Power converter and control method thereof

Abstract

The embodiment of the invention discloses a power converter and a control method thereof, relates to the technical field of energy, and solves the problem of how to accurately judge whether an arc fault breaker works normally or not. Specifically, in the power converter, a controller is used for outputting a pulse signal. The noise signal conditioning circuit is used for receiving the pulse signal and outputting a noise signal according to the pulse signal. The current transformer is used for receiving and sampling the noise signal so as to output a sampling signal. The sampling signal conditioning circuit is used for receiving the sampling signal and outputting a conditioning signal according to the sampling signal. The controller is further used for controlling the power conversion circuit to start working under the condition that the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is smaller than or equal to a frequency threshold value and the gain of the conditioning signal is larger than or equal to a gain threshold value corresponding to the frequency of the pulse signal.

Description

Technical Field

[0001] The present application relates to the field of energy technology, and in particular to a power converter and a control method thereof. Background Art

[0002] The photovoltaic power generation system may include a photovoltaic inverter, a micro string inverter is a photovoltaic inverter, the input of the micro string inverter is used to connect to the photovoltaic array, and the output of the micro string inverter is used to connect to the load or the power grid, or the photovoltaic power generation system may also include an optimizer, the input of the optimizer is used to connect to the photovoltaic array, and the output of the optimizer is used to connect to the input of the photovoltaic inverter.

[0003] Photovoltaic power generation systems have a long service life. Due to cable aging or unreliable terminal connection, DC arc faults are prone to occur, causing electrical fires. To avoid the above problems, an arc-fault circuit-interrupter (AFCI) can be set in the photovoltaic inverter or optimizer. The arc-fault circuit-interrupter can also be called an arc-fault circuit breaker.

[0004] However, how to judge whether the arc fault breaker is working normally and control the power conversion circuit in the photovoltaic inverter or optimizer to start working when the arc fault breaker is working normally to improve the reliability and safety of the photovoltaic inverter or optimizer has become an urgent problem to be solved. Summary of the invention

[0005] The embodiments of the present application provide a power converter and a control method thereof, which solve the problem of how to accurately determine whether an arc fault breaker operates normally.

[0006] In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

[0007] In a first aspect of an embodiment of the present application, a power converter is provided, which includes a current transformer, a power conversion circuit, a noise signal conditioning circuit, a sampling signal conditioning circuit and a controller, wherein the noise signal conditioning circuit includes a first resistor and a capacitor connected in series. The current transformer is used to connect between a photovoltaic array and a power conversion circuit, the current transformer is used to detect the current output by the photovoltaic array, and the power conversion circuit is used to perform power conversion on the direct current output by the photovoltaic array. The current transformer and the sampling signal conditioning circuit are used for direct current arc detection. The controller is used to output a pulse signal. The noise signal conditioning circuit is used to receive a pulse signal and output a noise signal according to the pulse signal. The current transformer is used to receive a noise signal and sample it to output a sampling signal. The sampling signal conditioning circuit is used to receive a sampling signal and output a conditioned signal according to the sampling signal. The controller is also used to control the power conversion circuit to start working when the absolute value of the difference between the frequency of the conditioned signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioned signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal.

[0008] Based on this solution, the controller controls the power conversion circuit to start working when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal, so that the power conversion circuit can be controlled to start working when the arc fault breaker in the power converter is more accurately determined to be working normally, which can improve the reliability and safety of the power converter. At the same time, the noise signal conditioning circuit includes a first resistor and a capacitor connected in series, and the circuit topology of the noise signal conditioning circuit is simpler, which can reduce the cost of the power converter.

[0009] In combination with the first aspect, in a possible implementation, the controller is also used to control the power converter to shut down when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than a frequency threshold, or the gain of the conditioning signal is less than a gain threshold corresponding to the frequency of the pulse signal.

[0010] Based on this solution, when the absolute value of the difference between the frequency of the conditioned signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioned signal is less than the gain threshold corresponding to the frequency of the pulse signal, the controller determines that the arc fault breaker in the power converter is not operating normally, and issues an alarm to indicate that the arc fault breaker is not operating normally, and controls the power converter to shut down, thereby improving the reliability and safety of the power converter.

[0011] In combination with the first aspect, in a possible implementation method, the controller is specifically used to output a pulse signal whose frequency changes according to a fixed step size during a DC arc detection. The frequency change according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

[0012] Based on this scheme, compared with the controller outputting a pulse signal of each frequency in sequence in a DC arc detection, the controller outputs a pulse signal whose frequency changes according to a fixed step size in a DC arc detection. The controller needs to compare fewer conditioned signals and pulse signals, thereby being able to more quickly determine whether the arc fault interrupter in the power converter is working normally, thereby improving the startup efficiency of the power converter.

[0013] In combination with the first aspect, in a possible implementation manner, the fixed step size includes 5 KHz, 10 KHz, 15 KHz or 20 KHz.

[0014] In combination with the first aspect, in a possible implementation manner, the frequency range threshold of the pulse signal is greater than or equal to 20 KHz and less than or equal to 60 KHz.

[0015] Based on this solution, the frequency range threshold of the pulse signal is greater than or equal to 20KHz and less than or equal to 60KHz. By reducing the frequency range threshold of the controller output pulse signal, the controller needs to compare fewer conditioned signals and pulse signals, thereby being able to more quickly determine whether the arc fault interrupter in the power converter is working properly, thereby improving the startup efficiency of the power converter.

[0016] In combination with the first aspect, in a possible implementation, the power converter further includes a drive circuit, the drive circuit is arranged between the controller and the noise signal conditioning circuit, and the sampling signal conditioning circuit is a second-order bandpass filter.

[0017] Based on this solution, by setting a driving circuit between the controller and the noise signal conditioning circuit, additional driving capability can be provided when the driving capability of the controller is insufficient, thereby avoiding the controller being unable to detect whether the arc fault breaker is working normally, and improving the reliability of the power converter.

[0018] In combination with the first aspect, in a possible implementation, the current transformer includes a second resistor, and a first coil, a second coil, a third coil, and a fourth coil that are magnetically coupled to each other. One end of the first coil is used to connect to the positive pole of the photovoltaic array, and the other end of the first coil is connected to the positive input end of the power conversion circuit. One end of the second coil is used to connect to the negative pole of the photovoltaic array, and the other end of the second coil is connected to the negative input end of the power conversion circuit. One end of the third coil is connected to the output end of the noise signal conditioning circuit, the other end of the third coil and one end of the fourth coil are connected to the ground end, the other end of the fourth coil is connected to the input end of the sampling signal conditioning circuit, and the second resistor is connected in parallel with the fourth coil.

[0019] In combination with the first aspect, in one possible implementation, the power conversion circuit is a DCDC power conversion circuit, and the output of the power converter is used to be connected to the input of the inverter, or the output of the power converter is used to be connected in series with the output of at least one power converter and then connected to the input of the inverter, and the output of the inverter is used to be connected to a grid or a load.

[0020] In combination with the first aspect, in a possible implementation, the power conversion circuit is a DCAC power conversion circuit, and the output of the power conversion circuit is used to connect to a power grid or a load. The controller is specifically used to control the power conversion circuit to establish a connection with the power grid or the load when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal. When the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal, the power conversion circuit is controlled to disconnect from the power grid or the load.

[0021] According to a second aspect of an embodiment of the present application, a control method for a power converter is provided, which is applied to a power converter, and the method includes: generating a pulse signal. Generating a noise signal according to the pulse signal. Generating a sampling signal according to the noise signal. Generating a conditioning signal according to the sampling signal. When the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to a frequency threshold, and the gain of the conditioning signal is greater than or equal to a gain threshold corresponding to the frequency of the pulse signal, controlling a power conversion circuit in the power converter to start working.

[0022] In combination with the second aspect, in a possible implementation, the method also includes: controlling the power converter to shut down when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than a frequency threshold, or when the gain of the conditioning signal is less than a gain threshold corresponding to the frequency of the pulse signal.

[0023] In combination with the second aspect, in a possible implementation, the above-mentioned generation of a pulse signal includes: in a DC arc detection, generating a pulse signal whose frequency changes according to a fixed step size, the frequency changing according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

[0024] In combination with the second aspect, in a possible implementation manner, the fixed step size includes 5 KHz, 10 KHz, 15 KHz or 20 KHz.

[0025] In combination with the second aspect, in a possible implementation manner, the frequency range threshold of the pulse signal is greater than or equal to 20 KHz and less than or equal to 60 KHz.

[0026] According to a third aspect of an embodiment of the present application, a photovoltaic power generation system is provided, which includes multiple optimizers and photovoltaic inverters. Each optimizer can be used to connect to a photovoltaic array. The output ends of the multiple optimizers are connected in series and then connected to the input end of the photovoltaic inverter. The output end of the photovoltaic inverter is used to connect to a power grid or a load. The optimizer can also be called a power converter, which is a power converter as described in the above-mentioned first aspect or any possible implementation of the first aspect.

[0027] According to a fourth aspect of an embodiment of the present application, a photovoltaic power generation system is provided, which includes a plurality of micro string inverters, each of which can be used to connect to a photovoltaic array, each photovoltaic array includes at least one photovoltaic module, and the output ends of the plurality of micro string inverters are connected in parallel through power lines, which are connected to a power grid or a load. The micro string inverter can be called a power converter, which is a power converter as described in the first aspect or any possible implementation of the first aspect.

[0028] The description of the second to fourth aspects in this application can refer to the detailed description of the first aspect; and the beneficial effects of the second to fourth aspects can refer to the analysis of the beneficial effects of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a circuit topology of a photovoltaic inverter provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of a circuit topology of a photovoltaic power generation system provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of another circuit topology of a photovoltaic power generation system provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of a circuit topology of a power converter provided in an embodiment of the present application;

[0033] Figure 5 A schematic diagram of another circuit topology of a power converter provided in an embodiment of the present application;

[0034] Figure 6 A Bode diagram provided for an embodiment of the present application;

[0035] Figure 7 A pulse signal frequency adjustment schematic diagram provided in an embodiment of the present application;

[0036] Figure 8 A schematic flow chart of a method for controlling a power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The following will discuss the making and use of each embodiment in detail. However, it should be understood that many applicable inventive concepts provided by this application can be implemented in a variety of specific environments. The specific embodiments discussed are only used to illustrate the specific ways to implement and use this description and this technology, and do not limit the scope of this application.

[0038] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0039] Various circuits or other components may be described or referred to as being "configured to" perform one or more tasks. In this case, "configured to" is used to imply structure by indicating that the circuit / component includes structure (e.g., circuitry) that performs the one or more tasks during operation. Thus, even when the specified circuit / component is not currently operational (e.g., not turned on), the circuit / component may be referred to as being configured to perform the task. Circuits / components used with the phrase "configured to" include hardware, such as circuits that perform an operation, etc.

[0040] The technical scheme in the embodiment of the present application will be described below in conjunction with the accompanying drawings in the embodiment of the present application. In the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or its similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c or a, b and c, where a, b and c can be single or multiple. In addition, in the embodiment of the present application, the words "first", "second" and the like do not limit the quantity and order.

[0041] In this application, the words "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the related concepts in a concrete way.

[0042] Before introducing the embodiments of the present application, the technical terms and background technologies involved in the present application are first introduced.

[0043] Current transformer (CT): A current transformer is an instrument that converts a large primary current into a small secondary current for measurement based on the principle of electromagnetic induction. The current transformer consists of a closed iron core and a winding, which can also be called a coil.

[0044] Photovoltaic power generation systems have a long service life. Faults such as cable aging or unreliable terminal connections can easily cause DC arc faults and electrical fires. To avoid the above problems, an arc fault breaker can be set in the photovoltaic inverter or optimizer. For example, taking the photovoltaic inverter as an example, Figure 1 The schematic diagram of the circuit topology of a photovoltaic inverter 100 provided in an embodiment of the present application is shown. The photovoltaic inverter 100 includes a direct current to alternating current (DCAC) power conversion circuit 110, a controller 120, a current transformer 130, a noise generating circuit 140 and a filter amplifier circuit 150. The circuit composed of the current transformer 130, the noise generating circuit 140 and the filter amplifier circuit 150 can be called an arc fault breaker.

[0045] The current transformer 130 is used to be connected between the photovoltaic array 200 and the DCAC power conversion circuit 110, and the output of the DCAC power conversion circuit 110 is used to be connected to the power grid or the load 300. The current transformer 130 is used to detect the current output by the photovoltaic array 200, and the DCAC power conversion circuit 110 is used to convert the direct current output by the photovoltaic array 200 into alternating current and transmit it to the power grid or the load 300. The current transformer 130 and the filter amplifier circuit 150 are used for DC arc detection.

[0046] Specifically, refer to Figure 1 The current transformer 130 includes a first resistor R1, and a first coil L1, a second coil L2, a third coil L3 and a fourth coil L4 that are magnetically coupled to each other. The first coil L1 is connected between the positive pole of the photovoltaic array 200 and the positive input terminal of the DCAC power conversion circuit 110, and the second coil L2 is connected between the negative pole of the photovoltaic array 200 and the negative input terminal of the DCAC power conversion circuit 110. One end of the third coil L3 is connected to the output terminal of the noise generating circuit 140, and the input terminal of the noise generating circuit 140 is connected to the output terminal of the controller 120. The other end of the third coil L3 and one end of the fourth coil L4 are connected to the ground terminal (ground, G), and the other end of the fourth coil L4 is connected to the input terminal of the filter amplifier circuit 150. The output terminal of the filter amplifier circuit 150 is connected to the input terminal of the controller 120. The first resistor R1 is connected in parallel with the fourth coil L4.

[0047] Among them, the circuit composed of the third coil L3 and the noise generating circuit 140 can be called a self-test circuit, and the circuit composed of the fourth coil L4, the first resistor R1 and the filter amplifier circuit 150 can be called a detection circuit. The self-test circuit is used to test whether the function of the detection circuit is normal to determine whether the arc fault breaker is working normally. The detection circuit is used to detect whether there is a DC arc in the photovoltaic inverter 100.

[0048] When judging whether the arc fault breaker is working properly, the controller 120 sends a control signal to the noise generating circuit 140, so that the noise generating circuit 140 generates a noise signal having the same frequency spectrum characteristics as the arc noise signal, and transmits the noise signal to the third coil L3 in the current transformer 130. The fourth coil L4 in the current transformer 130 samples the noise signal and outputs a sampled signal, and the filter amplifier circuit 150 filters the sampled signal and outputs a conditioned signal. The controller 120 can determine whether the arc fault breaker is working properly by comparing whether the frequency of the conditioned signal is the same as the frequency of the noise signal. When the controller 120 controls the photovoltaic inverter 100 to be connected to the grid based on this, the reliability and safety of the photovoltaic inverter 100 can be ensured.

[0049] However, the controller 120 cannot accurately determine whether the arc fault breaker is working properly by comparing the frequency of the conditioned signal and the frequency of the noise signal. When the controller 120 controls the photovoltaic inverter 100 to be connected to the grid based on this, the reliability and safety of the photovoltaic inverter 100 will be low. Secondly, the circuit topology of the noise generating circuit 140 in the photovoltaic inverter 100 is complex, which will lead to a high cost of the photovoltaic inverter 100.

[0050] Based on this, an embodiment of the present application provides a power converter, in which a controller in the power converter can more accurately judge whether the arc fault breaker is working normally by comparing the frequency of the conditioning signal and the frequency of the pulse signal, and comparing the gain of the conditioning signal and the frequency corresponding to the gain threshold of the pulse signal. When the controller controls the power conversion circuit in the power converter to start working according to this, the safety and reliability of the power converter can be improved. At the same time, the noise signal conditioning circuit in the power converter includes a first resistor and a capacitor connected in series, and the circuit topology of the power converter is simpler and the cost is lower.

[0051] The power converter provided in the embodiment of the present application may be an optimizer, or a photovoltaic inverter, which is not limited in the embodiment of the present application. When the power converter is an optimizer, or a photovoltaic inverter, the power converter may be applied to a photovoltaic power generation system, which is not limited in the embodiment of the present application.

[0052] When the power converter provided in the embodiment of the present application is an optimizer and is applied to a photovoltaic power generation system, such as Figure 2 FIG. 4 is a schematic diagram of a circuit topology of a photovoltaic power generation system 400 provided in an embodiment of the present application. The photovoltaic power generation system 400 includes optimizers 411 to 41m and a photovoltaic inverter 420, where m is a positive integer. Figure 2 Each optimizer can be used to connect to a photovoltaic array, and each photovoltaic array includes at least one photovoltaic module. For example, optimizer 411 is used to connect to photovoltaic array 211, and optimizer 41m is used to connect to photovoltaic array 21n, where n is a positive integer. The output ends of the m optimizers from optimizer 411 to optimizer 41m are connected in series and then connected to the input end of photovoltaic inverter 420, and the output end of photovoltaic inverter 420 is used to connect to the power grid or load 300.

[0053] The photovoltaic arrays 211 to 21n are used to convert solar energy into direct current. After power conversion by the correspondingly connected optimizers 411 to 41m, the direct current output by the m optimizers is connected in series to the input end of the photovoltaic inverter 420. The photovoltaic inverter 420 is used to convert direct current into alternating current and transmit it to the power grid or load 300.

[0054] In a possible embodiment, the power converter provided in the embodiment of the present application may also be a photovoltaic inverter 420 .

[0055] When the power converter provided in the embodiment of the present application is a micro string inverter and is applied to a photovoltaic power generation system, such as Figure 3 FIG. 4 is a schematic diagram of a circuit topology of another photovoltaic power generation system 400 provided in an embodiment of the present application. The photovoltaic power generation system 400 includes micro string inverters 431 to 43k, where k is a positive integer. Figure 3 Each micro string inverter can be used to connect to a photovoltaic array, and each photovoltaic array includes at least one photovoltaic module. For example, micro string inverter 431 is used to connect to photovoltaic array 211, and micro string inverter 43k is used to connect to photovoltaic array 21n, where n is a positive integer. The output ends of the k micro string inverters from micro string inverter 431 to micro string inverter 43k are connected in parallel through a power line, which includes an AC live wire (L) and an AC neutral wire (N), and the power line is also connected to a power grid or a load 300.

[0056] Photovoltaic arrays 211 to 21n are used to convert solar energy into direct current, which is converted into alternating current with electrical parameters such as specific frequency and specific voltage required by the power grid or load 300 via correspondingly connected micro string inverters 431 to 43k. The alternating current is then provided to the power grid or load 300 for use via power lines.

[0057] like Figure 4 The circuit topology diagram of a power converter 500 provided in an embodiment of the present application is shown. The power converter 500 includes a current transformer 510, a power conversion circuit 520, a noise signal conditioning circuit 530, a sampling signal conditioning circuit 540 and a controller 550. The noise signal conditioning circuit 530 includes a first resistor R1 and a capacitor C connected in series. The embodiment of the present application does not limit the series connection order of the first resistor R1 and the capacitor C.

[0058] The current transformer 510 is used to be connected between the photovoltaic array 200 and the power conversion circuit 520. The output end of the power conversion circuit 520 is used to be connected to the power grid or the load 300. The current transformer 510 is used to detect the current output by the photovoltaic array 200. The power conversion circuit 520 is used to perform power conversion on the DC power output by the photovoltaic array 200 to supply power to the power grid or the load 300. The power converter 500 has the function of an arc fault breaker. The current transformer 510 and the sampling signal conditioning circuit 540 are used for DC arc detection.

[0059] Reference Figure 4, when the power converter 500 performs DC arc detection:

[0060] The controller 550 is used to output a pulse signal. Optionally, the pulse signal includes a pulse frequency modulation (PFM) or pulse width modulation (PWM) signal, which is not limited in the embodiment of the present application.

[0061] In a possible embodiment, the controller 550 includes a digital signal processing (DSP) chip or a microcontroller unit (MCU), which may also be referred to as a single-chip microcomputer, and the embodiment of the present application does not limit this.

[0062] The noise signal conditioning circuit 530 is used to receive a pulse signal and output a noise signal according to the pulse signal. Specifically, after the noise signal conditioning circuit 530 receives the pulse signal, the first resistor R1 in the noise signal conditioning circuit 530 is used as a current limiting resistor to limit the current peak of the pulse signal, and the capacitor C is used as a DC isolation capacitor to isolate the DC component in the pulse signal, so that the noise signal conditioning circuit 530 outputs a noise signal. Compared with the noise generating circuit 140 in the above-mentioned photovoltaic inverter 100, the noise signal conditioning circuit 530 provided in the embodiment of the present application includes a first resistor R1 and a capacitor C connected in series, and the circuit topology of the noise signal conditioning circuit 530 is simpler, which can reduce the cost of the power converter 500.

[0063] The current transformer 510 is used to receive and sample the noise signal to output a sampled signal.

[0064] In a possible embodiment, Figure 5 As shown, the current transformer 510 includes a second resistor R2, and a first coil L1, a second coil L2, a third coil L3 and a fourth coil L4 that are magnetically coupled to each other. One end of the first coil L1 is used to connect the positive pole of the photovoltaic array 200, and the other end of the first coil L1 is connected to the positive input end of the power conversion circuit 520. One end of the second coil L2 is used to connect the negative pole of the photovoltaic array 200, and the other end of the second coil L2 is connected to the negative input end of the power conversion circuit 520. One end of the third coil L3 is connected to the output end of the noise signal conditioning circuit 530, and the input end of the noise signal conditioning circuit 530 is connected to the output end of the controller 550. The other end of the third coil L3 and one end of the fourth coil L4 are connected to the ground terminal G, and the other end of the fourth coil L4 is connected to the input end of the sampling signal conditioning circuit 540. The output end of the sampling signal conditioning circuit 540 is connected to the input end of the controller 550. The second resistor R2 is connected in parallel with the fourth coil L4.

[0065] Among them, the circuit composed of the third coil L3 and the noise signal conditioning circuit 530 can be called a self-test circuit, and the circuit composed of the fourth coil L4, the second resistor R2 and the sampling signal conditioning circuit 540 can be called a detection circuit. The self-test circuit is used to test whether the function of the detection circuit is normal, and the detection circuit is used to detect whether there is a DC arc in the power converter 500.

[0066] Specifically, refer to Figure 5 The above-mentioned current transformer 510 receives the noise signal and samples it to output the sampled signal, including: the third coil L3 in the current transformer 510 receives the noise signal, and the fourth coil L4 samples the noise signal to output the sampled signal.

[0067] The sampling signal conditioning circuit 540 is used to receive the sampling signal and output a conditioned signal according to the sampling signal.

[0068] In a possible embodiment, the sampling signal conditioning circuit 540 includes a second-order bandpass filter. The sampling signal conditioning circuit 540 is specifically used to receive a sampling signal, perform filtering and amplification processing on the sampling signal, and output a conditioned signal.

[0069] The controller 550 is also used to control the power conversion circuit 520 to start working when the absolute value of the difference between the frequency of the conditioned signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioned signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal. The embodiment of the present application does not limit the specific value of the frequency threshold and the specific value of the gain threshold corresponding to the frequency of the pulse signal.

[0070] In a possible embodiment, controlling the power conversion circuit 520 to start working includes: controlling the power conversion circuit 520 to perform power conversion on the direct current output by the photovoltaic array 200, such as direct current to direct current (DCDC) power conversion, or DCAC power conversion.

[0071] In a possible embodiment, the controller 120 may perform Fourier analysis on the conditioned signal to determine the gain of the conditioned signal.

[0072] Compared with the above-mentioned photovoltaic inverter 100, in which the controller 120 determines whether the arc fault breaker is working normally by comparing the frequency of the conditioning signal and the frequency of the noise signal, and controls the photovoltaic inverter 100 to be connected to the grid accordingly, in the power converter 500 provided in the embodiment of the present application, the controller 550 controls the power conversion circuit 520 to start working when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal, thereby controlling the power conversion circuit 520 to start working when it is more accurately determined that the arc fault breaker in the power converter 500 is working normally, thereby improving the reliability and safety of the power converter 500.

[0073] In a possible embodiment, before the power converter 500 leaves the factory, the gain threshold corresponding to each frequency pulse signal can be obtained through simulation or experiment, and the gain threshold corresponding to each frequency pulse signal can be stored in the controller 550. Therefore, after the power converter 500 leaves the factory, the controller 550 can determine that the arc fault interrupter is operating normally and control the power conversion circuit 520 to start operating when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal.

[0074] Specifically, before the power converter 500 leaves the factory, when the controller 550 outputs a pulse signal of each frequency, the controller 550 can obtain the gain of the conditioning signal corresponding to the pulse signal of each frequency. The gain of the conditioning signal can also be called a design gain threshold, and the gain of the conditioning signal can be used as the gain threshold of the pulse signal of the corresponding frequency. The relationship between the frequency of the pulse signal and the gain threshold corresponding to the frequency of the pulse signal can be expressed as follows: Figure 6 The Bode plot shown in FIG. 1 shows that the horizontal axis is the frequency of the pulse signal in kilohertz (KHz), and the vertical axis is the gain threshold corresponding to the frequency of the pulse signal in decibels (dB). Figure 6 , when the frequency of the pulse signal is 20KHz, the gain threshold corresponding to the frequency of the pulse signal 20KHz is 10dB. Figure 6 When the frequency of the pulse signal is 30KHz, the gain threshold corresponding to the frequency of the pulse signal is 15dB. The relationship between the frequency of other pulse signals and the gain threshold corresponding to the frequency of the pulse signal can be referred to Figure 6 , the embodiments of the present application will not be described in detail here.

[0075] For example, refer to Figure 5 and Figure 6, taking the frequency threshold as 0.1KHz, during a DC arc detection process, the controller 550 outputs a pulse signal with a frequency of 20KHz, and the controller 550 receives a conditioning signal with a frequency of 20KHz output by the sampling signal conditioning circuit 540, and the gain of the conditioning signal is 11dB. For example, the controller 550 can determine that the arc fault breaker is operating normally and control the power conversion circuit 520 to start operating when the absolute value of the difference between the frequency of the conditioning signal 20KHz and the frequency of the pulse signal 20KHz is 0 and is less than the frequency threshold of 0.1KHz, and the gain of the conditioning signal 11dB is greater than the gain threshold 10DB corresponding to the frequency of the pulse signal 20KHz.

[0076] In a possible embodiment, the controller 550 is also used to determine that the arc fault breaker in the power converter 500 is not operating normally when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal, and to issue an alarm indicating that the arc fault breaker is not operating normally, and to control the power converter 500 to shut down, thereby improving the reliability and safety of the power converter 500.

[0077] For example, refer to Figure 5 and Figure 6 , taking the frequency threshold as 0.1KHz, during a DC arc detection process, the frequency of the pulse signal output by the controller 550 is 20KHz, and the controller 550 receives the conditioned signal with a frequency of 19KHz output by the sampling signal conditioning circuit 540, and the gain of the conditioned signal is 10dB. For example, the controller 550 can determine that the arc fault breaker in the power converter 500 is not working properly when the absolute value 1KHz of the difference between the frequency of the conditioned signal 19KHz and the frequency of the pulse signal 20KHz is greater than the frequency threshold 0.1KHz, and control the power converter 500 to shut down.

[0078] For example, refer to Figure 5 and Figure 6 , taking the frequency threshold as 0.1KHz, during a DC arc detection process, the controller 550 outputs a pulse signal with a frequency of 20KHz, and the controller 550 receives a conditioning signal with a frequency of 20KHz output by the sampling signal conditioning circuit 540, and the gain of the conditioning signal is 9dB. For example, the controller 550 can determine that the arc fault breaker in the power converter 500 is not working properly and control the power converter 500 to shut down when the gain of the conditioning signal 9dB is less than the gain threshold 10dB corresponding to the frequency of the pulse signal 20KHz.

[0079] For example, refer to Figure 5 and Figure 6, taking the frequency threshold as 0.1KHz, during a DC arc detection process, the controller 550 outputs a pulse signal with a frequency of 20KHz, and the controller 550 receives a conditioning signal with a frequency of 19KHz output by the sampling signal conditioning circuit 540, and the gain of the conditioning signal is 9dB. For example, the controller 550 can determine that the arc fault breaker in the power converter 500 is not working properly and control the power converter 500 to shut down when the absolute value of the difference between the frequency of the conditioning signal 19KHz and the frequency of the pulse signal 20KHz is 1KHz greater than the frequency threshold of 0.1KHz, and the gain of the conditioning signal 9dB is less than the gain threshold 10dB corresponding to the frequency of the pulse signal 20KHz.

[0080] In a possible embodiment, the controller 550 outputs a pulse signal, including: the controller 550 outputs a pulse signal whose frequency changes according to a fixed step size in a DC arc detection, the frequency changing according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, the first frequency is less than the second frequency, or the first frequency is greater than the second frequency, and the embodiment of the present application does not limit the specific values ​​of the first frequency and the second frequency. Compared with the controller 550 outputting a pulse signal of each frequency in turn in a DC arc detection, the controller 550 outputs a pulse signal whose frequency changes according to a fixed step size in a DC arc detection. The controller 550 needs to compare fewer conditioning signals and pulse signals, so that it can more quickly determine whether the arc fault breaker in the power converter 500 is working normally, and the startup efficiency of the power converter 500 can be improved.

[0081] In one possible embodiment, referring to Figure 6 The frequency range threshold of the pulse signal output by the controller 550 is greater than or equal to 10 KHz and less than or equal to 100 KHz. The embodiment of the present application does not limit the specific value of the frequency range threshold of the pulse signal output by the controller 550.

[0082] In a possible embodiment, the fixed step size includes 5 KHz, 10 KHz, 15 KHz or 20 KHz. The embodiment of the present application does not limit the specific value of the fixed step size.

[0083] For example, Figure 7 As shown in (a), taking the first frequency as 10KHz, the second frequency as 100KHz, and the fixed step size as 10KHz as an example, the controller 550 can output a pulse signal with a frequency increasing from the first frequency 10KHz to the second frequency 100KHz according to the fixed step size of 10KHz in a DC arc detection.

[0084] For example, Figure 7As shown in (b), taking the first frequency as 100KHz, the second frequency as 10KHz, and the fixed step size as 10KHz as an example, the controller 550 can output a pulse signal with a frequency decreasing from the first frequency 100KHz to the second frequency 10KHz according to a fixed step size of 10KHz during a DC arc detection.

[0085] In a possible embodiment, the frequency range threshold of the pulse signal output by the controller 550 is greater than or equal to 20KHz and less than or equal to 60KHz. Compared with the frequency range threshold of the pulse signal output by the above-mentioned controller 550 being greater than or equal to 10KHz and less than or equal to 100KHz, by reducing the frequency range threshold of the pulse signal output by the controller 550, the controller 550 needs to compare fewer conditioning signals and pulse signals, so that it can more quickly determine whether the arc fault interrupter in the power converter 500 is working normally, and the startup efficiency of the power converter 500 can be improved.

[0086] In a possible embodiment, the power conversion circuit 520 is a DCDC power conversion circuit, and the power converter 500 can be called an optimizer. Figure 2 The output of the power converter 500 is used to be connected to the input of the photovoltaic inverter 420, or the output of the power converter 500 is used to be connected in series with the output of at least one power converter 500 and then connected to the input of the photovoltaic inverter 420, and the output of the photovoltaic inverter 420 is used to be connected to the power grid or the load 300.

[0087] In a possible embodiment, the power conversion circuit 520 is a DCAC power conversion circuit, and the output of the power conversion circuit 520 is used to connect to the power grid or load 300. The power converter 500 can be called a micro string inverter. The controller 550 is specifically used to control the power conversion circuit 520 to establish a connection with the power grid or load 300 when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal. When the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal, the power conversion circuit 520 is controlled to disconnect from the power grid or load 300.

[0088] In a possible embodiment, the power conversion circuit 520 is a DCAC power conversion circuit, and the power converter 500 may be the photovoltaic inverter 420 described above.

[0089] In the power converter 500 provided in the embodiment of the present application, the controller 550 controls the power conversion circuit 520 to start working when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal, so that the power conversion circuit 520 can be controlled to start working when the arc fault breaker in the power converter 500 is more accurately determined to be working normally, thereby improving the reliability and safety of the power converter 500. At the same time, the noise signal conditioning circuit 530 includes a first resistor R1 and a capacitor C connected in series, and the circuit topology of the noise signal conditioning circuit 530 is simpler, which can reduce the cost of the power converter 500.

[0090] In a possible embodiment, Figure 5 As shown, the power converter 500 also includes a drive circuit 560, which is arranged between the controller 550 and the noise signal conditioning circuit 530, so that when the driving capacity of the controller 550 is insufficient, additional driving capacity can be provided, thereby avoiding the controller 550 being unable to detect whether the arc fault breaker is working normally, and the reliability of the power converter 500 can be improved.

[0091] In a possible embodiment, the driving circuit 560 includes a buffer driver, a gate circuit, or a push-pull circuit, which is not limited in the embodiment of the present application.

[0092] The power converter 500 provided in the embodiment of the present application can provide additional driving capability when the driving capability of the controller 550 is insufficient by setting a driving circuit 560 between the controller 550 and the noise signal conditioning circuit 530, thereby avoiding the controller 550 being unable to detect whether the arc fault breaker is working normally, and improving the reliability of the power converter 500.

[0093] like Figure 8 As shown, an embodiment of the present application further provides a control method for a power converter, which is applied to the above-mentioned power converter 500, and the method includes steps S801 to S805.

[0094] S801. The controller 550 generates a pulse signal.

[0095] In a possible embodiment, the above-mentioned controller 550 generates a pulse signal, including: the controller 550 generates a pulse signal whose frequency changes according to a fixed step size during a DC arc detection, and the frequency change according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

[0096] In one possible embodiment, referring to Figure 6 The frequency range threshold of the pulse signal output by the controller 550 is greater than or equal to 10 KHz and less than or equal to 100 KHz. The embodiment of the present application does not limit the specific value of the frequency range threshold of the pulse signal output by the controller 550.

[0097] In a possible embodiment, the fixed step size includes 5 KHz, 10 KHz, 15 KHz or 20 KHz. The embodiment of the present application does not limit the specific value of the fixed step size.

[0098] In a possible embodiment, the frequency range threshold of the pulse signal output by the controller 550 is greater than or equal to 20KHz and less than or equal to 60KHz. Compared with the frequency range threshold of the pulse signal output by the above-mentioned controller 550 being greater than or equal to 10KHz and less than or equal to 100KHz, by reducing the frequency range threshold of the pulse signal output by the controller 550, the controller 550 needs to compare fewer conditioning signals and pulse signals, so that it can more quickly determine whether the arc fault interrupter in the power converter 500 is working normally, and the startup efficiency of the power converter 500 can be improved.

[0099] S802: The noise signal conditioning circuit 530 generates a noise signal according to the pulse signal.

[0100] S803: The current transformer 510 generates a sampling signal according to the noise signal.

[0101] S804 , the sampling signal conditioning circuit 540 generates a conditioning signal according to the sampling signal.

[0102] S805, the controller 550 controls the power conversion circuit 520 in the power converter 500 to start working when the absolute value of the difference between the frequency of the conditioned signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioned signal is greater than or equal to the frequency corresponding gain threshold of the pulse signal. The embodiment of the present application does not limit the specific value of the frequency threshold and the specific value of the frequency corresponding gain threshold of the pulse signal.

[0103] In the control method of the power converter provided in the embodiment of the present application, the controller 550 controls the power conversion circuit 520 in the power converter 500 to start working when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal. In this way, the power conversion circuit 520 in the power converter 500 can be controlled to start working when it is more accurately determined that the arc fault interrupter in the power converter 500 is working normally, thereby improving the reliability and safety of the power converter 500.

[0104] In a possible embodiment, Figure 8 As shown, the control method of the power converter provided in the embodiment of the present application also includes step S806. When executing, step S806 and the above-mentioned step S805 can be selected to be executed based on the relationship between the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal and the frequency threshold, and the relationship between the gain of the conditioning signal and the frequency corresponding to the gain threshold of the pulse signal.

[0105] S806. The controller 550 controls the power converter 500 to shut down when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than the frequency threshold, or when the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal.

[0106] In the control method of the power converter provided in the embodiment of the present application, when the absolute value of the difference between the frequency of the conditioned signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioned signal is less than the gain threshold corresponding to the frequency of the pulse signal, the controller 550 determines that the arc fault breaker in the power converter 500 is not operating normally, and issues an alarm to indicate that the arc fault breaker is not operating normally, and controls the power converter 500 to shut down, thereby improving the reliability and safety of the power converter 500.

[0107] Based on this, an embodiment of the present application further provides a photovoltaic power generation system, which includes a power converter.

[0108] In a possible embodiment, the circuit topology diagram of the photovoltaic power generation system is as follows: Figure 2 The circuit topology diagram of the photovoltaic power generation system 400 shown in FIG. 4 includes optimizers 411 to 41m and a photovoltaic inverter 420, where m is a positive integer. Figure 2 , each optimizer can be used to connect to a photovoltaic array, and each photovoltaic array includes at least one photovoltaic module. For example, optimizer 411 is used to connect to photovoltaic array 211, and optimizer 41m is used to connect to photovoltaic array 21n, where n is a positive integer. The output ends of the m optimizers from optimizer 411 to optimizer 41m are connected in series and then connected to the input end of photovoltaic inverter 420, and the output end of photovoltaic inverter 420 is used to connect to the power grid or load 300. Among them, optimizer 411 to optimizer 41m can also be called power converter, and the circuit topology diagram of any optimizer can be the above Figure 4 or Figure 5 A circuit topology diagram of a power converter 500 is shown.

[0109] In a possible embodiment, the circuit topology diagram of the photovoltaic power generation system is as follows: Figure 3The circuit topology diagram of the photovoltaic power generation system 400 shown in the figure includes micro string inverters 431 to micro string inverters 43k, where k is a positive integer. Each micro string inverter can be used to connect to a photovoltaic array, and each photovoltaic array includes at least one photovoltaic component. For example, the micro string inverter 431 is used to connect to the photovoltaic array 211, and the micro string inverter 43k is used to connect to the photovoltaic array 21n, where n is a positive integer. The output ends of the k micro string inverters from the micro string inverter 431 to the micro string inverter 43k are connected in parallel through a power line, and the power line includes an AC live wire and an AC neutral wire, and the power line is also connected to the power grid or load 300. Among them, the micro string inverters 431 to the micro string inverter 43k can also be called power converters, and the circuit topology diagram of any micro string inverter can be the above Figure 4 or Figure 5 A circuit topology diagram of a power converter 500 is shown.

[0110] The above detailed description of the power converter 500 and the analysis of the beneficial effects can be correspondingly referred to the control method of the power converter and the photovoltaic power generation system 400, and the embodiments of the present application will not be repeated here.

[0111] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A power converter, characterized in that: The power converter includes a current transformer, a power conversion circuit, a noise signal conditioning circuit, a sampling signal conditioning circuit and a controller, wherein the noise signal conditioning circuit includes a first resistor and a capacitor connected in series; wherein the current transformer is used to be connected between the photovoltaic array and the power conversion circuit, the current transformer is used to detect the current output by the photovoltaic array, and the power conversion circuit is used to perform power conversion on the direct current output by the photovoltaic array; the current transformer and the sampling signal conditioning circuit are used for direct current arc detection; The controller is used to output a pulse signal; The noise signal conditioning circuit is used to receive the pulse signal and output a noise signal according to the pulse signal; The current transformer is used to receive and sample the noise signal to output a sampled signal; The sampling signal conditioning circuit is used to receive the sampling signal and output a conditioning signal according to the sampling signal; The controller is also used to control the power conversion circuit to start working when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to a frequency threshold, and the gain of the conditioning signal is greater than or equal to a gain threshold corresponding to the frequency of the pulse signal.

2. The power converter according to claim 1, characterized in that: The controller is also used to control the power converter to shut down when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than the frequency threshold, or when the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal.

3. The power converter according to claim 1 or 2, characterized in that: The controller is specifically used to output the pulse signal whose frequency changes according to a fixed step size during a DC arc detection. The frequency change according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

4. The power converter according to claim 3, characterized in that: The fixed step size includes 5KHz, 10KHz, 15KHz or 20KHz.

5. The power converter according to any one of claims 1 to 4, characterized in that: The frequency range threshold of the pulse signal is greater than or equal to 20 KHz and less than or equal to 60 KHz.

6. The power converter according to any one of claims 1 to 5, characterized in that: The power converter further includes a driving circuit, wherein the driving circuit is arranged between the controller and the noise signal conditioning circuit, and the sampling signal conditioning circuit is a second-order bandpass filter.

7. The power converter according to any one of claims 1 to 6, characterized in that: The current transformer comprises a second resistor, and a first coil, a second coil, a third coil and a fourth coil which are magnetically coupled to each other; One end of the first coil is used to connect the positive pole of the photovoltaic array, and the other end of the first coil is connected to the positive input end of the power conversion circuit; one end of the second coil is used to connect the negative pole of the photovoltaic array, and the other end of the second coil is connected to the negative input end of the power conversion circuit; One end of the third coil is connected to the output end of the noise signal conditioning circuit, the other end of the third coil and one end of the fourth coil are connected to the ground end, the other end of the fourth coil is connected to the input end of the sampling signal conditioning circuit, and the second resistor is connected in parallel with the fourth coil.

8. The power converter according to any one of claims 1 to 7, characterized in that: The power conversion circuit is a DCDC power conversion circuit, the output of the power converter is used to be connected to the input of an inverter, or the output of the power converter is used to be connected in series with the output of at least one power converter and then connected to the input of the inverter, and the output of the inverter is used to be connected to a power grid or a load.

9. The power converter according to any one of claims 1 to 7, characterized in that: The power conversion circuit is a DCAC power conversion circuit, and the output of the power conversion circuit is used to connect to a power grid or a load; The controller is specifically used to control the power conversion circuit to establish a connection with the power grid or the load when the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal; When the absolute value of the difference between the frequency of the conditioned signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioned signal is less than the gain threshold corresponding to the frequency of the pulse signal, the power conversion circuit is controlled to be disconnected from the power grid or the load.

10. A method for controlling a power converter, characterized in that: Applied to a power converter, the method comprises: generating a pulse signal; generating a noise signal according to the pulse signal; generating a sampling signal according to the noise signal; generating a conditioned signal according to the sampled signal; When the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is less than or equal to the frequency threshold, and the gain of the conditioning signal is greater than or equal to the gain threshold corresponding to the frequency of the pulse signal, the power conversion circuit in the power converter is controlled to start working.

11. The method according to claim 10, characterized in that The method further comprises: When the absolute value of the difference between the frequency of the conditioning signal and the frequency of the pulse signal is greater than the frequency threshold, or the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal, the power converter is controlled to shut down.

12. The method according to claim 10 or 11, characterized in that: The generating of the pulse signal comprises: In a DC arc detection, a pulse signal is generated whose frequency changes according to a fixed step size. The frequency change according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

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