Fault detection circuit, method, DC power supply system and DC appliance

Abstract

The present invention discloses a fault detection circuit, method, DC power supply system and DC appliance. The circuit includes: a detection module, which is arranged at the DC interface of the DC power supply system and connected to a signal processor, and is used to collect physical parameters at the interface and convert them into electrical signals and send them to the signal processor; the signal processor is used to determine the fault type at the interface according to the electrical signals. Through the present invention, various faults at the DC interface can be accurately detected, and the reliability of the entire DC power supply system can be improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a fault detection circuit, method, direct current power supply system and direct current appliance. Background Art

[0002] Nowadays, with the development of power electronics technology and electronic information technology, high-power inverters and photovoltaic air conditioners are becoming more and more widely used, and as a result, the number of input channels on the photovoltaic power generation side is also increasing. When a new DC power supply system is installed for the first time, the DC interface may have poor contact; the old DC power supply system may be loose due to long-term operation and interference from external factors, which may also cause the above interface to loosen. Both of the above situations will cause arcing at the wiring point. Taking the photovoltaic power supply system as an example, when multiple photovoltaic strings are connected in parallel to the power load, there is a possibility that one or several photovoltaic strings will be connected to the positive and negative terminals of the DC / DC converter in reverse during the installation process. Figure 1 The comparison diagram of the current direction of the photovoltaic string when it is connected forward and reverse, where the actual line is the current direction when it is connected forward, and the dotted line is the current direction when it is connected reversely. Figure 1 As shown, when reversely connected, the current of the crystal diode in the DC / DC converter flows in the reverse direction, which will cause the positive and negative short circuit of the photovoltaic string. When one or several photovoltaic strings have this fault, other photovoltaic strings that have not failed can still operate normally. Therefore, it is impossible to know whether there is a situation of reverse connection of one or several photovoltaic strings on the photovoltaic power generation side. Long-term operation under this fault may cause the reliability of the photovoltaic power supply system to decrease. In addition, since the interface is exposed to the environment all year round, the protective layer is prone to damage, resulting in the exposure of the line, etc., causing serious safety hazards. In the current DC power supply system, there is no detection scheme that can detect the above-mentioned faults at the same time.

[0003] With regard to the problem that there are many types of faults in the DC interface in the prior art and that they cannot be detected simultaneously, no effective solution has been proposed yet. Summary of the invention

[0004] The embodiments of the present invention provide a fault detection circuit, method, DC power supply system and DC appliance to solve the problem in the prior art that there are many types of faults in the DC interface and they cannot be detected simultaneously.

[0005] In order to solve the above technical problems, the present invention provides a fault detection circuit, wherein the circuit comprises:

[0006] A detection module, arranged at the DC interface of the DC power supply system, connected to a signal processor, and used for collecting physical parameters at the interface and converting them into electrical signals and sending them to the signal processor;

[0007] The signal processor is used to determine the fault type at the interface according to the electrical signal.

[0008] Furthermore, the physical parameters include temperature and light intensity.

[0009] Furthermore, the detection module includes:

[0010] a first detection unit, configured to detect the temperature at the interface, and generate a first electrical signal based on the temperature at the interface and output it to the signal processor;

[0011] a second detection unit, configured to detect the light intensity at the interface, and generate a second electrical signal based on the light intensity at the interface and output it to the signal processor;

[0012] The signal processor is specifically used to determine the fault type at the interface according to the voltage value carried by the first electrical signal and the voltage value carried by the second electrical signal.

[0013] Furthermore, the first detection unit includes:

[0014] A thermistor is arranged at the interface, with a first end connected to a voltage source and a second end connected to the signal processor, and is used to make the voltage value carried by the first signal greater than a first reference voltage when the temperature at the interface is higher than a first threshold.

[0015] Furthermore, the first detection unit further includes:

[0016] The first follower has a first input terminal connected to the second terminal of the thermistor, a second input terminal connected to its own output terminal, and an output terminal connected to the signal processor.

[0017] Furthermore, the first detection unit further includes:

[0018] A first resistor has a first end grounded and a second end connected between the second end of the thermistor and the first input end of the first follower, and is used to control the magnitude of an input voltage of the first input end of the first follower.

[0019] A first capacitor has a first end connected to ground and a second end connected between the second end of the thermistor and the first input end of the first follower, and is used for filtering the voltage output from the second end of the thermistor.

[0020] Furthermore, the second detection unit includes:

[0021] A photoresistor is arranged at the interface, with a first end connected to a voltage source and a second end connected to the signal processor, and is used to make the voltage carried by the second electrical signal greater than a second reference voltage when the light intensity at the interface is higher than a second threshold.

[0022] Furthermore, the second detection unit further includes:

[0023] The second follower has an input end connected to the first end of the photoresistor, a second input end connected to its own output end, and an output end connected to the signal processor.

[0024] Furthermore, the second detection unit further includes:

[0025] A second resistor has a first end grounded and a second end connected between the second end of the photoresistor and the first input end of the second follower, and is used to control the magnitude of the input voltage of the first input end of the second follower.

[0026] The second capacitor has a first end connected to ground and a second end connected between the second end of the photoresistor and the first input end of the second follower, and is used for filtering the voltage output from the second end of the photoresistor.

[0027] The present invention also provides a DC power supply system, comprising at least one DC interface. The DC power supply system also comprises: at least one of the above-mentioned fault detection circuits, wherein the fault detection circuits are arranged at each DC interface in a one-to-one correspondence.

[0028] Furthermore, the DC power supply system is a photovoltaic power supply system.

[0029] The present invention also provides a DC electrical appliance, comprising a load and the above-mentioned DC power supply system.

[0030] Furthermore, the DC electrical appliance is a photovoltaic air conditioner.

[0031] The present invention also provides a fault detection method, the method comprising:

[0032] Acquire the electrical signal output by the detection module; wherein the detection module is arranged at the DC interface of the DC power supply system and connected to the signal processor;

[0033] The fault type at the interface is determined according to the electrical signal.

[0034] Furthermore, the electrical signal includes:

[0035] A first electrical signal and a second electrical signal; wherein the first electrical signal is generated based on the temperature at the interface between the photovoltaic string and the DC / DC converter; and the second electrical signal is generated based on the light intensity at the interface between the photovoltaic string and the DC / DC converter.

[0036] Furthermore, before determining the fault type at the interface according to the electrical signal, the method further includes:

[0037] Determine whether a voltage value carried by a first electrical signal output by the detection module is less than or equal to a first reference voltage, and a voltage value carried by a second electrical signal output by the detection module is less than or equal to a second reference voltage;

[0038] If yes, it is determined that no fault occurs at the interface;

[0039] If not, it is determined that a fault occurs at the interface, triggering the process of determining the type of fault at the interface based on the electrical signal.

[0040] Further, judging the fault type at the interface according to the electrical signal includes:

[0041] If the voltage value carried by the first electrical signal is less than or equal to a first reference voltage, and the voltage value carried by the second electrical signal is greater than a second reference voltage, it is determined that the fault type is a damage to the protective layer;

[0042] If the voltage value carried by the first electrical signal is greater than a first reference voltage, and the voltage value carried by the second electrical signal is less than or equal to a second reference voltage, then determining that the fault type is a reverse connection of the terminal;

[0043] If the voltage value carried by the first electrical signal is greater than a first reference voltage, and the voltage value carried by the second electrical signal is greater than a second reference voltage, it is determined that the fault type is arcing at the interface.

[0044] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the fault detection method as described above is implemented.

[0045] By applying the technical solution of the present invention, a detection module is arranged at the DC interface of a DC power supply system, physical parameters at the interface are collected and converted into electrical signals and sent to a signal processor. The signal processor determines whether a fault occurs based on the above physical parameters, and various faults at the DC interface can be accurately detected, thereby improving the reliability of the entire DC power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a comparison diagram of the current direction when the photovoltaic string is connected forward and reverse;

[0047] Figure 2 is a structural diagram of a fault detection circuit according to an embodiment of the present invention;

[0048] Figure 3 is a structural diagram of a fault detection circuit according to another embodiment of the present invention;

[0049] Figure 4 is a structural diagram of a fault detection circuit according to another embodiment of the present invention;

[0050] Figure 5 is a structural diagram of a photovoltaic power supply system according to an embodiment of the present invention;

[0051] Figure 6 is a structural diagram of a photovoltaic air conditioner according to an embodiment of the present invention;

[0052] Figure 7 is a flow chart of a fault detection method according to an embodiment of the present invention;

[0053] Figure 8 FIG. 4 is a flow chart of another fault detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0056] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0057] It should be understood that although the terms first, second, etc. may be used to describe the detection unit in the embodiments of the present invention, these detection units should not be limited to these terms. These terms are only used to distinguish detection units that implement different functions. For example, without departing from the scope of the embodiments of the present invention, the first detection unit may also be referred to as the second detection unit, and similarly, the second detection unit may also be referred to as the first detection unit.

[0058] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0059] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0060] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0061] Example 1

[0062] This embodiment provides a fault detection circuit, which is applied to a DC power supply system. This embodiment takes a photovoltaic power supply system as an example to explain the technical solution of the present invention in detail. Figure 2 is a structural diagram of a fault detection circuit according to an embodiment of the present invention, as shown in Figure 2 As shown, the fault detection circuit includes:

[0063] The detection module 1 is arranged at the interface (i.e., the DC interface) between the photovoltaic string 3 and the DC / DC converter 4 of the photovoltaic power supply system, and is connected to the signal processor to collect the physical parameters at the interface and convert them into electrical signals and send them to the signal processor; wherein the above-mentioned physical parameters include temperature and light intensity.

[0064] Since the main faults at the interface between the photovoltaic string 3 and the DC / DC converter 4 include arcing, reverse connection of terminals and damage to the protective layer, when the above faults occur, the physical parameters at the interface between the photovoltaic string 3 and the DC / DC converter 4, such as temperature and light intensity, will change, and when different faults occur, the changed physical parameters are different. By detecting the physical parameters at the interface between the photovoltaic string 3 and the DC / DC converter 4, it is possible to determine whether a fault has occurred and what specific fault has occurred. Since the physical signal collected by the detection module 1 is an analog signal, it is necessary to convert the above analog signal into an electrical signal before judgment can be made. Therefore, the detection module 1 is also used to convert the above physical parameters into electrical signals and send them to the signal processor.

[0065] The signal processor 2 is used to determine the fault type at the interface between the photovoltaic string 3 and the DC / DC converter 4 according to the electrical signal output by the detection module 1. In specific implementation, the signal processor 2 can select a digital signal processing chip DSP.

[0066] The fault detection circuit of this embodiment, through the detection module 1 set at the interface between the photovoltaic string 3 and the DC / DC converter 4 of the photovoltaic power supply system, collects the physical parameters at the interface and converts them into electrical signals and sends them to the signal processor 2. The signal processor 2 determines whether a fault occurs according to the above physical parameters. It can accurately detect various faults at the interface between the photovoltaic string and the DC / DC converter, thereby improving the reliability of the entire photovoltaic power supply system.

[0067] Example 2

[0068] This embodiment provides another fault detection circuit. According to the above, the above physical parameters include temperature and light intensity. Therefore, a corresponding detection unit is required to detect the above physical parameters. Figure 3 FIG. 4 is a structural diagram of a fault detection circuit according to another embodiment of the present invention. Figure 3As shown, the above-mentioned detection module includes: a first detection unit 101, which is used to detect the temperature at the interface between the photovoltaic string 3 and the DC / DC converter 4, and based on the temperature at the interface, generates a first electrical signal to output to the signal processor 2; a second detection unit 102, which is used to detect the light intensity at the interface between the photovoltaic string 3 and the DC / DC converter 4, and based on the light intensity at the above-mentioned interface, generates a second electrical signal to output to the signal processor 2; in this embodiment, the signal processor 2 is specifically used to: determine the fault type at the interface according to the voltage value V1 carried by the first electrical signal and the voltage value V2 carried by the second electrical signal. For example, when the voltage value V1 carried by the first electrical signal output by the detection module is less than or equal to the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is less than or equal to the second reference voltage Vref2; it is determined that no fault has occurred at the interface; when the voltage value V1 carried by the first electrical signal output by the detection module is less than or equal to the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is greater than the second reference voltage Vref2, it is determined that a fault has occurred, and the fault type is damage to the protective layer; when the voltage value V1 carried by the first electrical signal output by the detection module is greater than the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is less than or equal to the second reference voltage Vref2, it is determined that a fault has occurred, and the fault type is reverse connection of the terminals; when the voltage value V1 carried by the first electrical signal output by the detection module is greater than the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is greater than the second reference voltage Vref2, it is determined that a fault has occurred, and the fault type is arcing at the interface.

[0069] Figure 4 FIG. 4 is a structural diagram of a fault detection circuit according to another embodiment of the present invention. Figure 4 As shown, in order to realize the generation of electrical signals with different voltage values ​​according to the temperature at the interface, the first detection unit 101 includes: a thermistor Ra, which is arranged at the interface, and the first end of which is connected to the voltage source Vcc, and the second end of which is connected to the signal processor 2, and is used to make the voltage value carried by the first signal greater than the first reference voltage Vref1 when the temperature at the interface is higher than the first threshold. In this embodiment, the thermistor Ra can be a negative temperature coefficient thermistor Ra, and its characteristic is that the resistance value decreases as the temperature of the environment increases. When the temperature at the interface is higher than the first threshold, the resistance value of the thermistor Ra decreases to below a certain threshold, and the voltage drop at both ends also decreases. Since the voltage output by the voltage source Vcc is stable and unchanged, the voltage value V1 carried by the first electrical signal increases to be greater than the first reference voltage Vref1. It should be noted that this embodiment only takes the thermistor Ra as a negative temperature coefficient thermistor Ra as an example. In other embodiments of the present invention, the thermistor Ra can also be a positive temperature coefficient thermistor Ra.

[0070] In order to achieve voltage buffering and isolation, such as Figure 4 As shown, the first detection unit 101 also includes: a first follower U1, whose first input end is connected to the second end of the thermistor Ra, whose second input end is connected to its own output end, and whose output end is also connected to the signal processor 2. The first follower U1 can avoid the signal loss caused by the high output impedance and the low input impedance of the next stage to a certain extent, and plays a role of connecting the upper and lower stages. Since the follower has the characteristics of high input impedance and low output impedance, it presents a high impedance state to the upper stage circuit (thermistor Ra) and a low impedance state to the next stage circuit (signal processor 2), so as to isolate the front and rear stage circuits and eliminate the mutual influence between them.

[0071] Since the follower and the signal processor 2 have operating voltage limitations, their input voltage cannot be too high and needs to be lower than a certain threshold. In order to control the voltage at the first input terminal of the first follower U1, the above-mentioned first detection unit 101 also includes: a first resistor R1, whose first end is grounded, and whose second end is connected between the second end of the thermistor Ra and the first input terminal of the first follower U1, and is used to control the input voltage of the first input terminal of the first follower U1.

[0072] Since the follower has high accuracy, voltage fluctuations will affect the output result of the follower. In order to ensure the stability of the voltage output from the second end of the thermistor Ra, the first detection unit 101 also includes: a first capacitor C1, whose first end is grounded, and whose second end is connected between the second end of the thermistor Ra and the first input end of the first follower U1, for filtering the voltage output from the second end of the thermistor Ra.

[0073] Similarly, in order to realize the generation of electrical signals with different voltage values ​​according to the light intensity at the interface, such as Figure 3 As shown, the second detection unit 102 includes: a photoresistor Rb, which is arranged at the above-mentioned interface, a first end of which is connected to the voltage source Vcc, and a second end is connected to the signal processor 2. The characteristic of the photoresistor Rb is that the resistance value decreases with the increase of the light intensity of the environment. When the light intensity at the above-mentioned interface is greater than the second threshold value, the resistance value of the photoresistor Rb decreases to below a certain threshold value, and the voltage drop at both ends also decreases. Since the voltage output by the voltage source Vcc is stable, the voltage value V2 carried by the second electrical signal increases to be greater than the second reference voltage Vref2.

[0074] Also in order to achieve voltage buffering and isolation, such as Figure 4 As shown, the second detection unit 102 further includes: a second follower U2 , whose first input end is connected to the second end of the photoresistor Rb, whose second input end is connected to its own output end, and whose output end is also connected to the signal processor 2 .

[0075] Since the follower and the signal processor 2 have working voltage limitations, their input voltage cannot be too high and needs to be lower than a certain threshold. In order to control the voltage of the first input terminal of the second follower U2, the above-mentioned second detection unit 102 also includes: a second resistor R2, whose first end is grounded, and whose second end is connected to the second end of the photoresistor Rb and the first input terminal of the second follower U2, for controlling the size of the input voltage of the first input terminal of the second follower U2.

[0076] Since the follower has high accuracy, voltage fluctuations will affect the output result of the follower. In order to ensure the stability of the voltage output from the second end of the thermistor Ra, the second detection unit 102 also includes: a second capacitor C2, whose first end is grounded, and whose second end is connected between the second end of the photoresistor Rb and the first input end of the second follower U2, for filtering the voltage output from the second end of the photoresistor Rb.

[0077] In a specific embodiment, the resistance of the thermistor Ra changes with the change of temperature; the resistance of the photoresistor Rb changes with the change of light intensity; the thermistor Ra and the photoresistor Rb are both installed inside the interface.

[0078] The first resistor R1 and the second resistor R2 are voltage-dividing resistors, which ensure that the voltage values ​​input to the first follower U1, the second follower U2 and the signal processor 2 are within the normal range; the first capacitor C1 and the second capacitor C2 play a filtering role; the first reference voltage Vref1 and the second reference voltage Vref2 are protection thresholds set inside the software. The selection of these two values ​​needs to ensure that the optimal values ​​are selected by multiple measurements under different working conditions and different powers when the system is running normally.

[0079] The first voltage V1 is the voltage value carried by the first electrical signal, and the second voltage V2 is the voltage value carried by the second electrical signal. The first electrical signal and the second electrical signal are output to the signal processor, which compares the first voltage V1 with the first reference voltage Vref1 in the software, and the second voltage V2 with the second reference voltage Vref2, and then makes a fault judgment. The first voltage V1 = the voltage value of Vcc * the resistance value of R1 / (the resistance value of R1 + the resistance value of Ra), and the second voltage V2 = the voltage value of Vcc * the resistance value of R2 / (the resistance value of R2 + the resistance value of Rb).

[0080] Example 3

[0081] This embodiment provides a DC power supply system, wherein the DC power supply device may be a photovoltaic power supply system. Figure 5 is a structural diagram of a photovoltaic power supply system according to an embodiment of the present invention, as shown in Figure 5As shown, the photovoltaic power supply system includes at least one photovoltaic string 3 and at least one DC / DC converter 4, and the photovoltaic strings 3 and the DC / DC converter 4 are connected one-to-one. The photovoltaic power supply system also includes: at least one fault detection circuit in the above-mentioned embodiment, wherein the fault detection circuit is arranged one-to-one at the interface between each photovoltaic string 3 and the corresponding DC / DC converter 4.

[0082] Example 4

[0083] This embodiment provides a DC appliance, which may be a photovoltaic air conditioner. Figure 6 is a structural diagram of a photovoltaic air conditioner according to an embodiment of the present invention, such as Figure 6 As shown, the photovoltaic air conditioner includes a load and also includes the photovoltaic power supply system in the above embodiment.

[0084] Example 5

[0085] This embodiment provides a fault detection method. Figure 7 is a flow chart of a fault detection method according to an embodiment of the present invention. Figure 7 As shown, the method includes:

[0086] S101, obtaining an electrical signal output by a detection module; wherein the detection module is arranged at a DC interface of a DC power supply system and connected to a signal processor.

[0087] Since the main faults at the DC interface include arcing, reverse connection of terminals and damage to the protective layer, when the above faults occur, the physical parameters at the DC interface, such as temperature and light intensity, will change, and the changed physical parameters are different under different faults. The detection module generates an electrical signal by detecting the physical parameters at the DC interface, and can determine whether a fault has occurred and what specific fault has occurred based on the electrical signal. Since the physical signal collected by the detection module is an analog signal, it is necessary to convert the above analog signal into an electrical signal before making a judgment. Therefore, the detection module is also used to convert the above physical parameters into electrical signals and send them to the signal processor.

[0088] S102: Determine the fault type at the DC interface according to the electrical signal output by the detection module.

[0089] The fault detection method of this embodiment, through a detection module set at the DC interface of the DC power supply system, collects physical parameters at the interface and converts them into electrical signals, and determines whether a fault occurs based on the above electrical signals. It can accurately detect various faults at the DC interface and improve the reliability of the entire DC power supply system.

[0090] Example 6

[0091] This embodiment provides another fault detection method. In this embodiment, in order to convert the temperature and light intensity at the DC interface into electrical signals respectively, the electrical signals output by the detection module include:

[0092] A first electrical signal and a second electrical signal; wherein the first electrical signal is generated according to the temperature at the DC interface; and the second electrical signal is generated according to the light intensity at the interface between the photovoltaic string and the DC / DC converter.

[0093] In the present embodiment, before determining the fault type at the DC interface according to the electrical signal output by the detection module, the method further includes: determining whether a voltage value V1 carried by a first electrical signal output by the detection module is less than or equal to a first reference voltage Vref1, and a voltage value V2 carried by a second electrical signal output by the detection module is less than or equal to a second reference voltage Vref2; if so, determining that no fault has occurred at the interface; if not, determining that a fault has occurred at the interface, triggering determination of the fault type at the DC interface according to the electrical signal output by the detection module.

[0094] The specific faults and judgment conditions are shown in Table 1 below:

[0095] Table 1 Conditional fault comparison table

[0096]

[0097] Specifically, as shown in Table 1, if the voltage value V1 carried by the first electrical signal output by the detection module is less than or equal to the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is greater than the second reference voltage Vref2, the fault type is determined to be damage to the protective layer; if the voltage value V1 carried by the first electrical signal output by the detection module is greater than the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is less than or equal to the second reference voltage Vref2, the fault type is determined to be reverse connection of the terminals; if the voltage value V1 carried by the first electrical signal output by the detection module is greater than the first reference voltage Vref1, and the voltage value V2 carried by the second electrical signal output by the detection module is greater than the second reference voltage Vref2, the fault type is determined to be arcing at the interface.

[0098] The temperature and light intensity at the DC interface are sampled through the hardware circuit, and the temperature is converted into a voltage value V1, and the light intensity is converted into V2, which are input into the signal processor and compared with the first reference voltage Vref1 and the second reference voltage Vref2 in the software. When V1>Vref1 and V2>Vref2, it indicates that a large amount of heat and light are generated at the interface. Since DC arcing will generate a large amount of arc heat and sparks, it can be determined that arcing has occurred at this interface. The signal processor outputs a signal to cut off the load in the circuit, extinguish the arc, and report the corresponding fault.

[0099] When V1>Vref1, V2≤Vref2, it indicates that a large amount of heat is generated at the interface, but the light intensity is not high. When the PV string terminals are reversed, the PV strings on this path will be short-circuited, thus generating a large amount of heat. Therefore, it can be determined that the terminals at the interface are reversed, causing a short circuit. The signal processor outputs a signal to cut off the load in the circuit and reports a corresponding fault.

[0100] When V1≤Vref1, but V2>Vref2, it indicates that a large amount of light is generated at the interface, but the temperature is not high. Due to years of use, the protective layer at the interface is easily damaged, resulting in exposed circuits. At this time, if the photoresistor inside the interface detects abnormal light and the temperature is within the normal range, it can be determined that the protective layer at the interface is damaged, and the signal processor outputs a signal to cut off the load in the circuit and report the corresponding fault.

[0101] Figure 8 FIG. 1 is a flow chart of another fault detection method according to an embodiment of the present invention. Figure 8 As shown, the method includes:

[0102] S1, controls the DC power supply system to power on.

[0103] S2, determine whether V1≤Vref1 and V2≤Vref2 are established, if yes, execute step S3, if no, execute step S4.

[0104] S3, determine that no fault has occurred.

[0105] S4, determine what type of fault has occurred according to specific conditions. If V1>Vref1 and V2>Vref2, execute step S5; if V1>Vref1 and V2≤Vref2, execute step S6; if V1≤Vref1 and V2>Vref2, execute step S7;

[0106] S5, determines that arcing occurs at the interface, cuts off the load in the circuit, extinguishes the arc, and reports an arcing fault.

[0107] S6, determines that the terminal reverse connection occurs at the interface, causing a short circuit, cuts off the load in the circuit, and reports a terminal reverse connection fault.

[0108] S7, determines that the protective layer at the interface is damaged, cuts off the load in the circuit, and reports a protective layer damage fault.

[0109] The method of this embodiment automatically disconnects the load to extinguish the arc when an arc is detected at the DC interface, and reports an arc fault to remind maintenance; after detecting a photovoltaic short circuit, the automatic circuit breaker is disconnected, and a reverse connection fault is reported to remind maintenance; after the system detects that the protective layer at the interface is damaged, the automatic circuit breaker is disconnected, and a protective layer damage fault is reported, thereby increasing the reliability of the installation and operation of the photovoltaic system.

[0110] The circuit embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0111] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fault detection circuit, applied to a DC power supply system, characterized in that: The circuit comprises: A detection module is provided at the DC interface of the DC power supply system and connected to the signal processor, and is used to collect physical parameters at the interface and convert them into electrical signals and send them to the signal processor; the detection module includes: a first detection unit, configured to detect the temperature at the interface, and generate a first electrical signal based on the temperature at the interface and output it to the signal processor; a second detection unit, configured to detect the light intensity at the interface, and generate a second electrical signal based on the light intensity at the interface and output it to the signal processor; The signal processor is used to determine the fault type at the interface according to the electrical signal; the signal processor is specifically used to determine the fault type at the interface according to the voltage value carried by the first electrical signal and the voltage value carried by the second electrical signal; The signal processor is also used to: determine whether the voltage value carried by the first electrical signal output by the detection module is less than or equal to the first reference voltage, and whether the voltage value carried by the second electrical signal output by the detection module is less than or equal to the second reference voltage; if so, determine that no fault has occurred at the interface; if not, determine that a fault has occurred at the interface, triggering the determination of the fault type at the interface based on the electrical signal.

2. The fault detection circuit according to claim 1, characterized in that: The physical parameters include temperature and light intensity.

3. The fault detection circuit according to claim 1, characterized in that: The first detection unit comprises: A thermistor is arranged at the interface, with a first end connected to a voltage source and a second end connected to the signal processor, and is used to make the voltage value carried by the first electrical signal greater than a first reference voltage when the temperature at the interface is higher than a first threshold.

4. The fault detection circuit according to claim 3, characterized in that: The first detection unit also includes: The first follower has a first input terminal connected to the second terminal of the thermistor, a second input terminal connected to its own output terminal, and an output terminal connected to the signal processor.

5. The fault detection circuit according to claim 4, characterized in that: The first detection unit also includes: A first resistor, a first end of which is grounded, and a second end of which is connected between the second end of the thermistor and the first input end of the first follower, and is used to control the magnitude of an input voltage at the first input end of the first follower; A first capacitor has a first end connected to ground and a second end connected between the second end of the thermistor and the first input end of the first follower, and is used for filtering the voltage output from the second end of the thermistor.

6. The fault detection circuit according to claim 1, characterized in that: The second detection unit comprises: A photoresistor is arranged at the interface, with a first end connected to a voltage source and a second end connected to the signal processor, and is used to make the voltage carried by the second electrical signal greater than a second reference voltage when the light intensity at the interface is higher than a second threshold.

7. The fault detection circuit according to claim 6, characterized in that: The second detection unit also includes: The second follower has an input end connected to the first end of the photoresistor, a second input end connected to its own output end, and an output end connected to the signal processor.

8. The fault detection circuit according to claim 7, characterized in that: The second detection unit also includes: A second resistor, a first end of which is grounded, and a second end of which is connected between the second end of the photoresistor and the first input end of the second follower, for controlling the magnitude of an input voltage at the first input end of the second follower; The second capacitor has a first end connected to ground and a second end connected between the second end of the photoresistor and the first input end of the second follower, and is used for filtering the voltage output from the second end of the photoresistor.

9. A DC power supply system, comprising at least one DC interface, the DC power supply system further comprising: At least one fault detection circuit according to any one of claims 1 to 8, wherein the fault detection circuit is arranged at each DC interface in a one-to-one correspondence.

10. The DC power supply system according to claim 9, characterized in that: The DC power supply system is a photovoltaic power supply system.

11. A DC electrical appliance, comprising a load, and also comprising the DC power supply system according to claim 9.

12. The DC electrical appliance according to claim 11, characterized in that: The DC electrical appliance is a photovoltaic air conditioner.

13. A fault detection method, characterized in that: The method comprises: Acquire the electrical signal output by the detection module; wherein the detection module is arranged at the DC interface of the DC power supply system and connected to the signal processor; Determine the fault type at the interface according to the electrical signal; the electrical signal includes: a first electrical signal and a second electrical signal; wherein the first electrical signal is generated according to the temperature at the interface between the photovoltaic string and the DC / DC converter; and the second electrical signal is generated according to the light intensity at the interface between the photovoltaic string and the DC / DC converter; Before determining the fault type at the interface according to the electrical signal, the method further includes: Determine whether a voltage value carried by a first electrical signal output by the detection module is less than or equal to a first reference voltage, and a voltage value carried by a second electrical signal output by the detection module is less than or equal to a second reference voltage; If yes, it is determined that no fault occurs at the interface; If not, it is determined that a fault occurs at the interface, triggering the process of determining the type of fault at the interface based on the electrical signal.

14. The fault detection method according to claim 13, characterized in that: Determining the fault type at the interface according to the electrical signal includes: If the voltage value carried by the first electrical signal is less than or equal to a first reference voltage, and the voltage value carried by the second electrical signal is greater than a second reference voltage, it is determined that the fault type is a damage to the protective layer; If the voltage value carried by the first electrical signal is greater than a first reference voltage, and the voltage value carried by the second electrical signal is less than or equal to a second reference voltage, then determining that the fault type is a reverse connection of the terminal; If the voltage value carried by the first electrical signal is greater than a first reference voltage, and the voltage value carried by the second electrical signal is greater than a second reference voltage, it is determined that the fault type is arcing at the interface.

15. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to claim 13 or 14 is implemented.

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