CN117895487A - Grid-connected converter dynamic inertia quantitative evaluation method and system - Google Patents
Grid-connected converter dynamic inertia quantitative evaluation method and system Download PDFInfo
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Abstract
The invention discloses a method for quantitatively evaluating dynamic inertia of a grid-connected converter, which comprises the following steps: and establishing a transfer function model of the system frequency response and acquiring system parameters. And obtaining a characteristic equation according to the transfer function model, solving the characteristic equation to obtain a characteristic mode of the system, then calculating a zero point of the transfer function, and screening out the characteristic mode with the minimum damping as a dominant characteristic mode of the system. Substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, reducing the equivalent order of the transfer function into a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term. And calculating to obtain the inertia constant after the dynamic inertia quantization evaluation. The invention has the advantages that: the stability of the system is enhanced, the regulation performance of the system is improved, the risk of system instability is reduced, and the reliability of the system is improved.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a grid-connected converter dynamic inertia quantitative evaluation method and system based on dominant characteristic modes.
Background
The dynamic inertia of the grid-connected converter refers to the inertia provided by the grid-connected converter to the power grid under the condition of considering the dynamic characteristics of the controller. The dynamic response capability of the grid-connected converter under the conditions of grid frequency change or grid faults and the like is reflected, and the dynamic response capability can be used for evaluating the supporting capability of the grid-connected converter to the grid. The quantitative evaluation of the dynamic inertia can help to know the dynamic characteristics of the system and provide important references for optimizing the control strategy.
The characteristic mode refers to characteristic values of a transfer function of the system, the characteristic values determine the overall dynamic characteristic of the system, the real part of the characteristic values influences the stability of the system, and the imaginary part influences the oscillation property of the system; the dominant feature mode refers to one or a group of feature roots which have significant influence on the dynamic characteristics of the system in all feature modes of the system.
The existing quantitative evaluation method for the dynamic inertia of the grid-connected converter realizes quantitative evaluation by neglecting the medium-high order terms of the dynamic inertia expression, and the inertia constant obtained based on the quantitative evaluation method can not only reflect the influence of the dynamic characteristics of the system on the dynamic inertia of the grid-connected converter, but also can not accurately reflect the influence of the controller parameters on the dynamic inertia of the grid-connected converter.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method and a system for quantitatively evaluating the dynamic inertia of a grid-connected converter.
In order to achieve the above object, the present invention adopts the following technical scheme:
a grid-connected converter dynamic inertia quantitative evaluation method comprises the following steps:
establishing a transfer function model of the system frequency response and acquiring system parameters, wherein the system parameters comprise: inertia constant and damping constant of synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of speed regulator part, dynamic inertia and dynamic damping of grid-connected converter and frequency adjustment response coefficient of load.
And obtaining a characteristic equation of the transfer function according to the transfer function model, obtaining a characteristic mode of the system by solving the characteristic equation, calculating a zero point of the transfer function, and screening out the characteristic mode with the minimum damping as a dominant characteristic mode of the system under the condition of considering zero point and characteristic mode approximate cancellation.
Substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, reducing the equivalent order of the transfer function into a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term. And based on the dominant characteristic mode, realizing quantitative evaluation of the dynamic inertia of the grid-connected converter, and calculating to obtain an inertia constant after quantitative evaluation of the dynamic inertia.
Further, the transfer function model includes:
transfer function of grid-connected inverter: describes the response characteristic of the grid-connected converter to frequency disturbance, which is formed by dynamic inertia H c (s) and dynamic damping D c (s) composition, s representing complex frequencies in the transfer function.
Transfer function of synchronous generator: inertia constant H including synchronous generator sg Damping constant D sg Equivalent transfer function G of governor part gov (s) describing the response of the synchronous generator when the frequency is changed, wherein R is the difference adjustment coefficient of primary frequency modulation of the synchronous generator.
Transfer function of load: describing the response characteristic of the load to the frequency variation, the response coefficient D is regulated by the frequency l Composition is prepared.
Further, the characteristic mode is obtained through the following procedures:
deriving a transfer function between the system frequency response quantity and the power disturbance quantity according to the transfer function model, wherein the transfer function is expressed as:
where Δp is the power disturbance of the system, and Δω is the frequency response of the system.
The transfer function is characterized by the following equation (1):
(G gov (s)/R+2H c (s)+D c (s)s+2H sg s+D sg +D l )＝0 (2)
the solution of the characteristic equation in the formula (2) is the characteristic mode of the system, so that lambda is assumed i ＝-ε i +jω i ,i∈[1,n]Is the ith solution of the characteristic equation, lambda i ＝-ε i +jω i ,i∈[1,n]Is a characteristic mode of the system. Wherein n is the order of the characteristic equation, i represents an integer variable, j represents the imaginary sign of the complex number, ε i And omega i Respectively represent the damping and oscillation frequency of the characteristic mode epsilon i ＞0。
Further, the dominant characteristic mode of the system is obtained through the following procedures:
calculating the zero point of the transfer function in the formula (1), namely solving the equation:
assuming that the dominant characteristic mode of the system is lambda d ＝-ε d +jω d Zero point of system transfer function is z k K is the number of zero points, and then the full necessary conditions of the dominant characteristic mode are screened out from all characteristic modesThe method comprises the following steps:
wherein ε d 、ω d Damping and oscillation frequency of dominant characteristic modes respectively; min { } represents taking the minimum value, and |represents taking the absolute value.
Further, the quantitative evaluation of the dynamic inertia of the grid-connected converter is specifically as follows:
the dominant characteristic mode lambda of the system d Substituting the transfer function of the frequency response link of the grid-connected converter into the following formula:
wherein ε g 、ω g Respectively representDamping and oscillation frequency of (a).
Since s=λ d ＝-ε d +jω d Then at lambda d 2H under dominant system dynamics c (s)s+D c (s) is equivalent to:
calculating inertia constantThe expression is:
in the method, in the process of the invention,representation quantization scaleAnd estimating an inertia constant obtained by the dynamic inertia of the grid-connected converter.
The invention discloses a grid-connected converter dynamic inertia quantitative evaluation system which can be used for implementing the grid-connected converter dynamic inertia quantitative evaluation method, and specifically comprises the following steps:
parameter acquisition module: the method is used for acquiring system parameters, including inertia constant and damping constant of the synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of a speed regulator part, dynamic inertia and dynamic damping of the grid-connected converter and frequency adjustment response coefficient of load.
A system frequency response modeling module: and establishing a transfer function model of the system frequency response, and acquiring system parameters.
And a characteristic equation solving module: and obtaining a characteristic equation according to the transfer function model, and then obtaining a characteristic mode of the system by solving the characteristic equation.
Zero point and characteristic mode screening module: and calculating the zero point of the transfer function, and screening out the characteristic mode with the minimum damping as the dominant characteristic mode of the system under the condition of considering the approximate cancellation of the zero point and the characteristic mode.
Frequency response equivalent order reduction module: substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, reducing the equivalent order of the transfer function into a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term.
Dynamic inertia quantitative evaluation module: and calculating the inertia constant after the dynamic inertia quantization evaluation.
The invention also discloses computer equipment, which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor realizes the grid-connected converter dynamic inertia quantitative evaluation method when executing the program.
The invention also discloses a computer readable storage medium, on which a computer program is stored, which when being executed by a processor, realizes the grid-connected converter dynamic inertia quantitative evaluation method.
Compared with the prior art, the invention has the advantages that:
1. enhancing system stability: through the dynamic inertia quantitative evaluation, the inertia characteristics of the grid-connected converter can be evaluated to ensure that the grid-connected converter has proper dynamic response capability to the system frequency change, so that the stability of the power system is enhanced.
2. Optimizing system adjustment: the control strategy of the grid-connected converter can be optimized through dynamic inertia quantitative evaluation, so that the grid-connected converter can respond to the change of the system frequency better, and the regulation performance of the system is improved.
3. The risk of system instability is reduced: by adopting the dynamic inertia quantitative evaluation method, the possible unstable condition of the grid-connected converter when the system frequency changes can be found in time, so that measures can be taken in time to reduce the risk of system instability.
4. The system reliability is improved: by quantitatively evaluating the dynamic inertia of the grid-connected converter, the grid-connected converter can be ensured to have good dynamic response characteristics, so that the reliability and stability of the system are improved.
Drawings
Fig. 1 is a flowchart of a method for quantitatively evaluating dynamic inertia of a grid-connected inverter according to an embodiment of the invention;
FIG. 2 is a graph of a transfer function model of the system frequency response of an embodiment of the present invention;
FIG. 3 is a graph of a transfer function model of the system frequency response of an experiment of an embodiment of the invention.
Detailed Description
The invention will be described in further detail below with reference to the accompanying drawings and by way of examples in order to make the objects, technical solutions and advantages of the invention more apparent.
The invention provides a method for quantitatively evaluating dynamic inertia of a grid-connected converter, which is shown in fig. 1 and comprises the following steps:
step one: establishing a transfer function model of system frequency response, and acquiring system parameters; the system parameters include: inertia constant and damping constant of synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of speed regulator part; dynamic inertia and dynamic damping of the grid-connected converter; the frequency of the load adjusts the response coefficient.
Step two: extracting a characteristic equation according to the system transfer function model, calculating the root of the characteristic equation to obtain a characteristic mode of the system, solving the zero point of the system transfer function model, and finally screening out the characteristic mode with the minimum damping as a dominant characteristic mode of the system under the condition of considering the approximate cancellation of the zero point and the characteristic mode.
Step three: substituting the dominant characteristic mode of the system into the transfer function of the frequency response link of the grid-connected converter, reducing the equivalent of the transfer function into a first-order transfer function, further correspondingly obtaining coefficients before a first-order term, and finally calculating according to the formula to obtain the inertia constant after the dynamic inertia quantization evaluation.
The transfer function model of the system frequency response is established, and the transfer function model is specifically as follows:
in order to calculate the dominant characteristic mode of the system, a transfer function model of the system frequency response needs to be established first, and the transfer function model mainly comprises frequency response links of a grid-connected converter, a synchronous generator and a load, and the specific structure is shown in figure 2.
In FIG. 2, H c (s) and D c (s) the dynamic inertia and the dynamic damping of the grid-connected converter are respectively, and are in a transfer function form, and s represents complex frequency in the transfer function; h sg And D sg Respectively inertia constant and damping constant of the synchronous generator, R is a difference adjustment coefficient of primary frequency modulation of the synchronous generator, G gov (s) is the equivalent transfer function of the synchronous generator governor portion; d (D) l The response coefficients are adjusted for the frequency of the load, and ΔP and Δω are the power disturbance quantity and the frequency response quantity of the system, respectively.
The dominant characteristic mode of the computing system is as follows:
from the transfer function model of the system frequency response, the transfer function expression between the system frequency response quantity and the power disturbance quantity can be deduced as follows:
the characteristic equation of the transfer function, which is obtained by equation (1), is:
(G gov (s)/R+2H c (s)+D c (s)s+2H sg s+D sg +D l )＝0 (2)
the solution of the characteristic equation in the formula (2) is the characteristic mode of the system, so that lambda is assumed i ＝-ε i +jω i ,i∈[1,n]Is the ith solution of the characteristic equation, lambda i ＝-ε i +jω i ,i∈[1,n]Is a characteristic mode of the system. Wherein n is the order of the characteristic equation, i represents an integer variable, j represents the imaginary sign of the complex number, ε i And omega i Respectively represent the damping and oscillation frequency of the characteristic mode epsilon i ＞0。
Among all the characteristic modes of the system, the dominant characteristic mode of the system is one characteristic mode with decisive influence on the dynamic characteristics of the system, and the damping epsilon of the characteristic mode is determined d Is the least damped of all characteristic modes, and the zero point of the transfer function model is not approximately canceled.
It is therefore first necessary to calculate the zero point of the transfer function in equation (1), i.e. solve the equation:
the solution of the equation in the formula (3) is the zero point of the system, and the dominant characteristic mode of the system is lambda d ＝-ε d +jω d Zero point of system transfer function is z k K is the number of zero points, and the sufficient and necessary conditions for screening dominant characteristic modes from all characteristic modes are as follows:
ε d 、ω d damping and oscillation frequency of dominant characteristic modes respectively; min { } represents taking the minimum value, and |represents taking the absolute value.
The quantitative evaluation of the dynamic inertia of the grid-connected converter is specifically as follows:
the dominant characteristic mode lambda of the system d Substituting the transfer function of the frequency response link of the grid-connected converter to obtain:
ε g 、ω g respectively representIn turn, equation (5) can be expressed as,
since s=λ d ＝-ε d +jω d Then at lambda d 2H under dominant system dynamics c (s)s+D c (s) can be equivalently:
it can be seen that in the dominant characteristic mode lambda of the system d And the transfer function of the higher order in the frequency response of the grid-connected converter can be equivalent to a transfer function of the first order, and the dynamic characteristics of the transfer function and the transfer function are identical. The low-frequency dynamic characteristic of the common alternating current system is usually determined by a dominant characteristic mode, so that quantitative evaluation of the dynamic inertia of the grid-connected converter can be realized based on the dominant characteristic mode, and the obtained inertia constantThe expression is given by the formula (I),
in the method, in the process of the invention,and (5) representing an inertia constant obtained by quantitatively evaluating the dynamic inertia of the grid-connected converter.
The following is an example of a grid-connected converter dynamic inertia quantitative evaluation method;
the system parameters are set as follows:
synchronous generator: inertia constant H sg =1, damping constant D sg Difference coefficient r=0.01 for primary frequency modulation, equivalent transfer function of governor part
Grid-connected converters: dynamic inertiaDynamic damping D c (s)＝0；
Load: frequency adjustment response coefficient D l ＝0.2
Step one: according to the system parameters, a transfer function model of the frequency response of the example system is established, as shown in FIG. 3;
step two: based on the transfer function model, the transfer function between the system frequency response and the power disturbance variable is expressed as:
for characteristic equationSolving, the characteristic modes of the system can be obtained as follows:
λ 1 ＝-0.49，λ 2,3 ＝-1.21±j3.94，λ 4,5 ＝-10.11±j4.42，λ 6 ＝-34.23
equation of pairSolving, wherein the zero point of the available system is as follows:
z 1 ＝-0.14，z 2 ＝-5.00，z 3,4 ＝-6.94±j7.01，z 5 ＝-10.00
then the sufficiency and the necessity of screening dominant characteristic modes are completely overcome
Lambda can be found 1 And z 1 The situation of zero pole cancellation exists, and the dominant characteristic mode of the system is lambda d ＝λ 2,3 ＝-1.21±j3.94。
Step three: the dominant characteristic mode lambda of the system d Substituting the transfer function of the frequency response link of the grid-connected converter to obtain
Based on the method provided by the invention, according toCalculating inertia constant of available grid-connected converter
If the prior technical scheme is adopted, the quantitative evaluation is carried out by directly neglecting the higher-order term of the time-varying inertia, namely 0.072s 2 =0, then grid-tied inverter dynamic inertiaThe inertia constant obtained after the quantization was 2.
In still another embodiment of the present invention, a quantized evaluation system of dynamic inertia of a grid-connected inverter is provided, where the system can be used to implement the quantized evaluation method of dynamic inertia of a grid-connected inverter, and specifically includes:
parameter acquisition module: the method is used for acquiring system parameters, including inertia constant and damping constant of the synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of a speed regulator part, dynamic inertia and dynamic damping of the grid-connected converter and frequency adjustment response coefficient of load.
A system frequency response modeling module: and establishing a transfer function model of the system frequency response, and acquiring system parameters.
And a characteristic equation solving module: and obtaining a characteristic equation according to the transfer function model, and then obtaining a characteristic mode of the system by solving the characteristic equation.
Zero point and characteristic mode screening module: and calculating the zero point of the transfer function, and screening out the characteristic mode with the minimum damping as the dominant characteristic mode of the system under the condition of considering the approximate cancellation of the zero point and the characteristic mode.
Frequency response equivalent order reduction module: substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, reducing the equivalent order of the transfer function into a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term.
Dynamic inertia quantitative evaluation module: and calculating the inertia constant after the dynamic inertia quantization evaluation.
In yet another embodiment of the present invention, a terminal device is provided, the terminal device including a processor and a memory, the memory for storing a computer program, the computer program including program instructions, the processor for executing the program instructions stored by the computer storage medium. The processor may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), off-the-shelf Programmable gate arrays (FPGAs) or other Programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which are the computational core and control core of the terminal adapted to implement one or more instructions, in particular adapted to load and execute one or more instructions to implement a corresponding method flow or a corresponding function; the processor provided by the embodiment of the invention can be used for the operation of the grid-connected converter dynamic inertia quantitative evaluation method, and comprises the following steps:
by establishing a transfer function model of the system frequency response and acquiring system parameters, the system parameters comprise: inertia constant and damping constant of synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of speed regulator part, dynamic inertia and dynamic damping of grid-connected converter and frequency adjustment response coefficient of load.
And obtaining a characteristic equation of the transfer function according to the transfer function model, obtaining a characteristic mode of the system by solving the characteristic equation, calculating a zero point of the transfer function, and screening out the characteristic mode with the minimum damping as a dominant characteristic mode of the system under the condition of considering zero point and characteristic mode approximate cancellation.
Substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, reducing the equivalent order of the transfer function into a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term. And based on the dominant characteristic mode, realizing quantitative evaluation of the dynamic inertia of the grid-connected converter, and calculating to obtain an inertia constant after quantitative evaluation of the dynamic inertia.
In a further embodiment of the present invention, the present invention also provides a storage medium, in particular, a computer readable storage medium (Memory), which is a Memory device in a terminal device, for storing programs and data. It will be appreciated that the computer readable storage medium herein may include both a built-in storage medium in the terminal device and an extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space storing an operating system of the terminal. Also stored in the memory space are one or more instructions, which may be one or more computer programs (including program code), adapted to be loaded and executed by the processor. The computer readable storage medium herein may be a high-speed RAM memory or a non-volatile memory (non-volatile memory), such as at least one magnetic disk memory.
One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the respective steps of the method for quantitative assessment of dynamic inertia of a parallel network converter in the above embodiments; one or more instructions in a computer-readable storage medium are loaded by a processor and perform the steps of:
by establishing a transfer function model of the system frequency response and acquiring system parameters, the system parameters comprise: inertia constant and damping constant of synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of speed regulator part, dynamic inertia and dynamic damping of grid-connected converter and frequency adjustment response coefficient of load.
And obtaining a characteristic equation of the transfer function according to the transfer function model, obtaining a characteristic mode of the system by solving the characteristic equation, calculating a zero point of the transfer function, and screening out the characteristic mode with the minimum damping as a dominant characteristic mode of the system under the condition of considering zero point and characteristic mode approximate cancellation.
Substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, reducing the equivalent order of the transfer function into a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term. And based on the dominant characteristic mode, realizing quantitative evaluation of the dynamic inertia of the grid-connected converter, and calculating to obtain an inertia constant after quantitative evaluation of the dynamic inertia.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Those of ordinary skill in the art will appreciate that the embodiments described herein are intended to aid the reader in understanding the practice of the invention and that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (8)
1. The grid-connected converter dynamic inertia quantitative evaluation method is characterized by comprising the following steps of:
by establishing a transfer function model of the system frequency response and acquiring system parameters, the system parameters comprise: inertia constant and damping constant of synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of speed regulator part, dynamic inertia and dynamic damping of grid-connected converter and frequency adjustment response coefficient of load;
obtaining a characteristic equation of a transfer function according to the transfer function model, obtaining a characteristic mode of the system by solving the characteristic equation, calculating a zero point of the transfer function, and screening out the characteristic mode with the minimum damping as a dominant characteristic mode of the system under the condition of considering zero point and characteristic mode approximate cancellation;
substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, performing equivalent reduction to obtain a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term; and based on the dominant characteristic mode, realizing quantitative evaluation of the dynamic inertia of the grid-connected converter, and calculating to obtain an inertia constant after quantitative evaluation of the dynamic inertia.
2. The grid-connected inverter dynamic inertia quantitative evaluation method according to claim 1, wherein the method comprises the following steps of: the transfer function model includes:
transfer function of grid-connected inverter: describes the response characteristic of the grid-connected converter to frequency disturbance, which is formed by dynamic inertia H c (s) and dynamic damping D c (s) composition, s representing complex frequencies in the transfer function;
transfer function of synchronous generator: inertia constant H including synchronous generator sg Damping constant D sg Equivalent transfer function G of governor part gov (s) describing the response of the synchronous generator when the frequency is changed, wherein R is the difference adjustment coefficient of primary frequency modulation of the synchronous generator;
transfer function of load: describing the response characteristic of the load to the frequency variation, the response coefficient D is regulated by the frequency l Composition is prepared.
3. The grid-connected inverter dynamic inertia quantitative evaluation method according to claim 2, wherein the method comprises the following steps of: the characteristic mode is obtained through the following procedures:
deriving a transfer function between the system frequency response quantity and the power disturbance quantity according to the transfer function model, wherein the transfer function is expressed as:
wherein, delta P is the power disturbance quantity of the system, delta omega is the frequency response quantity of the system;
the transfer function is characterized by the following equation (1):
(G gov (s)/R+2H c (s)+D c (s)s+2H sg s+D sg +D l )＝0(2)
the solution of the characteristic equation in the formula (2) is the characteristic mode of the system, so that lambda is assumed i ＝-ε i +jω i ,i∈[1,n]Is the ith solution of the characteristic equation, lambda i ＝-ε i +jω i ,i∈[1,n]Is a characteristic mode of the system; wherein n is the order of the characteristic equation, i represents an integer variable, j represents the imaginary sign of the complex number, ε i And omega i Respectively represent the damping and oscillation frequency of the characteristic mode epsilon i ＞0。
4. The grid-connected inverter dynamic inertia quantitative evaluation method according to claim 3, wherein the method comprises the following steps of: the dominant characteristic mode of the system is obtained through the following procedures:
calculating the zero point of the transfer function in the formula (1), namely solving the equation:
assuming that the dominant characteristic mode of the system is lambda d ＝-ε d +jω d Zero point of system transfer function is z k K is the number of zero points, and the sufficient and necessary conditions for screening dominant characteristic modes from all characteristic modes are as follows:
wherein ε d 、ω d Damping and oscillation frequency of dominant characteristic modes respectively; min { } represents taking the minimum value, and |represents taking the absolute value.
5. The method for quantitatively evaluating the dynamic inertia of the grid-connected converter according to claim 4, which is characterized in that: the quantitative evaluation of the dynamic inertia of the grid-connected converter is specifically as follows:
the dominant characteristic mode lambda of the system d Substituting the transfer function of the frequency response link of the grid-connected converter into the following formula:
wherein ε g 、ω g Respectively representDamping and oscillation frequency of (a);
since s=λ d ＝-ε d +jω d Then at lambda d 2H under dominant system dynamics c (s)s+D c (s) is equivalent to:
calculating inertia constantThe expression is:
in the method, in the process of the invention,representing quantitative assessment andand an inertia constant obtained by the dynamic inertia of the network converter.
6. A grid-connected inverter dynamic inertia quantitative evaluation system is characterized in that: the system can be used for implementing the grid-connected converter dynamic inertia quantitative evaluation method according to one of claims 1 to 5, and specifically comprises the following steps:
parameter acquisition module: the method comprises the steps of obtaining system parameters, including inertia constant and damping constant of a synchronous generator, primary frequency modulation difference adjustment coefficient, equivalent transfer function of a speed regulator part, dynamic inertia and dynamic damping of a grid-connected converter and frequency adjustment response coefficient of a load;
a system frequency response modeling module: establishing a transfer function model of system frequency response, and acquiring system parameters;
and a characteristic equation solving module: obtaining a characteristic equation according to the transfer function model, and then obtaining a characteristic mode of the system by solving the characteristic equation;
zero point and characteristic mode screening module: calculating the zero point of the transfer function, and screening out the characteristic mode with the minimum damping as the dominant characteristic mode of the system under the condition of considering the approximate cancellation of the zero point and the characteristic mode;
frequency response equivalent order reduction module: substituting the dominant characteristic mode of the system into a transfer function of a frequency response link of the grid-connected converter, performing equivalent reduction to obtain a first-order transfer function, and correspondingly obtaining a coefficient before a first-order term;
dynamic inertia quantitative evaluation module: and calculating the inertia constant after the dynamic inertia quantization evaluation.
7. A computer device, characterized by: comprising a memory, a processor and a computer program stored on the memory and executable on the processor, said processor implementing the grid-tie inverter dynamic inertia quantitative evaluation method according to one of claims 1 to 5 when executing said program.
8. A computer-readable storage medium, characterized by: a computer program stored thereon, which when executed by a processor, implements the grid-tie inverter dynamic inertia quantitative assessment method according to one of claims 1 to 5.
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