CN117996742A - Modeling method and device for inverter output impedance under finite set model predictive control - Google Patents
Modeling method and device for inverter output impedance under finite set model predictive control Download PDFInfo
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Abstract
The invention discloses a modeling method and a device for inverter output impedance under finite set model predictive control, wherein the method comprises the following steps: determining a transfer function of the phase-locked loop, and establishing a phase-locked loop model; determining a transfer function of the finite set model predictive controller based on a descriptive function method, and establishing a finite set model predictive controller model; determining a transfer function of controllable impedance according to the transfer function of the phase-locked loop and the transfer function of the finite set model predictive controller, and establishing a controllable impedance model; determining a transfer function of the output impedance of the inverter according to the transfer function of the controllable impedance and the transfer function of the filter impedance, and establishing an output impedance model of the inverter; the output impedance of the inverter is formed by connecting the controllable impedance with the filter impedance in parallel. By the method, the effectiveness and the simplicity of modeling of the output impedance of the inverter under the predictive control of the finite set model can be improved.
Description
Technical Field
The invention belongs to the technical field of renewable energy power generation, in particular to an inverter technology, and more particularly relates to a modeling method and device for inverter output impedance under the predictive control of a finite set model.
Background
Renewable energy power generation provides support for sustainable clean utilization of electric energy, and most renewable energy sources are connected to a power grid through a power electronic converter, and the output impedance of the power electronic converter is complex and variable, so that a regional power grid with high renewable energy power generation permeability presents a weak power grid condition. Harmonic interaction between the grid-connected inverter and the power grid is more complex under the condition of weak power grid, and serious stability problems are easy to cause. Harmonic interaction behavior between the inverter and the grid is essentially caused by impedance coupling, and impedance-based analysis and control schemes provide a powerful means for assessing and solving such problems. The stability of the inverter grid-connected system can be determined by analyzing the amplitude and phase relation between the output impedance of the inverter and the impedance of the power grid. In addition, based on the impedance analysis result, the purpose of improving the system stability can be achieved by remolding the output impedance of the inverter.
Modeling technology of inverter output impedance is a particularly critical technology for realizing impedance analysis and impedance remodeling. Most inverter output impedance modeling is based on a harmonic linearization method, which has been widely used in linear control systems. As processor performance advances, more and more nonlinear control methods are applied in power electronic converters and present a number of advantages over linear control methods. Among them, finite set model predictive control (FCS-MPC) has been widely used as one of the most typical ones in grid-connected inverters under various grid conditions including weak grids.
However, the existing harmonic linearization method is not suitable for modeling the output impedance of the inverter under the FCS-MPC, so that the grid-connected inverter under the FCS-MPC is difficult to perform stability analysis and stability improvement research by using an impedance-based method, and the application of the FCS-MPC in the grid-connected inverter is limited to a certain extent. Although the output impedance of the inverter under the FCS-MPC can be obtained by the frequency scanning test method, the frequency scanning process is too complicated, and repeated tests are required when the parameters or the running conditions of the inverter change, so that the complexity of modeling the output impedance of the inverter is further increased.
Disclosure of Invention
The invention aims to provide a modeling method and device for inverter output impedance under finite set model predictive control, and the effectiveness and simplicity of inverter output model modeling are improved.
In order to achieve the above purpose, the modeling method provided by the invention is realized by adopting the following technical scheme:
A modeling method of inverter output impedance under finite set model predictive control includes:
determining a transfer function T PLL(s) of the phase-locked loop, and establishing a phase-locked loop model;
Determining a transfer function DF'(s) of the finite set model predictive controller based on a descriptive function method, and establishing a finite set model predictive controller model;
Determining a transfer function Z invc(s) of controllable impedance according to the transfer function of the phase-locked loop and the transfer function of the finite set model predictive controller, and establishing a controllable impedance model; wherein,
Determining a transfer function Z inv(s) of the output impedance of the inverter according to the transfer function Z invc(s) of the controllable impedance and the transfer function Z f(s) of the filter impedance, and establishing an output impedance model of the inverter; wherein the inverter output impedance is formed by connecting the controllable impedance and the filter impedance in parallel;
determining a transfer function of the finite set model predictive controller based on a descriptive function method, comprising:
determining that the finite set model predictive controller has a description function of DF (f p):
all description function discrete points DF at the set disturbance frequency are obtained:
DF＝[DF(f1),DF(f2),…,DF(fn)]；
Obtaining a fitting function under a set order according to all the discrete points DF of the description function, and determining a transfer function DF'(s) of the finite set model predictive controller;
Where s is the transfer function factor, f p is the disturbance frequency, DF (f p) is the description function of the finite set model predictive controller at f p, A p(fp) is the disturbance current amplitude at f p, A m(fp) is the amplitude of the inverter filter inductor response current at f p, The inverter is filtered for the phase of the inductor response current at f p, f 1、f2、...、fn being the set disturbance frequency.
In some embodiments of the present application, the transfer function T PLL(s) of the phase-locked loop is specifically:
Wherein I ref is a current reference value of the inverter, U pp is a voltage peak value of a grid-connected node of the inverter, ω 0 is a basic angular frequency of a grid voltage of a grid incorporated by the inverter, H PLL is a transfer function of a voltage controller of the phase-locked loop, and k p and k i are a proportional coefficient and an integral coefficient of the voltage controller of the phase-locked loop, respectively.
In some embodiments of the present application, the transfer function Z inv(s) of the output impedance of the inverter is specifically:
Wherein, R f and C f are respectively a damping resistor and a filter capacitor in the filter impedance.
In order to achieve the purpose of the invention, the modeling device provided by the invention is realized by adopting the following technical scheme:
a modeling apparatus for inverter output impedance under finite set model predictive control, comprising:
The phase-locked loop model building unit is used for determining a transfer function T PLL(s) of the phase-locked loop and building a phase-locked loop model;
the finite set model predictive controller model building unit is used for determining a transfer function DF'(s) of the finite set model predictive controller based on a descriptive function method and building a finite set model predictive controller model;
The controllable impedance model building unit is used for determining a transfer function Z invc(s) of controllable impedance according to the transfer function of the phase-locked loop and the transfer function of the finite set model predictive controller, and building a controllable impedance model; wherein,
An inverter output impedance model building unit, configured to determine a transfer function Z inv(s) of the inverter output impedance according to the transfer function Z invc(s) of the controllable impedance and the filter impedance transfer function Z f(s), and build an inverter output impedance model; wherein the inverter output impedance is formed by connecting the controllable impedance and the filter impedance in parallel;
The finite set model predictive controller model establishing unit determines a transfer function of the finite set model predictive controller based on a descriptive function method, and comprises the following steps:
determining that the finite set model predictive controller has a description function of DF (f p):
all description function discrete points DF at the set disturbance frequency are obtained:
DF＝[DF(f1),DF(f2),…,DF(fn)]；
Obtaining a fitting function under a set order according to all the discrete points DF of the description function, and determining a transfer function DF'(s) of the finite set model predictive controller;
Where s is the transfer function factor, f p is the disturbance frequency, DF (f p) is the description function of the finite set model predictive controller at f p, A p(fp) is the disturbance current amplitude at f p, A m(fp) is the amplitude of the inverter filter inductor response current at f p, The inverter is filtered for the phase of the inductor response current at f p, f 1、f2、...、fn being the set disturbance frequency.
In some embodiments of the present application, the transfer function T PLL(s) of the phase-locked loop determined by the phase-locked loop model building unit is specifically:
Wherein I ref is a current reference value of the inverter, U pp is a voltage peak value of a grid-connected node of the inverter, ω 0 is a basic angular frequency of a grid voltage of a grid incorporated by the inverter, H PLL is a transfer function of a voltage controller of the phase-locked loop, and k p and k i are a proportional coefficient and an integral coefficient of the voltage controller of the phase-locked loop, respectively.
In some embodiments of the present application, the transfer function Z inv(s) of the inverter output impedance determined by the inverter output impedance model building unit is specifically:
Wherein, R f and C f are respectively a damping resistor and a filter capacitor in the filter impedance.
Another object of the present invention is to provide a computer device, including a processor, a memory, and a computer program stored on the memory, where the processor is configured to execute the computer program to implement the modeling method of the inverter output impedance under the finite set model predictive control described above.
Still another object of the present invention is to provide a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the modeling method of inverter output impedance under finite set model predictive control described above.
Compared with the prior art, the invention has the advantages and positive effects that:
According to the modeling method and device for the output impedance of the inverter under the finite set model predictive control, the transfer function of the finite set model predictive controller is determined based on the descriptive function method, the phase-locked loop transfer function and the filter impedance transfer function are combined, the transfer function of the output impedance of the inverter is determined, the inverter output impedance model is built based on the transfer function, the determined output impedance model is highly consistent with the frequency scanning result, the behavior characteristics of the output impedance of the inverter under the finite set model predictive control can be accurately described, feasibility and effectiveness of modeling of the output impedance of the inverter under the finite set model predictive control are realized, the influence of each parameter on the output impedance is conveniently analyzed, and basis are provided for analyzing the harmonic interaction problem between the grid-connected inverter and the weak current network under the finite set model predictive control based on the impedance method; in addition, compared with the impedance model building method based on frequency scanning, when the inverter parameters or the running conditions change, repeated modeling is not needed, the inverter output impedance modeling process is simplified, and the modeling simplicity and the easy realization are improved.
Other features and advantages of the present invention will become apparent upon review of the detailed description of the invention in conjunction with the drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of one embodiment of an inverter grid-tie system under finite set model predictive control of the present invention;
FIG. 2 is a schematic diagram of an equivalent model of the inverter grid-tie system of FIG. 1;
FIG. 3 is a schematic diagram of an inverter system impedance model corresponding to FIG. 2;
FIG. 4 is a flow chart of one embodiment of a modeling method for inverter output impedance under finite set model predictive control according to the present invention;
FIG. 5 is a schematic diagram of an embodiment of a modeling apparatus for inverter output impedance under finite set model predictive control according to the present invention;
FIG. 6 is a graph of amplitude frequency characteristics and simulation data for a finite set model predictive controller with different current references;
FIG. 7 is a schematic diagram of the phase frequency characteristic curve and simulation data of the finite set model predictive controller for different current references;
FIG. 8 is a graph of amplitude versus frequency characteristics and simulation data for a finite set model predictive controller with different inductance parameters;
FIG. 9 is a schematic diagram of the phase frequency characteristic curves and simulation data of the finite set model predictive controller under different inductance parameters;
FIG. 10 is a graph of amplitude frequency characteristics and simulation data of an inverter output impedance model constructed based on the modeling method of FIG. 4;
Fig. 11 is a schematic diagram of a phase frequency characteristic curve and simulation data of an inverter output impedance model established based on the modeling method of fig. 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples.
Fig. 1 is a block diagram of an embodiment of an inverter grid-connected system under the prediction control of a finite set model, specifically, a block diagram of an inverter grid-connected system under the prediction control of a current-type finite set model.
In fig. 1, L f is a filter inductor, R f and C f are a damping resistor and a filter capacitor, respectively, S i is a switching vector, V dc is a dc input voltage, Z g is a grid impedance, PCC is a grid-connected node, I fabc is a filter inductor current, u pabc is a PCC voltage, I f is a filter inductor current after Clarke conversion, u p is a PCC voltage after Clarke conversion, I ref is a current reference value of an inverter, and I r is a current reference signal in an αβ coordinate system. The sampled current i fabc and the sampled voltage u pabc from the main circuit are converted into a current i f and a voltage u p by Clarke conversion, and the current i f and the voltage u p enter the finite set model predictive controller FCS-MPC together with the current reference signal i r. The FCS-MPC executes a predictive control algorithm to complete closed-loop control of the filter inductor current.
Fig. 2 shows a schematic diagram of an equivalent model of the inverter grid-tie system of fig. 1 in the αβ coordinate system. As shown in fig. 2, the inverter is equivalently a controllable current source, and the phase-locked loop PLL and the finite set model predictive controller FCS-MPC together form a control loop of the controllable current source. In addition, the control loop of the controllable current source takes the PCC voltage u p as input, the filter inductance current I f as output and the current reference value I ref as disturbance, and has the behavior characteristic similar to impedance, so that the control loop of the inverter can be equivalent to a controllable impedance controlled by the current reference value I ref.
Fig. 3 shows a schematic diagram of an impedance model of the inverter system corresponding to fig. 2. In fig. 3, Z invc is a controllable impedance, Z f is a filter impedance formed by R f、Cf, and the inverter output impedance Z inv is formed by two parts, namely a controllable impedance Z invc and a filter impedance Z f.
Based on the analysis, the invention provides a modeling method for the output impedance of the inverter under the predictive control of the finite set model.
Specifically, fig. 4 is a schematic flow chart of an embodiment of a modeling method of the output impedance of the inverter under the prediction control of the finite set model according to the present invention. This embodiment builds an inverter output impedance model using the following procedure.
S11: and determining a transfer function of the phase-locked loop, and establishing a phase-locked loop model.
The determination of the transfer function of the phase-locked loop is implemented using prior art techniques. After determining the phase-locked loop transfer function, a corresponding phase-locked loop model may be established.
In some embodiments, the transfer function T PLL(s) of the phase-locked loop is specifically:
Referring to fig. 1 to 3, s is a transfer function factor, I ref is a current reference value of the inverter, and is a known value; u pp is the voltage peak value of the grid-connected node of the inverter and is a measurable value; omega 0 is the basic angular frequency of the grid voltage of the grid into which the inverter is incorporated, and is a known value; h PLL is the transfer function of the voltage controller of the phase-locked loop, and k p and k i are the proportional coefficient and the integral coefficient, respectively, of the voltage controller of the phase-locked loop, which are known values.
S12: and determining a transfer function of the finite set model predictive controller based on a descriptive function method, and establishing a finite set model predictive controller model.
Because the finite set model predictive controller is a nonlinear controller, the transfer function of the control loop cannot be directly deduced. Thus, this embodiment uses a descriptive function to determine its transfer function. Specifically, after the sinusoidal disturbance current signals with different disturbance frequencies f p are superimposed on the current reference signal i r, the sinusoidal disturbance current signals are input as input signals to a finite set model predictive controller, and after the finite set model predictive controller controls the inverter, the amplitude A m(fp) and the phase of the inverter filter inductance response current at the disturbance frequency f p can be obtainedFurther, it can be determined that the finite set model predictive controller has a description function of DF (f p):
then, all description function discrete points DF at the set disturbance frequency are obtained:
DF＝[DF(f1),DF(f2),…,DF(fn)]。
finally, setting the order of the curve to be fitted, and performing curve fitting on all the discrete points DF of the description function under the set order to obtain a fitting function, wherein the fitting function is determined as the transfer function DF'(s) of the finite set model predictive controller.
Where DF (f p) is the descriptive function of the finite set model predictive controller at f p, A p(fp) is the disturbance current magnitude at f p, is a known value, A m(fp) is the magnitude of the inverter filter inductor response current at f p,The phase of the filter inductance response current of the inverter at f p is a measurable value, and f 1、f2、...、fn is a set disturbance frequency.
In some embodiments, the set disturbance frequency may be a sampling value within a set disturbance frequency range, and the set disturbance frequency range and the specific sampling value may be set as desired.
In some embodiments, the setting order of the fitting function may be selected according to the actual requirement.
S13: and determining the transfer function of the controllable impedance according to the transfer function of the phase-locked loop and the transfer function of the finite set model predictive controller, and establishing a controllable impedance model.
The transfer function of the controllable impedance is denoted as Z invc(s), which is expressed as:
S14: and determining the transfer function of the output impedance of the inverter according to the transfer function of the controllable impedance and the transfer function of the filter impedance, and establishing an output impedance model of the inverter.
As described above, the inverter output impedance is formed by connecting the controllable impedance and the filter impedance in parallel, and the transfer function of the inverter output impedance is denoted as Z inv(s), then Z inv(s) can be expressed as: z inv(s)＝Zinvc(s)||Zf(s). Wherein Z f(s) is the filter impedance transfer function,
In some embodiments, the transfer function Z inv(s) of the inverter output impedance is specifically:
By adopting the method of the embodiment, the transfer function of the finite set model predictive controller is determined based on the descriptive function method, then the transfer function of the inverter output impedance is determined by combining the phase-locked loop transfer function and the filter impedance transfer function, and then the inverter output impedance model is established based on the transfer function, and the determined output impedance model is highly consistent with the frequency scanning result, so that the behavior characteristics of the inverter output impedance under the finite set model predictive control can be accurately described, the feasibility and the effectiveness of the inverter output impedance modeling under the finite set model predictive control are realized, the influence of each parameter on the output impedance is conveniently analyzed, and the basis are provided for analyzing the harmonic interaction problem between the grid-connected inverter and the weak grid under the finite set model predictive control based on the impedance method; in addition, compared with the impedance model building method based on frequency scanning, when the inverter parameters or the running conditions change, repeated modeling is not needed, the inverter output impedance modeling process is simplified, and the modeling simplicity and the easy realization are improved.
FIG. 5 is a schematic diagram of an embodiment of a modeling apparatus for inverter output impedance under finite set model predictive control according to the present invention.
As shown in fig. 5, the modeling apparatus of this embodiment includes structural units, connection relationships between the structural units, and functions, which are described as follows:
The modeling apparatus includes:
The phase-locked loop model building unit 21 is configured to determine a transfer function T PLL(s) of the phase-locked loop, and build a phase-locked loop model.
The finite set model predictive controller model establishing unit 22 is used for determining a transfer function DF'(s) of the finite set model predictive controller based on a descriptive function method and establishing a finite set model predictive controller model.
The controllable impedance model building unit 23 is configured to build a controllable impedance model according to the phase-locked loop transfer function determined by the phase-locked loop model building unit 21 and the transfer function Z invc(s) of the finite set model predictive controller determined by the finite set model predictive controller model building unit 22.
An inverter output impedance model building unit 24 for building an inverter output impedance model by determining a transfer function Z inv(s) of the inverter output impedance from the transfer function Z invc(s) of the controllable impedance determined by the controllable impedance model building unit 23 and the filter impedance transfer function Z f(s). The output impedance of the inverter is formed by connecting controllable impedance and filter impedance in parallel.
The modeling device with the structure runs corresponding software programs, realizes modeling of the inverter output impedance under the prediction control of the finite set model according to the modeling method of the embodiment of fig. 4 and other embodiments, and achieves the technical effect corresponding to the modeling method.
Some embodiments of the present application also provide a computer device, which includes a processor, a memory, and a computer program stored on the memory, where the processor is configured to execute the computer program, implement the modeling method of the embodiment of fig. 4 and other embodiments, implement modeling of the output impedance of the inverter under the predictive control of the finite set model, and achieve a technical effect corresponding to the modeling method.
Other embodiments of the present invention further provide a computer storage medium, on which a computer program is stored, which when executed by a processor, implements the modeling method of the embodiment of fig. 4 and other embodiments, implements modeling of the output impedance of the inverter under the predictive control of the finite set model, and achieves a technical effect corresponding to the modeling method.
The effectiveness of the modeling method of the present invention is further described below based on a simulation example.
In this simulation example, the inverter parameters are shown in table 1 below.
Table 1 inverter parameters
Based on the inverter parameters in table 1, when the set order is the fourth order, determining the transfer function of the finite set model predictive controller by using the descriptive function method is as follows:
And frequency testing is carried out on the frequency response of the finite set model predictive controller in simulation software, and the test result is compared with the transfer function of the finite set model predictive controller.
Fig. 6 shows an amplitude frequency characteristic curve and a simulation data diagram of the finite-set model predictive controller under different current reference values, and fig. 7 shows a phase frequency characteristic curve and a simulation data diagram of the finite-set model predictive controller under different current reference values. As can be seen from the graph, when the current reference values are 3A and 10A, the simulation data are highly matched with the transfer function curve, so that the transfer function has stronger robustness to the change of the current reference value of the inverter. Therefore, when the current reference value changes, the modeling process of the finite set model predictive controller does not need to be repeated.
Fig. 8 shows amplitude frequency characteristic curves and simulation data diagrams of finite set model predictive controllers under different inductance parameters, and fig. 9 shows phase frequency characteristic curves and simulation data diagrams of finite set model predictive controllers under different inductance parameters. From the graph, when the filter inductance value of the inverter changes by 10-30%, the amplitude deviation between the simulation data and the transfer function curve is within 2dB, and the phase deviation is within 15 degrees, which shows that the transfer function has stronger robustness to the change of the inductance parameter of the inverter. When the inductance parameter changes, the modeling process of the finite set model predictive controller does not need to be repeated.
The above simulation analysis shows that it is effective to predict the transfer function of the controller based on the finite set model determined by the descriptive function method.
And performing frequency scanning test on the frequency response of the inverter output impedance in simulation software, and comparing the test result with an inverter output impedance model established based on the modeling method provided by the invention.
Fig. 10 is a schematic diagram of amplitude frequency characteristic curves and simulation data of an inverter output impedance model established based on the modeling method of fig. 4, and fig. 11 is a schematic diagram of phase frequency characteristic curves and simulation data of an inverter output impedance model established based on the modeling method of fig. 4. As can be seen from the figure, the inverter output impedance model curve established based on the modeling method of fig. 4 is highly consistent with the simulation data, which indicates that the modeling method provided by the invention is effective and feasible.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be apparent to one skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (8)
1. A modeling method for inverter output impedance under finite set model predictive control, the method comprising:
determining a transfer function T PLL(s) of the phase-locked loop, and establishing a phase-locked loop model;
Determining a transfer function DF'(s) of the finite set model predictive controller based on a descriptive function method, and establishing a finite set model predictive controller model;
Determining a transfer function Z invc(s) of controllable impedance according to the transfer function of the phase-locked loop and the transfer function of the finite set model predictive controller, and establishing a controllable impedance model; wherein,
Determining a transfer function Z inv(s) of the output impedance of the inverter according to the transfer function Z invc(s) of the controllable impedance and the transfer function Z f(s) of the filter impedance, and establishing an output impedance model of the inverter; wherein the inverter output impedance is formed by connecting the controllable impedance and the filter impedance in parallel;
determining a transfer function of the finite set model predictive controller based on a descriptive function method, comprising:
determining that the finite set model predictive controller has a description function of DF (f p):
all description function discrete points DF at the set disturbance frequency are obtained:
DF＝[DF(f1),DF(f2),…,DF(fn)]；
Obtaining a fitting function under a set order according to all the discrete points DF of the description function, and determining a transfer function DF'(s) of the finite set model predictive controller;
Where s is the transfer function factor, f p is the disturbance frequency, DF (f p) is the description function of the finite set model predictive controller at f p, A p(fp) is the disturbance current amplitude at f p, A m(fp) is the amplitude of the inverter filter inductor response current at f p, The inverter is filtered for the phase of the inductor response current at f p, f 1、f2、...、fn being the set disturbance frequency.
2. The modeling method of inverter output impedance under finite set model predictive control according to claim 1, wherein the transfer function T PLL(s) of the phase-locked loop is specifically:
Wherein I ref is a current reference value of the inverter, U pp is a voltage peak value of a grid-connected node of the inverter, ω 0 is a basic angular frequency of a grid voltage of a grid incorporated by the inverter, H PLL is a transfer function of a voltage controller of the phase-locked loop, and k p and k i are a proportional coefficient and an integral coefficient of the voltage controller of the phase-locked loop, respectively.
3. The modeling method of inverter output impedance under finite set model predictive control according to claim 2, wherein the transfer function Z inv(s) of inverter output impedance is specifically:
Wherein, R f and C f are respectively a damping resistor and a filter capacitor in the filter impedance.
4. A modeling apparatus for inverter output impedance under finite set model predictive control, the apparatus comprising:
The phase-locked loop model building unit is used for determining a transfer function T PLL(s) of the phase-locked loop and building a phase-locked loop model;
the finite set model predictive controller model building unit is used for determining a transfer function DF'(s) of the finite set model predictive controller based on a descriptive function method and building a finite set model predictive controller model;
The controllable impedance model building unit is used for determining a transfer function Z invc(s) of controllable impedance according to the transfer function of the phase-locked loop and the transfer function of the finite set model predictive controller, and building a controllable impedance model; wherein,
An inverter output impedance model building unit, configured to determine a transfer function Z inv(s) of the inverter output impedance according to the transfer function Z invc(s) of the controllable impedance and the filter impedance transfer function Z f(s), and build an inverter output impedance model; wherein the inverter output impedance is formed by connecting the controllable impedance and the filter impedance in parallel;
The finite set model predictive controller model establishing unit determines a transfer function of the finite set model predictive controller based on a descriptive function method, and comprises the following steps:
determining that the finite set model predictive controller has a description function of DF (f p):
all description function discrete points DF at the set disturbance frequency are obtained:
DF＝[DF(f1),DF(f2),…,DF(fn)]；
Obtaining a fitting function under a set order according to all the discrete points DF of the description function, and determining a transfer function DF'(s) of the finite set model predictive controller;
Where s is the transfer function factor, f p is the disturbance frequency, DF (f p) is the description function of the finite set model predictive controller at f p, A p(fp) is the disturbance current amplitude at f p, A m(fp) is the amplitude of the inverter filter inductor response current at f p, The inverter is filtered for the phase of the inductor response current at f p, f 1、f2、...、fn being the set disturbance frequency.
5. The modeling apparatus for inverter output impedance under finite set model predictive control as claimed in claim 4, wherein the transfer function T PLL(s) of the phase-locked loop determined by the phase-locked loop model building unit is specifically:
Wherein I ref is a current reference value of the inverter, U pp is a voltage peak value of a grid-connected node of the inverter, ω 0 is a basic angular frequency of a grid voltage of a grid incorporated by the inverter, H PLL is a transfer function of a voltage controller of the phase-locked loop, and k p and k i are a proportional coefficient and an integral coefficient of the voltage controller of the phase-locked loop, respectively.
6. The modeling apparatus for inverter output impedance under finite set model predictive control according to claim 5, wherein the transfer function Z inv(s) of the inverter output impedance determined by the inverter output impedance model building unit is specifically:
Wherein, R f and C f are respectively a damping resistor and a filter capacitor in the filter impedance.
7. A computer device comprising a processor, a memory and a computer program stored on the memory, characterized in that the processor is configured to execute the computer program to implement a method of modeling the output impedance of an inverter under the finite set model predictive control of any of the preceding claims 1-3.
8. A computer readable storage medium having stored thereon a computer program, which when executed by a processor, implements a method of modeling inverter output impedance under finite set model predictive control as claimed in any one of the preceding claims 1-3.
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