CN114977302A - Small signal equivalent modeling method and system for new energy grid-connected inverter - Google Patents
Small signal equivalent modeling method and system for new energy grid-connected inverter Download PDFInfo
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
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Abstract
The invention relates to a small signal equivalent modeling method and system for a new energy grid-connected inverter, which comprises the following steps: obtaining an impedance transfer function from output current to grid-connected point voltage of a single inverter under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model; determining an inverter coherence criterion based on the impedance transfer function, calculating the difference degree of amplitude-frequency characteristics of n inverters, and performing coherence grouping on the n inverters; and calculating the aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system, and performing simulation analysis on the multi-inverter system of the new energy station. The invention provides a practical inverter coherence criterion, realizes equivalent order reduction of a multi-inverter grid-connected system, greatly simplifies a multi-inverter grid-connected system model and improves simulation speed on the premise of ensuring simulation precision, and can be widely applied to the technical field of power electronics.
Description
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a frequency domain transfer function-based small signal equivalent modeling method and system for a new energy grid-connected inverter.
Background
With the rapid development of new energy power generation grid-connected technology, the permeability of a grid-connected inverter serving as an important interface of new energy grid connection in a power system is continuously improved. The grid-connected inverters in large-scale wind power plants and photovoltaic power stations are large in number and complex in control mode, and if each new energy grid-connected inverter is subjected to detailed modeling, the complexity of simulation analysis is greatly increased. The problem can be well solved by a model which can accurately represent the overall dynamic characteristics of the system and is equivalent and simplified.
At present, two main types of dynamic equivalent modeling methods of a new energy station are a reduced order method and a dynamic polymerization method. The order reduction method generally adopts a mathematical method or a system theory, in order to reduce the order of the whole model of the new energy station, a detailed system differential equation needs to be reduced and simplified, but the order reduction method can omit some state variables of the system aiming at different analysis problems, and the original physical structure of the new energy grid-connected inverter is damaged.
The dynamic polymerization method is divided into single-machine polymerization and multi-machine polymerization, and is a more common method. The single-machine aggregation enables the whole new energy station to be equivalent to one machine set, and large errors can be generated. The multi-machine aggregation is performed by grouping first and then polymerizing, the selection of grouping criteria can obviously influence the errors before and after equivalence, most of the existing multi-machine aggregation methods are divided according to simple indexes such as the type, the operation mode, the installation position and the like of a new energy unit, and therefore the accuracy difference of the equivalent model obtained by the existing equivalent method under different external environment conditions is large.
Disclosure of Invention
In view of the above problems, the invention aims to provide a small-signal equivalent modeling method and system for a new energy grid-connected inverter, which start from a grid-connected inverter linearization model to perform equivalent aggregation on the system, improve the accuracy of a multi-machine aggregation model, and improve the efficiency of simulation operation.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a small signal equivalent modeling method for a new energy grid-connected inverter, which comprises the following steps:
obtaining an impedance transfer function from output current to grid-connected point voltage of a single inverter under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model;
determining an inverter coherence criterion based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of the n inverters, and performing coherence grouping on the n inverters;
and calculating the aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system, and performing simulation analysis on the multi-inverter system of the new energy station.
Further, the method for obtaining the impedance transfer function from the output current to the grid-connected point voltage of the single inverter under the unified coordinate system based on the established new energy grid-connected inverter linearization mathematical model comprises the following steps:
establishing a mathematical model of the new energy grid-connected inverter;
linearizing the mathematical model to obtain the relation between grid-connected point voltage and grid-connected inverter output current of a single inverter under a dq synchronous rotation coordinate system;
and selecting an infinite power grid as a unified coordinate system, and converting the relation between the grid-connected point voltage and the inverter output current of the single inverter under the dq synchronous rotation coordinate system into the unified coordinate system.
Further, the method for determining the coherence criterion of the inverters based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of the n inverters, and performing coherence grouping on the n inverters comprises the following steps:
establishing inverter coherence criterion based on a frequency domain transfer function;
simplifying the inverter coherence criterion based on the amplitude-frequency characteristic of the impedance transfer function to obtain the impedance transfer function Z xx Practical criteria of amplitude-frequency characteristic response;
defining the difference degree of the inverter according to the practical coherence criterion;
and sequentially calculating the difference degree of every two inverters, and carrying out coherence discrimination and grouping on the inverters according to the difference degree and the selected allowable error.
Further, the inverter has a difference degree of:
ε ij ＝|G i (Z xxi (s))-G j (Z xxj (s))|
in the formula, epsilon ij Is the degree of disparity of the inverters; z xxi (s) and Z xxj And(s) are impedance transfer functions of the variation of the x-axis output current of the ith inverter and the jth inverter to the variation of the x-axis grid-connected point voltage in a unified coordinate system respectively.
Further, when calculating the aggregation parameter of the inverters in each coherent group based on the grouping result of the inverters, the method includes: the method comprises the steps of circuit structure parameter aggregation and control system parameter aggregation, wherein the control system parameter aggregation comprises the phase-locked loop control parameter aggregation and the current loop control parameter aggregation.
Further, the aggregation of the circuit structure parameters is as follows:
L f,eq ＝L f1 //L f2 //…//L fn
in the formula, L f,eq Filter inductance, L, being an equivalent model f1 、L f2 、……L fn Respectively showing the filter inductance of the 1 st to the nth grid-connected inverters in a certain coordination group.
Further, the method for aggregating the control parameters of the phase-locked loop comprises the following steps:
in the formula, k pPLL,eq And k iPLL,eq The proportional coefficient and the integral coefficient of the phase-locked loop of the equivalent system are respectively; k is a radical of pPLLi And k iPLLi Proportional coefficient and integral coefficient of the ith inverter phase-locked loop, c i The weighting coefficient of the ith inverter;
the polymerization method of the current loop control parameters comprises the following steps:
in the formula, k pi,eq And k ii,eq Respectively is a current loop proportional coefficient and an integral coefficient of an equivalent system; k is a radical of pij And k iij Proportional and integral coefficients, c, of the jth inverter current loop, respectively j Is the weight coefficient of the jth inverter.
In a second aspect, the invention provides a small signal equivalent modeling system for a new energy grid-connected inverter, which includes:
the impedance transfer function determining module is used for obtaining an impedance transfer function from output current to grid-connected point voltage of a single inverter under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model;
the system comprises a coherence grouping module, a sampling module and a sampling module, wherein the coherence grouping module is used for determining a coherence criterion of the inverters based on an impedance transfer function, calculating the difference degree of amplitude-frequency characteristics of n inverters and performing coherence grouping on the n inverters;
and the aggregation parameter calculation module is used for calculating aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system, and performing simulation analysis on the multi-inverter system of the new energy station.
In a third aspect, the invention provides a processing device, which at least includes a processor and a memory, where the memory stores a computer program, and the processor executes the computer program when running the computer program to implement the steps of the new energy grid-connected inverter small signal equivalence modeling method.
In a fourth aspect, the present invention provides a computer storage medium having computer readable instructions stored thereon, the computer readable instructions being executable by a processor to implement the steps of the small-signal equivalence modeling method according to the new energy grid-connected inverter.
Due to the adoption of the technical scheme, the invention has the following advantages: the invention performs coherent grouping on the multi-inverter grid-connected system through the coherent criterion based on the inverter frequency domain transfer function, overcomes the defect of larger equivalent error of the traditional single machine, overcomes the defect that the existing multi-machine coherent criterion depends on the measured data of the new energy station, performs equivalent aggregation on the system from the inverter linearization model, improves the accuracy of the multi-machine aggregation model, and improves the efficiency of simulation operation. Therefore, the method can be widely applied to the technical field of power electronics.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Like reference numerals refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a flow chart of a new energy grid-connected inverter small signal equivalent modeling method in the invention;
FIG. 2 is a schematic diagram of a single inverter structure and control system according to the present invention;
FIG. 3 is a schematic diagram of the relationship between each inverter and a unified coordinate system according to the present invention;
fig. 4 is a structural diagram of a 5 new energy grid-connected inverter system according to an embodiment of the present invention;
FIG. 5 is a graph of the amplitude-frequency characteristic of the impedance transfer function Zxx for 5 inverters of the present invention;
FIG. 6 is a comparison of the active power waveforms before and after clustering according to the frequency domain transfer function coherence criterion;
fig. 7 is a comparison diagram of active power waveforms before and after single-machine equivalence is performed on 5 new energy grid-connected inverters in the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
When large-scale new energy (wind power and photovoltaic) stations are modeled and analyzed, due to the fact that the number of new energy grid-connected inverters is large and the control mode is complex, if each power generation unit in the whole system is modeled in detail, the system order is too high, dimension disaster is easily caused, and the difficulty of simulation analysis is greatly increased.
The invention provides a new energy grid-connected inverter small signal equivalent modeling method based on a frequency domain transfer function, aiming at overcoming the defects of the existing new energy inverter dynamic equivalent modeling method, a grouping index does not depend on real data in the actual operation of an inverter, and equivalent aggregation is carried out on a multi-inverter grid-connected system from a grid-connected inverter linear model, so that the accuracy of a multi-machine aggregation model is improved, the order of the model is effectively reduced on the premise of ensuring the accuracy of the equivalent model, and the simulation operation time of the multi-inverter grid-connected system is shortened.
Correspondingly, in other embodiments of the invention, a new energy grid-connected inverter small signal equivalent modeling system, equipment and medium are also provided.
Example 1
As shown in fig. 1, the embodiment provides a small-signal equivalent modeling method for a new energy grid-connected inverter, and provides a grid-connected inverter coherence criterion based on a frequency domain transfer function from a new energy grid-connected inverter linearization model, without depending on monitoring data of the grid-connected inverter in actual grid-connected operation, so that the order of the system is effectively reduced, and the method has the advantages of simplicity, practicality, high model precision and the like. Specifically, the method comprises the following steps:
step 1: and obtaining an impedance transfer function from the output current of the single inverter to the voltage of the grid-connected point under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model.
Specifically, the step 1 can be implemented by the following steps:
step 1.1: and establishing a mathematical model of the new energy grid-connected inverter.
Fig. 2 is a schematic diagram of a single inverter structure and a control system. The mathematical model comprises a phase-locked loop, a current loop controlled grid-connected inverter, a filter and a weak power grid. Wherein L is f Is a filter inductor, L g Is a weak grid equivalent inductance, G pll And H i PI controllers of a phase-locked loop and a current loop respectively; i is dref And I qref Reference values, U, are respectively given for d-axis and q-axis currents of the current loop dref And U qref And d-axis and q-axis voltage reference values are output by the current loop respectively.
Step 1.2: and linearizing the mathematical model to obtain the relation between the grid-connected point voltage and the output current of the grid-connected inverter of a single inverter under the dq synchronous rotation coordinate system.
Specifically, linearizing the mathematical model, that is, applying a small disturbance increment at a balance point of the mathematical model of the system, neglecting a high-order term increment, and obtaining a relation between a grid-connected point voltage and an inverter output current in a dq synchronous rotation coordinate system, which is expressed as:
in equation (1), all variables are based on the dq synchronous rotation coordinate system of each inverter, Δ u pccd And Δ u pccq Respectively representing the variation of the grid-connected point voltage under the dq synchronous rotation coordinate system; Δ i d And Δ i q Respectively representing the variable quantity of the inverter output current under the dq synchronous rotation coordinate system; z dd (s)、Z qd (s)、Z dq (s) and Z qq (s) are the four impedance transfer functions in the dq synchronous rotation coordinate system.
Step 1.3: and (3) selecting an infinite power grid as a unified coordinate system, and converting the relation between the grid-connected point voltage of the single inverter obtained in the step (1.2) and the output current of the inverter in the dq synchronous rotation coordinate system into the unified coordinate system.
As shown in fig. 3, a schematic diagram of coordinate transformation is shown, and the coordinate transformation relationship is:
in the formula (f) di And f qi The grid-connected point voltage or the inverter current of the ith inverter under the dq coordinate system of the ith inverter; f. of xi And f yi The grid-connected point voltage or the inverter current of the ith inverter under the unified coordinate system; theta.theta. i And the phase angle difference between the dq coordinate system of the ith inverter and the unified coordinate system is obtained.
Linearizing equation (2) to yield:
in the formula,. DELTA.f di And Δ f qi The grid-connected point voltage or the inverter current variation of the ith inverter in the dq coordinate system of the ith inverter; Δ f xi And Δ f yi The variation of the grid-connected point voltage or the inverter current of the ith inverter in a unified coordinate system; theta i0 The phase angle difference between the dq coordinate system of the ith inverter and the unified coordinate system at a steady-state working point; f. of qi0 And f di0 And respectively, the steady-state working point of the grid-connected point voltage or the inverter current of the ith inverter in the dq coordinate system of the ith inverter.
Combining formula (1) and formula (3) gives:
in the formula (4), the coordinate systems are all based on the selected unified coordinate system, and Δ u pccx And Δ u pccy Respectively representing the variation of the grid-connected point voltage under the unified coordinate system; delta i xi And Δ i yi Respectively representing the variable quantity of the inverter output current under the unified coordinate system; z xx (s)、Z yx (s)、Z xy (s) and Z yy (s) are four impedance transfer functions in the same coordinate system.
Step 2: and determining the coherence criterion of the inverters based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of the n inverters, and performing coherence grouping on the n inverters.
As shown in fig. 3, the implementation flow of the coherent equivalence modeling method in the present invention includes the following steps:
step 2.1: and establishing inverter coherence criterion based on the frequency domain transfer function.
If the difference between the amplitude-frequency characteristic response and the phase-frequency characteristic response of the frequency domain transfer functions of the two inverters is not greater than the tolerance delta in the whole frequency range (i.e. the wide frequency band range including the power frequency), the two grid-connected inverters can be judged to be in the same tone, and the expression is as follows:
wherein, | G 1 (s) | and | G 2 (s) | represents the amplitude-frequency characteristics of the two inverters respectively, and angle G 1 (s) and ≈ G 2 (s) respectively represent phase frequency characteristics; delta 1 And delta 2 Respectively representing the allowable errors corresponding to the amplitude-frequency characteristic and the phase-frequency characteristic.
Step 2.2: simplifying the inverter coherence criterion of the step 2.1 based on the amplitude-frequency characteristic of the impedance transfer function to obtain the impedance transfer function Z xx The practical criterion of the amplitude-frequency characteristic response.
From the above, the linearized mathematical model for each inverter is a 2 x 2 matrix, Z xx (s)、Z xy (s)、Z yx (s)、Z yy And(s) respectively corresponding to the four transfer functions, and if the four transfer functions of the two inverters all meet the given criterion formula, the inverters are strictly in coherence. However, if the amplitude-frequency characteristic curve of each transfer function is determined, the workload of coherent determination is greatly increased. Therefore, in order to make the coherence criterion practical, the embodiment selects one of the transfer functions Z xx (s); i.e. the impedance transfer function Z of two grid-connected inverters xx The amplitude-frequency characteristic curve is not more than a given error delta under any frequency, and the two grid-connected inverters can be judged to be in the same phase, namely
||G 1 (s)|-|G 2 (s)||≤δ (6)
In the formula, δ is an allowable error corresponding to the amplitude-frequency characteristics of the two inverters.
Step 2.3: and (3) defining the difference degree of the inverter according to the practical coherence criterion obtained in the step 2.2:
ε ij ＝|G i (Z xxi (s))-G j (Z xxj (s))| (7)
in the formula, epsilon ij Is the degree of disparity of the inverters; z xxi (s) and Z xxj (s) are respectively the ith coordinate systemImpedance transfer functions of x-axis output current variation of the stage inverter and the jth stage inverter to x-axis grid-connected point voltage variation.
Step 2.4: and sequentially calculating the difference degree of every two inverters, and carrying out coherence discrimination and grouping on the inverters according to the difference degree and the selected allowable error.
And step 3: and calculating the aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system so as to perform simulation analysis on the multi-inverter system of the new energy station.
The aggregation parameters comprise aggregation of circuit structure parameters and aggregation of control system parameters, and the aggregation of the control system parameters comprises aggregation of phase-locked loop control parameters and aggregation of current loop control parameters.
Specifically, the polymerization method of each parameter is as follows:
step 3.1: the method for aggregating the circuit structure parameters comprises the following steps:
L f,eq ＝L f1 //L f2 //…//L fn (8)
in the formula, L f,eq Filter inductance, L, being an equivalent model f1 、L f2 、……L fn Respectively showing the filter inductance of the 1 st to the nth grid-connected inverters in a certain homodyne group.
Step 3.2: the method for polymerizing the control parameters of the phase-locked loop comprises the following steps:
in the formula, k pPLL,eq And k iPLL,eq The proportional coefficient and the integral coefficient of the phase-locked loop of the equivalent system are respectively; k is a radical of pPLLi And k iPLLi Proportional coefficient and integral coefficient of the ith inverter phase-locked loop, c i The weight coefficient of the ith inverter is equivalent to the d-axis current reference value of the ith inverter in the invention.
Step 3.3: the polymerization method of the current loop control parameters comprises the following steps:
in the formula, k pi,eq And k ii,eq Respectively is a current loop proportional coefficient and an integral coefficient of an equivalent system; k is a radical of formula pij And k iij Proportional coefficient and integral coefficient of the j inverter phase-locked loop, c j The weight coefficient of the j inverter is equivalent to the d-axis current reference value of the j inverter in the invention, and n is the number of inverters in the same coherent group.
Example 2
In this embodiment, the invention is further described by taking 5 new energy grid-connected inverter systems shown in fig. 4 as an example.
Firstly, establishing dq impedance transfer function of each grid-connected inverter under a unified coordinate system, and drawing 5 grid-connected inverter impedances Z xx The amplitude-frequency characteristic curve of (2) is shown in fig. 5.
Then, the difference degree between every two inverters is calculated according to the difference degree defined in the present invention, and the calculation result of the difference degree is shown in table 1.
TABLE 1 calculation of the degree of difference
| No. | 1 | 2 | 3 | 4 | 5 |
| 1 | 0 | 6.0210 | 9.5433 | 8.0807 | 12.0418 |
| 2 | — | 0 | 7.5258 | 4.0035 | 8.3903 |
| 3 | — | — | 0 | 3.5235 | 2.4991 |
| 4 | — | — | — | 0 | 6.2015 |
| 5 | — | — | — | — | 0 |
If the selected allowable error is 5dB, it can be seen from table 1 that the difference between the number 2 and 4 grid-connected inverters is small, and the difference between the number 3, 4 and 5 grid-connected inverters is small, so that the obtained grouping result is that the number 2-5 is a coherent group. However, it is observed from table 1 that the differences between the grid-connected inverters nos. 4 and 5 are large, and in order to ensure the rigor of the grouping result, the grid-connected inverters nos. 2 and 4 are divided into coherent groups, and the grid-connected inverters nos. 3 and 5 are divided into coherent groups. Therefore, in the embodiment, 5 grid-connected inverters are divided into 3 coherent groups which are 1 respectively; 2 and 4; 3 and 5.
FIG. 6 is a comparison diagram of the active power of an equivalent model and the active power of a detailed model obtained by aggregation according to the equivalent modeling method, FIG. 7 is a comparison diagram of a single-machine equivalent method and the active power of the detailed model, FIG. 6 shows that the dynamic response of the equivalent model obtained by clustering and aggregation of the coherence criteria provided by the invention is basically completely consistent with that of the detailed model, FIG. 7 shows that the dynamic process of the single-machine equivalent model cannot be consistent with that of the detailed model, and the comparison between FIG. 6 and FIG. 7 verifies the effectiveness of the equivalent modeling method provided by the invention.
Example 3
The embodiment 1 provides a new energy grid-connected inverter small signal equivalent modeling method, and correspondingly, the embodiment provides a new energy grid-connected inverter small signal equivalent modeling system. The system provided by the embodiment can implement the new energy grid-connected inverter small signal equivalent modeling method of embodiment 1, and the system can be implemented through software, hardware or a combination of software and hardware. For example, the system may comprise integrated or separate functional modules or functional units to perform the corresponding steps in the methods of embodiment 1. Since the system of this embodiment is substantially similar to the method embodiment, the description process of this embodiment is relatively simple, and reference may be made to part of the description of embodiment 1 for relevant points.
The small-signal equivalent modeling system for the new energy grid-connected inverter provided by the embodiment comprises:
the impedance transfer function determining module is used for obtaining an impedance transfer function from output current to grid-connected point voltage of a single inverter under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model;
the coherent grouping module is used for determining the coherent criterion of the inverters based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of the n inverters and performing coherent grouping on the n inverters;
and the aggregation parameter calculation module is used for calculating aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system so as to perform simulation analysis on the multi-inverter system of the new energy station.
Example 4
The present embodiment provides a processing device corresponding to the new energy grid-connected inverter small signal equivalence modeling method provided in embodiment 1, where the processing device may be a processing device for a client, such as a mobile phone, a notebook computer, a tablet computer, a desktop computer, and the like, to execute the method of embodiment 1.
The processing equipment comprises a processor, a memory, a communication interface and a bus, wherein the processor, the memory and the communication interface are connected through the bus so as to complete mutual communication. A computer program capable of running on the processor is stored in the memory, and when the processor runs the computer program, the new energy grid-connected inverter small signal equivalent modeling method provided in embodiment 1 is executed.
In some embodiments, the Memory may be a high-speed Random Access Memory (RAM) and may also include a non-volatile Memory, such as at least one disk Memory.
In other embodiments, the processor may be various general-purpose processors such as a Central Processing Unit (CPU), a Digital Signal Processor (DSP), and the like, and is not limited herein.
Example 5
The new energy grid-connected inverter small signal equivalence modeling method of this embodiment 1 may be embodied as a computer program product, and the computer program product may include a computer readable storage medium on which computer readable program instructions for executing the new energy grid-connected inverter small signal equivalence modeling method of this embodiment 1 are loaded.
The computer readable storage medium may be a tangible device that holds and stores the instructions for use by the instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic memory device, a magnetic memory device, an optical memory device, an electromagnetic memory device, a semiconductor memory device, or any combination of the foregoing.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A new energy grid-connected inverter small signal equivalent modeling method is characterized by comprising the following steps:
obtaining an impedance transfer function from output current to grid-connected point voltage of a single inverter under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model;
determining an inverter coherence criterion based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of the n inverters, and performing coherence grouping on the n inverters;
and calculating the aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system, and performing simulation analysis on the multi-inverter system of the new energy station.
2. The small-signal equivalent modeling method for the new energy grid-connected inverter according to claim 1, wherein the method for obtaining the impedance transfer function from the output current to the grid-connected point voltage of a single inverter under a unified coordinate system based on the established linearized mathematical model of the new energy grid-connected inverter comprises the following steps:
establishing a mathematical model of the new energy grid-connected inverter;
linearizing the mathematical model to obtain the relation between grid-connected point voltage and grid-connected inverter output current of a single inverter under a dq synchronous rotation coordinate system;
and selecting an infinite power grid as a unified coordinate system, and converting the relation between the grid-connected point voltage and the inverter output current of the single inverter under the dq synchronous rotation coordinate system into the unified coordinate system.
3. The small-signal equivalent modeling method for the new energy grid-connected inverter according to claim 1, wherein the method for determining an inverter coherence criterion based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of n inverters, and performing coherence clustering on the n inverters comprises the following steps:
establishing inverter coherence criterion based on a frequency domain transfer function;
simplifying the inverter coherence criterion based on the amplitude-frequency characteristic of the impedance transfer function to obtain the impedance transfer function Z xx Practical criteria of amplitude-frequency characteristic response;
defining the difference degree of the inverter according to the practical coherence criterion;
and sequentially calculating the difference degree of every two inverters, and carrying out coherence discrimination and grouping on the inverters according to the difference degree and the selected allowable error.
4. The small-signal equivalent modeling method for the new energy grid-connected inverter according to claim 3, characterized in that the difference degree of the inverter is as follows:
ε ij ＝|G i (Z xxi (s))-G j (Z xxj (s))|
in the formula, epsilon ij Is the degree of disparity of the inverters; z xxi (s) and Z xxj And(s) are impedance transfer functions of the variation of the x-axis output current of the ith inverter and the jth inverter to the variation of the x-axis grid-connected point voltage in a unified coordinate system respectively.
5. The small-signal equivalent modeling method for the new energy grid-connected inverter according to claim 1, wherein when calculating the aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters, the method comprises the following steps: the method comprises the steps of circuit structure parameter aggregation and control system parameter aggregation, wherein the control system parameter aggregation comprises the phase-locked loop control parameter aggregation and the current loop control parameter aggregation.
6. The small-signal equivalent modeling method for the new energy grid-connected inverter according to claim 5, characterized in that the aggregation of the circuit structure parameters is as follows:
L f,eq ＝L f1 //L f2 //…//L fn
in the formula, L f,eq Filter inductance, L, being an equivalent model f1 、L f2 、……L fn Respectively showing the filter inductance of the 1 st to the nth grid-connected inverters in a certain coordination group.
7. The small signal equivalent modeling method for the new energy grid-connected inverter according to claim 5, characterized in that the aggregation method of the control parameters of the phase-locked loop is as follows:
in the formula, k pPLL,eq And k iPLL,eq The proportional coefficient and the integral coefficient of the phase-locked loop of the equivalent system are respectively; k is a radical of pPLLi And k iPLLi Proportional coefficient and integral coefficient of the ith inverter phase-locked loop, c i The weighting coefficient of the ith inverter;
the polymerization method of the current loop control parameters comprises the following steps:
in the formula, k pi,eq And k ii,eq Current loop ratio of the respective equivalent systemA coefficient and an integral coefficient; k is a radical of pij And k iij Proportional and integral coefficients, c, of the jth inverter current loop, respectively j Is the weight coefficient of the jth inverter.
8. A small signal equivalent modeling system of a new energy grid-connected inverter is characterized by comprising:
the impedance transfer function determining module is used for obtaining an impedance transfer function from output current to grid-connected point voltage of a single inverter under a unified coordinate system based on the established new energy grid-connected inverter linear mathematical model;
the coherent grouping module is used for determining the coherent criterion of the inverters based on the impedance transfer function, calculating the difference degree of the amplitude-frequency characteristics of the n inverters and performing coherent grouping on the n inverters;
and the aggregation parameter calculation module is used for calculating aggregation parameters of the inverters in each coherent group based on the grouping result of the inverters to obtain a coherent equivalence model of the multi-inverter system, and performing simulation analysis on the multi-inverter system of the new energy station.
9. A processing device comprising at least a processor and a memory, the memory having stored thereon a computer program, characterized in that the processor executes, when executing the computer program, the steps to implement the new energy grid-connected inverter small signal equivalence modeling method according to any one of claims 1 to 7.
10. A computer storage medium having computer readable instructions stored thereon, the computer readable instructions being executable by a processor to implement the steps of the new energy grid-connected inverter small signal equivalence modeling method according to any one of claims 1 to 7.
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