Leakage current detection device and method, frequency converter and energy storage converter

Abstract

The invention discloses a leakage current detection device and method, a frequency converter and an energy storage converter, and the device comprises a self-detection unit which enables the leakage current detection device to carry out detection; the oscillation unit is used for generating an oscillation signal on a secondary winding of the leakage current detection mutual inductor so as to reflect the oscillation signal to a primary winding to become a carrier signal of leakage current, and then transmitting the carrier signal to the secondary winding to obtain a leakage current sampling signal; the filtering unit is used for filtering the leakage current sampling signal to obtain a leakage current filtering signal; the protection unit performs protection based on the leakage current sampling signal to obtain a protection signal; the conditioning unit is used for conditioning based on the leakage current filtering signal and the protection signal to obtain a leakage current detection signal; and the control unit is used for controlling the power grid side converter based on the leakage current detection signal so as to realize leakage current protection of the power grid side converter. According to the scheme, when the leakage current on the ground wire of the power grid side converter or the power line connected with the power grid side is detected, self-inspection and protection are achieved, and safety is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of leakage current detection, and specifically relates to a leakage current detection device, method, inverter and energy storage converter, and more particularly to a leakage current detection and self-checking circuit, method, inverter and energy storage converter. Background Art

[0002] When leakage current occurs in the grid-side converter (such as a frequency converter, energy storage converter, etc.), a self-check of the leakage current is required to ensure the safety of the converter when it is powered on. However, in related solutions, there are safety hazards when the grid-side converter does not have a self-check function.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The object of the present invention is to provide a leakage current detection device, method, frequency converter and energy storage converter to solve the problem of potential safety hazards when the grid-side converter does not have a self-detection function in related schemes, so as to achieve the effect of improving safety by realizing self-detection and protection while detecting the leakage current on the ground wire of the grid-side converter or the power line connected to the grid.

[0005] The present invention provides a leakage current detection device, which is used to detect the leakage current of a grid-side converter from the grid side; the leakage current detection device includes: a leakage current detection mutual inductor, a self-checking unit, a filtering unit, an oscillating unit, a protection unit, a conditioning unit, and a control unit; the primary winding of the leakage current detection mutual inductor has a first winding, a second winding, a third winding, a fourth winding and a fifth winding, and the first winding, the second winding, the third winding and the fourth winding are respectively connected in series to the three-phase four-wire alternating current line on the grid side; the fifth winding is connected to the self-checking unit; the secondary winding of the leakage current detection mutual inductor is respectively connected to the oscillating unit and the protection unit; the filtering unit is connected to the oscillating unit, and the conditioning unit is respectively connected to the filtering unit and the protection unit; wherein the self-checking unit is used to generate a constant current based on a trigger signal input from a preset trigger pin; the constant current generates a self-checking signal through the fifth winding current, so that the leakage current detection device performs detection based on the self-test current to determine whether the leakage current detection device is in a preset working state; the oscillation unit is used to generate an oscillation signal on the secondary winding to reflect the leakage current to the primary winding to become a carrier signal of the leakage current, and then transmit it to the secondary winding to obtain a leakage current sampling signal when the leakage current detection device is in a preset working state; the filtering unit is used to filter the leakage current sampling signal to obtain a leakage current filtering signal; the protection unit is used to perform protection based on the leakage current sampling signal to obtain a protection signal; the conditioning unit is used to perform conditioning based on the leakage current filtering signal and the protection signal to obtain a conditioning signal as a leakage current detection signal obtained by detecting the leakage current of the grid-side converter from the grid side; the control unit is used to control the grid-side converter based on the leakage current detection signal to achieve leakage current protection for the grid-side converter.

[0006] In some embodiments, the self-test unit includes: a first current limiting resistor module, a second current limiting resistor module, a first switch tube module, a voltage regulator diode module, and a protection module for the fifth winding; wherein a preset first DC power supply is connected to the same-name end of the fifth winding after passing through the protection module of the fifth winding; the opposite-name end of the fifth winding is connected to the first connection end of the first switch tube module; a preset input trigger pin is connected to the control end of the first switch tube module after passing through the first current limiting resistor module; the second connection end of the first switch tube module is grounded after passing through the second current limiting resistor module; the preset input trigger pin is also connected to the cathode of the voltage regulator diode module; the anode of the voltage regulator diode module is grounded; the control end of the voltage regulator diode module is connected to the second connection end of the first switch tube module.

[0007] In some embodiments, the oscillation unit includes: an oscillation module and a sampling resistor module; wherein the secondary winding is connected to the oscillation module to form a self-excited oscillator; the same-name end of the secondary winding is connected to the first connection end of the sampling resistor module; the second connection end of the sampling resistor module is connected to the oscillation module and grounded; the first connection end of the sampling resistor module is also connected to the filtering unit; and the oscillation module is also connected to the protection unit.

[0008] In some embodiments, the oscillation module includes: a timing module, a first operational amplifier module, a second switch tube module, and a third open tube module; wherein the same-name end of the secondary winding is connected to the ground pin of the timing module after passing through the sampling resistor module; the same-name end of the secondary winding and the common end of the sampling resistor module are respectively connected to the discharge pin of the timing module and the threshold pin of the timing module; the same-name end of the secondary winding and the common end of the sampling resistor module are connected to the input end of the filtering unit as the output end of the oscillation unit; the opposite-name end of the secondary winding is connected to the trigger pin of the timing module; the output pin of the timing module can be connected connected to the non-inverting input terminal of the first operational amplifier module; the inverting input terminal of the first operational amplifier module is used to receive a preset reference voltage signal; the output terminal of the first operational amplifier module is respectively connected to the control terminal of the second switch tube module and the control terminal of the third switch tube module; a preset second DC power supply is connected to the first connection terminal of the second switch tube module; the second connection terminal of the second switch tube module is connected to the first connection terminal of the third switch tube module; a preset third DC power supply is connected to the second connection terminal of the third switch tube module; the second connection terminal of the second switch tube module is also respectively connected to the opposite-name terminal of the secondary winding and the input terminal of the protection unit.

[0009] In some embodiments, the filtering unit includes: a second operational amplifier module, a two-stage RC filtering module, and a third operational amplifier module; wherein the output end of the leakage current sampling signal of the oscillation unit can be connected to the non-inverting input end of the second operational amplifier module; the inverting input end of the second operational amplifier module is connected to the output end of the second operational amplifier module; the output end of the second operational amplifier module can be connected to the non-inverting input end of the third operational amplifier module after passing through the two-stage RC filtering module; the inverting input end of the third operational amplifier module is connected to the output end of the third operational amplifier module; the output end of the third operational amplifier module is connected to the input end of the conditioning unit.

[0010] In some embodiments, the protection unit includes: a first capacitor module, a second capacitor module, a diode module, a discharge resistor module, a fourth switch tube module, a third current limiting resistor module, and a fourth current limiting resistor module; wherein, the opposite end of the secondary winding is connected to the anode of the diode module after passing through the first capacitor module; the anode of the diode module and the cathode of the diode module are grounded after passing through the discharge resistor module respectively; the cathode of the diode module is connected to the control end of the fourth switch tube after passing through the third current limiting resistor module and the fourth current limiting resistor module; a preset fourth DC power supply can be connected to the first connection end of the fourth switch tube; the first connection end of the fourth switch tube, as the output end of the protection unit, is also connected to the input end of the conditioning unit; the second connection end of the fourth switch tube is grounded.

[0011] In some embodiments, the conditioning unit includes: a fifth current limiting resistor module, a sixth current limiting resistor module, an RC setting module, a fourth op amp module, and a seventh current limiting resistor module; wherein the output end of the filtering unit and the output end of the protection unit are connected to the inverting input end of the fourth op amp module after passing through the fifth current limiting resistor module; a preset fifth DC power supply can be connected to the inverting input end of the fourth op amp module; the non-inverting input end of the fourth op amp module is connected to the output end of the fourth op amp module after passing through the RC setting module; the output end of the fourth op amp module can be connected to the sampling end of the control unit after passing through the seventh current limiting resistor module to output the leakage current detection signal to the control unit.

[0012] Matching the above device, the present invention further provides a frequency converter, including: the leakage current detection device mentioned above.

[0013] Matching the above device, the present invention further provides an energy storage converter, including: the leakage current detection device described above.

[0014] Matching the above-mentioned device, the present invention provides a leakage current detection method on another aspect, comprising: generating a constant current based on a trigger signal input from a preset trigger pin through the self-test unit; the constant current generates a self-test current through the fifth winding, so that the leakage current detection device performs detection based on the self-test current to determine whether the leakage current detection device is in a preset working state; generating an oscillation signal on the secondary winding through the oscillation unit to reflect the leakage current to the primary winding to become a carrier signal of the leakage current, and then transmitting it to the secondary winding to obtain a leakage current sampling signal when the leakage current detection device is in a preset working state; filtering the leakage current sampling signal through the filtering unit to obtain a leakage current filtering signal; performing protection based on the leakage current sampling signal through the protection unit to obtain a protection signal; performing conditioning based on the leakage current filtering signal and the protection signal through the conditioning unit to obtain a conditioning signal as a leakage current detection signal obtained by detecting the leakage current of the grid-side converter from the grid side; controlling the grid-side converter based on the leakage current detection signal to achieve leakage current protection of the grid-side converter.

[0015] In some embodiments, the grid-side converter is controlled based on the leakage current detection signal to implement leakage current protection for the grid-side converter, including: determining whether the current value corresponding to the leakage current detection signal is less than a preset first current value and the duration is less than a preset first time; if it is determined to be satisfied, determining the sudden residual current of the grid-side converter according to the leakage current detection signal; if it is determined that the sudden residual current of the grid-side converter is greater than or equal to a preset second current value, or if it is determined that the sudden residual current of the grid-side converter is less than the preset second current value but greater than or equal to a preset third current value and the duration is less than a preset second time, or if it is determined that the sudden residual current of the grid-side converter is less than the preset second current value but greater than or equal to a preset third current value and the duration is less than a preset second time, If the residual current is less than the preset third current value but greater than or equal to the preset fourth current value and the duration is less than the preset first time, a reminder message is initiated that the grid-side converter has a leakage current fault; until the grid-side converter is shut down for protection, it is determined whether the current value corresponding to the leakage current detection signal is less than the preset fifth current value and the duration reaches the preset third time: if so, the reminder message is cleared and the grid-side converter is restarted, otherwise, the reminder message of the grid-side converter having a leakage current fault continues to be initiated; wherein, the preset fifth current value is greater than the preset fourth current value and less than the preset third current value, and the preset first time is greater than the preset second time and less than the preset third time.

[0016] Therefore, the scheme of the present invention is to set a leakage current detection transformer, a self-detection unit (such as a self-detection circuit), a filtering unit (such as a low-pass filtering circuit), an oscillation unit (such as an oscillation circuit), a protection unit (such as a differential protection circuit), a conditioning unit (such as a sampling conditioning circuit), and a control unit (such as an MCU) on the grid side of the grid-side converter, wherein: the first winding, the second winding, the third winding, and the fourth winding in the primary winding of the leakage current detection transformer are connected between the grid side and the converter, and the fifth winding in the primary winding of the leakage current detection transformer is connected to the self-detection unit, and the self-detection unit is used to generate a current of a certain value, so that the detection circuit composed of the filtering unit, the oscillation unit, the protection unit, and the conditioning unit performs detection based on the current of the certain value. The detection circuit is measured to determine whether it is in a normal working state; the oscillation unit generates an oscillation signal on the secondary winding to reflect it to the primary winding to become a carrier signal of the leakage current, and then transmits it to the secondary winding to obtain a leakage current sampling signal; the filtering unit filters the leakage current sampling signal output by the oscillation unit, the protection unit controls the conditioning unit according to the oscillation signal generated by the oscillation unit, and the conditioning unit conditions the signal filtered by the filtering unit and the protection signal of the protection unit to output the leakage current detection signal to the control unit, so that the control unit processes based on the leakage current detection signal; thereby, by detecting the leakage current on the ground wire of the grid-side converter or the power line connected to the grid side, self-detection and protection can be achieved to improve safety.

[0017] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of an embodiment of a leakage current detection device of the present invention;

[0020] Figure 2 It is a structural schematic diagram of the main circuit where the leakage current detection and self-test circuit of the present invention is located;

[0021] Figure 3 It is a schematic diagram of the flow of the leakage current detection and self-test method of the present invention;

[0022] Figure 4 A schematic diagram of a flow chart of an embodiment of a leakage current detection method of the present invention;

[0023] Figure 5 The present invention is a flowchart of an embodiment of controlling the grid-side converter based on the leakage current detection signal in the method of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Considering that in the relevant schemes, there are safety hazards when the grid-side converter does not have a self-test function. Generally, only type B leakage current sensors have a self-test function, and some leakage current sensors in the relevant schemes do not have a self-test function; when there is no self-test function, the correctness of the test results cannot be guaranteed, and the normal operation of the equipment cannot be guaranteed. For example: some schemes provide a multi-speed automatic adjustment type B residual current detection protection method and circuit, but this detection method does not have a corresponding residual current self-test circuit, and cannot guarantee the accuracy of the detection results and the safety of the system when the detection circuit fails. Leakage detection requires a self-test circuit to ensure the accuracy of the test results and the safety of the system when power is turned on. The self-test process is similar to the calibration of a measuring device.

[0026] Some other solutions provide a leakage current detection circuit and an inverter, but this detection method does not have a corresponding self-test circuit, and the measurement range of the leakage current is limited and cannot cover inverters of other power ranges.

[0027] Some other solutions provide a photovoltaic inverter leakage current detection device. This detection method can detect leakage current well and has a self-test circuit, but lacks a corresponding protection circuit, and a large short-circuit current will damage the sampling circuit.

[0028] Therefore, the solution of the present invention proposes a leakage current detection device, specifically a leakage current detection and self-test circuit, which can identify the size of short-circuit current and leakage current by detecting the leakage current on the ground wire of the grid-side converter or the power line connected to the grid side; and, while detecting the leakage current, it has a self-test circuit and a protection circuit to ensure the integrity of the current detection function and improve safety.

[0029] According to an embodiment of the present invention, a leakage current detection device is provided. Figure 1 The leakage current detection device is used to detect the leakage current of the grid-side converter from the grid side; in the scheme of the present invention, Figure 1 As shown, the leakage current detection device includes: a leakage current detection transformer (such as Figure 2 Current transformer T1 shown), self-test unit (such as Figure 2The self-test circuit shown), the filter unit (such as Figure 2 The low-pass filter circuit shown), the oscillation unit (such as Figure 2 Oscillation circuit shown), protection unit (such as Figure 2 Differential protection circuit shown), conditioning unit (such as Figure 2 The sampling and conditioning circuit shown in FIG. Figure 2 MCU shown); the primary winding of the leakage current detection transformer has a first winding, a second winding, a third winding, a fourth winding and a fifth winding, and the first winding, the second winding, the third winding and the fourth winding are correspondingly connected in series with the three-phase four-wire AC power line on the grid side; the fifth winding is connected to the self-test unit; the secondary winding of the leakage current detection transformer is respectively connected to the oscillation unit and the protection unit; the filter unit is connected to the oscillation unit, and the conditioning unit is respectively connected to the filter unit and the protection unit.

[0030] Among them, the self-test unit is used to generate a constant current based on a trigger signal (such as a 3.3V~5V high-level voltage) input from a preset trigger pin; the constant current generates a self-test current through the fifth winding, so that the leakage current detection device performs detection based on the self-test current to determine whether the leakage current detection device is in a preset working state (such as a normal working state), thereby realizing self-test of the leakage current detection device.

[0031] The oscillation unit is used to generate an oscillation signal on the secondary winding when the leakage current detection device is in a preset working state, so as to reflect the oscillation signal to the primary winding to become a carrier signal of the leakage current, and then transmit the oscillation signal to the secondary winding to obtain a leakage current sampling signal.

[0032] The filtering unit is used to filter the leakage current sampling signal to obtain a leakage current filtering signal.

[0033] The protection unit is used to perform protection based on the leakage current sampling signal to obtain a protection signal.

[0034] The conditioning unit is used to perform conditioning based on the leakage current filter signal and the protection signal to obtain a conditioned signal as a leakage current detection signal obtained by detecting the leakage current of the grid-side converter from the grid side.

[0035] The control unit is used to control the grid-side converter based on the leakage current detection signal to achieve leakage current protection for the grid-side converter.

[0036] Figure 2 FIG. 1 is a schematic diagram of the structure of the main circuit of the leakage current detection and self-test circuit of the present invention. Figure 2As shown, the main circuit where the leakage current detection and self-test circuit is located has a current transformer T1 as a leakage current detection transformer. The leakage current detection and self-test circuit includes: a self-test circuit, a low-pass filter circuit, a sampling and conditioning circuit, an oscillation circuit, and a differential protection circuit. The self-test circuit is connected to the primary winding of the current transformer T1, the low-pass filter circuit, the oscillation circuit, and the differential protection circuit are all connected to the secondary winding of the current transformer T1, and the sampling and conditioning circuit is connected to the low-pass filter circuit.

[0037] exist Figure 2 In the example shown, the primary winding of the current transformer T1 includes: a first winding, a second winding, a third winding, a fourth winding and a fifth winding. The first winding in the primary winding of the current transformer T1 is connected in series with the A line of the three-phase current input terminal on the grid side. Specifically, the same-name end of the first winding in the primary winding of the current transformer T1 is connected to the A line of the three-phase current input terminal on the grid side, and the opposite-name end of the first winding in the primary winding of the current transformer T1 is connected to the rear end of the A line (such as the part connected to the A line in the grid side converter); the second winding in the primary winding of the current transformer T1 is connected in series with the B line of the three-phase current input terminal on the grid side. Specifically, the same-name end of the second winding in the primary winding of the current transformer T1 is connected to the B line of the three-phase current input terminal on the grid side, and the opposite-name end of the second winding in the primary winding of the current transformer T1 is connected to the rear end of the B line (such as the part connected to the B line in the grid side converter); the primary winding of the current transformer T1 The third winding in the primary winding of the current transformer T1 is connected in series with the C line of the three-phase current input terminal on the grid side, specifically, the same-name end of the third winding in the primary winding of the current transformer T1 is connected to the C line of the three-phase current input terminal on the grid side, and the opposite-name end of the third winding in the primary winding of the current transformer T1 is connected to the rear end of the C line (such as the part connected to the C line in the grid side converter); the fourth winding in the primary winding of the current transformer T1 is connected in series with the N line of the three-phase current input terminal on the grid side, specifically, the same-name end of the fourth winding in the primary winding of the current transformer T1 is connected to the N line of the three-phase current input terminal on the grid side, and the opposite-name end of the fourth winding in the primary winding of the current transformer T1 is connected to the rear end of the N line (such as the part connected to the N line in the grid side converter); the fifth winding in the primary winding of the current transformer T1 is connected to the self-test circuit.

[0038] The scheme of the present invention proposes a leakage current detection and self-checking circuit. For the grid-side converter, by detecting the leakage current on the ground wire or the power line connected to the grid side, it can identify the magnitude of the short-circuit current and the leakage current, and solve the problem that the wire diameter of the three-phase incoming cable is too thick to pass through the leakage current detection device; and the scheme of the present invention, while detecting the leakage current, has a self-checking circuit and a protection circuit to ensure the integrity of the current detection function and improve safety.

[0039] Among them, leakage current is the current between the power line and the earth. There are two wiring methods for detection. One is to connect all the power lines on the grid side to the transformer, that is, corresponding to A, B, C, N; the other is to only connect the ground wire to one of the phases A, B, C, N.

[0040] In some embodiments, the self-test unit includes: a first current limiting resistor module (such as Figure 2 The resistor R1 shown in FIG. 1 ), the second current limiting resistor module (such as Figure 2 The resistor R2 shown in FIG. 1 ), the first switch tube module (such as Figure 2 The transistor Q1 shown), the voltage regulator diode module (such as Figure 2 The voltage stabilizing diode D1 shown in FIG. 1 ), and the protection module of the fifth winding (such as Figure 2 Resistor R0, diode D11 and diode D12 are shown).

[0041] Among them, the preset first DC power supply (such as a 5V DC power supply) is connected to the same-name end of the fifth winding after passing through the protection module of the fifth winding; the opposite-name end of the fifth winding is connected to the first connection end of the first switch tube module (such as the collector of the transistor Q1). The preset input trigger pin (such as the input pin of the 3.3V~5V DC power supply) is connected to the control end of the first switch tube module (such as the base of the transistor Q1) after passing through the first current limiting resistor module; the second connection end of the first switch tube module (such as the emitter of the transistor Q1) is grounded after passing through the second current limiting resistor module. The preset input trigger pin (such as the input pin of the 3.3V~5V DC power supply) is also connected to the cathode of the Zener diode module; the anode of the Zener diode module is grounded; the control end of the Zener diode module is connected to the second connection end of the first switch tube module (such as the emitter of the transistor Q1).

[0042] exist Figure 2 In the example shown, the self-test circuit includes: resistor R0, resistor R1, resistor R2, diode D11, diode D12, voltage-stabilizing diode D1, and transistor Q1. Resistor R0 is a current-limiting resistor to prevent excessive current in the loop from damaging the device; diodes D11 and D12 are used to protect the circuit. When a large current flows through the self-test coil (i.e., the fifth winding), a high voltage will be generated at both ends of the self-test coil. Diodes D11 and D12 play a role in limiting the high voltage in the circuit.

[0043] Among them, the 5V DC power supply is connected to the same-name end of the fifth winding in the primary winding of the current transformer T1 after passing through the resistor R0. The same-name end of the fifth winding in the primary winding of the current transformer T1 is also connected to the cathode of the diode D11; the anode of the diode D11 is grounded. The 5V DC power supply is connected to the cathode of the diode D12; the anode of the diode D12 is connected to the cathode of the diode D11. The opposite-name end of the fifth winding in the primary winding of the current transformer T1 is connected to the collector of the transistor Q1. The 3.3V~5V DC power supply is connected to the base of the transistor Q1 after passing through the resistor R1. The emitter of the transistor Q1 is grounded after passing through the resistor R2. The 3.3V~5V DC power supply is also connected to the cathode of the voltage-stabilizing diode D1; the anode of the voltage-stabilizing diode D1 is grounded; the control end of the voltage-stabilizing diode D1 is connected to the emitter of the transistor Q1.

[0044] exist Figure 2 In the leakage current detection and self-test circuit shown in FIG. 1 , the self-test circuit inputs a 3.3V to 5V high level voltage through the input trigger pin (i.e., the 3.3V to 5V voltage input pin), which will generate a constant current IT in the branch. The constant current IT directly passes through the leakage current detection transformer (such as Figure 2 The fifth winding in the primary winding of the current transformer T1) shown in FIG. generates a self-test current. Figure 2 When the trigger pin input is 3.3V~5V, the diode D1 makes the voltage on the resistor R2 2.5V. The current of the self-test coil can be obtained by dividing the voltage of 2.5V by the resistance value of the resistor R2. When the input trigger pin voltage is less than 0.2V or is open-circuited, the branch does not generate current and exits the self-test. The self-test circuit generates a certain value of current, and the detection circuit detects this current. By comparing the detection results of the detection circuit, it is determined whether the detection circuit is in a normal working state. When it is determined that the detection circuit is in a normal working state, the detection circuit is used to perform leakage current detection, which can improve safety. Figure 2 The resistance value of R2 in the circuit is fixed, so the self-test current is also fixed. The test result can be compared with the given value of the program to know whether the test result is correct. For example: the resistance value of resistor R2 is 1kΩ, 2.5V / 1kΩ=2.5mA. The given value of the program is 2.5mA. By comparing the value returned by the test with the given value of 2.5mA, we can know whether the circuit is normal.

[0045] In some embodiments, the oscillation unit includes: an oscillation module (such as Figure 2 555 timer and its peripheral circuit shown in the figure), sampling resistor module (such as Figure 2 Resistor R6 shown).

[0046] The secondary winding is connected to the oscillation module to form a self-excited oscillator; the same-name end of the secondary winding is connected to the first connection end of the sampling resistor module; the second connection end of the sampling resistor module is connected to the oscillation module and grounded; the first connection end of the sampling resistor module is also connected to the filter unit; and the oscillation module is also connected to the protection unit.

[0047] In the solution of the present invention, when leakage current occurs in the grid-side converter (such as a frequency converter, an energy storage converter, etc.), an oscillating circuit constructed by a 555 timer is connected to the leakage current detection transformer (such as Figure 2 A high-frequency oscillation signal is generated on the secondary winding of the current transformer T1 shown in FIG. 1 , and is reflected to the leakage current detection transformer (such as Figure 2 The primary winding of the current transformer T1 shown in FIG. 1 is used as a carrier signal of the low-frequency leakage current, and the low-frequency leakage current is transmitted to the leakage current detection transformer (such as Figure 2 The secondary side of the current transformer T1 shown in the figure can obtain a low-frequency leakage current signal after filtering out the high-frequency oscillation signal through a low-pass filter, and then send it to the AD sampling channel of the controller MCU after passing through the sampling and conditioning circuit. Then the software implements the corresponding calculation, logic judgment and protection functions to improve safety.

[0048] In some embodiments, the oscillation module includes: a timing module (such as Figure 2 555 timer shown), the first op amp module (such as Figure 2 The operational amplifier U1 shown in FIG. Figure 2 The transistor Q2 shown), and the third open tube module (such as Figure 2 Transistor Q3 shown).

[0049] Among them, the same-name end of the secondary winding is connected to the ground pin of the timing module after passing through the sampling resistor module; the same-name end of the secondary winding and the common end of the sampling resistor module are respectively connected to the discharge pin of the timing module and the threshold pin of the timing module; the same-name end of the secondary winding and the common end of the sampling resistor module are connected to the input end of the filtering unit as the output end of the oscillation unit. The opposite-name end of the secondary winding is connected to the trigger pin of the timing module; the output pin of the timing module can be connected to the same-phase input end of the first operational amplifier module; the inverting input end of the first operational amplifier module is used to receive a preset reference voltage signal; the output end of the first operational amplifier module is respectively connected to the control end of the second switch tube module (such as the base of the transistor Q2), and the control end of the third switch tube module (such as the base of the transistor Q3). A preset second DC power supply (such as a 12V DC power supply) is connected to the first connection end of the second switch tube module (such as the collector of the transistor Q2); the second connection end of the second switch tube module (such as the emitter of the transistor Q2) is connected to the first connection end of the third switch tube module (such as the emitter of the transistor Q3); a preset third DC power supply (such as a -12V DC power supply) is connected to the second connection end of the third switch tube module (such as the collector of the transistor Q3); the second connection end of the second switch tube module (such as the emitter of the transistor Q2) is also respectively connected to the opposite end of the secondary winding and the input end of the protection unit.

[0050] exist Figure 2In the example shown, the oscillation circuit includes: resistors R3, R4, R5, R6, capacitor C1, transistors Q2, Q3, 555 timer, and operational amplifier U1. Among them, the same-name end of the secondary winding of the current transformer T1 is grounded after passing through the resistor R6; the 12V power supply is grounded after passing through the capacitor C1, the ground pin (such as the GND pin) of the 555 timer is grounded, and the power pin (such as the V+ pin) of the 555 timer is connected to the 12V power supply; the same-name end of the secondary winding of the current transformer T1 is connected to the discharge pin (such as the DS pin) of the 555 timer and the threshold pin (such as the THR pin) of the 555 timer; the opposite-name end of the secondary winding of the current transformer T1 is connected to the trigger pin (such as the TR pin) of the 555 timer; the reset pin (such as the RS pin) of the 555 timer is connected to the 12V power supply, and the CV pin of the 555 timer is grounded. The output pin (such as the O pin) of the 555 timer is connected to the non-inverting input terminal of the operational amplifier U1 through the resistor R3; the inverting input terminal of the operational amplifier U1 is grounded through the resistor R4; the power terminal of the operational amplifier U1 is connected to the 12V power supply, the ground terminal of the operational amplifier U1 is connected to the -12V power supply, and the ground terminal of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U1 through the resistor R5. The output terminal of the operational amplifier U1 is connected to the base of the transistor Q2 and the base of the transistor Q3 respectively. The 12V power supply is connected to the collector of the transistor Q2; the emitter of the transistor Q2 is connected to the emitter of the transistor Q3; the collector of the transistor Q3 is connected to the -12V power supply. The emitter of the transistor Q2 is connected to the opposite end of the secondary winding of the current transformer T1.

[0051] exist Figure 2 In the leakage current detection and self-test circuit shown in FIG. 1 , transistors Q2 and Q3 in the oscillation circuit are NPN transistors and PNP transistors, respectively. Assume that the OUT pin (i.e., O pin) of the 555 timer outputs a high level, at which time transistor Q2 is turned on and transistor Q3 is turned off. At this time, the midpoint voltage of transistors Q2 and Q3 is +12V, and the midpoint voltage of transistors Q2 and Q3 will be sent to the leakage current detection transformer (such as Figure 2 The secondary coil of the current transformer T1 shown in the figure is charged, and when the leakage current detection transformer (such as Figure 2 When the secondary coil of the current transformer T1 shown in FIG. 1 is positively charged and reaches saturation, the leakage current detection transformer (such as Figure 2The current in the secondary coil of the current transformer T1 shown in the figure rises, and the voltage on the resistor R6 suddenly increases, causing the voltage at the THR pin input terminal of the 555 timer and the voltage at the TR pin input terminal of the 555 timer to increase and exceed 8V. The secondary coil has a charging process, which is equivalent to the charging process of the inductor. Before it is fully charged, the current changes slowly. After it is fully charged, the coil can be considered to be short-circuited, and the current in the coil suddenly increases, causing it to rise. Since the THR pin of the 555 timer and the TR pin of the 555 timer are the input terminals of the internal comparator of the 555 timer, the OUT pin of the 555 timer outputs a low level, and the output terminal of the operational amplifier U1 outputs a low level. At this time, the transistor Q2 is turned off, the transistor Q3 is turned on, and the midpoint voltage between the transistor Q2 and the transistor Q3 becomes -12V, and the leakage current detection transformer (such as Figure 2 The secondary coil of the current transformer T1 shown in FIG. 1 is reversely charged, so that the leakage current detection transformer (such as Figure 2 The current transformer T1 shown in the figure is always in the detection state. When the leakage current detection transformer (such as Figure 2 When leakage current occurs in the circuit where the current transformer T1 is located, the leakage current signal can be quickly detected. When the ground line or power line is connected to the primary side of the current transformer, when leakage current occurs in the line, the leakage current will be sensed from the primary side to the secondary side by the current transformer, and then input to the MCU through the conditioning circuit, so as to be detected.

[0052] Similarly, when the leakage current detection transformer (such as Figure 2 When the secondary coil of the current transformer T1 shown in FIG. 1 is reversely charged and reaches a saturation state, the OUT pin of the 555 timer outputs a high level potential. At this time, the operational amplifier U1 outputs a high level, so the midpoint voltage of the transistor Q2 and the transistor Q3 becomes +12V again.

[0053] The CV pin of the 555 timer is the reference voltage setting pin. The voltage on the CV pin is used as the reference value. The voltage comparisons on the THR pin and the TR pin are based on the voltage on the CV pin. Tring level = 1 / 3U CV , Thres level = 2 / 3U CV In the initial state, the OUT pin of the 555 timer outputs high and low levels based on the voltage comparison between the THR pin and the TR pin and the CV pin. For details, please refer to the table below.

[0054]

[0055] In the solution of the present invention, a 555 timer, an operational amplifier U1, a transistor Q2, a transistor Q3, and a leakage current detection transformer (such as Figure 2The secondary coil of the current transformer T1 shown in FIG. 1 constitutes a self-excited oscillator. The width of the positive pulse and the negative pulse of the self-excited oscillator are the same, and it is easy to know that the self-excited oscillation frequency of the oscillator is the same as that of the leakage current detection transformer (such as Figure 2 The core saturation characteristics of the current transformer T1 shown in the figure, the leakage current detection resistor (such as resistor R6) and the magnitude of the leakage current are related, but once the oscillation circuit is determined, the oscillation frequency is only related to the magnitude of the leakage current. Among them, resistor R6 is used to convert the leakage current signal into a voltage signal.

[0056] In some implementations, the filtering unit includes: a second operational amplifier module (such as Figure 2 The operational amplifier U2 shown in the figure), the two-stage RC filter module (such as Figure 2 The two-stage RC filter circuit composed of the resistor R9, the resistor R10, the capacitor C3, and the capacitor C4 shown in the figure), and the third operational amplifier module (such as Figure 2 The operational amplifier U3).

[0057] Wherein, the output terminal of the leakage current sampling signal of the oscillation unit is as follows: Figure 2 The common end of the resistor R6 and the same-name end of the secondary winding, that is, the same-name end of the secondary winding, can be connected to the in-phase input end of the second operational amplifier module; the inverting input end of the second operational amplifier module is connected to the output end of the second operational amplifier module; the output end of the second operational amplifier module, after passing through the two-stage RC filtering module, can be connected to the in-phase input end of the third operational amplifier module; the inverting input end of the third operational amplifier module is connected to the output end of the third operational amplifier module; the output end of the third operational amplifier module is connected to the input end of the conditioning unit (such as Figure 2 The resistor R11 shown is connected to the common terminal of the operational amplifier U3).

[0058] exist Figure 2In the example shown, the low-pass filter circuit includes: resistors R7, R8, R9, R10, capacitors C2, C3, C4, operational amplifiers U2, and U3. The same-name end of the secondary winding of the current transformer T1 is connected to the non-inverting input end of the operational amplifier U2 through resistors R7 and R8; the non-inverting input end of the operational amplifier U2 is grounded through capacitor C2; the inverting input end of the operational amplifier U2 is grounded; the inverting input end of the operational amplifier U2 is also connected to the output end of the operational amplifier U2; the power supply end of the operational amplifier U2 is connected to a 12V power supply, and the ground end of the operational amplifier U2 is grounded. The output end of the operational amplifier U2 is connected to the non-inverting input end of the operational amplifier U3 through resistors R9 and R10; the non-inverting input end of the operational amplifier U3 is grounded through capacitor C3; the inverting input end of the operational amplifier U3 is grounded; the inverting input end of the operational amplifier U3 is connected to the output end of the operational amplifier U3, the ground end of the operational amplifier U3 is grounded, and the power supply end of the operational amplifier U3 is connected to a 12V power supply. The common end of the resistor R9 and the resistor R10 is connected to the output end of the operational amplifier U3 through capacitor C4. The output end of the operational amplifier U3 is connected to the sampling and conditioning circuit, and the output end of the operational amplifier U3 is connected to the input end of the sampling and conditioning circuit. Preferably, the inverting input end of the operational amplifier U3 is grounded through resistor R23, and the inverting input end of the operational amplifier U3 is connected to the output end of the operational amplifier U3 through resistor R24.

[0059] exist Figure 2In the leakage current detection and self-test circuit shown, in the low-pass filter circuit, resistor R8, resistor R21, resistor R22 and operational amplifier U2 form a common-phase proportional amplifier circuit, and resistor R8, resistor R7, capacitor C2, and capacitor C8 form a two-stage RC filter circuit. A negative feedback circuit (i.e., an inverting proportional operational circuit) is introduced between the output end of the operational amplifier U2 and the inverting input end of the operational amplifier U2. In different frequency bands, the polarity of the negative feedback circuit will change. When the frequency f of the self-excited oscillator is greater than the cut-off frequency fc, the two-stage RC filter circuit will shift the phase to -180°, so that the input voltage of the negative feedback circuit is opposite to the phase of the output voltage. At this time, the feedback from the output end of the operational amplifier U2 to the inverting input end of the operational amplifier U2 through the capacitor C2 is negative feedback. The negative feedback acts on the inverting input end of the operational amplifier U2 to reduce the input signal, and at the same time, the voltage amplification factor of the operational amplifier U2 is reduced. Therefore, the amplitude-frequency characteristic of the second-order low-pass active filter decays rapidly in the high frequency band and can only pass low-frequency signals. For the input voltage and output voltage of the same operational amplifier, each stage of RC brings a 90-degree phase shift, and two stages bring a 180-degree phase shift. The net input decreases during negative feedback, that is, the input minus the feedback equals the net input, and the negative feedback reduces the amplification factor. In the scheme of the present invention, two second-order low-pass active filters with the same architecture are used to realize the high-frequency carrier signal generated by the self-excited oscillation circuit, thereby obtaining a low-frequency leakage current detection signal. The sampling and conditioning circuit plays a signal conditioning role; the low-pass filter circuit allows low-frequency signals to pass through and filters out high-frequency signals. The leakage current signal is a low-frequency signal, which will be retained after the low-pass filter circuit and can be transmitted to the MCU.

[0060] In some embodiments, the protection unit includes: a first capacitor module (such as Figure 2 The capacitor C6 shown in FIG. Figure 2 Capacitor C7 as shown), diode module (such as Figure 2 The diode D2 shown in the figure), the discharge resistor module (such as Figure 2 The resistor R16 and the resistor R17 shown in FIG. 1 ), the fourth switch tube module (such as Figure 2 The switch tube Q4 shown in FIG. 1 ), the third current limiting resistor module (such as Figure 2 The resistor R18 shown), and the fourth current limiting resistor module (such as Figure 2 Resistor R19 shown).

[0061] Among them, the opposite end of the secondary winding is connected to the anode of the diode module after passing through the first capacitor module; the anode of the diode module and the cathode of the diode module are grounded after passing through the discharge resistor module respectively; the cathode of the diode module is connected to the control end of the fourth switch tube (such as the base of the transistor Q4) after passing through the third current limiting resistor module and the fourth current limiting resistor module. The preset fourth DC power supply (such as a 3V DC power supply) can be connected to the first connection end of the fourth switch tube (such as the collector of the transistor Q4); the first connection end of the fourth switch tube (such as the collector of the transistor Q4), as the output end of the protection unit, is also connected to the input end of the conditioning unit; the second connection end of the fourth switch tube (such as the emitter of the transistor Q4) is grounded.

[0062] exist Figure 2 In the example shown, the differential protection circuit includes: resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, capacitor C6, capacitor C7, diode D2, transistor Q4. Among them, the opposite end of the secondary winding of the current transformer T1 is grounded after passing through capacitor C6 and resistor R16; the common end of capacitor C6 and resistor R16 is connected to the anode of diode D2, the cathode of diode D2 is grounded after passing through resistor R17, the cathode of diode D2 is also grounded after passing through resistor R18 and capacitor C7, the common end of resistor R18 and capacitor C7 is connected to the base of transistor Q4 after passing through resistor R19; the 3V power supply is connected to the collector of transistor Q4 after passing through resistor R20, and the emitter of transistor Q4 is grounded. The collector of transistor Q4 is connected to the input end of the sampling and conditioning circuit.

[0063] exist Figure 2 In the leakage current detection and self-test circuit shown in FIG. Figure 2The differential protection circuit shown in FIG. 1 is mainly composed of capacitor C6, resistor R16, diode D2, resistor R18, resistor R19, capacitor C7, resistor R20 and NPN transistor Q4 and related circuits. The high-frequency signal of the self-excited oscillator will be transmitted to the anode of diode D2 through the differential capacitor (such as capacitor C6), and capacitor C7 will be charged through diode D2 and resistor R17. Resistors R16 and R17 are the discharge resistors of capacitor C6 and capacitor C7 respectively, resistor R18 is the current limiting resistor of capacitor C7, resistor R19 is the base current limiting resistor of transistor Q4, +3V is the reference voltage, and the values ​​of resistors R20 and R11 are equal, so that a DC bias voltage of 1.5V can be formed at the in-phase input terminal of operational amplifier U4 in the sampling and conditioning circuit. Due to the unidirectional conductivity of diode D2, only the high-frequency positive pulse signal energy in the self-excited oscillator charges capacitor C7 through capacitor C6. At this time, the high-frequency positive pulse signal in the self-excited oscillator charges capacitor C7 through resistor R18, so the charging time constant is determined by resistor R18 and capacitor C7; and during the high-frequency negative pulse signal in the self-excited oscillator, the energy in capacitor C7 is discharged through resistor R18 and resistor R17, so the discharge time constant is determined by resistor R17, resistor R18 and capacitor C7. Obviously, the discharge time of capacitor C7 is slower than its charging time. After capacitor C7 is charged, the first-order zero input response circuit, the moment capacitor C7 discharges is equivalent to a power supply and resistor R18 and resistor R17 forming a loop for discharge.

[0064] When the frequency of the self-excited oscillator is not high enough, the energy charged by capacitor C7 during the high-frequency positive pulse will be completely discharged during the high-frequency negative pulse, or the voltage on capacitor C7 will be insufficient to turn on transistor Q4. At this time, a 1.5V DC bias voltage is formed at the in-phase input of operational amplifier U4 in the sampling and conditioning circuit. When the frequency of the self-excited oscillation is high enough, the charging frequency of capacitor C7 becomes faster, so the energy charged during the high-frequency positive pulse cannot be fully discharged during the high-frequency negative pulse, which causes the voltage accumulated on capacitor C7 to be sufficient to turn on transistor Q4, thereby pulling the in-phase input of operational amplifier U4 in the sampling and conditioning circuit down to 0 potential. It can be seen that the differential detection protection circuit (such as Figure 2 The function of the differential protection circuit shown in FIG. 1 is to determine whether a DC bias voltage is added to the sampling and conditioning circuit according to whether the frequency of the self-excited oscillator is high enough.

[0065] In some embodiments, the conditioning unit includes: a fifth current limiting resistor module (such as Figure 2 The resistor R11 shown in FIG. 1 ), the sixth current limiting resistor module (such as Figure 2 The resistor R12 shown), RC setting module (such as Figure 2 The resistor R13, the resistor R14 and the capacitor C5 shown in FIG. Figure 2The operational amplifier U4 shown in FIG. Figure 2 The resistor R15).

[0066] Wherein, the output end of the filtering unit (such as Figure 2 The output end of the operational amplifier U3), and the output end of the protection unit (such as Figure 2 The collector of the transistor Q4 is connected to the inverting input terminal of the fourth operational amplifier module after passing through the fifth current limiting resistor module; a preset fifth DC power supply (such as a 1.5V DC power supply) can be connected to the inverting input terminal of the fourth operational amplifier module; the non-inverting input terminal of the fourth operational amplifier module is connected to the output terminal of the fourth operational amplifier module after passing through the RC setting module; the output terminal of the fourth operational amplifier module can be connected to the sampling terminal of the control unit after passing through the seventh current limiting resistor module to output the leakage current detection signal to the control unit.

[0067] exist Figure 2 In the example shown, the sampling and conditioning circuit includes: resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, capacitor C5, and operational amplifier U4. The first connection end of resistor R11, as the input end of the sampling and conditioning circuit, is connected to the output end of operational amplifier U3 and the collector of transistor Q4. The second connection end of resistor R11 is connected to the inverting input end of operational amplifier U4; the 1.5V power supply is connected to the inverting input end of operational amplifier U4 through resistor R12; the non-inverting input end of operational amplifier U4 is grounded through resistor R13; the non-inverting input end of operational amplifier U4 is also connected to the output end of operational amplifier U4 through resistor R14 and capacitor C5 in parallel; the output end of operational amplifier U4 is connected to the sampling end of MCU through resistor R15.

[0068] Figure 2 The sampling and conditioning circuit in the circuit is an emitter follower composed of an operational amplifier U4, and the non-inverting input terminal of the operational amplifier U4 is superimposed with a low-frequency leakage current signal from an active low-pass filter (such as a low-pass filter circuit) and a DC bias voltage signal determined by a differential detection protection circuit, and the superimposed signal is sent to the AD sampling channel of the controller (such as an MCU) through the output terminal of the operational amplifier U4. The differential detection protection circuit is mainly used to ensure that when a relatively large leakage current or short-circuit current appears in the leakage current detection circuit, it plays a role in protecting the sampling and conditioning circuit and the MCU. Excessive leakage current or short-circuit current will generate high voltage on the resistor R6. If there is no differential detection protection circuit, the high voltage will exceed the withstand voltage range of the subsequent circuit, resulting in damage to the device.

[0069] According to the technical solution of the present invention, a leakage current detection transformer, a self-detection unit (such as a self-detection circuit), a filter unit (such as a low-pass filter circuit), an oscillation unit (such as an oscillation circuit), a protection unit (such as a differential protection circuit), a conditioning unit (such as a sampling conditioning circuit), and a control unit (such as an MCU) are arranged on the grid side of the grid-side converter, wherein: the first winding, the second winding, the third winding, and the fourth winding in the primary winding of the leakage current detection transformer are connected between the grid side and the converter, the fifth winding in the primary winding of the leakage current detection transformer is connected to the self-detection unit, and the self-detection unit is used to generate a current of a certain value, so that the filter unit (such as a low-pass filter circuit), the oscillation unit (such as an oscillation circuit), the protection unit (such as a differential protection circuit), and the conditioning unit (such as a sampling conditioning circuit) constitute The detection circuit performs detection based on the current of the certain value to determine whether the detection circuit is in a normal working state; the oscillation unit generates an oscillation signal on the secondary winding to reflect it to the primary winding to become a carrier signal of the leakage current, and then transmits it to the secondary winding to obtain a leakage current sampling signal; the filtering unit filters the leakage current sampling signal output by the oscillation unit, the protection unit controls the conditioning unit according to the oscillation signal generated by the oscillation unit, and the conditioning unit conditions the signal filtered by the filtering unit and the protection signal of the protection unit to output the leakage current detection signal to the control unit, so that the control unit performs processing based on the leakage current detection signal; thereby, by detecting the leakage current on the ground wire of the grid-side converter or the power line connected to the grid side, self-detection and protection can be achieved to improve safety.

[0070] According to an embodiment of the present invention, a frequency converter corresponding to the leakage current detection device is also provided. The frequency converter may include: the leakage current detection device described above.

[0071] Since the processing and functions implemented by the frequency converter of this embodiment basically correspond to the embodiments, principles and examples of the device, for the details not described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0072] According to an embodiment of the present invention, an energy storage converter corresponding to the leakage current detection device is also provided. The energy storage converter may include: the leakage current detection device described above.

[0073] Since the processing and functions implemented by the energy storage converter of this embodiment basically correspond to the embodiments, principles and examples of the device, for the details not described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0074] According to an embodiment of the present invention, a leakage current detection method corresponding to the leakage current detection device is also provided, such as Figure 4The flowchart of an embodiment of the method of the present invention is shown in FIG. The leakage current detection method may include: steps S110 to S160.

[0075] At step S110, a constant current is generated through the self-test unit based on a trigger signal (such as a 3.3V to 5V high-level voltage) input from a preset trigger pin; the constant current generates a self-test current through the fifth winding, so that the leakage current detection device performs detection based on the self-test current to determine whether the leakage current detection device is in a preset working state (such as a normal working state), thereby realizing self-test of the leakage current detection device.

[0076] At step S120, through the oscillation unit, when the leakage current detection device is in a preset working state, an oscillation signal is generated on the secondary winding to be reflected to the primary winding to become a carrier signal of the leakage current, and then transmitted to the secondary winding to obtain a leakage current sampling signal.

[0077] In step S130, the leakage current sampling signal is filtered by the filtering unit to obtain a leakage current filtering signal.

[0078] In step S140, the protection unit performs protection based on the leakage current sampling signal to obtain a protection signal.

[0079] In step S150, the conditioning unit performs conditioning based on the leakage current filter signal and the protection signal to obtain a conditioned signal as a leakage current detection signal obtained by detecting the leakage current of the grid-side converter from the grid side.

[0080] In step S160, the grid-side converter is controlled based on the leakage current detection signal to implement leakage current protection for the grid-side converter.

[0081] In the solution of the present invention, through the leakage current detection and self-test circuit, for the grid-side converter, by detecting the leakage current on the ground wire or the power line connected to the grid side, the magnitude of the short-circuit current and the leakage current can be identified, and the problem that the wire diameter of the three-phase incoming cable is too thick to pass through the leakage current detection device can be solved; and the solution of the present invention, while detecting the leakage current, has a self-test circuit and a protection circuit to ensure the integrity of the current detection function and improve safety.

[0082] In some implementations, in step S160, the grid-side converter is controlled based on the leakage current detection signal to implement leakage current protection for the grid-side converter. Please refer to the following exemplary description for the specific process.

[0083] Combine the following Figure 5The flowchart of an embodiment of controlling the grid-side converter based on the leakage current detection signal in the method of the present invention further illustrates the specific process of controlling the grid-side converter based on the leakage current detection signal in step S160, including: step S210 to step S240.

[0084] Step S210, determining whether the current value corresponding to the leakage current detection signal is less than a preset first current value and the duration is less than a preset first time; wherein the preset first current value is such as 100 mA, and the preset first time is such as 0.2 s.

[0085] Step S220: If it is determined that the condition is satisfied, the sudden residual current of the grid-side converter is determined according to the leakage current detection signal.

[0086] Step S230, if it is determined that the sudden residual current of the grid-side converter is greater than or equal to the preset second current value, or it is determined that the sudden residual current of the grid-side converter is less than the preset second current value but greater than or equal to the preset third current value and the duration is less than the preset second time, or it is determined that the sudden residual current of the grid-side converter is less than the preset third current value but greater than or equal to the preset fourth current value and the duration is less than the preset first time, then a reminder message is initiated that the grid-side converter has a leakage current fault.

[0087] Step S240, after the grid-side converter is shut down for protection, determine whether the current value corresponding to the leakage current detection signal is less than the preset fifth current value and the duration reaches the preset third time: if so, clear the reminder message and restart the grid-side converter, otherwise continue to initiate a reminder message that the grid-side converter has a leakage current fault; wherein, the preset fifth current value is greater than the preset fourth current value and less than the preset third current value, the preset first time is greater than the preset second time and less than the preset third time, the preset second current value is such as 150mA, the preset third current value is such as 60mA, the preset fourth current value is such as 30mA, the preset fifth current value is such as 50mA, the preset second time is such as 0.1s, and the preset third time is such as 5.5s.

[0088] Figure 3 FIG. 1 is a flow chart of the leakage current detection and self-test method of the present invention. Figure 3 As shown, the leakage current detection and self-test method includes:

[0089] Step 1, 25mA (milliampere) self-test and calculate the 25mA coefficient, then proceed to step 2. The resistance value of resistor R2 is set to 1kΩ, 2.5V divided by the resistance value of resistor R2 and multiplied by the number of turns of the self-test coil (fifth winding) 10, the current of the self-test coil is 25mA.

[0090] Step 2: Perform continuous residual current protection to determine whether the continuous leakage current is less than 100 mA and the duration does not exceed 0.2 seconds: If yes, proceed to step 21; otherwise, proceed to step 3. Residual current and leakage current are just called differently. The name of residual current is in the standard NB / T+3200.

[0091] Step 21, calculate the sudden residual current to obtain the sudden residual current (GFCI), and then execute step 22. There are three types of leakage current: AC sinusoidal, smooth DC, and transient DC. The sudden residual current belongs to transient DC, that is, the current waveform is discontinuous.

[0092] Step 22, determine whether GFCI < 150mA is satisfied: if so, proceed to step 23; otherwise, proceed to step 3.

[0093] Step 23, determine whether GFCI≥60mA and Jump2_Fault<0.1s: if so, execute step 24; otherwise, execute step 3.

[0094] Step 24, determine whether GFCI≥30mA and Jump2_Fault<0.2s: If so, execute step 25; otherwise, execute step 3.

[0095] The leakage current is judged from large to small. Different leakage current values ​​have different time requirements for disconnection from the power grid. For details, please refer to the exemplary description of the response time of the sudden change current in the table below. Jump2_Fault means that the detection response time does not exceed 0.2s.

[0096]

[0097] Step 25: Determine that the leakage current is normal, clear the relevant flag, and end the current detection.

[0098] Step 3: Report the total protection position 1, and then execute step 31.

[0099] Step 31, after executing the leakage current protection, determine whether the effective value of the leakage current is less than 50mA and the duration is 5.5s: if so, clear all faults and restart; otherwise, report an error to determine that there is a fault.

[0100] Among them, clearing the relevant flags and reporting the total protection position 1 are set in the program. For example, when the flag is set, if the condition is met: the continuous leakage current is less than 100mA and does not exceed 0.2s, flag = 1, otherwise flag = 0. The program makes conditional judgments based on the flag value. The total protection bit is also set by the program, and the value of the total protection bit is determined by judging the conditions of other flags. If flag and flag1 are both equal to 1, the total protection bit is set to 1; otherwise, it is set to 0.

[0101] In the solution of the present invention, when leakage current occurs in the grid-side converter (such as a frequency converter, an energy storage converter, etc.), an oscillating circuit constructed by a 555 timer is connected to the leakage current detection transformer (such as Figure 2 A high-frequency oscillation signal is generated on the secondary winding of the current transformer T1 shown in FIG. 1 , and is reflected to the leakage current detection transformer (such as Figure 2 The primary winding of the current transformer T1 shown in FIG. 1 is used as a carrier signal of the low-frequency leakage current, and the low-frequency leakage current is transmitted to the leakage current detection transformer (such as Figure 2 The secondary side of the current transformer T1 shown in the figure can obtain a low-frequency leakage current signal after filtering out the high-frequency oscillation signal through a low-pass filter, and then send it to the AD sampling channel of the controller MCU after passing through the sampling and conditioning circuit. Then the software implements the corresponding calculation, logic judgment and protection functions to improve safety.

[0102] The solution of the present invention can be applied to frequency converters and power conversion systems (PCS). The PCS can control the charging and discharging process of the battery, perform AC / DC conversion, and directly supply power to AC loads when there is no power grid.

[0103] Since the processing and functions implemented by the method of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned frequency converter and energy storage converter, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0104] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0105] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A leakage current detection device, characterized in that: Used to detect leakage current of a grid-side converter from the grid side; the leakage current detection device comprises: a leakage current detection transformer, a self-checking unit, a filtering unit, an oscillating unit, a protection unit, a conditioning unit, and a control unit; the primary winding of the leakage current detection transformer comprises a first winding, a second winding, a third winding, a fourth winding, and a fifth winding, and the first winding, the second winding, the third winding, and the fourth winding are connected in series with a three-phase four-wire alternating current line on the grid side; the fifth winding is connected to the self-checking unit; the secondary winding of the leakage current detection transformer is connected to the oscillating unit and the protection unit respectively; the filtering unit is connected to the oscillating unit, and the conditioning unit is connected to the filtering unit and the protection unit respectively; wherein, The self-test unit is used to generate a constant current based on a trigger signal input from a preset trigger pin; the constant current generates a self-test current through the fifth winding, so that the leakage current detection device performs detection based on the self-test current to determine whether the leakage current detection device is in a preset working state; The oscillation unit is used to generate an oscillation signal on the secondary winding when the leakage current detection device is in a preset working state, so as to reflect the oscillation signal to the primary winding to become a carrier signal of the leakage current, and then transmit the oscillation signal to the secondary winding to obtain a leakage current sampling signal; The filtering unit is used to filter the leakage current sampling signal to obtain a leakage current filtering signal; The protection unit is used to perform protection based on the leakage current sampling signal to obtain a protection signal; The conditioning unit is used to perform conditioning based on the leakage current filter signal and the protection signal to obtain a conditioning signal as a leakage current detection signal obtained by detecting the leakage current of the grid-side converter from the grid side; The control unit is used to control the grid-side converter based on the leakage current detection signal to achieve leakage current protection for the grid-side converter.

2. The leakage current detection device according to claim 1, characterized in that: The self-test unit includes: a first current limiting resistor module, a second current limiting resistor module, a first switch tube module, a voltage regulator diode module, and a protection module for the fifth winding; wherein, A preset first DC power supply is connected to the same-name end of the fifth winding after passing through the protection module of the fifth winding; and the opposite-name end of the fifth winding is connected to the first connection end of the first switch tube module; A preset input trigger pin is connected to the control end of the first switch tube module through the first current limiting resistor module; a second connection end of the first switch tube module is grounded through the second current limiting resistor module; The preset input trigger pin is also connected to the cathode of the voltage regulator diode module; the anode of the voltage regulator diode module is grounded; and the control end of the voltage regulator diode module is connected to the second connection end of the first switch tube module.

3. The leakage current detection device according to claim 1 or 2, characterized in that: The oscillation unit includes: an oscillation module and a sampling resistor module; wherein, The secondary winding is connected to the oscillation module to form a self-excited oscillator; The same-name end of the secondary winding is connected to the first connection end of the sampling resistor module; the second connection end of the sampling resistor module is connected to the oscillation module and grounded; The first connection end of the sampling resistor module is also connected to the filtering unit; the oscillation module is also connected to the protection unit.

4. The leakage current detection device according to claim 3, characterized in that: The oscillation module includes: a timing module, a first operational amplifier module, a second switch tube module, and a third open tube module; wherein, The same-name end of the secondary winding is connected to the ground pin of the timing module after passing through the sampling resistor module; the same-name end of the secondary winding and the common end of the sampling resistor module are connected to the discharge pin of the timing module and the threshold pin of the timing module respectively; the same-name end of the secondary winding and the common end of the sampling resistor module, as the output end of the oscillation unit, are connected to the input end of the filtering unit; The opposite-phase end of the secondary winding is connected to the trigger pin of the timing module; the output pin of the timing module can be connected to the non-inverting input end of the first operational amplifier module; the inverting input end of the first operational amplifier module is used to receive a preset reference voltage signal; the output end of the first operational amplifier module is respectively connected to the control end of the second switch tube module and the control end of the third switch tube module; A preset second DC power supply is connected to the first connection end of the second switch tube module; the second connection end of the second switch tube module is connected to the first connection end of the third switch tube module; a preset third DC power supply is connected to the second connection end of the third switch tube module; the second connection end of the second switch tube module is also respectively connected to the opposite-name end of the secondary winding and the input end of the protection unit.

5. The leakage current detection device according to any one of claims 1 to 4, characterized in that: The filtering unit includes: a second operational amplifier module, a two-stage RC filtering module, and a third operational amplifier module; wherein, The output end of the leakage current sampling signal of the oscillation unit can be connected to the non-inverting input end of the second operational amplifier module; the inverting input end of the second operational amplifier module is connected to the output end of the second operational amplifier module; the output end of the second operational amplifier module can be connected to the non-inverting input end of the third operational amplifier module after passing through the two-stage RC filtering module; the inverting input end of the third operational amplifier module is connected to the output end of the third operational amplifier module; the output end of the third operational amplifier module is connected to the input end of the conditioning unit.

6. The leakage current detection device according to any one of claims 1 to 5, characterized in that: The protection unit includes: a first capacitor module, a second capacitor module, a diode module, a discharge resistor module, a fourth switch module, a third current limiting resistor module, and a fourth current limiting resistor module; wherein, The opposite-name end of the secondary winding is connected to the anode of the diode module after passing through the first capacitor module; the anode of the diode module and the cathode of the diode module are grounded after passing through the discharge resistor module respectively; the cathode of the diode module is connected to the control end of the fourth switch tube after passing through the third current limiting resistor module and the fourth current limiting resistor module; The preset fourth DC power supply can be connected to the first connection end of the fourth switch tube; the first connection end of the fourth switch tube, as the output end of the protection unit, is also connected to the input end of the conditioning unit; the second connection end of the fourth switch tube is grounded.

7. The leakage current detection device according to any one of claims 1 to 6, characterized in that: The conditioning unit includes: a fifth current limiting resistor module, a sixth current limiting resistor module, an RC setting module, a fourth operational amplifier module, and a seventh current limiting resistor module; wherein, The output end of the filtering unit and the output end of the protection unit are connected to the inverting input end of the fourth operational amplifier module after passing through the fifth current limiting resistor module; the preset fifth DC power supply can be connected to the inverting input end of the fourth operational amplifier module; the non-inverting input end of the fourth operational amplifier module is connected to the output end of the fourth operational amplifier module after passing through the RC setting module; the output end of the fourth operational amplifier module can be connected to the sampling end of the control unit after passing through the seventh current limiting resistor module to output the leakage current detection signal to the control unit.

8. A frequency converter, characterized in that: include: The leakage current detection device according to any one of claims 1 to 7.

9. An energy storage converter, characterized in that: include: The leakage current detection device according to any one of claims 1 to 7.

10. A leakage current detection method corresponding to the leakage current detection device according to any one of claims 1 to 7, characterized in that: include: By means of the self-checking unit, a constant current is generated based on a trigger signal input from a preset trigger pin; The constant current generates a self-test current through the fifth winding, so that the leakage current detection device performs detection based on the self-test current to determine whether the leakage current detection device is in a preset working state; By means of the oscillation unit, when the leakage current detection device is in a preset working state, an oscillation signal is generated on the secondary winding to be reflected to the primary winding to become a carrier signal of the leakage current, and then transmitted to the secondary winding to obtain a leakage current sampling signal; The leakage current sampling signal is filtered by the filtering unit to obtain a leakage current filtering signal; By means of the protection unit, protection is performed based on the leakage current sampling signal to obtain a protection signal; By means of the conditioning unit, conditioning is performed based on the leakage current filter signal and the protection signal to obtain a conditioning signal as a leakage current detection signal obtained by detecting the leakage current of the grid-side converter from the grid side; The grid-side converter is controlled based on the leakage current detection signal to implement leakage current protection for the grid-side converter.

11. The leakage current detection method according to claim 10, characterized in that: The grid-side converter is controlled based on the leakage current detection signal to implement leakage current protection for the grid-side converter, including: Determine whether the current value corresponding to the leakage current detection signal is less than a preset first current value and the duration is less than a preset first time; If it is determined that the condition is satisfied, determining the sudden residual current of the grid-side converter according to the leakage current detection signal; If it is determined that the sudden residual current of the grid-side converter is greater than or equal to the preset second current value, or it is determined that the sudden residual current of the grid-side converter is less than the preset second current value but greater than or equal to the preset third current value and the duration is less than the preset second time, or it is determined that the sudden residual current of the grid-side converter is less than the preset third current value but greater than or equal to the preset fourth current value and the duration is less than the preset first time, then a reminder message that the grid-side converter has a leakage current fault is initiated; Until the grid-side converter is shut down for protection, determine whether the current value corresponding to the leakage current detection signal is less than the preset fifth current value and the duration reaches the preset third time: if so, clear the reminder message and restart the grid-side converter; otherwise, continue to initiate a reminder message that the grid-side converter has a leakage current fault; wherein the preset fifth current value is greater than the preset fourth current value and less than the preset third current value, and the preset first time is greater than the preset second time and less than the preset third time.

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