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WO2025161807A1 - Onduleur et dispositif de détection de courant de fuite - Google Patents

Onduleur et dispositif de détection de courant de fuite

Info

Publication number
WO2025161807A1
WO2025161807A1 PCT/CN2024/144232 CN2024144232W WO2025161807A1 WO 2025161807 A1 WO2025161807 A1 WO 2025161807A1 CN 2024144232 W CN2024144232 W CN 2024144232W WO 2025161807 A1 WO2025161807 A1 WO 2025161807A1
Authority
WO
WIPO (PCT)
Prior art keywords
resistor
comparator
leakage current
voltage
source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/CN2024/144232
Other languages
English (en)
Chinese (zh)
Inventor
王昆
赵星
付明晓
张志宏
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Huawei Digital Power Technologies Co Ltd
Original Assignee
Huawei Digital Power Technologies Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Digital Power Technologies Co Ltd filed Critical Huawei Digital Power Technologies Co Ltd
Publication of WO2025161807A1 publication Critical patent/WO2025161807A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. DC/AC converters
    • H02H7/1225—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. DC/AC converters responsive to internal faults, e.g. shoot-through
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter

Definitions

  • the present application relates to the technical field of power supply detection, and in particular to an inverter and a leakage current detection device.
  • Leakage current is a common safety hazard in electrical equipment. It is often caused by ground faults, insulation damage, and aging of electrical equipment. It can lead to electrical accidents and threaten personal safety, equipment, and property. Therefore, the need for leakage current detection is becoming increasingly important.
  • Leakage current detection technology can effectively detect leakage current problems in electrical equipment, promptly identifying and addressing safety hazards.
  • various electrical equipment requires leakage current detection to ensure production safety and work efficiency; in the civilian field, household appliances also require leakage current detection to protect family members; and in the medical field, various medical devices also require leakage current detection to ensure the safety of medical procedures.
  • the first aspect is an inverter of the present application, comprising: an inverter circuit and a leakage current detection device; the inverter circuit is used to convert the received DC power into AC power and output it to the load; the leakage current detection device includes a positive DC source, a negative DC source, a leakage current transformer, a self-excited oscillation circuit, a sampling resistor and a controller.
  • the leakage current transformer may be an electrical component for detecting leakage current, wherein the leakage current transformer comprises a magnetic core and a detection winding wound around the magnetic core, wherein the magnetic core is sleeved on the power connection line.
  • a self-oscillating circuit is a circuit that generates an excitation signal (such as a square wave or rectangular signal) with a fixed frequency and alternating waveform.
  • the self-oscillating circuit includes a comparator, a first resistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a first switching transistor, and a second switching transistor.
  • the first power supply terminal of the comparator is connected to a positive DC source and one end of a first resistor, respectively.
  • the other end of the first resistor is connected to the output terminal of the comparator.
  • the second power supply terminal of the comparator is connected to a negative DC source.
  • the non-inverting input terminal of the comparator is connected to the first end of the detection winding.
  • the inverting input terminal of the comparator is connected to one end of the first voltage-dividing resistor and one end of the second voltage-dividing resistor, respectively.
  • the other end of the first voltage-dividing resistor is connected to the second end of the detection winding, and the other end of the second voltage-dividing resistor is grounded.
  • the output terminal of the comparator is connected to the driving terminal of the first switching tube and the driving terminal of the second switching tube.
  • the input end of the first switch tube is connected to the positive DC source, and the output end of the second switch tube is connected to the negative DC source; the output end of the first switch tube is respectively connected to the input end of the second switch tube and the second end of the detection winding.
  • sampling resistor One end of the sampling resistor is connected to the non-inverting input terminal of the comparator, and the other end of the sampling resistor is grounded.
  • the controller is configured to output a signal indicating leakage current on the power connection line when the integral value of the voltage across the sampling resistor in a single cycle is not zero.
  • the self-excited oscillation circuit of the present application drives the states of two switching tubes (i.e., the first switching tube and the second switching tube) through an active comparator, so that the two switching tubes switch back and forth between the on and off states, respectively, thereby loading an excitation signal with a fixed frequency and an alternating waveform into the detection winding of the leakage current transformer, causing the magnetic core to reciprocally magnetize and move towards saturation.
  • the sampling resistor is connected in series with the first end of the detection winding, so that the sampling signal at both ends of the sampling resistor can be the signal output by the detection winding under the internal magnetic field generated by the excitation signal.
  • the leakage current If there is no leakage current in the power connection line, there is no external magnetic field generated by the leakage current within the magnetic core, resulting in symmetry between the positive and negative half-cycles of the sampling signal waveform within the excitation cycle. If there is leakage current in the power connection line, the leakage current generates an external magnetic field. When the external magnetic field is in the same direction as the internal magnetic field, this accelerates the magnetic saturation of the magnetic core; when the external magnetic field is in the opposite direction, this delays the magnetic saturation of the core, resulting in asymmetry between the positive and negative half-cycles of the sampling signal waveform within the excitation cycle.
  • the presence of leakage current in the power connection line is determined by detecting whether the integral of the voltage across the sampling resistor within a single cycle is zero. If the integral of the voltage across the sampling resistor within a single cycle is not zero, leakage current is present in the power connection line.
  • This leakage current detection device can thus provide leakage current protection for the inverter, improving inverter safety.
  • the signal output by the comparator is a high level; if the input voltage of the non-inverting input terminal of the comparator is lower than the input voltage of the inverting input terminal of the comparator, the signal output by the comparator is a low level; if the signal output by the comparator is a high level, the first switch tube is in the off state and the second switch tube is in the on state; if the signal output by the comparator is a low level, the first switch tube is in the on state and the second switch tube is in the off state.
  • the relationship between the input voltage at the comparator's non-inverting input and the input voltage at its inverting input determines whether the comparator's output signal is high or low.
  • the comparator's output signal then drives the states of the first and second switching transistors, causing them to switch back and forth between on and off states, respectively.
  • the two switching transistors are not turned on at the same time, thereby applying a fixed-frequency, alternating waveform excitation signal to the detection winding of the leakage current transformer, causing the magnetic core to reciprocate and magnetize toward saturation.
  • the self-excited oscillation circuit further includes a first current limiting resistor and a second current limiting resistor; the input end of the first switching tube is connected to the positive DC source through the first current limiting resistor; and the output end of the second switching tube is connected to the negative DC source through the second current limiting resistor.
  • the first current limiting resistor is used to limit the current flowing to the first switching tube to ensure the working performance of the first switching tube
  • the second current limiting resistor is used to limit the current flowing to the second switching tube to ensure the working performance of the second switching tube.
  • the self-excited oscillation circuit also includes a third current limiting resistor and a fourth current limiting resistor; the output end of the first switching tube is connected to one end of the third current limiting resistor, and the input end of the second switching tube is connected to one end of the fourth current limiting resistor; the other end of the third current limiting resistor is respectively connected to the other end of the fourth current limiting resistor and the second end of the detection winding.
  • the third current limiting resistor is used to limit the current flowing to the first switch tube to ensure the working performance of the first switch tube
  • the fourth current limiting resistor is used to limit the current flowing to the second switch tube to ensure the working performance of the second switch tube.
  • the self-excited oscillation circuit also includes a first diode and a second diode; the positive terminal of the first diode is respectively connected to the negative terminal of the second diode and the second end of the detection winding, and the negative terminal of the first diode is connected to the positive DC source; the positive terminal of the second diode is connected to the negative DC source.
  • the induced current can be introduced into the positive DC source VCC through the first diode and the second diode, thereby preventing the induced current from damaging the components in the self-excited oscillation circuit.
  • the self-excited oscillation circuit further includes a second resistor; the output end of the comparator is connected to one end of the second resistor, and the other end of the second resistor is respectively connected to the driving end of the first switching tube and the driving end of the second switching tube.
  • the self-excited oscillation circuit further includes a third resistor; the non-inverting input terminal of the comparator is connected to one end of the third resistor, and the other end of the third resistor is respectively connected to the first end of the detection winding and one end of the sampling resistor.
  • the driving end of the first switching tube is the gate of the PMOS tube, the input end of the first switching tube is the source of the PMOS tube, and the output end of the first switching tube is the drain of the PMOS tube;
  • the driving end of the second switching tube is the gate of the N-channel metal oxide semiconductor NMOS tube, the input end of the second switching tube is the drain of the NMOS tube, and the output end of the second switching tube is the source of the NMOS tube.
  • the comparator output signal when the comparator output signal is high, the PMOS transistor is in the off state and the NMOS transistor is in the on state; when the comparator output signal is low, the PMOS transistor is in the on state and the NMOS transistor is in the off state.
  • the comparator output signal drives the states of the PMOS transistor and the NMOS transistor, causing the PMOS transistor and the NMOS transistor to switch back and forth between the on and off states, respectively.
  • the inverter further includes a switching circuit, which is provided on the power connection line; the controller is further configured to input a signal for controlling the switching circuit to disconnect when there is a leakage current signal on the power connection line.
  • the switch circuit is provided on the power connection line, when there is a leakage current signal on the power connection line, the switch circuit is turned off to prevent the leakage current from affecting the circuit on the power connection line.
  • the second aspect of the present application is a leakage current detection device, comprising: a positive DC source, a negative DC source, a leakage current transformer, a self-excited oscillation circuit, a sampling resistor, and a controller.
  • the leakage current transformer includes a magnetic core and a detection winding wound around the magnetic core, and the magnetic core is sleeved on the power connection line.
  • the self-excited oscillation circuit includes a comparator, a first resistor, a first voltage-dividing resistor, a second voltage-dividing resistor, a first switching tube, and a second switching tube.
  • the first power supply terminal of the comparator is respectively connected to a positive DC source and one end of a first resistor, the other end of the first resistor is connected to the output terminal of the comparator, and the second power supply terminal of the comparator is connected to a negative DC source;
  • the non-inverting input terminal of the comparator is connected to the first end of the detection winding;
  • the inverting input terminal of the comparator is respectively connected to one end of a first voltage-dividing resistor and one end of a second voltage-dividing resistor, the other end of the first voltage-dividing resistor is connected to the second end of the detection winding, and the other end of the second voltage-dividing resistor is grounded;
  • the output terminal of the comparator is respectively connected to the driving end of the first switching tube and the driving end of the second switching tube.
  • the input end of the first switching tube is connected to the positive DC source, and the output end of the second switching tube is connected to the negative DC source; the output end of the first switching tube is respectively connected to the input end of the second switching tube and the second end of the detection winding; one end of the sampling resistor is connected to the non-inverting input end of the comparator, and the other end of the sampling resistor is grounded.
  • the controller is used to output a signal that there is leakage current on the power connection line when the integral value of the voltage across the sampling resistor in a single cycle is not 0.
  • the waveform of the sampling signal when there is no leakage current on the power connection line, the waveform of the sampling signal is symmetrical between the positive and negative half-cycles within the excitation cycle, making the integral value of the voltage across the sampling resistor within a single cycle zero.
  • the waveform of the sampling signal is asymmetrical between the positive and negative half-cycles within the excitation cycle, and the integral value of the voltage across the sampling resistor within a single cycle is not zero, that is, the voltage amplitude is not zero.
  • the voltage amplitude difference can be mapped to the leakage current, and this mapping relationship can be obtained in advance through experimental measurements. Furthermore, the larger the voltage amplitude difference, the larger the leakage current; the smaller the voltage amplitude difference, the smaller the leakage current. Ultimately, once a voltage amplitude difference is obtained, the leakage current can be determined based on the voltage amplitude difference and the mapping relationship.
  • the signal output by the comparator is a high level; if the input voltage of the non-inverting input terminal of the comparator is lower than the input voltage of the inverting input terminal of the comparator, the signal output by the comparator is a low level; if the signal output by the comparator is a high level, the first switch tube is in the off state and the second switch tube is in the on state; if the signal output by the comparator is a low level, the first switch tube is in the on state and the second switch tube is in the off state.
  • the relationship between the input voltage at the comparator's non-inverting input and the input voltage at its inverting input determines whether the comparator's output signal is high or low.
  • the comparator's output signal then drives the states of the first and second switching transistors, causing them to switch back and forth between on and off states, respectively.
  • the two switching transistors are not turned on at the same time, thereby applying a fixed-frequency, alternating waveform excitation signal to the detection winding of the leakage current transformer, causing the magnetic core to reciprocate and magnetize toward saturation.
  • the self-excited oscillation circuit further includes a first current limiting resistor and a second current limiting resistor; the input end of the first switching tube is connected to the positive DC source through the first current limiting resistor; and the output end of the second switching tube is connected to the negative DC source through the second current limiting resistor.
  • the first current limiting resistor is used to limit the current flowing to the first switching tube to ensure the working performance of the first switching tube
  • the second current limiting resistor is used to limit the current flowing to the second switching tube to ensure the working performance of the second switching tube.
  • the self-excited oscillation circuit also includes a third current limiting resistor and a fourth current limiting resistor; the output end of the first switching tube is connected to one end of the third current limiting resistor, and the input end of the second switching tube is connected to one end of the fourth current limiting resistor; the other end of the third current limiting resistor is respectively connected to the other end of the fourth current limiting resistor and the second end of the detection winding.
  • the third current limiting resistor is used to limit the current flowing to the first switch tube to ensure the working performance of the first switch tube
  • the fourth current limiting resistor is used to limit the current flowing to the second switch tube to ensure the working performance of the second switch tube.
  • the self-excited oscillation circuit also includes a first diode and a second diode; the positive terminal of the first diode is respectively connected to the negative terminal of the second diode and the second end of the detection winding, and the negative terminal of the first diode is connected to the positive DC source; the positive terminal of the second diode is connected to the negative DC source.
  • the induced current can be introduced into the positive DC source VCC through the first diode and the second diode, thereby preventing the induced current from damaging the components in the self-excited oscillation circuit.
  • the self-excited oscillation circuit further includes a second resistor; the output end of the comparator is connected to one end of the second resistor, and the other end of the second resistor is respectively connected to the driving end of the first switching tube and the driving end of the second switching tube.
  • the self-excited oscillation circuit further includes a third resistor; the non-inverting input terminal of the comparator is connected to one end of the third resistor, and the other end of the third resistor is respectively connected to the first end of the detection winding and one end of the sampling resistor.
  • the driving end of the first switching tube is the gate of the PMOS tube, the input end of the first switching tube is the source of the PMOS tube, and the output end of the first switching tube is the drain of the PMOS tube;
  • the driving end of the second switching tube is the gate of the N-channel metal oxide semiconductor NMOS tube, the input end of the second switching tube is the drain of the NMOS tube, and the output end of the second switching tube is the source of the NMOS tube.
  • the comparator output signal when the comparator output signal is high, the PMOS transistor is in the off state and the NMOS transistor is in the on state; when the comparator output signal is low, the PMOS transistor is in the on state and the NMOS transistor is in the off state.
  • the comparator output signal drives the states of the PMOS transistor and the NMOS transistor, causing the PMOS transistor and the NMOS transistor to switch back and forth between the on and off states, respectively.
  • FIG1 is a schematic diagram of the architecture of a photovoltaic energy storage system according to an embodiment of the present application.
  • FIG2 is a schematic structural diagram of a leakage current detection circuit according to an embodiment of the present application.
  • FIG3 is a structural diagram illustrating a circuit loop of a leakage current detection circuit according to an embodiment of the present application
  • FIG4 is a structural diagram illustrating a circuit loop of another leakage current detection circuit according to an embodiment of the present application.
  • FIG5 is a structural example diagram of a voltage waveform at point B and a voltage waveform across resistor R1 according to an embodiment of the present application;
  • FIG6 is a structural example diagram of a voltage waveform at point B and a voltage waveform across resistor R1 according to another embodiment of the present application;
  • FIG. 7 to 15 are schematic structural diagrams of another leakage current detection circuit according to an embodiment of the present application.
  • FIG16 is a schematic structural diagram of another leakage current detection device according to an embodiment of the present application.
  • FIG17 is a schematic structural diagram of an inverter according to an embodiment of the present application.
  • FIG18 is a schematic structural diagram of another inverter according to an embodiment of the present application.
  • a and/or B can represent the following three situations: “A”, “B”, and "A and B”.
  • a and B can be singular or plural.
  • the symbol "/" can indicate that the preceding and following objects are in an "or” relationship.
  • the symbol “/” can also represent a division sign, that is, performing a division operation.
  • A/B can mean A divided by B.
  • At least one item or similar expressions refers to any combination of these items, including any combination of single items or plural items, and refers to one or more, and “multiple” refers to two or more.
  • at least one item among a, b or c can represent the following seven situations: “a”, “b”, “c”, “a and b”, “a and c", “b and c", "a, b and c".
  • each of a, b, and c can be an element or a set containing one or more elements.
  • Coupled and “connection” can be used to indicate electrical connection, which can include direct connection through wires or connectors or indirect connection through other devices (such as inductors, capacitors, or resistors). Therefore, “coupling” and “connection” can be regarded as a broad sense of electronic communication connection.
  • the mutual coupling/direct coupling/connection shown or discussed can be indirect coupling or connection through some interface, device, unit or device, which can be in the form of communication, electrical or other forms.
  • circuits or other components in the embodiments of the present application may be described as being “configured to” perform one or more tasks.
  • “configured to” may imply a structure by indicating that the circuit/component includes a structure (e.g., circuitry) that performs the one or more tasks during operation. Thus, even when a specified circuit/component is not currently operational, the circuit/component may be said to be configured to perform the task.
  • Circuits/components used with the term “configured to” include hardware, such as circuits that perform an operation, etc.
  • Leakage current is one of the common safety hazards in electrical equipment. It is usually caused by ground faults, insulation damage, aging of electrical appliances, etc., which may lead to electrical accidents and threaten personal safety and equipment property. Therefore, the demand for leakage current detection is becoming increasingly important. Based on this, this embodiment requires leakage current detection of electrical equipment.
  • electrical equipment may include power supply equipment, charging equipment, uninterruptible power supply (UPS), or inverter, etc.
  • the photovoltaic energy storage system 10 includes a photovoltaic string 110, an inverter 120, and a load 130.
  • the inverter 120 includes an inverter circuit 1201 and a leakage current detection device 1202.
  • the photovoltaic string 110 refers to a circuit unit formed by connecting several photovoltaic modules (usually photovoltaic cells of the same specifications) in series in a photovoltaic energy storage system.
  • the inverter circuit 1201 is a circuit that converts direct current into alternating current by controlling switching tubes (such as transistors and switching tubes) and outputs the alternating current to the load 130.
  • the leakage current detection device 1202 is a device that detects leakage current.
  • the load 130 may include various electrical devices or an AC power grid. In this way, the leakage current detection device 1202 provides leakage current protection for the inverter 120, thereby improving the safety of the inverter 120.
  • leakage current detection circuit The leakage current detection circuit, the leakage current detection device, and the electrical equipment where the leakage current detection circuit is located are described in detail below.
  • the leakage current detection circuit may include a leakage current transformer, a self-excited oscillation circuit, and a sampling resistor.
  • a leakage current transformer is an electrical component used to detect leakage current. It typically consists of a primary winding, a secondary winding, and a magnetic core.
  • the primary winding can be made up of the power connection wires of the electrical device.
  • One end of the secondary winding is connected to a self-excited oscillation circuit, and the magnetic core senses the magnetic field generated by the leakage current of the electrical device.
  • the secondary winding can also be called a detection winding.
  • a self-excited oscillator circuit is a circuit that generates an excitation signal with a fixed frequency and alternating waveform (such as a square wave or rectangular signal).
  • a fixed frequency and alternating waveform such as a square wave or rectangular signal.
  • a sampling resistor is a passive component in a leakage current detection circuit, used to sample and measure physical quantities such as current and voltage. Its resistance can range from a few ohms to several hundred ohms.
  • the sampling resistor can be connected in series with the other end of the secondary winding. Furthermore, the sampled signal across the sampling resistor can be the signal output by the secondary winding in the presence of the inherent magnetic field generated by the excitation signal.
  • the waveform of the sampling signal is symmetrical in the positive and negative half cycles within the excitation cycle.
  • leakage current flows through a power line, it generates an external magnetic field.
  • the external magnetic field is in the same direction as the internal magnetic field, this accelerates the core's saturation.
  • the external magnetic field is in the opposite direction, it delays saturation. Consequently, the waveform of the sampling signal exhibits asymmetry between positive and negative directions within the excitation cycle. This indicates that the waveform of the sampling signal varies between the presence and absence of leakage current, making it suitable for detecting leakage current in power lines.
  • Figure 2 is a schematic diagram of the structure of a leakage current detection circuit according to an embodiment of the present application.
  • the leakage current detection circuit 20 includes a leakage current transformer 210, a self-excited oscillation circuit 220, and a resistor R1.
  • the resistor R1 is used as a sampling resistor to detect leakage current.
  • the leakage current transformer 210 includes a magnetic core 2101 and a detection winding 2102 wound around the magnetic core 2101.
  • the magnetic core 2101 is sleeved on the power connection line 230.
  • the first end of the detection winding 2102 is represented by point M, and the second end of the detection winding 2102 is represented by point N.
  • the self-excited oscillation circuit 220 includes a comparator U1 , a resistor R2 , a resistor R3 , a resistor R4 , a switch Q1 , and a switch Q2 .
  • the first power supply terminal of the comparator U1 is connected to the positive DC source VCC and one end of the resistor R2 respectively.
  • the other end of the resistor R2 is connected to the output terminal of the comparator U1.
  • the second power supply terminal of the comparator U1 is connected to the negative DC source -VCC.
  • the non-inverting input of comparator U1 is connected to the first end of detection winding 2102.
  • the inverting input of comparator U1 is connected to one end of resistor R3 and one end of resistor R4, respectively.
  • the other end of resistor R3 is connected to the second end of detection winding 2102, and the other end of resistor R4 is grounded to GND.
  • the output of comparator U1 is connected to the driving end of switch Q1 and the driving end of switch Q2, respectively.
  • the input end of the switch tube Q1 is connected to the positive DC source VCC, the output end of the switch tube Q2 is connected to the negative DC source -VCC, and the output end of the switch tube Q1 is connected to the input end of the switch tube Q2 and the second end of the detection winding 2102.
  • One end of the resistor R1 is connected to the non-inverting input terminal of the comparator U1, and the other end of the resistor R1 is grounded GND.
  • comparator U1 if the input voltage at the non-inverting input of comparator U1 (i.e., the voltage at point E) is higher than the input voltage at the inverting input of comparator U1 (i.e., the voltage at point D), the signal output by comparator U1 is a high level; if the input voltage at the non-inverting input of comparator U1 is lower than the input voltage at the inverting input of comparator U1, the signal output by comparator U1 is a low level.
  • switch Q1 and switch Q2 can be triodes, metal-oxide-semiconductor field-effect transistors (MOSFETs), or insulated gate bipolar transistors (IGBTs), etc., without specific limitation.
  • MOSFETs metal-oxide-semiconductor field-effect transistors
  • IGBTs insulated gate bipolar transistors
  • switch Q1 and switch Q2 can be P-channel Metal-Oxide-Semiconductor (PMOS) transistors, and switch Q2 can be N-channel Metal-Oxide-Semiconductor (NMOS) transistors.
  • the driving terminal of switch Q1 is the gate of the PMOS transistor, the input terminal of switch Q1 is the source of the PMOS transistor, and the output terminal of switch Q1 is the drain of the PMOS transistor.
  • the driving terminal of switch Q2 is the gate of the NMOS transistor, the output terminal of switch Q2 is the source of the NMOS transistor, and the input terminal of switch Q2 is the drain of the NMOS transistor.
  • the gate of the PMOS transistor is connected to the output terminal of comparator U1
  • the source of the PMOS transistor is connected to the positive DC source VCC
  • the drain of the PMOS transistor is connected to the drain of the NMOS transistor and the second terminal of detection winding 2102, respectively
  • the gate of the NMOS transistor is connected to the output terminal of comparator U1
  • the source of the NMOS transistor is connected to the negative DC source -VCC.
  • the following describes the working principles of the leakage current detection circuit 20 under the conditions of no leakage current and leakage current on the power connection line 230 .
  • the working principle of the leakage current detection circuit 20 is as follows:
  • positive DC source VCC provides positive DC power to the first power supply terminal of comparator U1 and the input terminal of switch Q1.
  • Negative DC source -VCC provides negative DC power to the second power supply terminal of comparator U1 and the output terminal of switch Q2.
  • positive DC source VCC generates a high level at point A through resistor R2.
  • the switch Q1 When a high level is generated at point A, the switch Q1 is turned off and the switch Q2 is turned on. At this time, the leakage current detection circuit 20 generates a circuit loop, and the voltages at points B and C are pulled to -VCC, as shown in FIG3 .
  • resistors R3 and R4 divide the voltage at point C (-VCC).
  • resistor R3 can be referred to as the "first voltage-dividing resistor” and resistor R4 can be referred to as the "second voltage-dividing resistor.”
  • the voltage at point D is -VCC*R4/(R3+R4).
  • the resistance of resistors R3 and R4 can be the same or different. When the resistance of resistors R3 and R4 is the same, the voltage at point D is -VCC/2.
  • the input voltage of the inverting input terminal of the comparator U1 is the voltage at point D
  • the input voltage of the non-inverting input terminal of the comparator U1 is the voltage at point E (ie, the voltage across the resistor R1 ).
  • resistors R3 and R4 divide the voltage (VCC) at point C. Assuming the resistance of resistors R3 and R4 is the same, the voltage at point D is VCC/2.
  • the current flowing through detection winding 2102 generates an internal magnetic field, and magnetic core 2101 gradually magnetizes within this internal magnetic field.
  • magnetic core 2101 magnetizes, the voltage at point E continuously increases from VCC/2 (or VCC/2 slightly greater) toward -VCC.
  • the voltage waveform of the self-excited oscillation circuit 220 at point B (or point C) and the voltage waveform across resistor R1 are shown in Figure 5.
  • the voltage waveform at point B is symmetrical between the positive and negative half-cycles during the excitation cycle
  • the voltage waveform across resistor R1 is also symmetrical between the positive and negative half-cycles during the excitation cycle.
  • the working principle of the leakage current detection circuit 20 is as follows:
  • Leakage current on power connection line 230 generates an external magnetic field.
  • leakage current detection circuit 20 When leakage current detection circuit 20 generates the circuit loop shown in Figure 3, current flows from the first end of detection winding 2102 to the second end of detection winding 2102. This current flowing through detection winding 2102 generates an internal magnetic field, gradually magnetizing magnetic core 2101 within the internal magnetic field. As magnetic core 2101 magnetizes, the voltage at point E continuously increases from 0 to -VCC.
  • leakage current detection circuit 20 When the voltage at point E quickly reaches near -VCC/2, the voltage at point E is lower than the voltage at point D, causing the output signal of comparator U1 to be low.
  • leakage current detection circuit 20 generates the circuit loop shown in Figure 4, with current flowing from the second end of detection winding 2102 to the first end of detection winding 2102. Because the direction of the current flowing through detection winding 2102 in Figure 4 is opposite to the direction of the current flowing through detection winding 2102 in Figure 3, the direction of the internal magnetic field generated by the current in Figure 4 is opposite to the direction of the internal magnetic field generated by the current in Figure 4. While the direction of the external magnetic field generated by the leakage current remains unchanged, the direction of the external magnetic field generated by the leakage current is opposite to the direction of the internal magnetic field at this time, which delays the magnetic core from reaching magnetic saturation.
  • the voltage waveform across the resistor R1 when there is no leakage current is also symmetrical in the positive and negative half-cycles during the excitation cycle, while the voltage waveform across the resistor R1 when there is leakage current is asymmetrical in the positive and negative half-cycles during the excitation cycle. In this way, the signal across the resistor R1 can be used to detect leakage current on the power connection line 230.
  • this embodiment can add additional components to improve the performance of the leakage current detection circuit.
  • this embodiment can add a current-limiting resistor in the path from the positive DC source VCC through the switch Q1 to point B to limit the current flowing to the switch Q1 and ensure the operating performance of the switch Q1; and/or add a current-limiting resistor in the path from the negative DC source -VCC through the switch Q2 to point B to limit the current flowing to the switch Q2 and ensure the operating performance of the switch Q2.
  • the self-excited oscillation circuit 220 also includes a resistor R5 and a resistor R6. Among them, the input end of the switch tube Q1 is connected to one end of the resistor R5, and the other end of the resistor R5 is connected to the positive DC source VCC, that is, the input end of the switch tube Q1 is connected to the positive DC source VCC through the resistor R5.
  • the output end of the switch tube Q2 is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the negative DC source -VCC, that is, the output end of the switch tube Q2 is connected to the negative DC source -VCC through the resistor R6.
  • the resistor R5 can be called the “first current limiting resistor” and the resistor R6 can be called the “second current limiting resistor.”
  • the current flowing to the switch tube Q1 is limited by the resistor R5 to ensure the working performance of the switch tube Q1
  • the current flowing to the switch tube Q2 is limited by the resistor R6 to ensure the working performance of the switch tube Q2.
  • the self-excited oscillation circuit 220 also includes resistors R7 and R8. Among them, the output end of the switch tube Q1 is connected to one end of the resistor R7, and the input end of the switch tube Q2 is connected to one end of the resistor R8. The other end of the resistor R7 is respectively connected to the other end of the resistor R8 and the second end of the detection winding 2102.
  • the resistor R7 can be referred to as the "third current-limiting resistor” and the resistor R8 can be referred to as the "fourth current-limiting resistor.”
  • the resistor R7 is used to limit the current flowing to the switch tube Q1 to ensure the working performance of the switch tube Q1
  • the resistor R8 is used to limit the current flowing to the switch tube Q2 to ensure the working performance of the switch tube Q2.
  • this embodiment can add some additional devices to protect the components within the leakage current detection circuit. Since the detection winding 2102 of the leakage current transformer 210 may be affected by an external magnetic field to generate an induced current, and the induced current flows along the detection winding 2102 to the self-oscillation circuit 220, the large induced current may damage the components within the self-oscillation circuit 220. Therefore, the hazards caused by the large induced current need to be considered.
  • the detection winding 2102 is subjected to an external magnetic field to generate a large induced current.
  • a diode can be connected to the second end of the detection winding 2102 so as to introduce the induced current into the positive DC source VCC through the diode, thereby preventing the induced current from damaging the components in the self-excited oscillation circuit 220.
  • the self-oscillation circuit 220 also includes a diode D1 and a diode D2.
  • the positive terminal of diode D1 is connected to the negative terminal of diode D2 and the second end of the detection winding 2102, respectively.
  • the negative terminal of diode D1 is connected to the positive DC source VCC, and the positive terminal of diode D2 is connected to the negative DC source -VCC.
  • diode D1 can be referred to as the "first diode” and diode D2 can be referred to as the "second diode.”
  • the induced current can be introduced into the positive DC source VCC through the diode D1 and the diode D2, thereby preventing the induced current from damaging the components in the self-excited oscillation circuit 220.
  • this embodiment can add additional components to improve the performance of the leakage current detection circuit.
  • this embodiment can add a resistor in the path from the output of comparator U1 to point A. This resistor can be used to control the conduction speed of switches Q1 and Q2. Thus, by adjusting the resistance of the resistor, the conduction speed of switch Q1 or Q2 can be ensured to be within the required range.
  • the self-excited oscillation circuit 220 further includes a resistor R9.
  • the output of the comparator U1 is connected to one end of the resistor R9, and the other end of the resistor R9 is connected to the driving end of the switch Q1 and the driving end of the switch Q2, respectively.
  • the resistor R9 may be referred to as the "second resistor.”
  • this embodiment can add some additional components to improve the performance of the leakage current detection circuit.
  • this embodiment can add a resistor in the path from the non-inverting input of comparator U1 to point E. This resistor can be used to limit the current flowing into comparator U1, thereby protecting comparator U1.
  • the self-excited oscillation circuit 220 further includes a resistor R10 , wherein the non-inverting input terminal of the comparator U1 is connected to one end of the resistor R10 , and the other end of the resistor R10 is connected to the first end of the detection winding 2102 and one end of the resistor R1 , respectively.
  • Solution 1 can be combined with “Solutions 2 to 5" to obtain a circuit topology for the leakage current detection circuit, thereby improving the operating performance of the leakage current detection circuit. For example, as shown in Figures 12 and 13, this will not be repeated here.
  • the self-excited oscillation circuit 220 of this embodiment needs to drive the states of the switch tubes Q1 and Q2 respectively to generate an excitation signal.
  • this embodiment directly drives the states of the switch tubes Q1 and Q2 through the signal output by the comparator U1. For example, if the signal output by the comparator U1 is high, the switch tube Q1 is in the off state and the switch tube Q2 is in the on state; if the signal output by the comparator U1 is low, the switch tube Q1 is in the on state and the switch tube Q2 is in the off state.
  • this embodiment can add an inverter on the path from the output of comparator U1 to point A, and use the output signal of the inverter to drive the states of switches Q1 and Q2.
  • the inverter can convert a high-level input to a low-level input or vice versa.
  • switch Q1 can be an NMOS transistor and switch Q2 can be a PMOS transistor.
  • an inverter is added to the leakage current detection circuit 20 shown in FIG2 , as shown in FIG14 .
  • the self-oscillation circuit further includes an inverter V1 .
  • the output of the comparator U1 is connected to the input of the inverter V1 , and the output of the inverter V1 is connected to the driving end of the switch tube Q1 and the driving end of the switch tube Q2 , respectively.
  • the leakage current detection device may include a positive DC source, a negative DC source, a leakage current detection circuit, and a controller.
  • the leakage current detection circuit includes a leakage current transformer, a self-excited oscillation circuit, and a sampling resistor.
  • the controller may be connected to one end of the sampling resistor in the leakage current detection circuit.
  • the circuit topology of the leakage current detection circuit can be the circuit topology mentioned in the above-mentioned various solutions, which will not be described in detail.
  • the filter circuit can be used to filter the sampling signal at both ends of the sampling resistor to obtain an output signal, and transmit the output signal to the calculation circuit.
  • the waveform of the sampled signal is symmetrical between the positive and negative half-cycles within the excitation cycle.
  • the voltage waveform across resistor R1 in Figure 5 is symmetrical between the positive and negative half-cycles within the excitation cycle. That is, the area of the waveform in the negative half-cycle is the same as the area in the positive half-cycle, making the integral value of the voltage across resistor R1 within a single cycle zero.
  • the voltage amplitude across resistor R1 is zero.
  • the waveform of the sampled signal becomes asymmetrical within the excitation cycle.
  • the voltage waveform across resistor R1 in Figure 5 exhibits asymmetrical polarity within the excitation cycle. This means that the area of the waveform during the negative half-cycle differs from the area during the positive half-cycle, causing the integral of the voltage across resistor R1 within a single cycle to be non-zero. Ideally, the voltage amplitude across resistor R1 will no longer be zero. This means that when leakage current is present, the voltage amplitude will differ compared to when there is no leakage current.
  • the voltage amplitude difference can be mapped to the leakage current, and this mapping relationship can be obtained in advance through experimental measurements. Furthermore, the larger the voltage amplitude difference, the larger the leakage current; the smaller the voltage amplitude difference, the smaller the leakage current. Thus, once a voltage amplitude difference is obtained, the leakage current can be determined based on the voltage amplitude difference and the aforementioned mapping relationship.
  • the leakage current detection device 1500 includes a positive DC source VCC, a negative DC source -VCC, the leakage current detection circuit 20, and a controller 1510.
  • One end of the resistor R1 is connected to the non-inverting input of the comparator U1, the controller 1510, and the first end of the detection winding 2102, respectively, and the other end of the resistor R1 is grounded.
  • the controller 1510 can be configured to output a signal indicating leakage current on the power connection line 230 when the integral value of the voltage across the resistor R1 within a single cycle is not zero (or in other words, the voltage amplitude across the resistor R1 is not zero). In this way, the leakage current detection device 1500 can detect whether there is leakage current on the power connection line 230 based on the voltage across the resistor R1.
  • the leakage current detection device may include a filter circuit, and the controller is connected to one end of the sampling resistor through the filter circuit.
  • the filter circuit may be used to filter the sampled signal across the sampling resistor to obtain an output signal, and transmit the output signal to the controller.
  • the leakage current detection device 1500 further includes a filter circuit 1610 .
  • One end of the resistor R1 is connected to the non-inverting input of the comparator U1, the input of the filter circuit 1610, and the first end of the detection winding 2102 , respectively, and the other end of the resistor R1 is grounded.
  • the output of the filter circuit 1610 is connected to the controller 1510 .
  • the filter circuit 1610 is used to filter the sampled signals at both ends of the resistor R1 to obtain an output signal.
  • the controller 1510 is used to determine whether there is a leakage current on the power connection line 230 based on whether the voltage amplitude of the output signal is 0. When the voltage amplitude of the output signal is 0, this indicates that there is no leakage current on the power connection line 230; when the voltage amplitude of the output signal is not 0, this indicates that there is a leakage current on the power connection line 230.
  • Solution 8 this embodiment specifically describes the inverter where the leakage current detection device is located.
  • the inverter may include an inverter circuit and a leakage current detection device.
  • An inverter circuit can be a circuit that converts a DC signal into an AC signal.
  • the inverter circuit's input is connected to a photovoltaic string, and its output is connected to a load via a power connection line.
  • the load can include an AC power grid.
  • the inverter 1700 includes an inverter circuit 1710 and the leakage current detection device 1500 .
  • the input end of the inverter circuit 1710 is connected to the photovoltaic string 1720
  • the output end of the inverter circuit 1710 is connected to the load 1730 via the power connection line 230 .
  • the inverter circuit 1710 is used to convert the received direct current into alternating current and output it to the load 1730 .
  • the leakage current detection device 1500 can provide leakage current protection for the inverter 1700, thereby improving the safety of the inverter 1700 .
  • the inverter further includes a switching circuit, which is disposed on the power connection line and connected to the controller.
  • the controller is further configured to input a signal to control the switching circuit to disconnect when a leakage current signal is detected on the power connection line.
  • inverter 1700 further includes a switching circuit 1810.
  • Switching circuit 1810 is provided on power connection line 230 and is connected to controller 1510.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

La présente demande se rapporte au domaine technique de la détection d'alimentation électrique, et concerne un onduleur et un dispositif de détection de courant de fuite. L'onduleur de la présente demande comprend un circuit onduleur et un dispositif de détection de courant de fuite, et le dispositif de détection de courant de fuite comprend une source de courant continu à électrode positive, une source de courant continu à électrode négative, un transformateur de courant de fuite, un circuit d'oscillation auto-excité, une résistance d'échantillonnage et un dispositif de commande. Le circuit d'oscillation auto-excité commande les états de deux transistors de commutation au moyen d'un comparateur actif, de telle sorte que les deux transistors de commutation sont respectivement commutés en va-et-vient entre un état activé et un état désactivé, et un signal d'excitation ayant une fréquence fixe et une forme d'onde alternative est généré. De plus, la résistance d'échantillonnage est connectée en série à une première extrémité d'un enroulement de détection du transformateur de courant de fuite, de telle sorte que la tension sous un champ magnétique interne généré par le signal d'excitation est échantillonnée aux deux extrémités de la résistance d'échantillonnage. Par conséquent, le courant de fuite sur une ligne de connexion électrique est détecté au moyen de la tension aux deux extrémités de la résistance d'échantillonnage, de telle sorte qu'une protection contre le courant de fuite peut être obtenue sur l'onduleur au moyen du dispositif de détection de courant de fuite, améliorant la sécurité de l'onduleur.
PCT/CN2024/144232 2024-01-29 2024-12-31 Onduleur et dispositif de détection de courant de fuite Pending WO2025161807A1 (fr)

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CN119355578A (zh) * 2024-12-26 2025-01-24 国网山东省电力公司青岛供电公司 一种用于电缆线的漏电流检测装置

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