CN113113934B - Quasi-synchronous switching-on method, device and system considering frequency fluctuation - Google Patents
Quasi-synchronous switching-on method, device and system considering frequency fluctuation Download PDFInfo
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- CN113113934B CN113113934B CN202110351165.3A CN202110351165A CN113113934B CN 113113934 B CN113113934 B CN 113113934B CN 202110351165 A CN202110351165 A CN 202110351165A CN 113113934 B CN113113934 B CN 113113934B
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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
- H02J3/40—Synchronising a generator for connection to a network or to another generator
- H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R25/00—Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
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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
- H02J3/241—The oscillation concerning frequency
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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
- H02J3/40—Synchronising a generator for connection to a network or to another generator
- H02J3/44—Synchronising a generator for connection to a network or to another generator with means for ensuring correct phase sequence
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Abstract
The invention discloses a quasi-synchronous switching-on method, a device and a system considering frequency fluctuation, wherein the method comprises the following steps: acquiring real-time operation voltage frequency of a reference line at the side of a power grid system and real-time operation voltage frequency of a synchronized object; responding to the received quasi-synchronization closing instruction signal, and calculating the real-time voltage phase angle sum of a reference line at the side of the power grid system and a synchronized object under the same reference; according to the sum, whether any voltage on one side of two sides of the grid-connected point operates under the non-power frequency condition is judged, if yes, the real-time voltage phase angle of the corresponding voltage is corrected by using the real-time operation voltage frequency of the corresponding voltage; and determining the quasi-synchronous closing time based on the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing. The invention can reduce the influence of asynchronous sampling on the calculation of the voltage phase angle under the condition of frequency fluctuation, improve the accuracy of quasi-synchronous closing and reduce the damage of non-synchronous paralleling on a power grid system and personal safety.
Description
Technical Field
The invention relates to the technical field of power system automation, in particular to a quasi-synchronous switching-on method, a quasi-synchronous switching-on device and a quasi-synchronous switching-on system considering frequency fluctuation.
Background
With the continuous development of the industrial society, the electric power industry has a greater and greater proportion, and the concurrent juxtaposition is a very important operation frequently performed in an electric power system. The improper juxtaposition can generate huge impact on the system, and simultaneously can damage electrical equipment, further influences the stability of the electric power system, and even causes casualties, so that the improvement of the accuracy of the quasi-synchronous closing has very important significance on the reliability and the safety of the electric power system. However, the voltages on both sides of the grid-connected point often have inconsistent frequency, amplitude or phase, and even the frequency of the voltages on both sides can change constantly with a certain slip. Under the condition, the accurate closing time needs to be predicted according to the phase of the current voltage on two sides and the rule of frequency change, and the synchronous paralleling is carried out. However, under the condition of voltage frequency fluctuation, sampling of analog quantity is asynchronous, and in an actual quasi-synchronous device, frequency tracking of multi-path analog quantity and then synchronization of sampling are difficult to achieve. At the moment, the calculation of the voltage phase angle is usually performed under asynchronous sampling, the voltage phase angle calculated by using the traditional DFT algorithm has a small error, the switching-on time predicted under the calculation result is inaccurate, and no method is used for achieving the accurate prediction effect. Therefore, under the condition that the voltage frequency on the two sides of the grid-connected point fluctuates, the quasi-synchronous closing time is difficult to predict, the closing accuracy is greatly reduced, and the synchronous parallel is difficult to successfully carry out.
Disclosure of Invention
The invention aims to provide a quasi-synchronous switching-on method, a device and a system considering frequency fluctuation, which reduce the influence of asynchronous sampling on voltage phase angle calculation under the condition of frequency fluctuation, thereby improving the accuracy of quasi-synchronous switching-on and reducing the damage of non-synchronous paralleling on a power grid system and personal safety.
The technical scheme adopted by the invention is as follows: a quasi-synchronous switching-on method considering frequency fluctuation comprises the following steps:
obtaining real-time operation voltage frequency f of power grid system side reference line s And real-time operating voltage frequency f of the synchronized object x ；
Responding to the received external quasi-synchronous closing instruction signal, and calculating the real-time voltage phase angle phi of the reference line and the synchronized object under the same reference s And phi x ；
According to f s And f x Judging whether any voltage on two sides of the grid-connected point operates under the non-power frequency condition, if so, correcting the real-time voltage phase angle of the corresponding voltage by using the real-time operating voltage frequency of the corresponding voltage;
based on f s 、f x And determining the quasi-synchronous closing time by the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing.
Optionally, the method further comprises: responding to the received quasi-synchronous closing instruction signal, calculating the frequency difference f of the voltages at two sides of the grid-connected point δ ：
f δ ＝|f s -f x |
Judgment of f δ And if the frequency difference is larger than the preset frequency difference threshold value, closing is not allowed.
Above scheme, if f δ If the frequency difference is smaller than or equal to the preset frequency difference threshold value, quasi-synchronous closing operation can be executed, namely calculation and correction of a real-time voltage phase angle can be carried out, and prediction of quasi-synchronous closing time is carried out based on the corrected rubber.
The method of the invention may be performed by a quasi-contemporaneous device. Optionally, the grid system side reference line is a preset or quasi-synchronization device identified and obtained certain grid system side line with the phase voltage or line voltage close to the voltage of the synchronized object in magnitude and phase. Identification of the reference line may be based on real-time operating frequency and voltage phase angle calculations.
Optionally, the real-time operating voltage frequency f of the reference line on the power grid system side s And real-time operating voltage frequency f of the synchronized object x And the frequency measurement algorithm is used for real-time calculation by the quasi-synchronous device to obtain the frequency measurement result. The frequency measurement algorithm can adopt an existing algorithm such as a Fourier frequency measurement method, a zero crossing point frequency measurement method and the like.
In the invention, a DFT algorithm based on synchronous sampling with power frequency is adopted to calculate the real-time voltage phase angle phi of a reference line and a synchronized object on the side of a power grid system under the same reference s And phi x 。
Optionally, for a power grid system side reference line or a synchronized object with voltage running under a non-power frequency condition, the real-time running voltage frequency is used to correct the real-time voltage phase angle, and the following formula is used:
wherein phi is the real-time voltage phase angle, phi' is the corrected real-time voltage phase angle, phi ERR The phase angle deviation of the voltage, a represents a fixed deviation error, b represents a rotation deviation error, N is the number of sampling points per cycle under power frequency, lambda is the frequency deviation rate of the corrected voltage, f is the frequency of the corrected voltage, f 0 Is the frequency of the power frequency voltage.
Then, by using the above formula, the corrected real-time voltage phase angle phi can be obtained for the voltage of the reference line on the side of the power grid system when the voltage operates under the non-power frequency condition, or the voltage of the synchronized object s ' and phi x ′。
Optionally, the base is f s 、f x The corrected real-time voltage phase angle determines the quasi-synchronous closing moment, and sends a closing command at the quasi-synchronous closing moment to perform quasi-synchronous closing, and the method comprises the following steps:
calculating the acceleration of the frequency difference between the reference line voltage on the side of the power grid system and the voltage of the synchronized object, wherein the formula is as follows:
f s.last and f x.last Respectively calculating the frequency t of the voltage at two sides of the grid-connected point at the last moment of the quasi-synchronization device δ Is the time between two calculations;
calculating the corrected phase difference phi between the reference line voltage of the grid system side and the synchronized object voltage δ ；
Predicting the phase difference of the voltages at two sides of the grid-connected point after the leading time of closing, determining the quasi-synchronous closing time if the following inequality is met, and sending a closing command:
t dq 、φ gd 、φ set the device comprises a quasi-synchronization device, a control device and a control device, wherein the quasi-synchronization device is respectively preset with a closing leading time, a fixed phase difference and an angular difference fixed value allowing closing.
Optionally, the present invention calculates the corrected phase difference phi δ Neglecting the rotation deviation error, the corrected phase difference phi δ Calculated according to the following formula:
in the formula of lambda s And λ x Respectively, the frequency deviation rate of the voltage across the grid-connected point.
In a second aspect, the present invention discloses a quasi-synchronous switching-on device considering frequency fluctuation, including:
a voltage frequency calculation module configured to obtain a real-time operating voltage frequency f of the grid system side reference line s And real-time operating voltage frequency f of the synchronized object x ；
A voltage phase angle calculation module configured to calculate a real-time voltage phase angle phi of a reference line and a synchronized object on a power grid system side under the same reference in response to receiving an external quasi-synchronization closing instruction signal s And phi x ；
A non-mains frequency voltage phase angle correction module configured to correct the phase angle according to f s And f x Judging whether any voltage on two sides of the grid-connected point operates under the condition of non-power frequency, if so, correcting the real-time voltage phase angle of the corresponding voltage by utilizing the real-time operating voltage frequency of the corresponding voltage;
and a quasi-synchronous closing control module configured to be based on f s 、f x And determining the quasi-synchronous closing time by the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing.
In a third aspect, the present invention further provides a quasi-synchronous closing system considering frequency fluctuation, including a processor and a memory, where the memory stores a plurality of instructions, and the instructions are adapted to be loaded by the processor and executed by the quasi-synchronous closing method considering frequency fluctuation in the first aspect.
Advantageous effects
The quasi-synchronous closing method provided by the invention considers the situation that the sampling of voltage phase angles is asynchronous due to the frequency fluctuation of two sides of a grid-connected point, judges the non-power frequency fluctuation state by monitoring the frequency of two sides of the grid-connected point, corrects the sampled voltage phase angles by using the real-time voltage frequency when the voltage on any side of the grid-connected point works under the condition of non-power frequency fluctuation, further judges the quasi-synchronous closing time based on the corrected voltage phase angles, performs quasi-synchronous closing when the set allowable closing angle difference is met, can reliably avoid the influence of asynchronous sampling on the calculation of the voltage phase angles under the condition of frequency fluctuation, thereby improving the accuracy of quasi-synchronous closing, reducing the damage of non-synchronous closing on power equipment in a power grid and improving the safety and reliability of a power system.
Drawings
FIG. 1 is a schematic flow chart of an embodiment of the method of the present invention.
Detailed Description
The technical conception of the invention is as follows: firstly, when an electric network system runs, a quasi-synchronization device calculates the voltage frequency of the electric network system side and the voltage frequency of a synchronized object in real time, when the quasi-synchronization device receives a quasi-synchronization closing instruction, the phase angle of the system side voltage and the synchronized object voltage under the same reference at present is calculated, for the voltage of non-power frequency, the calculated phase angle is corrected according to the voltage frequency calculated in real time, and the accurate synchronization closing time is predicted on the basis of the corrected phase angle according to the calculated frequency difference and the calculated acceleration of the frequency difference between the system side voltage and the synchronized object voltage and the combined parameters of closing lead time, inherent phase angle difference and the like. The influence of asynchronous sampling on the phase angle calculation of the system side voltage and the synchronized object voltage under the condition of frequency fluctuation is avoided, and the accuracy of quasi-synchronization switching-on is improved.
The following further description is made in conjunction with the accompanying drawings and the specific embodiments.
Example 1
The embodiment introduces a quasi-synchronous closing method considering frequency fluctuation, which includes:
obtaining real-time operation voltage frequency f of power grid system side reference line s And real-time operating voltage frequency f of the synchronized object x ；
Responding to the received external quasi-synchronization closing instruction signal, calculating the real-time voltage phase angle phi of a reference line at the side of the power grid system and a synchronized object under the same reference s And phi x ；
According to f s And f x Judging whether any voltage on two sides of the grid-connected point operates under the non-power frequency condition, if so, correcting the real-time voltage phase angle of the corresponding voltage by using the real-time operating voltage frequency of the corresponding voltage;
based on f s 、f x And determining the quasi-synchronous closing time by the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing.
The situation that frequency fluctuation on two sides of a grid-connected point causes asynchronous sampling of voltage phase angles is considered, the non-power-frequency fluctuation state is judged by monitoring the frequency on two sides of the grid-connected point, when any side voltage of the grid-connected point works under the condition of non-power-frequency fluctuation, the voltage phase angles obtained by sampling are corrected by using real-time voltage frequency, further judgment of quasi-synchronous closing time is carried out based on the corrected voltage phase angles, quasi-synchronous closing is carried out when the condition that allowable closing angle differences are set is met, the influence of asynchronous sampling on system side voltage and voltage phase angle calculation of a synchronized object under the condition of frequency fluctuation can be avoided, and the quasi-synchronous closing accuracy is improved.
Examples 1 to 1
On the basis of embodiment 1, a quasi-synchronous closing method implemented by a quasi-synchronous device and considering frequency fluctuation is specifically described below, and the steps are shown in fig. 1.
1. Real-time voltage frequency calculation
When the power grid system runs, the quasi-synchronization device calculates the voltage frequency of the power grid system side and the voltage frequency of a synchronized object in real time, automatically identifies or manually sets a certain path of phase voltage or line voltage which is close to the voltage and the phase of the synchronized object, and the certain path of phase voltage or line voltage is used as reference line voltage and is used for being compared with the synchronized object voltage to detect whether the two sides of a grid-connected point reach synchronization conditions or not. For simplicity of description, the aforementioned reference line voltage will be referred to collectively as the grid system-side voltage hereinafter.
The quasi-synchronization device can utilize a self-contained frequency measurement algorithm to perform real-time frequency calculation, such as a Fourier frequency measurement method, a zero-crossing frequency measurement method and the like.
When the system runs, the quasi-synchronization device calculates the voltage frequency of the power grid system side in real time and stores the voltage frequency as f s (ii) a Calculating and storing the voltage frequency of the synchronized object in real time, and recording as f x 。
2. When the quasi-synchronization device receives a quasi-synchronization closing instruction, firstly, the frequency difference f between the side voltage of the power grid system and the voltage of a synchronized object is judged δ ：
f δ ＝|f s -f x | (1)
Judgment of f δ And if not, the calculation or operation related to the subsequent quasi-synchronous closing can be continuously executed.
3. Real-time voltage phase angle calculation
The quasi-synchronization device adopts a DFT algorithm based on synchronous sampling with power frequency to calculate a real-time voltage phase angle phi of a reference line and a synchronized object on a power grid system side under the same reference s And phi x And stored.
4. Voltage phase angle correction
Considering that the voltage frequency has fluctuation, under the condition of non-power frequency, the voltage phase angle obtained by DFT calculation executed based on the sampling frequency of the power frequency has a small error, and the prediction of the switching-on time is seriously influenced, so that the voltage phase angle of two sides of a grid-connected point running under the condition of non-power frequency fluctuation needs to be corrected.
First, f is calculated from s And f x Judging whether the voltage on either side of the grid-connected point is in the non-power frequency or even in the fluctuation condition,if so, correcting the real-time voltage phase angle of the non-power frequency voltage on any side by using the following formula:
wherein phi is the real-time voltage phase angle, phi' is the corrected real-time voltage phase angle, phi ERR The phase angle deviation of the voltage is represented by a, a represents the first half part of the back formula and is a fixed offset error, b represents the second half part of the back formula and is a rotation offset error, N is the number of sampling points per cycle at power frequency, lambda is the frequency offset rate of the corrected voltage, f is the frequency of the corrected voltage 0 Is the frequency of the power frequency voltage.
Then, by using the above formula, the corrected real-time voltage phase angle phi can be obtained for the voltage of the reference line at the side of the power grid system under the condition that the voltage operates under the non-power frequency condition, or the voltage of the synchronized object s ′、φ x ′。
With reference to the actual situation, selecting N =256 and λ =0.05 for theoretical analysis, wherein when N is larger, a is in direct proportion to the frequency deviation rate; the rotational offset error b is related to the magnitude of the voltage phase angle at the moment of calculation, and is negligible relative to the fixed offset error of the first half due to the small λ.
Therefore, in the embodiment, when the actual voltage phase angle is corrected, only the fixed offset error is considered, and the phase difference of the two corrected voltages can be obtained as follows for determining the subsequent quasi-synchronization time:
in the formula, λ s And λ x Respectively, the frequency deviation rate of the voltage across the grid-connected point.
5. Determination of quasi-synchronous closing time
As shown in fig. 1, if there is no situation that any one side of voltages operates in non-power frequency fluctuation on both sides of a grid-connected point, determining a synchronous switching-on time based on a phase angle between a synchronous voltage obtained by real-time calculation and a synchronized object voltage according to preset parameters such as switching-on lead time, inherent phase angle difference and the like, and sending a switching-on command to realize quasi-synchronous switching-on.
And for the condition that any side voltage on two sides of the grid connection point fluctuates in non-power frequency operation, determining the quasi-synchronous closing time on the basis of the corrected real-time voltage phase angle according to the calculated acceleration of the frequency and the frequency difference of the synchronous voltage and the synchronized object voltage and the parameters of closing leading time, inherent phase angle difference and the like, and further sending a closing command to realize the quasi-synchronous closing.
In particular, based on f s 、f x The corrected real-time voltage phase angle determines the quasi-synchronous closing moment, and sends a closing command at the quasi-synchronous closing moment to perform quasi-synchronous closing, and the method comprises the following steps:
calculating the acceleration of the frequency difference between the reference line voltage on the side of the power grid system and the voltage of the synchronized object, wherein the formula is as follows:
f s.last and f x.last Respectively calculating the frequency t of the voltage at two sides of the grid-connected point at the last moment of the quasi-synchronization device δ Is the time between two calculations;
calculating the corrected phase difference phi between the reference line voltage of the power grid system side and the voltage of the synchronized object by using the formula (3) δ ；
Predicting the phase difference of the voltages at two sides of the grid-connected point after the leading time of closing, determining the quasi-synchronous closing time if the following inequality is met, and sending a closing command:
t dq 、φ gd 、φ set respectively the pre-set closing leading time and fixed phase in the quasi-synchronous deviceThe difference is fixed with the angular difference allowing closing.
Example 2
Based on the same inventive concept as embodiment 1, this embodiment introduces a quasi-synchronous closing device considering frequency fluctuation, including:
a voltage frequency calculation module configured to obtain a real-time operating voltage frequency f of the grid system side reference line s And real-time operating voltage frequency f of the synchronized object x ；
A voltage phase angle calculation module configured to calculate a real-time voltage phase angle phi of a reference line and a synchronized object on a power grid system side under the same reference in response to receiving an external quasi-synchronization closing instruction signal s And phi x ；
A non-mains frequency voltage phase angle correction module configured to correct the phase angle according to f s And f x Judging whether any voltage on two sides of the grid-connected point operates under the non-power frequency condition, if so, correcting the real-time voltage phase angle of the corresponding voltage by using the real-time operating voltage frequency of the corresponding voltage;
and a quasi-synchronous closing control module configured to be based on f s 、f x And determining the quasi-synchronous closing time by the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing.
The specific functional implementation of each functional module above refers to the relevant content in embodiment 1.
Example 3
Based on the same inventive concept as embodiments 1 and 2, this embodiment introduces a quasi-synchronous closing system considering frequency fluctuation, which includes a processor and a memory, wherein the memory stores a plurality of instructions, and the instructions are suitable for being loaded by the processor and executing the aforementioned quasi-synchronous closing method considering frequency fluctuation.
In conclusion, the method and the device can reliably avoid the influence of asynchronous sampling on voltage phase angle calculation under the condition of frequency fluctuation, improve the accuracy of quasi-synchronous closing, reduce the damage of non-synchronous closing on power equipment in a power grid, and improve the safety and the reliability of a power system.
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.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (8)
1. A quasi-synchronous switching-on method considering frequency fluctuation is characterized by comprising the following steps:
acquiring real-time operating voltage frequency f of reference line on power grid system side s And real-time operating voltage frequency f of the synchronized object x ；
Responding to the received external quasi-synchronous closing instruction signal, and calculating the real-time voltage phase angle phi of the reference line and the synchronized object under the same reference s And phi x ；
According to f s And f x Judging whether any voltage on two sides of the grid-connected point operates under the non-power frequency condition, if so, correcting the real-time voltage phase angle of the corresponding voltage by using the real-time operating voltage frequency of the corresponding voltage;
based on f s 、f x Determining the quasi-synchronous closing time by the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing;
the method comprises the following steps of correcting a real-time voltage phase angle by utilizing a real-time running voltage frequency for a power grid system side reference line or a synchronized object with a voltage running under the non-power frequency condition, and utilizing the following formula:
wherein phi is the real-time voltage phase angle, phi' is the corrected real-time voltage phase angle, phi ERR Is a voltagePhase angle deviation, a represents fixed deviation error, b represents rotation deviation error, N is the number of sampling points per cycle under power frequency, lambda is the frequency deviation rate of the corrected voltage, f is the frequency of the corrected voltage, f 0 The frequency is the power frequency voltage frequency;
the radicals based on f s 、f x The corrected real-time voltage phase angle determines the quasi-synchronous closing moment, and sends a closing command at the quasi-synchronous closing moment to perform quasi-synchronous closing, and the method comprises the following steps:
calculating the acceleration of the frequency difference between the reference line voltage on the side of the power grid system and the voltage of the synchronized object, wherein the formula is as follows:
in the formula (f) s.last And f x.last Respectively the frequency, t, of the voltage at both sides of the grid-connected point obtained at the previous moment δ Is the time between two calculations;
calculating the corrected phase difference phi between the reference line voltage of the power grid system side and the voltage of the synchronized object δ ；
Predicting the phase difference of voltages on two sides of a grid-connected point after the leading time of closing, and if the following inequality is met, sending a closing command:
in the formula, t dq 、φ gd 、φ set The preset leading time of closing, fixed phase difference and the fixed value of the angular difference allowing closing are respectively.
2. The method of claim 1, further comprising: responding to the received external quasi-synchronous closing instruction signal, calculating the frequency difference f of the voltages at two sides of the grid-connected point δ ：
f δ ＝|f s -f x |
Judgment of f δ And if the frequency difference is larger than the preset frequency difference threshold value, closing is not allowed.
3. A method according to claim 1 or 2, wherein the grid system side reference line is a grid system side line of similar magnitude and phase of the phase voltage or line voltage and the voltage of the contemporaneous object, preset or identified by the quasi contemporaneous device.
4. Method according to claim 1 or 2, characterized in that the real-time operating voltage frequency f of the reference line s And real-time operating voltage frequency f of the synchronized object x And calculating in real time by using a frequency measurement algorithm.
5. The method as claimed in claim 1 or 2, wherein a DFT algorithm based on synchronous sampling with power frequency is adopted to calculate the real-time voltage phase angle phi of the reference line on the side of the power grid system and the synchronized object under the same reference s And phi x 。
6. The method of claim 1, wherein the corrected phase difference φ is calculated δ Neglecting the rotation deviation error, and correcting the phase difference phi δ Calculated according to the following formula:
in the formula of lambda s And λ x Respectively, the frequency deviation rate of the voltage across the grid-connected point.
7. A quasi-synchronous closing apparatus considering frequency fluctuation, comprising:
a voltage frequency calculation module configured to obtain a real-time operating voltage frequency f of a grid system-side reference line s And real-time operating voltage frequency f of the synchronized object x ；
A voltage phase angle calculation module configured to calculate a real-time voltage phase angle phi of a reference line and a synchronized object on a power grid system side under the same reference in response to receiving an external quasi-synchronization closing instruction signal s And phi x ；
A non-mains frequency voltage phase angle correction module configured to correct the phase angle according to f s And f x Judging whether any voltage on two sides of the grid-connected point operates under the non-power frequency condition, if so, correcting the real-time voltage phase angle of the corresponding voltage by using the real-time operating voltage frequency of the corresponding voltage;
and a quasi-synchronous closing control module configured to be based on f s 、f x Determining the quasi-synchronous closing time by the corrected real-time voltage phase angle, and sending a closing command at the quasi-synchronous closing time to perform quasi-synchronous closing;
the non-power frequency voltage phase angle correction module corrects a real-time voltage phase angle by utilizing a real-time running voltage frequency for a power grid system side reference line or a synchronized object of which the voltage runs under the non-power frequency condition, and the following formula is utilized:
wherein phi is the real-time voltage phase angle, phi' is the corrected real-time voltage phase angle, phi ERR The phase angle deviation of the voltage, a represents a fixed deviation error, b represents a rotation deviation error, N is the number of sampling points per cycle under power frequency, lambda is the frequency deviation rate of the corrected voltage, f is the frequency of the corrected voltage, f 0 The frequency is the power frequency voltage frequency;
the quasi-synchronous closing control module is based on f s 、f x The corrected real-time voltage phase angle determines the quasi-synchronous closing moment, and sends a closing command at the quasi-synchronous closing moment to perform quasi-synchronous closing, and the method comprises the following steps:
calculating the acceleration of the frequency difference between the reference line voltage on the side of the power grid system and the voltage of the synchronized object, wherein the formula is as follows:
in the formula (f) s.last And f x.last Respectively the frequency, t, of the voltage at both sides of the grid-connected point obtained at the previous moment δ Is the time between two calculations;
calculating the corrected phase difference phi between the reference line voltage of the power grid system side and the voltage of the synchronized object δ ；
Predicting the phase difference of the voltages at two sides of the grid-connected point after the leading time of closing, and if the following inequality is met, sending a closing command:
in the formula, t dq 、φ gd 、φ set The preset leading time of closing, fixed phase difference and the fixed value of the angular difference allowing closing are respectively.
8. A quasi-synchronous closing system considering frequency fluctuation, comprising a processor and a memory, wherein the memory stores a plurality of instructions, and the instructions are suitable for being loaded by the processor and executing the quasi-synchronous closing method considering frequency fluctuation according to any one of claims 1 to 6.
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