Arc discharge detection circuit and photovoltaic system

Abstract

The utility model provides an arc discharge detection circuit and a photovoltaic system. The circuit comprises a first sampling circuit, a second sampling circuit, a differential circuit and a processing module, the output end of the first sampling circuit is connected with the positive electrode input end of the differential circuit, the output end of the first sampling circuit is connected with the negative electrode input end of the differential circuit, and the output end of the differential circuit is connected with the processing module. According to the differential circuit, differential mode interference and common mode interference in the electric signals can be eliminated by subtracting the output electric signals of the two photovoltaic pole plates, so that an accurate arc discharge signal is obtained, and whether the first photovoltaic pole plate or the second photovoltaic pole plate has an arc discharge fault is directly determined based on the size of the arc discharge signal; the influence of differential mode interference and common mode interference on arc discharge detection is avoided, and the accuracy of arc discharge detection is improved.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology, and in particular to an arc detection circuit and a photovoltaic system. Background Technology

[0002] With the development and widespread application of photovoltaic power generation technology, the technical requirements for photovoltaic systems, such as power generation capacity, are becoming increasingly stringent. A photovoltaic system consists of photovoltaic panels, photovoltaic DC cables, and inverters. It utilizes solar photovoltaic panels exposed outdoors to collect solar energy and convert it into photovoltaic power, thereby achieving photovoltaic power generation.

[0003] Photovoltaic panel arcing refers to the electric arcing phenomenon that occurs between photovoltaic panels in a photovoltaic power generation system due to voltage or voltage fluctuations. This arcing can easily damage circuit components and cause system failure. Therefore, it is necessary to detect arcing faults in photovoltaic power generation systems and promptly disconnect the circuit or take other measures to prevent circuit damage.

[0004] However, during arcing detection, the voltage signal at the output terminal of the photovoltaic plate is affected by differential-mode interference and common-mode interference at the inverter grounding terminal, leading to inaccurate arcing detection. Utility Model Content

[0005] This utility model provides an arc detection circuit and a photovoltaic system to solve the problem of inaccurate arc detection in the prior art.

[0006] In a first aspect, embodiments of the present invention provide an arc detection circuit, comprising:

[0007] The first sampling circuit is used to collect the output electrical signal of the first photovoltaic plate;

[0008] The second sampling circuit is used to collect the output electrical signal of the second photovoltaic plate;

[0009] The positive input terminal is connected to the output terminal of the first sampling circuit, and the negative input terminal is connected to the output terminal of the second sampling circuit. This is a differential circuit used to calculate the difference between the output electrical signal of the first photovoltaic plate and the output electrical signal of the second photovoltaic plate to output an arcing signal.

[0010] A processing module connected to the output of the differential circuit for determining whether the first photovoltaic plate or the second photovoltaic plate has experienced an arcing fault based on the arcing signal.

[0011] In one possible implementation, the arc detection circuit further includes an amplification circuit:

[0012] The input terminal of the amplifier circuit is connected to the output terminal of the differential circuit, and the output terminal of the amplifier circuit is connected to the input terminal of the processing module.

[0013] The amplification circuit is used to amplify the arc signal and send the amplified arc signal to the processing module.

[0014] In one possible implementation, the differential circuit includes a first operational amplifier, a first resistor, a second resistor, and a voltage feedback unit;

[0015] The first end of the first resistor is connected to the output terminal of the first sampling circuit, and the second end of the first resistor is connected to the negative input terminal of the first operational amplifier; the first end of the second resistor is connected to the output terminal of the second sampling circuit; and the second end of the second resistor is connected to the positive input terminal of the first operational amplifier.

[0016] The first end of the voltage feedback unit is connected to the negative input terminal of the first operational amplifier, and the second end of the voltage feedback unit is connected to the output terminal of the first operational amplifier.

[0017] In one possible implementation, the voltage feedback unit includes a first capacitor and a third resistor;

[0018] The first terminal of the first capacitor and the first terminal of the third resistor are both connected to the negative input terminal of the first operational amplifier, and the second terminal of the first capacitor and the second terminal of the third resistor are both connected to the output terminal of the first operational amplifier.

[0019] In one possible implementation, the differential circuit further includes a second capacitor and a fourth resistor;

[0020] The first terminals of the second capacitor and the fourth resistor are both connected to the positive input terminal of the first operational amplifier, and the second terminals of the second capacitor and the fourth resistor are both grounded.

[0021] In one possible implementation, the differential circuit further includes a third capacitor;

[0022] The first end of the third capacitor is connected to the negative input terminal of the first operational amplifier, and the second end of the third capacitor is connected to the positive input terminal of the first operational amplifier.

[0023] In one possible implementation, the arc detection circuit further includes a high-pass filter circuit;

[0024] The input terminal of the high-pass filter circuit is connected to the output terminal of the differential circuit, and the output terminal of the high-pass filter circuit is connected to the input terminal of the amplifier circuit.

[0025] In one possible implementation, the sampling line of the first photovoltaic plate and the sampling line of the second photovoltaic plate are twisted together and then connected to the corresponding first sampling circuit and second sampling circuit.

[0026] In one possible implementation, the amplification circuit includes: a second operational amplifier and an amplification ratio unit;

[0027] The positive input terminal of the second operational amplifier is connected to the output terminal of the differential circuit, the negative input terminal of the second operational amplifier is connected to the first terminal of the amplification unit, the second terminal of the amplification unit is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the input terminal of the processing module.

[0028] Secondly, this utility model provides a photovoltaic system comprising a plurality of photovoltaic plates and an arc detection circuit as described in the first aspect above.

[0029] This utility model embodiment provides an arc detection circuit, which includes:

[0030] A first sampling circuit for acquiring the output electrical signal of the first photovoltaic panel; a second sampling circuit for acquiring the output electrical signal of the second photovoltaic panel; a positive input terminal connected to the output terminal of the first sampling circuit, and a negative input terminal connected to the output terminal of the second sampling circuit; a differential circuit for subtracting the output electrical signals of the first and second photovoltaic panels to output an arcing signal; and a processing module connected to the output terminal of the differential circuit for determining whether an arcing fault has occurred on the first or second photovoltaic panel based on the magnitude of the arcing signal. The differential circuit, by subtracting the output electrical signals of the two photovoltaic panels, can eliminate differential-mode interference and common-mode interference in the electrical signals, thereby obtaining an accurate electrical signal difference value. Then, based on the magnitude of the arcing signal, it directly determines whether an arcing fault has occurred, avoiding the influence of differential-mode interference and common-mode interference on arcing detection and improving the accuracy of arcing detection. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the arc detection circuit provided in an embodiment of the present invention;

[0033] Figure 2 This is a circuit diagram of the arc detection circuit provided in this embodiment of the utility model. Detailed Implementation

[0034] In the following description, specific details such as particular system structures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the present invention. However, those skilled in the art will understand that the present invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0036] Photovoltaic panel arcing refers to the phenomenon of electric arc discharge between photovoltaic panels in a photovoltaic power generation system due to voltage or voltage fluctuations. The resulting high temperature and high pressure effect can damage the photovoltaic panels, reduce energy conversion efficiency, and may cause fires.

[0037] In order to accurately detect the arcing discharge phenomenon of photovoltaic plates and take corresponding measures in a timely manner, this embodiment uses an arcing detection circuit to detect the arcing fault of photovoltaic plates.

[0038] See Figure 1 The diagram shows a schematic of the arc detection circuit provided in an embodiment of the present invention. The arc detection circuit includes:

[0039] The first sampling circuit 10 is used to collect the output electrical signal of the first photovoltaic plate;

[0040] The second sampling circuit 20 is used to collect the output electrical signal of the second photovoltaic plate;

[0041] The positive input terminal is connected to the output terminal of the first sampling circuit 10, and the negative input terminal is connected to the output terminal of the second sampling circuit 20; a differential circuit 30 is used to calculate the difference between the output electrical signal of the first photovoltaic plate and the output electrical signal of the second photovoltaic plate to output an arcing signal.

[0042] A processing module 50, connected to the output of the differential circuit 30, is used to determine whether the first photovoltaic plate or the second photovoltaic plate has experienced an arcing fault based on the arcing signal.

[0043] Specifically, a photovoltaic system includes multiple photovoltaic panels and an inverter. The output terminals of each photovoltaic panel are connected in parallel and then connected to the DC terminal of the inverter. The AC terminal of the inverter can be connected to the power grid.

[0044] Both the first sampling circuit 10 and the second sampling circuit 20 can be voltage sensors. The first sampling circuit 10 is used to acquire the output voltage of the first photovoltaic plate and uses this output voltage as the first output voltage. The second sampling circuit 20 is used to acquire the output voltage of the second photovoltaic plate and uses this output voltage as the second output voltage. The differential circuit 30 is used to acquire the first and second output voltages and calculate the difference between the first and second output voltages to obtain the arcing signal. Since both the first and second output voltages are subject to the same differential-mode and common-mode interference, subtracting the first and second output voltages can cancel out the differential-mode and common-mode interference in the first and second output voltages, thereby eliminating the differential-mode and common-mode interference in the output arcing signal. When the arcing signal is not subject to any interference, if there is an arcing fault in either the first or second photovoltaic plate, the arcing signal will not be zero; if there is no arcing fault in either the first or second photovoltaic plate, the arcing signal will be zero.

[0045] Specifically, the first sampling circuit 10 and the second sampling circuit 20 can also be current sensors. A resistor can also be connected in series between the negative input terminal of the first sampling circuit and the differential circuit, so that the current signal collected by the first sampling circuit is converted into a voltage signal and then input into the differential circuit. A resistor can also be connected in series between the positive input terminal of the second sampling circuit and the differential circuit, so that the current signal collected by the second sampling circuit is converted into a voltage signal and then input into the differential circuit.

[0046] The processing module 50 is used to detect the magnitude of the arcing signal. If the arcing signal is less than the first preset value, it is determined that the first photovoltaic plate or the second photovoltaic plate has not experienced an arcing fault. If the arcing signal is greater than or equal to the first preset value, it is determined that the first photovoltaic plate or the second photovoltaic plate has experienced an arcing fault.

[0047] As can be seen from the above embodiments, the differential circuit 30 can eliminate differential-mode interference and common-mode interference in the electrical signal by subtracting the output electrical signals of the two photovoltaic plates, thereby obtaining an accurate arcing signal. Then, based on the magnitude of the accurate arcing signal, it can directly determine whether an arcing fault has occurred, thus avoiding the influence of differential-mode interference and common-mode interference on arcing detection and improving the accuracy of arcing detection.

[0048] In one possible implementation, the arc detection circuit further includes an amplification circuit:

[0049] The input terminal of the amplifier circuit is connected to the output terminal of the differential circuit, and the output terminal of the amplifier circuit is connected to the input terminal of the processing module.

[0050] The amplification circuit is used to amplify the arc signal and send the amplified arc signal to the processing module.

[0051] In this embodiment, since the arcing signal is a value around zero, in order to enable the processing module 50 to more accurately identify the arcing signal, this embodiment amplifies the arcing signal after obtaining it to obtain an amplified arcing signal. The processing module can accurately identify whether the photovoltaic plate has an arcing fault based on the amplified arcing signal, thereby improving the detection accuracy of arcing faults.

[0052] In one possible implementation, Figure 2 The circuit diagram of the arc detection circuit is shown below. (Refer to...) Figure 2 The differential circuit 30 includes a first operational amplifier U1B, a first resistor R1, a second resistor R2, and a voltage feedback unit;

[0053] The first end of the first resistor R1 is connected to the output terminal of the first sampling circuit 10, and the second end of the first resistor R1 is connected to the negative input terminal of the first operational amplifier U1B; the first end of the second resistor R2 is connected to the output terminal of the second sampling circuit 20; and the second end of the second resistor R2 is connected to the positive input terminal of the first operational amplifier U1B.

[0054] The first end of the voltage feedback unit is connected to the negative input terminal of the first operational amplifier U1B, and the second end of the voltage feedback unit is connected to the output terminal of the first operational amplifier U1B.

[0055] In this embodiment, the first operational amplifier U1B is used to calculate the difference between the first input voltage and the second input voltage, thereby canceling out differential-mode interference and common-mode interference in the two voltage signals.

[0056] Furthermore, since the arc signal is similar to white noise, its energy is distributed across almost the entire spectrum, manifesting as energy elevation in different frequency bands. However, in photovoltaic systems, the high-frequency switching noise of the inverter overlaps with the arc signal frequency, thus requiring a filter to separate the arc signal. This embodiment incorporates a voltage feedback unit, which performs low-pass filtering on the output electrical signals of the first and second photovoltaic panels. By setting the low-pass cutoff frequency through the voltage feedback unit, high-frequency signals are filtered out, thereby improving the quality of the arc signal.

[0057] In one possible implementation, refer to Figure 2 The voltage feedback unit includes a first capacitor C1 and a third resistor R3;

[0058] The first terminal of the first capacitor C1 and the first terminal of the third resistor R3 are both connected to the negative input terminal of the first operational amplifier U1B, and the second terminal of the first capacitor C1 and the second terminal of the third resistor R3 are both connected to the output terminal of the first operational amplifier U1B.

[0059] Specifically, the low-pass cutoff frequency of the voltage feedback unit is determined by the first capacitor C1 and the third resistor R3; the output electrical signal of the first photovoltaic plate is divided and low-pass filtered to generate a feedback voltage signal, and the difference between the output electrical signal of the first photovoltaic plate and the output electrical signal of the second photovoltaic plate is adjusted by the feedback voltage signal to obtain the arcing signal.

[0060] In this embodiment, a power supply signal VCC is also required for the first operational amplifier U1B, and the first operational amplifier U1B is grounded to VSS.

[0061] In one possible implementation, refer to Figure 2 The differential circuit 30 further includes a second capacitor C2 and a fourth resistor R4;

[0062] The first terminals of the second capacitor C2 and the fourth resistor R4 are both connected to the positive input terminal of the first operational amplifier U1B, and the second terminals of the second capacitor C2 and the fourth resistor R4 are both grounded.

[0063] In one possible implementation, refer to Figure 2 The differential circuit 30 also includes a third capacitor C3;

[0064] The first terminal of the third capacitor C3 is connected to the negative input terminal of the first operational amplifier U1B, and the second terminal of the third capacitor C3 is connected to the positive input terminal of the first operational amplifier U1B.

[0065] In this embodiment, the third capacitor C3 can perform preliminary filtering on the output signals of the two photovoltaic plates input to the differential circuit 30.

[0066] In one possible implementation, refer to Figure 2 The arc detection circuit also includes a high-pass filter circuit;

[0067] The input terminal of the high-pass filter circuit is connected to the output terminal of the differential circuit 30, and the output terminal of the high-pass filter circuit is connected to the input terminal of the amplifier circuit 40.

[0068] In this embodiment, the high-pass filter circuit and the voltage feedback unit in the differential circuit 30 jointly realize the band-pass filtering of the arcing signal, effectively filtering out unwanted frequency bands, retaining the characteristic frequency of the arcing signal, realizing the function of blocking DC and passing AC, and reducing the interference of the inverter's high-frequency switching noise on the arcing signal.

[0069] In one possible implementation, refer to Figure 2 The high-pass filter circuit includes a fifth capacitor C5 and a fifth resistor R5;

[0070] The first end of the fifth capacitor C5 is connected to the output end of the differential circuit 30, and the second end of the fifth capacitor C5 is connected to the input end of the amplifier circuit 40 and the first end of the fifth resistor R5 respectively; the second end of the fifth resistor R5 is grounded.

[0071] In this embodiment, the first sampling circuit 10 and the second sampling circuit 20 typically have a reference voltage. That is, the value sampled by the first sampling circuit 10 and the second sampling circuit 20 is the reference voltage plus the accurate output voltage value of the photovoltaic plate. This reference voltage will cause the sampled output voltage value to be inaccurate, affecting the detection of the arcing signal. Although this reference voltage can be partially canceled out during the differential calculation process of the differential circuit 30, since the reference voltage of each sampling circuit may be different, this embodiment can also use a high-pass filter circuit to remove the reference voltage bias of the sampling circuit, and process the arcing signal into a more accurate arcing signal that fluctuates around zero.

[0072] In one possible implementation, refer to Figure 2 The amplifier circuit 40 includes: a second operational amplifier U2B and an amplification ratio unit;

[0073] The positive input terminal of the second operational amplifier U2B is connected to the output terminal of the differential circuit 30, the negative input terminal of the second operational amplifier U2B is connected to the first terminal of the amplification unit, the second terminal of the amplification unit is connected to the output terminal of the second operational amplifier U2B, and the output terminal of the second operational amplifier U2B is connected to the input terminal of the processing module 50.

[0074] In this embodiment, the amplifier circuit 40 is a non-inverting amplifier, which amplifies the arcing signal by a preset factor to a size that the processing module 50 can recognize, so that the processing module 50 can receive and recognize the arcing signal.

[0075] In one possible implementation, refer to Figure 2 The amplification unit includes a sixth resistor R6 and a seventh resistor R7;

[0076] The first end of the sixth resistor R6 and the first end of the seventh resistor R7 are both connected to the negative input terminal of the second operational amplifier U2B. The second end of the sixth resistor R6 is connected to the power supply terminal, and the second end of the seventh resistor R7 is connected to the output terminal of the second operational amplifier U2B.

[0077] In this embodiment, through the connection relationship between the sixth resistor R6 and the seventh resistor R7, the amplifier circuit 40 can amplify the arcing signal. This amplification is achieved by multiplying the arcing signal by a factor of 1.5. The amplification ratio can be determined based on a reference voltage that the processing module 50 can accurately identify.

[0078] In one possible implementation, the sampling line of the first photovoltaic plate is twisted with the sampling line of the second photovoltaic plate and then connected to the corresponding first sampling circuit and second sampling circuit.

[0079] In this embodiment, the output cables of the first photovoltaic plate and the second photovoltaic plate are twisted into a twisted pair, which can cancel out the electromagnetic waves radiated during transmission, thereby effectively reducing the interference of external electromagnetic fields on the twisted pair and the interference between the twisted pair wires.

[0080] In one possible implementation, the processing module 50 includes a digital signal processor (DSP).

[0081] In this embodiment, the processing module can also be other microprocessor chips.

[0082] Specifically, the arcing signal is obtained through the DSP. When the arcing signal is greater than the first preset value, it is determined that the first photovoltaic plate or the second photovoltaic plate has an arcing fault.

[0083] In this embodiment, the arc detection circuit also includes an arc alarm device. When the processing module 50 detects an arc fault in the first photovoltaic plate or the second photovoltaic plate, it can trigger an alarm through the arc alarm device. The arc alarm device can be a virtual alarm module on the display screen or an audible and visual alarm.

[0084] The processing module 50 can also control the corresponding switching device to cut off when an arcing fault is detected, so as to avoid damage to the solar panel, fire accident, etc. caused by the arcing fault.

[0085] The arc detection circuit also includes a wireless communication module. The processing module 50 is connected to the operator's terminal through the wireless communication module. When an arc fault occurs, the processing module 50 generates arc fault information and sends it to the corresponding operator's terminal through the wireless communication module.

[0086] Secondly, this utility model provides a photovoltaic system comprising a plurality of photovoltaic plates and an arc detection circuit as described in the first aspect above.

[0087] In this embodiment, the above-mentioned arc detection circuit can be set between two adjacent photovoltaic plates in the photovoltaic system to detect arc faults of the photovoltaic plates in a timely manner and take corresponding effective measures to avoid damage to the devices caused by arc faults and ensure the safety of devices and personnel.

[0088] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. An arc detection circuit, characterized by, The application relates to a circuit for detecting an arc fault of a photovoltaic panel. The circuit comprises: a first sampling circuit for collecting an output electric signal of a first photovoltaic panel; a second sampling circuit for collecting an output electric signal of a second photovoltaic panel; a differential circuit having a positive input end connected with an output end of the first sampling circuit and a negative input end connected with an output end of the second sampling circuit, for differentiating the output electric signal of the first photovoltaic panel and the output electric signal of the second photovoltaic panel and outputting an arc signal; 2. The arc detection circuit of claim 1, wherein, a processing module connected with an output end of the differential circuit, for determining whether an arc fault occurs in the first photovoltaic panel or the second photovoltaic panel based on the arc signal. The arc detection circuit further comprises an amplification circuit: an input end of the amplification circuit is connected with an output end of the differential circuit, and an output end of the amplification circuit is connected with an input end of the processing module; 3. The arc detection circuit of claim 1, wherein, the amplification circuit is used for amplifying the arc signal and sending the amplified arc signal to the processing module. The differential circuit comprises a first operational amplifier, a first resistor, a second resistor and a voltage feedback unit; a first end of the first resistor is connected with an output end of the first sampling circuit, and a second end of the first resistor is connected with a negative input end of the first operational amplifier; a first end of the second resistor is connected with an output end of the second sampling circuit; a second end of the second resistor is connected with a positive input end of the first operational amplifier; 4. The arc detection circuit of claim 3, wherein, a first end of the voltage feedback unit is connected with the negative input end of the first operational amplifier, and a second end of the voltage feedback unit is connected with an output end of the first operational amplifier. The voltage feedback unit comprises a first capacitor and a third resistor; 5. The arc detection circuit of claim 3, wherein, a first end of the first capacitor and a first end of the third resistor are both connected with the negative input end of the first operational amplifier, and a second end of the first capacitor and a second end of the third resistor are both connected with the output end of the first operational amplifier. The differential circuit further comprises a second capacitor and a fourth resistor; 6. The arc detection circuit of claim 3, wherein, a first end of the second capacitor and a first end of the fourth resistor are both connected with the positive input end of the first operational amplifier, and a second end of the second capacitor and a second end of the fourth resistor are both grounded. The differential circuit further comprises a third capacitor; 7. The arc detection circuit of claim 2, wherein, a first end of the third capacitor is connected with the negative input end of the first operational amplifier, and a second end of the third capacitor is connected with the positive input end of the first operational amplifier. The arc detection circuit further comprises a high-pass filter circuit; 8. The arc detection circuit of claim 1, wherein, an input end of the high-pass filter circuit is connected with an output end of the differential circuit, and an output end of the high-pass filter circuit is connected with an input end of the amplification circuit.

9. The arc detection circuit of claim 2, wherein, The sampling line of the first photovoltaic panel is twisted with the sampling line of the second photovoltaic panel and then connected with the corresponding first sampling circuit and second sampling circuit. The amplification circuit comprises a second operational amplifier and an amplification ratio unit; The positive input end of the second operational amplifier is connected with the output end of the differential circuit, the negative input end of the second operational amplifier is connected with the first end of the amplification ratio unit, and the second end of the amplification ratio unit is connected with the output end of the second operational amplifier; and the output end of the second operational amplifier is connected with the input end of the processing module.

10. A photovoltaic system characterized by, Comprising: a plurality of photovoltaic plates and a striking arc detection circuit as claimed in any of claims 1 to 9.

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