A power converter and a control method thereof

Abstract

The embodiment of the application discloses a kind of power converter and its control method, it is related to energy technology field, it solves how to accurately judge arc fault breaker whether normal work problem.Specifically, in power converter: controller is used to output pulse signal.Noise signal conditioning circuit is used to receive pulse signal, and noise signal is exported according to pulse signal.Current transformer is used to receive noise signal and sample, to output sampling signal.Sampling signal conditioning circuit is used to receive sampling signal, and conditioning signal is exported according to sampling signal.Controller is also used to in the absolute value of the difference between the frequency of conditioning signal and the frequency of pulse signal is less than or equal to frequency threshold value, and the gain of conditioning signal is greater than or equal to the frequency corresponding gain threshold value of pulse signal, situation, control power conversion circuit starts work.

Description

Technical Field

[0001] This application relates to the field of energy technology, and in particular to a power converter and its control method. Background Technology

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

[0003] Photovoltaic power generation systems have a long service life, but due to faults such as cable aging or unreliable terminal connections, DC arc faults can easily occur, leading to electrical fires. To avoid these problems, an arc-fault circuit-interrupter (AFCI) can be installed in the photovoltaic inverter or optimizer. This AFCI can also be called an arc-fault circuit breaker.

[0004] However, determining whether the arc fault disconnector is working properly, and then controlling the power conversion circuit in the photovoltaic inverter or optimizer to start working when the arc fault disconnector is working properly, in order 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] This application provides a power converter and its control method, which solves the problem of how to accurately determine whether an arc fault disconnector is working properly.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] A first aspect of this application provides a power converter, which includes a current transformer, a power conversion circuit, a noise signal conditioning circuit, a sampling signal conditioning circuit, and a controller. The noise signal conditioning circuit includes a first resistor and a capacitor connected in series. The current transformer is connected between a photovoltaic array and the power conversion circuit, and is used to detect the current output by the photovoltaic array. The power conversion circuit is used to convert the DC power output by the photovoltaic array. The current transformer and the sampling signal conditioning circuit are used for DC 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 based on the pulse signal. The current transformer is used to receive the noise signal and sample it to output a sampled signal. The sampling signal conditioning circuit is used to receive the sampled signal and output a conditioned signal based on the sampled signal. The controller is further used to control the power conversion circuit to start operating 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 a 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 scheme, the controller starts the power conversion circuit 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 the gain threshold corresponding to the frequency of the pulse signal. This allows for more accurate determination of the arc fault interrupter's normal operation before controlling the power conversion circuit to start working, thus improving the reliability and safety of the power converter. Simultaneously, the noise signal conditioning circuit includes a first resistor and a capacitor connected in series, resulting in a simpler circuit topology and reducing the cost of the power converter.

[0009] In conjunction with the first aspect, in one possible implementation, the controller is further configured to shut down the power converter 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 the gain threshold corresponding to the frequency of the pulse signal.

[0010] Based on this scheme, if 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 if the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal, the controller determines that the arc fault disconnector in the power converter is not working properly, and issues an alarm indicating that the arc fault disconnector is not working properly, and controls the power converter to shut down, thereby improving the reliability and safety of the power converter.

[0011] In conjunction with the first aspect, in one possible implementation, the controller is specifically used to output a pulse signal whose frequency varies in fixed steps during a single DC arc detection. The frequency variation in fixed steps includes adjusting the frequency from a first frequency to a second frequency in fixed steps, where 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 pulse signals of each frequency sequentially in a single DC arc detection, the controller outputs pulse signals with frequencies varying according to a fixed step size in a single DC arc detection. The controller needs to compare fewer conditioning signals and pulse signals, thus determining more quickly whether the arc fault disconnector in the power converter is working properly, which can improve the start-up efficiency of the power converter.

[0013] In conjunction with the first aspect, in one possible implementation, the fixed step size includes 5kHz, 10kHz, 15kHz or 20kHz.

[0014] In conjunction with the first aspect, in one possible implementation, 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 scheme, 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 conditioning signals and pulse signals, thereby determining more quickly whether the arc fault interruptor in the power converter is working properly, which can improve the start-up efficiency of the power converter.

[0016] In conjunction with the first aspect, in one possible implementation, the power converter further includes a drive circuit, which is disposed 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 drive circuit between the controller and the noise signal conditioning circuit, additional drive capability can be provided when the controller's drive capability is insufficient. This can prevent the controller from failing to detect whether the arc fault interrupter is working properly, thereby improving the reliability of the power converter.

[0018] In conjunction with the first aspect, in one possible implementation, the current transformer includes a second resistor and four magnetically coupled coils: a first coil, a second coil, a third coil, and a fourth coil. One end of the first coil is connected to the positive terminal of the photovoltaic array, and the other end is connected to the positive input terminal of the power conversion circuit. One end of the second coil is connected to the negative terminal of the photovoltaic array, and the other end is connected to the negative input terminal of the power conversion circuit. One end of the third coil is connected to the output terminal of a noise signal conditioning circuit, and the other ends of the third and fourth coils are connected to ground. The other end of the fourth coil is connected to the input terminal of a sampling signal conditioning circuit. The second resistor is connected in parallel with the fourth coil.

[0019] In conjunction with the first aspect, in one possible implementation, the power conversion circuit is a DC-DC power conversion circuit, the output of the power converter is used to connect to the input of the inverter, or the output of the power converter is used to connect to the input of the inverter after being connected in series with the output of at least one power converter, and the output of the inverter is used to connect to the power grid or load.

[0020] In conjunction with the first aspect, in one possible implementation, the power conversion circuit is a DC-AC power conversion circuit, and its output is used to connect to the power grid or load. Specifically, the controller is used to establish a connection between the power conversion circuit and the power grid or 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 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. Conversely, the controller controls the power conversion circuit to disconnect from the power grid or load 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.

[0021] A second aspect of this application provides a control method for a power converter, applied to a power converter. The method includes: generating a pulse signal; generating a noise signal based on the pulse signal; generating a sampling signal based on the noise signal; generating a conditioning signal based on the sampling signal; and controlling a power conversion circuit in the power converter 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 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.

[0022] In conjunction with the second aspect, in one possible implementation, the method further 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 the gain threshold corresponding to the frequency of the pulse signal.

[0023] In conjunction with the second aspect, in one possible implementation, the above-mentioned generation of pulse signals includes: in a single DC arc detection, generating a pulse signal whose frequency varies in fixed steps, wherein the frequency variation in fixed steps includes adjusting the frequency from a first frequency to a second frequency in fixed steps, wherein the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

[0024] In conjunction with the second aspect, in one possible implementation, the fixed step size includes 5kHz, 10kHz, 15kHz, or 20kHz.

[0025] In conjunction with the second aspect, in one possible implementation, 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] A third aspect of this application provides a photovoltaic power generation system, which includes a plurality of optimizers and a photovoltaic inverter. Each optimizer can be connected to a photovoltaic array. The output terminals of the plurality of optimizers are connected in series and then connected to the input terminal of the photovoltaic inverter. The output terminal of the photovoltaic inverter is used to connect to the power grid or a load. The optimizer can also be referred to as a power converter. The power converter is the power converter described in the first aspect or any possible implementation of the first aspect.

[0027] A fourth aspect of this application provides a photovoltaic power generation system comprising a plurality of micro string inverters, each micro string inverter being connected to a photovoltaic array, each photovoltaic array comprising at least one photovoltaic module, the output terminals of the plurality of micro string inverters being connected in parallel via a power line connected to a power grid or load, the micro string inverter being referred to as a power converter, the power converter being as described in the first aspect above or any possible implementation thereof.

[0028] The descriptions of the second to fourth aspects in this application can be referred to the detailed description of the first aspect; and the beneficial effects of the second to fourth aspects can be referred to the analysis of the beneficial effects of the first aspect, which will not be repeated here. Attached Figure Description

[0029] Figure 1 This application provides a schematic diagram of the circuit topology of a photovoltaic inverter.

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

[0031] Figure 3 This is a schematic diagram of another photovoltaic power generation system provided in an embodiment of this application;

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

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

[0034] Figure 6 A Bode plot provided for an embodiment of this application;

[0035] Figure 7 This is a schematic diagram of pulse signal frequency adjustment provided in an embodiment of this application;

[0036] Figure 8 This is a flowchart illustrating a control method for a power converter provided in an embodiment of this application. Detailed Implementation

[0037] The following sections will discuss the fabrication and use of various embodiments in detail. However, it should be understood that many applicable inventive concepts provided in this application can be implemented in a variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways of implementing and using this description and technology, and do not limit the scope of this application.

[0038] Unless otherwise defined, all technical terms used herein have the same meaning as commonly known to one of ordinary skill in the art.

[0039] Each circuit or other component may be described or referred to as "for" performing one or more tasks. In this context, "for" is used to imply a structure by indicating that the circuit / component includes a structure (e.g., a circuit system) that performs one or more tasks during operation. Therefore, even when the specified circuit / component is currently inoperable (e.g., not turned on), it can still be referred to as "for performing that task." Circuits / components used with the term "for" include hardware, such as circuits that perform operations.

[0040] The technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings. In this application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: 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 embodiments of this application, the words "first," "second," etc., do not limit the quantity or order.

[0041] In this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0042] Before introducing the embodiments of this application, the technical terms and background technology involved in this application will be introduced first.

[0043] Current transformer (CT): A current transformer is an instrument that measures a large primary current by converting a small secondary current into a large primary current based on the principle of electromagnetic induction. A 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, but are prone to DC arcing faults due to cable aging or unreliable terminal connections, which can lead to electrical fires. To avoid this problem, arcing fault interrupters can be installed in photovoltaic inverters or optimizers. For example, taking a photovoltaic inverter as an example... Figure 1 The diagram shown is a circuit topology diagram of a photovoltaic inverter 100 provided in an embodiment of this application. 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 generation circuit 140, and a filter amplifier circuit 150. The circuit composed of the current transformer 130, the noise generation circuit 140, and the filter amplifier circuit 150 can be called an arc fault disconnector.

[0045] A current transformer 130 is connected between the photovoltaic array 200 and the DCAC power conversion circuit 110. The output of the DCAC power conversion circuit 110 is used to connect to the power grid or load 300. The current transformer 130 is used to detect the current output by the photovoltaic array 200. The DCAC power conversion circuit 110 is used to convert the DC power output by the photovoltaic array 200 into AC power and transmit it to the power grid or 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 four coils L1, L2, L3, and L4 that are magnetically coupled to each other. The first coil L1 is connected between the positive terminal of the photovoltaic array 200 and the positive input terminal of the DCAC power conversion circuit 110. The second coil L2 is connected between the negative terminal 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 generation circuit 140, and the input terminal of the noise generation 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 (G). The other end of the fourth coil L4 is connected to the input terminal of the filter amplifier circuit 150, and 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] The circuit consisting of the third coil L3 and the noise generation circuit 140 can be called a self-test circuit, and the circuit consisting 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, so as to determine whether the arc fault disconnector is working properly. The detection circuit is used to detect whether there is a DC arc in the photovoltaic inverter 100.

[0048] When determining whether the arc fault disconnector is working properly, the controller 120 sends a control signal to the noise generation circuit 140, causing the noise generation circuit 140 to generate a noise signal with the same spectral characteristics as the arc noise signal, and transmit it 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. The filter amplifier circuit 150 filters the sampled signal and outputs a conditioning signal. By comparing the frequency of the conditioning signal with the frequency of the noise signal, the controller 120 can determine whether the arc fault disconnector is working properly. Based on this, when the photovoltaic inverter 100 is connected to the grid, the controller 120 can ensure the reliability and safety of the photovoltaic inverter 100.

[0049] However, by comparing the frequency of the conditioning signal with the frequency of the noise signal, the controller 120 cannot accurately determine whether the arc fault interrupter is working properly. If the controller 120 uses this information to control the photovoltaic inverter 100 to connect to the grid, the reliability and safety of the photovoltaic inverter 100 will be low. Secondly, the complex circuit topology of the noise generation circuit 140 in the photovoltaic inverter 100 will result in a higher cost for the photovoltaic inverter 100.

[0050] Based on this, this application provides a power converter. The controller in this power converter compares the frequency of a conditioning signal with the frequency of a pulse signal, and compares the gain of the conditioning signal with the gain threshold corresponding to the frequency of the pulse signal. This allows for a more accurate determination of whether the arc fault interrupter is functioning correctly. When the controller controls the power conversion circuit in the power converter to start operating based on this comparison, the safety and reliability of the power converter can be improved. Furthermore, the noise signal conditioning circuit in this power converter includes a first resistor and a capacitor connected in series, resulting in a simpler circuit topology and lower cost.

[0051] The power converter provided in this application embodiment can be an optimizer or a photovoltaic inverter, and this application embodiment does not limit it in this regard. When the power converter is an optimizer or a photovoltaic inverter, the power converter can be applied to a photovoltaic power generation system, and this application embodiment does not limit it in this regard.

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

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

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

[0055] When the power converter provided in this application embodiment is a micro string inverter and is applied to a photovoltaic power generation system, such as Figure 3 The diagram shown is a circuit topology schematic of another photovoltaic power generation system 400 provided in an embodiment of this application. The photovoltaic power generation system 400 includes micro-string inverters 431 to 43k, where k is a positive integer. (Refer to...) Figure 3 Each micro-string inverter can be connected 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 terminals of the k micro-string inverters 431 to 43k are connected in parallel via power lines, which include an AC live wire (L) and an AC neutral wire (N), and are also connected to the power grid or load 300.

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

[0057] like Figure 4 The diagram shows a circuit topology of a power converter 500 according to an embodiment of this application. 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. This embodiment of the application does not limit the series connection order of the first resistor R1 and the capacitor C.

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

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

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

[0061] In one 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. This application embodiment does not limit this.

[0062] The noise signal conditioning circuit 530 receives pulse signals and outputs noise signals based on the pulse signals. Specifically, after receiving the pulse signal, the first resistor R1 in the noise signal conditioning circuit 530 acts as a current-limiting resistor to limit the peak current of the pulse signal, and the capacitor C acts as a DC-blocking 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 generation circuit 140 in the photovoltaic inverter 100 described above, the noise signal conditioning circuit 530 provided in this embodiment includes a first resistor R1 and a capacitor C connected in series. The circuit topology of this 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 noise signals in order to output a sampled signal.

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

[0065] The circuit consisting of the third coil L3 and the noise signal conditioning circuit 530 can be called a self-test circuit, and the circuit consisting 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 current transformer 510 receives and samples noise signals to output a sampled signal, including: the third coil L3 in the current transformer 510 receives noise signals, and the fourth coil L4 samples the noise signals to output a sampled signal.

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

[0068] In one possible embodiment, the sampling signal conditioning circuit 540 includes a second-order bandpass filter. Specifically, the sampling signal conditioning circuit 540 receives a sampled signal, filters and amplifies the sampled signal to 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 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 the gain threshold corresponding to the frequency of the pulse signal. In this embodiment, the specific value of the frequency threshold and the specific value of the gain threshold corresponding to the frequency of the pulse signal are not limited.

[0070] In one possible embodiment, controlling the power conversion circuit 520 to start operating 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 one possible embodiment, the controller 120 can perform Fourier analysis on the conditioning signal to determine the gain of the conditioning signal.

[0072] Compared to the photovoltaic inverter 100 described above, where the controller 120 determines whether the arc fault disconnector is working properly by comparing the frequency of the conditioning signal and the frequency of the noise signal, and controls the photovoltaic inverter 100 to connect to the grid accordingly, in the power converter 500 provided in this application embodiment, 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 a 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. This allows for more accurate determination that the arc fault disconnector in the power converter 500 is working properly before controlling the power conversion circuit 520 to start working, thereby improving the reliability and safety of the power converter 500.

[0073] In one 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 experimentation. The gain threshold corresponding to each frequency pulse signal can be stored in the controller 550. Thus, after the power converter 500 leaves the factory, the controller 550 can determine that the arc fault disconnector is working normally and control 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.

[0074] Specifically, before the power converter 500 leaves the factory, when the controller 550 outputs a pulse signal at each frequency, the controller 550 can obtain the gain of the conditioning signal corresponding to each frequency pulse signal. This gain of the conditioning signal can also be called the design gain threshold, and it can be used as the gain threshold for the corresponding frequency pulse signal. The relationship between the frequency of the pulse signal and the corresponding gain threshold can be expressed as follows: Figure 6 The Bode plot shown represents the pulse signal frequency on the horizontal axis (kHz) and the gain threshold corresponding to that frequency on the vertical axis (dB). For example, refer to... Figure 6 When the frequency of the pulse signal is 20kHz, the gain threshold corresponding to a pulse signal frequency of 20kHz is 10dB. For example, refer to... Figure 6 When the frequency of the pulse signal is 30kHz, the corresponding gain threshold is 15dB. The relationship between the frequencies of other pulse signals and their corresponding gain thresholds can be found by referring to... Figure 6 The embodiments of this application will not be described in detail here.

[0075] For example, refer to Figure 5 and Figure 6Taking a frequency threshold of 0.1kHz as an example, during a DC arc detection process, the controller 550 outputs a pulse signal with a frequency of 20kHz. 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. If 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 less than the frequency threshold of 0.1kHz, and the gain of the conditioning signal (11dB) is greater than the gain threshold of 10dB corresponding to the frequency of the pulse signal (20kHz), the controller 550 determines that the arc fault disconnector is working normally and controls the power conversion circuit 520 to start working.

[0076] In one possible embodiment, the controller 550 is further configured to determine that the arc fault disconnector in the power converter 500 is not working properly 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 the gain threshold corresponding to the frequency of the pulse signal, and to issue an alarm indicating that the arc fault disconnector is not working properly, and 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 a frequency threshold of 0.1 kHz as an example, during a DC arc detection process, the controller 550 outputs a pulse signal with a frequency of 20 kHz, and the controller 550 receives a conditioning signal with a frequency of 19 kHz output by the sampling signal conditioning circuit 540. The gain of this conditioning signal is 10 dB. If the absolute value of the difference between the frequency of the conditioning signal (19 kHz) and the frequency of the pulse signal (20 kHz) is greater than the frequency threshold of 0.1 kHz, the controller 550 can determine that the arc fault disconnector in the power converter 500 is not working properly and control the power converter 500 to shut down.

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

[0079] For example, refer to Figure 5 and Figure 6Taking a DC arc detection process with a frequency threshold of 0.1 kHz, where the controller 550 outputs a pulse signal with a frequency of 20 kHz and receives a conditioning signal with a frequency of 19 kHz from the sampling signal conditioning circuit 540, and the gain of this conditioning signal is 9 dB, the controller 550 can determine that the arc fault disconnector in the power converter 500 is not working properly and control the power converter 500 to shut down if the absolute value of the difference between the frequency of the conditioning signal 19 kHz and the frequency of the pulse signal 20 kHz is greater than the frequency threshold of 0.1 kHz and the gain of the conditioning signal 9 dB is less than the gain threshold of 10 dB corresponding to the frequency of the pulse signal 20 kHz.

[0080] In one possible embodiment, the controller 550 outputs a pulse signal, including: during a DC arc detection, the controller 550 outputs a pulse signal with a frequency varying according to a fixed step size. This frequency variation includes adjusting the frequency from a first frequency to a second frequency, where the first frequency is less than the second frequency, or the first frequency is greater than the second frequency. This embodiment does not limit the specific values ​​of the first and second frequencies. Compared to the controller 550 sequentially outputting pulse signals of each frequency during a DC arc detection, the controller 550 outputs a pulse signal with a frequency varying according to a fixed step size. This reduces the number of conditioning signals and pulse signals the controller 550 needs to compare, allowing for faster determination of whether the arc fault disconnector in the power converter 500 is functioning correctly, thus improving the start-up efficiency of the power converter 500.

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

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

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

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

[0085] In one possible embodiment, the frequency range threshold of the output pulse signal of the controller 550 is greater than or equal to 20KHz and less than or equal to 60KHz. Compared with the above-mentioned frequency range threshold of the output pulse signal of the controller 550 being greater than or equal to 10KHz and less than or equal to 100KHz, by reducing the frequency range threshold of the output pulse signal of the controller 550, the controller 550 needs to compare fewer conditioning signals and pulse signals, thereby determining more quickly whether the arc fault disconnector in the power converter 500 is working properly, which can improve the start-up efficiency of the power converter 500.

[0086] In one possible embodiment, the power conversion circuit 520 is a DC-DC power conversion circuit, and the power converter 500 can be referred to as an optimizer. (See also...) Figure 2 The output of the power converter 500 is used to connect to the input of the photovoltaic inverter 420, or the output of the power converter 500 is used to connect to the input of the photovoltaic inverter 420 after being connected in series with the output of at least one power converter 500. The output of the photovoltaic inverter 420 is used to connect to the grid or the load 300.

[0087] In one possible embodiment, the power conversion circuit 520 is a DC-AC power conversion circuit, the output of which is used to connect to the power grid or load 300. This power converter 500 can be referred to as a miniature string inverter. Specifically, the controller 550 controls 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 a 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 when the gain of the conditioning signal is less than the gain threshold corresponding to the frequency of the pulse signal, the controller controls the power conversion circuit 520 to disconnect from the power grid or load 300.

[0088] In one possible embodiment, the power conversion circuit 520 is a DCAC power conversion circuit, and the power converter 500 can be the aforementioned photovoltaic inverter 420.

[0089] The power converter 500 provided in this application embodiment allows the controller 550 to 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 a 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. This allows for more accurate determination of the arc fault interrupter's normal operation within the power converter 500, thereby improving the reliability and safety of the power converter 500. Simultaneously, the noise signal conditioning circuit 530 includes a first resistor R1 and a capacitor C connected in series. The circuit topology of this noise signal conditioning circuit 530 is simpler, reducing the cost of the power converter 500.

[0090] In one possible embodiment, such as Figure 5 As shown, the power converter 500 also includes a drive circuit 560, which is located between the controller 550 and the noise signal conditioning circuit 530. This allows the power converter 500 to provide additional drive capability when the controller 550's drive capability is insufficient. This prevents the controller 550 from failing to detect whether the arc fault disconnector is working properly, thereby improving the reliability of the power converter 500.

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

[0092] The power converter 500 provided in this application embodiment provides 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. This can prevent the controller 550 from failing to detect whether the arc fault disconnector is working properly and improve the reliability of the power converter 500.

[0093] like Figure 8 As shown, this application embodiment also provides a control method for a power converter, applied to the power converter 500 described above, the method including steps S801-S805.

[0094] S801 and controller 550 generate pulse signals.

[0095] In one possible embodiment, the controller 550 generates a pulse signal, including: in a DC arc detection, the controller 550 generates a pulse signal with a frequency that varies according to a fixed step size, wherein the frequency variation according to the fixed step size includes adjusting the frequency from a first frequency to a second frequency according to a fixed step size, wherein the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

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

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

[0098] In one possible embodiment, the frequency range threshold of the output pulse signal of the controller 550 is greater than or equal to 20KHz and less than or equal to 60KHz. Compared with the above-mentioned frequency range threshold of the output pulse signal of the controller 550 being greater than or equal to 10KHz and less than or equal to 100KHz, by reducing the frequency range threshold of the output pulse signal of the controller 550, the controller 550 needs to compare fewer conditioning signals and pulse signals, thereby determining more quickly whether the arc fault disconnector in the power converter 500 is working properly, which can improve the start-up efficiency of the power converter 500.

[0099] S802, Noise signal conditioning circuit 530 generates noise signal based on pulse signal.

[0100] S803 and current transformer 510 generate sampling signals based on noise signals.

[0101] S804, the sampling signal conditioning circuit 540 generates a conditioning signal based on the sampling signal.

[0102] In step S805, 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 the gain threshold corresponding to the frequency of the pulse signal, the controller 550 controls the power conversion circuit 520 in the power converter 500 to start working. This embodiment does not limit the specific value of the frequency threshold or the specific value of the gain threshold corresponding to the frequency of the pulse signal.

[0103] The control method for the power converter provided in this application embodiment allows the controller 550 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 the gain threshold corresponding to the frequency of the pulse signal. This allows the controller 550 to start working the power conversion circuit 520 in the power converter 500 when it is more accurately determined that the arc fault disconnector in the power converter 500 is working normally, thereby improving the reliability and safety of the power converter 500.

[0104] In one possible embodiment, such as Figure 8 As shown, the control method for the power converter provided in this application embodiment further includes step S806. When step S806 and step S805 are executed, they 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 gain threshold corresponding to the frequency of the pulse signal.

[0105] S806, controller 550 controls power converter 500 to stop 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] The control method for the power converter provided in this application embodiment determines that the arc fault disconnector in the power converter 500 is not working properly 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 the gain threshold corresponding to the frequency of the pulse signal. The controller 550 then issues an alarm indicating that the arc fault disconnector is not working properly and controls the power converter 500 to shut down, thereby improving the reliability and safety of the power converter 500.

[0107] Based on this, this application also provides a photovoltaic power generation system, which includes a power converter.

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

[0109] In one possible embodiment, the circuit topology of the photovoltaic power generation system is as follows: Figure 3The circuit topology diagram of the photovoltaic power generation system 400 shown is illustrated. The photovoltaic power generation system 400 includes micro-string inverters 431 to 43k, where k is a positive integer. Each micro-string inverter can be connected 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 terminals of the k micro-string inverters 431 to 43k are connected in parallel via a power line, which includes an AC live wire and an AC neutral wire. This power line is also connected to the power grid or load 300. The micro-string inverters 431 to 43k can also be referred to as power converters, and the circuit topology diagram of any one of the micro-string inverters can be as described above. Figure 4 or Figure 5 The circuit topology diagram of the power converter 500 is shown.

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

[0111] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the 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. The noise signal conditioning circuit includes a first resistor and a capacitor connected in series. The current transformer is connected between the photovoltaic array and the power conversion circuit, and is used to detect the current output by the photovoltaic array. The power conversion circuit is used to convert the DC power output by the photovoltaic array. The current transformer and the sampling signal conditioning circuit are used for DC arc detection. The controller is used to output pulse signals; 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 in order 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 further configured 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 the gain threshold corresponding to the frequency of the pulse signal.

2. The power converter according to claim 1, characterized in that, The controller is further configured 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 configured to output a pulse signal with a frequency that varies in fixed steps during one DC arc detection. The frequency variation in fixed steps includes adjusting the frequency from a first frequency to a second frequency in fixed steps, wherein 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 1-4, characterized in that, The frequency range threshold of the pulse signal is greater than or equal to 20KHz and less than or equal to 60KHz.

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

7. The power converter according to any one of claims 1-6, characterized in that, 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 terminal of the photovoltaic array, and the other end of the first coil is connected to the positive input terminal of the power conversion circuit. One end of the second coil is used to connect to the negative terminal of the photovoltaic array, and the other end of the second coil is connected to the negative input terminal of the power conversion circuit. One end of the third coil is connected to the output terminal 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 terminal, the other end of the fourth coil is connected to the input terminal 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 1-7, characterized in that, The power conversion circuit is a DC-DC power conversion circuit. The output of the power converter is used to connect to the input of the inverter, or the output of the power converter is used to connect in series with the output of at least one power converter and then to the input of the inverter. The output of the inverter is used to connect to the power grid or load.

9. The power converter according to any one of claims 1-7, characterized in that, The power conversion circuit is a DC-AC power conversion circuit, and the output of the power conversion circuit is used to connect to the power grid or load. The controller is specifically configured to control the power conversion circuit to establish a connection with the power grid or 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 a 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. If 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 if 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 load.

10. A control method for a power converter, characterized in that, Applied to a power converter, the method includes: Generate pulse signals; A noise signal is generated based on the pulse signal; A sampling signal is generated based on the noise signal; A conditioning signal is generated based on 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 a 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 includes: If 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 if 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 generated pulse signal includes: In a DC arc detection, a pulse signal is generated whose frequency varies in fixed steps. The frequency variation in fixed steps includes adjusting the frequency from a first frequency to a second frequency in fixed steps, wherein the first frequency is less than the second frequency, or the first frequency is greater than the second frequency.

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