Leakage current detection device, frequency converter and energy storage converter

Abstract

The utility model discloses a leakage current detection device, a frequency converter and an energy storage converter, and the device comprises a self-checking 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 utility model belongs to the technical field of leakage current detection, specifically relates to a leakage current detection device, frequency converter and energy storage converter, especially relates to a leakage current detection and self-checking circuit, frequency converter and energy storage converter. BACKGROUND

[0002] When the leakage current appears in the grid-side converter (such as frequency converter, energy storage converter, etc.), the leakage current needs to be self-checked to ensure the safety when the converter is powered on. However, in the related scheme, the grid-side converter does not have a self-checking function, which has a safety hazard.

[0003] The above content is only used to assist in understanding the technical scheme of the utility model and does not represent the acknowledgement of the above content as prior art. UTILITY MODEL CONTENT

[0004] The utility model aims at providing a leakage current detection device, frequency converter and energy storage converter to solve the problem of safety hazard in the related scheme when the grid-side converter does not have a self-checking function, and achieve the effect of self-checking and protection through detecting the leakage current on the ground wire of the grid-side converter or the power line connected to the grid, and improve the safety.

[0005] The utility model provides a leakage current detection device, apply to the leakage current of grid side converter from the grid side detection, the leakage current detection device, include: leakage current detection mutual inductor, self inspection unit, filter unit, oscillation unit, protection unit, conditioning unit and control unit, the primary winding of leakage current detection mutual inductor has first winding, second winding, third winding, fourth winding and fifth winding, first winding second winding third winding fourth winding corresponds to the line of three phase four line ac of stringing into the grid side, fifth winding is connected with self inspection unit, the secondary winding of leakage current detection mutual inductor is connected with oscillation unit and protection unit respectively, filter unit is connected with oscillation unit, conditioning unit is connected with filter unit and protection unit respectively, wherein, self inspection unit is used for generating constant current based on the trigger signal of self preset trigger pin input, the constant current passes through fifth winding and generates self inspection current, to make leakage current detection device detect based on self inspection current, determine whether leakage current detection device is in preset working state, oscillation unit is used for generating oscillation signal on the secondary winding to reflect on the primary winding to become the carrier signal of leakage current under the condition that leakage current detection device is in preset working state, then transmission to the secondary winding obtains leakage current sampling signal, filter unit is used for filtering leakage current sampling signal, obtains leakage current filter signal, protection unit is used for protection based on leakage current sampling signal, obtains protection signal, conditioning unit is used for conditioning based on leakage current filter signal and protection signal, obtains conditioning signal, as leakage current detection signal that leakage current of grid side converter from the grid side detection obtains, control unit is used for controlling grid side converter based on leakage current detection signal, to realize the leakage current protection of grid side converter.

[0006] In some embodiments, the self inspection unit includes a first current limiting resistor module, a second current limiting resistor module, a first switch tube module, a voltage stabilizing diode module, and a protection module of the fifth winding. A preset first DC power supply is connected to the same name end of the fifth winding through the protection module of the fifth winding. The different 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. The 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 stabilizing diode module. The anode of the voltage stabilizing diode module is grounded. The control end of the voltage stabilizing diode module is connected to the second connection end of the first switch tube module.

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

[0008] In some embodiments, the oscillation module comprises: a timing module, a first operational amplifier module, a second switch tube module, and a third switch tube module; wherein the same name end of the secondary winding is connected with the ground pin of the timing module 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 with the input end of the filter unit as the output end of the oscillation unit; the different name end of the secondary winding is connected with 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 for receiving 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; and the second connection end of the second switch tube module is also respectively connected with the different name end of the secondary winding and the input end of the protection unit.

[0009] In some embodiments, the filter unit comprises: a second operational amplifier module, a two-stage RC filter 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 through the two-stage RC filter module; the inverting input end of the third operational amplifier module is connected to the output end of the third operational amplifier module; and 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 comprises: a first capacitor module, a second capacitor module, a diode module, a bleeder resistor module, a fourth switch tube module, a third current-limiting resistor module, and a fourth current-limiting resistor module; wherein the anti-phase end of the secondary winding is connected to the anode of the diode module via the first capacitor module; the anode of the diode module and the cathode of the diode module are respectively connected to the ground via the bleeder resistor module; the cathode of the diode module is connected to the control end of the fourth switch tube via 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 serves as an output end of the protection unit and is also connected to the input end of the conditioning unit; and the second connection end of the fourth switch tube is grounded.

[0011] In some embodiments, the conditioning unit comprises: 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 filter unit and the output end of the protection unit are connected to the inverting input end of the fourth operational amplifier module via the fifth current-limiting resistor module; a 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 via the RC setting module; and the output end of the fourth operational amplifier module can be connected to the sampling end of the control unit via the seventh current-limiting resistor module to output the leakage current detection signal to the control unit.

[0012] In order to match the above device, the utility model further provides a frequency converter, which comprises the leakage current detection device.

[0013] In order to match the above device, the utility model further provides an energy storage converter, which comprises the leakage current detection device.

[0014] Therefore, the scheme of the utility model, through setting leakage current detection mutual inductor, self-checking unit (such as self-checking circuit), filter unit (such as low pass filter circuit), oscillation unit (such as oscillation circuit), protection unit (such as differential protection circuit), conditioning unit (such as sampling conditioning circuit) and control unit (such as MCU) on the power grid side of the power grid side converter, wherein: the first winding, the second winding, the third winding, the fourth winding in the primary winding winding of leakage current detection mutual inductor are connected between the power grid side and the converter, the fifth winding in the primary winding winding of leakage current detection mutual inductor is connected with the self-checking unit, the self-checking unit is used to generate a certain value of current, so that the detection circuit composed of filter unit, oscillation unit, protection unit, conditioning unit carries out detection based on the certain value of current to determine whether the detection circuit is in normal working state; the oscillation unit generates oscillation signal on the secondary winding to reflect on the primary winding to become the carrier signal of leakage current, and then is transmitted to the secondary winding to obtain leakage current sampling signal; the filter unit carries out filtering to 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, the conditioning unit carries out conditioning output leakage current detection signal to the control unit based on the signal filtered by the filter unit and the protection signal of the protection unit, so that the control unit carries out processing based on the leakage current detection signal; thereby, through detecting the leakage current on the ground wire of the detection power grid side converter or the power supply line connected with the power grid side, self-checking and protection can be realized, and safety is improved.

[0015] Other features and advantages of the utility model will be set forth in the subsequent description, and, partially, become apparent from the description, or be understood from the implementation of the utility model.

[0016] The technical scheme of the utility model will be described in further detail below by means of the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is an embodiment structure schematic view of leakage current detection device of the utility model;

[0018] Figure 2 It is the structure schematic view of main circuit of leakage current detection and self-checking circuit of the utility model;

[0019] Figure 3 It is the flow schematic view of leakage current detection and self-checking method of the utility model;

[0020] Figure 4 It is the flow schematic view of one embodiment of leakage current detection method of the utility model;

[0021] Figure 5 It is the flow schematic view of one embodiment of the method based on the leakage current detection signal to control the power grid side converter of the utility model. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the utility model clearer, the utility model technical scheme will be described clearly and completely below by combining with the utility model specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor belong to the protection scope of the utility model.

[0023] It is considered that, in the related scheme, the grid-side converter does not have a self-checking function, which has a safety hazard. Generally, only the B-type leakage current sensor has a self-checking function, and a part of the leakage current sensor of the related scheme also does not have a self-checking function; when not having a self-checking function, the correctness of the detection result cannot be guaranteed, and the normal operation of the equipment also cannot be guaranteed. For example: some schemes provide a B-type residual current detection protection method and circuit with multi-grade automatic adjustment, but this detection method does not have a corresponding residual current self-checking circuit, and the accuracy of the detection result and the safety of the system cannot be guaranteed when the detection circuit fails. The leakage detection needs a self-checking circuit to ensure the accuracy of the detection result and the safety of the system when power is turned on, and the process of self-checking is similar to the calibration of the metering equipment.

[0024] Some other schemes provide a leakage current detection circuit and an inverter, but this detection method does not have a corresponding self-checking circuit, and the measurement range of the leakage current is limited, and other power segment frequency converters cannot be covered.

[0025] Some other schemes provide a photovoltaic inverter leakage current detection device, and this detection method can detect the leakage current well and has a self-checking circuit, but lacks a corresponding protection circuit, and a large short-circuit current can damage the sampling circuit.

[0026] Therefore, the scheme of the utility model provides a leakage current detection device, specifically a leakage current detection and self-checking circuit, which can identify the size of the short-circuit current and the 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 at the same time of detecting the leakage current, the self-checking circuit and the protection circuit are provided, the integrity of the current detection function is guaranteed, and the safety is improved.

[0027] According to the embodiments of the utility model, a leakage current detection device is provided. Referring to Figure 1 the structural schematic diagram of an embodiment of the device of the utility model. The leakage current detection device is applied to detecting the leakage current of the grid-side converter from the grid side; in the scheme of the utility model, as Figure 1 shown, the leakage current detection device comprises: a leakage current detection transformer (such as Figure 2The current transformer T1), a self-checking unit (such as Figure 2 The self-checking circuit shown), a filtering unit (such as Figure 2 The low-pass filter circuit shown), an oscillation unit (such as Figure 2 The oscillation circuit shown), a protection unit (such as Figure 2 The differential protection circuit shown), a conditioning unit (such as Figure 2 The sampling conditioning circuit shown), and a control unit (such as Figure 2 The 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, the first winding, the second winding, the third winding, the fourth winding correspond to the line of three-phase four-wire alternating current into the power grid side; the fifth winding is connected with the self-checking unit; the secondary winding of the leakage current detection transformer is connected with the oscillation unit and the protection unit respectively; the filtering unit is connected with the oscillation unit, and the conditioning unit is connected with the filtering unit and the protection unit respectively.

[0028] The self-checking 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-checking current through the fifth winding, so that the leakage current detection device detects based on the self-checking current to determine whether the leakage current detection device is in a preset working state (such as a normal working state), and realizes self-checking of the leakage current detection device.

[0029] The oscillation unit is used to generate an oscillation signal on the secondary winding to reflect on the primary winding as a carrier signal of leakage current when the leakage current detection device is in a preset working state, and then transmit to the secondary winding to obtain a leakage current sampling signal.

[0030] The filtering unit is used to filter the leakage current sampling signal to obtain a leakage current filtering signal.

[0031] The protection unit is used to protect based on the leakage current sampling signal to obtain a protection signal.

[0032] The conditioning unit is used to condition 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 power grid side.

[0033] The control unit is used to control the grid-side converter based on the leakage current detection signal to realize leakage current protection of the grid-side converter.

[0034] Figure 2The utility model discloses a leakage current detection and self-checking circuit's structure schematic drawing in main circuit. Figure 2 As shown in the figure, leakage current detection and self-checking circuit in main circuit has current transformer T1, and leakage current detection and self-checking circuit includes: self-checking circuit, low pass filter circuit, sampling conditioning circuit, oscillation circuit, differential protection circuit.

[0035] In Figure 2 As shown in the figure, the primary winding of current transformer T1 includes: first winding, second winding, third winding, fourth winding and fifth winding. The first winding of the primary winding of current transformer T1 is connected to the A line of the three-phase current input end of the power grid side, specifically, the same name end of the first winding of the primary winding of current transformer T1 is connected to the A line of the three-phase current input end of the power grid side, and the different name end of the first winding of the primary winding of current transformer T1 is connected to the rear end part of the A line (such as the part connected to the A line in the power grid side converter). The second winding of the primary winding of current transformer T1 is connected to the B line of the three-phase current input end of the power grid side, specifically, the same name end of the second winding of the primary winding of current transformer T1 is connected to the B line of the three-phase current input end of the power grid side, and the different name end of the second winding of the primary winding of current transformer T1 is connected to the rear end part of the B line (such as the part connected to the B line in the power grid side converter). The third winding of the primary winding of current transformer T1 is connected to the C line of the three-phase current input end of the power grid side, specifically, the same name end of the third winding of the primary winding of current transformer T1 is connected to the C line of the three-phase current input end of the power grid side, and the different name end of the third winding of the primary winding of current transformer T1 is connected to the rear end part of the C line (such as the part connected to the C line in the power grid side converter). The fourth winding of the primary winding of current transformer T1 is connected to the N line of the three-phase current input end of the power grid side, specifically, the same name end of the fourth winding of the primary winding of current transformer T1 is connected to the N line of the three-phase current input end of the power grid side, and the different name end of the fourth winding of the primary winding of current transformer T1 is connected to the rear end part of the N line (such as the part connected to the N line in the power grid side converter). The fifth winding of the primary winding of current transformer T1 is connected to the self-checking circuit.

[0036] The leakage current detection and self-checking circuit provided by the utility model is aimed at the power grid side converter, can identify the size of short-circuit current and leakage current by detecting the leakage current on the ground wire or the power supply line connected to the power grid side, solves the problem that the diameter of the three-phase incoming line cable is too thick to pass through the leakage current detection device, and meanwhile, the utility model has a self-checking circuit and a protection circuit while detecting the leakage current, guarantees the integrity of the current detection function, and improves the safety.

[0037] Wherein, the leakage current is the current between the power line and the ground. There are two kinds of wiring methods for detection, one is that the power lines on the grid side are connected to the transformer, that is, corresponding to A, B, C, N; the other only needs to connect the ground wire to one of A, B, C, N.

[0038] In some embodiments, the self-checking unit comprises: a first current-limiting resistor module (such as the resistor R1 shown in the figure), a second current-limiting resistor module (such as the resistor R2 shown in the figure), a first switch tube module (such as the transistor Q1 shown in the figure), a voltage stabilizing diode module (such as the voltage stabilizing diode D1 shown in the figure), and a protection module of the fifth winding (such as the resistor R0, diode D11 and diode D12 shown in the figure). Figure 2 Figure 2 Figure 2 Figure 2 Figure 2

[0039] Wherein, the preset first direct current power supply (such as 5V direct current power supply) is connected to the same name end of the fifth winding after the protection module of the fifth winding; the different name end of the fifth winding is connected to the first connection end (such as the collector of the transistor Q1) of the first switch tube module. The preset input trigger pin (such as the input pin of the 3.3V-5V direct current power supply) is connected to the control end (such as the base of the transistor Q1) of the first switch tube module after the first current-limiting resistor module; the second connection end (such as the emitter of the transistor Q1) of the first switch tube module is grounded after the second current-limiting resistor module. The preset input trigger pin (such as the input pin of the 3.3V-5V direct current power supply) is also connected to the cathode of the voltage stabilizing diode module; the anode of the voltage stabilizing diode module is grounded; the control end of the voltage stabilizing diode module is connected to the second connection end (such as the emitter of the transistor Q1) of the first switch tube module.

[0040] In the example shown in Figure 2 , the self-checking circuit comprises: 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 protect the circuit by limiting the high voltage generated across the self-checking coil (i.e. the fifth winding) when a large current flows through it.

[0041] ​​​​​The 5V DC power supply, after passing through resistor R0, is connected to the same-name terminal of the fifth winding in the primary winding of current transformer T1. The same-name terminal of the fifth winding in the primary winding of current transformer T1 is also connected to the cathode of diode D11; the anode of diode D11 is grounded. The 5V DC power supply is connected to the cathode of diode D12; the anode of diode D12 is connected to the cathode of diode D11. The opposite-name terminal of the fifth winding in the primary winding of current transformer T1 is connected to the collector of transistor Q1. The 3.3V~5V DC power supply, after passing through resistor R1, is connected to the base of transistor Q1. The emitter of transistor Q1 is grounded after passing through resistor R2. The 3.3V~5V DC power supply is also connected to the cathode of Zener diode D1; the anode of Zener diode D1 is grounded; the control terminal of Zener diode D1 is connected to the emitter of transistor Q1.

[0042] exist Figure 2 In the leakage current detection and self-test circuit shown, the self-test circuit, by inputting a 3.3V~5V high-level voltage through the input trigger pin (i.e., the input pin for a 3.3V~5V voltage), will generate a constant current IT in the branch. This constant current IT directly passes through the leakage current detection transformer (e.g., ...). Figure 2 The fifth winding of the primary winding of the current transformer T1 (shown) generates a self-test current. Figure 2 When the trigger pin input is 3.3V~5V, diode D1 makes the voltage across resistor R2 2.5V. Dividing 2.5V by the resistance of R2 gives the current of the self-test coil. When the input trigger pin voltage is less than 0.2V or is open-circuited, no current is generated in the branch, and the self-test exits. The self-test circuit generates a certain current, which is detected by the detection circuit. By comparing the detection results, it is determined whether the detection circuit is in normal working condition. When the detection circuit is confirmed to be in normal working condition, leakage current detection can be performed using the detection circuit, thus improving safety. Figure 2 The resistance value of R2 is fixed, therefore the self-test current generated is also fixed. The test result can be compared with the value given by the program to determine if the test is correct. For example, if the resistance of R2 is 1kΩ, 2.5V / 1kΩ = 2.5mA. If the program gives a value of 2.5mA, comparing the detected value with the program's given value of 2.5mA will determine if the circuit is functioning correctly.

[0043] In some embodiments, the oscillation unit includes: an oscillation module (such as...) Figure 2 The 555 timer and its peripheral circuit shown), sampling resistor module (such as...) Figure 2 The resistor R6 is shown.

[0044] Wherein, the secondary winding is connected with the oscillation module, and constitutes a self-excited oscillator; the same name end of the secondary winding is connected with the first connecting end of the sampling resistance module; the second connecting end of the sampling resistance module is connected with the oscillation module and grounded; the first connecting end of the sampling resistance module is also connected with the filter unit; the oscillation module is also connected with the protection unit.

[0045] In the scheme of the utility model, when the leakage current appears in the grid side converter (such as frequency converter, energy storage converter, etc.), the high-frequency oscillation signal is generated on the secondary winding of the leakage current detection mutual inductor (such as the current transformer T1 shown in the figure) by the 555 timer constructed oscillation circuit, and is reflected to the primary winding of the leakage current detection mutual inductor (such as the current transformer T1 shown in the figure), and the primary winding of the leakage current detection mutual inductor (such as the current transformer T1 shown in the figure) becomes the carrier signal of the low-frequency leakage current, and the low-frequency leakage current is transmitted to the secondary side of the leakage current detection mutual inductor (such as the current transformer T1 shown in the figure), and the low-frequency leakage current signal can be obtained after the high-frequency oscillation signal is filtered by the low-pass filter, and then is sent to the AD sampling channel of the controller MCU after the sampling conditioning circuit, and then the corresponding calculation, logic judgment and protection function are realized by software, and the safety is improved. Figure 2 Figure 2 Figure 2

[0046] In some embodiments, the oscillation module comprises a timing module (such as the 555 timer shown in the figure), a first operational amplifier module (such as the operational amplifier U1 shown in the figure), a second switch tube module (such as the triode Q2 shown in the figure) and a third switch tube module (such as the triode Q3 shown in the figure). Figure 2 Figure 2 Figure 2 Figure 2

[0047] ​​​​​​​The same name end of the secondary winding is connected to the ground pin of the timing module through the sampling resistance module; the same name end of the secondary winding and the common end of the sampling resistance 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 resistance module are connected to the input end of the filter unit as the output end of the oscillation unit. The different 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 non-inverting input end of the first operational amplifier module; the inverting input end of the first operational amplifier module is used for receiving a preset reference voltage signal; the output end of the first operational amplifier module is respectively connected to the control end (such as the base of the triode Q2) of the second switch tube module and the control end (such as the base of the triode Q3) of the third switch tube module. A preset second direct current power supply (such as a 12V direct current power supply) is connected to the first connection end (such as the collector of the triode Q2) of the second switch tube module; the second connection end (such as the emitter of the triode Q2) of the second switch tube module is connected to the first connection end (such as the emitter of the triode Q3) of the third switch tube module; a preset third direct current power supply (such as a -12V direct current power supply) is connected to the second connection end (such as the collector of the triode Q3) of the third switch tube module; the second connection end (such as the emitter of the triode Q2) of the second switch tube module is also respectively connected to the different name end of the secondary winding and the input end of the protection unit.

[0048] In Figure 2In the example shown, the oscillation circuit includes: resistor R3, resistor R4, resistor R5, resistor R6, capacitor C1, transistor Q2, transistor Q3, 555 timer, operational amplifier U1. Among them, the same name end of the secondary winding of the current transformer T1 is connected to ground through resistor R6; the 12V power supply is connected to ground through capacitor C1, the ground pin (such as GND pin) of the 555 timer is grounded, and the power supply pin (such as 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 DS pin) of the 555 timer and the threshold pin (such as 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 TR pin) of the 555 timer; the reset pin (such as 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 O pin) of the 555 timer is connected to the non-inverting input terminal of the operational amplifier U1 through resistor R3; the inverting input terminal of the operational amplifier U1 is connected to ground through resistor R4; the power supply end of the operational amplifier U1 is connected to the 12V power supply, the ground end of the operational amplifier U1 is connected to the -12V power supply, and the ground end of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U1 through resistor R5. The output end 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 name end of the secondary winding of the current transformer T1.

[0049] In Figure 2 In the leakage current detection and self-checking circuit shown, the transistors Q2 and Q3 in the oscillation circuit are NPN and PNP transistors, respectively. Assuming that the OUT pin (i.e., O pin) of the 555 timer outputs a high level, at this time the transistor Q2 is turned on and the transistor Q3 is turned off, and the midpoint voltage of the transistors Q2 and Q3 is +12V, which will charge the secondary coil of the leakage current detection transformer (such as the current transformer T1 shown in Figure 2 When the secondary coil of the leakage current detection transformer (such as the current transformer T1 shown in Figure 2 is forward charged to a saturation state, the secondary coil of the leakage current detection transformer (such as the current transformer T1 shown in Figure 2The current in the secondary coil of the current transformer T1 (shown) rises, causing a sudden increase in the voltage across resistor R6. This results in the voltages at the THR and TR pins of the 555 timer increasing and exceeding 8V. The secondary coil undergoes a charging process, similar to the charging process of an inductor. Before full charging, the current changes slowly; after full charging, the coil can be considered short-circuited, causing a sudden increase in current and the rise. Since the THR and TR pins of the 555 timer are the inputs of the internal comparator, the OUT pin of the 555 timer outputs a low level, and the output of operational amplifier U1 also outputs a low level. At this time, transistor Q2 is off, and transistor Q3 is on. The midpoint voltage between transistors Q2 and Q3 becomes −12V. The leakage current detection transformer (such as…)… Figure 2 The secondary coil of the current transformer T1 shown is reverse-charged, thus causing the leakage current detection transformer (such as...) to... Figure 2 The current transformer T1 shown is always in the detection state. When the leakage current detection transformer (such as...) Figure 2 When leakage current occurs in the circuit containing the current transformer T1 shown, the leakage current signal can be detected quickly. When the ground wire 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 induced from the primary side to the secondary side by the current transformer, and after passing through the conditioning circuit, it will be input to the MCU and thus be detected.

[0050] Similarly, when the leakage current detection transformer (such as...) Figure 2 When the secondary coil of the current transformer T1 shown is reverse charged to saturation, 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 transistors Q2 and Q3 becomes +12V again.

[0051] 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, and the voltage comparisons on the THR and TR pins 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 a high or low level based on the voltage comparison between the THR pin, TR pin, and CV pin. Please refer to the table below for details.

[0052]

[0053] In this invention, the system comprises a 555 timer, an operational amplifier U1, transistors Q2 and Q3, and a leakage current detection transformer (such as...). Figure 2The secondary coil of the current transformer T1 shown constitutes a self-excited oscillator. The widths of the positive and negative pulses of the self-excited oscillator are the same, and it is easy to know that the self-excited oscillation frequency of this oscillator is similar to that of the leakage current detection transformer (such as...). Figure 2 The current transformer T1 shown has core saturation characteristics, and the leakage current detection resistor (such as resistor R6) is related to the magnitude of the leakage current. However, once the oscillation circuit is determined, the oscillation frequency is only related to the magnitude of the leakage current. Resistor R6 is used to convert the leakage current signal into a voltage signal.

[0054] In some embodiments, the filtering unit includes: a second operational amplifier module (e.g., Figure 2 The operational amplifier U2 shown), and the two-stage RC filter module (such as...) Figure 2 The circuit shown consists of a two-stage RC filter circuit composed of resistors R9 and R10, capacitors C3 and C4, and a third operational amplifier module (such as...). Figure 2 The operational amplifier U3 mentioned above.

[0055] Wherein, the output terminal of the leakage current sampling signal of the oscillation unit, such as Figure 2 The common terminal of resistor R6 and the corresponding terminal of the secondary winding, i.e., the corresponding terminal of the secondary winding, can be connected to the non-inverting input terminal of the second operational amplifier module; the inverting input terminal of the second operational amplifier module is connected to the output terminal of the second operational amplifier module; the output terminal of the second operational amplifier module, after passing through the two-stage RC filter module, can be connected to the non-inverting input terminal of the third operational amplifier module; the inverting input terminal of the third operational amplifier module is connected to the output terminal of the third operational amplifier module; the output terminal of the third operational amplifier module is connected to the input terminal of the conditioning unit (e.g., ...). Figure 2 The resistor R11 shown is connected to the common terminal of operational amplifier U3.

[0056] exist Figure 2In the shown example, the low-pass filter circuit comprises: resistor R7, resistor R8, resistor R9, resistor R10, capacitor C2, capacitor C3, capacitor C4, operational amplifier U2, operational amplifier U3. The same name end of the secondary winding of the current transformer T1 is connected to the non-inverting input terminal of the operational amplifier U2 through the resistor R7 and the resistor R8; the non-inverting input terminal of the operational amplifier U2 is grounded through the capacitor C2; the inverting input terminal of the operational amplifier U2 is grounded; the inverting input terminal of the operational amplifier U2 is also connected to the output terminal of the operational amplifier U2; the power supply terminal of the operational amplifier U2 is connected to the 12V power supply, and the ground terminal of the operational amplifier U2 is grounded. The output terminal of the operational amplifier U2 is connected to the non-inverting input terminal of the operational amplifier U3 through the resistor R9 and the resistor R10; the non-inverting input terminal of the operational amplifier U3 is grounded through the capacitor C3; the inverting input terminal of the operational amplifier U3 is grounded; the inverting input terminal of the operational amplifier U3 is connected to the output terminal of the operational amplifier U3, the ground terminal of the operational amplifier U3 is grounded, and the power supply terminal of the operational amplifier U3 is connected to the 12V power supply. The common terminal of the resistor R9 and the resistor R10 is connected to the output terminal of the operational amplifier U3 through the capacitor C4. The output terminal of the operational amplifier U3 is connected to the sampling and conditioning circuit, and the output terminal of the operational amplifier U3 is connected to the input terminal of the sampling and conditioning circuit. Preferably, the inverting input terminal of the operational amplifier U3 is grounded through the resistor R23, and the inverting input terminal of the operational amplifier U3 is connected to the output terminal of the operational amplifier U3 through the resistor R24.

[0057] In Figure 2The shown leakage current detection and self-checking circuit, low pass filter circuit, resistance R8, resistance R21, resistance R22 and operational amplifier U2 constitute a same phase proportional amplification circuit, resistance R8, resistance R7, capacitor C2, capacitor C8 constitute two-stage RC filter circuit. A negative feedback circuit (i.e. 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, and the polarity of the negative feedback circuit will change at different frequency bands. When the frequency f of the self-oscillator is greater than the cut-off frequency fc, the two-stage RC filter circuit is shifted to -180 degrees, so that the phase of the input voltage and the output voltage of the negative feedback circuit is opposite. At this time, the feedback of 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, and the negative feedback acting on the inverting input end of the operational amplifier U2 makes the input signal decrease, and at the same time, the voltage amplification multiple of the operational amplifier U2 decreases, so the amplitude-frequency characteristic of the two-order low pass active filter rapidly attenuates in the high frequency band, and only low frequency signals can pass through. For the input voltage and output voltage of the same operational amplifier, each stage of RC brings 90 degrees of phase shift, and two stages are 180 degrees of phase shift. When negative feedback, the net input decreases, that is, the input minus the feedback equals the net input, and at the same time, the negative feedback makes the amplification multiple decrease. In the scheme of the utility model, two two-order low pass active filters with the same structure are adopted to realize the high frequency carrier signal generated by the self-oscillation circuit, so as to obtain the low frequency leakage current detection signal. The sampling 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 is retained through the low pass filter circuit and can be transmitted into the MCU.

[0058] In some embodiments, the protection unit comprises: a first capacitor module (such as Figure 2 the capacitor C6 shown), a second capacitor module (such as Figure 2 the capacitor C7 shown), a diode module (such as Figure 2 the diode D2 shown), a bleeder resistor module (such as Figure 2 resistors R16 and R17 shown), a fourth switch tube module (such as Figure 2 the switch tube Q4 shown), a third current limiting resistor module (such as Figure 2 the resistor R18 shown), and a fourth current limiting resistor module (such as Figure 2 the resistor R19 shown).

[0059] The opposite end of the secondary winding is connected to the anode of the diode module through the first capacitor module. The anode of the diode module and the cathode of the diode module are connected to ground through the discharge resistor module, respectively. The cathode of the diode module is connected to the control end of the fourth switch tube (e.g. the base of the transistor Q4) through the third current-limiting resistor module and the fourth current-limiting resistor module. The first connection end of the fourth switch tube (e.g. the collector of the transistor Q4) is connected to the fourth DC power supply (e.g. 3V DC power supply) and is also connected to the input end of the conditioning unit as the output end of the protection unit. The second connection end of the fourth switch tube (e.g. the emitter of the transistor Q4) is connected to ground.

[0060] In Figure 2 In the example shown, the differential protection circuit includes: resistors R16, R17, R18, R19, R20, capacitors C6, C7, a diode D2, and a transistor Q4. The opposite end of the secondary winding of the current transformer T1 is connected to ground through the capacitor C6 and the resistor R16. The common end of the capacitor C6 and the resistor R16 is connected to the anode of the diode D2. The cathode of the diode D2 is connected to ground through the resistor R17 and also connected to ground through the resistor R18 and the capacitor C7. The common end of the resistor R18 and the capacitor C7 is connected to the base of the transistor Q4 through the resistor R19. The 3V power supply is connected to the collector of the transistor Q4 through the resistor R20, and the emitter of the transistor Q4 is connected to ground. The collector of the transistor Q4 is connected to the input end of the sampling and conditioning circuit.

[0061] In Figure 2 In the example shown, the differential protection circuit includes: resistors R16, R17, R18, R19, R20, capacitors C6, C7, a diode D2, and a transistor Q4. The opposite end of the secondary winding of the current transformer T1 is connected to ground through the capacitor C6 and the resistor R16. The common end of the capacitor C6 and the resistor R16 is connected to the anode of the diode D2. The cathode of the diode D2 is connected to ground through the resistor R17 and also connected to ground through the resistor R18 and the capacitor C7. The common end of the resistor R18 and the capacitor C7 is connected to the base of the transistor Q4 through the resistor R19. The 3V power supply is connected to the collector of the transistor Q4 through the resistor R20, and the emitter of the transistor Q4 is connected to ground. The collector of the transistor Q4 is connected to the input end of the sampling and conditioning circuit. Figure 2The differential protection circuit shown mainly consists of capacitor C6, resistor R16, diode D2, resistor R18, resistor R19, capacitor C7, resistor R20, and NPN transistor Q4 and related circuitry. The high-frequency signal from the self-excited oscillator is transmitted to the anode of diode D2 via the differential capacitor (such as capacitor C6). Diode D2 and resistor R17 charge capacitor C7. Resistors R16 and R17 are the discharge resistors for capacitors C6 and C7, respectively. Resistor R18 is the current-limiting resistor for capacitor C7. Resistor R19 is the base current-limiting resistor for transistor Q4. +3V is the reference voltage. Resistors R20 and R11 have equal values, thus forming a 1.5V DC bias voltage at the non-inverting input of operational amplifier U4 in the sampling 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. Therefore, the charging time constant is determined by resistor R18 and capacitor C7. During the high-frequency negative pulse signal period in the self-excited oscillator, the energy in capacitor C7 is discharged through resistors R18 and R17. Therefore, the discharge time constant is determined by resistors R17, R18, and capacitor C7. Clearly, the discharge time of capacitor C7 is slower than its charging time. After capacitor C7 is charged, in the first-order zero-input response circuit, the instantaneous discharge of capacitor C7 is equivalent to a power source forming a loop with resistors R18 and R17 for discharge.

[0062] When the frequency of the self-oscillating circuit 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. In this case, a DC bias voltage of 1.5V is formed at the non-inverting input of operational amplifier U4 in the sampling conditioning circuit. When the frequency of the self-oscillation is high enough, the charging frequency of capacitor C7 becomes faster, so the energy charged by it during the high-frequency positive pulse cannot be fully discharged during the high-frequency negative pulse. This results in the voltage accumulated on capacitor C7 being sufficient to turn on transistor Q4, thereby pulling the non-inverting input of operational amplifier U4 in the sampling conditioning circuit down to 0 potential. It can be seen that the differential detection protection circuit (such as...) Figure 2 The differential protection circuit shown is used to determine whether to apply a DC bias voltage to the sampling conditioning circuit based on whether the frequency of the self-excited oscillator is high enough.

[0063] In some embodiments, the conditioning unit includes: a fifth current-limiting resistor module (e.g., Figure 2 The resistor R11 shown), the sixth current-limiting resistor module (as shown) Figure 2 The resistor R12 shown), RC setting module (such as...) Figure 2 Resistors R13, R14, and C5 are shown; the fourth operational amplifier module (as shown) Figure 2The shown operational amplifier U4, and the seventh current limiting resistor module (such as Figure 2 The shown resistor R15.

[0064] The output end of the shown filter unit (such as Figure 2 The output end of the shown operational amplifier U3), and the output end of the shown protection unit (such as Figure 2 The collector of the shown triode Q4), are connected to the inverting input end of the fourth operational amplifier module through the fifth current limiting resistor module; a preset fifth direct current power supply (such as a 1.5V direct current 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 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 through the seventh current limiting resistor module to output the leakage current detection signal to the control unit.

[0065] In Figure 2 The shown sampling conditioning circuit includes resistors R11, R12, R13, R14, R15, capacitor C5, and operational amplifier U4. The first connection end of resistor R11, as the input end of the sampling conditioning circuit, is connected to the output end of operational amplifier U3 and the collector of triode Q4. The second connection end of resistor R11 is connected to the inverting input end of operational amplifier U4; a 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 connected to the output end of operational amplifier U4 through parallel-connected resistor R14 and capacitor C5; and the output end of operational amplifier U4 is connected to the sampling end of MCU through resistor R15.

[0066] Figure 2 The sampling conditioning circuit in the shown example is an emitter follower composed of operational amplifier U4, and the non-inverting input end of operational amplifier U4 superimposes a low-frequency leakage current signal from the active low-pass filter (such as the low-pass filter circuit) and a direct current bias voltage signal determined by the differential detection protection circuit, and sends this superimposed signal to the AD sampling channel of the controller (such as MCU) through the output end of operational amplifier U4. The differential detection protection circuit mainly functions to protect the sampling conditioning circuit and MCU when a relatively large leakage current or short-circuit current appears in the leakage current detection circuit. A large leakage current or short-circuit current will generate a high voltage on resistor R6, and if there is no differential detection protection circuit, the high voltage will exceed the voltage resistance range of the subsequent circuit, resulting in damage to the device.

[0067] The technical scheme of the utility model discloses a leakage current detection transformer, a self-checking unit (such as a self-checking 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 power grid side of the power grid side converter, wherein: the first winding, the second winding, the third winding and the fourth winding in the original side winding of the leakage current detection transformer are connected between the power grid side and the converter, the fifth winding in the original side winding of the leakage current detection transformer is connected with the self-checking unit, the self-checking unit is used for generating a current with a certain value, so that the detection circuit composed of 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) detects based on the current with the certain value to determine whether the detection circuit is in a normal working state; the oscillation unit generates an oscillation signal on the auxiliary side winding to reflect on the original side winding to become a carrier signal of the leakage current, and then the carrier signal of the leakage current is transmitted to the auxiliary side winding to obtain a leakage current sampling signal; the filter 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, the conditioning unit performs conditioning output of the leakage current detection signal to the control unit based on the signal filtered by the filter unit and the protection signal of the protection unit, so that the control unit processes based on the leakage current detection signal; thereby, through detecting the leakage current on the ground wire of the detection power grid side converter or the power supply line connected with the power grid side, self-checking and protection can be realized, and safety is improved.

[0068] According to the embodiments of the utility model, a frequency converter corresponding to the leakage current detection device is also provided. The frequency converter can include the leakage current detection device described above.

[0069] Since the processing and functions realized by the frequency converter of the embodiments basically correspond to the embodiments, principles and examples of the device, the descriptions of the embodiments are not detailed, and the related descriptions in the foregoing embodiments are referred to, which will not be repeated here.

[0070] According to the embodiments of the utility model, a frequency converter corresponding to the leakage current detection device is also provided. The frequency converter can include the leakage current detection device described above.

[0071] Since the processing and functions realized by the energy storage converter of the embodiments basically correspond to the embodiments, principles and examples of the device, the descriptions of the embodiments are not detailed, and the related descriptions in the foregoing embodiments are referred to, which will not be repeated here.

[0072] According to the embodiments of the utility model, a leakage current detection method corresponding to the leakage current detection device is also provided, such as Figure 2The flowchart of an embodiment of the method of the utility model is shown. The leakage current detection method can include: step S110 to step S160.

[0073] At step S110, a constant current is generated by the self-checking unit 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-checking current through the fifth winding, so that the leakage current detection device detects based on the self-checking current to determine whether the leakage current detection device is in a preset working state (such as a normal working state), thereby realizing self-checking of the leakage current detection device.

[0074] At step S120, an oscillation signal is generated on the secondary winding by the oscillation unit in the case that the leakage current detection device is in the preset working state, so as to be reflected on the primary winding as a carrier signal of the leakage current, and then transmitted to the secondary winding to obtain a leakage current sampling signal.

[0075] At step S130, the leakage current sampling signal is filtered by the filtering unit to obtain a leakage current filtered signal.

[0076] At step S140, the leakage current sampling signal is protected by the protection unit to obtain a protection signal.

[0077] At step S150, the leakage current filtered signal and the protection signal are conditioned by 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.

[0078] At step S160, the grid-side converter is controlled based on the leakage current detection signal to realize leakage current protection of the grid-side converter.

[0079] In the scheme of the utility model, the leakage current detection and self-checking circuit can detect the leakage current on the ground wire or the power line connected to the grid side, can identify the size of the short-circuit current and the leakage current, and can solve the problem that the diameter of the three-phase incoming cable is too thick to pass through the leakage current detection device. In addition, the scheme of the utility model has a self-checking circuit and a protection circuit while detecting the leakage current, ensures the integrity of the current detection function, and improves the safety.

[0080] In some embodiments, the specific process of controlling the grid-side converter based on the leakage current detection signal to realize leakage current protection of the grid-side converter in step S160 is described in the following exemplary description.

[0081] The following will be described in combination with Figure 2An embodiment flow diagram of the method of the utility model is shown in the figure, which further illustrates the specific process of controlling the grid-side converter based on the leakage current detection signal in step S160, comprising: step S210 to step S240.

[0082] In step S210, it is determined whether the current value corresponding to the leakage current detection signal is less than the preset first current value and the duration is less than the preset first time.

[0083] In step S220, if it is determined that the condition is met, the sudden residual current of the grid-side converter is determined according to the leakage current detection signal.

[0084] In 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, the prompt message that the grid-side converter has a leakage current fault is initiated.

[0085] In step S240, until 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 after shutdown protection of the grid-side converter, if yes, the prompt message is cleared and the grid-side converter is restarted, otherwise the prompt message that the grid-side converter has a leakage current fault is continuously initiated; 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 150mA, the preset third current value is 60mA, the preset fourth current value is 30mA, the preset fifth current value is 50mA, the preset second time is 0.1s, and the preset third time is 5.5s.

[0086] Figure 2 The flow diagram of the leakage current detection and self-checking method of the utility model is shown in the figure. Figure 2 The leakage current detection and self-checking method comprises:

[0087] Step 1, 25mA self-checking and calculating 25mA coefficient, and then executing step 2. The resistance R2 is set to 1kΩ, 2.5V divided by the resistance R2 is multiplied by the number of turns 10 of the self-checking coil (fifth winding), and the current of the self-checking coil is 25mA.

[0088] Step 2, continuous residual current protection is performed to determine whether the continuous leakage current < 100 mA and the duration is not more than 0.2 s (seconds): if yes, step 21 is executed, otherwise step 3 is executed. Residual current and leakage current are just different names, residual current is called in standard NB / T+3200.

[0089] Step 21, the mutation residual current calculation is performed to obtain the mutation residual current (GFCI), and then step 22 is executed. Leakage current has three types: alternating sinusoidal, smooth direct current, and transient direct current. The mutation residual current belongs to transient direct current, that is, the current waveform is discontinuous.

[0090] Step 22, determine whether GFCI < 150 mA: if yes, step 23 is executed, otherwise step 3 is executed.

[0091] Step 23, determine whether GFCI ≥ 60 mA and Jump2_Fault < 0.1 s: if yes, step 24 is executed, otherwise step 3 is executed.

[0092] Step 24, determine whether GFCI ≥ 30 mA and Jump2_Fault < 0.2 s: if yes, step 25 is executed, otherwise step 3 is executed.

[0093] Among them, the leakage current is determined from large to small, and the leakage current values of different sizes and the time requirements of power grid disconnection are different, which can be seen from the example of the response time of the mutation current in the following table. Jump2_Fault represents the detection reaction time is not more than 0.2 s.

[0094]

[0095] Step 25, determine that the leakage current is normal, clear the relevant flag bit, and end the current detection.

[0096] Step 3, report error total protection position 1, and then execute step 31.

[0097] Step 31, after executing the leakage current protection, determine whether the leakage current effective value < 50 mA and the duration is 5.5 s: if yes, clear all faults and restart, otherwise report error to determine that there is a fault.

[0098] The functions of clearing relevant flags and setting the overall protection bit to 1 are pre-defined in the program. For example, if the flag "flag" is set, it will be set to 1 if the continuous leakage current is less than 100mA and does not exceed 0.2s; otherwise, it will be set to 0. The program uses the value of "flag" to make conditional judgments. The overall protection bit is also set in the program, and its value is determined by judging the status of other flags. For example, if both "flag" and "flag1" are equal to 1, the overall protection bit is set to 1; otherwise, it is set to 0.

[0099] In this invention, when leakage current occurs in the grid-side converter (such as a frequency converter, energy storage converter, etc.), a 555 timer is used to construct an oscillation circuit at 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, and reflected to the leakage current detection transformer (such as...). Figure 2 The primary winding of the current transformer T1 (shown) is used as a carrier signal for the low-frequency leakage current, which is then transmitted to the leakage current detection transformer (such as...). Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 Figure 2 The secondary side of the current transformer T1 shown can obtain a low-frequency leakage current signal after the high-frequency oscillation signal is filtered out by a low-pass filter. After passing through a sampling conditioning circuit, it is sent to the AD sampling channel of the controller MCU. Then, the software implements the corresponding calculation, logic judgment and protection functions to improve safety.

[0100] The solution of this invention can be applied to frequency converters and power conversion systems (PCS). The PCS controls the charging and discharging process of the battery, performs AC-DC conversion, and can directly supply power to AC loads in the absence of a power grid.

[0101] Since the processing and functions implemented by the method in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned frequency converter and energy storage converter, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0102] In summary, it is readily understood by those skilled in the art that, without conflict, the aforementioned advantageous methods can be freely combined and superimposed.

[0103] The above description is merely an embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of the claims of this utility model.

Claims

1. A leakage current detection device, characterized by, The application is applied to the detection of leakage current of grid-side converter from grid side; the leakage current detection device comprises a leakage current detection transformer, a self-checking unit, a filtering unit, an oscillation unit, a protection unit, a conditioning unit and a control unit; 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, the first winding, the second winding, the third winding and the fourth winding correspond to the lines of three-phase four-wire alternating current connected to 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 oscillation unit and the protection unit respectively; the filtering unit is connected to the oscillation unit, and the conditioning unit is connected to the filtering unit and the protection unit respectively; 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 current through the fifth winding, so that the leakage current detection device detects based on the self-checking 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 on the primary winding as a carrier signal of leakage current when the leakage current detection device is in a preset working state, and then transmit the carrier 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 protect based on the leakage current sampling signal to obtain a protection signal; the conditioning unit is used to condition 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 realize leakage current protection of the grid-side converter.

2. The leakage current detection device according to claim 1, characterized by the self-checking unit comprises a first current limiting resistor module, a second current limiting resistor module, a first switch tube module, a voltage stabilizing diode module and a protection module of the fifth winding; wherein, a preset first direct current source is connected to the same name end of the fifth winding after the protection module of the fifth winding; the different 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 the first current limiting resistor module; the second connection end of the first switch tube module is grounded after the second current limiting resistor module; the preset input trigger pin is also connected to the cathode of the voltage stabilizing diode module; the anode of the voltage stabilizing diode module is grounded; the control end of the voltage stabilizing 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 by the oscillation unit comprises an oscillation module and a sampling resistor module; wherein, the secondary winding is connected to the oscillation module to form a self-oscillator. The same name end of the secondary side winding is connected with the first connection end of the sampling resistance module; the second connection end of the sampling resistance module is connected with the oscillation module and grounded; The first connection end of the sampling resistance module is also connected with the filter unit; the oscillation module is also connected with the protection unit.

4. The leakage current detection device according to claim 3, characterized by The oscillation module comprises a timing module, a first operational amplifier module, a second switch tube module and a third switch tube module; wherein, The same name end of the secondary side winding is connected with the ground pin of the timing module through the sampling resistance module; the same name end of the secondary side winding and the common end of the sampling resistance module are respectively connected to the discharge pin of the timing module and the threshold value pin of the timing module; the same name end of the secondary side winding and the common end of the sampling resistance module are taken as the output end of the oscillation unit and connected with the input end of the filter unit; The different name end of the secondary side winding is connected with 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 for receiving 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 direct current 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 direct current 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 different name end of the secondary side winding and the input end of the protection unit.

5. The leakage current detecting apparatus according to claim 1 or 2, wherein The filter unit comprises a second operational amplifier module, a two-stage RC filter 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 through the two-stage RC filter 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 detecting apparatus according to claim 1 or 2, wherein The protection unit comprises a first capacitor module, a second capacitor module, a diode module, a discharge resistance module, a fourth switch tube module, a third current limiting resistance module and a fourth current limiting resistance module; wherein, The different name end of the secondary side winding is connected to the anode of the diode module through the first capacitor module; the anode of the diode module and the cathode of the diode module are respectively grounded through the discharge resistance module; the cathode of the diode module is connected to the control end of the fourth switch tube through the third current limiting resistance module and the fourth current limiting resistance module; A fourth preset direct current power source is capable of being connected to the first connection end of the fourth switch tube; the first connection end of the fourth switch tube, as an output end of the protection unit, is further connected to an input end of the conditioning unit; and the second connection end of the fourth switch tube is grounded.

7. The leakage current detecting apparatus according to claim 1 or 2, wherein The conditioning unit comprises 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 through the fifth current-limiting resistor module; a fifth preset direct current power source is capable of being 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 through the RC setting module; and the output end of the fourth operational amplifier module is capable of being connected to a sampling end of the control unit 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 The leakage current detection device comprises: The leakage current detection device according to any one of claims 1 to 7.

9. An energy storage converter, characterized by The leakage current detection device comprises: ​

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