CN113655325A - Fault detection circuit and method, direct current power supply system and direct current electric appliance - Google Patents

Abstract

The invention discloses a fault detection circuit and method, a direct current power supply system and a direct current electric appliance. Wherein, this circuit includes: the detection module is arranged at a direct current interface of the direct current power supply system, is connected with the signal processor, and is used for acquiring physical parameters at the interface, converting the physical parameters into electric signals and sending the electric signals to the signal processor; and the signal processor is used for judging the fault type at the interface according to the electric signal. By the method and the device, various faults at the direct current interface can be accurately detected, and the reliability of the whole direct current power supply system is improved.

Description

Fault detection circuit and method, direct current power supply system and direct current electric appliance

Technical Field

The invention relates to the technical field of electronic power, in particular to a fault detection circuit and method, a direct current power supply system and a direct current electric appliance.

Background

Nowadays, with the development of power electronic technology and electronic information technology, high-power inverters and photovoltaic air conditioners are more and more widely applied, and the number of input circuits on the photovoltaic power generation side is more and more. When a new direct current power supply system is installed for the first time, poor contact may occur at a direct current interface; the old dc power supply system is interfered by external factors due to long-term operation, and may cause the interface to be loosened. Both of the above two situations can cause the arc discharge phenomenon at the connection position. Taking a photovoltaic power supply system as an example, when multiple photovoltaic strings are connected in parallel to an electric load, the possibility of connecting one or more photovoltaic strings with the positive and negative terminals of the DC/DC converter in the reverse direction exists in the installation process, fig. 1 is a comparison diagram of the current directions when the photovoltaic strings are connected in the positive direction and the reverse direction, wherein the current direction is realized when the photovoltaic string is connected positively, the dotted line is the current direction when the photovoltaic string is connected negatively, as shown in fig. 1, the current of the crystal diode in the DC/DC converter flows reversely when the photovoltaic string is connected negatively, which causes the problem of positive and negative short circuit of the photovoltaic string, after one or more photovoltaic string(s) has/have the fault, other photovoltaic string(s) which have not fault still can normally operate, therefore, whether a certain photovoltaic power generation side or a certain number of photovoltaic groups are connected in a reverse mode cannot be known, and the reliability of the photovoltaic power supply system can be reduced due to the fact that the photovoltaic power generation side is operated under the fault for a long time. In addition, the interface is exposed in the environment all the year round, so that the damage of the protective layer is easy to occur, the circuit is exposed and the like, and serious potential safety hazards are caused. In the current direct current power supply system, a detection scheme capable of simultaneously detecting the faults does not exist.

Aiming at the problems that in the prior art, the direct current interfaces have more fault types and cannot be detected simultaneously, an effective solution is not provided at present.

Disclosure of Invention

The embodiment of the invention provides a fault detection circuit, a fault detection method, a direct current power supply system and a direct current electric appliance, and aims to solve the problems that in the prior art, a direct current interface has more fault types and cannot be detected simultaneously.

In order to solve the above technical problem, the present invention provides a fault detection circuit, wherein the circuit includes:

the detection module is arranged at a direct current interface of the direct current power supply system, is connected with the signal processor, and is used for acquiring physical parameters at the interface, converting the physical parameters into electric signals and sending the electric signals to the signal processor;

and the signal processor is used for judging the fault type at the interface according to the electric signal.

Further, the physical parameters include temperature and illumination intensity.

Further, the detection module includes:

the first detection unit is used for detecting the temperature at the interface, generating a first electric signal based on the temperature at the interface and outputting the first electric signal to the signal processor;

the second detection unit is used for detecting the illumination intensity at the interface, generating a second electric signal based on the illumination intensity at the interface and outputting the second electric signal to the signal processor;

the signal processor is specifically configured to: and judging the fault type at the interface according to the voltage value carried by the first electric signal and the voltage value carried by the second electric signal.

Further, the first detection unit includes:

and the thermistor is arranged at the interface, the first end of the thermistor is connected with a voltage source, the second end of the thermistor is connected with the signal processor, and the thermistor is used for enabling the voltage value carried by the first signal to be greater than a first reference voltage when the temperature at the interface is higher than a first threshold value.

Further, the first detection unit further includes:

and a first input end of the first follower is connected with the second end of the thermistor, a second input end of the first follower is connected with an output end of the first follower, and an output end of the first follower is also connected with the signal processor.

Further, the first detection unit further includes:

and the first end of the first resistor is grounded, and the second end of the first resistor is connected between the second end of the thermistor and the first input end of the first follower and used for controlling the magnitude of the input voltage of the first input end of the first follower.

And the first end of the first capacitor is grounded, and the second end of the first capacitor is 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 by the second end of the thermistor.

Further, the second detection unit includes:

and the photoresistor is arranged at the interface, the first end of the photoresistor is connected with a voltage source, the second end of the photoresistor is connected with the signal processor, and the photoresistor is used for enabling the voltage carried by the second electric signal to be greater than a second reference voltage when the illumination intensity at the interface is higher than a second threshold value.

Further, the second detection unit further includes:

and the input end of the second follower is connected with the first end of the photosensitive resistor, the second input end of the second follower is connected with the output end of the second follower, and the output end of the second follower is also connected with the signal processor.

Further, the second detection unit further includes:

and the first end of the second resistor is grounded, and the second end of the second resistor is connected between the second end of the photoresistor and the first input end of the second follower and used for controlling the magnitude of the input voltage of the first input end of the second follower.

And the first end of the second capacitor is grounded, and the second end of the second capacitor is connected between the second end of the photoresistor and the first input end of the second follower and used for filtering the voltage output by the second end of the photoresistor.

The present invention further provides a dc power supply system, including at least one dc interface, the dc power supply system further including: and the fault detection circuits are arranged at each direct current interface in a one-to-one correspondence manner.

Further, the direct current power supply system is a photovoltaic power supply system.

The invention also provides a direct current device which comprises a load and the direct current power supply system.

Further, the direct current equipment is a photovoltaic air conditioner.

The invention also provides a fault detection method, which comprises the following steps:

acquiring an electric signal output by a detection module; the detection module is arranged at a direct current interface of the direct current power supply system and is connected with the signal processor;

and judging the fault type at the interface according to the electric signal.

Further, the electrical signal includes:

a first electrical signal and a second electrical signal; wherein the first electrical signal is generated as a function of temperature at an interface between the photovoltaic string and the DC/DC converter; the second electrical signal is generated as a function of the intensity of illumination at the interface between the photovoltaic string and the DC/DC converter.

Further, before determining the type of the fault at the interface according to the electrical signal, the method further includes:

judging whether a voltage value carried by a first electric signal output by the detection module is smaller than or equal to a first reference voltage and a voltage value carried by a second electric signal output by the detection module is smaller than or equal to a second reference voltage;

if yes, judging that no fault occurs at the interface;

if not, judging that the interface has a fault, and triggering to judge the fault type at the interface according to the electric signal.

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

if the voltage value carried by the first electric signal is less than or equal to a first reference voltage and the voltage value carried by the second electric signal is greater than a second reference voltage, judging that the fault type is the damage of the protective layer;

if the voltage value carried by the first electric signal is greater than a first reference voltage and the voltage value carried by the second electric signal is less than or equal to a second reference voltage, judging that the fault type is the reverse connection of the terminal;

and if the voltage value carried by the first electric signal is greater than a first reference voltage and the voltage value carried by the second electric signal is greater than a second reference voltage, judging that the fault type is arc discharge at the interface.

The present invention also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the fault detection method as described above.

By applying the technical scheme of the invention, the physical parameters at the interface are collected and converted into electric signals to be sent to the signal processor through the detection module arranged at the DC interface of the DC power supply system, and the signal processor judges whether a fault occurs according to the physical parameters, so that various faults at the DC interface can be accurately detected, and the reliability of the whole DC power supply system is improved.

Drawings

FIG. 1 is a comparison graph of current direction when photovoltaic string is connected in the forward direction and in the reverse direction;

FIG. 2 is a block diagram of a fault detection circuit according to an embodiment of the present invention;

FIG. 3 is a block diagram of a fault detection circuit according to another embodiment of the present invention;

FIG. 4 is a block diagram of a fault detection circuit according to yet another embodiment of the present invention;

FIG. 5 is a block diagram of a photovoltaic power system according to an embodiment of the present invention;

fig. 6 is a structural view of a photovoltaic air conditioner according to an embodiment of the present invention;

FIG. 7 is a flow chart of a fault detection method according to an embodiment of the invention;

fig. 8 is a flowchart of another fault detection method according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be understood that although the terms first, second, etc. may be used to describe the detection units in the embodiments of the present invention, the detection units should not be limited to these terms. These terms are only used to distinguish between detection units that perform different functions. For example, 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, without departing from the scope of the embodiments of the present invention.

The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.

Alternative embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Example 1

The present embodiment provides a fault detection circuit, which is applied to a dc power supply system, and the present embodiment takes a photovoltaic power supply system as an example to describe in detail a technical solution of the present invention, and fig. 2 is a structural diagram of the fault detection circuit according to the embodiment of the present invention, as shown in fig. 2, the fault detection circuit includes:

the detection module 1 is arranged at an interface (namely a direct current interface) between a photovoltaic group string 3 and a DC/DC converter 4 of a photovoltaic power supply system, is connected with a signal processor, and is used for collecting physical parameters at the interface, converting the physical parameters into electric signals and sending the electric signals to the signal processor; wherein the physical parameters include temperature and illumination intensity.

Since the major faults at the interface between the pv string 3 and the DC/DC converter 4 include arcing, reverse connection of terminals, and damage of a protection layer, when the above faults occur, physical parameters, such as temperature and illumination intensity, at the interface between the pv string 3 and the DC/DC converter 4 may change, and when different faults occur, the changed physical parameters are different, and by detecting the physical parameters at the interface between the pv string 3 and the DC/DC converter 4, whether the fault occurs or not, and what fault specifically occurs can be determined. Because the physical signal collected by the detection module 1 is an analog signal, the judgment can be performed only by converting the analog signal into an electrical signal, and therefore, the detection module 1 is further configured to convert the physical parameter into the electrical signal and send the electrical signal to the signal processor.

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

The fault detection circuit of the embodiment collects physical parameters at a connector through the detection module 1 arranged at the connector between the photovoltaic string 3 and the DC/DC converter 4 of the photovoltaic power supply system, converts the physical parameters into electric signals and sends the electric signals to the signal processor 2, and the signal processor 2 judges whether faults occur according to the physical parameters, so that various faults at the connector between the photovoltaic string and the DC/DC converter can be accurately detected, and the reliability of the whole photovoltaic power supply system is improved.

Example 2

This embodiment provides another fault detection circuit, according to the above, the above physical parameters include temperature and illumination intensity, so a corresponding detection unit is needed to detect the above physical parameters, fig. 3 is a structural diagram of a fault detection circuit according to another embodiment of the present invention, as shown in fig. 3, the above detection module includes: the first detection unit 101 is used for detecting the temperature at the interface between the photovoltaic string 3 and the DC/DC converter 4, and generating a first electrical signal based on the temperature at the interface and outputting the first electrical signal to the signal processor 2; the second detection unit 102 is configured to detect an illumination intensity at an interface between the photovoltaic string 3 and the DC/DC converter 4, and generate a second electrical signal based on the illumination intensity at the interface, and output the second electrical signal to the signal processor 2; in this embodiment, the signal processor 2 is specifically configured to: and judging the fault type at the interface according to the voltage value V1 carried by the first electric signal and the voltage value V2 carried by the second electric 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 Vref 2; judging that no fault occurs 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, determining that a fault occurs and the fault type is the damage of the protection 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, determining that a fault occurs, and the fault type is that the terminals are reversely connected; 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 occurs, and the fault type is arc discharge at the interface.

Fig. 4 is a structural diagram of a fault detection circuit according to another embodiment of the present invention, and as shown in fig. 4, in order to generate electrical signals with different voltage values according to the temperature at the interface, the first detection unit 101 includes: and the thermistor Ra is arranged at the interface, a first end of the thermistor Ra is connected with a voltage source Vcc, and a second end of the thermistor Ra is connected with the signal processor 2, and is used for enabling the voltage value carried by the first signal to be greater than a first reference voltage Vref1 when the temperature at the interface is higher than a first threshold value. In this embodiment, the thermistor Ra may be a negative temperature coefficient thermistor Ra, and has a characteristic that the resistance value decreases with the increase of the temperature of the environment, when the temperature at the interface is higher than the first threshold, the resistance value of the thermistor Ra decreases to be below a certain threshold, the voltage drop at both ends also decreases, and the voltage output by the voltage source Vcc is stable and unchanged, so the voltage value V1 carried by the first electrical signal increases to be greater than the first reference voltage Vref 1. In this embodiment, the thermistor Ra is merely exemplified as the negative temperature coefficient thermistor Ra, and in another embodiment of the present invention, the thermistor Ra may be a positive temperature coefficient thermistor Ra.

In order to achieve the voltage buffering and isolation function, as shown in fig. 4, the first detection unit 101 further includes: the first follower U1 has a first input terminal connected to the second terminal of the thermistor Ra, a second input terminal connected to its own output terminal, and an output terminal connected to the signal processor 2. The first follower U1 can avoid signal loss caused by higher output impedance and lower input impedance of the next stage to a certain extent, and plays a role in starting and stopping. Because the follower has the characteristics of high input impedance and low output impedance, the follower presents a high-impedance state for a previous-stage circuit (thermistor Ra) and presents a low-impedance state for a next-stage circuit (signal processor 2) so as to isolate the previous-stage circuit and the next-stage circuit and eliminate the mutual influence between the previous-stage circuit and the next-stage circuit.

Since the follower and signal processor 2 has an operating voltage limit, and its 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 first follower U1, the first detection unit 101 further includes: the first end of the first resistor R1 is grounded, and the second end thereof is connected between the second end of the thermistor Ra and the first input end of the first follower U1, so as to control the magnitude of the input voltage at the first input end of the first follower U1.

Since the precision of the follower is high, the output result of the follower is affected by the fluctuation of the voltage, and in order to ensure the stability of the voltage output from the second end of the thermistor Ra, the first detection unit 101 further includes: a first capacitor C1, having a first terminal connected to ground and a second terminal connected between the second terminal of the thermistor Ra and the first input terminal of the first follower U1, is used for filtering the voltage output from the second terminal of the thermistor Ra.

Similarly, in order to generate electrical signals with different voltage values according to the illumination intensity at the interface, as shown in fig. 3, the second detecting unit 102 includes: the photoresistor Rb is arranged at the interface, the first end of the photoresistor Rb is connected with a voltage source Vcc, the second end of the photoresistor Rb is connected with the signal processor 2, the resistance of the photoresistor Rb is reduced along with the increase of the illumination intensity of the environment, when the illumination intensity at the interface is greater than a second threshold value, the resistance of the photoresistor Rb is reduced below a certain threshold value, the voltage drop at the two ends is also reduced, and the voltage output by the voltage source Vcc is stable and unchanged, so that the voltage value V2 carried by the second electric signal is increased to be greater than a second reference voltage Vref 2.

Also to achieve the voltage buffering and isolation function, as shown in fig. 4, the second detecting unit 102 further includes: a second follower U2 has a first input connected to the second terminal of the photo resistor Rb, a second input connected to its own output, and an output connected to the signal processor 2.

Since the follower and signal processor 2 has an operating voltage limit, and its 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 second detection unit 102 further includes: the first end of the second resistor R2 is grounded, and the second end thereof is connected between the second end of the photosensitive resistor Rb and the first input end of the second follower U2, so as to control the magnitude of the input voltage at the first input end of the second follower U2.

Since the precision of the follower is high, the fluctuation of the voltage may affect the output result of the follower, and in order to ensure the stability of the voltage output from the second end of the thermistor Ra, the second detection unit 102 further includes: a second capacitor C2, having a first terminal connected to ground and a second terminal connected between the second terminal of the photoresistor Rb and the first input terminal of the second follower U2, is used for filtering the voltage outputted from the second terminal of the photoresistor Rb.

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

The first resistor R1 and the second resistor R2 are voltage dividing resistors, and ensure that the voltage values input into the first follower U1, the second follower U2 and the signal processor 2 are in a normal range; the first capacitor C1 and the second capacitor C2 play a role in filtering; the first reference voltage Vref1 and the second reference voltage Vref2 are protection thresholds set inside software, and the two values are selected to ensure that the selected optimal value is measured for many times under different working conditions and different powers when the system is running normally.

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

Example 3

This embodiment provides a direct current power supply system, where the direct current power supply device may be a photovoltaic power supply system, fig. 5 is a structural diagram of the photovoltaic power supply system according to an embodiment of the present invention, and as shown in fig. 5, the photovoltaic power supply system includes at least one photovoltaic string 3 and at least one DC/DC converter 4, the photovoltaic string 3 and the DC/DC converter 4 are connected in a one-to-one correspondence, and the photovoltaic power supply system further includes: the fault detection circuit in at least one of the above embodiments, wherein the fault detection circuits are arranged in a one-to-one correspondence at the interface between each photovoltaic string 3 and its corresponding DC/DC converter 4.

Example 4

The embodiment provides a direct current device, which may be a photovoltaic air conditioner, and fig. 6 is a structural diagram of the photovoltaic air conditioner according to the embodiment of the present invention, as shown in fig. 6, the photovoltaic air conditioner includes a load, and further includes a photovoltaic power supply system in the above embodiment.

Example 5

The present embodiment provides a fault detection method, and fig. 7 is a flowchart of the fault detection method according to the embodiment of the present invention, as shown in fig. 7, the method includes:

s101, acquiring an electric signal output by a detection module; the detection module is arranged at a direct current interface of the direct current power supply system and is connected with the signal processor.

Because main trouble when the direct current kneck includes that the arc is drawn, the terminal joins conversely and the protective layer is damaged, when above-mentioned trouble takes place, the physical parameter at the direct current kneck, for example temperature and illumination intensity all can change to, under the different trouble, the physical parameter that changes is different, and detection module is through detecting the physical parameter at the direct current kneck, generates the signal of telecommunication, can judge whether the trouble takes place according to this signal of telecommunication to and what trouble has specifically taken place. The physical signals collected by the detection module are analog signals, so that the judgment can be carried out only by converting the analog signals into electric signals, and the detection module is also used for converting the physical parameters into the electric signals and sending the electric signals to the signal processor.

And S102, judging the fault type at the direct current interface according to the electric signal output by the detection module.

According to the fault detection method, the physical parameters at the interface are collected and converted into the electric signals through the detection module arranged at the DC interface of the DC power supply system, whether faults occur or not is judged according to the electric signals, various faults at the DC interface can be accurately detected, and the reliability of the whole DC power supply system is improved.

Example 6

In this embodiment, in order to convert the temperature and the illumination intensity at the dc interface into electrical signals, the electrical signals output by the detection module include:

a first electrical signal and a second electrical signal; wherein the first electrical signal is generated according to a temperature at the DC interface; a second electrical signal is generated as a function of the intensity of illumination at the interface between the photovoltaic string and the DC/DC converter.

Before determining the type of the fault at the dc interface according to the electrical signal output by the detection module in this embodiment, the method further includes: judging whether a voltage value V1 carried by the first electric signal output by the detection module is less than or equal to a first reference voltage Vref1 and a voltage value V2 carried by the second electric signal output by the detection module is less than or equal to a second reference voltage Vref 2; if yes, judging that no fault occurs at the interface; if not, judging that the interface has a fault, and triggering to judge the fault type at the direct current interface according to the electric signal output by the detection module.

Specific failure and determination conditions are shown in table 1 below:

TABLE 1 Condition Fault Compare sheet

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, it is determined that the fault type is a protective layer breakage; 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 terminal reverse connection; and if the voltage value V1 carried by the first electric signal output by the detection module is greater than the first reference voltage Vref1, and the voltage value V2 carried by the second electric signal output by the detection module is greater than the second reference voltage Vref2, judging that the fault type is arc discharge at the interface.

The temperature and the illumination intensity at the direct current interface are sampled through a hardware circuit, the temperature is converted into a voltage value V1, the illumination intensity is converted into a voltage value V2, and the voltage value V2 is input into a signal processor and is compared with a first reference voltage Vref1 and a second reference voltage Vref2 inside software. When V1> Vref1 while V2> Vref2, it indicates that a large amount of heat and a large amount of light are generated at the interface. Because the direct current arc discharge can generate a large amount of arc heat and sparks, the interface can be judged to have the arc discharge phenomenon, and the signal processor outputs a signal to cut off the load in the circuit, so as to extinguish the arc and report a corresponding fault.

When V1 is greater than Vref1 and V2 is less than or equal to Vref2, the interface generates a large amount of heat, but the illumination intensity is not high, when the terminals of the photovoltaic string are reversely connected, the photovoltaic string in the circuit is short-circuited, and therefore a large amount of heat is generated, so that the fact that the terminals at the interface are reversely connected to cause short circuit can be judged, the signal processor outputs a signal to cut off the load in the circuit, and a corresponding fault is reported.

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. The protective layer is easy to damage at the interface due to year use, so that the circuit is exposed, at the moment, if the photoresistor in the interface detects abnormal light and the temperature is in a normal range, the protective layer at the interface can be judged to be damaged, and the signal processor outputs a signal to cut off a load in a circuit and report a corresponding fault.

Fig. 8 is a flowchart of another fault detection method according to an embodiment of the present invention, as shown in fig. 8, the method includes:

and S1, controlling the direct current power supply system to be powered on.

S2, judging whether V1 is not less than Vref1 and V2 is not less than Vref2, if yes, executing step S3, and if no, executing step S4.

And S3, judging that no fault occurs.

S4, judging which type of fault happens according to specific conditions, if V1> Vref1 and V2> Vref2, executing step S5; if V1> Vref1, and V2 ≦ Vref2, perform step S6; if V1 ≦ Vref1, and V2> Vref2, perform step S7;

and S5, judging that arc discharge occurs at the interface, cutting off the load in the circuit, extinguishing arc, and reporting arc discharge fault.

And S6, judging that the terminal reverse connection occurs at the interface, causing short circuit, cutting off the load in the circuit, and reporting the terminal reverse connection fault.

And S7, judging the damage of the protective layer at the interface, cutting off the load in the circuit, and reporting the damage fault of the protective layer.

According to the method, when the arc discharge phenomenon at the direct current interface is detected, the load can be automatically disconnected so as to achieve the arc extinguishing effect, and the arc discharge fault is reported to remind maintenance; after the photovoltaic short circuit is detected, the automatic circuit breaking circuit 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 can be disconnected, the fault of the damaged protective layer is reported, and the reliability of the installation and the operation of the photovoltaic system is improved.

The above-described circuit embodiments are only illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (18)

1. A fault detection circuit for use in a DC power supply system, the circuit comprising:

the detection module is arranged at a direct current interface of the direct current power supply system, is connected with the signal processor, and is used for acquiring physical parameters at the interface, converting the physical parameters into electric signals and sending the electric signals to the signal processor;

and the signal processor is used for judging the fault type at the interface according to the electric signal.

2. The fault detection circuit of claim 1, wherein the physical parameters include temperature and illumination intensity.

3. The fault detection circuit of claim 2, wherein the detection module comprises:

the first detection unit is used for detecting the temperature at the interface, generating a first electric signal based on the temperature at the interface and outputting the first electric signal to the signal processor;

the second detection unit is used for detecting the illumination intensity at the interface, generating a second electric signal based on the illumination intensity at the interface and outputting the second electric signal to the signal processor;

the signal processor is specifically configured to: and judging the fault type at the interface according to the voltage value carried by the first electric signal and the voltage value carried by the second electric signal.

4. The fault detection circuit of claim 3, wherein the first detection unit comprises:

and the thermistor is arranged at the interface, the first end of the thermistor is connected with a voltage source, the second end of the thermistor is connected with the signal processor, and the thermistor is used for enabling the voltage value carried by the first signal to be greater than a first reference voltage when the temperature at the interface is higher than a first threshold value.

5. The fault detection circuit of claim 4, wherein the first detection unit further comprises:

and a first input end of the first follower is connected with the second end of the thermistor, a second input end of the first follower is connected with an output end of the first follower, and an output end of the first follower is also connected with the signal processor.

6. The fault detection circuit of claim 5, wherein the first detection unit further comprises:

and the first end of the first resistor is grounded, and the second end of the first resistor is connected between the second end of the thermistor and the first input end of the first follower and used for controlling the magnitude of the input voltage of the first input end of the first follower.

And the first end of the first capacitor is grounded, and the second end of the first capacitor is 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 by the second end of the thermistor.

7. The fault detection circuit of claim 3, wherein the second detection unit comprises:

and the photoresistor is arranged at the interface, the first end of the photoresistor is connected with a voltage source, the second end of the photoresistor is connected with the signal processor, and the photoresistor is used for enabling the voltage carried by the second electric signal to be greater than a second reference voltage when the illumination intensity at the interface is higher than a second threshold value.

8. The fault detection circuit of claim 7, wherein the second detection unit further comprises:

and the input end of the second follower is connected with the first end of the photosensitive resistor, the second input end of the second follower is connected with the output end of the second follower, and the output end of the second follower is also connected with the signal processor.

9. The fault detection circuit of claim 8, wherein the second detection unit further comprises:

and the first end of the second resistor is grounded, and the second end of the second resistor is connected between the second end of the photoresistor and the first input end of the second follower and used for controlling the magnitude of the input voltage of the first input end of the second follower.

And the first end of the second capacitor is grounded, and the second end of the second capacitor is connected between the second end of the photoresistor and the first input end of the second follower and used for filtering the voltage output by the second end of the photoresistor.

10. A dc power supply system comprising at least one dc interface, the dc power supply system further comprising: the fault detection circuit of any one of claims 1 to 10, wherein the fault detection circuits are provided at each dc interface in a one-to-one correspondence.

11. The dc device of claim 10, wherein the dc power supply system is a photovoltaic power supply system.

12. A dc device comprising a load and further comprising the dc power supply system of claim 10.

13. The direct current device according to claim 12, characterized in that the direct current device is a photovoltaic air conditioner.

14. A method of fault detection, the method comprising:

acquiring an electric signal output by a detection module; the detection module is arranged at a direct current interface of the direct current power supply system and is connected with the signal processor;

and judging the fault type at the interface according to the electric signal.

15. The fault detection method of claim 14, wherein the electrical signal comprises:

a first electrical signal and a second electrical signal; wherein the first electrical signal is generated as a function of temperature at an interface between the photovoltaic string and the DC/DC converter; the second electrical signal is generated as a function of the intensity of illumination at the interface between the photovoltaic string and the DC/DC converter.

16. The method according to claim 15, wherein before determining the type of the fault at the interface according to the electrical signal, the method further comprises:

judging whether a voltage value carried by a first electric signal output by the detection module is smaller than or equal to a first reference voltage and a voltage value carried by a second electric signal output by the detection module is smaller than or equal to a second reference voltage;

if yes, judging that no fault occurs at the interface;

if not, judging that the interface has a fault, and triggering to judge the fault type at the interface according to the electric signal.

17. The method of claim 15, wherein determining the type of fault at the interface from the electrical signal comprises:

if the voltage value carried by the first electric signal is less than or equal to a first reference voltage and the voltage value carried by the second electric signal is greater than a second reference voltage, judging that the fault type is the damage of the protective layer;

if the voltage value carried by the first electric signal is greater than a first reference voltage and the voltage value carried by the second electric signal is less than or equal to a second reference voltage, judging that the fault type is the reverse connection of the terminal;

and if the voltage value carried by the first electric signal is greater than a first reference voltage and the voltage value carried by the second electric signal is greater than a second reference voltage, judging that the fault type is arc discharge at the interface.

18. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out the method according to any one of claims 14 to 17.

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