Arc monitoring circuit of photovoltaic system
By designing a photovoltaic system arc monitoring circuit including signal acquisition and processing units, the problem of difficulty in monitoring DC arc stretching in photovoltaic systems is solved, and high sensitivity monitoring and distinction of DC arc stretching signals is realized, and the reliability of monitoring is improved.
Patent Information
- Application Number
- CN202420200241.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-26
- Publication Date
- 2025-03-18
- Estimated Expiration
- 2034-01-26
AI Technical Summary
DC arc pulling is difficult to accurately monitor in photovoltaic systems, mainly due to the lack of periodic changes in current and voltage, which makes it difficult for the monitoring system to identify and distinguish between normal DC current and potential arc pulling current.
An arc monitoring circuit for a photovoltaic system is designed, including a signal acquisition unit and a signal processing unit. The signal acquisition unit simplifies the signal acquisition structure through a multiplexer, while the signal processing unit improves signal quality and monitoring sensitivity through basic amplification, filtering and further amplification processing.
Through the multi-stage amplification and filtering processing of the signal processing unit, small signal changes caused by DC arc drawing can be accurately captured, the monitoring circuit's ability to distinguish normal DC current and potential arc drawing current can be improved, and the sensitivity and reliability of DC arc drawing monitoring can be enhanced.
Smart Images
Figure CN222638502U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of power system monitoring, and in particular to an arc monitoring circuit for a photovoltaic system. Background Art
[0002] Fire is one of the accidents that causes the greatest economic loss in photovoltaic power plants. There are many factors that cause fires. For fires in photovoltaic power plants, DC arcing is one of the main causes of fires in photovoltaic power plants.
[0003] Arcing is an arc discharge, which is a visible spark produced when current passes through a non-conductive medium (such as air). DC arcing is a phenomenon that occurs in DC circuits, usually due to a sudden interruption of current or a fault in the circuit. In photovoltaic power plants, DC arcing is usually caused by loose joints of photovoltaic modules, poor contact, damp wires, broken insulation, etc. When the current is interrupted at these fault points, DC arcing may occur. DC arcing will generate extremely high temperatures, usually between 3000-7000℃, which may cause overheating of the contact parts, which may cause fuses and cables to melt at the least, or cause fires and damage components and equipment at the worst.
[0004] Since a fire in a photovoltaic system cannot be extinguished directly with water (water is a conductor, and when water comes into contact with energized electrical equipment or circuits, it may cause a risk of electric shock, and the combination of water and electric current may cause more serious fires or other safety accidents), it is very important to warn and prevent DC arcing in photovoltaic systems.
[0005] However, monitoring DC arcs presents some challenges compared to other types of arcs, such as AC arcs. DC arcs do not have periodic changes in current and voltage, as in AC arcs. In AC arcs, current and voltage periodically cross zero, producing significant oscillations. In DC arcs, this periodic variation is less frequent, and it is difficult for monitoring systems to accurately capture the small changes caused by DC arcs, making it more difficult for monitoring systems to identify and distinguish normal DC current from potential arcing current. Utility Model Content
[0006] In order to improve the sensitivity and reliability of DC arc monitoring, the present application provides an arc monitoring circuit for a photovoltaic system.
[0007] The present application provides an arc monitoring circuit for a photovoltaic system, which adopts the following technical solution:
[0008] An arc monitoring circuit for a photovoltaic system comprises a signal acquisition unit and a signal processing unit, wherein the signal acquisition unit is used to sequentially acquire electrical signals of a plurality of induction coils of the photovoltaic system and send the electrical signals to the signal processing unit, and the signal processing unit is used to improve the quality of the electrical signals;
[0009] The input end of the signal acquisition unit is used to connect with the multiple induction coils of the photovoltaic system, and the output end of the signal acquisition unit is connected with the signal processing unit;
[0010] The signal processing unit includes a first amplifying unit, a filtering unit and a second amplifying unit, wherein the input end of the first amplifying unit is used to be connected to the input end of the signal processing unit, the output end of the first amplifying unit is connected to the input end of the filtering unit, the output end of the filtering unit is connected to the input end of the second amplifying unit, and the output end of the second amplifying unit is connected to the output end of the signal processing unit;
[0011] The first amplifying unit is used to perform basic amplification processing on the electrical signal, the filtering unit is used to perform filtering processing on the electrical signal that has undergone basic amplification processing, and the second amplifying unit is used to perform further amplification processing on the electrical signal that has undergone filtering processing.
[0012] By adopting the above technical solution, during the signal acquisition process, the electrical signal may be mixed with noise. By performing basic amplification processing after signal acquisition, the amplitude of the signal can be increased. Moreover, in the monitoring of DC arcing, small signal changes may be key indicators, so amplification can make it easier for the system to capture these changes.
[0013] Filtering the amplified electrical signal can effectively reduce the noise in the signal, allowing the system to focus more on detecting and identifying the real electrical signal. In addition, the DC arc signal contains components of specific frequencies, which are located in a different frequency range from other noise or interference. By using a filtering unit, signals in a specific frequency range can be selectively highlighted or suppressed to improve the subsequent ability to distinguish DC arc signals.
[0014] In summary, filtering plays a key role in improving the reliability of DC arc monitoring. By reducing noise and optimizing signal characteristics, the monitoring system is made more robust and accurate.
[0015] Further amplifying the electrical signal after filtering can enhance the strength of the signal to avoid the phenomenon that the signal amplitude is reduced after filtering, which affects subsequent processing and analysis.
[0016] Through this structured signal processing method, subsequent processing and analysis of electrical signals can accurately capture the slight changes caused by DC arcing, improve the monitoring circuit's ability to distinguish between normal DC current and potential arcing current, and improve the sensitivity and reliability of DC arc monitoring.
[0017] Exemplarily, the signal acquisition unit includes a multiplexer, the multiplexer includes a signal output end and multiple signal acquisition ends, the multiple signal acquisition ends are used to be connected to the induction coils of the photovoltaic system in a one-to-one correspondence, and the signal output end forms the output end of the signal acquisition unit.
[0018] By adopting the above technical solution, the multiplexer outputs the signals of multiple induction coils from the same signal output terminal in sequence, thereby simplifying the structure of the entire signal acquisition unit, reducing the complexity of the connection lines, and reducing the distortion and loss of signal transmission.
[0019] Exemplarily, the filtering unit includes a high-pass filtering module and a low-pass filtering module, the input end of the high-pass filtering module forms the input end of the filtering unit, the output end of the high-pass filtering module is connected to the input end of the low-pass filtering module, and the output end of the low-pass filtering module forms the output end of the filtering unit.
[0020] By adopting the above technical solution, the high-pass filter module can be used to remove the DC component. By removing the DC component, the subsequent signal analysis unit can more easily detect the slight changes of the DC arc, and improve the sensitivity of the monitoring circuit to the DC arc signal. The low-pass filter module helps to smooth the signal, remove high-frequency noise and sharp changes, and can make the output signal more stable. This can improve the ability of the subsequent signal analysis unit to capture the slowly changing DC arc signal.
[0021] In general, the design combining the high-pass filter module and the low-pass filter module helps to improve the reliability of DC arc monitoring and ensure that the subsequent signal analysis unit can capture key signal features more accurately.
[0022] Exemplarily, the high-pass filtering module includes a first high-pass filter and a second high-pass filter, the input end of the first high-pass filter forms the input end of the high-pass filtering module, the output end of the first high-pass filter is connected to the input end of the second high-pass filter, the output end of the second high-pass filter forms the output end of the high-pass filtering module, and the cutoff frequency of the first high-pass filter is less than the cutoff frequency of the second high-pass filter.
[0023] By adopting the above technical solution and introducing two high-pass filters with different cutoff frequencies, frequency layered processing of the input signal is achieved, so that the high-pass filter module can more finely control the frequency range to be passed, ensure the detection sensitivity of the DC arcing signal, improve the monitoring effect of the DC arcing signal, and enhance the reliability of the system.
[0024] Exemplarily, the low-pass filtering module includes a first low-pass filter and a second low-pass filter, the input end of the first low-pass filter forms the input end of the low-pass filtering module, the output end of the first low-pass filter is connected to the input end of the second low-pass filter, the output end of the second low-pass filter forms the output end of the low-pass filtering module, and the cutoff frequency of the first low-pass filter is greater than the cutoff frequency of the second low-pass filter.
[0025] By adopting the above technical solution, similar to the high-pass filter module, the design of the low-pass filter module also adopts the frequency layering method. In this way, the frequency range to be passed can be more finely controlled to ensure a smoother output signal.
[0026] Exemplarily, the first high-pass filter and the second high-pass filter each include a first capacitor, a second capacitor, a first resistor, a second resistor and a first operational amplifier, the first capacitor, the second capacitor, the first resistor and the second resistor each include a first connection end and a second connection end, the first connection end of the first capacitor forms the input end of the high-pass filter, the second connection end of the first capacitor is connected to the first connection end of the second capacitor, the second connection end of the second capacitor is connected to the non-inverting input end of the first operational amplifier, the first connection end of the second resistor is connected between the second connection end of the second capacitor and the non-inverting input end of the first operational amplifier, the second connection end of the second resistor is connected to a reference voltage, the first connection end of the first resistor is connected between the second connection end of the first capacitor and the first connection end of the second capacitor, the second connection end of the first resistor is connected to the inverting input end of the first operational amplifier, the output end of the first operational amplifier is connected to the inverting input end of the first operational amplifier, and the output end of the first operational amplifier forms the output end of the high-pass filter;
[0027] The resistance value of the first resistor of the first high-pass filter is greater than the resistance value of the first resistor of the second high-pass filter, and the resistance value of the second resistor of the first high-pass filter is less than the resistance value of the second resistor of the second high-pass filter.
[0028] By adopting the above technical solution, the first resistance of the first high-pass filter is greater than the first resistance of the second high-pass filter, and the second resistance of the second high-pass filter is greater than the second resistance of the first high-pass filter, which helps to improve the system's sensitivity to high-frequency components in DC arcing signals.
[0029] Exemplarily, the first low-pass filter and the second low-pass filter each include a third capacitor, a fourth capacitor, a third resistor, a fourth resistor and a second operational amplifier, and the third capacitor, the fourth capacitor, the third resistor and the fourth resistor each include a first connection end and a second connection end;
[0030] The first connection end of the third resistor forms the input end of the above-mentioned low-pass filter, the second connection end of the third resistor is connected to the first connection end of the fourth resistor, the second connection end of the fourth resistor is connected to the non-inverting input end of the second operational amplifier, the first connection end of the fourth capacitor is connected between the second connection end of the fourth resistor and the non-inverting input end of the second operational amplifier, the second connection end of the fourth capacitor is connected to a reference voltage, the first connection end of the third capacitor is connected between the second connection end of the third resistor and the first connection end of the fourth resistor, the second connection end of the third capacitor is connected to the inverting input end of the second operational amplifier, the output end of the second operational amplifier is connected to the inverting input end of the second operational amplifier, and the output end of the second operational amplifier forms the output end of the above-mentioned low-pass filter;
[0031] Among them, the resistance value of the third resistor of the first low-pass filter is smaller than the resistance value of the third resistor of the second low-pass filter, the resistance value of the fourth resistor of the first low-pass filter is smaller than the resistance value of the fourth resistor of the second low-pass filter, the resistance value of the third capacitor of the first low-pass filter is greater than the capacitive reactance of the third capacitor of the second low-pass filter, and the resistance value of the fourth capacitor of the first low-pass filter is greater than the capacitive reactance of the fourth capacitor of the second low-pass filter.
[0032] By adopting the above technical solution and adjusting the resistance and capacitance parameters of the first low-pass filter and the second low-pass filter, the cutoff frequency of the system can be selected more precisely, which helps to optimize the system's response to the low-frequency components in the DC arcing signal and improve the accuracy of monitoring.
[0033] Exemplarily, the first amplifying unit includes a third operational amplifier U6A, a first amplifying resistor R24, and a second amplifying resistor R19, one end of the first amplifying resistor R24 is connected to a reference voltage, and the other end is connected to an inverting input of the third operational amplifier U6A, one end of the second amplifying resistor R19 is connected to the inverting input of the third operational amplifier U6A, and the other end is connected to the output of the third operational amplifier U6A, the non-inverting input of the third operational amplifier U6A forms the input of the first amplifying unit, and the output of the third operational amplifier U6A forms the output of the first amplifying unit.
[0034] By adopting the above technical solution, the first amplification unit realizes voltage amplification of the electrical signal by using an operational amplifier and a corresponding resistor network, which helps to enhance the system's sensitivity to tiny signals, especially in DC arc monitoring, and can better capture tiny electrical signal changes.
[0035] Exemplarily, the second amplifying unit includes a fourth operational amplifier U4B, a third amplifying resistor R22, a fourth amplifying resistor R18, a first amplifying capacitor C35 and a second amplifying capacitor C30, one end of the first amplifying capacitor C35 forms the input end of the second amplifying unit, and the other end is connected to the third amplifying resistor R22, the third amplifying resistor R22 is connected to the inverting input end of the fourth operational amplifier U4B, one end of the fourth amplifying resistor R18 is connected between the third amplifying resistor R22 and the inverting input end of the fourth operational amplifier U4B, and the other end is connected to the output end of the fourth operational amplifier U4B, one end of the second amplifying capacitor C30 is connected between the third amplifying resistor R22 and the inverting input end of the fourth operational amplifier U4B, and the other end is connected to the output end of the fourth operational amplifier U4B, and the output end of the fourth operational amplifier U4B forms the output end of the second amplifying unit.
[0036] By adopting the above technical solution, the second amplification unit realizes further voltage amplification and filtering of the signal through the fourth operational amplifier U4B and the corresponding capacitor and resistor network. This helps to enhance the sensitivity to the DC arcing signal, while filtering out unnecessary high-frequency components and improving the performance of the system.
[0037] In summary, the present application includes at least one of the following beneficial technical effects:
[0038] 1. By performing basic amplification processing on the electrical signal after signal acquisition, the amplitude of the signal can be increased. Moreover, in the monitoring of DC arcing, small signal changes may be key indicators, so amplification can make it easier for the system to capture these changes. Filtering the amplified electrical signal can effectively reduce the noise in the signal, allowing the system to focus more on detecting and identifying the real electrical signal. Moreover, the DC arcing signal contains components of specific frequencies, which are located in a different frequency range from other noise or interference. By using a filtering unit, signals in a specific frequency range can be selectively highlighted or suppressed to improve the subsequent ability to distinguish DC arcing signals. Further amplification of the electrical signal after filtering can enhance the strength of the signal to avoid the phenomenon of reduced signal amplitude after filtering, which affects subsequent processing and analysis.
[0039] Through this structured signal processing method, subsequent processing and analysis of electrical signals can accurately capture the slight changes caused by DC arcing, improve the monitoring circuit's ability to distinguish between normal DC current and potential arcing current, and improve the sensitivity and reliability of DC arc monitoring.
[0040] 2. By setting a multiplexer, the multiplexer outputs the signals of multiple induction coils from the same signal output terminal in sequence, which simplifies the structure of the entire signal acquisition unit, reduces the complexity of the connection line, and reduces the distortion and loss of signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Figure 1 It is the circuit diagram of the signal acquisition unit.
[0042] Figure 2 is the circuit diagram of the signal processing unit.
[0043] Figure 3 This is the circuit diagram of the high-pass filter module.
[0044] Figure 4 This is the circuit diagram of the low-pass filter module.
[0045] Description of reference numerals:
[0046] 1. Signal acquisition unit; 2. Signal processing unit; 21. First amplifying unit; 22. Filtering unit; 221. High-pass filtering module; 2211. First high-pass filter; 2212. Second high-pass filter; 222. Low-pass filtering module; 2221. First low-pass filter; 2222. Second low-pass filter; 23. Second amplifying unit; 3. Signal analyzing unit. DETAILED DESCRIPTION
[0047] The present application is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0048] The present application embodiment discloses an arc monitoring circuit for a photovoltaic system. Figure 1 and Figure 2 , an arc monitoring circuit for a photovoltaic system, comprising a signal acquisition unit 1 and a signal processing unit 2. The output end of the signal acquisition unit 1 is connected to the input end of the signal processing unit 2. The signal acquisition unit 1 is used to sequentially acquire electrical signals from a plurality of induction coils and send the electrical signals to the signal processing unit 2. The signal processing unit 2 is used to enhance the amplitude of the electrical signal and adjust the spectrum of the electrical signal to improve the quality of the signal. The input end of the signal acquisition unit 1 is connected to a plurality of induction coils of the photovoltaic system, and the output end of the signal processing unit 2 is used to connect to a signal analysis unit 3, and send the processed electrical signal to the signal analysis unit 3, so that the signal analysis unit 3 can better analyze and identify the electrical signal.
[0049] Continue to refer to Figure 1 In the embodiment of the present application, the signal acquisition unit 1 includes a multiplexer, and the multiplexer includes a signal output terminal and a plurality of signal acquisition terminals. The plurality of signal acquisition terminals are used to be connected one-to-one with the induction coils of the photovoltaic system, and the signal output terminal forms the output terminal of the signal acquisition unit 1. There are multiple signal transmission paths inside the multiplexer, which can enable the electrical signals of the plurality of induction coils to be output from the same signal output terminal to the subsequent signal processing unit 2. There is no need to equip each induction coil with a dedicated signal processing unit 2 and signal analysis unit 3, which simplifies the structure of the entire signal acquisition unit 1, reduces the complexity of the connection line, and reduces the distortion and loss of signal transmission. Specifically, the multiplexer used in the embodiment of the present application is CD74HCT4051M96, the A pin of the multiplexer is the signal output terminal, and A1-A7 are the signal acquisition terminals.
[0050] Reference Figure 2 The signal processing unit 2 includes a first amplifying unit 21, a filtering unit 22 and a second amplifying unit 23. The first amplifying unit 21 is used to perform basic amplification processing on the electrical signal, the filtering unit 22 is used to perform filtering processing on the electrical signal that has undergone basic amplification processing, and the second amplifying unit 23 is used to further amplify the electrical signal that has undergone filtering processing. The input end of the first amplifying unit 21 is used to be connected to the input end of the signal processing unit 2, the output end of the first amplifying unit 21 is connected to the input end of the filtering unit 22, the output end of the filtering unit 22 is connected to the input end of the second amplifying unit 23, and the output end of the second amplifying unit 23 is connected to the output end of the signal processing unit 2.
[0051] Continue to refer Figure 1The first amplifying unit 21 includes a third operational amplifier U6A, a first amplifying resistor R24, and a second amplifying resistor R19. One end of the first amplifying resistor R24 is connected to the reference voltage, and the other end is connected to the inverting input terminal of the third operational amplifier U6A. One end of the second amplifying resistor R19 is connected to the inverting input terminal of the third operational amplifier U6A, and the other end is connected to the output terminal of the third operational amplifier U6A. The non-inverting input terminal of the third operational amplifier U6A forms the input terminal of the first amplifying unit 21, and the output terminal of the third operational amplifier U6A forms the output terminal of the first amplifying unit 21.
[0052] The second amplifying unit 23 includes a fourth operational amplifier U4B, a third amplifying resistor R22, a fourth amplifying resistor R18, a first amplifying capacitor C35 and a second amplifying capacitor C30. One end of the first amplifying capacitor C35 forms the input end of the second amplifying unit 23, and the other end is connected to the third amplifying resistor R22. The third amplifying resistor R22 is connected to the inverting input end of the fourth operational amplifier U4B. One end of the fourth amplifying resistor R18 is connected between the third amplifying resistor R22 and the inverting input end of the fourth operational amplifier U4B, and the other end is connected to the output end of the fourth operational amplifier U4B. One end of the second amplifying capacitor C30 is connected between the third amplifying resistor R22 and the inverting input end of the fourth operational amplifier U4B, and the other end is connected to the output end of the fourth operational amplifier U4B. The output end of the fourth operational amplifier U4B forms the output end of the second amplifying unit 21.
[0053] Furthermore, in order to enable the subsequent signal analysis unit 3 to more accurately capture the signal characteristics of the DC arcing signal, the filtering unit 22 disclosed in the embodiment of the present application includes a high-pass filtering module 221 and a low-pass filtering module 222, the input end of the high-pass filtering module 221 forms the input end of the filtering unit 22, the output end of the high-pass filtering module 221 is connected to the input end of the low-pass filtering module 222, and the output end of the low-pass filtering module 222 forms the output end of the filtering unit 22.
[0054] refer to Figure 3Specifically, in different embodiments, the high-pass filter module 221 can be implemented by different circuit structures. In the embodiment of the present application, the high-pass filter module 221 includes a first high-pass filter 2211 and a second high-pass filter 2212. The input end of the first high-pass filter 2211 forms the input end of the high-pass filter module 221, the output end of the first high-pass filter 2211 is connected to the input end of the second high-pass filter 2212, and the output end of the second high-pass filter 2212 forms the output end of the high-pass filter module 221. The cutoff frequency of the first high-pass filter 2211 is greater than the cutoff frequency of the second high-pass filter 2212. By introducing two high-pass filters with different cutoff frequencies, it is possible to achieve frequency layered processing of the input signal, so as to more finely control the frequency range to be passed, ensure the detection sensitivity of the DC arcing signal, improve the monitoring effect of the DC arcing signal, and enhance the reliability of the system.
[0055] In an embodiment of the present application, the first high-pass filter 2211 and the second high-pass filter 2212 both include a first capacitor, a second capacitor, a first resistor, a second resistor and a first operational amplifier. The first capacitor, the second capacitor, the first resistor and the second resistor both include a first connection end and a second connection end. The first connection end of the first capacitor forms the input end of the above-mentioned high-pass filter, the second connection end of the first capacitor is connected to the first connection end of the second capacitor, the second connection end of the second capacitor is connected to the non-inverting input end of the first operational amplifier, the first connection end of the second resistor is connected between the second connection end of the second capacitor and the non-inverting input end of the first operational amplifier, and the second connection end of the second resistor is connected to the reference voltage. The first connection end of the first resistor is connected between the second connection end of the first capacitor and the first connection end of the second capacitor, and the second connection end of the first resistor is connected to the inverting input end of the first operational amplifier. The output end of the first operational amplifier is connected to the inverting input end of the first operational amplifier, and the output end of the first operational amplifier forms the output end of the above-mentioned high-pass filter. The resistance value of the first resistor of the first high pass filter 2211 is greater than the resistance value of the first resistor of the second high pass filter 2212 , and the resistance value of the second resistor of the first high pass filter 2211 is less than the resistance value of the second resistor of the second high pass filter 2212 .
[0056] Specifically, in the embodiment of the present application, the first capacitor of the first high-pass filter 2211 is C40 (capacitive reactance is 1nF), the second capacitor is C41 (capacitive reactance is 1nF), the first resistor is R25 (resistance is 2.7kΩ), the second resistor is R26 (resistance is 3.9kΩ), and the first operational amplifier is U6B. In this way, the cutoff frequency of the first high-pass filter 2211 is 27kHz. The first capacitor of the second high-pass filter 2212 is C38 (capacitive reactance is 1nF), the second capacitor is C39 (capacitive reactance is 1nF), the first resistor is R20 (resistance is 1.8kΩ), the second resistor is R21 (resistance is 10kΩ), and the first operational amplifier is U5A. In this way, the cutoff frequency of the second high-pass filter 2212 is 57kHz.
[0057] refer to Figure 4 The low-pass filter module 222 includes a first low-pass filter 2221 and a second low-pass filter 2222. The input end of the first low-pass filter 2221 forms the input end of the low-pass filter module 222. The output end of the first low-pass filter 2221 is connected to the input end of the second low-pass filter 2222. The output end of the second low-pass filter 2222 forms the output end of the low-pass filter module 222. The cut-off frequency of the first low-pass filter 2221 is greater than the cut-off frequency of the second low-pass filter 2222.
[0058] Specifically, in different embodiments, the low-pass filter module 222 can be implemented by different circuit structures. In the embodiment of the present application, the first low-pass filter 2221 and the second low-pass filter 2222 both include a third capacitor, a fourth capacitor, a third resistor, a fourth resistor and a second operational amplifier. The third capacitor, the fourth capacitor, the third resistor and the fourth resistor all include a first connection end and a second connection end. The first connection end of the third resistor forms the input end of the above-mentioned low-pass filter, the second connection end of the third resistor is connected to the first connection end of the fourth resistor, the second connection end of the fourth resistor is connected to the in-phase input end of the second operational amplifier, the first connection end of the fourth capacitor is connected between the second connection end of the fourth resistor and the in-phase input end of the second operational amplifier, the second connection end of the fourth capacitor is connected to the reference voltage, the first connection end of the third capacitor is connected between the second connection end of the third resistor and the first connection end of the fourth resistor, the second connection end of the third capacitor is connected to the inverting input end of the second operational amplifier, the output end of the second operational amplifier is connected to the inverting input end of the second operational amplifier, and the output end of the second operational amplifier forms the output end of the above-mentioned low-pass filter.
[0059] The resistance value of the third resistor of the first low-pass filter 2221 is smaller than the resistance value of the third resistor of the second low-pass filter 2222, the resistance value of the fourth resistor of the first low-pass filter 2221 is smaller than the resistance value of the fourth resistor of the second low-pass filter 2222, the capacitive reactance of the third capacitor of the first low-pass filter 2221 is greater than the capacitive reactance of the third capacitor of the second low-pass filter 2222, and the capacitive reactance of the fourth capacitor of the first low-pass filter 2221 is greater than the capacitive reactance of the fourth capacitor of the second low-pass filter 2222.
[0060] Specifically, in the embodiment of the present application, the third capacitor of the first low-pass filter 2221 is C34 (capacitive reactance is 1.5nF), the fourth capacitor is C33 (capacitive reactance is 1nF), the third resistor is R31 (resistance is 1.2kΩ), the fourth resistor is R32 (resistance is 1.2kΩ), and the second operational amplifier is U5B. With such settings, the cutoff frequency of the first low-pass filter 2221 is 149kHz. The third capacitor of the second low-pass filter 2222 is C32 (capacitive reactance is 1nF), the fourth capacitor is C31 (capacitive reactance is 91pF), the third resistor is R27 (resistance is 5.1kΩ), the fourth resistor is R28 (resistance is 5.1kΩ), and the second operational amplifier is U4A. With such settings, the cutoff frequency of the second low-pass filter 2222 is 90kHz.
[0061] In the embodiment of the present application, the filter unit 22 forms a bandpass filter unit 22 by setting a first high-pass filter 2211, a second high-pass filter 2212, a first low-pass filter 2221 and a second low-pass filter 2222, with a bandwidth range of 27kHz to 90kHz. In a specific application, the bandwidth range of the filter unit 22 can be changed by changing the parameters in the first high-pass filter 2211, the second high-pass filter 2212, the first low-pass filter 2221 and the second low-pass filter 2222.
[0062] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.
Claims
1. An arc monitoring circuit for a photovoltaic system, characterized in that: It comprises a signal acquisition unit (1) and a signal processing unit (2), wherein the signal acquisition unit (1) is used to sequentially acquire electrical signals from a plurality of induction coils of the photovoltaic system and send the electrical signals to the signal processing unit (2), and the signal processing unit (2) is used to improve the quality of the electrical signals; The input end of the signal acquisition unit (1) is used to be connected to a plurality of induction coils of the photovoltaic system, and the output end of the signal acquisition unit (1) is connected to the signal processing unit (2); The signal processing unit (2) comprises a first amplifying unit (21), a filtering unit (22) and a second amplifying unit (23); the input end of the first amplifying unit (21) is used to be connected to the input end of the signal processing unit (2); the output end of the first amplifying unit (21) is connected to the input end of the filtering unit (22); the output end of the filtering unit (22) is connected to the input end of the second amplifying unit (23); and the output end of the second amplifying unit (23) is connected to the output end of the signal processing unit (2); The first amplifying unit (21) is used to perform basic amplification processing on the electrical signal, the filtering unit (22) is used to perform filtering processing on the electrical signal that has undergone basic amplification processing, and the second amplifying unit (23) is used to perform further amplification processing on the electrical signal that has undergone filtering processing.
2. The arc monitoring circuit of the photovoltaic system according to claim 1, characterized in that: The signal acquisition unit (1) comprises a multiplexer, the multiplexer comprising a signal output end and a plurality of signal acquisition ends, the plurality of signal acquisition ends being used for one-to-one connection with the induction coils of the photovoltaic system, the signal output end forming the output end of the signal acquisition unit (1).
3. The arc monitoring circuit of the photovoltaic system according to claim 1, characterized in that: The filtering unit (22) comprises a high-pass filtering module (221) and a low-pass filtering module (222); the input end of the high-pass filtering module (221) forms the input end of the filtering unit (22); the output end of the high-pass filtering module (221) is connected to the input end of the low-pass filtering module (222); and the output end of the low-pass filtering module (222) forms the output end of the filtering unit (22).
4. The arc monitoring circuit of the photovoltaic system according to claim 3, characterized in that The high-pass filter module (221) comprises a first high-pass filter (2211) and a second high-pass filter (2212); the input end of the first high-pass filter (2211) forms the input end of the high-pass filter module (221); the output end of the first high-pass filter (2211) is connected to the input end of the second high-pass filter (2212); the output end of the second high-pass filter (2212) forms the output end of the high-pass filter module (221); and the cut-off frequency of the first high-pass filter (2211) is less than the cut-off frequency of the second high-pass filter (2212).
5. The arc monitoring circuit of the photovoltaic system according to claim 3, characterized in that: The low-pass filter module (222) comprises a first low-pass filter (2221) and a second low-pass filter (2222); the input end of the first low-pass filter (2221) forms the input end of the low-pass filter module (222); the output end of the first low-pass filter (2221) is connected to the input end of the second low-pass filter (2222); the output end of the second low-pass filter (2222) forms the output end of the low-pass filter module (222); and the cut-off frequency of the first low-pass filter (2221) is greater than the cut-off frequency of the second low-pass filter (2222).
6. The arc monitoring circuit of the photovoltaic system according to claim 4, characterized in that: The first high-pass filter (2211) and the second high-pass filter (2212) both comprise a first capacitor, a second capacitor, a first resistor, a second resistor and a first operational amplifier; the first capacitor, the second capacitor, the first resistor and the second resistor all comprise a first connection end and a second connection end; the first connection end of the first capacitor forms an input end of the high-pass filter; the second connection end of the first capacitor is connected to the first connection end of the second capacitor; the second connection end of the second capacitor is connected to a non-inverting input end of the first operational amplifier; the first connection end of the second resistor is connected between the second connection end of the second capacitor and the non-inverting input end of the first operational amplifier; the second connection end of the second resistor is connected to a reference voltage; the first connection end of the first resistor is connected between the second connection end of the first capacitor and the first connection end of the second capacitor; the second connection end of the first resistor is connected to an inverting input end of the first operational amplifier; the output end of the first operational amplifier is connected to the inverting input end of the first operational amplifier; and the output end of the first operational amplifier forms an output end of the high-pass filter; The resistance value of the first resistor of the first high-pass filter (2211) is greater than the resistance value of the first resistor of the second high-pass filter (2212), and the resistance value of the second resistor of the first high-pass filter (2211) is less than the resistance value of the second resistor of the second high-pass filter (2212).
7. The arc monitoring circuit of the photovoltaic system according to claim 5, characterized in that: The first low-pass filter (2221) and the second low-pass filter (2222) both comprise a third capacitor, a fourth capacitor, a third resistor, a fourth resistor and a second operational amplifier, and the third capacitor, the fourth capacitor, the third resistor and the fourth resistor both comprise a first connection end and a second connection end; The first connection end of the third resistor forms the input end of the above-mentioned low-pass filter, the second connection end of the third resistor is connected to the first connection end of the fourth resistor, the second connection end of the fourth resistor is connected to the non-inverting input end of the second operational amplifier, the first connection end of the fourth capacitor is connected between the second connection end of the fourth resistor and the non-inverting input end of the second operational amplifier, the second connection end of the fourth capacitor is connected to a reference voltage, the first connection end of the third capacitor is connected between the second connection end of the third resistor and the first connection end of the fourth resistor, the second connection end of the third capacitor is connected to the inverting input end of the second operational amplifier, the output end of the second operational amplifier is connected to the inverting input end of the second operational amplifier, and the output end of the second operational amplifier forms the output end of the above-mentioned low-pass filter; The resistance value of the third resistor of the first low-pass filter (2221) is smaller than the resistance value of the third resistor of the second low-pass filter (2222), the resistance value of the fourth resistor of the first low-pass filter (2221) is smaller than the resistance value of the fourth resistor of the second low-pass filter (2222), the capacitive reactance of the third capacitor of the first low-pass filter (2221) is larger than the capacitive reactance of the third capacitor of the second low-pass filter (2222), and the capacitive reactance of the fourth capacitor of the first low-pass filter (2221) is larger than the capacitive reactance of the fourth capacitor of the second low-pass filter (2222).
8. The arc monitoring circuit of a photovoltaic system according to claim 1, characterized in that: The first amplifying unit (21) comprises a third operational amplifier U6A, a first amplifying resistor R24, and a second amplifying resistor R19. One end of the first amplifying resistor R24 is connected to a reference voltage, and the other end is connected to an inverting input end of the third operational amplifier U6A. One end of the second amplifying resistor R19 is connected to the inverting input end of the third operational amplifier U6A, and the other end is connected to an output end of the third operational amplifier U6A. The non-inverting input end of the third operational amplifier U6A forms an input end of the first amplifying unit (21), and the output end of the third operational amplifier U6A forms an output end of the first amplifying unit (21).
9. The arc monitoring circuit of a photovoltaic system according to claim 1, characterized in that: The second amplifying unit (23) comprises a fourth operational amplifier U4B, a third amplifying resistor R22, a fourth amplifying resistor R18, a first amplifying capacitor C35 and a second amplifying capacitor C30. One end of the first amplifying capacitor C35 forms an input end of the second amplifying unit (23), and the other end is connected to the third amplifying resistor R22. The third amplifying resistor R22 is connected to an inverting input end of the fourth operational amplifier U4B. One end of the fourth amplifying resistor R18 is connected between the third amplifying resistor R22 and the inverting input end of the fourth operational amplifier U4B, and the other end is connected to the output end of the fourth operational amplifier U4B. One end of the second amplifying capacitor C30 is connected between the third amplifying resistor R22 and the inverting input end of the fourth operational amplifier U4B, and the other end is connected to the output end of the fourth operational amplifier U4B. The output end of the fourth operational amplifier U4B forms the output end of the second amplifying unit (23).