Patent Description:
A photovoltaic power generation system is a power generation system of converting solar energy into electric energy. The photovoltaic power generation system is used as a power source in more sites due to advantages that the photovoltaic power generation system has a long service life, is environmentally friendly, and not only can generate electricity independently but also can implement grid connection. Currently, the photovoltaic power generation system mainly includes a plurality of solar cell panels, a photovoltaic inverter, and the like. The solar cell panels are connected to the photovoltaic inverter by using cables and wiring terminals.

In the prior art, a direct current arc fault easily occurs in the photovoltaic power generation system due to aging of the cables or unreliable connections of the wiring terminals. To avoid an electrical fire caused by the direct current arc fault in the photovoltaic power generation system, an AFCI used to detect a direct current arc is disposed in the photovoltaic inverter in the photovoltaic power generation system. The AFCI includes a detection circuit used to detect whether a direct current arc exists in the photovoltaic power generation system, and a self-checking circuit used to test whether the detection circuit functions normally. A noise generation circuit is disposed in the self-checking circuit. The noise generation circuit may generate a noise signal having a spectrum characteristic the same as that of an arc noise signal, so that the self-checking circuit can test, by outputting the noise signal to the detection circuit, whether the detection circuit can detect the noise signal, and determine, based on this, whether the detection circuit functions normally.

However, regardless of whether the self-checking circuit of the AFCI is in a state of testing whether the detection circuit functions normally, the noise generation circuit in the self-checking circuit generates noise signals constantly. As a result, the noise signals affect a component in the working AFCI and a component in the photovoltaic inverter of the AFCI, and the AFCI and the photovoltaic inverter cannot work normally.

<CIT> discloses a method and apparatus for testing an AFCI device. In one embodiment, the method comprises the steps of providing an AFCI device to be tested and a load, wherein the AFCI device and the load form an electrical circuit, applying AC power to the AFCI device, generating a high frequency broadband noise signal, amplifying the high frequency broadband noise signal to provide an amplified high-frequency noise signal, modulating the amplified high frequency noise signal with a signal synchronized to the load current or load voltage to provide synchronized high frequency broadband noise bursts, coupling the synchronized high frequency broadband noise bursts into the electrical circuit to simulate series arcing signals, determining if the AFCI device opens the electrical circuit within a predetermined amount of time, indicating the AFCI device has passed the test if the AFCI opens the electrical circuit within the predetermined amount of time, and indicating the AFCI device has failed the test if the AFCI device fails to open the electrical circuit within the predetermined amount of time.

<CIT> discloses a combination AFCI/GFCI which includes a single test button which when pushed, tests both the arc fault and ground fault detection circuitry and the circuit interrupter. Closing the test button causes a simulated ground fault and enables a signal steering circuit. The steering circuit redirects the ground fault detector output to an arc fault simulator circuit which produces a simulated arcing pulses that are coupled, preferably by way of an extra winding, to an arc fault sensor transformer. The arc fault detector senses the arc fault simulator pulses coupled to the sensor transformer and, if everything is operating normally, triggers a switching device such as an SCR which activities a circuit interrupter. In this way, both the ground fault circuit interrupter and arc fault circuit interrupter functions are tested simultaneously, and the test is initiated by a single test button. When the circuit interrupter is not in the test mode, the steering circuitry is disabled and either a ground fault or an arc fault or both will independently activate the switching device and the circuit interrupter.

<CIT> discloses a method and apparatus for an integrated noise circuit for generating broadband gaussian noise with specified spectral flatness, matching impedance, and power output characteristics. A diode section operated in an avalanche breakdown mode is the primary noise source. A resistor network is selected to provide the specified matching impedance. Additional series resistor sections in the circuit are laser trimmed in production for specified spectral flatness and output power. The integrated noise circuit may be packaged for surface mounting on a printed circuit board.

<CIT> discloses a device having an avalanche diode which is arranged such that it is polarized under normal conditions of operation of the device in reverse direction. The avalanche diode is formed through a portion of transistor. The Zener voltage of emitter-base junction of transistor is set in the range from <NUM>-<NUM> V. The base of first transistor is connected to emitter of second transistor.

<CIT> relates to measurement and indication of partial discharges for testing and troubleshooting of arising insulation damage to high and medium voltage equipment, especially the calibration of such TE measuring arrangements.

The invention is defined in the claims. In the following, parts of the description and drawings referring to embodiments or aspects which are not covered by the claims are not presented as embodiments of the invention, but as examples useful for understanding the invention.

This application provides an AFCI, and a photovoltaic power generation system, to resolve a prior-art technical problem that regardless of whether a self-checking circuit of an AFCI is in a state of testing whether a detection circuit functions normally, a noise generation circuit in the self-checking circuit generates noise signals constantly, and as a result, the noise signals affect a component in the working AFCI and a component in a photovoltaic inverter of the AFCI, and consequently, the AFCI and the photovoltaic inverter cannot work normally.

According to a first aspect, this application provides an arc fault circuit interrupter as defined in independent claim <NUM>. According to the arc fault interrupter provided in the first aspect, after the noise generation circuit is disposed in a self-checking circuit of an AFCI in a photovoltaic power generation system, the power switch module of the noise generation circuit controls, only when receiving a self-checking instruction, the noise generator of the noise generation circuit to generate a noise signal having a spectrum characteristic the same as that of an arc noise signal. That is, the noise generation circuit in the self-checking circuit generates a noise signal only when the self-checking circuit tests a function of a detection circuit, that is, only after the photovoltaic power generation system is powered on and before an inverter works, and does not generate a noise signal in a non self-checking time, that is, when the AFCI and the photovoltaic inverter work normally. Therefore, according to the noise generation circuit provided in this application, no impact is imposed on a component in the AFCI in a working state or a component in a photovoltaic inverter of the AFCI, thereby ensuring normal working of the AFCI and the photovoltaic inverter, and improving working efficiency of the AFCI and the photovoltaic inverter.

According to the invention, the power switch module includes a power source, a first resistor, a second resistor, a first switch, and a P-channel metal oxide semiconductor PMOS transistor; and
a first terminal of the first resistor is connected to a first terminal of the first switch, a second terminal of the first switch is grounded, a third terminal of the first switch is connected to both a first terminal of the second resistor and a gate of the PMOS transistor, a second terminal of the second resistor and a source of the PMOS transistor both are connected to the power source, and a drain of the PMOS transistor is connected to the noise generator.

According to the noise generation circuit provided in this possible implementation, after the first resistor of the power switch module receives the self-checking instruction, the first switch of the power switch module may be connected by using a voltage obtained after the first resistor performs voltage division, to reduce a voltage on the gate of the PMOS transistor, so that the voltage on the gate of the PMOS transistor is less than a voltage on the source of the PMOS transistor, and further, the source and the drain of the PMOS transistor are connected. In this manner, the power source VCC of the power switch module can supply power, by using the source of the PMOS transistor, to the noise generator connected to the drain of the PMOS transistor, so that the noise generator can generate a noise signal, and the self-checking circuit can test, by using the noise signal, whether the detection circuit functions normally, thereby implementing a self-checking function of the self-checking circuit.

Optionally, in a possible implementation of the first aspect, the power switch module further includes a third resistor; and
a first terminal of the third resistor is connected to both the first terminal of the first resistor and the first terminal of the first switch, and a second terminal of the third resistor is grounded.

According to the noise generation circuit provided in this possible implementation, the third resistor can release a charge accumulated when the first switch stops working, thereby improving stability of the first switch.

Optionally, in a possible implementation of the first aspect, the power switch module further includes a fourth resistor; and
a first terminal of the fourth resistor is connected to the third terminal of the first switch, and a second terminal of the fourth resistor is connected to both the first terminal of the second resistor and the gate of the PMOS transistor.

According to the noise generation circuit provided in this possible implementation, the fourth resistor and the second resistor can share a voltage of the VCC together, so that the voltage on the gate of the PMOS transistor is equal to a voltage on the second terminal of the fourth resistor, thereby reducing the voltage on the gate of the PMOS transistor, and further connecting the PMOS transistor. Therefore, the power switch module can supply power to the noise generator by using the PMOS transistor, so that the noise generator generates a noise signal, and the self-checking circuit can test, by using the noise signal, whether the detection circuit functions normally, thereby implementing the self-checking function of the self-checking circuit.

Optionally, in a possible implementation of the first aspect, the first switch is a first NPN triode; and.

In a first alternative of the first aspect, the noise generator is a Zener diode; and a first terminal of the Zener diode is connected to both the drain of the PMOS transistor and a first terminal of the capacitor, and a second terminal of the Zener diode is grounded.

According to the noise generation circuit provided in this possible implementation, because the Zener diode may generate, in a normal working state, a shot noise signal having a spectrum characteristic the same as that of an arc noise signal, when the Zener diode is used as the noise generator of the noise generation circuit, the service life of the noise generator can be lengthened, and further, reliability of the noise generation circuit can be improved.

Optionally, in a possible implementation of the first aspect, the power switch module further includes a fifth resistor used for current limiting; and
the first terminal of the Zener diode is connected to the drain of the PMOS transistor by using the fifth resistor.

According to the noise generation circuit provided in this possible implementation, the fifth resistor is disposed between the drain of the PMOS transistor and the Zener diode, so that a current passing through the Zener diode can be limited. Therefore, the Zener diode can be protected from being damaged by an excessively large current, thereby lengthening the service life of the Zener diode, and further, improving the reliability of the noise generation circuit.

In a second alternative of the first aspect, the noise generator is a second NPN transistor ; and
an emitter of the second NPN triode is connected to the drain of the PMOS transistor, a base of the second NPN triode is connected to a first terminal of the capacitor, and a collector of the second NPN triode is not connected.

Optionally, in a possible implementation of the first aspect, the power switch module further includes a fifth resistor used for current limiting; and
the emitter of the second NPN triode is connected to the drain of the PMOS transistor by using the fifth resistor.

According to the noise generation circuit provided in this possible implementation, the fifth resistor is disposed between the drain of the PMOS transistor and the second NPN triode, so that a current passing through the second NPN triode can be limited. Therefore, the second NPN triode can be protected from being damaged by an excessively large current, thereby lengthening the service life of the second NPN triode, and further, improving the reliability of the noise generation circuit.

Optionally, in a possible implementation of the first aspect, the noise generation circuit further includes a sixth resistor and an operational amplifier; and
a first terminal of the sixth resistor is grounded, a second terminal of the sixth resistor is connected to both a second terminal of the capacitor and a non-inverting input terminal of the operational amplifier, and an output terminal of the operational amplifier is connected to an inverting input terminal of the operational amplifier.

According to the noise generation circuit provided in this possible implementation, by using the sixth resistor connected to the capacitor, the sixth resistor can release a charge accumulated when the capacitor stops working. In addition, by using the operational amplifier connected to the capacitor, the operational amplifier can isolate the capacitor from impedance in a filter amplifier circuit in the self-checking circuit, so that the capacitor can work in a normal state, and the capacitor can effectively remove the direct current component in the noise signal generated by the noise generator, thereby improving working efficiency of the capacitor.

According to an unclaimed example,
this application provides a self-checking circuit. The self-checking circuit may include any noise generation circuit described above.

For a beneficial effect of the self-checking circuit provided in the unclaimed example, refer to the beneficial effect of the first aspect and any possible implementation of the first aspect, and details are not described herein again.

According to a further aspect, this application provides a photovoltaic power generation system. The photovoltaic power generation system may include the AFCI described above.

For a beneficial effect of the photovoltaic power generation system provided in the fourth aspect, refer to the beneficial effect of the first aspect and any possible implementation of the first aspect, and details are not described herein again.

According to the AFCI, and the photovoltaic power generation system that are provided in this application, after the noise generation circuit is disposed in the self-checking circuit of the AFCI in the photovoltaic power generation system, the power switch module of the noise generation circuit controls, only when receiving a self-checking instruction, the noise generator of the noise generation circuit to generate a noise signal having a spectrum characteristic the same as that of an arc noise signal. That is, the noise generation circuit in the self-checking circuit generates a noise signal only when the self-checking circuit tests a function of the detection circuit, that is, only after the photovoltaic power generation system is powered on and before an inverter works, and does not generate a noise signal in a non self-checking time, that is, when the AFCI and the photovoltaic inverter work normally. Therefore, according to the noise generation circuit provided in this application, no impact is imposed on the component in the AFCI in a working state or the component in the photovoltaic inverter of the AFCI, thereby ensuring normal working of the AFCI and the photovoltaic inverter, and improving the working efficiency of the AFCI and the photovoltaic inverter.

Using an AFCI in a photovoltaic power generation system as an example, in the prior art, the AFCI is disposed in a photovoltaic inverter in the photovoltaic power generation system, and the AFCI may include a detection circuit used to detect whether a direct current arc exists in the photovoltaic power generation system, and a self-checking circuit. The self-checking circuit may test, after the photovoltaic power generation system is powered on and before the photovoltaic inverter works, whether the detection circuit functions normally. A noise generation circuit in the self-checking circuit is connected to the detection circuit by using a switch module. The switch module is configured to connect the noise generation circuit to the detection circuit when the self-checking circuit tests a function of the detection circuit, so that the noise generation circuit in the self-checking circuit can output a noise signal having a spectrum characteristic the same as that of an arc noise signal to the detection circuit, and further, the self-checking circuit can determine, by testing whether the detection circuit can detect the noise signal, whether the detection circuit functions normally. However, regardless of whether the switch module is in a connected state, that is, regardless of whether the self-checking circuit tests a function of the detection circuit, the noise generation circuit in the self-checking circuit generates noise signals constantly. As a result, when the AFCI and the photovoltaic inverter of the AFCI work, the noise signals generated by the noise generation circuit in the self-checking circuit affect a component in the working AFCI and a component in the photovoltaic inverter of the AFCI, and the AFCI and the photovoltaic inverter cannot work normally.

According to a noise generation circuit provided in this application, after the noise generation circuit is disposed in a self-checking circuit of an AFCI in a photovoltaic power generation system, a power switch module of the noise generation circuit controls, only when receiving a self-checking instruction, a noise generator of the noise generation circuit to generate a noise signal having a spectrum characteristic the same as that of an arc noise signal. That is, the noise generation circuit in the self-checking circuit generates a noise signal only when the self-checking circuit tests a function of a detection circuit, that is, only after the photovoltaic power generation system is powered on and before an inverter works, and does not generate a noise signal in a non self-checking time, that is, when the AFCI and the photovoltaic inverter work normally. Therefore, according to the noise generation circuit provided in this application, no impact is imposed on a component in the AFCI in a working state or a component in the photovoltaic inverter of the AFCI, thereby ensuring normal working of the AFCI and the photovoltaic inverter. Therefore, the noise generation circuit provided in this application is intended to resolve a prior-art technical problem that regardless of whether a self-checking circuit of an AFCI is in a state of testing whether a detection circuit functions normally, a noise generation circuit in the self-checking circuit generates noise signals constantly, and as a result, the noise signals affect a component in a working AFCI and a component in a photovoltaic inverter of the AFCI, and the AFCI and the photovoltaic inverter cannot work normally.

<FIG> is a schematic structural diagram of modules of a noise generation circuit according to this application. As shown in <FIG>, the noise generation circuit may include a power switch module <NUM>, a noise generator <NUM>, and a capacitor <NUM>. The noise generator <NUM> is connected to both the power switch module <NUM> and the capacitor <NUM>.

The power switch module <NUM> is configured to control, according to a self-checking instruction, whether the noise generator <NUM> generates a noise signal.

The capacitor <NUM> is configured to filter out a direct current component in the noise signal when the noise generator <NUM> generates the noise signal.

Specifically, the noise generation circuit may be disposed in a self-checking circuit of an AFCI in an inverter of a photovoltaic power generation system, and is configured to output a noise signal having a spectrum characteristic the same as that of an arc noise signal to a detection circuit when the self-checking circuit of the AFCI tests a function of the detection circuit.

The power switch module <NUM> included in the noise generation circuit may be any module having a receiving function, a connection function, a disconnection function, a power supply function, or the like. In this application, the power switch module <NUM> may receive the self-checking instruction, and supply power to the noise generator <NUM> when receiving the self-checking instruction, so that the noise generator <NUM> can generate a noise signal having a spectrum characteristic the same as that of an arc noise signal. In addition, the power switch module <NUM> stops supplying power to the noise generator <NUM> when the power switch module <NUM> does not receive the self-checking instruction, so that the noise generator <NUM> does not generate the noise signal, to avoid impact imposed by the noise signal on working of a component in the AFCI and a component in the photovoltaic inverter of the AFCI, thereby ensuring normal working of the AFCI and the photovoltaic inverter of the AFCI. The self-checking instruction may be any high-level signal whose voltage is greater than a working voltage of the power switch module <NUM>, for example, a <NUM> V high-level signal, or a <NUM> V high-level signal. This may be specifically set according to the working voltage of the power switch module <NUM>. During specific implementation, the self-checking instruction may be a self-checking instruction sent by a processor of the self-checking circuit of the AFCI, or a self-checking instruction generated when a maintenance person manually triggers a hardware switch (for example, a button) connected to the power switch module <NUM>, or the like.

The noise generator <NUM> included in the noise generation circuit may be any component that can generate an analog arc noise signal; according to the invention, the noise generator is a Zener diode or a NPN transistor. In this application, the noise generator <NUM> may generate, when the power switch module <NUM> receives the self-checking instruction, that is, when the power switch module <NUM> supplies power to the noise generator, a noise signal having a spectrum characteristic the same as that of an arc noise signal. The capacitor included in the noise generation circuit may be any capacitor having a function of coupling alternating current signals. In this application, when the noise generator <NUM> generates the noise signal, the capacitor may filter out the direct current component in the noise signal, so that the noise signal approaches an actual arc noise signal.

The following describes an operating principle of the noise generation circuit provided in this application by using an example in which the noise generation circuit is disposed in a self-checking circuit of an existing AFCI. Specifically:
<FIG> shows a self-checking circuit of an AFCI according to this application. As shown in <FIG>, the self-checking circuit of the AFCI may include a noise generation circuit, a first filter amplifier circuit, a button switch connected to the noise generation circuit, and a current transformer CT, a sampling resistor, a second filter amplifier circuit, a processor, and an LED lamp that are of a detection circuit. The current CT may include a coil <NUM> and a coil <NUM>. When the noise generation circuit provided in this application is disposed in the self-checking circuit of the AFCI shown in <FIG>, a self-checking method of the AFCI may specifically include the following steps:.

According to the noise generation circuit provided in this application, after the noise generation circuit is disposed in the self-checking circuit of the AFCI in the photovoltaic power generation system, the power switch module of the noise generation circuit controls, only when receiving a self-checking instruction, the noise generator of the noise generation circuit to generate a noise signal having a spectrum characteristic the same as that of an arc noise signal. That is, the noise generation circuit in the self-checking circuit generates a noise signal only when the self-checking circuit tests a function of the detection circuit, that is, only after the photovoltaic power generation system is powered on and before an inverter works, and does not generate a noise signal in a non self-checking time, that is, when the AFCI and the photovoltaic inverter work normally. Therefore, according to the noise generation circuit provided in this application, no impact is imposed on a component in the AFCI in a working state or a component in the photovoltaic inverter of the AFCI, thereby ensuring normal working of the AFCI and the photovoltaic inverter, and improving working efficiency of the AFCI and the photovoltaic inverter.

<FIG> is a circuit diagram of the noise generation circuit according to this application. As shown in <FIG>, the power switch module <NUM> of the noise generation circuit may include a power source VCC, a first resistor R1, a second resistor R2, a first switch <NUM>, and a PMOS transistor Q1.

A first terminal of the first resistor R1 is connected to a first terminal of the first switch <NUM>, a second terminal of the first switch <NUM> is grounded, a third terminal of the first switch <NUM> is connected to both a first terminal of the second resistor R2 and a gate of Q1, a second terminal of the second resistor R2 and a source of Q1 both are connected to the power source, and a drain of Q1 is connected to the noise generator.

Specifically, the first resistor R1 may be a voltage division resistor, and the first resistor R1 may be connected to an output terminal of the processor or a button switch by using the second terminal of the first resistor, so that the first resistor R1 can receive a self-checking instruction, and when receiving a self-checking instruction in a form of a high-level signal, perform voltage division for the high-level signal, to reduce a voltage of the high-level signal. Therefore, the voltage approaches a working voltage of the first switch <NUM>, to connect the first switch <NUM>. The connected first switch <NUM> may cause the gate of Q1 to be grounded, to reduce a voltage on the gate of Q1, so that the voltage on the gate of Q1 is less than a voltage on the source of Q1, and further, the source and the drain of Q1 can be connected. In this manner, after the power switch module <NUM> receives the self-checking instruction, the power source VCC of the power switch module <NUM> can supply power, by using the source of Q1, to the noise generator <NUM> connected to the drain of Q1, so that the noise generator <NUM> can generate a noise signal having a spectrum characteristic the same as that of an arc noise signal, and the self-checking circuit can test, by using the noise signal, whether the detection circuit functions normally, thereby implementing a self-checking function of the self-checking circuit.

Continuing to refer to <FIG>, optionally, in another implementation of this application, the power switch module <NUM> may further include a third resistor R3 used for voltage division. A first terminal of the third resistor R3 is connected to both the first terminal of the first resistor R1 and the first terminal of the first switch <NUM>, and a second terminal of the third resistor R3 is grounded, so that the third resistor R3 can release a charge accumulated when the first switch <NUM> stops working, thereby improving stability of the first switch <NUM>.

Continuing to refer to <FIG>, optionally, in another implementation of this application, the power switch module <NUM> may further include a fourth resistor R4 used for voltage division. A first terminal of the fourth resistor R4 is connected to the third terminal of the first switch <NUM>, and a second terminal of the fourth resistor R4 is connected to both the first terminal of the second resistor R2 and the gate of Q1, so that the fourth resistor R4 and R2 can share a voltage of the power source VCC together. Therefore, the voltage on the gate of Q1 is equal to a voltage on the second terminal of R4, thereby reducing the voltage on the gate of Q1, and further connecting the PMOS transistor. Therefore, the power switch module <NUM> can supply power to the noise generator by using the PMOS transistor, so that the noise generator generates a noise signal, and the self-checking circuit can test, by using the noise signal, whether the detection circuit functions normally, thereby implementing a self-checking function of the self-checking circuit.

Continuing to refer to <FIG>, as shown in <FIG>, the first switch <NUM> in the power switch module <NUM> may be any switch that can be connected when a working voltage is satisfied, for example, an NPN triode, or an NMOS transistor. Optionally, when the first switch <NUM> is a first NPN triode T1, a base B of T1 is the first terminal of the first switch <NUM>, an emitter E of T1 is the second terminal of the first switch <NUM>, and a collector C of T1 is the third terminal of the first switch <NUM>. Optionally, when the first switch <NUM> is an NMOS transistor, a gate of the NMOS transistor is the first terminal of the first switch <NUM>, a source of the NMOS transistor is the second terminal of the first switch <NUM>, and a drain of the NMOS transistor is the third terminal of the first switch <NUM>. The power switch module <NUM> shown in <FIG> is a power switch module whose first switch <NUM> is, for example, T1.

As described in the foregoing embodiment, the noise generator <NUM> included in the noise generation circuit may be any component that can generate an analog arc noise signal, for example, an NPN triode, or a Zener diode. Optionally, when the noise generator <NUM> is a second NPN triode, an emitter E of the second NPN triode may be connected to the drain of the PMOS transistor, a base B of the second NPN triode may be connected to a first terminal of a capacitor C1, and a collector C of the second NPN triode may be not connected, so that when the power switch module <NUM> supplies power to the second NPN triode, the second NPN triode may work in a reverse breakdown state, to generate a white noise signal having a spectrum characteristic the same as that of an arc noise signal. Optionally, when the noise generator <NUM> is a Zener diode ZD1, a first terminal of ZD1 is connected to both the drain of the PMOS transistor and a first terminal of a capacitor C1, and a second terminal of ZD1 is grounded, so that when the power switch module <NUM> supplies power to ZD1, that is, when ZD1 can work normally, ZD1 can generate a shot noise signal having a spectrum characteristic the same as that of an arc noise signal. Because ZD1 can generate, in a normal working state, a noise signal having a spectrum characteristic the same as that of an arc noise signal, when ZD1 is used as the noise generator <NUM> of the noise generation circuit, the service life of the noise generator <NUM> can be lengthened, and further reliability of the noise generation circuit can be improved. <FIG> shows the noise generation circuit <NUM> using the Zener diode ZD1 as the noise generator <NUM>.

Continuing to refer to <FIG>, optionally, the power switch module <NUM> may further include a fifth resistor R5 used for current limiting. R5 may be disposed between the drain of Q1 and the noise generator <NUM>, and is configured to limit a current passing through the noise generator <NUM>, so that the noise generator <NUM> can be protected from being damaged by an excessively large current, thereby lengthening the service life of the noise generator <NUM>, and improving reliability of the noise generation circuit. Optionally, if the noise generator <NUM> is ZD1, when the power switch module <NUM> includes R5, the first terminal of ZD1 may be connected to the drain of the PMOS transistor by using R5. Optionally, if the noise generator <NUM> is the second NPN triode, when the power switch module <NUM> includes R5, the emitter E of the second NPN triode may be connected to the drain of the PMOS transistor by using R5. Continuing to refer to <FIG>, optionally, the noise generation circuit may further include a sixth resistor R6 and an operational amplifier U1. A first terminal of R6 is grounded, a second terminal of R6 is connected to both a second terminal of C1 and a non-inverting input terminal of U1, an output terminal of U1 is connected to an inverting input terminal of U1, so that R6 can release a charge accumulated when the capacitor C1 stops working, and U1 can isolate the capacitor from impedance in a filter amplifier circuit in the self-checking circuit. Therefore, C1 can work in a normal state, and C1 can effectively remove a direct current component in an analog arc noise signal generated by the noise generator, thereby improving working efficiency of C1.

It should be noted that although the foregoing embodiment describes, by using an example in which the noise generation circuit is disposed in the AFCI in the inverter in the photovoltaic power generation system, the noise generation circuit provided in this application, a person skilled in the art may understand that the noise generation circuit may be alternatively disposed in an AFCI in another device in the photovoltaic power generation system, or may be disposed in an AFCI in any other device or system (for example, a high-voltage direct current power source) in which an AFCI is disposed, so that impact imposed on an AFCI and a device of the AFCI because the noise generation circuit generates an arc noise signal in a non self-checking time can be avoided, to ensure normal working of the AFCI and the device of the AFCI.

An unclaimed example of this application further provides a self-checking circuit. The self-checking circuit may include the noise generation circuit in any one of the foregoing embodiments. Implementation principles and technical effects thereof are similar, and details are not described herein again.

Still another aspect of this application further provides an AFCI. The AFCI may include the foregoing self-checking circuit, and the self-checking circuit may include the noise generation circuit in any one of the foregoing embodiments. Implementation principles and technical effects thereof are similar, and details are not described herein again.

Claim 1:
An arc fault circuit interrupter AFCI, comprising a noise generation circuit, which noise generation circuit comprises a power switch module (<NUM>), a noise generator (<NUM>), and a capacitor (<NUM>), wherein the noise generator (<NUM>) is connected to both the power switch module (<NUM>) and the capacitor (<NUM>), wherein the power switch module (<NUM>) comprises a power source, a first resistor, a second resistor, a first switch, and a P-channel metal oxide semiconductor, PMOS transistor;
the power switch module (<NUM>) is configured to control, according to a self-checking instruction, whether the noise generator (<NUM>) generates a noise signal; and
the capacitor (<NUM>) is configured to filter out a direct current component in the noise signal when the noise generator (<NUM>) generates the noise signal;
the noise generator (<NUM>) is a Zener diode; and a first terminal of the Zener diode is connected to both the drain of the PMOS transistor and a first terminal of the capacitor (<NUM>), and a second terminal of the Zener diode is grounded; or
the noise generator (<NUM>) is a second NPN transistor; and an emitter of the second NPN transistor is connected to the drain of the PMOS transistor, a base of the second NPN transistor is connected to a first terminal of the capacitor (<NUM>), and a collector of the second NPN transistor is not connected,; and
A first terminal of the first resistor is connected to a first terminal of the first switch, a second terminal of the first switch is grounded, a third terminal of the first switch is connected to both a first terminal of the second resistor and a gate of the PMOS transistor, a second terminal of the second resistor and a source of the PMOS transistor both are connected to the power source, and a drain of the PMOS transistor is connected to the noise generator (<NUM>).