Leakage current detection device and inverter device

Abstract

The utility model relates to a leakage current detection device and an inversion device, the leakage current detection device comprises a pulse signal generation module, a transformer, an energy storage module, a current transformer, a sampling module and a filtering module, a first end of a primary winding of the transformer is connected with the pulse signal generation module, and a second end of the primary winding is grounded through the energy storage module; a first end of a secondary winding of the transformer is connected with a first end of a secondary coil of the current transformer, a second end of the secondary coil is grounded through the sampling module, a second end of the secondary winding is grounded, a magnetic core of the current transformer is sleeved on a power line to be detected, and the filtering module is connected with the second end of the secondary coil. The filtering module can filter out signals whose frequency is greater than or equal to the frequency of the pulse signals, and retains signals induced based on the leakage current, thereby achieving the detection of the leakage current, and facilitating the improvement of the working reliability of the power equipment where the to-be-detected power line is located.

Description

Technical Field

[0001] This application relates to the field of leakage current detection technology, and in particular to a leakage current detection device and an inverter device. Background Technology

[0002] With the development of science and technology, various electrical devices are emerging in large numbers. When these devices are working, leakage current may be generated, affecting their performance and even posing safety hazards.

[0003] Taking grid-connected photovoltaic (PV) inverters as an example, these inverters connect solar photovoltaic panels to the power grid, converting direct current (DC) to alternating current (AC) and feeding the converted AC power into the grid. However, for non-isolated grid-connected PV inverters, due to their non-isolation characteristics, leakage current will occur regardless of the topology or modulation method used, caused by the capacitance between the PV modules and the ground. Excessive leakage current can be harmful to human health, leading to lower reliability of non-isolated grid-connected PV inverters. Therefore, leakage current detection is necessary to prevent excessive leakage current from affecting the reliability of non-isolated grid-connected PV inverters. Utility Model Content

[0004] Therefore, it is necessary to provide a leakage current detection device and inverter that can detect leakage current and has high operational reliability.

[0005] In one aspect, a leakage current detection device is provided, including a pulse signal generation module, a transformer, an energy storage module, a current transformer, a sampling module, and a filtering module;

[0006] The first end of the primary winding of the transformer is connected to the pulse signal generation module, and the second end of the primary winding is grounded through the energy storage module. The first end of the secondary winding of the transformer is connected to the first end of the secondary coil of the current transformer, and the second end of the secondary coil is grounded through the sampling module. The second end of the secondary winding is grounded. The magnetic core of the current transformer is sleeved on the power line to be measured. The filtering module is connected to the second end of the secondary coil and is connected to the pulse signal generation module.

[0007] The pulse signal generation module is used to generate a pulse signal, which is used to bring the current transformer to a critical saturation state. The energy storage module is used for charging and discharging. The current transformer is used to detect the leakage current of the power line under test. The filtering module is used to filter out signals with a frequency greater than or equal to the frequency of the pulse signal.

[0008] Secondly, an inverter device is provided, including an inverter and a leakage current detection device as described above.

[0009] The aforementioned leakage current detection device and inverter include a pulse signal generation module, a transformer, an energy storage module, a current transformer, a sampling module, and a filtering module. The first end of the primary winding of the transformer is connected to the pulse signal generation module, and the second end of the primary winding is grounded through the energy storage module. The first end of the secondary winding of the transformer is connected to the first end of the secondary coil of the current transformer, and the second end of the secondary coil is grounded through the sampling module. The second end of the secondary winding is also grounded. The magnetic core of the current transformer is fitted onto the power line under test. The filtering module is connected to the second end of the secondary coil. The pulse signal generation module is used to generate a pulse signal, which is used to bring the current transformer to a critical saturation state. The energy storage module is used for charging and discharging. The current transformer is used to detect the leakage current of the power line under test. The filtering module is used to filter out signals with a frequency greater than or equal to the frequency of the pulse signal. Therefore, under the action of the pulse signal, the current transformer is in a critical saturation state, the energy storage module is in a charging or discharging state, the secondary winding of the transformer induces electromotive forces of different polarities, the terminal voltage of the secondary coil of the current transformer alternates between positive and negative, and the voltage corresponding to the leakage current of the power line under test is induced. After the sampling module samples the voltage of the secondary coil, the filtering module can filter out signals with a frequency greater than or equal to the frequency of the pulse signal, and retain the signal induced based on the leakage current, thereby realizing the detection of leakage current, which is beneficial to improving the working reliability of the power equipment where the power line under test is located. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the leakage current detection device in one embodiment;

[0012] Figure 2 This is a schematic diagram of the leakage current detection device in another embodiment;

[0013] Figure 3 This is a waveform diagram of the PWM signal in one embodiment;

[0014] Figure 4 This is a schematic diagram of the voltage waveform of the sampling resistor in one embodiment, under PWM and no leakage current conditions.

[0015] Figure 5 This is a schematic diagram of the voltage waveforms of the sampling resistor under PWM and leakage current conditions in one embodiment;

[0016] Figure 6This is a schematic diagram of the voltage waveform of the sampling resistor after low-pass filtering in one embodiment. Detailed Implementation

[0017] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0019] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0020] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0021] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0022] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0023] The leakage current detection device provided in this application embodiment is used to detect the leakage current of a power line under test. Exemplarily, the power line under test can be a power line in a photovoltaic inverter, used to detect the leakage current of the photovoltaic inverter. The photovoltaic inverter can be a grid-connected non-isolated photovoltaic inverter, and the power line under test can specifically be the connection line between the main circuit of the grid-connected non-isolated photovoltaic inverter and the power grid. For example, a grid-connected non-isolated photovoltaic inverter includes photovoltaic modules and an inverter circuit. The photovoltaic modules are connected to the inverter circuit, and the inverter circuit is connected to the power grid; therefore, the power line under test can be the connection line between the inverter circuit and the power grid.

[0024] In one embodiment, such as Figure 1 As shown, the leakage current detection device includes a pulse signal generation module 100, a transformer T1, an energy storage module 200, a current transformer 300, a sampling module 400, and a filtering module 500. The first end of the primary winding of transformer T1 is connected to the pulse signal generation module 100, and the second end of the primary winding is grounded through the energy storage module 200. The first end of the secondary winding of transformer T1 is connected to the first end of the secondary coil of the current transformer 300, and the second end of the secondary coil is grounded through the sampling module 400. The magnetic core of the current transformer 300 is fitted onto the power line under test. The filtering module 500 is connected to the second end of the secondary coil. The pulse signal generation module 100 generates a pulse signal to bring the current transformer 300 to a critical saturation state. The energy storage module 200 is used for charging and discharging. The current transformer 300 is used to detect the leakage current of the power line under test. The filtering module 500 filters out signals with a frequency greater than or equal to the frequency of the pulse signal.

[0025] Specifically, the pulse signal generation module 100 is connected to the first end of the primary winding of transformer T1 to generate pulse signals and transmit them to the primary winding of transformer T1 to control the operation of transformer T1. The structure of the pulse signal generation module 100 is not limited, as long as it can generate pulse signals. The pulse signals include high-level and low-level signals; the primary winding of transformer T1 operates differently when receiving high-level and low-level signals.

[0026] The first end of the primary winding of transformer T1 is connected to a pulse signal generation module 100 for receiving pulse signals. The second end of the primary winding is grounded through an energy storage module 200, which is used for charging or discharging. By configuring transformer T1, the leakage current detection device has an isolation function. The pulse signal includes a high-level signal and a low-level signal. For example, when a high-level signal is received at the first end of the primary winding of transformer T1, the energy storage module 200 charges, and the secondary winding of transformer T1 generates a corresponding induced electromotive force (EMF). The direction of the induced EMF is the same as that of the same-name terminal of transformer T1. When a low-level signal is received at the first end of the primary winding of transformer T1, the energy storage module 200 discharges, and the secondary winding of transformer T1 generates a corresponding induced EMF. The direction of the induced EMF is opposite to the polarity of the induced EMF generated when transformer T1 receives a high-level signal, thereby causing the voltage of the secondary coil of the current transformer 300 connected to the secondary winding of transformer T1 to alternate between positive and negative. The structure of the energy storage module 200 is not limited, as long as it can perform charging and discharging. For example, the energy storage module 200 can be a capacitor C1, which can be charged and discharged quickly, is highly efficient, and is safe and reliable.

[0027] The magnetic core of the current transformer 300 is fitted onto the electric field line under test, meaning the electric field line under test passes through the middle of the magnetic core. The electric field line under test can serve as the primary winding of the current transformer 300. The structure and shape of the magnetic core are not limited; generally, the magnetic core has a closed structure with a through hole in the middle for the electric field line under test to pass through.

[0028] The secondary winding of current transformer 300 is connected to the first terminal of the secondary winding of transformer T1 and the sampling module 400. When leakage current exists on the power line under test, the magnetic core of current transformer 300 can induce the leakage current, causing a corresponding change in the voltage of the secondary winding of current transformer 300. Therefore, the voltage of the secondary winding of current transformer 300 is the result of the combined effect of the induced electromotive force of the secondary winding of transformer T1 and the leakage current induced in the magnetic core.

[0029] Furthermore, the pulse signal generated by the pulse signal generation module 100, after passing through transformer T1, is applied to the current transformer 300, which can bring the current transformer 300 to a critical saturation state. When the current transformer 300 is in a critical saturation state, the magnetic flux density of the current transformer 300 core is close to but has not yet reached the saturation magnetic flux density. The magnetic core of the current transformer 300 can sensitively sense the leakage current in the circuit under test.

[0030] The sampling module 400 is used to sample the voltage of the secondary winding of the current transformer 300, and the sampled voltage is transmitted to the filtering module 500. The structure of the sampling module 400 is not limited, as long as it can achieve signal sampling.

[0031] The filter module 500 is used to filter out signals with a frequency greater than or equal to the frequency of the pulse signal. For example, if the frequency of the pulse signal is high and the frequency of the leakage current is low, the filter module 500 can be a low-pass filter circuit.

[0032] When the leakage current is zero, the voltage signal of the secondary winding of the current transformer 300 has the same or similar frequency as the pulse signal. When transmitted to the filter module 500, the filter module 500 filters out these signals and does not output a signal. When the leakage current is not zero, the voltage signal of the secondary winding of the current transformer 300 includes signals with the same or similar frequency as the pulse signal, as well as signals corresponding to the frequency of the leakage current. After these signals are transmitted to the filter module 500, the filter module 500 filters out the signals with the same or similar frequency as the pulse signal, leaving only the signal corresponding to the frequency of the leakage current, which it then outputs. Therefore, by analyzing the signal output by the filter module 500, the magnitude of the leakage current can be obtained, thus enabling leakage current detection.

[0033] The filter module 500 can also be connected to the pulse signal generation module 100. The pulse signal generation module 100 can analyze the signal output by the filter module 500, and can detect leakage current or obtain other analysis results.

[0034] In this embodiment, the leakage current detection device includes a pulse signal generation module 100, a transformer T1, an energy storage module 200, a current transformer 300, a sampling module 400, and a filtering module 500. The first end of the primary winding of the transformer T1 is connected to the pulse signal generation module 100, and the second end of the primary winding is grounded through the energy storage module 200. The first end of the secondary winding of the transformer T1 is connected to the first end of the secondary coil of the current transformer 300, and the second end of the secondary coil is grounded through the sampling module 400. The second end of the secondary winding is also grounded. The magnetic core of the current transformer 300 is fitted onto the power line under test. The filtering module 500 is connected to the second end of the secondary coil. The pulse signal generation module 100 is used to generate a pulse signal, which is used to bring the current transformer 300 to a critical saturation state. The energy storage module 200 is used for charging and discharging. The current transformer 300 is used to detect the leakage current of the power line under test. The filtering module 500 is used to filter out signals with a frequency greater than or equal to the frequency of the pulse signal. Therefore, under the action of the pulse signal, the current transformer 300 is in a critical saturation state, the energy storage module 200 is in a charging or discharging state, the secondary winding of the transformer T1 induces electromotive forces of different polarities, the terminal voltage of the secondary coil of the current transformer 300 alternates between positive and negative, and the voltage corresponding to the leakage current of the power line under test is induced. After the sampling module 400 samples the voltage of the secondary coil, the filtering module 500 can filter out signals with a frequency greater than or equal to the frequency of the pulse signal, and retain the signal induced based on the leakage current, thereby realizing the detection of leakage current, which is beneficial to improving the working reliability of the power equipment where the power line under test is located.

[0035] In one exemplary embodiment, such as Figure 2 As shown, the pulse signal generation module 100 includes a controller 102, which is connected to the first end of the primary winding of the transformer T1, and the filter module 500 is connected to the controller 102.

[0036] The controller 102 can generate pulse signals and transmit them to the first end of the primary winding of the transformer T1 to control the operating state of the transformer T1. In addition, the controller 102 is also connected to the filter module 500, which can receive the signals output by the filter module 500 and analyze the signals output by the filter module 500 to detect leakage current.

[0037] Expandably, the controller 102 can also be connected to the electrical equipment located on the power line under test to control the operating status of the electrical equipment based on the detected leakage current. For example, when the controller 102 detects that the leakage current exceeds the safety limit, it can control the electrical equipment located on the power line under test to immediately stop working or stop working after a preset time, thereby protecting the electrical equipment. The safety limit can be set according to industry standards or based on actual needs. For example, the safety limit can include three levels: if the leakage current suddenly changes from 0 to 30mA, it switches within 0.3s; if the leakage current suddenly changes from 0 to 60mA, it switches within 0.15s; if the leakage current suddenly changes from 0 to 150mA, it switches within 0.04s.

[0038] In this embodiment, the pulse signal generation module 100 includes a controller 102, which is connected to the first end of the primary winding of the transformer T1, and a filter module 500 is connected to the controller 102. The controller 102 can generate pulse signals and also receive and process signals output by the filter module 500, and can detect the magnitude and changes of leakage current, which helps to improve the accuracy and reliability of leakage current detection.

[0039] In one exemplary embodiment, such as Figure 2 As shown, the pulse signal generation module 100 also includes a driver chip 104, which is connected to the controller 102 and the first end of the primary winding of the transformer T1.

[0040] The controller 102 is connected to the first end of the primary winding of the transformer T1 through the driver chip 104. After the controller 102 outputs a pulse signal, the driver chip 104 can improve the driving capability of the pulse signal, and then transmit the pulse signal with improved driving capability to the first end of the primary winding of the transformer T1, so that the pulse signal can better control the working state of the transformer T1 and the energy storage module 200.

[0041] The driver chip 104 is also used to connect to a power source, and can utilize the connected electrical energy to increase the amplitude and current of the pulse signal, thereby improving the driving capability of the pulse signal. The type of driver chip 104 is not limited; for example, it can be a chip with model number TPM27523 / 4 / 5 / 6, etc.

[0042] In this embodiment, the pulse signal generation module 100 further includes a driver chip 104. The driver chip 104 is connected to the controller 102 and the first end of the primary winding of the transformer T1. The driver chip 104 is also used to connect to a power source. The driver chip 104 can amplify the output capability of the pulse signal output by the controller 102 before transmitting it to the first end of the primary winding of the transformer T1, so that the pulse signal can better control the working state of the transformer T1 and the energy storage module 200, thereby improving the working performance of the leakage current detection device.

[0043] In a scalable embodiment, the leakage current detection device further includes an amplification module, through which the filter module 500 is connected to the controller 102. The amplification module amplifies the signal output by the filter module 500 and transmits the amplified signal to the controller 102, thereby enabling the controller 102 to better detect the output signal of the filter module 500, reducing the occurrence of missed detections, and also lowering the requirements for the sampling sensitivity of the controller 102.

[0044] The structure of the amplification module is not unique. In one exemplary embodiment, the amplification module includes an operational amplifier, the input of which is connected to the filter module 500, and the output of which is connected to the controller 102. The operational amplifier can be either a non-inverting or inverting amplifier, and this is not limited thereto.

[0045] After the signal output by the filter module 500 is connected to the input terminal of the operational amplifier, the received signal is amplified and then transmitted to the controller 102. Specifically, it can be transmitted to the sampling port of the controller 102 so that the controller 102 can better detect the output signal of the filter module 500, reduce the occurrence of missed detections, and also reduce the requirements for the sampling sensitivity of the controller 102.

[0046] In this embodiment, the amplification module includes an operational amplifier. The input of the operational amplifier is connected to the filter module 500, and the output of the operational amplifier is connected to the controller 102. Using an operational amplifier for signal amplification has advantages such as high gain, low offset, high input impedance, and low output impedance.

[0047] The structure of the sampling module 400 is not unique; in one exemplary embodiment, such as... Figure 2 As shown, the sampling module 400 includes a sampling resistor R1. The first end of the sampling resistor R1 is connected to the second end of the filter module 500 and the secondary coil, and the second end of the sampling resistor R1 is grounded.

[0048] The sampling resistor R1 enables the voltage signal on the secondary winding of the current transformer 300 to be transmitted to the filter module 500. When current flows through the secondary winding of the current transformer 300 and the sampling resistor R1 and is grounded, a voltage drop proportional to the current is generated across the sampling resistor R1, realizing the conversion of current and voltage signals and completing the sampling.

[0049] In this embodiment, the sampling module 400 includes a sampling resistor R1. The first end of the sampling resistor R1 is connected to the second end of the filter module 500 and the secondary coil, and the second end of the sampling resistor R1 is grounded. Sampling is performed through the sampling resistor R1, which has high sampling accuracy, simple structure, and wide applicability.

[0050] In one exemplary embodiment, the pulse signal is a PWM (Pulse Width Modulation) signal. A PWM signal is a digital signal consisting of a series of square waves, with only two states: high level and low level, including high-level signals and low-level signals.

[0051] In this embodiment, the pulse signal is a PWM signal. PWM signals are relatively simple to transmit and process, have strong anti-interference capabilities, and the duty cycle of the PWM signal can be adjusted as needed, making them flexible to use.

[0052] In one exemplary embodiment, the switching frequency of the pulse signal is a preset switching frequency, which is determined based on the parameters of the current transformer 300.

[0053] The parameters of the current transformer 300 include, but are not limited to, its structural and performance parameters. The structural parameters of the current transformer 300 may include the cross-sectional area of ​​its magnetic core, the number of turns in its primary winding, and the number of turns in its secondary winding. The performance parameters of the current transformer 300 may include the maximum magnetic flux density of its magnetic core material.

[0054] The preset switching frequency can be determined as follows:

[0055] (1)

[0056] in, To preset the switching frequency, The maximum magnetic flux density of the core material of the 300 current transformer; This is the cross-sectional area of ​​the 300 magnetic core of the current transformer; This refers to the number of turns in the secondary winding of transformer T1. The duty cycle of the high-level pulse signal; This is the voltage on the secondary winding side of transformer T1. The calculation method is as follows:

[0057] (2)

[0058] Wherein, VCC is the voltage on the primary winding side of transformer T1, that is, the power supply voltage connected to the drive chip, and N is the turns ratio of transformer T1. According to the fluxgate principle, when a pulse signal is sent at the preset switching frequency calculated according to formula (1), the pulse signal can make the current transformer 300 be in a critical saturation state.

[0059] In this embodiment, the switching frequency of the pulse signal is a preset switching frequency, which is determined based on the parameters of the current transformer 300. This pulse signal can bring the current transformer 300 to a critical saturation state, thereby enabling more sensitive and accurate detection of leakage current on the power line under test.

[0060] The shape of the magnetic core of the current transformer 300 is not unique. In one exemplary embodiment, the magnetic core is a toroidal core. The toroidal core is fitted onto the electric field line under test, with the electric field line passing through the hollow portion of the toroidal core. Furthermore, the electric field line under test can pass through the geometric center of the toroidal core, ensuring that the distance between the toroidal core and the electric field line under test is approximately equal at all points, which helps improve the accuracy of leakage current detection. It is understood that in other embodiments, the shape of the magnetic core can also be other, such as a rectangular core, as long as those skilled in the art deem it feasible.

[0061] In this embodiment, the magnetic core is a toroidal core. The toroidal core helps improve the measurement accuracy and stability of the current transformer 300, meeting various complex measurement requirements. The toroidal core current transformer 300 features a fast response speed, rapidly responding to current changes. Furthermore, the toroidal core is small in size and lightweight, facilitating installation and maintenance. The toroidal core also exhibits high linearity, providing more accurate measurement results.

[0062] To better understand the above embodiments, a detailed explanation is provided below with reference to a specific embodiment. In one embodiment, as follows... Figure 2 As shown, the leakage current detection device includes a pulse signal generation module 100, a transformer T1, an energy storage module 200, a current transformer 300, a sampling module 400, a filtering module 500, and an amplification circuit. The current transformer 300 includes a magnetic core (material can be an alloy), a primary winding (the power line to be measured), and a secondary winding. The pulse signal is a PWM signal, such as... Figure 3As shown. The pulse signal generation module 100 includes a controller 102 and a driver chip 104. The controller 102 can be an MCU, and the driver chip 104 is a chip that amplifies the PWM output capability, such as TPM27523 / 4 / 5 / 6. The energy storage module 200 includes a capacitor C1, the sampling module 400 includes a sampling resistor R1, the filtering module 500 is a low-pass filter circuit, and the amplification circuit includes an operational amplifier.

[0063] The MCU sends a PWM waveform according to a pre-set switching frequency, which is calculated as follows:

[0064] (1)

[0065] in, To preset the switching frequency, The maximum magnetic flux density of the core material of the 300 current transformer; This is the cross-sectional area of ​​the 300 magnetic core of the current transformer; This refers to the number of turns in the secondary winding of transformer T1. The duty cycle of the high-level pulse signal; This is the voltage on the secondary winding side of transformer T1. The calculation method is as follows:

[0066] (2)

[0067] Where VCC is the voltage on the primary winding side of transformer T1, and N is the turns ratio of transformer T1. According to the fluxgate principle, when a pulse signal is sent at the preset switching frequency calculated according to equation (1), the pulse signal can make the current transformer 300 be in a critical saturation state.

[0068] The working process of the leakage current detection device includes:

[0069] 1. The MCU sends a PWM signal according to the preset switching frequency. When the level in the PWM signal is high, capacitor C1 is charged and the secondary winding of transformer T1 generates a corresponding induced electromotive force. The direction of the electromotive force is the same as that of the same terminal of transformer T1.

[0070] 2. When the PWM signal is at a low level, capacitor C1 discharges, and the secondary winding of transformer T1 generates a corresponding induced electromotive force. The polarity of the electromotive force is opposite to that generated when the PWM is at a high level, thus causing the terminal voltage of the secondary coil of current transformer 300 to alternate between positive and negative.

[0071] 3. When the leakage current flowing through the primary winding (i.e., the power line under test) of the current transformer 300 is 0, if Figure 4As shown, the voltage across the sampling resistor R1 is a high-frequency signal with alternating positive and negative values. After passing through the low-pass filter circuit, the output voltage is basically 0.

[0072] 4. When the leakage current flowing through the primary winding (i.e., the power line under test) of the current transformer 300 is not zero, such as Figure 5 As shown, assuming the flow direction is positive, after low-pass filtering, the low-pass filter circuit filters out the high-frequency voltage signal generated by the PWM on the current transformer 300, as follows: Figure 6 As shown, low-frequency leakage current enters the sampling port of the MCU, which can detect the leakage current and determine whether it exceeds safety limits. If the leakage current exceeds safety limits, the MCU can immediately stop operating the photovoltaic inverter, or stop operating after a preset time, to avoid further adverse consequences.

[0073] The leakage current detection device provided in this application embodiment does not require the self-excited circuit required by other schemes, resulting in high reliability. Furthermore, it uses fewer components, further improving reliability. The MCU can also control whether the current sensor operates, which helps reduce the loss of the current sensor. In addition, the leakage current detection device also includes a transformer T1, providing isolation functionality.

[0074] This application also provides an inverter device, including an inverter and a leakage current detection device as described in any of the above embodiments. The photovoltaic inverter can be a grid-connected non-isolated photovoltaic inverter, and the power line under test can specifically be the connection line between the main circuit of the grid-connected non-isolated photovoltaic inverter and the power grid. For example, the grid-connected non-isolated photovoltaic inverter includes photovoltaic modules and an inverter circuit. The photovoltaic modules are connected to the inverter circuit, and the inverter circuit is connected to the power grid. In this case, the power line under test can be the connection line between the inverter circuit and the power grid.

[0075] In the aforementioned inverter device, under the action of a pulse signal, the current transformer is in a critical saturation state, the energy storage module is in a charging or discharging state, and the secondary winding of the transformer induces electromotive forces of different polarities. The terminal voltage of the secondary coil of the current transformer alternates between positive and negative, and the voltage corresponding to the leakage current of the power line under test is induced. After the sampling module samples the voltage of the secondary coil, the filtering module can filter out signals with a frequency greater than or equal to the frequency of the pulse signal, and retain the signal induced based on the leakage current, thereby realizing the detection of leakage current, which is beneficial to improving the working reliability of the photovoltaic inverter.

[0076] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0077] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A leakage current detection device, characterized in that, It includes a pulse signal generation module, a transformer, an energy storage module, a current transformer, a sampling module, and a filtering module; The first end of the primary winding of the transformer is connected to the pulse signal generation module, and the second end of the primary winding is grounded through the energy storage module. The first end of the secondary winding of the transformer is connected to the first end of the secondary coil of the current transformer, and the second end of the secondary coil is grounded through the sampling module. The second end of the secondary winding is grounded. The magnetic core of the current transformer is sleeved on the power line to be measured. The filtering module is connected to the second end of the secondary coil and is connected to the pulse signal generation module. The pulse signal generation module is used to generate a pulse signal, which is used to bring the current transformer to a critical saturation state. The energy storage module is used for charging and discharging. The current transformer is used to detect the leakage current of the power line under test. The filtering module is used to filter out signals with a frequency greater than or equal to the frequency of the pulse signal.

2. The leakage current detection device according to claim 1, characterized in that, The pulse signal generation module includes a controller, which is connected to the first end of the primary winding of the transformer, and the filtering module is connected to the controller.

3. The leakage current detection device according to claim 2, characterized in that, The pulse signal generation module also includes a driver chip, which is connected to the controller and the first end of the primary winding of the transformer.

4. The leakage current detection device according to claim 2, characterized in that, It also includes an amplification module, and the filtering module is connected to the controller through the amplification module.

5. The leakage current detection device according to claim 4, characterized in that, The amplification module includes an operational amplifier, the input of which is connected to the filtering module, and the output of which is connected to the controller.

6. The leakage current detection device according to claim 1, characterized in that, The sampling module includes a sampling resistor, the first end of which is connected to the filtering module and the second end of the secondary coil, and the second end of the sampling resistor is grounded.

7. The leakage current detection device according to claim 1, characterized in that, The pulse signal is a PWM signal.

8. The leakage current detection device according to claim 1, characterized in that, The switching frequency of the pulse signal is a preset switching frequency, which is determined based on the parameters of the current transformer.

9. The leakage current detection device according to claim 1, characterized in that, The magnetic core is a toroidal core.

10. An inverter device, characterized in that, It includes an inverter and a leakage current detection device as described in any one of claims 1-9.

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