A leakage locking control circuit for a high-voltage frequency converter

Abstract

The present invention discloses a leakage locking control circuit for a high-voltage frequency converter, which includes a controller, a high-voltage relay, and an insulation detection module. The main circuit of the high-voltage frequency converter includes an input transformer, multiple groups of serially connected power units, and a power-on mechanism; the high-voltage relay includes contacts with the same number as the power units. The first end of the high-voltage relay contact is connected to the corresponding power unit circuit, and the other end is connected to a common connection point. The coil of the high-voltage relay is connected to the controller; the insulation detection module includes a leakage sensor, a current source, and an excitation coil. The positive end of the circuit in which the current source is serially connected with the line excitation coil is connected to the controller, and the negative end is grounded; the excitation coil is coupled with the leakage sensor. The first end of the leakage sensor coil is connected to the common connection point, and the other end is grounded; the control end of the power-on mechanism is connected to the control signal output end of the controller. The structure of the present invention is simple, the loop loss is small, and it can monitor the leakage conditions of all power units of the high-voltage frequency converter, improving the safety of the equipment.

Description

[Technical field]

[0001] The invention relates to a high-voltage frequency converter, and in particular to a leakage locking control circuit of the high-voltage frequency converter. [Background Technology]

[0002] Cascaded high-voltage inverters have many power units and high operating voltage, which requires high insulation. The commonly used leakage lockout circuit is directly connected to the inverter power output terminal and connected to the motor. When used in high-voltage inverters, it is difficult to monitor the leakage of each power unit due to the tortuous circuit and large loss. [Summary of the invention]

[0003] The technical problem to be solved by the present invention is to provide a leakage blocking control circuit which has a simple structure, small loop loss and can monitor the leakage conditions of all power units of a high-voltage frequency converter.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is a leakage lockout control circuit of a high-voltage inverter, including a controller, a first high-voltage relay and an insulation detection module, the main circuit of the high-voltage inverter includes an input transformer, multiple groups of power units connected in series and a power-on mechanism; the first high-voltage relay includes contacts with the same number as the power units, the first end of the first high-voltage relay contact is connected to the corresponding power unit circuit, and the other end is connected to a common connection point, and the coil of the first high-voltage relay is connected to the relay control signal output end of the controller; the insulation detection module includes a leakage sensor, a current source and an excitation coil, the positive end of the current source and the line excitation coil series circuit is connected to the controller, and the negative end is grounded; the excitation coil is coupled to the coil of the leakage sensor, the first end of the leakage sensor coil is connected to the common connection point, and the other end is grounded; the control end of the power-on mechanism is connected to the control signal output end of the controller.

[0005] The leakage lockout control circuit described above includes a second high-voltage relay, the first end of the leakage sensor coil is connected to the common connection point through the contact of the second high-voltage relay, and the coil of the second high-voltage relay is connected to the relay control signal output end of the controller.

[0006] In the leakage lockout control circuit described above, the power unit circuit includes a three-phase full-bridge rectifier module and a full-bridge inverter module, and the first end of the first high-voltage relay contact is connected to the corresponding AC output terminal of the full-bridge inverter module of the power unit circuit.

[0007] The leakage lockout control circuit described above performs leakage detection when the power circuit of the high-voltage inverter is not powered. The insulation detection module transmits current to the power unit through the first high-voltage relay contact, and then flows to the insulation detection board through the casing ground to form a sampling circuit. The first high-voltage relay contact converts the current signal into a voltage signal and sends it to the controller; the controller calculates the insulation resistance value of the sampling circuit to the ground; when the resistance value of the sampling circuit element to the ground drops to the leakage protection resistance value, the controller sends a signal to the main control system of the high-voltage inverter, cuts off the power-on mechanism of the high-voltage inverter power circuit, prohibits the power circuit from being powered on, and sends a fault alarm signal.

[0008] In the leakage lockout control circuit described above, when the first high-voltage relay contact is closed, the controller prohibits the power-on mechanism of the high-voltage inverter power circuit from operating; only after the first high-voltage relay contact is disconnected, the controller allows the power-on mechanism of the high-voltage inverter power circuit to operate and power on the power circuit.

[0009] The present invention has a simple structure and low loop loss, and can monitor the leakage conditions of all power units of the high-voltage frequency converter, thereby improving the safety of the equipment. [Drawings]

[0010] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0011] Figure 1 It is a structural block diagram of a leakage lockout control circuit of a high-voltage inverter according to an embodiment of the present invention.

[0012] Figure 2 It is a principle block diagram of the insulation monitoring board according to an embodiment of the present invention.

[0013] Figure 3 It is a principle block diagram of a high voltage relay module according to an embodiment of the present invention.

[0014] Figure 4 It is a principle block diagram of the main circuit of the power unit according to an embodiment of the present invention. [Specific implementation method]

[0015] The structure of the leakage lockout control circuit of the high voltage inverter according to the embodiment of the present invention is as follows: Figure 1 As shown, it includes a PLC controller 260, a multi-channel high-voltage relay 220, a single-channel high-voltage relay 240 and an insulation detection template 200. Leakage monitoring and locking control are performed on 24 power units of the high-voltage inverter.

[0016] The main circuit of the high-voltage inverter includes an input transformer 110, 24 power units 210 and a power-on mechanism. The 24 power units 210 are divided into three groups, and each group of 8 power units 210 is connected in series and then in a star shape.

[0017] The multi-way high-voltage relay 220 includes 24 pairs of contacts, and the first end of each pair of contacts of the multi-way high-voltage relay 220 is electrically connected to the circuit of a corresponding power unit 210, and the other end is connected to the common connection point. The circuits of all 24 power units 210 form a star connection through the 24 pairs of contacts of the multi-way high-voltage relay 220.

[0018] The casing 230 of the high voltage inverter is grounded.

[0019] like Figure 2 As shown, the insulation detection template 200 includes a leakage sensor, a current source and an excitation coil. The positive terminal of the series circuit of the current source and the line excitation coil is connected to the PLC controller 260, and the negative terminal is grounded. The excitation coil is wound around the leakage sensor and coupled with the coil of the leakage sensor.

[0020] The first end of the leakage sensor coil is connected to the common connection point through the contact of the single-way high-voltage relay 240, and the other end is grounded. The single-way high-voltage relay 240 is used to control the on-off of the multi-way high-voltage relay 220 and the insulation detection template 200.

[0021] The control coil of the multi-channel high-voltage relay 220 and the coil of the single-channel high-voltage relay 240 are connected to the relay control signal output terminal of the PLC controller 260 through the relay coil control circuit 280. The control terminal of the power-on mechanism of the input transformer 110 is connected to the control signal output terminal of the PLC controller 260.

[0022] like Figure 4 As shown, the power unit circuit includes a three-phase full-bridge rectifier module composed of six rectifier diodes, a full-bridge inverter module composed of a DC bus and four switch tubes, and the housing of the power unit is connected to the ground. The three-phase full-bridge rectifier module has three AC input terminals A, B, and C, the full-bridge inverter module has two AC output terminals D and E, and the three-phase full-bridge rectifier module has two output terminals F and G. The first end of the multi-way high-voltage relay 220 contact can be connected to any one of the terminals A, B, C, D, E, F and G. Considering the convenience of connection, in this embodiment, the first end of the multi-way high-voltage relay 220 contact is connected to the AC output terminal D or E of the corresponding power unit circuit.

[0023] The leakage lockout control circuit of the high-voltage inverter of the embodiment of the present invention performs leakage detection when the power circuit of the high-voltage inverter is not powered. When the contacts of the multi-channel high-voltage relay 220 are closed, the PLC controller 260 prohibits the power-on mechanism of the power circuit of the high-voltage inverter from operating. After the contacts of the multi-channel high-voltage relay 220 are disconnected, the PLC controller 260 allows the power-on mechanism of the power circuit of the high-voltage inverter to operate and power on the power circuit.

[0024] When the main circuit is powered on, the PLC disconnects the two high-voltage relays to reliably isolate the high-voltage main circuit from the insulation monitoring circuit, and the detection circuit will not be damaged by the high voltage.

[0025] The insulation detection template 200 transmits a certain current to the power unit through the contacts of the multi-channel high-voltage relay 220, and then flows to the insulation detection board through the chassis ground to form a sampling loop. The contacts of the multi-channel high-voltage relay 220 convert the current signal into a voltage signal and send it to the PLC controller 260. The PLC controller 260 calculates the insulation resistance value of the sampling loop to the ground. When the resistance value of the sampling loop element to the ground drops to the leakage protection resistance value, the PLC controller 260 sends a signal to the main control system of the high-voltage inverter, cuts off the power-on mechanism of the high-voltage inverter power circuit, prohibits the power circuit from being powered on, and sends a fault alarm signal.

[0026] The above embodiments of the present invention combine the leakage locking circuit and the PLC controller to realize automated operation, greatly improve the safety performance of the high-voltage inverter, have a high degree of circuit intelligence, are easy to install, maintain and use, and improve equipment safety.

Claims

1. A leakage locking control circuit for a high-voltage frequency converter. The main circuit of the high-voltage frequency converter includes an input transformer, multiple groups of serially connected power units, and a power-on mechanism. Characterized in that, it includes a controller, a first high-voltage relay, and an insulation detection module; the first high-voltage relay includes contacts with the same number as the power units. The first end of the contacts of the first high-voltage relay is connected to the corresponding power unit circuit, and the other end is connected to a common connection point. The coil of the first high-voltage relay is connected to the relay control signal output end of the controller; the insulation detection module includes a leakage sensor, a current source, and an excitation coil. The positive end of the circuit in which the current source is serially connected with the line excitation coil is connected to the controller, and the negative end is grounded; the excitation coil is coupled with the coil of the leakage sensor. The first end of the coil of the leakage sensor is connected to the common connection point, and the other end is grounded; the control end of the power-on mechanism is connected to the control signal output end of the controller; when the power circuit of the high-voltage frequency converter is in an unpowered state, leakage detection is performed. The insulation detection module sends current to the power units through the contacts of the first high-voltage relay, and then flows to the insulation detection board through the machine shell ground to form a sampling circuit. The contacts of the first high-voltage relay convert the current signal into a voltage signal and send it to the controller; the controller calculates the insulation resistance value of the sampling circuit to the ground; when the insulation resistance value of the sampling circuit to the ground drops to the leakage protection resistance value, the controller sends a signal to the main control system of the high-voltage frequency converter, cuts off the power-on mechanism of the power circuit of the high-voltage frequency converter, prohibits power-on of the power circuit, and issues a fault alarm signal.

2. The leakage locking control circuit according to claim 1, Characterized in that, it includes a second high-voltage relay. The first end of the coil of the leakage sensor is connected to the common connection point through the contacts of the second high-voltage relay. The coil of the second high-voltage relay is connected to the relay control signal output end of the controller.

3. The leakage locking control circuit according to claim 1, Characterized in that, the power unit circuit includes a three-phase full-bridge rectification module and a full-bridge inversion module. The first end of the contacts of the first high-voltage relay is connected to the AC output terminal of the full-bridge inversion module of the corresponding power unit circuit.

4. The leakage locking control circuit according to claim 1, Characterized in that, when the contacts of the first high-voltage relay are closed, the controller prohibits the operation of the power-on mechanism of the power circuit of the high-voltage frequency converter; after the contacts of the first high-voltage relay are opened, the controller allows the power-on mechanism of the power circuit of the high-voltage frequency converter to operate and supplies power to the power circuit.

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