CN206300991U - An overcurrent fault monitoring and protection device for flexible direct current transmission inverter station - Google Patents

Abstract

The utility model provides a kind of over current fault monitoring and protecting device for flexible DC power transmission Inverter Station, is related to technical field of electric power system control.The device includes microprocessor unit, composite buffering protection location, power converter unit, IGBT driver elements, overheating detection unit, fault current detection unit, radio communication unit, LC wave filters and host computer; the electric current and temperature information collected by microprocessor processes overheating detection unit and fault current detection unit; IGBT driver elements are driven to control the break-make of IGBT device, while by transmitting fault information to host computer.The utility model can detect the type and power converter unit overheating fault of positioning fault current; to having detected that fault current is positioned, classified and processed; and then quick and precisely suppress failure during short circuit current and overcurrent; the damage of power converter unit is avoided, flexible DC power transmission Inverter Station over current fault monitoring positioning is realized and is protected.

Description

An overcurrent fault monitoring and protection device for flexible direct current transmission inverter station

technical field

The utility model relates to the technical field of flexible direct current transmission, in particular to an overcurrent fault monitoring and protection device for a flexible direct current transmission inverter station.

Background technique

With the prominence of environmental problems and the intensification of the energy crisis, renewable energy such as wind energy and solar energy has developed by leaps and bounds. As an effective way to connect clean energy to the grid, flexible DC transmission technology has attracted more and more attention. Due to the adjustment method of the flexible DC transmission system and the inherent characteristics of its own structure, the fault current of the DC transmission line has the characteristics of fast rising speed and large peak value, and frequent overcurrent faults. When a fault occurs, the fault current can easily damage the converter of the inverter station. The current equipment and equipment are insulated, and the flexible DC transmission cannot monitor, locate and classify the fault current through relevant measures, and cannot realize the self-clearing of the fault by adjusting the trigger angle. high demands. At present, the protection of DC lines in flexible DC transmission projects only borrows the protection strategy of traditional HVDC transmission, which does not meet the requirements of fast action of flexible DC line protection. For the overcurrent fault of the flexible HVDC inverter station, not only fast and reliable line protection is required to identify the overcurrent fault, but also corresponding treatment measures and means are required to effectively limit the overcurrent after the fault to reduce the impact of the fault The current damages the converter components, DC lines and systems of the inverter station.

Utility model content

Aiming at the defects of the prior art, the utility model provides an overcurrent fault monitoring and protection device for flexible direct current transmission inverter stations, aiming at the monitoring and positioning of overcurrent faults and the suppression and protection of line overcurrent faults, combining hardware The auxiliary circuit and the hardware structure of the control system can detect and locate the type of fault current and the overheating fault of the power frequency conversion unit, locate, classify and process the detected fault current, and then quickly and accurately suppress the short-circuit current and overcurrent during the fault period, avoiding the power conversion unit It realizes the monitoring, positioning and protection of overcurrent faults in inverter stations of flexible DC transmission, avoids secondary damage to converter devices, DC lines and systems of inverter stations, and has the function of enhancing man-machine dialogue.

An overcurrent fault monitoring and protection device for a flexible direct current transmission inverter station, including a microprocessor unit, a composite buffer protection unit, a power conversion unit, an IGBT (insulated gate bipolar transistor) drive unit, an overheat detection unit, and a fault current Detection unit, wireless communication unit, LC filter and host computer;

The microprocessor unit includes a main control chip, a first buffer chip and a second buffer chip, which are used to process the current and temperature information collected by the overheat detection unit and the fault current detection unit, and then drive the IGBT drive unit to control the communication of the IGBT device. At the same time, the fault information is transmitted to the host computer to protect related devices from secondary damage; the IGBT drive unit is connected to the main control chip through the first buffer chip, and the overheat detection unit and fault current detection unit are both connected through the second The buffer chip is connected to the main control chip, and the wireless communication unit is directly connected to the main control chip;

The composite buffer protection unit includes two first composite buffer circuits and a second composite buffer circuit with the same structure, which are respectively arranged on two busbars to suppress the peak voltage on the busbar when the IGBT device is turned on and off; the composite buffer protection The unit includes two input terminals and three output terminals, the first input terminal of the composite buffer protection unit is connected to the flexible direct current transmission terminal station as a DC power supply, and the second input terminal of the composite buffer protection unit is connected to the IGBT The output terminal of the drive unit, the first output terminal of the composite buffer protection unit is connected to the input terminal of the fault current detection unit, the second output terminal of the composite buffer protection unit is connected to the first input terminal of the overheat detection unit, and the composite buffer protection unit The third output end of the unit is connected to the first input end of the power conversion unit;

The power frequency conversion unit is used to convert the DC voltage at the busbar side to the AC voltage at the grid side, and includes 6 subunits with the same structure, and the circuit structure of each subunit is the same as that of the first or second composite buffer circuit ;

The IGBT drive unit is used to boost the output signal of the microprocessor unit, and then achieve the voltage required for controlling the gate of the IGBT device;

The overheat detection unit is used to detect the temperature of each IGBT device in the composite buffer protection unit and the power conversion unit, including 8 groups of overheat detection circuits with the same circuit structure;

The fault current detection unit is used to detect whether the current at the point to be detected in the monitoring and protection device exceeds a preset current value, and includes a bridge arm through fault current detection unit, a bus fault current detection unit and a load fault current detection unit, the bridge arm The detection circuit of the through-fault current detection unit is a decentralized overcurrent protection circuit, which is used to detect whether the through-current of the bridge arm at the point to be detected in the composite buffer unit and the power conversion unit exceeds the preset current value. The bus fault current detection unit and the load The detection and protection circuits of the fault current detection unit are all centralized overcurrent protection circuits. The bus fault current detection unit is used to detect whether the current at the point to be detected on the DC bus exceeds the preset current value, and a A bus fault current detection unit, the load fault current detection unit is used to detect whether the current at the point to be detected on the load connection line exceeds a preset current value;

The wireless communication unit is used to wirelessly transmit the signal of the micro-processing unit to the host computer;

The LC filter is used to filter out the harmonics generated by the power frequency conversion unit, including three groups of LC filter circuits, the input ends of the three groups of LC filter circuits are respectively connected to the three output terminals of the power conversion unit, and the three groups The output ends of the LC filter circuit are respectively connected to the three-phase lines of the power grid;

The upper computer is a mobile phone and a computer PC, which are used for real-time monitoring of the overcurrent and overheating fault information of the device, and at the same time can control the on-off of the IGBT device by sending instructions.

Further, the first composite snubber circuit includes a first IGBT device, a first resistor, a first capacitor, a first inductor, a first reverse diode, and a second reverse diode;

One end of the first inductance is used as the first input end of the composite buffer protection unit, connected to the flexible DC transmission end station as a DC power supply, and connected to the cathode of the first reverse diode at the same time, the other end of the first inductance Connect the collector of the first IGBT device, one end of the first resistor, the anode of the first reverse diode and the anode of the second reverse diode, the emitter of the first IGBT device is connected to the cathode of the second reverse diode, the second reverse diode The other end of a resistor, the positive pole of the first capacitor, and the first input terminal of the power frequency conversion unit, the negative pole of the first capacitor is used as the third output terminal of the composite buffer protection unit, connected to the emitter of the first IGBT device and the power frequency conversion unit The first input terminal of the unit, the gate of the first IGBT device is used as the second input terminal of the composite buffer protection unit, connected to the output terminal of the IGBT drive unit; the collector of the first IGBT device is used as the first input terminal of the composite buffer unit The output terminal is connected to the input terminal of the fault current detection unit; a PTC thermistor is placed at the position ⑥ of the first IGBT device as the second output terminal of the composite buffer protection unit, and connected to the first input terminal of the overheat detection unit.

Further, the power frequency conversion unit also includes a third capacitor; the gates of the IGBT devices of each subunit are used as the second input terminal of the power frequency conversion unit, connected to the output terminal of the IGBT drive unit; one end of the inductor in each subunit respectively serve as the input terminals of the corresponding subunits; the emitters of the IGBT devices in each subunit respectively serve as the output terminals of the corresponding subunits; the first subunit, the third subunit, and the first subunit among the six subunits with the same structure The input ends of the five subunits are connected at one point, as the first input end of the power frequency conversion unit, connected to the third output end of the first composite buffer circuit connected to the bus I, and the second of the six subunits with the same structure The output ends of the subunit, the fourth subunit, and the sixth subunit are connected at one point, as the first input end of the power conversion unit, connected to the third output end of the second composite buffer circuit connected to the bus II; the third The capacitor is connected between the input terminal of the first subunit and the output terminal of the second subunit; the output terminals of the first subunit, the third subunit, and the fifth subunit in the six subunits with the same structure are respectively The input terminals of the second subunit, the fourth subunit and the sixth subunit are correspondingly connected, and are respectively used as three output terminals of the power conversion unit.

Further, the IGBT driving unit includes a driving chip and a peripheral protection circuit, wherein the peripheral circuit includes a ninth diode, a tenth capacitor, an eleventh capacitor, a current limiting resistor, a buffer resistor, a feedback resistor, a transistor, and an optocoupler;

Pin 6 of the driver chip is connected to the anode of the ninth diode, and the cathode of the ninth diode is connected to the collector of the driven IGBT device. Pin 2 of the driver chip is connected to the 15V power supply, the positive pole of the tenth capacitor and one end of the feedback resistor at the same time. Pin 3 of the driver chip is connected to the positive electrode of the eleventh capacitor and one end of the snubber resistor at the same time, and the other end of the snubber resistor is used as the output end of the IGBT drive unit and connected to the gate of the driven IGBT device; the tenth capacitor and the eleventh capacitor The negative pole is connected to the emitter of the driven IGBT device and pin 1 of the driver chip at the same time. Pin 15 of the driver chip is connected to one end of the current limiting resistor, and the other end of the current limiting resistor is connected to a 15V power supply. Pin 14 of the driver chip is connected to the collector of the transistor. The emitter of the transistor is connected to pin 1 of the optocoupler, the gate of the transistor is connected to the first buffer chip of the microprocessor unit, pin 6 of the driver chip is connected to the second output terminal of the overheat detection unit, pin 5 of the driver chip is connected to the photocoupler The 4 pins of the optocoupler are connected, the 3 pins of the optocoupler are connected to the other end of the feedback resistor, and the 2 pins of the optocoupler are connected to the microprocessor unit.

Further, the overheat detection circuit includes a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first thermistor, a second thermistor, a first voltage comparator and a second voltage comparator ;

The non-inverting input terminal of the first voltage comparator is used as the first input terminal of the overheating detection unit, and is respectively connected with the first thermistor and one terminal of the ninth resistor, and the other terminal of the ninth resistor is connected with the DC power supply VCC, and the first thermistor The other end of the sensitive resistor is grounded; the non-inverting input end of the second voltage comparator is used as the second input end of the overheat detection unit, and is connected to the second thermistor and one end of the eleventh resistor respectively, and the other end of the eleventh resistor One end is connected to the DC power supply VCC, the other end of the second thermistor is grounded; the inverting input ends of the first voltage comparator and the second voltage comparator are connected to one end of the tenth resistor and the twelfth resistor, and the tenth resistor The other end is connected to the DC power supply VCC, and the other end of the twelfth resistor is grounded; the signal output end of the first voltage comparator is used as the first output end of the overheat detection unit, connected with the microprocessor unit, and outputs an alarm signal, and the second voltage comparator The signal output end of the device is used as the second output end of the overheat detection unit, and is connected with the second input end of the microprocessor unit and the IGBT drive unit, and outputs a shutdown signal.

Further, the decentralized overcurrent protection circuit is used to detect the through current of the bridge arm formed by the composite buffer unit and the IGBT device in the power conversion unit, including a third voltage comparator, a thirteenth resistor, a fourteenth resistor, a tenth The fifth resistor and the sixteenth resistor, the tenth diode and the eleventh diode and the first adjustable potentiometer;

The non-inverting input end of the third voltage comparator is connected to one end of the fourteenth resistor and the anode of the tenth diode, and the cathode of the tenth diode is used as the input end of the distributed overcurrent protection circuit, and is connected to the power conversion unit The collector of each IGBT device; one end of the thirteenth resistor is connected to a 15V DC power supply, and the other end is connected to the other end of the fourteenth resistor and a fixed end of the first adjustable potentiometer; the other fixed end of the first adjustable potentiometer The terminal is grounded, the sliding end of the first adjustable potentiometer is connected to one end of the fifteenth resistor, and the other end of the fifteenth resistor is connected to the reverse input terminal of the third voltage comparator; the positive pole of the third voltage comparator is connected to 15V DC power supply, one end of the sixteenth resistor, pin 2 of the driver chip of the IGBT drive unit and one end of the tenth capacitor; the negative pole of the power supply of the third voltage comparator is grounded, and the signal output end of the third voltage comparator is connected to the sixteenth voltage comparator The other end of the resistor is connected to the cathode of the eleventh diode, and the anode of the eleventh diode is used as the output end of the distributed overcurrent protection circuit, connected to pin 6 of the drive chip of the IGBT drive unit, and the third voltage comparator The signal output terminal is connected to the second buffer chip of the microprocessor unit.

Further, the centralized overcurrent protection circuit includes a Hall current sensor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a second adjustable potentiometer, a twelfth capacitor, a thirteenth capacitor and a fourth voltage comparator;

The Hall current sensor is installed on the connection line of the detected point, the signal output terminal of the Hall current sensor is connected with the same input terminal of the fourth voltage comparator; One end is connected to the same input end of the fourth voltage comparator for signal filtering; one fixed end of the second adjustable potentiometer is connected to the 15V power supply, the other fixed end is grounded, and the sliding end is connected to the reverse input end of the fourth voltage comparator connected to provide feedback voltage; one end of the eighteenth resistor is connected to a 5V power supply as a pull-up resistor, and the other end is connected to the signal output end of the fourth voltage comparator and one end of the nineteenth resistor; the other end of the nineteenth resistor is used as a concentrated overcurrent An output port of the protection circuit is connected to the second buffer chip of the microprocessor unit, and is connected to one end of the thirteenth capacitor, and the other end of the thirteenth capacitor is grounded; the nineteenth resistor and the thirteenth capacitor form an RC delay circuit .

Further, the power supply of each unit in the overcurrent fault monitoring and protection device used in the flexible direct current transmission inverter station is provided by a switching power supply with multiple voltage outputs (output ±15V, 5V, 3.3V voltage).

It can be known from the above technical solution that the beneficial effect of the utility model lies in that the utility model provides an overcurrent fault monitoring and protection device for a flexible direct current transmission inverter station, which is aimed at the monitoring and positioning of the overcurrent fault and the line overcurrent Fault suppression protection. Firstly, a composite buffer unit is added to the DC bus at the sending end of the flexible DC power transmission. When the bus IGBT device is turned on or off, it can suppress and reduce the surge voltage amplitude on the bus first; secondly, an overheat detection unit is added to control the operating temperature of the IGBT device. Carry out inspections, record relevant temperature data, analyze the data through the computer PC host computer, establish the relationship curve between IGBT temperature and current, and provide the basis for the classification of fault current; finally, the overcurrent of the power frequency conversion unit is detected by the fault current detection unit. The fault location is monitored and located, and the gate voltage is slowly lowered through the hardware auxiliary circuit and the microprocessor unit to extend the fault protection time of the action circuit, and the wireless communication unit is used to communicate with the mobile phone and the computer to realize data sharing between the mobile phone and the computer, and enhance man-machine Dialogue to avoid secondary damage to the converter components, DC lines and systems of the inverter station. The utility model combines the hardware auxiliary circuit and the hardware structure of the control system, can detect and locate the type of fault current and the overheating fault of the power frequency conversion unit, locate, classify and process the detected fault current, and then quickly and accurately suppress the short-circuit current and overheating fault during the fault period. current, to avoid damage to the power conversion unit, and to realize the monitoring, positioning and protection of overcurrent faults in the flexible DC transmission inverter station.

Description of drawings

Figure 1 is a schematic structural diagram of an overcurrent fault monitoring and protection device for a flexible DC transmission inverter station provided by an embodiment of the present invention;

Fig. 2 is the circuit principle diagram of the microprocessor unit that the utility model embodiment provides;

Fig. 3 is the circuit schematic diagram of the compound snubber circuit that the utility model embodiment provides;

Fig. 4 is the circuit principle diagram of the power frequency conversion unit provided by the embodiment of the utility model;

Fig. 5 is a schematic diagram of the connection circuit of the flexible direct current transmission terminal station, the composite buffer unit, the power frequency conversion unit and the LC filter provided by the embodiment of the utility model;

Fig. 6 is the circuit schematic diagram of the IGBT driving unit provided by the embodiment of the utility model;

Fig. 7 is a schematic circuit diagram of an overheat detection unit provided by an embodiment of the present invention;

Fig. 8 is a schematic diagram of the working principle of the decentralized overcurrent protection circuit provided by the embodiment of the present invention;

9 is a schematic diagram of a decentralized overcurrent protection circuit connected to an IGBT drive unit provided by an embodiment of the present invention;

Fig. 10 is a schematic circuit diagram of the centralized overcurrent protection circuit on the DC bus at the sending end of the flexible DC transmission provided by the embodiment of the utility model;

Fig. 11 is a circuit schematic diagram of the composite buffer unit IGBT turn-off time provided by the embodiment of the utility model;

Fig. 12 is a circuit schematic diagram of the composite buffer unit IGBT turn-on time provided by the embodiment of the utility model;

Fig. 13 is a graph of effective value of three-phase current before installing an overcurrent fault monitoring and protection device provided by the embodiment of the present invention;

Fig. 14 is a three-phase current effective value curve diagram provided by an embodiment of the present invention after installing an overcurrent fault monitoring protection device;

Fig. 15 is a curve diagram of the relationship between IGBT temperature and current after installing the overcurrent fault monitoring and protection device provided by the embodiment of the present invention.

detailed description

Below in conjunction with accompanying drawing and embodiment, the specific embodiment of the utility model is described in further detail. The following examples are used to illustrate the utility model, but not to limit the scope of the utility model.

As shown in Figure 1, an overcurrent fault monitoring and protection device for a flexible DC transmission inverter station, the device includes a microprocessor unit, a composite buffer protection unit, a power conversion unit (flexible DC transmission receiving end station), an IGBT Drive unit, overheat detection unit, fault current detection unit, wireless communication unit, LC filter and host computer. In this embodiment, the wireless communication unit adopts the SIM808 wireless module, which is used to wirelessly transmit the signal of the microprocessing unit to the upper computer, the IGBT device adopts the IGBT module of the model FZ1000R20KS4, the IGBT drive unit adopts the EXB841 IGBT integrated driver, and the upper computer is a mobile phone And computer PC, used for real-time monitoring of overcurrent and overheating fault information of the device, and at the same time, it can control the IGBT on and off by sending instructions. The power supply of each unit in the device is provided by a switching power supply with multiple voltage outputs (output ±15V, 5V, 3.3V voltage).

The microprocessor unit is used to process the current and temperature information collected by the overheat detection unit and the fault current detection unit, and then drive the IGBT drive unit to control the on-off of the IGBT device, and at the same time transmit the fault information to the host computer to protect related devices from secondary damage. secondary damage. In this embodiment, the microprocessor unit includes a TMS320F28335 main control chip, a first buffer chip 74HC245 and a second buffer chip 743384, the IGBT drive unit, the overheat detection unit and the fault current detection unit are all connected to the main control chip through the buffer chip, The wireless communication unit is directly connected with the main control chip. The TMS320F28335 main control chip is a processor with a main frequency up to 150MHZ, with 8 channels of complementary symmetrical pulse width modulation ports PWM1-8, built-in 2*8 channel 12-bit ADC converter, and 3 channel SCI communication interface.

Taking a group of detection units as an example, as shown in Figure 2, the specific connection structure between the microprocessor unit and other peripheral units is: the pulse width modulation ports PWM1, PWM2, PWM3, PWM4, PWM5, PWM6, PWM7, PWM8 of the main control chip They are respectively connected to ports A0, A1, A2, A3, A4, A5, A6 and A7 of the first buffer chip 74HC245 in one-to-one correspondence, B0 and R1 of the first buffer chip 74HC245 are connected to ports S3 and S4 of the IGBT drive unit, and 74HC245 buffers The B6 and R1 of the chip are connected to the IN1 and IN2 ports of the IGBT drive unit. The ADCINA0 and ADCINA7 ports of the TMS320F28335 main control chip are respectively connected to the A0 and A1 ports of the second buffer chip 743384. The D0 and D18 ports of the TMS320F28335 main control chip are respectively connected to the second buffer chip. The A8 and A15 ports of the second buffer chip 743384, the B0 and B7 of the second buffer chip 743384 are connected to the 0C1 and 0C2 ports of the fault current detection unit respectively, and the B8 and R15 of the second buffer chip 743384 are respectively connected to the two outputs of the overheat detection unit The ports S1 and S2 are connected; the SCITXD port of the wireless communication unit SIM808 module is connected with the SCIRXD port of the TMS320F28335 main control chip, and the SCIRXD port of the wireless communication unit SIM808 module is connected with the SCITXD port of the TMS320F28335 main control chip.

The composite buffer protection unit includes two composite buffer circuits with the same structure, which are respectively installed on two busbars to suppress the peak voltage on the busbar when the IGBT is turned on and off. The composite buffer protection unit includes two input terminals and three output terminals. The composite buffer protection unit The first input terminal of the unit is connected to the flexible DC transmission terminal station as a DC power supply, the second input terminal of the composite buffer protection unit is connected to the output terminal of the IGBT drive unit, and the first output terminal of the composite buffer protection unit is connected to the input of the fault current detection unit The second output end of the composite buffer protection unit is connected to the first input end of the overheat detection unit, and the third output end of the composite buffer protection unit is connected to the first input end of the power conversion unit (flexible direct current transmission terminal station).

The structure of the composite snubber circuit on the two busbars is the same, as shown in Figure 3, both of which include an IGBT device VT1 with high-frequency breaking function, resistor R1, capacitor C1, inductor L1, the first reverse diode VD1 and the second reverse Diode VD2. Taking a bus bar as an example, the first composite snubber circuit includes IGBT device VT1, resistor R1, capacitor C1, inductor L1, first reverse diode VD1 and second reverse diode VD2, and the specific connection structure is: one end of inductor L1 serves as the The input terminal of the composite buffer circuit, that is, the first input terminal of the composite buffer protection unit, is connected to the flexible DC transmission terminal station as a DC power supply, and is connected to the cathode of the first reverse diode VD1 at the same time, and the other end of the inductor L1 is connected to the IGBT device VT1 The collector of the resistor R1, the anode of the first reverse diode VD1 and the anode of the second reverse diode VD2, the emitter of the IGBT device VT1 is connected to the cathode of the second reverse diode VD2, the other end of the resistor R1, and the capacitor The positive pole of C1 and the first input terminal of the power conversion unit, the negative pole of capacitor C1 as the third output terminal of the composite buffer protection unit, connect the emitter of the IGBT device VT1 and the first input terminal of the power conversion unit; the gate of the IGBT device VT1 The pole serves as the second input terminal of the composite buffer protection unit, and is connected to the output terminal of the IGBT drive unit. The collector of the IGBT device VT1 is used as the first output terminal of the composite buffer unit, connected to the input terminal of the fault current detection unit; a PTC thermistor is placed at the position ⑥ of the IGBT device VT1, as the second output terminal of the composite buffer unit, connected to The first input terminal of the overheat detection unit.

The power frequency conversion unit is used to convert the DC voltage on the busbar side to the AC voltage on the grid side, as shown in Figure 4, including the filter support capacitor C3 and 6 subunits with the same structure, and the circuit structure of each subunit is the same as that of the first or second The circuit structure of the compound snubber circuit is the same. The IGBT device VT3 and its peripheral circuit are used as the first subunit of the power conversion unit, the IGBT device VT4 and its peripheral circuit are used as the second subunit of the power conversion unit, and the IGBT device VT5 and its peripheral circuit are used as the third subunit of the power conversion unit , IGBT device VT6 and its peripheral circuit as the fourth subunit of the power frequency conversion unit, IGBT device VT7 and its peripheral circuit as the fifth subunit of the power frequency conversion unit, IGBT device VT8 and its peripheral circuit as the sixth subunit of the power frequency conversion unit unit. Taking the first subunit as an example, it includes an IGBT device VT3 with a high-frequency breaking function, a resistor R3, a capacitor C4, an inductor L3, a first reverse diode VD3, and a second reverse diode VD4; one end of the inductor L3 is connected to the first The cathode of the reverse diode VD3, the other end of the inductor L3 is connected to the collector of the IGBT device VT3, one end of the resistor R3, the anode of the first reverse diode VD3 and the anode of the second reverse diode VD4, and the emitter of the IGBT device VT3 is connected to The cathode of the second reverse diode VD4, the other end of the resistor R3, and the anode of the capacitor C4, the cathode of the capacitor C4 are connected to the emitter of the IGBT device VT3, and the gate of the IGBT device VT3 is used as the second input end of the power conversion unit, connected to the IGBT The first output end of the driving unit. One end of the inductors L3, L4, L5, L6, L7, and L8 in each subunit is used as the input end of the corresponding subunit, and the emitters of the IGBT devices VT3, VT4, VT5, VT6, VT7, and VT8 in each subunit are respectively as the output of the corresponding subunit. The input terminals of the first subunit, the third subunit and the fifth subunit of the power frequency conversion unit are connected to the third output terminal of the first composite buffer circuit connected to the bus I at the same time, and the second subunit, the fourth subunit, the fifth subunit The output terminals of the six subunits are simultaneously connected to the third output terminal of the second composite buffer circuit connected to the bus II. The capacitor C3 is connected between the input terminal of the first subunit and the output terminal of the second subunit. The output terminals of the first subunit, the third subunit, and the fifth subunit of the power frequency conversion unit are respectively connected to the input terminals of the second subunit, the fourth subunit, and the sixth subunit of the power frequency conversion unit, and serve as power frequency conversion units respectively. Three outputs of the unit.

The connection circuit of the flexible DC transmission terminal station, composite buffer unit, power frequency conversion unit and LC filter is shown in Figure 5.

The IGBT drive unit includes EXB841 drive chip and peripheral protection circuit, as shown in Figure 6, where the peripheral circuit includes ERA34-10 diode D9, capacitors C10, C11, current limiting resistor Re, snubber resistor RG, feedback resistor Rf, transistor TCR and TLP251 optocoupler. Each IGBT drive unit drives a set of half-bridges composed of two IGBTs. Pin 6 of the driver chip EXB841 is connected to the anode of the ERA34-10 diode D9, the cathode of the ERA34-10 diode D9 is connected to the collector of the driven IGBT device, pin 2 of the driver chip EXB841 is connected to the 15V power supply, the positive pole of the capacitor C10, and the positive pole of the capacitor C11 At the same time, it is connected to pin 3 of the driver chip EXB841 and one end of the buffer resistor RG. The other end of the buffer resistor RG is used as the output end of the IGBT drive unit, connected to the gate of the driven IGBT device, and the negative poles of the capacitor C10 and capacitor C11 are simultaneously connected to be driven The emitter of the IGBT, the pin 15 of the driver chip EXB841 is connected to one end of the current limiting resistor Re, the other end of the current limiting resistor Re is connected to a 15V power supply, the pin 14 of the driver chip EXB841 is connected to the collector of the transistor TCR, the emitter of the transistor TCR is connected to the TLP251 The 1 pin of the optocoupler is connected, the gate of the transistor TCR is used as the IGBT drive unit to connect the input terminal IN1 of the microprocessor control signal, the 6 pin of the driver chip EXB841 is connected to the second output terminal S2 of the overheat detection unit, and the 5 pin of the driver chip EXB841 is connected to the second output terminal S2 of the overheat detection unit. Pin 4 of the TLP251 optocoupler is connected, pin 3 of the TLP251 optocoupler is connected to one end of the feedback resistor Rf, the other end of the feedback resistor Rf is connected to the 15V unit and pin 2 of the driver chip EXB841, pin 2 of the TLP251 optocoupler is connected to the micro processor unit. The gates of all IGBT devices in the composite buffer unit and the power conversion unit are connected to the output terminal of the IGBT drive unit.

The overheat detection unit is used to detect the temperature of each IGBT device in the composite buffer protection unit and the power frequency conversion unit, including 8 groups of overheat detection circuits with the same circuit structure, which respectively correspond to the detection of the temperature of the 8 IGBT devices in the composite buffer protection unit and the power frequency conversion unit temperature.

Take a set of overheat detection circuit as an example, as shown in Figure 7, including three 2K resistors R9, R10, R11, a 470 ohm resistor R12, two PTC thermistors Rtc1, Rtc2 and two voltage comparators U1, U2 , the voltage comparator is the LM339 model, and its specific connection structure is: the non-inverting input terminal (pin 3) of the voltage comparator U1 is used as the first input terminal of the overheat detection unit, and one end of the thermistor Rtc1 and the resistor R9 are respectively The other end of the resistor R9 is connected to the DC power supply VCC, and the other end of the thermistor Rtc1 is grounded; the non-inverting input terminal (pin 3) of the voltage comparator U2 is used as the second input terminal of the overheating detection unit, and the thermistor Rtc2 and One end of the resistor R11 is connected respectively, the other end of the resistor R11 is connected to the DC power supply VCC, the other end of the thermistor Rtc2 is grounded; the inverting input ends (pin 2) of the voltage comparators U1 and U2 are connected to one end of the resistors R10 and R12 The other end of the resistor R10 is connected to the DC power supply VCC, and the other end of the resistor R12 is grounded; the signal output terminal (pin 1) of the voltage comparator U1 is used as the first output terminal S1 of the overheat detection unit, and is connected to the microprocessor unit. An alarm signal is output, and the signal output terminal (pin 1) of the voltage comparator U2 is used as the second output terminal S2 of the overheat detection unit, which is connected with the microprocessor unit and the IGBT drive unit, and outputs a shutdown signal.

In Figure 7, the DC power supply VCC, the resistor R10 and the resistor R12 are connected in series to provide the reference voltage Vref. When the temperature of the detected IGBT device is lower than 100 degrees, the resistance values of the thermistor Rtc1 and Rtc2 are both less than 470 ohms, so the thermistor The voltage drops Vtc1 and Vtc2 of Rtc1 and Rtc2 are both less than the reference voltage Vref, at this time the voltage of the non-inverting input terminal (pin 3) of the voltage comparator U1 is less than the voltage of the inverting input terminal (pin 2) of U1, and the voltage comparator U1 outputs Low level, the voltage of the non-inverting input terminal (pin 3) of the voltage comparator U2 is lower than the voltage of the negative input terminal (pin 2) of U2, and the voltage comparator U2 outputs a low level. Therefore, when both the alarm signal and the shutdown signal are at low level, the temperature of the detected IGBT device is normal. When the temperature of the detected IGBT device is greater than 100 degrees but less than 120 degrees, the voltage drop Vtc1 of the thermistor Rtc1 is greater than the reference voltage Vref, and the voltage drop Vtc2 of the thermistor Rtc2 is less than the reference voltage Vref, at this time the voltage comparator U1 Output high level, voltage comparator U2 output low level. Therefore, when the alarm signal is at a high level and the shutdown signal is at a low level, the overheat detection circuit sends an overheat alarm signal to the control circuit. When the temperature of the detected IGBT device exceeds 120 degrees, both Vtc1 and Vtc2 are greater than Vref, and at this time U1 and U2 both output high levels. Therefore, when both the alarm signal and the shutdown signal are at high level, the control circuit shuts down the main circuit to protect the IGBT device from being damaged due to overheating.

The fault current detection unit is used to detect whether the current at the point to be detected in the device exceeds the preset current threshold, including a bridge arm through fault current detection unit, a bus fault current detection unit and a load fault current detection unit. The detection circuit of the bridge arm through fault current detection unit is a decentralized overcurrent protection circuit, which is used to detect whether the bridge arm through current at the point to be detected in the composite buffer unit and the power conversion unit exceeds the preset current value, and is used to detect the composite buffer unit and the power conversion unit. The decentralized overcurrent protection circuit in the power conversion unit has the same structure, the detection and protection circuits of the bus fault current detection unit and the load fault current detection unit are centralized overcurrent protection circuits, and the bus fault current detection unit is used to detect the voltage of the point to be detected on the bus Whether the current exceeds the preset current value, and a bus fault current detection unit is respectively arranged on the two buses, and the load fault current detection unit is used to detect whether the current at the point to be detected on the load connection line exceeds the preset current value. The detection positions of the bridge arm through-fault current detection unit are shown in ⑥ and ⑦ in Figure 3 and 4, the detection positions of the bus fault current detection unit are shown in ① and ② in Figure 4, and the detection positions of the load fault current detection unit are shown in Figure 4 ③, ④ and ⑤.

The working principle of the decentralized overcurrent protection circuit is shown in Figure 8. Vref is used as the set threshold voltage of the decentralized overcurrent protection circuit. When the comparator detects that the voltage at point 0 is greater than the set threshold voltage, the comparator outputs a high level The AND gate AND outputs a high-level signal to the micro-processing unit, and then sends out a pulse control signal to control the on-off of the IGBT to prevent the device from suffering secondary damage.

Taking the decentralized overcurrent protection circuit set at the point to be detected of the power conversion unit as an example, Figure 9 is a working principle diagram of the decentralized overcurrent protection circuit connected to the IGBT drive unit provided by this embodiment, and the specific structure of the decentralized overcurrent protection circuit Including voltage comparator U3, resistors R13, R14, R15 and R16, Schottky diodes VD10 and VD11, blue and white adjustable potentiometer RP1 (used to adjust the set voltage threshold), the specific connection structure is:

The same input end of LM339 voltage comparator U3 is connected to one end of resistor R14 and the anode of Schottky diode VD10, the cathode of Schottky diode VD10 is used as the input end INA of the distributed overcurrent protection circuit, and connected to the power conversion unit IGBT device VT3 Collector; one end of resistor R13 is connected to 15V DC power supply, the other end of resistor R13 is connected to the other end of resistor R14 and a fixed end of adjustable potentiometer RP1; the other fixed end of adjustable potentiometer RP1 is grounded, and the adjustable potentiometer The sliding end of RP1 is connected to one end of the resistor R15, and the other end of the resistor R15 is connected to the reverse input end of the voltage comparator U3; one end of the resistor R16 is connected to the 15V DC power supply, and at the same time connected to the positive pole of the voltage comparator U3 and the IGBT drive unit Pin 2 of the driver chip EXB841 and one end of the capacitor C10 of the IGBT drive unit; the negative pole 14 of the power supply of the voltage comparator U3 is grounded, and the signal output end of the LM339 voltage comparator U3 is connected to the other end of the resistor R16 and the Schottky diode VD11 The cathode of the Schottky diode VD11 is used as the output terminal of the distributed overcurrent protection circuit, connected to the pin 6 of the driver chip of the IGBT drive unit, and the signal output terminal OUT of the voltage comparator U3 is the fault current detection unit and the microprocessor The ADOC1 port connected to the second buffer chip of the device unit; the resistor R13 is connected in series with the blue and white adjustable potentiometer RP1, through the adjustable potentiometer RP1, the feedback voltage Vref is provided to the LM339 voltage comparator U3 through the resistor R15, and the LM339 voltage comparator U3 The non-inverting input terminal of the IGBT device collects the collector voltage of the IGBT device through the diode VD10, and compares it with the preset Vref value to determine whether the bridge arm of the IGBT device has an overcurrent fault.

Taking the centralized overcurrent protection circuit on the DC bus at the sending end of flexible DC transmission as an example, as shown in Figure 10, the specific structure of the centralized overcurrent protection circuit takes bus I as an example, including Hall current sensor H1, resistors R17, R18, R19, blue and white adjustable potentiometer RP2, capacitors C12, C13 and LM339 voltage comparator U4, among them, the Hall current sensor H1 adopts the direct measurement Hall effect current sensor HAP8-200/4 of Japan HINODE Company, the sensor needs Positive and negative 15V dual power supply for power supply. The specific connection structure of the circuit is:

The signal output terminal of the Hall current sensor H1 is connected to the same-inverting input terminal (pin 3) of the LM339 voltage comparator U4; one end of the resistor R17 is connected in parallel with the capacitor C12 to ground, and the other end is connected to the same-inverting input terminal of the LM339 voltage comparator U4 (pin 3) for signal filtering; one fixed end of the adjustable potentiometer RP2 is connected to a 15V power supply, the other fixed end is grounded, and the sliding end is connected to pin 2 of the inverting input end of the LM339 voltage comparator U4 to provide feedback voltage ; One end of the resistor R18 is connected to a 5V power supply as a pull-up resistor, and the other end is connected to the signal output terminal (pin 1) of the LM339 voltage comparator U4 and one end of the resistor R19 to improve the current driving capability of the signal output terminal of the LM339 voltage comparator U4. The other end of the resistor R19 is used as an output port OC1 of the centralized overcurrent protection circuit, that is, the ADOC2 port where the fault current detection unit is connected to the second buffer chip of the microprocessor unit, and at the same time connected to one end of the capacitor C13, and the other end of the capacitor C13 is grounded , Resistor R19 and capacitor C13 constitute an RC delay circuit. The LM339 voltage comparator U4 output (pin 1) signal outputs the level signal OC1 to the microprocessor through the buffer resistor R19 to record the current data. When the threshold value is seriously exceeded, all IGBT drive signals are blocked, and the resistor R19 and The delay circuit formed by the capacitor C13 is an anti-jamming measure taken to prevent the malfunction of the blocking circuit. A centralized over-current protection circuit with the same structure is set on the other bus, and its output port is OC2.

The LC filter is used to filter out the harmonics generated by the power frequency conversion unit, including three sets of LC filter circuits. The three-phase lines of the grid.

The method of realizing over-current fault monitoring, positioning and protection through the above-mentioned over-current fault monitoring and protection device used in the flexible direct current transmission inverter station is as follows:

Step 1. Use the microprocessor unit to control the internal components of the composite buffer protection unit, power frequency conversion unit and IGBT drive unit, so that the entire overcurrent fault monitoring and protection device is in operation. The specific method is:

Step 1.1, adopt microprocessor unit to send SPWM (sinusoidal pulse width modulation) signal;

Step 1.2, carry out boost processing through the IGBT drive unit, and increase the amplitude of the SPWM voltage signal to 15V;

Step 1.3, drive the two IGBT devices of the IGBT composite buffer unit and the six IGBT devices of the power conversion unit respectively, so that each IGBT device is turned on, so that the overcurrent fault monitoring and protection device used in the flexible direct current transmission inverter station is in a normal operating state;

Step 2. At the same time, use the PTC thermistor of the overheat detection unit, the decentralized overcurrent protection circuit in the fault current detection unit, and the centralized overcurrent protection circuit to collect the current and heat of the composite buffer protection unit and the power frequency conversion unit in real time, and overheat detection The PTC thermistor of the unit monitors the actual temperature of all IGBT devices in the composite buffer protection unit and the power conversion unit;

The overheat detection unit generates two signals, one alarm signal is sent to the microprocessor unit, and the other is a shutdown signal sent to the EXB841 driver chip of the IGBT drive unit, which prompts the IGBT to perform a soft shutdown of the gate voltage, suppresses the peak surge current, and avoids power failure. The inverter unit is damaged;

The level signals generated in the bus fault current detection unit and the load fault current detection unit are sent to the EXB841 drive chip of the IGBT drive unit and the ADCINAO-A7 port of the microprocessor unit through the delay of the RC delay circuit;

The microprocessor unit collects and records the temperature data of each current and IGBT device, and constructs the relationship curve between the temperature of the IGBT device and the detection branch in real time;

Step 3. The microprocessor unit judges the position of the fault current, judges whether the current value exceeds 1.2 times the set value, and whether the temperature of the IGBT device reaches the overheating alarm temperature of 100°C. If any one of them exceeds or both exceed at the same time, it means If there is a fault, the corresponding unit is the faulty unit, go to step 4, otherwise it means that the DC transmission inverter station is working normally, return to step 2, and continue to detect;

Step 4. Use the microprocessor unit to generate a control signal and send it to the corresponding unit where the fault occurs, and slowly reduce the gate voltage of the IGBT device of the faulty unit; the microprocessor unit records the position of the fault current at the same time, and generates a corresponding number. No. 1 is the bus current fault, No. 2 is the bridge arm through fault, No. 3 and 5 are the load short-circuit fault, and the fault record will be sent to the mobile phone through the SIM808 wireless communication unit to report the fault information judged by the microprocessor unit, and Send out a fault intermediate-level alarm signal, and transmit the fault to the computer PC host computer; the computer PC host computer compares the existing faults with the faults stored in the computer database, and determines the type and location of the fault current;

Step 5. The microprocessor further judges the fault current overheating detection, and judges whether the current value exceeds 1.5 times the set value, and whether the IGBT temperature reaches the overheating alarm temperature of 120°C. If any one exceeds or both exceed at the same time, the corresponding position is determined. If a serious short circuit or overcurrent fault occurs, go to step 6, otherwise go to step 2;

Step 6. The microprocessor unit sends a control signal, blocks the input signal, shuts off the IGBT device in the unit that has a serious short circuit or overcurrent fault, and continuously sends the fault information to the user's mobile phone through the SIM808 wireless communication unit, and at the same time micro The processor unit generates a serious fault alarm signal, and transmits the fault to the PC host computer to avoid secondary damage to the inverter.

In this embodiment, when the monitoring protection is completed, the IGBT device is turned off to form a composite snubber circuit structure as shown in Figure 11, the current in the inductor L1 is released through the diode VD1, and the energy stored in the stray inductance in VT1 is passed through the capacitor C1 and resistor R1 are released, buffering the overcurrent generated when the IGBT device is turned off, and avoiding damage to the IGBT device.

In this embodiment, when the monitoring and protection device starts to operate, the IGBT device is turned on to form a composite snubber circuit structure as shown in Figure 12. The inductance L1 suppresses the current rise rate on the collector side at the moment the IGBT is turned on, reducing the collector side surge. At the same time, the surge current at the moment of VT1 opening is released through VD2 and C1, as shown in the dotted line in the figure, which buffers the surge current generated at the moment of turning on the IGBT to avoid damage to the IGBT device.

Before installing the overcurrent fault monitoring and protection device, the effective value of the three-phase current is shown in Figure 13. After installing the overcurrent fault monitoring and protection device, the three-phase current effective value is shown in Figure 14. From the curve in the figure, it can be seen It is found that during the period from 40ms to 42ms after the switch-on, the peak current after installation is significantly suppressed. After 42ms, the voltage waveform of the AC side is significantly improved, and the instantaneous peak value of the fault current is also significantly suppressed.

After installing the overcurrent fault monitoring and protection device, the relationship between IGBT temperature and current is shown in Figure 15. From the curve in the figure, it can be seen that after the IGBT device is turned on, the current rises slowly within 0-20°C, and at 23°C- During the 38°C period, the current hardly changes, and the IGBT device operates stably. When an overheating fault occurs, the current rises rapidly with the increase of the temperature of the IGBT device. After exceeding the heat resistance limit, the IGBT device is damaged and the current drops to the lowest point. After the overcurrent fault monitoring and protection device is installed, the relationship between current and temperature changes in the overheating fault can be monitored in real time. After the overheating fault occurs, the fault can be eliminated at point C-D to avoid secondary damage to the device and ensure the normal operation of the system.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present utility model, and are not intended to limit it; although the utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the scope defined by the claims of the utility model .

Claims (8)

1. a kind of over current fault monitoring and protecting device for flexible DC power transmission Inverter Station, it is characterised in that：The device includes Microprocessor unit, composite buffering protection location, power converter unit, IGBT (igbt) driver element, mistake Hot detection unit, fault current detection unit, radio communication unit, LC wave filters and host computer；

The microprocessor unit includes main control chip, the first buffer chip and the second buffer chip；The IGBT driver elements It is connected with main control chip by the first buffer chip, the overheating detection unit and fault current detection unit delay by second Rush chip to be connected with main control chip, the radio communication unit is directly connected with the main control chip；

The composite buffering protection location includes two structure identical the first composite buffering circuits and the second composite buffering circuit, It is respectively arranged on two buses；The composite buffering protection location includes two inputs and three output ends, described compound slow The first input end connection of protection location is rushed as the flexible DC power transmission sending end station of dc source, the composite buffering protection is single Second input of unit connects the IGBT driver elements output end, the first output end connection of the composite buffering protection location The input of fault current detection unit, the second output end connection overheating detection unit first of the composite buffering protection location Input, the 3rd output end of the composite buffering protection location connects the first input end of power converter unit；

The power converter unit includes 6 structure identical subelements, the circuit structure of each subelement with described first or The circuit structure of the second composite buffering circuit is identical；

The overheating detection unit includes 8 groups of circuit structure identical overheating detection circuits；

The fault current detection unit includes bridge arm direct pass fault current detection unit, bus-bar fault current detecting unit and bears Fault current detection unit is carried, the detection circuit of the bridge arm direct pass fault current detection unit is dispersion current foldback circuit, The detection protection circuit of the bus-bar fault current detecting unit and load fault current detection unit is concentration overcurrent protection Circuit, is respectively equipped with a bus-bar fault current detecting unit on two buses, and the load fault current detection unit sets In on load connecting line；

The LC wave filters include three groups of LC filter circuits, and the input of three groups of LC filter circuits connects the power respectively Three tunnel output ends of converter unit, the output end of three groups of LC filter circuits connects the triple line of power network respectively；

The host computer is mobile phone and computer PC, and the radio communication unit is connected with mobile phone wireless.

2. the over current fault monitoring and protecting device for flexible DC power transmission Inverter Station according to claim 1, its feature It is：The first composite buffering circuit includes the first IGBT device, first resistor, the first electric capacity, the first inductance, first reverse Diode, the second backward dioded；One end of first inductance as the composite buffering protection location first input end, Connect as the flexible DC power transmission sending end station of dc source, while the negative electrode of the first backward dioded is connected, first electricity The other end of sense connects colelctor electrode, one end of first resistor, the anode of the first backward dioded and second of the first IGBT device The anode of backward dioded, the emitter stage of first IGBT device connects the negative electrode of the second backward dioded, first resistor The other end, the positive pole of the first electric capacity, the first input end of power converter unit, the negative pole of first electric capacity is used as composite buffering 3rd output end of protection location, connects the emitter stage of the first IGBT device and the first input end of power converter unit, first The gate pole of IGBT device connects the output end of IGBT driver elements as the second input of composite buffering protection location；It is described The first IGBT device colelctor electrode as composite buffering unit the first output end, the input of connecting fault current detecting unit End；6. locate to place PTC thermistor in the position of the first IGBT device, as the second output end of composite buffering protection location, Connect the first input end of overheating detection unit.

3. the over current fault monitoring and protecting device for flexible DC power transmission Inverter Station according to claim 2, its feature It is：The power converter unit also includes the 3rd electric capacity；The gate pole of the IGBT device of each subelement is as power frequency conversion list Second input of unit, connects the output end of IGBT driver elements；One end of inductance in each subelement is respectively as corresponding son The input of unit；Output end of the emitter stage of the IGBT device in each subelement respectively as corresponding subelement；6 knots The first subelement, the 3rd subelement in structure identical subelement, the input of the 5th subelement are connected to a bit, used as power The first input end of converter unit, the 3rd output end of the first composite buffering circuit that connection is connected with bus I, 6 knots The second subelement, the 4th subelement in structure identical subelement, the output end of the 6th subelement are connected to a bit, used as power The first input end of converter unit, the 3rd output end of the second composite buffering circuit that connection is connected with bus II；Described 3rd Capacitance connection is between the input of the first subelement and the output end of the second subelement；6 structures identical subelement In the first subelement, that the 3rd subelement, the output end of the 5th subelement are connected respectively the second subelement, the 4th son is single Unit, the input of the 6th subelement, and respectively as three tunnel output ends of power converter unit.

4. the over current fault monitoring and protecting device for flexible DC power transmission Inverter Station according to claim 3, its feature It is：The IGBT driver elements include driving chip and peripheral protection circuit, and wherein peripheral circuit includes the 9th diode, the Ten electric capacity, the 11st electric capacity, current-limiting resistance, buffer resistance, feedback resistance, transistor and optocoupler；The 6 pin connection the of driving chip The anode of nine diodes, by the colelctor electrode of driving IGBT device, 2 pin of driving chip connect simultaneously for the negative electrode connection of the 9th diode One end of 15V power supplys, the tenth capacitance cathode and feedback resistance is connect, 3 pin of driving chip connect the positive pole of the 11st electric capacity simultaneously With one end of buffer resistance, the other end of buffer resistance connected by driving IGBT device as the output end of IGBT driver elements Gate pole；The negative pole of the tenth electric capacity and the 11st electric capacity connects 1 by the emitter stage of driving IGBT device and driving chip simultaneously Pin, 15 pin of driving chip connect one end of current-limiting resistance, the other end connection 15V power supplys of current-limiting resistance, the 14 of driving chip Pin connects the colelctor electrode of transistor, and the emitter stage of transistor is connected with 1 pin of optocoupler, the grid connection microprocessor list of transistor First buffer chip of unit, 6 pin of driving chip are connected with the second output end of overheating detection unit, 5 pin of driving chip and 4 pin of optocoupler are connected, and 3 pin of optocoupler connect the other end of feedback resistance, the 2 pins connection microprocessor unit of optocoupler.

5. the over current fault monitoring and protecting device for flexible DC power transmission Inverter Station according to claim 1, its feature It is：The overheating detection circuit includes the 9th resistance, the tenth resistance, the 11st resistance, the 12nd resistance, the first temperature-sensitive electricity Resistance, the second thermistor, first voltage comparator and second voltage comparator；The in-phase input end of the first voltage comparator Used as the first input end of overheating detection unit, the one end with the first thermistor and the 9th resistance is respectively connected with, the 9th resistance The other end connection dc source VCC, the first thermistor the other end ground connection；The homophase input of the second voltage comparator Hold as the second input of overheating detection unit, the one end with the second thermistor and the 11st resistance is respectively connected with, the tenth The other end connection dc source VCC of one resistance, the other end ground connection of the second thermistor；First voltage comparator and the second electricity The one end of the reverse input end of comparator with the tenth resistance and the 12nd resistance is pressed to be connected, the other end connection of the tenth resistance is straight Stream power supply VCC, the other end ground connection of the 12nd resistance；The signal output part of first voltage comparator is used as overheating detection unit First output end, is connected with microprocessor unit, output alarm signal, and the signal output part of second voltage comparator is used as overheat Second output end of detection unit, the second input with microprocessor unit and IGBT driver elements is connected, output shut-off letter Number.

6. the over current fault monitoring and protecting for flexible DC power transmission Inverter Station according to any one of claim 4 or 5 is filled Put, it is characterised in that：The dispersion current foldback circuit is used to detect the IGBT in composite buffering unit and power converter unit Device constitute bridge arm direct pass electric current, including tertiary voltage comparator, the 13rd resistance, the 14th resistance, the 15th resistance and 16th resistance, the tenth diode and the 11st diode and the first adjustable potentiometer；The tertiary voltage comparator it is in the same direction Input connects one end of the 14th resistance and the anode of the tenth diode, and the negative electrode of the tenth diode is used as dispersion overcurrent protection The input of circuit, the colelctor electrode of each IGBT device in connection power converter unit；One end connection 15V direct currents of the 13rd resistance Power supply, the other end connects the other end of the 14th resistance and a fixing end of the first adjustable potentiometer；First adjustable potentiometer Another fixing end ground connection, the sliding end of the first adjustable potentiometer is connected with one end of the 15th resistance, the 15th resistance The other end connects the reverse input end of tertiary voltage comparator；The positive source connection 15V dc sources of tertiary voltage comparator, One end of 16th resistance, one end of the electric capacity of pin 2 and the tenth of the driving chip of IGBT driver elements；Tertiary voltage comparator Power cathode ground connection, the other end and the 11st diode of the signal output part of tertiary voltage comparator and the 16th resistance Negative electrode is connected, and the anode of the 11st diode connects the drive of IGBT driver elements as the output end of dispersion current foldback circuit The pin 6 of dynamic chip, the signal output part of tertiary voltage comparator connects the second buffer chip of microprocessor unit.

7. the over current fault monitoring and protecting for flexible DC power transmission Inverter Station according to any one of claim 4 or 5 is filled Put, it is characterised in that：The concentration current foldback circuit includes Hall current sensor, the 17th resistance, the 18th resistance, the 19 resistance, the second adjustable potentiometer, the 12nd electric capacity, the 13rd electric capacity and the 4th voltage comparator；Hall current sensor It is installed on the connecting line of tested measuring point, the input in the same direction of the signal output part of Hall current sensor and the 4th voltage comparator End is connected；17th resistance is in parallel with the 12nd electric capacity and then one end is grounded, and the other end connects the in the same direction of the 4th voltage comparator Input, carries out signal filtering；Second fixing end of adjustable potentiometer one accesses 15V power supplys, and another fixing end ground connection is slided End is connected with the reverse input end of the 4th voltage comparator, there is provided feedback voltage；Access 5V power supply conducts in 18th resistance one end Pull-up resistor, the other end connects signal output part and the 19th resistance one end of the 4th voltage comparator；19th resistance it is another One end is connected as an output port for concentrating current foldback circuit with the second buffer chip of microprocessor unit, while Connect one end of the 13rd electric capacity, the other end ground connection of the 13rd electric capacity；19th resistance and the 13rd electric capacity constitute RC retardation ratio Circuit.

8. the over current fault monitoring and protecting device for flexible DC power transmission Inverter Station according to claim 1, its feature It is：The power pack of each unit is provided by the Switching Power Supply exported with plurality of voltages in the device, including output ± 15V, 5V, 3.3V voltage.