, and improve the reliability and safety of the system.

[0181] Next, simulation experiments are carried out to verify the existence of transient characteristic differences in the power loop control structure of the network-forming converter.

[0182] First, a unified network-forming converter model applicable to transient conditions is constructed.

[0183] Build the network-forming grid-connected model shown in the appendix in Matlab / Simulink. The active power loop and the reactive power loop adopt Equation (22), and the rated active power of the network-forming is 100 kW, and the parameters are shown in Table 6. Figure 5

[0184] Table 6 Simulation parameters of the network-forming converter

[0185]

[0186] For the differential analysis of the active power loop, the same inertia and damping parameters J = 2 kg * m 2 and D = 10 N * s / m and the primary frequency modulation parameter K f = 10 are selected, and the voltage drops to 0.5 pu at the 3rd second. Analyze the influence of the active power loop in different forms on the power angle stability and the grid connection point voltage.

[0187] Figure 9Figures (a) and (b) in show the influence of the active power loop expressions in Table 2 on the power angle and grid-connected voltage under the same inertia and damping parameters. The power angle variations and voltage supports of each expression have similarities and differences. The specific reason is that when the active power loop has the same parameters, the corresponding generalized parameters of each expression are different, which will lead to the scaling of the control parameters and different effects on the power angle variation and grid-connected voltage. First, this verifies the rationality of the grid-forming unified active power loop expression; second, it shows that the active power loop under different situations will affect the transient characteristics.

[0188] For the analysis of the differences in the reactive power loop, the same generalized proportional parameter k ep = 0.0001 and the generalized integral parameter k ei = 1.15e-05 (J q = 8.6957e+04) and the voltage regulation parameter k ev = 750 (D q = 750) are selected, and the voltage drops to 0.5 pu at the 3rd second. Analyze the influence of the reactive power loop in different forms on the power angle stability and the grid-connected point voltage.

[0189] Figure 10 Figures (a) and (b) in show the influence of different reactive power loop expressions on the power angle and grid-connected voltage under the same parameters. The power angle variations and voltage supports of each expression have similarities and differences. The specific reason is that there are differences in the number of parameters in different reactive power loops, that is, differences in the design ideas and principles, and there is a phenomenon of mutual influence among the parameters during the fault process, resulting in different effects on the power angle variation and grid-connected voltage. First, this verifies the rationality of the grid-forming unified reactive power loop expression; second, it shows that the differences in the reactive power loop will affect the transient characteristics, and there is a mutual influence among the control parameters.

[0190] For the analysis of the influence of the change of active power loop parameters on the transient characteristics, the changing generalized inertia parameter J eq = 2, 5, 20, 100 and 500 kg * m 2 and the generalized damping parameter D eq = 10, 20, 50 and 200 N * s / m, and the primary frequency regulation parameter K f = 10 are selected, and the voltage drops to 0.5 pu at the 3rd second. Analyze the influence of the differences on the power angle stability and the grid-connected point voltage.

[0191] For Figure 11 in (a), as J eq changes from 2 to J eq = 100, the power angle remains stable, the power angle range becomes larger and the angular velocity range becomes smaller, that is, the power angle change slows down and the power angle is transiently stable; when J eqchanges from 100 to J eq When it is 500, the power angle loses stability, J eq The increase of can both deteriorate and inhibit the process of Vd change, which is consistent. For Figure 11 In (b) of, as D eq changes from 10 to D eq When it is 200, the power angle remains stable, the power angle range becomes larger and the angular velocity range becomes smaller, that is, increasing the generalized damping D eq parameters can enhance the power angle stability of the network-forming type

[0192] For the analysis of the influence of the change of reactive power loop parameters on the transient characteristics, the changing generalized ratio k ep is selected as 1e-4, 5e-4, 7e-4, 1e-3, and the generalized integral k ei is 2.3e-6, 5.8e-6, 1.15e-5, 4.5e-5, 5.7e-5 and the generalized voltage correction parameter k ev is 300, 450, 750, 1000. It is selected that the voltage drops to 0.5 pu at the 3rd second. Analyze the influence of the difference of reactive power parameters on the power angle stability and the grid-connected point voltage

[0193] Figure 12 As shown in (a) of, when k ep changes from 1e-4 to k ep When it is 1e-3, the grid-connected point voltage remains above 155 V (0.5 pu of the voltage drop), the transient voltage is stable, and the smaller the k ep parameter, the stronger the voltage support ability; for Figure 12 As shown in (b) of, when k ei changes from 2.3e-6 to k ei When it is 5.7e-5, the grid-connected point voltage remains at 155 V (0.5 pu of the voltage drop), the transient voltage is stable, but the voltage support ability is weakened and the voltage dynamic at the transient moment is not smooth; for Figure 12 As shown in (c) of, as k ev changes from 450 to k ev When it is 1000, the grid-connected point voltage remains above 155 V (0.5 pu of the voltage drop), which meets the grid-connected requirements during transient state and has a certain voltage support ability. Therefore, a larger k ev parameter is beneficial to transient stability and can weaken the deterioration of the power angle stability by the reactive power loop

[0194] As Figure 13The following is a schematic structural diagram of a parameter design optimization device for a grid-forming converter under transient conditions provided by an embodiment of the present application. The device includes: a traditional model construction unit 131, a general correlation relationship acquisition unit 132, a unified model construction unit 133, a VSG unified relationship acquisition unit 134, a transient unified relationship acquisition unit 135, and a parameter design optimization unit 136, which are connected in sequence. Among them:

[0195] The traditional model construction unit 131 is used to build a traditional grid-forming converter model. The traditional grid-forming converter model includes: an active frequency control loop, a reactive voltage control loop, a coordinate transformation system, a power calculation system, and a PWM modulation unit. The power calculation system is respectively connected to the active frequency control loop and the reactive voltage control loop, and the coordinate transformation system is respectively connected to the active frequency control loop, the reactive voltage control loop, and the PWM modulation unit.

[0196] The general correlation relationship acquisition unit 132 is used to obtain a general expression for connecting a virtual synchronous machine control type converter and a droop control type converter based on the traditional grid-forming converter model.

[0197] The unified model construction unit 133 is used to build a unified grid-forming converter model applicable to transient conditions. The unified grid-forming converter model includes: an active control loop unit, a reactive control loop unit, a voltage-current inner loop unit, and a PWM modulator. The voltage-current inner loop unit is respectively connected to the active control loop unit, the reactive control loop unit, and the voltage-current inner loop unit.

[0198] The VSG unified relationship acquisition unit 134 is used to obtain a unified expression of the virtual synchronous machine under different power loop forms based on the unified grid-forming converter model.

[0199] The transient unified relationship acquisition unit 135 is used to obtain a grid-forming unified standard expression of the unified grid-forming converter model applicable to transient conditions based on the general expression and the unified expression of the virtual synchronous machine.

[0200] The parameter design optimization unit 136 is used to optimize the parameter design of the grid-forming converter under transient conditions based on the grid-forming unified standard expression.

[0201] Preferably, as Figure 14 shown, the above general correlation relationship acquisition unit 132 includes:

[0202] The active-reactive relationship acquisition module 1321 is used to respectively obtain the mathematical expressions of the active loop and the reactive loop in the traditional droop control, LPF type droop control, and virtual synchronous machine control in the traditional grid-forming converter model;

[0203] The general association relationship acquisition module 1322 is used to obtain a general expression connecting the virtual synchronous machine control type converter and the droop control type converter based on the mathematical expressions of the active power loop and the reactive power loop. The general expression is as follows:

[0204]

[0205] In the above formula, ω and V are the output angular velocity and the grid connection point voltage respectively, ω 0 and V 0 are the angular velocity and the grid connection point voltage commands respectively, P and Q are the electromagnetic active power and the electromagnetic reactive power respectively, P 0 and Q 0 are the active power and reactive power commands respectively, s is the Laplace operator, and A, B, C, and D are undetermined parameters.

[0206] Preferably, as Figure 15 shown, the above VSG unified relationship acquisition unit 134 includes:

[0207] The active power analysis module 1341 is used to analyze the differences and similarities in the active power loop control of the virtual synchronous machine under different power loop forms in the unified network-forming converter model.

[0208] The active power relationship establishment module 1342 is used to establish a unified active power loop expression based on the analysis results of the differences and similarities in the active power loop control. The active power loop expression is as follows:

[0209]

[0210] In the above formula, P m is the active power command value, P e is the electromagnetic active power, D eq is the generalized damping, and J eq is the generalized inertia;

[0211] The reactive power analysis module 1343 analyzes the differences and similarities in the reactive power loop control of the virtual synchronous machine under different power loop forms in the unified network-forming converter model.

[0212] The reactive power relationship establishment module 1344 establishes a unified reactive power loop expression based on the analysis results of the differences and similarities in the reactive power loop control. The reactive power loop expression is as follows:

[0213]

[0214] In the above formula, E is the output voltage, U 0 is the output voltage command value, k ep is the generalized proportional parameter, k ei is the generalized integral parameter, kev is the generalized voltage correction parameter, Q ref is the reactive power command, Q e is the electromagnetic reactive power.

[0215] The VSG unified relationship building module 1345 is used to combine the active loop expression and the reactive loop expression to obtain a virtual synchronous machine unified expression.

[0216] Preferably, the unified standard expression of the unified grid-type converter model applicable to transient conditions is:

[0217]

[0218] Preferably, Figure 16 As shown, the parameter design optimization unit 136 includes:

[0219] The first relationship table acquisition module 1361 is used to analyze the influence of the scaling of generalized damping and generalized inertia on the frequency stability and power angle stability under transient conditions based on the unified standard expression of the network type, and obtain a first parameter-stability correspondence table.

[0220] The second relationship table acquisition module 1362 obtains the influence of the presence or absence of the generalized proportional parameter, the generalized integral parameter and the generalized voltage correction parameter on the transient voltage stability under transient conditions based on the unified standard expression of the network construction type, and obtains the second parameter-stability correspondence relationship table.

[0221] The parameter adjustment module 1363 is used to adjust the values ​​of the generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter and generalized voltage correction parameter of the grid-type converter under transient conditions according to the first parameter-stability correspondence table and the second parameter-stability correspondence table to meet the design requirements.

[0222] Preferably, Figure 17 As shown, the parameter adjustment module 1363 includes:

[0223] The parameter extraction submodule 13631 is used to extract the control code of the grid-type converter, analyze the active loop and reactive loop expressions corresponding to the control code, and then extract the parameters in the control code, including damping, inertia, reactive loop ratio, integration and voltage correction coefficient.

[0224] The equivalent conversion submodule 13632 is used to compare the extracted parameters with the unified standard expression of the network type, and convert them into generalized damping, generalized inertia, generalized proportion, generalized integral and generalized voltage correction parameters.

[0225] The adjustment sub-module 13633 is used to transiently stabilize a single analyzed equivalent parameter and adjust the equivalent parameter according to the first parameter-stability correspondence table and the second parameter-stability correspondence table.

[0226] The reverse equivalent sub-module 13634 is used to reverse-equivalent the adjusted equivalent parameter into the form in the control code through the network-constructing unified standard expression, so as to optimize the operating condition parameters of the control code to adapt to transient faults.

[0227] For the detailed descriptions of the above units and modules, reference can be made to Figure 1 the corresponding descriptions in the corresponding method embodiments, which will not be elaborated here.

[0228] As can be seen from the above technical solutions, the parameter design optimization device for the network-constructing converter under transient conditions proposed by the present invention can more accurately analyze the transient characteristics of the network-constructing converter under different control strategies by establishing a unified network-constructing converter model and obtaining the corresponding unified standard expression, thereby optimizing the parameter design, improving its stability under transient conditions, and reducing or even avoiding the instability phenomenon caused by transient disturbances. In addition, the parameter optimization method proposed in this application can effectively improve the fault ride-through ability of the network-constructing converter under various faults, ensure that the system can quickly resume stable operation when a fault occurs, and improve the reliability and safety of the system.

[0229] Figure 18 It is a schematic diagram of an electronic device provided by an embodiment of the present invention. Figure 18 The shown electronic device is a general data processing device, which includes a general computer hardware structure and at least includes a processor 801 and a memory 802. The processor 801 and the memory 802 are connected through a bus 803. The memory 802 is suitable for storing one or more instructions or programs executable by the processor 801. The one or more instructions or programs are executed by the processor 801 to implement the steps in the above parameter design optimization method for the network-constructing converter under transient conditions.

[0230] The above-mentioned processor 801 can be an independent microprocessor or a set of one or more microprocessors. Thus, the processor 801 processes data and controls other devices by executing the commands stored in the memory 802, thereby implementing the method flow of the embodiments of the present invention as described above. The bus 803 connects the above-mentioned multiple components together and also connects the above-mentioned components to the display controller 804, the display device, and the input / output (I / O) device 805. The input / output (I / O) device 805 can be a mouse, a keyboard, a modem, a network interface, a touch input device, a somatosensory input device, a printer, and other devices well-known in the art. Typically, the input / output (I / O) device 805 is connected to the system through the input / output (I / O) controller 806.

[0231] Among them, the memory 802 can store software components, such as an operating system, a communication module, an interaction module, and application programs. Each of the above-mentioned modules and application programs corresponds to a set of executable program instructions for completing one or more functions and the methods described in the embodiments of the invention.

[0232] The embodiments of the present invention also provide a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned parameter design optimization method for the grid-forming converter under transient conditions are implemented.

[0233] The parameter design optimization method and device for the grid-forming converter under transient conditions proposed by the present invention enable the present application to more accurately analyze the transient characteristics of the grid-forming converter under different control strategies by establishing a unified grid-forming converter model and obtaining the corresponding unified standard expression, thereby optimizing the parameter design, improving its stability under transient conditions, and reducing or even avoiding the instability phenomenon caused by transient disturbances. In addition, the parameter optimization method proposed in the present application can effectively improve the fault ride-through ability of the grid-forming converter under various faults, ensure that the system can quickly resume stable operation when a fault occurs, and improve the reliability and safety of the system.

[0234] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. Many features and advantages of these embodiments are clear from this detailed description. Therefore, the claims are intended to cover all these features and advantages that fall within the true spirit and scope of these embodiments. In addition, since many modifications and changes are easily conceivable by those skilled in the art, the embodiments of the present invention are not limited to the exact structures and operations illustrated and described, but may cover all suitable modifications and equivalents that fall within its scope.

[0235] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0236] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0237] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0238] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0239] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A parameter design optimization method for a grid-connected converter under transient conditions, characterized in that: The method comprises: A traditional grid-type converter model is constructed, wherein the traditional grid-type converter model comprises: an active frequency control loop, a reactive voltage control loop, a coordinate transformation system, a power calculation system and a PWM modulation unit, wherein the power calculation system is respectively connected to the active frequency control loop and the reactive voltage control loop, and the coordinate transformation system is respectively connected to the active frequency control loop, the reactive voltage control loop and the PWM modulation unit; Obtaining a general expression for connecting a virtual synchronous machine controlled converter and a droop controlled converter based on the conventional grid-type converter model; A unified grid-type converter model suitable for transient working conditions is constructed, wherein the unified grid-type converter model comprises: an active control loop unit, a reactive control loop unit, a voltage and current inner loop unit and a PWM modulator, wherein the voltage and current inner loop unit is respectively connected to the active control loop unit, the reactive control loop unit and the voltage and current inner loop unit; Based on the unified grid-type converter model, a unified expression of virtual synchronous machines under different power loop forms is obtained; Based on the general expression and the virtual synchronous machine unified expression, a unified standard expression of a unified grid-type converter model suitable for transient conditions is obtained; The parameter design of the grid-type converter under transient conditions is optimized based on the unified standard expression of the grid-type.

2. The parameter design optimization method for a grid-connected converter under transient conditions according to claim 1, characterized in that: The general expression for connecting the virtual synchronous machine control type converter and the droop control type converter based on the traditional grid-type converter model includes: The mathematical expressions of active loop and reactive loop in traditional droop control, LPF type droop control and virtual synchronous machine control in traditional grid-connected converter model are obtained respectively; Based on the mathematical expressions of the active loop and the reactive loop, a general expression for connecting the virtual synchronous machine controlled converter and the droop controlled converter is obtained, and the general expression is as follows: In the above formula, ω and V are the output angular velocity and grid-connected point voltage respectively, ω0 and V0 are the angular velocity and grid-connected point voltage instructions respectively, P and Q are the electromagnetic active power and electromagnetic reactive power respectively, P0 and Q0 are the active power and reactive power instructions respectively, s is the Laplace operator, and A, B, C, and D are unknown parameters respectively.

3. The parameter design optimization method for a grid-connected converter under transient conditions according to claim 2, characterized in that: The unified expression of virtual synchronous machines under different power ring forms obtained based on the unified grid-type converter model includes: Analyze the differences and similarities of the active loop control of the virtual synchronous machine under different power loop forms in the unified grid-connected converter model; A unified active loop expression is established based on the difference and similarity analysis results of the active loop control, and the active loop expression is as follows: In the above formula, P ref is the active power command value, P e is the electromagnetic active power, D eq is the generalized damping, J eq is the generalized inertia; Analyze the differences and similarities of the reactive loop control of virtual synchronous machines under different power loop forms in the unified grid-connected converter model; Based on the difference and similarity analysis results of the reactive loop control, a unified reactive loop expression is established, and the reactive loop expression is as follows: In the above formula, E is the output voltage, U0 is the output voltage command value, k ep is the generalized scale parameter, k ei is the generalized integral parameter, k ev is the generalized voltage correction parameter, Q ref is the reactive power command, Q e is the electromagnetic reactive power; The active loop expression and the reactive loop expression are combined to obtain a unified expression of the virtual synchronous machine.

4. The parameter design optimization method for a grid-connected converter under transient conditions according to claim 3, characterized in that: The unified standard expression of the unified grid-type converter model applicable to transient conditions is:

5. The parameter design optimization method for a grid-connected converter under transient conditions according to claim 4, characterized in that: The method of optimizing the parameter design of the grid-type converter under transient conditions based on the grid-type unified standard expression includes: Based on the unified standard expression of the network type, the influence of the scaling of generalized damping and generalized inertia on the frequency stability and power angle stability under transient conditions is analyzed, and the first parameter-stability correspondence table is obtained; Based on the unified standard expression of the network type, the influence of the presence or absence of the generalized proportional parameter, the generalized integral parameter and the generalized voltage correction parameter on the transient voltage stability under transient conditions is analyzed, and a second parameter-stability correspondence table is obtained; According to the first parameter-stability correspondence table and the second parameter-stability correspondence table, the values ​​of the generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter and generalized voltage correction parameter of the grid-type converter under transient conditions are adjusted to meet the design requirements.

6. The parameter design optimization method for a grid-connected converter under transient conditions according to claim 5, characterized in that: The adjusting the values ​​of the generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter and generalized voltage correction parameter of the grid-type converter under transient conditions according to the first parameter-stability correspondence table and the second parameter-stability correspondence table to meet the design requirements includes: Extracting the control code of the grid-type converter, analyzing the active loop and reactive loop expressions corresponding to the control code, and then extracting the parameters in the control code, wherein the parameters include damping, inertia, reactive loop ratio, integral and voltage correction coefficient; Comparing the extracted parameters with the unified standard expression of the network type, and converting them into generalized damping, generalized inertia, generalized proportion, generalized integral and generalized voltage correction parameters; Single analysis of transient stability of equivalent parameters, and adjustment of equivalent parameters according to the first parameter-stability correspondence table and the second parameter-stability correspondence table; The adjusted equivalent parameters are reversely converted into the form in the control code through the unified standard expression of the network type, so as to improve the optimization of the operating parameters of the control code to adapt to transient faults.

7. A parameter design optimization device for a grid-type converter under transient conditions, characterized in that: The device comprises: A traditional model building unit, used for building a traditional grid-type converter model, the traditional grid-type converter model comprising: an active frequency control loop, a reactive voltage control loop, a coordinate transformation system, a power calculation system and a PWM modulation unit, the power calculation system is respectively connected to the active frequency control loop and the reactive voltage control loop, the coordinate transformation system is respectively connected to the active frequency control loop, the reactive voltage control loop and the PWM modulation unit; A general association relationship acquisition unit, used for obtaining a general expression for connecting a virtual synchronous machine control type converter and a droop control type converter based on the traditional grid-forming converter model; A unified model building unit, used for building a unified grid-type converter model suitable for transient working conditions, the unified grid-type converter model comprising: an active control loop unit, a reactive control loop unit, a voltage and current inner loop unit and a PWM modulator, the voltage and current inner loop unit being connected to the active control loop unit, the reactive control loop unit and the voltage and current inner loop unit respectively; A VSG unified relationship acquisition unit, used to obtain a unified expression of a virtual synchronous machine under different power loop forms based on the unified grid-type converter model; A transient unified relationship acquisition unit, used for obtaining a unified standard grid-type expression of a unified grid-type converter model suitable for transient working conditions based on the general expression and the unified expression of the virtual synchronous machine; A parameter design optimization unit is used to optimize the parameter design of the grid-type converter under transient conditions based on the unified standard expression of the grid-type.

8. The parameter design optimization device for a grid-type converter under transient conditions according to claim 7, characterized in that: The general association relationship acquisition unit includes: An active / reactive relationship acquisition module is used to respectively acquire mathematical expressions of active loop and reactive loop in traditional droop control, LPF type droop control and virtual synchronous machine control in traditional grid-connected converter model; A general association relationship acquisition module is used to obtain a general expression for connecting a virtual synchronous machine controlled converter and a droop controlled converter based on the mathematical expressions of the active loop and the reactive loop, wherein the general expression is as follows: In the above formula, ω and V are the output angular velocity and grid-connected point voltage respectively, ω0 and V0 are the angular velocity and grid-connected point voltage instructions respectively, P and Q are the electromagnetic active power and electromagnetic reactive power respectively, P0 and Q0 are the active power and reactive power instructions respectively, s is the Laplace operator, and A, B, C, and D are unknown parameters respectively.

9. The parameter design optimization device for a grid-type converter under transient conditions according to claim 8, characterized in that: The VSG unified relationship acquisition unit includes: An active power analysis module, used to analyze the differences and similarities of active power loop control of virtual synchronous machines under different power loop forms in the unified grid-type converter model; The active power relationship establishment module is used to establish a unified active power loop expression based on the difference and similarity analysis results of the active power loop control. The active power loop expression is as follows: In the above formula, P ref is the active power command value, P e is the electromagnetic active power, D eq is the generalized damping, J eq is the generalized inertia; A reactive power analysis module, which analyzes the differences and similarities of reactive power loop control of virtual synchronous machines under different power loop forms in the unified grid-connected converter model; The reactive relationship establishment module establishes a unified reactive loop expression based on the difference and similarity analysis results of the reactive loop control. The reactive loop expression is as follows: In the above formula, E is the output voltage, U0 is the output voltage command value, k ep is the generalized scale parameter, k ei is the generalized integral parameter, k ev is the generalized voltage correction parameter, Q ref is the reactive power command, Q e is the electromagnetic reactive power; The VSG unified relationship building module is used to combine the active ring expression and the reactive ring expression to obtain a unified expression of a virtual synchronous machine.

10. The parameter design optimization device for a grid-type converter under transient conditions according to claim 9, characterized in that: The unified standard expression of the unified grid-type converter model applicable to transient conditions is:

11. The parameter design optimization device for a grid-connected converter under transient conditions according to claim 10, characterized in that: The parameter design optimization unit comprises: A first relationship table acquisition module is used to analyze the influence of the scaling of generalized damping and generalized inertia on the frequency stability and power angle stability under transient conditions based on the unified standard expression of the network type, and obtain a first parameter-stability correspondence relationship table; A second relationship table acquisition module, based on the unified standard expression of the network type, analyzes the influence of the presence or absence of the generalized proportional parameter, the generalized integral parameter and the generalized voltage correction parameter on the transient voltage stability under transient conditions, and obtains a second parameter-stability correspondence relationship table; A parameter adjustment module is used to adjust the values ​​of generalized damping, generalized inertia, generalized proportional parameter, generalized integral parameter and generalized voltage correction parameter of the grid-type converter under transient conditions according to the first parameter-stability correspondence table and the second parameter-stability correspondence table to meet design requirements.

12. The parameter design optimization device for a grid-connected converter under transient conditions according to claim 11, characterized in that: The parameter adjustment module comprises: A parameter extraction submodule is used to extract the control code of the grid-type converter, analyze the active loop and reactive loop expressions corresponding to the control code, and then extract the parameters in the control code, wherein the parameters include damping, inertia, reactive loop ratio, integral and voltage correction coefficient; An equivalent conversion submodule is used to compare the extracted parameter variables with the unified standard expression of the network type, and convert them into generalized damping, generalized inertia, generalized proportion, generalized integral and generalized voltage correction parameters; An adjustment submodule, used for analyzing the transient stability of equivalent parameters in a single manner, and adjusting the equivalent parameters according to the first parameter-stability correspondence table and the second parameter-stability correspondence table; The reverse equivalent submodule is used to reversely convert the adjusted equivalent parameters into the form in the control code through the unified standard expression of the network type, so as to improve the optimization of the operating parameters of the control code to adapt to transient faults.

13. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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