Leakage locking control circuit of high-voltage frequency converter[ Technical field ]
The invention relates to a high-voltage frequency converter, in particular to a leakage locking control circuit of the high-voltage frequency converter.
[ Background Art ]
The cascade high-voltage frequency converter has high operating voltage and high insulation requirement due to a plurality of power units. The common leakage blocking circuit is directly connected with the power output end of the frequency converter and is communicated with the motor, and the leakage blocking circuit is applied to the high-voltage frequency converter, so that the leakage condition of each power unit is difficult to monitor due to the fact that a loop is bent and has large loss.
[ Summary of the invention ]
The invention aims to solve the technical problem of providing the leakage blocking control circuit which has a simple structure and small loop loss and can monitor the leakage condition of all power units of the high-voltage frequency converter.
In order to solve the technical problem, the technical scheme includes that the leakage locking control circuit of the high-voltage frequency converter comprises a controller, a first high-voltage relay and an insulation detection module, wherein a main circuit of the high-voltage frequency converter comprises an input transformer, a plurality of groups of power units connected in series and an upper motor mechanism, the first high-voltage relay comprises contacts with the same number as the power units, a first end of each contact of the first high-voltage relay is connected with a corresponding power unit circuit, the other end of each contact of the first high-voltage relay is connected with a public connection point, a coil of the first high-voltage relay is connected with a relay control signal output end of the controller, the insulation detection module comprises a leakage sensor, a current source and an excitation coil, the current source is connected with the positive electrode of the circuit in series with the line excitation coil, the negative electrode of the circuit is connected with the ground, the excitation coil is coupled with the coil of the leakage sensor, the first end of the coil of the leakage sensor is connected with the public connection point, the other end of the coil of the excitation coil is grounded, and the control signal output end of the upper motor mechanism is connected with the control signal of the controller.
The leakage locking control circuit comprises a second high-voltage relay, wherein the first end of the leakage sensor coil is connected with a common connection point through a contact of the second high-voltage relay, and the coil of the second high-voltage relay is connected with a relay control signal output end of the controller.
The leakage locking control circuit comprises a power unit circuit, a first high-voltage relay contact and a second high-voltage relay contact, wherein the power unit circuit comprises a three-phase full-bridge rectifying module and a full-bridge inverting module, and the first end of the first high-voltage relay contact is connected with an alternating-current output terminal of the corresponding full-bridge inverting module of the power unit circuit.
The leakage locking control circuit is used for carrying out leakage detection on the power loop of the high-voltage frequency converter in a non-power-supplied state, the insulation detection module is used for conveying current to the power unit through the first high-voltage relay contact, then the current flows to the insulation detection board through the grounding of the shell to form a sampling loop, the first high-voltage relay contact is used for converting a current signal into a voltage signal and sending the voltage signal to the controller, the controller is used for calculating the insulation resistance value of the sampling loop to the ground, and when the resistance value of the sampling loop element to the ground is reduced to the leakage protection resistance value, the controller is used for signaling the main control system of the high-voltage frequency converter, cutting off the power-on mechanism of the power loop of the high-voltage frequency converter, prohibiting the power loop from being electrified and sending a fault alarm signal.
In the leakage locking control circuit, when the first high-voltage relay contact is closed, the controller prohibits the action of the upper motor mechanism of the power circuit of the high-voltage frequency converter, and after the first high-voltage relay contact is opened, the controller only allows the action of the upper motor mechanism of the power circuit of the high-voltage frequency converter to electrify the power circuit.
The invention has simple structure and small loop loss, can monitor the electric leakage condition of all power units of the high-voltage frequency converter, and improves the safety of equipment.
[ Description of the drawings ]
The invention will be described in further detail with reference to the drawings and the detailed description.
Fig. 1 is a block diagram of a leakage lock control circuit of a high-voltage inverter according to an embodiment of the present invention.
Fig. 2 is a schematic block diagram of an insulation monitoring board according to an embodiment of the present invention.
Fig. 3 is a schematic block diagram of a high voltage relay module according to an embodiment of the present invention.
Fig. 4 is a functional block diagram of a power cell main circuit according to an embodiment of the present invention.
Detailed description of the preferred embodiments
The structure of the leakage blocking control circuit of the high-voltage frequency converter according to the embodiment of the invention is shown in fig. 1, and the leakage blocking control circuit comprises a PLC (programmable logic controller) 260, a multi-path high-voltage relay 220, a single-path high-voltage relay 240 and an insulation detection template 200. And performing leakage monitoring and locking control on 24 power units of the high-voltage frequency converter.
The main circuit of the high-voltage frequency converter comprises an input transformer 110, 24 power units 210 and an upper motor mechanism, wherein the 24 power units 210 are divided into three groups, and 8 power units 210 in each group are connected in series and then are connected in a star shape.
The multi-path high voltage relay 220 includes 24 pairs of contacts, and a first end of each pair of contacts of the multi-path high voltage relay 220 is electrically connected to the circuit of a corresponding one of the power cells 210, and the other end is connected to the common connection point. All the circuits of the 24-medium power unit 210 form a star connection through 24 pairs of contacts of the multi-way high voltage relay 220.
The chassis 230 of the high voltage inverter is grounded.
As shown in fig. 2, the insulation detection template 200 includes a leakage sensor, a current source, and an excitation coil. The positive electrode of the current source and line excitation coil serial circuit is connected with the PLC 260, and the negative electrode is connected with the ground. The exciting coil is wound on the leakage sensor and is coupled with the coil of the leakage sensor,
The first end of the leakage sensor coil is connected to the common connection point through the contact of the one-way high-voltage relay 240, and the other end is grounded. The single-path high-voltage relay 240 is used for controlling the on-off of the multi-path high-voltage relay 220 and the insulation detection template 200.
The control coils of the multi-path high-voltage relay 220 and the coils of the single-path high-voltage relay 240 are connected with relay control signal output ends of the PLC 260 through a relay coil control circuit 280. The control end of the power-on mechanism of the input transformer 110 is connected with the control signal output end of the PLC 260.
As shown in fig. 4, the power unit circuit includes a full-bridge inverter module composed of six rectifying diodes, a three-phase full-bridge rectifying module, a dc bus and 4 switching tubes, and the casing of the power unit is grounded. The three-phase full-bridge rectifier module has three alternating current input terminals A, B, C, the full-bridge inverter module has two alternating current output terminals and D and E, and the three-phase full-bridge rectifier module has two output terminals F and G. A first end of the contacts of the multi-way high voltage relay 220 may be connected to either one of the terminals A, B, C, D, E, F and G. In view of the convenience of connection, in this embodiment, the first ends of the contacts of the multiple high-voltage relay 220 are connected to the ac output terminals D or E of the corresponding power unit circuits.
In the leakage locking control circuit of the high-voltage frequency converter, when the power circuit of the high-voltage frequency converter is in a non-power-supply state to perform leakage detection and the contacts of the multi-path high-voltage relay 220 are closed, the PLC 260 prohibits the action of the upper motor mechanism of the power circuit of the high-voltage frequency converter. After the contacts of the multi-path high-voltage relay 220 are opened, the PLC 260 allows the power-on mechanism of the power loop of the high-voltage frequency converter to act, and the power loop is powered on.
Under the condition that the main circuit is electrified, 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 cannot be damaged by high voltage.
The insulation detection template 200 transmits a certain current to the power unit through the contacts of the multi-path high-voltage relay 220, and then the current flows to the insulation detection plate to form a sampling loop through the grounding of the machine shell, and the contacts of the multi-path high-voltage relay 220 convert the current signal into a voltage signal and send the voltage signal to the PLC 260. The PLC controller 260 calculates the insulation resistance to ground of the sampling loop. When the ground resistance of the sampling loop element is reduced to the leakage protection resistance, the PLC 260 signals the main control system of the high-voltage frequency converter, cuts off the power-on mechanism of the power loop of the high-voltage frequency converter, prohibits the power loop from being powered on and sends out a fault alarm signal.
According to the embodiment of the invention, the leakage locking circuit and the PLC are combined to realize automatic operation, so that the safety performance of the high-voltage frequency converter is greatly improved, the intelligent degree of the circuit is high, the installation, maintenance and use are convenient, and the safety of equipment is improved.