Photovoltaic power generation system ferromagnetic resonance overvoltage suppression method based on harmonic detection

Abstract

The invention discloses a photovoltaic power generation system ferromagnetic resonance overvoltage suppression method based on harmonic detection. The method comprises the following steps: 1) obtaining ferromagnetic resonance frequency domain characteristics influenced by photovoltaic power generation harmonic waves in a photovoltaic power generation system under different working conditions; 2) comparing and analyzing the frequency domain characteristics of the ferromagnetic resonance influenced by the photovoltaic power generation harmonic waves and the frequency domain characteristics of the ferromagnetic resonance not influenced by the photovoltaic power generation harmonic waves, establishing a mapping relation between the harmonic waves generated by photovoltaic power generation and the ferromagnetic resonance, and writing the mapping relation into a photovoltaic power generation ferromagnetic resonance frequency domain characteristic database; 3) acquiring voltage frequency domain characteristics of ferromagnetic resonance of the photovoltaic power generation system in actual work; and 4) comparing and analyzing the voltage frequency domain characteristics of the ferromagnetic resonance of the photovoltaic power generation system in actual work with data in the frequency domain characteristic database of the ferromagnetic resonance of the photovoltaic power generation system, and if the ferromagnetic resonance overvoltage occurs in the photovoltaic power generation system, starting a suppression device to suppress the ferromagnetic resonance overvoltage of the photovoltaic power generation system. According to the invention, safe and stable operation of the photovoltaic power generation system is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of ferromagnetic resonance overvoltage protection for photovoltaic power generation systems, and in particular to a method for suppressing ferromagnetic resonance overvoltage for photovoltaic power generation systems based on harmonic detection. Background Art

[0002] With the rapid development of new energy technologies, photovoltaic power generation has been widely used as a clean energy. Photovoltaic power generation is a technology that uses the photovoltaic effect of semiconductor interfaces to directly convert light energy into electrical energy. It mainly consists of three parts: solar panels, controllers and inverters. The principle of photovoltaic power generation is that when photons irradiate metals, their energy can be completely absorbed by an electron in the metal. The energy absorbed by the electron is large enough to overcome the Coulomb force inside the metal atoms to do work, escape from the metal surface and become photoelectrons.

[0003] However, photovoltaic power generation systems may encounter ferromagnetic resonance during operation. Ferromagnetic resonance is a form of self-excited oscillation in power systems. It is a continuous, high-amplitude resonant overvoltage phenomenon caused by the saturation of ferromagnetic inductors such as transformers and voltage transformers. Although many detuning measures have been taken in power grid operation, ferromagnetic resonance accidents in small current grounding systems still occur frequently. Due to the influence of harmonics, the ferromagnetic resonance in photovoltaic power generation systems is significantly different from traditional ferromagnetic resonance in frequency domain characteristics, which leads to increased ferromagnetic resonance hazards. Summary of the invention

[0004] The purpose of the present invention is to provide a method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection, comprising the following steps:

[0005] 1) Obtain the frequency domain characteristics of ferromagnetic resonance in photovoltaic power generation systems affected by photovoltaic power generation harmonics under different working conditions.

[0006] 2) Compare and analyze the frequency domain characteristics of ferromagnetic resonance affected by photovoltaic power generation harmonics and the frequency domain characteristics of ferromagnetic resonance not affected by photovoltaic power generation harmonics, establish a mapping relationship between the harmonics generated by photovoltaic power generation and ferromagnetic resonance, and write it into the photovoltaic power generation ferromagnetic resonance frequency domain feature database.

[0007] 3) Obtain the voltage-frequency characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work.

[0008] 4) Compare and analyze the voltage frequency domain characteristics of ferromagnetic resonance in the actual photovoltaic power generation system with the data in the photovoltaic power generation ferromagnetic resonance frequency domain characteristic database. If ferromagnetic resonance overvoltage occurs in the photovoltaic power generation system, the suppression device is started to suppress the ferromagnetic resonance overvoltage of the photovoltaic power generation system.

[0009] Furthermore, the step of obtaining the ferromagnetic resonance frequency domain characteristics affected by photovoltaic power generation harmonics in the photovoltaic power generation system under different working conditions includes:

[0010] 1.1) Establish an electromagnetic transient model of the photovoltaic power generation system.

[0011] 1.2) Different operating conditions are preset in the electromagnetic transient model of the photovoltaic power generation system, and ferromagnetic resonance is excited to obtain the voltage time domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under the corresponding operating conditions.

[0012] 1.3) The voltage time-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are analyzed by fast Fourier decomposition, and the frequency-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are obtained.

[0013] Furthermore, the photovoltaic power generation system electromagnetic transient model includes a photovoltaic power generation model and a photovoltaic power generation system substation model.

[0014] Furthermore, the photovoltaic power generation model includes photovoltaic array and MPPT modeling, and inverter non-ideal model.

[0015] Furthermore, the photovoltaic power generation system substation model includes a line model, a transformer model, a PT model, and a capacitor reactor model.

[0016] Furthermore, the method for comparing and analyzing the ferromagnetic resonance frequency domain characteristics affected by photovoltaic power generation harmonics and the ferromagnetic resonance frequency domain characteristics not affected by photovoltaic power generation harmonics includes data preprocessing, feature extraction, and data mining.

[0017] Furthermore, the step of obtaining the voltage frequency domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system in actual work includes:

[0018] 3.1) Obtain the voltage time domain characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work.

[0019] 3.2) The voltage time domain characteristics of the ferromagnetic resonance in the actual photovoltaic power generation system are analyzed by fast Fourier decomposition, and the voltage frequency domain characteristics of the ferromagnetic resonance in the actual photovoltaic power generation system are obtained.

[0020] Furthermore, the calculation formula of the fast Fourier decomposition is as follows:

[0021] f(t)=∫F(ω)e iωt dω (1)

[0022] Where ω is the frequency, f(t) is the frequency domain analytical expression obtained by Fourier decomposition, F(ω) is the amplitude of the sine wave with frequency ω, and e iωt is a complex exponential function.

[0023] The technical effect of the present invention is unquestionable. The present invention provides a reasonable and effective harmonic detection method for suppressing ferromagnetic resonance overvoltage in photovoltaic power generation systems, determines the characteristic quantity of photovoltaic harmonics on ferromagnetic resonance, and specifically suppresses overvoltage according to different harmonic actions, thereby ensuring the safe and stable operation of photovoltaic power generation systems.

[0024] The core technology of the present invention is to simulate the system operation status under different working conditions by establishing the electromagnetic transient model and photovoltaic power generation model of the photovoltaic power generation system, and obtain the time-frequency domain characteristics of ferromagnetic resonance by harmonic injection. Through data preprocessing, feature extraction and data mining, the harmonic content of ferromagnetic resonance and traditional ferromagnetic resonance in the photovoltaic power generation system is compared and analyzed, and the harmonic content of the voltage in the actual system is detected in real time to identify whether ferromagnetic resonance occurs in the system.

[0025] In actual work, the present invention can obtain the time domain characteristics of the voltage in real time and convert them into frequency domain characteristics through fast Fourier transform. By comparing and analyzing the working data with the characteristic data in the database, the suppression device can be ensured to operate quickly and stably, thereby effectively suppressing the ferromagnetic resonance overvoltage and ensuring the safe and stable operation of the photovoltaic power generation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the ferromagnetic resonance overvoltage suppression device for the photovoltaic power generation system of the present invention;

[0027] Figure 2 A flow chart for obtaining the characteristic quantity of photovoltaic output harmonics that induce ferromagnetic resonance in the present invention;

[0028] Figure 3 It is the PT nonlinear inductance φ-i characteristic curve;

[0029] Figure 4 The φ-i characteristic curve of the main transformer;

[0030] Figure 5 This is a comparison chart of the frequency domain characteristics of ferromagnetic resonance and traditional ferromagnetic resonance in photovoltaic power generation system; Figure 5 (a) is a schematic diagram of the frequency domain characteristics of traditional ferromagnetic resonance; Figure 5 (b) is a schematic diagram of the frequency domain characteristics of ferromagnetic resonance in a photovoltaic power generation system;

[0031] Figure 6 This is a comparison diagram of the system voltage before and after the suppression device is activated; Figure 6 (a) is a schematic diagram of the system voltage waveform before suppression; Figure 6 (b) is a schematic diagram of the system voltage waveform after suppression;

[0032] Figure 7 This is a schematic diagram of the photovoltaic power generation model;

[0033] Figure 8 Schematic diagram of the photovoltaic power generation system substation model. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0035] Embodiment 1:

[0036] See also Figures 1 to 8 , a method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection, comprising the following steps:

[0037] 1) Obtain the frequency domain characteristics of ferromagnetic resonance in photovoltaic power generation systems affected by photovoltaic power generation harmonics under different working conditions.

[0038] 2) Compare and analyze the frequency domain characteristics of ferromagnetic resonance affected by photovoltaic power generation harmonics and the frequency domain characteristics of ferromagnetic resonance not affected by photovoltaic power generation harmonics, establish a mapping relationship between the harmonics generated by photovoltaic power generation and ferromagnetic resonance, and write it into the photovoltaic power generation ferromagnetic resonance frequency domain feature database.

[0039] 3) Obtain the voltage-frequency characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work.

[0040] 4) Compare and analyze the voltage frequency domain characteristics of ferromagnetic resonance in the actual photovoltaic power generation system with the data in the photovoltaic power generation ferromagnetic resonance frequency domain characteristic database. If ferromagnetic resonance overvoltage occurs in the photovoltaic power generation system, the suppression device is started to suppress the ferromagnetic resonance overvoltage of the photovoltaic power generation system.

[0041] Embodiment 2:

[0042] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in Example 1. Further, the step of obtaining the ferromagnetic resonance frequency domain characteristics of the photovoltaic power generation system affected by photovoltaic power generation harmonics under different working conditions includes:

[0043] 1.1) Establish an electromagnetic transient model of the photovoltaic power generation system.

[0044] 1.2) Different operating conditions are preset in the electromagnetic transient model of the photovoltaic power generation system, and ferromagnetic resonance is excited to obtain the voltage time domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under the corresponding operating conditions.

[0045] 1.3) The voltage time-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are analyzed by fast Fourier decomposition, and the frequency-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are obtained.

[0046] Embodiment 3:

[0047] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection. The main technical content is shown in any one of Examples 1 to 2. Furthermore, the electromagnetic transient model of the photovoltaic power generation system includes a photovoltaic power generation model and a photovoltaic power generation system substation model.

[0048] Embodiment 4:

[0049] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection. The main technical content is shown in any one of Examples 1 to 3. Furthermore, the photovoltaic power generation model includes photovoltaic array and MPPT modeling, and an inverter non-ideal model.

[0050] Embodiment 5:

[0051] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection. The main technical content is shown in any one of Examples 1 to 4. Furthermore, the photovoltaic power generation system substation model includes a line model, a transformer model, a PT model, and a capacitor reactor model.

[0052] Embodiment 6:

[0053] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in any one of Examples 1 to 5. Furthermore, the method for comparing and analyzing the ferromagnetic resonance frequency domain characteristics affected by photovoltaic power generation harmonics and the ferromagnetic resonance frequency domain characteristics not affected by photovoltaic power generation harmonics includes data preprocessing, feature extraction, and data mining.

[0054] Embodiment 7:

[0055] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in any one of Embodiments 1 to 6. Further, the step of obtaining the voltage frequency domain characteristics of ferromagnetic resonance in the photovoltaic power generation system in actual work includes:

[0056] 3.1) Obtain the voltage time domain characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work.

[0057] 3.2) The voltage time domain characteristics of the ferromagnetic resonance in the actual photovoltaic power generation system are analyzed by fast Fourier decomposition, and the voltage frequency domain characteristics of the ferromagnetic resonance in the actual photovoltaic power generation system are obtained.

[0058] Embodiment 8:

[0059] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in any one of Embodiments 1 to 7. Further, the calculation formula of the fast Fourier decomposition is as follows:

[0060] f(t)=∫F(ω)e iωt dω (1)

[0061] Where ω is the frequency, f(t) is the frequency domain analytical expression obtained by Fourier decomposition, F(ω) is the amplitude of the sine wave with frequency ω, and e iωt is a complex exponential function.

[0062] Embodiment 9:

[0063] See also Figures 1 to 8 , a method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection, comprising the following steps:

[0064] 1) Obtain the frequency domain characteristics of ferromagnetic resonance in photovoltaic power generation systems affected by photovoltaic power generation harmonics under different working conditions.

[0065] The switching frequency of the photovoltaic inverter is different, resulting in different harmonic orders, that is, different operating conditions.

[0066] 2) Compare and analyze the frequency domain characteristics of ferromagnetic resonance affected by photovoltaic power generation harmonics and the frequency domain characteristics of ferromagnetic resonance not affected by photovoltaic power generation harmonics, establish a mapping relationship between the harmonics generated by photovoltaic power generation and ferromagnetic resonance, and write it into the photovoltaic power generation ferromagnetic resonance frequency domain feature database.

[0067] Figure 5 This is a comparison of the frequency domain characteristics of ferromagnetic resonance and traditional ferromagnetic resonance in photovoltaic power generation systems. Figure 5 (b) It can be seen that the ferromagnetic resonance overvoltage amplitude in the photovoltaic power generation system is larger, so the harm is greater. Due to the influence of power supply harmonics, the ferromagnetic resonance frequency division resonance characteristics in the photovoltaic power generation system are significant, and contain 2nd, 3rd, 5th and other high-order harmonics. The action of the suppression device can be controlled according to the different harmonic contents.

[0068] The specific steps to establish the mapping relationship between the harmonics generated by photovoltaic power generation and ferromagnetic resonance are as follows: establish a photovoltaic power generation system model, conduct actual measurements under different photovoltaic power generation conditions, and establish the mapping relationship between the harmonics generated by photovoltaic power generation and ferromagnetic resonance. (That is, how many harmonics will produce corresponding resonance)

[0069] 3) Obtain the voltage-frequency characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work.

[0070] 4) Compare and analyze the voltage frequency domain characteristics of ferromagnetic resonance in the actual photovoltaic power generation system with the data in the photovoltaic power generation ferromagnetic resonance frequency domain characteristic database. If ferromagnetic resonance overvoltage occurs in the photovoltaic power generation system, the suppression device is started to suppress the ferromagnetic resonance overvoltage of the photovoltaic power generation system.

[0071] Embodiment 10:

[0072] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in Example 9. Further, the step of obtaining the ferromagnetic resonance frequency domain characteristics of the photovoltaic power generation system affected by photovoltaic power generation harmonics under different working conditions includes:

[0073] 1.1) Establish an electromagnetic transient model of the photovoltaic power generation system.

[0074] 1.2) Different operating conditions are preset in the electromagnetic transient model of the photovoltaic power generation system, and ferromagnetic resonance is excited to obtain the voltage time domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under the corresponding operating conditions.

[0075] 1.3) The voltage time-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are analyzed by fast Fourier decomposition, and the frequency-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are obtained.

[0076] Embodiment 11:

[0077] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection. The main technical content is shown in any one of Examples 9 to 10. Furthermore, the electromagnetic transient model of the photovoltaic power generation system includes a photovoltaic power generation model and a photovoltaic power generation system substation model.

[0078] Embodiment 12:

[0079] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection. The main technical content is shown in any one of Examples 9 to 11. Furthermore, the photovoltaic power generation model includes photovoltaic array and MPPT modeling, and an inverter non-ideal model.

[0080] Embodiment 13:

[0081] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection. The main technical content is shown in any one of Examples 9 to 12. Furthermore, the photovoltaic power generation system substation model includes a line model, a transformer model, a PT model, and a capacitor reactor model.

[0082] Embodiment 14:

[0083] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in any one of Examples 9 to 13. Furthermore, the method for comparing and analyzing the ferromagnetic resonance frequency domain characteristics affected by photovoltaic power generation harmonics and the ferromagnetic resonance frequency domain characteristics not affected by photovoltaic power generation harmonics includes data preprocessing, feature extraction, and data mining.

[0084] Embodiment 15:

[0085] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in any one of Embodiments 9 to 14. Further, the step of obtaining the voltage frequency domain characteristics of ferromagnetic resonance in the photovoltaic power generation system in actual work includes:

[0086] 3.1) Obtain the voltage time domain characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work.

[0087] 3.2) The voltage time domain characteristics of the ferromagnetic resonance in the actual photovoltaic power generation system are analyzed by fast Fourier decomposition, and the voltage frequency domain characteristics of the ferromagnetic resonance in the actual photovoltaic power generation system are obtained.

[0088] Embodiment 16:

[0089] A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, the main technical content of which is shown in any one of Embodiments 9 to 15. Further, the calculation formula of the fast Fourier decomposition is as follows:

[0090] f(t)=∫F(ω)e iωt dω (1)

[0091] Where ω is the frequency, f(t) is the frequency domain analytical expression obtained by Fourier decomposition, F(ω) is the amplitude of the sine wave with frequency ω, and e iωt is a complex exponential function.

[0092] Embodiment 17:

[0093] See also Figures 1 to 8 , a method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection, comprising the following steps:

[0094] S1: Establish an electromagnetic transient model of the photovoltaic power generation system.

[0095] S2: Different operating conditions are preset in the electromagnetic transient model of the photovoltaic power generation system to obtain the time domain and frequency domain characteristics of the ferromagnetic resonance in the photovoltaic power generation access station.

[0096] S3: Through data preprocessing, feature extraction, data mining and other methods, the frequency domain characteristics of ferromagnetic resonance under the influence of photovoltaic power generation harmonics and traditional ferromagnetic resonance are compared and analyzed, and the characteristic quantity connection between the harmonics generated by photovoltaic power generation and ferromagnetic resonance is established and stored in the database.

[0097] S4: Obtain the voltage time domain characteristics in actual work and obtain its harmonic content through fast Fourier transform.

[0098] S5: Real-time analysis of the voltage frequency domain characteristics in the actual system, and when ferromagnetic resonance overvoltage is detected in the photovoltaic power generation system, the suppression device is ensured to act quickly.

[0099] The steps of establishing a photovoltaic power generation ferromagnetic resonance frequency domain feature database are as follows:

[0100] S31: Excite ferromagnetic resonance in the electromagnetic transient simulation model of the photovoltaic power station to obtain the voltage waveform.

[0101] S32: Analysis of photovoltaic ferromagnetic resonance harmonic characteristics by fast Fourier decomposition.

[0102] S33: Compare and analyze the frequency domain characteristics of ferromagnetic resonance and traditional ferromagnetic resonance in photovoltaic power generation systems and establish a database.

[0103] Embodiment 18:

[0104] See also Figures 1 to 8 , a method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection, mainly including the following contents:

[0105] Figure 1 This is a flow chart of the ferromagnetic resonance overvoltage suppression device for the photovoltaic power generation system of the present invention. Figure 2 A flow chart for constructing a frequency domain characteristic database for photovoltaic power generation ferromagnetic resonance of the present invention.

[0106] Reference Figure 1 The method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection of the present invention comprises:

[0107] S1: Establish an electromagnetic transient simulation model for photovoltaic power generation system.

[0108] Among them, the photovoltaic power generation model includes: photovoltaic array and MPPT modeling, inverter non-ideal model, etc. The photovoltaic power generation system substation model includes: line model, transformer model, PT model, capacitor reactor model, etc.

[0109] Figure 3 This is the PT nonlinear inductance φ-i characteristic curve. Figure 4 This is the φ-i characteristic curve of the main transformer.

[0110] S2: Different working conditions are preset in the simulation model to obtain the time domain and frequency domain characteristics of ferromagnetic resonance in the photovoltaic power generation access station.

[0111] S3: Through data preprocessing, feature extraction, data mining and other methods, the frequency domain characteristics of ferromagnetic resonance under the influence of photovoltaic power generation harmonics and traditional ferromagnetic resonance are compared and analyzed, and the characteristic quantity connection between the harmonics generated by photovoltaic power generation and ferromagnetic resonance is established and stored in the database.

[0112] Figure 5 This is a comparison of the frequency domain characteristics of ferromagnetic resonance and traditional ferromagnetic resonance in photovoltaic power generation systems. It can be seen from the figure that the ferromagnetic resonance overvoltage amplitude in photovoltaic power generation systems is larger, so the harm is greater. Due to the influence of power supply harmonics, the ferromagnetic resonance frequency division resonance characteristics in photovoltaic power generation systems are significant, and contain 2nd, 3rd, 5th and other high-order harmonics. The action of the suppression device can be controlled according to the different harmonic contents.

[0113] S4: Obtain the voltage time domain characteristics in actual work and obtain its harmonic content through fast Fourier transform.

[0114] Among them, the Fourier decomposition formula is:

[0115] f(t)=∫F(ω)e iωt dω (1)

[0116] Among them, f(t) is the frequency domain analytical expression obtained by Fourier decomposition, F(ω) is the amplitude of the sine wave with frequency ω, and e iωt is a complex exponential function.

[0117] S5: Real-time analysis of the voltage frequency domain characteristics in the actual system, and when ferromagnetic resonance overvoltage is detected in the photovoltaic power generation system, the suppression device is ensured to act quickly.

[0118] Figure 6 This is a comparison diagram of the system voltage before and after the suppression device is activated. It can be seen from the figure that the suppression effect is obvious, the resonant overvoltage peak value decreases, and the waveform returns to normal within 0.2s after the resonance occurs.

Claims

1. A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection, characterized in that: The following steps are involved: 1) Obtain the ferromagnetic resonance frequency domain characteristics of photovoltaic power generation systems affected by photovoltaic power generation harmonics under different working conditions; 2) Compare and analyze the frequency domain characteristics of ferromagnetic resonance affected by photovoltaic power generation harmonics and the frequency domain characteristics of ferromagnetic resonance not affected by photovoltaic power generation harmonics, establish a mapping relationship between the harmonics generated by photovoltaic power generation and ferromagnetic resonance, and write it into the photovoltaic power generation ferromagnetic resonance frequency domain feature database. 3) Obtain the voltage-frequency characteristics of ferromagnetic resonance in photovoltaic power generation systems in actual work. 4) Compare and analyze the voltage frequency domain characteristics of ferromagnetic resonance in the actual photovoltaic power generation system with the data in the photovoltaic power generation ferromagnetic resonance frequency domain characteristic database. If ferromagnetic resonance overvoltage occurs in the photovoltaic power generation system, the suppression device is started to suppress the ferromagnetic resonance overvoltage of the photovoltaic power generation system.

2. The method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection according to claim 1, characterized in that: The step of obtaining the ferromagnetic resonance frequency domain characteristics of the photovoltaic power generation system affected by photovoltaic power generation harmonics under different working conditions comprises: 1.1) Establish an electromagnetic transient model of photovoltaic power generation system; 1.2) Preset different working conditions in the electromagnetic transient model of the photovoltaic power generation system, and excite ferromagnetic resonance to obtain the voltage time domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by photovoltaic power generation harmonics under the corresponding working conditions; 1.3) The voltage time-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are analyzed by fast Fourier decomposition, and the frequency-domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system affected by the photovoltaic power generation harmonics under different working conditions are obtained.

3. The method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection according to claim 2, characterized in that: The photovoltaic power generation system electromagnetic transient model includes a photovoltaic power generation model and a photovoltaic power generation system substation model.

4. A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection according to claim 3, characterized in that: The photovoltaic power generation model includes photovoltaic array and MPPT modeling, and inverter non-ideal model.

5. The method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection according to claim 3, characterized in that: The photovoltaic power generation system substation model includes a line model, a transformer model, a PT model, and a capacitor reactor model.

6. The method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection according to claim 1, characterized in that: The method for comparing and analyzing the ferromagnetic resonance frequency domain characteristics affected by photovoltaic power generation harmonics and the ferromagnetic resonance frequency domain characteristics not affected by photovoltaic power generation harmonics includes data preprocessing, feature extraction, and data mining.

7. The method for suppressing ferromagnetic resonance overvoltage of a photovoltaic power generation system based on harmonic detection according to claim 1, characterized in that: The step of obtaining the voltage frequency domain characteristics of ferromagnetic resonance in the photovoltaic power generation system in actual work includes: 3.1) Obtain the voltage time domain characteristics of ferromagnetic resonance in the actual photovoltaic power generation system; 3.2) The voltage time domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system in actual work are analyzed by fast Fourier decomposition, and the voltage frequency domain characteristics of the ferromagnetic resonance in the photovoltaic power generation system in actual work are obtained.

8. A method for suppressing ferromagnetic resonance overvoltage in a photovoltaic power generation system based on harmonic detection according to any one of claims 2 or 7, characterized in that: The calculation formula of the fast Fourier decomposition is as follows: f(t)=∫F(ω)e iωt dω (1) Where ω is the frequency, f(t) is the frequency domain analytical expression obtained by Fourier decomposition, F(ω) is the amplitude of the sine wave with frequency ω, and e iωt is a complex exponential function.

Images