Electrical quantity phasor calculation method and system for full-power variable speed pumped storage unit protection

Abstract

This invention discloses a method for calculating electrical phasors for the protection of full-power variable-speed pumped-storage units, comprising: during the operation of the unit protection device, acquiring current and / or voltage sampling values ​​within a preset time period prior to the current moment, forming a sampling value array; after the unit protection is activated, using the Fourier power frequency algorithm to calculate the real and imaginary parts of the current and voltage phasors at the current moment; using the current and / or voltage sampling values ​​within the preset time period prior to the current moment, employing the Fourier transform frequency measurement principle to calculate the current frequency of the unit; calculating the phase of the current phasor and / or voltage phasor at the current moment based on the real and imaginary parts and the current frequency; and calculating the amplitude of the current phasor and / or voltage phasor at the current moment based on the real and imaginary parts, the current frequency, and the phase. By measuring the frequency in real time and correcting the phase and amplitude, the accuracy of the current and voltage phasors is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, specifically to an electrical quantity phasor calculation method, system, and medium for the protection of full-power variable speed pumped storage units. Background Technology

[0002] Variable-speed pumped-storage units are connected to the system via converters. The unit-side frequency is not a fixed 50Hz; its frequency variation range is large. Traditional discrete Fourier transforms based on fixed frequencies are used to calculate the current and voltage phasors on the computer side.

[0003] The Discrete Fourier Transform (DFT) is a mathematical tool for transforming discrete signals from the time domain to the frequency domain. Its core function is to analyze the sinusoidal components of different frequencies contained in a signal, including their amplitude and phase. Its calculation formula is:

[0004]

[0005] In the formula, It is a complex array, which is the sampled signal. The result of the transformation is that half of the data in the complex array is conjugate to the other half. Therefore, we only need to focus on... The first half of the data is sufficient. Among them, This represents the fundamental frequency component in the sampled signal. The amplitude represents the amplitude of the fundamental frequency component in the sampled signal. The phase is the phase of the fundamental frequency component in the sampled signal.

[0006] The power frequency of my country's power system is 50Hz. Existing protection devices that require AC current and voltage phasors are all based on the premise of a power frequency of 50Hz, setting a fixed data window and obtaining a fixed number of sampling points for Fourier transform.

[0007] In relay protection devices, the Fourier power frequency algorithm is used to calculate the phasor values ​​of current and voltage. Its sampling frequency is fixed, and the number of sampling points in one sampling period is N. When the signal frequency deviates from the power frequency, the number of sampling points in one period is no longer N, resulting in a larger error in the calculated current phasor. This can easily cause the protection to fail to operate or malfunction, affecting the reliability of the protection. Since the frequency of full-power variable-speed pumped storage units is not a fixed 50Hz, but rather varies greatly, if the traditional current and voltage phasor calculation method is still used to obtain the current and voltage, the error will be large, affecting the protection performance of the existing units. Summary of the Invention

[0008] The purpose of this invention is to provide a method, system, and medium for calculating electrical phasors for the protection of full-power variable-speed pumped storage units. By using frequency correction, the invention achieves accurate calculation of electrical phasors and improves the adaptability of existing unit protection systems to full-power variable-speed pumped storage units.

[0009] This invention is achieved through the following technical solution:

[0010] In a first aspect, the first embodiment of the present invention provides a method for calculating electrical phasor quantities for the protection of a full-power variable-speed pumped-storage unit, comprising:

[0011] During the operation of the unit protection device, the current sampling value and / or voltage sampling value within a preset time period before the current moment are acquired to form a sampling value array;

[0012] After the unit protection is activated, the Fourier power frequency algorithm is used to calculate the real and imaginary parts of the current and the real and imaginary parts of the voltage phasor at the current moment.

[0013] Using the current and / or voltage sample values ​​within a preset time period before the current moment, the current frequency of the computer group is determined by applying the Fourier transform frequency measurement principle.

[0014] Calculate the phase of the current phasor and / or the phase of the voltage phasor at the current moment based on the real part, the imaginary part, and the current frequency;

[0015] Calculate the magnitude of the current phasor and / or the magnitude of the voltage phasor at the current moment based on the real part, imaginary part, current frequency, and phase.

[0016] Furthermore, the number of sampling points in the sampling value array is related to the sampling frequency, with a sampling frequency of 4kHz, a preset duration of 40ms, and a sampling number of 160.

[0017] Furthermore, the formula for calculating the phase of the current phasor at the current moment is:

[0018] ;

[0019] in, The phase of the current phasor at the current moment. Let be the real part of the current phasor at the current moment. f is the imaginary part of the current phasor at the current moment, and f is the current frequency.

[0020] Furthermore, the formula for calculating the magnitude of the current phasor at the current moment is:

[0021] ;

[0022] Where I is the magnitude of the current phasor. and Based on and The obtained current phasor amplitude, and The calculation formula is as follows:

[0023] ;

[0024] ;

[0025] in, For power frequency, It is the power frequency cycle.

[0026] Furthermore, =50 Hz Substituting =20 ms into the following values: and The calculation formula yields:

[0027] ;

[0028] .

[0029] Furthermore, according to and The formula for calculating the current phasor magnitude I at the current moment is:

[0030] .

[0031] Furthermore, the formula for calculating the phase of the voltage phasor at the current moment is:

[0032] ;

[0033] in, The phase of the voltage phasor at the current moment. The real part of the voltage phasor at the current moment, f is the imaginary part of the voltage phasor at the current moment, and f is the current frequency.

[0034] Furthermore, the formula for calculating the magnitude of the voltage phasor at the current moment is:

[0035] ;

[0036] Where U is the magnitude of the voltage phasor at the current moment.

[0037] Secondly, another embodiment of the present invention provides an electrical phasor calculation system for the protection of a full-power variable-speed pumped-storage unit, used to implement the method described in the first embodiment above, including:

[0038] The sampling parameter acquisition module is used to acquire the current sampling value and / or voltage sampling value within a preset time period before the current moment during the operation of the unit protection device, and form a sampling value array.

[0039] The real and virtual parts calculation module uses the Fourier power frequency algorithm to calculate the real and virtual parts of the current and the real and virtual parts of the voltage phasor at the current moment after the unit protection is started.

[0040] The frequency calculation module uses the current and / or voltage sampling values ​​within a preset time period before the current moment, and adopts the Fourier transform frequency measurement principle to determine the current frequency of the computer group.

[0041] The phase calculation module is used to calculate the phase of the current phasor and / or the phase of the voltage phasor at the current moment based on the real part, the imaginary part and the current frequency;

[0042] The amplitude calculation module is used to calculate the amplitude of the current phasor and / or the amplitude of the voltage phasor at the current moment based on the real part, imaginary part, current frequency, and phase.

[0043] Thirdly, another embodiment of the present invention provides a computer-readable storage medium storing a computer program, the computer program including program instructions, which, when executed by a processor, cause the processor to perform the method described in the first embodiment above.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] This invention provides a method, system, and medium for calculating electrical phasors in the protection of full-power variable-speed pumped-storage units. Addressing the wide frequency variation characteristic of full-power variable-speed pumped-storage units, this method solves the problem of large calculation errors in traditional fixed-50Hz Fourier algorithms when there are frequency deviations by measuring the frequency in real time and correcting the phase and amplitude. This significantly improves the accuracy of current and voltage phasors. The improved phasor calculation accuracy directly reduces the risk of protection devices failing to operate or maloperating due to electrical quantity errors, enhancing the reliability and safety of relay protection for full-power variable-speed pumped-storage units. This method is designed for operating conditions where the unit's frequency is not fixed and varies widely, enabling it to adapt to wide-frequency operating scenarios and significantly improving the adaptability of existing protection devices to full-power variable-speed pumped-storage units. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0047] Figure 1 A flowchart of an electrical quantity phasor calculation method for protection of a full-power variable-speed pumped-storage unit provided in the first embodiment of the present invention;

[0048] Figure 2 The present invention provides a structural block diagram of an electrical quantity phasor calculation system for the protection of a full-power variable-speed pumped-storage unit. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0050] like Figure 1 As shown, the first embodiment of the present invention provides a method for calculating electrical phasors for the protection of a full-power variable-speed pumped-storage unit, comprising the following steps:

[0051] Step 1: During the operation of the unit protection device, acquire the current sampling value and / or voltage sampling value within a preset time period before the current moment, and form a sampling value array;

[0052] Step 2: After the unit protection is activated, the real and imaginary parts of the current and the real and imaginary parts of the voltage phasor at the current moment are calculated using the Fourier power frequency algorithm.

[0053] Step 3: Using the current sampling value and / or voltage sampling value within the preset time period before the current moment, the current frequency of the computer group is determined by the Fourier transform frequency measurement principle;

[0054] Step 4: Calculate the phase of the current phasor and / or the phase of the voltage phasor at the current moment based on the real part, imaginary part, and current frequency;

[0055] Step 5: Calculate the magnitude of the current phasor and / or the magnitude of the voltage phasor at the current moment based on the real part, imaginary part, current frequency, and phase.

[0056] Specifically, during the operation of the unit's protection device, the sampled values ​​of current and voltage within 40ms prior to the current moment are recorded and saved, and recorded as a sampled value group. and N is the total number of points stored, and its size is related to the sampling frequency. If the sampling frequency is 4kHz, then N=160.

[0057] After the unit protection is activated, the real and imaginary parts of the current phasor at the current moment are calculated using the Fourier power frequency algorithm, and denoted as follows: , The real and imaginary parts of the voltage phasor at the current moment are calculated using the Fourier power frequency algorithm, and are denoted as follows: , Using a fixed 50Hz frequency as the calculation benchmark, a power frequency period of 20ms, and a frequency of 4kHz, the number of sampling points within one power frequency period is 80, and a current sampling sequence for one power frequency period is obtained. The protection device takes the discrete current sampling value of the most recent power frequency period at the current moment, forming a sequence: i(0), i(1), i(2), ..., i(k).

[0058] Where k = 0, 1, 2, ..., 79, and i(k) is the instantaneous current value at the kth sampling point.

[0059] The real part corresponds to the cosine component of the fundamental component, calculated using the following formula:

[0060] ,

[0061] Where N=80, The cosine coefficient corresponding to the fixed 50Hz power frequency is not affected by the actual frequency variation of the group.

[0062] The imaginary part corresponds to the sinusoidal component of the fundamental component, and its calculation formula is:

[0063] ,

[0064] In the formula, the negative sign represents the standard form of the Fourier algorithm in the field of relay protection. The sine coefficient is fixed at a 50Hz power frequency.

[0065] Similarly, the real and imaginary parts of the voltage phasor at the current moment are calculated using the Fourier power frequency algorithm, and are denoted as follows: , The calculation formula is:

[0066] ,

[0067] ,

[0068] According to the above formula, we obtain... , , , The real and imaginary parts are calculated based on a fixed 50Hz power frequency, without considering the actual frequency deviation of the unit, which results in calculation errors. Therefore, subsequent frequency measurement and phase and amplitude correction are required to obtain accurate current and voltage phasors.

[0069] Acquire a 40ms sampling data window: Based on the current sampling values ​​in the previous 40ms, form a sampling sequence of length 160 points, i(0), i(1), i(2), ..., i( ), =0, 1, 2 ... 159.

[0070] For the first 80 points i(0), i(1), i(2), ..., i(79), the fundamental (50Hz) component within the data window is extracted using Discrete Fourier Transform (DFT), and the real part of the fundamental component is calculated for each. and the virtual part :

[0071] ;

[0072] ,

[0073] Where N1=80.

[0074] Calculate the fundamental phase angle 1: from the real part and the virtual part The phase angle φ1 is obtained as follows:

[0075] ,

[0076] For the last 80 points i(80), i(81), i(82), ..., i(159), the fundamental (50Hz) component within the data window is extracted using Discrete Fourier Transform (DFT), and the real part of the fundamental component is calculated for each point. and the virtual part :

[0077] ;

[0078] ,

[0079] Where N1=80.

[0080] Calculate the fundamental phase angle 2: from the real part and the virtual part The phase angle φ2 is obtained:

[0081] ,

[0082] Current actual frequency of computer group :

[0083] .

[0084] get , and current frequency Then, calculate the phase of the current phasor at the current moment. The calculation formula can be expressed as:

[0085] ,

[0086] In the formula, The phase of the current phasor. It is the power frequency, i.e., 50 Hz. The power frequency period is 20 ms. Substituting the specific values ​​of the power frequency and the power frequency period into the above formula, we can obtain the formula for calculating the current phase:

[0087] .

[0088] The formula for calculating the magnitude of the current phasor at the current moment is:

[0089] ,

[0090] In the formula, I is the magnitude of the current phasor. and Based on and The obtained current phasor amplitude can be calculated using the following formula:

[0091] ,

[0092] ,

[0093] The above and In the calculation formula, It is the power frequency, i.e., 50 Hz. This is the power frequency period, i.e., 20 ms. Substituting the specific values ​​of into... and The calculation formula includes:

[0094] ,

[0095] .

[0096] In summary, the formula for calculating the current phasor amplitude at the current moment is:

[0097] .

[0098] Similarly, according to , Given the current frequency f, calculate the phase of the voltage phasor at the current moment. The calculation formula can be expressed as:

[0099] ,

[0100] in, The phase of the voltage phasor.

[0101] Based on the phase of the voltage phasor Calculate the magnitude of the voltage phasor at the current moment. The calculation formula is:

[0102] .

[0103] This invention provides a method for calculating electrical phasors for the protection of full-power variable-speed pumped-storage units. Addressing the characteristic of large frequency variations in full-power variable-speed pumped-storage units, this method solves the problem of large calculation errors in traditional fixed-50Hz Fourier algorithms when there are frequency deviations by measuring the frequency in real time and correcting for phase and amplitude. This significantly improves the accuracy of current and voltage phasors. Improved phasor calculation accuracy directly reduces the risk of protection devices failing to operate or maloperating due to electrical quantity errors, enhancing the reliability and safety of relay protection for full-power variable-speed pumped-storage units. This method is designed for operating conditions where the unit's frequency is not fixed and varies widely, enabling it to adapt to wide-frequency operating scenarios and significantly improving the adaptability of existing protection devices to full-power variable-speed pumped-storage units.

[0104] like Figure 2 As shown, another embodiment of the present invention provides an electrical quantity phasor calculation system for the protection of a full-power variable-speed pumped-storage unit, comprising: a sampling parameter acquisition module, used to acquire current sampling values ​​and / or voltage sampling values ​​within a preset time period before the current moment during the operation of the unit protection device, forming a sampling value array; a real and imaginary part calculation module, used to calculate the real and imaginary parts of the current and voltage phasors at the current moment using the Fourier power frequency algorithm after the unit protection is started; a frequency calculation module, used to calculate the current frequency of the unit using the current sampling values ​​and / or voltage sampling values ​​within a preset time period before the current moment, employing the Fourier transform frequency measurement principle; a phase calculation module, used to calculate the phase of the current phasor and / or the phase of the voltage phasor at the current moment based on the real and imaginary parts and the current frequency; and an amplitude calculation module, used to calculate the amplitude of the current phasor and / or the amplitude of the voltage phasor at the current moment based on the real and imaginary parts, the current frequency, and the phase.

[0105] The execution process of each module can be carried out according to the steps of the electrical quantity phasor calculation method for the protection of full-power variable speed pumped storage units provided in the first embodiment, and will not be described in detail in this embodiment.

[0106] The electrical quantity phasor calculation system for the protection of full-power variable-speed pumped-storage units and the electrical quantity phasor calculation method for the protection of full-power variable-speed pumped-storage units provided in this invention embodiment are based on the same inventive concept and have the same beneficial effects, and will not be described again here.

[0107] The present invention also provides an embodiment of a computer-readable storage medium storing a computer program, the computer program including program instructions, which, when executed by a processor, cause the processor to perform the method described in the first embodiment above.

[0108] The computer-readable storage medium can be an internal storage unit of the terminal described in the foregoing embodiments, such as the terminal's hard drive or memory. The computer-readable storage medium can also be an external storage device of the terminal, such as a plug-in hard drive, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the terminal. Furthermore, the computer-readable storage medium can include both internal storage units and external storage devices of the terminal. The computer-readable storage medium is used to store the computer program and other programs and data required by the terminal. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0109] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0110] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the terminals and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0111] In the several embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices or units, or may be electrical, mechanical or other forms of connection.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for calculating electrical phasors for the protection of full-power variable-speed pumped-storage units, characterized in that, include: During the operation of the unit protection device, the current sampling value and / or voltage sampling value within a preset time period before the current moment are acquired to form a sampling value array; After the unit protection is activated, the Fourier power frequency algorithm is used to calculate the real and imaginary parts of the current and the real and imaginary parts of the voltage phasor at the current moment. Using the current and / or voltage sample values ​​within a preset time period before the current moment, the current frequency of the computer group is determined by applying the Fourier transform frequency measurement principle. Calculate the phase of the current phasor and / or the phase of the voltage phasor at the current moment based on the real part, the imaginary part, and the current frequency; Calculate the magnitude of the current phasor and / or the magnitude of the voltage phasor at the current moment based on the real part, imaginary part, current frequency, and phase.

2. The method of claim 1, wherein, The number of sampling points in the sampling value array is related to the sampling frequency. The sampling frequency is 4kHz, the preset duration is 40ms, and the number of sampling points is 160.

3. The method of claim 1, wherein, The formula for calculating the phase of the current phasor at the current moment is: ； wherein is the phase of the current phasor at the current time instant, is the real part of the current phasor at the current time instant, is the imaginary part of the current phasor at the current time instant, and f is the current frequency.

4. The method of claim 3, wherein, The formula for calculating the magnitude of the current phasor at the current moment is: ； Where I is the magnitude of the current phasor. and Based on and The obtained current phasor amplitude, and The calculation formula is as follows: ； ； in, For power frequency, It is the power frequency cycle.

5. The method of claim 4, wherein, Substituting = 50 Hz, = 20 ms into the calculation formulas of and respectively gives: ； 。 6. The method of claim 5, wherein, According to and The calculation formula of the current phasor amplitude I at the current moment is: 。 7. The method of claim 1, wherein, The formula for calculating the phase of the voltage phasor at the current moment is: ； in, The phase of the voltage phasor at the current moment. The real part of the voltage phasor at the current moment, f is the imaginary part of the voltage phasor at the current moment, and f is the current frequency.

8. The method of claim 7, wherein, The formula for calculating the magnitude of the voltage phasor at the current moment is: ； Where U is the magnitude of the voltage phasor at the current moment.

9. An electrical quantity phasor calculation system for full power variable speed pumped storage unit protection, characterized in that, For implementing the method as described in any one of claims 1-8, comprising: The sampling parameter acquisition module is used to acquire the current sampling value and / or voltage sampling value within a preset time period before the current moment during the operation of the unit protection device, and form a sampling value array. The real and virtual parts calculation module uses the Fourier power frequency algorithm to calculate the real and virtual parts of the current and the real and virtual parts of the voltage phasor at the current moment after the unit protection is started. The frequency calculation module uses the current and / or voltage sampling values ​​within a preset time period before the current moment, and adopts the Fourier transform frequency measurement principle to determine the current frequency of the computer group. The phase calculation module is used to calculate the phase of the current phasor and / or the phase of the voltage phasor at the current moment based on the real part, the imaginary part and the current frequency; The amplitude calculation module is used to calculate the amplitude of the current phasor and / or the amplitude of the voltage phasor at the current moment based on the real part, imaginary part, current frequency, and phase.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, the computer program including program instructions that, when executed by a processor, cause the processor to perform the method as described in any one of claims 1-8.

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