Background
The direct current fuse is an important protection device of a direct current power system such as a ship direct current power system, a rail transit power system, a transformer substation direct current system and the like. With the rapid development of these power systems, the rated voltage and breaking capacity of the dc fuses are also increasing. In the development process of the direct current fuse, performance verification needs to be carried out on the designed fuse. The short circuit test is one of the main tests for verifying the performance of the fuse. The short circuit test is mainly used for analyzing the performance of the direct current fuse, simulating the worst working condition, namely the direct current short circuit of the direct current bus, and analyzing the fusing performance-fusing characteristic and the fusing heat energy value I2t of the fuse by collecting the short circuit current in the fusing process of the fuse. The fusing characteristics, also known as the time-current characteristics or ampere-second characteristics of the fuse, are the most important electrical performance indicators of the fuse; the melting heat energy value I2t refers to the energy value required by the fuse link to blow, and is a key technical index for evaluating the surge bearing capacity of the fuse. The typical circuit is tested against national standards and has recommended breaking capacity. The method is selected by Chen Yujun of the national daily electrical appliance quality supervision and inspection center in the analysis and selection of the breaking test process of a small-sized breaker, and the same typical circuit is adopted by Chen Yingxia of Shanghai university electronic information and electric engineering college in the research and development of a comprehensive automatic tester for fuses. The typical circuit has the greatest advantages of simple and reliable circuit, great impact on a power grid, high energy consumption and very high test cost. In the patent aspect, the invention of a high-current short circuit test for a direct-current fuse is not available at present.
The power module is an important component of the frequency converter, and the thermal calculation is one of important aspects of the power module selection, and the heating and reliability calculation is gradually out of the category of empirical estimation or imitation at present and is replaced by accurate simulation calculation. Since the power device inevitably generates a large amount of heat during the operation of the switch, it needs to be carried away by means of an external heat dissipation system. The direct consequence of incomplete or untimely heat dissipation is that the device is too hot, the crystal structure of the chip changes irreversibly and fails, and short circuits or other explosion events are caused seriously. Therefore, the simulation calculation and the test ensure that the device does not exceed a given temperature under any running state, and the simulation calculation and the test are the main contents of the heat circuit design of the power electronic equipment. However, the simulation calculation needs to be based on a certain aging test, i.e. the temperature rise of the power module in a certain time is tested under the condition of full power operation of the power module, and the temperature rise is compared with the simulation result to verify the accuracy of the simulation.
The invention discloses a comprehensive aging test platform for a UPFC power module, which comprises a UPFC power module IGBT circuit board, a loaded high-power resistor, a test case, a DC/DC module, a direct-current stabilized power supply, a radiator and a temperature control module.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the power module and the direct current fuse short circuit test platform are high in utilization rate, low in cost, stable and reliable.
In order to solve the technical problems, the invention adopts the following technical scheme: the circuit comprises a power module aging test loop and a fuse short-circuit test loop, wherein the power module aging test loop comprises a switch cabinet with an input end connected with a 380V power supply, an output end of the switch cabinet is connected with an input end of a three-phase electric voltage regulator, and the three-phase electric voltage regulator is an electric voltage regulator with a voltage regulation range of 0-650V; the output end of the three-phase electric voltage regulator is connected with the input end of the rectifying cabinet, and the rectifying cabinet rectifies the adjustable alternating voltage generated by the three-phase electric voltage regulator to generate 0-1200V direct voltage at the direct current source output end of the rectifying cabinet; the output end of the rectifying cabinet is divided into two branches, the first branch is connected with the input end of the power module cabinet, and the output end of the power module cabinet is connected with the reactor cabinet;
the power module cabinet at least comprises two power modules, the power modules adopt a back-to-back connection mode when the power module cabinet is tested, the reactor cabinet is used as a load when the power module aging test is carried out, each power module comprises an IGBT module and a signal acquisition card, the IGBT module is integrated with an NTC resistor, an external interface of the IGBT module comprises a temperature interface, the PLC is connected with an upper computer through a network cable, and current and voltage values can be displayed on the upper computer through a display interface;
when the power module aging test is carried out, the NTC resistor is used as a temperature measuring element, a temperature interface of the TGBT module is connected with a signal acquisition card through a cable, the signal acquisition card of each power module is connected with a hub6 through a network cable, the hub6 is connected with a PLC through the network cable, and the signal acquisition card converts a temperature signal into a normal temperature value and then sends the normal temperature value to the PLC through the network cable so as to monitor the temperature of each power module IGBT module in real time;
the fuse short circuit test loop comprises a pre-charging breaker with a wire inlet end connected with a second path of the output end of the rectifying cabinet, a wire outlet end of the pre-charging breaker is connected with a direct current capacitor group, the direct current capacitor group is also connected with a wire inlet end of a 4p frame breaker which is remotely controlled by plc and can be closed in a short circuit test to switch on the loop so as to provide short circuit direct current voltage for the fuse, the wire outlet end of the 4p frame breaker is connected with a tested product, and a discharging resistor is connected with a discharging breaker in series and connected with two ends of the capacitor group in parallel.
Preferably, the device also comprises a current and voltage transmitter which is simultaneously connected with the direct current capacitor bank and the tested object and used for converting the direct current capacitor bank and the current flowing through the tested object into 1V-5V direct current voltage which is output according to the linear proportion, wherein the current and voltage transmitter is connected with an analog input module of the PLC, and the analog input module converts the analog current and voltage into digital quantity which can be received by a CPU of the PLC so as to enable the PLC program to process and obtain specific current and voltage values.
Preferably, the DC capacitor group is composed of 36 capacitors with 420 mu F connected in parallel, and all frequency converters in the DC system are simulated in a fuse short circuit test.
Preferably, the 4p frame circuit breaker has a frame current of 1600A and a current breaking capacity of 690V/85kA (rms).
Preferably, the output end of the switch cabinet is also connected with a heat radiation fan for radiating heat of the electric voltage regulator and the rectifier cabinet.
The beneficial effects of the invention are as follows: the platform is used for conducting a fuse short circuit test and an aging test of a frequency converter power module, and verifying the performance of a designed fuse and the accuracy of simulation of the frequency converter power module through the comparative analysis of test results and simulation results. The method has the advantages that the method is safe and reliable in effect, can realize multiple functions, can effectively verify the performance of the designed fuse and the simulation accuracy of the frequency converter power module, and is characterized in that a rectifier used in a fuse short-circuit test has no special requirement, a large-capacity rectifier required in a traditional test is not needed, and the existence of the pre-charging circuit breaker enables the method to avoid huge impact on a power grid caused by connection and disconnection in a large-current short-circuit test. And the power module aging test can be carried out under the condition of almost not consuming power grid energy by back-to-back test and taking the reactor as a load, so that the test cost and the occupied space are reduced.
The test platform can also be used for other test purposes such as inductive load test, long-time reliability test and the like, and has low test cost, stability and reliability.
Detailed Description
Specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.
As shown in fig. 1-2, a power module and a dc fuse short-circuit test platform, the circuit of which comprises a power module aging test loop and a fuse short-circuit test loop, the power module aging test loop comprises a switch cabinet with an input end connected with a 380V power supply, an output end of the switch cabinet 1 is connected with an input end of a three-phase electric voltage regulator 2, and the voltage regulator 2 is an electric voltage regulator with a voltage regulation range of 0-650V. The output end of the three-phase electric voltage regulator 2 is connected with the input end of the rectifying cabinet 3, and the rectifying cabinet 3 rectifies the adjustable alternating voltage generated by the electric voltage regulator to generate 0-1200V direct voltage at the direct current source output end of the rectifying cabinet. The output end of the rectifying cabinet 3 is divided into two branches, the first branch is connected with the input end of the power module cabinet 4, and the output end of the power module cabinet 4 is connected with the reactor cabinet 5; the output end of the switch cabinet 1 is also connected with a heat radiation fan 10 which radiates heat to the electric voltage regulator 2 and the rectifying cabinet 3.
The power module cabinet 4 at least comprises two power modules, the power modules adopt a back-to-back connection mode when the test is carried out, the reactor cabinet 5 is used as a load when the power module aging test is carried out, and the reactor is a pure inductive load, so that active power is not consumed theoretically, and an external direct current source only provides loss for the system. The reactor is used as a load, and the topological structure can test the temperature rise of the tested power module under the full power condition and the reliability of the power module, and meanwhile, the power module does not consume too much energy of a power grid. The number of power modules which can be tested simultaneously in theory has no upper limit, each power module comprises an IGBT module and a signal acquisition card, the IGBT module integrates an NTC resistor, and an external interface of the IGBT module comprises a temperature interface;
when the power module aging test is carried out, the NTC resistor is used as a temperature measuring element, a temperature interface of the TGBT module is connected with a signal acquisition card through a cable, the signal acquisition card of each power module is connected with a hub6 through a network cable, the hub6 is connected with a PLC through the network cable, and the signal acquisition card converts a temperature signal into a normal temperature value and then sends the normal temperature value to the PLC through the network cable so as to monitor the temperature of each power module IGBT module in real time; the PLC is connected with the upper computer through a network cable, the temperature value can be displayed on the upper computer through a display interface, and the PLC can also guide data to the upper computer.
The fuse short circuit test loop comprises a pre-charging breaker 11 with a wire inlet end connected with a second path of the output end of the rectifying cabinet 3, the wire outlet end of the pre-charging breaker 11 is connected with a direct current capacitor bank 12, the direct current capacitor bank 12 is formed by connecting 36 capacitors with 420 mu F in parallel, and all frequency converters in the direct current system are simulated in the fuse short circuit test. The direct current capacitor bank 12 is also connected with the wire inlet end of a 4p frame circuit breaker 15 which is remotely controlled by plc and can be closed in a short circuit test to switch on a loop so as to provide short circuit direct current voltage for the fuse, the wire outlet end of the 4p frame circuit breaker 15 is connected with a tested product 16, the frame current of the 4p frame circuit breaker 15 is 1600A, and the current breaking capacity is 690V/85kA (rms). The discharging resistor 13 is connected in series with the discharging breaker 14 and connected in parallel to the two ends of the capacitor group 7. The voltage of the capacitor bank 7 can be brought below 50V within 5 minutes.
The PLC also comprises a current and voltage transmitter 9 which is simultaneously connected with the direct current capacitor bank 12 and the tested object 16 so as to convert the direct current capacitor bank 12 and the current flowing through the tested object 16 into 1V-5V direct current voltage which is output according to the linear proportion, wherein the current and voltage transmitter 9 is connected with an analog input module of the PLC, and the analog input module converts the analog current and voltage into digital quantity which can be received by a CPU of the PLC so as to enable the PLC program to process and obtain specific current and voltage values. The PLC is connected with the upper computer through a network cable, and the upper computer can display current and voltage values through a display interface.
In the case of a short-circuit test, all the circuit breakers of the switchgear 1 are first opened, and then the fuse is mounted at the test object 16.
Then, the power grid breaker of the test platform is closed to be connected with the mains supply, and the power indicator lamp of the switch cabinet 1 is lightened.
Through the operation at cubical switchboard and switch board, start electric voltage regulator 2 and rectifier cabinet 3, charge for DC capacitor bank 12 through the direct current that electric voltage regulator 2 and rectifier cabinet 3 output, adjust electric voltage regulator 2 and rectifier cabinet 3 and make the direct current voltage change, simultaneously through the voltage at monitoring DC capacitor bank 12 both ends, just can break off pre-charge circuit breaker 11 through the PLC controller after DC capacitor bank 12 is full-charged, open electric circuit breaker 14 simultaneously, utilize DC capacitor bank 7 to simulate all converters in the DC system. The purpose of opening the pre-charge circuit breaker 11 is to avoid the huge impact on the grid caused by the switching on and off during high current short circuit tests. At this time, the plc remote control 4p frame breaker 15 of the control cabinet is switched on, which is equivalent to short-circuiting the two ends of the dc capacitor bank 12 by the fuses, the short-circuit current will continuously increase until the I2t of the fuses reaches the I2t before the arc, the short-circuit current starts to decrease due to the continuous increase of the fuse resistance until the fuse is finally melted, and the short-circuit current will be 0.
At this time, the PLC detects that the current through the fuse becomes 0, closes the discharge breaker 14, releases the voltage in the dc capacitor bank 12 through the discharge resistor 13, and discharges to 50V or less within 5 minutes.
The PLC is connected with the upper computer through a network cable, the current and voltage values can be displayed on the upper computer through a display interface, and the PLC can also lead the data to the upper computer. Then, the pre-arc I2t of the fuse can be accurately calculated through an integral program, and the fusing characteristic of the fuse is obtained. And then, utilizing MATLAB modeling, and comparing and analyzing a test result and a simulation result to verify the rationality of the designed fuse.
The standard power module aging test is mainly used for carrying out full power operation test on the power modules, and the power module aging test is mainly realized through back-to-back test, namely, two groups of power modules in the system are connected back-to-back through reactors, and the connection mode is specifically shown in figure 2.
The rectifying module provides 1100V direct current voltage for the busbar of the power module cabinet of D1 and D2, direct current on the direct current busbar is converted into alternating current through the power module D1, and the alternating current is converted into direct current through the power module D2 after passing through the reactor cabinet 5, so that an energy cycle is formed. Let the input voltage of power module cabinet be VDC, then the effective voltage of power module D1, D2 alternating current section is respectively:
wherein m1 and m2 are modulation factors. In the experiment m1=m2, i.e. u1=u2. Because alternating current is a vector, the output of the two power modules can generate voltage difference by adjusting the phase difference mode of the U1 and the U2, so that load current is generated, and finally, the current in the loop reaches the rated current of the power modules by adjusting the phase difference of the U1 and the U2. In the aging test process of the power module, the PLC of the control cabinet is used for controlling the power module, the modulation factor of the power module is usually set to be 1.0, the phase angle of the network side power module is set to be 0, and the phase difference phi between the modules at the network side and the machine side is slowly adjusted to enable the voltage difference to be generated between the input and the output of the load reactor until rated current is generated. Each power module comprises an IGBT module and a signal acquisition card, wherein the IGBT module is integrated with an NTC resistor and comprises a temperature interface in an external interface of the IGBT module. When the power module aging test is carried out, the NTC resistor is used as a temperature measuring element, the temperature interface of the TGBT is connected with the signal acquisition card through a cable, the signal acquisition card converts a temperature signal into a normal temperature value and then sends the normal temperature value to the PLC through a network cable, the temperature of the IGBT module can be monitored in real time by the PLC, the PLC is connected with the upper computer through the network cable, the temperature value can be displayed on the upper computer through the display interface, and the PLC can also guide the data to the upper computer. Meanwhile, the PLC can collect bus voltage through a sensor in the module, so that real-time monitoring is performed, and protection of equipment, such as overvoltage protection, is realized.
When the power module and the direct current fuse short circuit test platform carry out power module aging test, the power modules are required to be tested in groups, namely, the power module cabinet at least comprises two power modules, and the number of the power modules which can be tested simultaneously in theory has no upper limit, compared with the traditional test, the test efficiency of only one power module can be improved by N times, and when a plurality of power modules carry out the test, the signal acquisition card of each power module is connected with the hub6 through a network cable, and the hub6 is connected with the PLC through the network cable, so that the PLC can monitor the temperature of each power module IGBT module in real time.
The above-described embodiments are merely illustrative of the principles and functions of the present invention, and some of the practical examples, not intended to limit the invention; it should be noted that modifications and improvements can be made by those skilled in the art without departing from the inventive concept, and these are all within the scope of the present invention.