CN110336279B - Electric power system oscillation self-adaptive suppression method, system and medium based on grid-connected converter - Google Patents
Electric power system oscillation self-adaptive suppression method, system and medium based on grid-connected converter Download PDFInfo
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/002—Flicker reduction, e.g. compensation of flicker introduced by non-linear load
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Abstract
The invention discloses a grid-connected converter-based power system oscillation self-adaptive suppression method, system and medium, and belongs to the field of power system dynamic stability. The method comprises the steps of collecting a feedback electric signal of a power grid connected with a grid-connected converter, separating a fundamental frequency component according to the feedback electric signal to obtain the feedback electric signal after the fundamental frequency component is separated, extracting oscillation signal characteristics according to the feedback electric signal after the fundamental frequency component is separated and the oscillation signal characteristics, generating an oscillation suppression signal according to the feedback electric signal after the fundamental frequency component is separated and the oscillation signal characteristics, superposing the oscillation suppression signal to a current control signal of the grid-connected converter to obtain a comprehensive control signal, generating a PWM trigger pulse signal and outputting the PWM trigger pulse signal to a control end of the grid-connected converter, and realizing. The invention can realize the on-line identification and the self-adaptive suppression of the middle-high frequency band oscillation of the power system, and can effectively improve the dynamic stable operation capability of the power system.
Description
Technical Field
The invention relates to an oscillation suppression technology of a power system, in particular to a power system oscillation self-adaptive suppression method, system and medium based on a grid-connected converter.
Background
The large-scale new energy such as wind power, photovoltaic and the like is combined into a power grid to provide clean power for the power system, and meanwhile certain challenges are brought to the safe and stable operation of the power system. Wind power, photovoltaic and other new energy sources generally realize energy conversion in different forms and are connected to an alternating current power system through a grid-connected converter based on power electronic devices, the grid-connected converter is different from the traditional electrical conversion equipment based on ferromagnetic elements, and the conversion of electric quantity is realized by means of orderly opening and closing of switches, so that the dynamic characteristic of the grid-connected converter is influenced by the dynamic state of the switches and the control algorithm of the grid-connected converter to a great extent. Complex control algorithms for grid-connected converters present challenges to system operators in understanding their dynamic behavior. Meanwhile, equipment manufacturers generally do not consider the complex grid conditions of the actual power system when designing the control algorithm of the converter, so that the designed control algorithm cannot adapt to the actual operating system environment, and even systematic oscillation can be caused after the control algorithm is connected into the power system, thereby endangering the stable operation of the power system. From reports related to power grid operation at home and abroad, an oscillation event caused in an actual system by large-scale wind power and photovoltaic grid connection causes great economic loss, so that a corresponding oscillation suppression measure needs to be sought.
The oscillation of the power system is generally caused by the mechanical/electrical characteristics or control characteristics of the grid-connected equipment, the oscillation forms are complex and various, the oscillation frequency range is wide, and particularly the oscillation caused by the grid-connected converter can reach kilohertz. And the suppression measures are rich for various oscillations in the power system. In summary, the suppression measures of oscillation can be started from two aspects, namely the characteristics of the adjustment device and the external damping device, and the two oscillation suppression modes have advantages and disadvantages respectively.
For example, chinese patent document No. cn201610060554.x discloses a method and a system for damping control of an electric power system including a plurality of fans, in which a fan tie power fluctuation signal sequence and an inter-area ac tie power fluctuation signal sequence are obtained by measuring a fan tie power signal and an inter-area ac tie power signal. And then, a power system state space model is constructed according to the signal sequence and a subspace state space identification algorithm of the power system. And the model is used for selecting a fan and installing an additional damping controller designed by adopting a phase compensation method so as to improve the suppression effect on the low-frequency oscillation of the power system. However, the method is only suitable for the power system with wind power integration.
For example, chinese patent application No. cn201820681809 discloses a distributed subsynchronous oscillation suppression device based on energy storage and a new energy power transmission system, where the subsynchronous oscillation suppression device is installed on a power transmission line between a new energy electric field and a bus bar, and is connected in series to the power transmission line, and injects subsynchronous oscillation impedance voltage into the power transmission line according to a subsynchronous oscillation impedance signal, thereby finally realizing suppression of subsynchronous oscillation of the system. The energy storage device is used for stabilizing the fluctuation of the voltage at two ends of the capacitor in the subsynchronous oscillation suppression device, so that the suppression capability of the distributed subsynchronous oscillation suppression device can be improved, and the frequency range of subsynchronous oscillation suppression is enlarged. However, the method is mainly used for inhibiting the subsynchronous oscillation of the system caused by new energy grid connection, and a corresponding oscillation inhibiting device is required to be additionally arranged.
For example, chinese patent application No. cn201610604425 discloses an adjustable impedance distributed photovoltaic power generation cluster resonance suppression system and a suppression method, in which an adjustable impedance is additionally installed on a common connection point where a system bus and a distributed photovoltaic power generation cluster are connected in parallel, a central control unit detects a resonance condition of the system, and when a resonance of the system is detected, reactor groups in a resonance suppression unit are sequentially switched cyclically from a middle stage until parallel resonance of the system is suppressed. However, the method is mainly aimed at resonance suppression caused by the distributed photovoltaic power generation cluster system.
At present, large-scale grid connection of wind power/photovoltaic and variable frequency driving loads and other equipment enables a large number of grid-connected converters to be connected into a system. The grid-connected converter brings challenges to the stable operation of the system, but the control characteristic of the grid-connected converter has extremely strong plasticity, and if the control algorithm of the grid-connected converter can be reasonably designed, the negative effects caused by the control algorithm can be effectively avoided, and the stable operation capability of the power system can be even further enhanced. Therefore, based on a grid-connected converter, how to realize a damping method capable of automatically adapting to an oscillation frequency aiming at the oscillation which is difficult to predict in a system becomes a key technical problem to be solved urgently.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: aiming at the problem of uncertainty of an oscillation form of a power system, the invention provides a power system oscillation self-adaptive suppression method, a system and a medium based on a grid-connected converter. The method realizes the identification of the system oscillation mode by extracting the harmonic current component of the power grid oscillation, further utilizes the self-adaptive algorithm to adjust the converter to optimize the control response frequency band and realize the damping of the system oscillation.
In order to solve the technical problems, the invention adopts the technical scheme that:
a self-adaptive suppression method for power system oscillation based on a grid-connected converter comprises the following implementation steps:
1) acquiring a feedback electric signal of a power grid connected with a grid-connected converter;
2) separating a fundamental frequency component aiming at the feedback electric signal to obtain the feedback electric signal after the fundamental frequency component is separated;
3) extracting oscillation signal characteristics aiming at the feedback electric signal after the fundamental frequency component is separated;
4) generating an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter according to the characteristics of the feedback electric signal and the oscillation signal after the fundamental frequency component is separated so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system;
5) comprehensively superposing the oscillation suppression signal to a current control signal of the grid-connected converter to obtain a comprehensive control signal;
6) and generating a PWM trigger pulse signal according to the comprehensive control signal and outputting the PWM trigger pulse signal to a control end of the grid-connected converter, so as to realize the self-adaptive suppression of the oscillation of the power system.
Optionally, the detailed steps of step 2) include:
2.1) mapping a feedback electric signal of a power grid connected with the grid-connected converter to a power grid synchronous rotating coordinate system through coordinate forward transformation, so that a fundamental frequency component is converted into a direct current signal;
2.2) filtering the fundamental frequency component which is converted into the direct current signal in the feedback electric signal mapped to the power grid synchronous rotation coordinate system, so as to realize the separation of the fundamental frequency component of the feedback electric signal from other components;
and 2.3) carrying out coordinate conversion on the feedback electric signal after the fundamental frequency component is filtered out and mapping the feedback electric signal back to a static coordinate system to obtain the feedback electric signal after the fundamental frequency component is separated.
Optionally, in step 2.2), when the fundamental frequency component converted into the direct current signal in the feedback electric signal mapped to the power grid synchronous rotation coordinate system is filtered, the filter used is a high-pass filter or a wave trap.
Optionally, when the oscillation signal feature is extracted from the feedback electrical signal after the fundamental frequency component is separated in step 3), the extracted oscillation signal feature is the oscillation frequency, or the amplitude, or the phase of the feedback electrical signal after the fundamental frequency component is separated.
Optionally, the feedback electric signal of the power grid connected to the grid-connected converter is collected in step 1) to be a feedback voltage signal.
Optionally, the feedback electric signal of the power grid connected with the grid-connected converter is collected in step 1) to be a feedback current signal idq(ii) a Step 2) obtaining the feedback electric signal after the fundamental frequency component is separated into a feedback current signal i after the fundamental frequency component is separatedhdq(ii) a When the characteristics of the oscillation signal are extracted from the feedback electrical signal after the fundamental frequency component is separated in the step 3), the extracted characteristics of the oscillation signal are the feedback current signal i after the fundamental frequency component is separatedhdqPhase of (a)iAnd the detailed step of extracting the oscillation signal features comprises:
3.1) separating the feedback current signal i after the fundamental frequency componenthdqCarrying out proportional integral control;
3.2) output result of proportional-integral control and preset constant omegaiSumming to obtain the frequency ω of the oscillation signal, wherein the frequency ω is a predetermined constantiSetting parameters for determining a corresponding response frequency band in an initial state for optimal control;
3.3) obtaining the feedback current signal i after the fundamental frequency component is separated by the frequency omega of the oscillation signal through integral operationhdqPhase of (a)iAnd separating the feedback current signal i after the fundamental frequency componenthdqPhase of (a)iAs the extracted oscillation signal characteristics.
Optionally, the feedback electric signal of the power grid connected with the grid-connected converter is collected in step 1) to be a feedback current signal idq(ii) a Step 2) obtaining the feedback electric signal after the fundamental frequency component is separated into a feedback current signal i after the fundamental frequency component is separatedhdq(ii) a When the characteristics of the oscillation signal are extracted from the feedback electrical signal after the fundamental frequency component is separated in the step 3), the extracted characteristics of the oscillation signal are the feedback current signal i after the fundamental frequency component is separatedhdqPhase of (a)i(ii) a The detailed steps of the step 4) comprise:
4.1) separating the feedback current signal i after the fundamental frequency componenthdqMapping the coordinate positive transformation to a power grid synchronous rotating coordinate system to obtain a direct current type current output component ihxAnd ihy；
4.2) for a current output component i in DC formhxAnd ihyCarrying out proportional conversion and low-pass filtering to generate an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system;
4.3) carrying out coordinate conversion on the oscillation suppression signal coordinates and mapping the oscillation suppression signal coordinates back to a static coordinate system so as to enable the oscillation suppression signal coordinates and the feedback current signal i after the fundamental frequency component is separatedhdqThe coordinate systems are the same.
The invention also provides a power system oscillation self-adaptive suppression system based on the grid-connected converter, which comprises the following components:
the signal sampling program unit is used for sampling a feedback electric signal of a power grid connected with the grid-connected converter;
the signal preprocessing program unit is used for separating a fundamental frequency component from a feedback electric signal of a power grid connected with the grid-connected converter to obtain the feedback electric signal after the fundamental frequency component is separated;
the oscillating signal characteristic identification program unit is used for extracting oscillating signal characteristics aiming at the feedback electric signal after the fundamental frequency component is separated;
the oscillation suppression signal generation program unit is used for generating an oscillation suppression signal which is used for adjusting the response bandwidth of each control branch of the grid-connected converter so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system according to the feedback electric signal and the oscillation signal characteristic after the fundamental frequency component is separated;
the signal comprehensive program unit is used for comprehensively superposing the oscillation suppression signal to the current control signal of the grid-connected converter to obtain a comprehensive control signal;
and the signal output program unit is used for generating a PWM trigger pulse signal according to the comprehensive control signal and outputting the PWM trigger pulse signal to a control end of the grid-connected converter so as to realize the self-adaptive suppression of the oscillation of the power system.
The invention also provides a grid-connected converter based power system oscillation adaptive suppression system, which comprises a computer device programmed or configured to execute the steps of the grid-connected converter based power system oscillation adaptive suppression method, or a storage medium of the computer device having stored thereon a computer program programmed or configured to execute the grid-connected converter based power system oscillation adaptive suppression method.
The present invention also provides a computer readable storage medium having stored thereon a computer program programmed or configured to perform the grid-tied converter based power system oscillation adaptive suppression method.
The invention also provides a power system oscillation self-adaptive suppression system based on the grid-connected converter, which comprises a direct current filter capacitor, the grid-connected converter, an alternating current filter and a control unit, wherein the direct current filter capacitor is connected with a power grid through the grid-connected converter, the alternating current filter and the power grid in sequence; or a storage medium of the control unit, having stored thereon a computer program programmed or configured to perform the grid-connected converter based power system oscillation adaptive suppression method.
Compared with the prior art, the invention has the following advantages:
1. aiming at the problem of oscillation of a middle-frequency band and a high-frequency band of a power system, the invention provides the method for realizing online identification and self-adaptive suppression of system oscillation by utilizing the optimization control of a grid-connected converter. The method realizes the identification of the system oscillation mode by extracting the harmonic current component of the power grid oscillation, further utilizes the self-adaptive algorithm to adjust the converter to optimize the control response frequency band and realize the damping of the system oscillation.
2. According to the invention, the fundamental frequency component is separated aiming at the feedback electric signal, so that the feedback electric signal after the fundamental frequency component is separated is obtained, the fundamental frequency component can be effectively separated, and a foundation is laid for extracting oscillation electric quantity information; the characteristics of the oscillation signal are extracted aiming at the feedback electric signal after the fundamental frequency component is separated, so that the characteristics of the system oscillation signal can be effectively extracted, and the self-adaptive adjustment of the dynamic characteristic of the converter is guaranteed; the self-adaptive adjustment of the dynamic characteristic of the grid-connected converter can be realized by generating an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter according to the characteristics of the feedback electric signal and the oscillation signal after the fundamental frequency component is separated so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the electric power system, so that the damping of the converter in the corresponding frequency band is improved; the oscillation suppression signal is comprehensively superposed on the current control signal of the grid-connected converter to obtain a comprehensive control signal, so that the integration of the traditional current control output and the algorithm output signal can be realized, and the characteristic of equipment can be adjusted on the basis of not changing the original traditional current control algorithm.
Drawings
FIG. 1 is a schematic diagram of a basic flow of a method according to an embodiment of the present invention.
FIG. 2 is a schematic flow chart of the step 2) pretreatment according to the embodiment of the present invention.
Fig. 3 is a schematic flow chart of generating the oscillation suppression signal in step 4) according to the embodiment of the present invention.
FIG. 4 is a block diagram of a system according to an embodiment of the present invention.
Illustration of the drawings: 1. a DC filter capacitor; 2. a grid-connected converter; 3. an AC filter; 4. a control unit; 41. a signal sampling program unit; 42. a signal preprocessing program unit; 43. an oscillation signal characteristic identification program unit; 44. an oscillation suppression signal generation program unit; 45. a signal integration program unit; 46. a signal output program unit; 47. a conventional current control program unit.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples.
It should be understood that the following examples are only for illustrating the present invention, but not for limiting the scope of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
As shown in fig. 1, the implementation steps of the grid-connected converter-based power system oscillation adaptive suppression method of the present embodiment include:
1) acquiring a feedback electric signal of a power grid connected with a grid-connected converter;
2) separating a fundamental frequency component aiming at the feedback electric signal to obtain the feedback electric signal after the fundamental frequency component is separated;
3) extracting oscillation signal characteristics aiming at the feedback electric signal after the fundamental frequency component is separated;
4) generating an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter according to the characteristics of the feedback electric signal and the oscillation signal after the fundamental frequency component is separated so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system;
5) comprehensively superposing the oscillation suppression signal to a current control signal of the grid-connected converter to obtain a comprehensive control signal;
6) and generating a PWM trigger pulse signal according to the comprehensive control signal and outputting the PWM trigger pulse signal to a control end of the grid-connected converter, so as to realize the self-adaptive suppression of the oscillation of the power system.
As shown in fig. 2, the detailed steps of step 2) of this embodiment include:
2.1) mapping a feedback electric signal of a power grid connected with the grid-connected converter to a power grid synchronous rotating coordinate system through coordinate forward transformation, so that a fundamental frequency component is converted into a direct current signal;
2.2) filtering the fundamental frequency component which is converted into the direct current signal in the feedback electric signal mapped to the power grid synchronous rotation coordinate system, so as to realize the separation of the fundamental frequency component of the feedback electric signal from other components;
and 2.3) carrying out coordinate conversion on the feedback electric signal after the fundamental frequency component is filtered out and mapping the feedback electric signal back to a static coordinate system to obtain the feedback electric signal after the fundamental frequency component is separated.
In this embodiment, in the step 2.2), when the fundamental frequency component converted into the direct current signal in the feedback electrical signal mapped to the power grid synchronous rotation coordinate system is filtered, the filter used is a high-pass filter. It should be noted that fig. 2 only shows a method for signal preprocessing (i.e. separating the fundamental frequency component from the feedback electrical signal to obtain the feedback electrical signal after separating the fundamental frequency component), and other filtering algorithms for separating the fundamental wave, such as a trap, can also be used to implement signal preprocessing, that is: and separating the fundamental frequency component aiming at the feedback electric signal to obtain the feedback electric signal after the fundamental frequency component is separated.
And 3) when the oscillation signal characteristics are extracted from the feedback electrical signal after the fundamental frequency component is separated, the extracted oscillation signal characteristics are the oscillation frequency, amplitude or phase of the feedback electrical signal after the fundamental frequency component is separated.
And 1) acquiring a feedback electric signal of a power grid connected with the grid-connected converter as a feedback voltage signal or a feedback current signal.
As a specific implementation manner, in this embodiment, in step 1), the feedback electrical signal of the power grid connected to the grid-connected converter is collected as the feedback current signal idq(ii) a Step 2) obtaining the feedback electric signal after the fundamental frequency component is separated into a feedback current signal i after the fundamental frequency component is separatedhdq(ii) a When the characteristics of the oscillation signal are extracted from the feedback electrical signal after the fundamental frequency component is separated in the step 3), the extracted characteristics of the oscillation signal are the feedback current signal i after the fundamental frequency component is separatedhdqPhase of (a)iAnd the detailed step of extracting the oscillation signal features comprises:
3.1) separating the feedback current signal i after the fundamental frequency componenthdqCarrying out proportional integral control;
3.2) output result of proportional-integral control and preset constant omegaiSumming to obtain the frequency ω of the oscillation signal, wherein the frequency ω is a predetermined constantiSetting parameters for determining a corresponding response frequency band in an initial state for optimal control;
3.3) obtaining the feedback current signal i after the fundamental frequency component is separated by the frequency omega of the oscillation signal through integral operationhdqPhase of (a)iAnd separating the feedback current signal i after the fundamental frequency componenthdqPhase of (a)iAs the extracted oscillation signal characteristics.
As a specific implementation manner, as shown in fig. 3, the detailed step of step 4) in this embodiment includes:
4.1) separating the feedback current signal i after the fundamental frequency componenthdqMapping the coordinate positive transformation to a power grid synchronous rotating coordinate system to obtain a direct current type current output component ihxAnd ihy；
4.2) for a current output component i in DC formhxAnd ihyCarrying out proportional conversion and low-pass filtering, and generating an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system, namely: e.g. of the typecxy；
4.3) carrying out coordinate conversion on the oscillation suppression signal coordinates and mapping the oscillation suppression signal coordinates back to a static coordinate system so as to enable the oscillation suppression signal coordinates and the feedback current signal i after the fundamental frequency component is separatedhdqThe coordinate systems are the same, and the following results are obtained: e.g. of the typecdq。
Referring to fig. 3, in step 4.2) of the present embodiment, the direct current form of the current output component i is aimed athxAnd ihyThe mathematical expression of the processing used when performing the scaling and the low-pass filtering is shown in formula (1):
Rv/(Tus+1)(1)
in the formula (1), RvCoefficient of proportional amplification, TuRepresenting a low-pass filtering time constant, s being an input quantity;
in this embodiment, the transformation matrix mapped to the grid synchronous rotation coordinate system in step 2.1) and step 4.1) through coordinate forward transformation is C2s/2rThe mathematical expression is shown as formula (2); in this embodiment, the transformation matrix that performs coordinate transformation mapping back to the stationary coordinate system in step 2.3) and step 4.13) is C2r/2sThe mathematical expression is shown as formula (3);
in the formulae (2) and (3), θiRepresenting the feedback current signal i after separation from the fundamental frequency componenthdqThe phase of (c).
In addition, this embodiment also provides a power system oscillation adaptive suppression system based on grid-connected converter, including:
a signal sampling program unit 41, configured to sample a feedback electrical signal of a power grid connected to the grid-connected converter;
the signal preprocessing program unit 42 is configured to separate a fundamental frequency component from a feedback electrical signal of a power grid connected to the grid-connected converter to obtain a feedback electrical signal after the fundamental frequency component is separated;
an oscillation signal feature identification program unit 43, configured to extract an oscillation signal feature for the feedback electrical signal after the fundamental frequency component is separated;
an oscillation suppression signal generation program unit 44, configured to generate an oscillation suppression signal for adjusting a response bandwidth of each control branch of the grid-connected converter according to the feedback electrical signal and the oscillation signal characteristic after the fundamental frequency component is separated, so as to change a dynamic characteristic of a frequency band corresponding to the grid-connected converter and achieve adaptive suppression of oscillation of the power system;
a signal integration program unit 45 for integrating and superimposing the oscillation suppression signal to the current control signal of the grid-connected converter to obtain an integrated control signal;
and the signal output program unit 46 is used for generating a PWM trigger pulse signal according to the comprehensive control signal and outputting the PWM trigger pulse signal to the control end of the grid-connected converter, so as to realize adaptive suppression of the oscillation of the power system.
In this embodiment, the current control signal of the grid-connected converter is obtained by the existing conventional current control program unit 47 in the control unit 4 by using the existing current control strategy, and in addition, the working requirement of the signal synthesis program unit 45 can be met by giving the current control signal of the grid-connected converter by an external processor, and since how to specifically obtain the current control signal of the grid-connected converter is not discussed in this embodiment, it is not listed in the above-mentioned system.
It should be noted that the program element may be implemented in a single microprocessor, or may be implemented by a plurality of microprocessors in conjunction with data communication between the microprocessors.
In addition, the present embodiment also provides a grid-connected converter based power system oscillation adaptive suppression system, which includes a computer device programmed or configured to execute the steps of the aforementioned grid-connected converter based power system oscillation adaptive suppression method, or a storage medium of the computer device having stored thereon a computer program programmed or configured to execute the aforementioned grid-connected converter based power system oscillation adaptive suppression method.
Furthermore, the present embodiment also provides a computer-readable storage medium having stored thereon a computer program programmed or configured to execute the aforementioned grid-connected converter-based power system oscillation adaptive suppression method.
In addition, referring to fig. 4, the present embodiment further provides a grid-connected converter-based power system oscillation adaptive suppression system, including a dc filter capacitor 1, a grid-connected converter 2, an ac filter 3, and a control unit 4, where the dc filter capacitor 1 is connected to a power grid through the grid-connected converter 2 and the ac filter 3 in sequence, a feedback electrical signal input end of the control unit 4 is connected to an ac side of the grid-connected converter 2, a control output end is connected to a control end of the grid-connected converter 2, and the control unit 4 performs current control according to a received current command value and a feedback electrical signal input at the ac side of the grid-connected converter 2 to obtain a current control signal, and is characterized in that the control unit 4 is programmed or configured to execute the steps of the aforementioned grid-connected converter-based power system oscillation adaptive suppression method; or a storage medium of the control unit 4, has stored thereon a computer program programmed or configured to perform the aforementioned grid-connected converter based power system oscillation adaptive suppression method.
It should be noted that the control unit 4 performs current control according to the received current instruction value and the feedback electrical signal input at the ac side of the grid-connected converter 2 to obtain a current control signal, which is the existing current control strategy of the grid-connected converter 2, and is used for implementing current control in the converter, and the specific implementation of the control algorithm includes, but is not limited to, dual PI control based on a phase-locked synchronous coordinate system, proportional resonance control in a stationary coordinate system, Bang-Bang control, and the like.
Referring to fig. 2, the signal sampling program unit 41 of this embodiment is configured to collect power grid power information, filter and convert the power grid power information, and feed back the power grid power information to each program unit, and includes a conventional current control program unit 47 configured to perform current control according to a received current instruction value and a feedback electrical signal input at an ac side of the grid-connected converter 2 to obtain a current control signal.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application 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 application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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.
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 self-adaptive suppression method for power system oscillation based on a grid-connected converter is characterized by comprising the following implementation steps:
1) acquiring a feedback electric signal of a power grid connected with a grid-connected converter;
2) separating a fundamental frequency component aiming at the feedback electric signal to obtain the feedback electric signal after the fundamental frequency component is separated;
3) extracting oscillation signal characteristics aiming at the feedback electric signal after the fundamental frequency component is separated;
4) generating an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter according to the characteristics of the feedback electric signal and the oscillation signal after the fundamental frequency component is separated so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system;
5) comprehensively superposing the oscillation suppression signal to a current control signal of the grid-connected converter to obtain a comprehensive control signal;
6) generating a PWM trigger pulse signal according to the comprehensive control signal and outputting the PWM trigger pulse signal to a control end of a grid-connected converter to realize the self-adaptive suppression of the oscillation of the power system;
acquiring a feedback electric signal of a power grid connected with a grid-connected converter in the step 1) as a feedback current signali dq (ii) a Step 2) obtaining the feedback electric signal after the fundamental frequency component is separated into a feedback current signal after the fundamental frequency component is separatedi hdq (ii) a When the characteristics of the oscillation signal are extracted from the feedback electrical signal after the fundamental frequency component is separated in step 3), the extracted characteristics of the oscillation signal are the feedback current signal after the fundamental frequency component is separatedi hdq Phase ofθ i And the detailed step of extracting the oscillation signal features comprises: 3.1) separating the feedback current signal of the fundamental frequency componenti hdq Carrying out proportional integral control; 3.2) output result of proportional-integral control and preset constantω i Summing to obtain the frequency of the oscillating signalωWherein a predetermined constant ω i Setting parameters for determining a corresponding response frequency band in an initial state for optimal control; 3.3) frequency of the oscillating signalωObtaining feedback current signal after separating fundamental frequency component by integral operationi hdq Phase ofθ i And separating the feedback current signal of the fundamental frequency componenti hdq Phase ofθ i As the extracted oscillation signal characteristics.
2. The grid-connected converter based power system oscillation adaptive suppression method according to claim 1, wherein the detailed steps of step 2) comprise: 2.1) mapping a feedback electric signal of a power grid connected with the grid-connected converter to a power grid synchronous rotating coordinate system through coordinate forward transformation, so that a fundamental frequency component is converted into a direct current signal; 2.2) filtering the fundamental frequency component which is converted into the direct current signal in the feedback electric signal mapped to the power grid synchronous rotation coordinate system, so as to realize the separation of the fundamental frequency component of the feedback electric signal from other components; and 2.3) carrying out coordinate conversion on the feedback electric signal after the fundamental frequency component is filtered out and mapping the feedback electric signal back to a static coordinate system to obtain the feedback electric signal after the fundamental frequency component is separated.
3. The grid-connected converter based power system oscillation adaptive suppression method according to claim 2, wherein in the step 2.2), when the fundamental frequency component converted into the direct current signal in the feedback electric signal mapped to the grid synchronous rotation coordinate system is filtered, the adopted filter is a high-pass filter or a wave trap.
4. The grid-connected converter-based power system oscillation adaptive suppression method according to claim 1, wherein when the oscillation signal characteristics are extracted from the feedback electrical signal after the fundamental frequency component is separated in step 3), the extracted oscillation signal characteristics are oscillation frequency, amplitude or phase of the feedback electrical signal after the fundamental frequency component is separated.
5. The grid-connected converter-based power system oscillation self-adaptive suppression method according to claim 1, wherein a feedback electric signal of a power grid connected with the grid-connected converter is collected in the step 1) to be a feedback voltage signal.
6. The grid-connected converter-based power system oscillation self-adaptive suppression method according to claim 1, wherein in the step 1), the feedback electric signal of the power grid connected with the grid-connected converter is collected to be a feedback current signali dq (ii) a Step 2) obtaining the feedback electric signal after the fundamental frequency component is separated into a feedback current signal after the fundamental frequency component is separatedi hdq (ii) a When the characteristics of the oscillation signal are extracted from the feedback electrical signal after the fundamental frequency component is separated in step 3), the extracted characteristics of the oscillation signal are the feedback current signal after the fundamental frequency component is separatedi hdq Phase ofθ i (ii) a The detailed steps of the step 4) comprise: 4.1) separating the feedback current signal of the fundamental frequency componenti hdq Mapping the coordinate positive transformation to a power grid synchronous rotating coordinate system to obtain a direct current type current output componenti hx Andi hy (ii) a 4.2) Current output component for DC formi hx Andi hy carrying out proportional conversion and low-pass filtering to generate an oscillation suppression signal for adjusting the response bandwidth of each control branch of the grid-connected converter so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system; 4.3) carrying out coordinate conversion on the oscillation suppression signal coordinates and mapping the oscillation suppression signal coordinates back to a static coordinate system so as to enable the oscillation suppression signal coordinates and the feedback current signal after the fundamental frequency component is separatedi hdq The coordinate systems are the same.
7. A self-adaptive power system oscillation suppression system based on a grid-connected converter is characterized by comprising:
a signal sampling program unit (41) for sampling a feedback electric signal of a power grid connected with the grid-connected converter;
the signal preprocessing program unit (42) is used for separating a fundamental frequency component aiming at a feedback electric signal of a power grid connected with the grid-connected converter to obtain the feedback electric signal after the fundamental frequency component is separated;
an oscillation signal feature identification program unit (43) for extracting an oscillation signal feature with respect to the feedback electric signal after the separation of the fundamental frequency component;
the oscillation suppression signal generation program unit (44) is used for generating an oscillation suppression signal which is used for adjusting the response bandwidth of each control branch of the grid-connected converter so as to change the dynamic characteristic of the corresponding frequency band of the grid-connected converter and realize the self-adaptive suppression of the oscillation of the power system according to the feedback electric signal and the oscillation signal characteristic after the fundamental frequency component is separated;
the signal synthesis program unit (45) is used for synthetically superposing the oscillation suppression signal to the current control signal of the grid-connected converter to obtain a comprehensive control signal;
the signal output program unit (46) is used for generating a PWM trigger pulse signal according to the comprehensive control signal and outputting the PWM trigger pulse signal to a control end of the grid-connected converter so as to realize the self-adaptive suppression of the oscillation of the power system;
the signal sampling program unit (41) collects a feedback electric signal of a power grid connected with the grid-connected converter into a feedback current signali dq (ii) a The signal preprocessing program unit (42) obtains the feedback electric signal after the fundamental frequency component is separated as a feedback current signal after the fundamental frequency component is separatedi hdq (ii) a When the oscillation signal feature identification program unit (43) extracts the oscillation signal feature for the feedback electric signal after the separation of the fundamental frequency component, the extracted oscillation signal feature is the feedback current signal after the separation of the fundamental frequency componenti hdq Phase ofθ i And the detailed step of extracting the oscillation signal features comprises: 3.1) separating the feedback current signal of the fundamental frequency componenti hdq Carrying out proportional integral control; 3.2) output result of proportional-integral control and preset constantω i Summing to obtain the frequency of the oscillating signalωWherein a predetermined constant ω i Setting parameters for determining a corresponding response frequency band in an initial state for optimal control; 3.3) frequency of the oscillating signalωObtaining feedback current signal after separating fundamental frequency component by integral operationi hdq Phase ofθ i And separating the feedback current signal of the fundamental frequency componenti hdq Phase ofθ i As the extracted oscillation signal characteristics.
8. A grid-connected converter based power system oscillation adaptive suppression system comprising a computer device, characterized in that the computer device is programmed or configured to perform the steps of the grid-connected converter based power system oscillation adaptive suppression method according to any one of claims 1 to 6, or a storage medium of the computer device has stored thereon a computer program programmed or configured to perform the grid-connected converter based power system oscillation adaptive suppression method according to any one of claims 1 to 6.
9. A computer readable storage medium having stored thereon a computer program programmed or configured to perform the method of adaptive suppression of grid-connected converter based power system oscillations according to any of claims 1 to 6.
10. An electric power system oscillation self-adaptive suppression system based on a grid-connected converter comprises a direct current filter capacitor (1), a grid-connected converter (2), an alternating current filter (3) and a control unit (4), the direct current filter capacitor (1) is connected with a power grid through a grid-connected converter (2) and an alternating current filter (3) in sequence, the feedback electric signal input end of the control unit (4) is connected with the alternating current side of the grid-connected converter (2), the control output end of the control unit is connected with the control end of the grid-connected converter (2), the control unit (4) controls the current according to the received current instruction value and a feedback electric signal input by the alternating current side of the grid-connected converter (2) to obtain a current control signal, characterized in that the control unit (4) is programmed or configured to perform the steps of the grid-connected converter based power system oscillation adaptive suppression method according to any one of claims 1 to 6; or a storage medium of the control unit (4) having stored thereon a computer program programmed or configured to perform the grid-connected converter based power system oscillation adaptive suppression method according to any of claims 1-6.
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