CN116961440B - Method, device and equipment for suppressing short-circuit current of direct-current port of power electronic transformer - Google Patents
Method, device and equipment for suppressing short-circuit current of direct-current port of power electronic transformer Download PDFInfo
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- CN116961440B CN116961440B CN202310595867.5A CN202310595867A CN116961440B CN 116961440 B CN116961440 B CN 116961440B CN 202310595867 A CN202310595867 A CN 202310595867A CN 116961440 B CN116961440 B CN 116961440B
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- 230000001629 suppression Effects 0.000 claims abstract description 27
- 238000013016 damping Methods 0.000 claims abstract description 18
- 239000003990 capacitor Substances 0.000 claims description 18
- 238000004364 calculation method Methods 0.000 claims description 15
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- 238000010586 diagram Methods 0.000 description 5
- 230000017525 heat dissipation Effects 0.000 description 4
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- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 238000013528 artificial neural network Methods 0.000 description 1
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- 238000004422 calculation algorithm Methods 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Protection Of Static Devices (AREA)
Abstract
A method, a device and equipment for suppressing short-circuit current of a direct current port of a power electronic transformer are provided, wherein the method comprises the following steps: calculating the theoretical short-circuit current maximum value under the conditions of over-damping critical resistance and under-damping resonance; judging whether a direct current port short circuit fault occurs or not through a fault detection circuit, and detecting the maximum short circuit current value after the short circuit fault occurs; comparing the maximum short-circuit current value with a theoretical short-circuit current maximum value, and if the maximum short-circuit current value is smaller than the theoretical short-circuit current maximum value, putting an over-damping critical resistor as a short-circuit current suppression resistor through an adjustable rheostat; if the maximum short-circuit current value is larger than or equal to the theoretical short-circuit current maximum value, all resistors are put into the adjustable rheostat to serve as short-circuit current suppression resistors, whether the IGBT and the body diode of the power electronic transformer are damaged due to overheat is judged, and if the IGBT and the body diode are damaged, the IGBT and the body diode are replaced after the fault. The invention not only effectively protects the power electronic transformer, but also increases the reliability of the power electronic transformer.
Description
Technical Field
The present invention relates to the field of power electronic transformers, and in particular, to a method, an apparatus, and a device for suppressing short-circuit current at a dc port of a power electronic transformer.
Background
The main structure of the power electronic transformer is that high-voltage alternating current is firstly converted into multi-unit direct current through an AC/DC (alternating current/direct current) converter, then electric isolation and energy transfer are realized through a plurality of multi-unit middle/high-frequency isolation type DC/DC (direct current/direct current) converters, and then direct current electric energy output is obtained through parallel or serial output sides, or alternating current electric energy output is obtained through inversion of the DC/AC (direct current/alternating current) converters. The power electronic transformer is mainly composed of power electronic modules, and when the power electronic transformer experiences internal faults or external faults, unrecoverable breakdown of power electronic devices can occur due to overcurrent and overvoltage, so that the power supply reliability of the power electronic transformer is affected. In order to protect the safety of the power electronic transformer during a fault, the ride-through of the fault can be achieved by blocking the internal module; meanwhile, each port of the power electronic transformer is provided with an outlet breaker as a corresponding backup protection.
When an inter-pole short circuit occurs at the 10 kv DC port, the power electronic devices within the range of the dashed line in fig. 2 are all blocked quickly, and the fault characteristic of the DC port is affected mainly by the electrical isolation of the high-frequency transformer in the isolated DC/DC converter, which is close to the fault point. As shown in fig. 3, after the fault occurs, the capacitive element, the inductive element and the short-circuit fault equivalent resistor in the circuit can generate R-L-C resonance; because the short-circuit fault occurring on the direct-current port is generally a metallic short-circuit, namely the equivalent resistance of the short-circuit point is very small and is generally equivalent to the resistance value of a metal conductor, the short-circuit fault current can cause underdamped resonance; under-damped resonance in the fault scene is divided into two stages, wherein the first-stage resonance current flows between a capacitor, an inductor and a resistor according to a small-dashed line path in fig. 3, and the second-stage resonance current flows through a body diode of a switching device (IGBT and the like) of the full-bridge converter according to a large-dashed line path in fig. 3. However, the power electronic device is basically a semiconductor element, and is fragile compared with the traditional electric element, and the body diode of the IGBT cannot bear short-circuit fault current which exceeds the rated current by multiple times and is damaged in underdamped resonant current in the short-circuit fault, so that the short-circuit current needs to be suppressed to protect related devices through which the short-circuit current flows.
Disclosure of Invention
The invention aims to overcome the defect and problem of poor protection effect of power electronic devices in the prior art, and provides a method, a device and equipment for inhibiting short-circuit current of a direct-current port of a power electronic transformer, which are used for improving the protection effect of the power electronic devices by inhibiting short-circuit current.
In order to achieve the above object, the technical solution of the present invention is: a method for suppressing short-circuit current of a direct current port of a power electronic transformer comprises the following steps:
the fault detection circuit and the power electronic full-control switching device are connected in series between the output inductance of the power electronic transformer and the direct current port, and the adjustable rheostat is connected in parallel with the fault detection circuit and the power electronic full-control switching device;
calculating the theoretical short-circuit current maximum value under the conditions of over-damping critical resistance and under-damping resonance;
judging whether a direct current port short circuit fault occurs or not through a fault detection circuit, and detecting the maximum short circuit current value after the short circuit fault occurs;
the power electronic full-control switch device is switched from an on state to an off state, and the adjustable rheostat is switched from a bypass state to a series connection access state;
comparing the maximum short-circuit current value with a theoretical short-circuit current maximum value, and if the maximum short-circuit current value is smaller than the theoretical short-circuit current maximum value, putting an over-damping critical resistor as a short-circuit current suppression resistor through an adjustable rheostat; if the maximum short-circuit current value is larger than or equal to the theoretical short-circuit current maximum value, all resistors are put into the adjustable rheostat to serve as short-circuit current suppression resistors, whether the IGBT and the body diode of the power electronic transformer are damaged due to overheat is judged, and if the IGBT and the body diode are damaged, the IGBT and the body diode are replaced after the fault.
The over-damping critical resistanceThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is equivalent inductance; />Is equivalent capacitance.
When the DC/DC modules in the power electronic transformer are connected in parallel,short-circuit fault equivalent capacitor of DC/DC module with parallel paths>The method comprises the following steps:
；
in the method, in the process of the invention,the capacitor is a direct current bus capacitor;
when the DC/DC modules in the power electronic transformer are connected in series,short-circuit fault equivalent capacitor of DC/DC module with series circuit>The method comprises the following steps:
。
theoretical short-circuit current maximum value under short-circuit fault under underdamped resonance conditionThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is the voltage of a direct current bus; />Is equivalent inductance; />Is equivalent capacitance.
The method for judging whether the IGBT and the body diode thereof are damaged due to overheat, if so, the IGBT and the body diode are replaced after the fault, and the method comprises the following steps:
calculating current value of IGBT and body diode during under-damped oscillation in follow current stageThe method comprises the following steps:
；
in the method, in the process of the invention,is the voltage of a direct current bus; />Is equivalent inductance; />Is equivalent capacitance; />Is a short circuit fault equivalent resistance; />The time when the occurrence time of the short circuit fault is zero;
in IGBT and body diode thereofIn the follow current stage, the short-circuit current suppressing resistor cuts in the current valueThe method comprises the following steps:
；
in the method, in the process of the invention,IGBT and body diode current when the short-circuit current suppression resistor is cut in; />The internal resistance of the body diode is the internal resistance of the IGBT; />Suppressing the maximum resistance value for the cut-in short-circuit current; />The time when the occurrence time of the short circuit fault is zero;
when the short-circuit current suppression resistor is cut in, the IGBT and the body diode thereof bear heat energyThe method comprises the following steps:
；
in the method, in the process of the invention,the switching-in moment of the adjustable rheostat; />The saturation voltage drop is generated when the IGBT and the body diode thereof are conducted;the on-resistance of the body diode is IGBT;
if IGBTThe thermal energy that the body diode has been subjected toIs greater than or equal to the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Namely:
；
the junction temperature of the IGBT and the body diode thereof exceeds the upper limit of 175 ℃, the IGBT and the body diode thereof are damaged, and the IGBT and the body diode thereof should be replaced after the fault;
if the IGBT and its body diode have been subjected to heat energyLess than the maximum heat energy which can be borne by IGBT and body diode thereof>Namely:
；
the junction temperature of the IGBT and the body diode thereof does not exceed the upper limit of 175 ℃, and the IGBT and the body diode thereof are still normal;
after the short-circuit current suppression resistor is cut in, the IGBT and the body diode generate heat energy until the discharge is completedThe method comprises the following steps:
；
if IGBT and its body diode generate heat energyLess than or equal to the maximum bearable during the follow current stage of IGBT and body diodeHeat energy->Thermal energy which is already received by IGBT and its body diode>I.e.:
；
the junction temperature of the IGBT and the body diode thereof does not exceed the upper limit of 175 ℃, and the IGBT and the body diode element thereof are still normal;
if IGBT and its body diode generate heat energyIs larger than the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Thermal energy which is already received by IGBT and its body diode>I.e.:
；
the IGBT and its body diode junction temperature at this point has exceeded the upper limit of 175 c, and the IGBT and its body diode elements have been damaged and should be replaced after failure.
The IGBT and the body diode thereof can bear the maximum heat energy in the follow current stageThe method comprises the following steps:
；
in the method, in the process of the invention,the upper limit of junction temperature of the IGBT and the body diode thereof; />Is at room temperature; />The thermal resistance of the IGBT and the body diode thereof;
the calculation formula of the thermal resistance of the IGBT and the body diode thereof is as follows:
；
in the method, in the process of the invention,junction-to-case thermal resistance in the transistor; />Is a shell-heat sink thermal resistance; />Is the heat resistance of the radiator.
The adjustable rheostat is cut in at the momentTime of occurrence of short-circuit fault->At the same time, the occurrence time of the short-circuit fault is +.>The calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is equivalent inductance; />Is the voltage of a direct current bus; />Is the maximum short circuit current value; />Is equivalent capacitance.
The device comprises a fault detection circuit, a power electronic full-control switching device and an adjustable rheostat, wherein the fault detection circuit and the power electronic full-control switching device are connected in series between an output inductance of the power electronic transformer and a direct current port together, and the adjustable rheostat is connected with the fault detection circuit and the power electronic switching device in parallel;
the fault detection circuit is used for judging whether a direct current port short circuit fault occurs or not, detecting the maximum short circuit current value after the short circuit fault occurs, and judging the current fault state according to the maximum short circuit current value;
the power electronic full-control switch device is an IGBT and is used for switching from an on state to an off state when a direct current port short circuit fault occurs, so that the adjustable rheostat is switched from a bypass state to a series connection access state;
the adjustable rheostat is used for adjusting the input resistance according to the current fault state.
A short-circuit current suppression device for a direct current port of a power electronic transformer comprises a memory and a processor;
the memory is used for storing computer program codes and transmitting the computer program codes to the processor;
the processor is configured to perform the method according to the instructions in the computer program code.
A computer readable storage medium having stored thereon a computer program which when executed by a processor implements the method described above.
Compared with the prior art, the invention has the beneficial effects that:
according to the method, the device and the equipment for suppressing the short-circuit current of the direct-current port of the power electronic transformer, the calculation and the switching of the short-circuit current limiting resistor do not involve a complex intelligent algorithm, and the calculation is faster and simpler; the related calculation is carried out before and after the fault occurs, and the fault does not need to be calculated at all, and the device action instruction can be sent out by simply judging the numerical value, so that the system is protected more rapidly. Meanwhile, after the short circuit fault occurs, a preset short circuit current suppression resistor is put into the IGBT, the junction temperature of the IGBT and a body diode of the IGBT is suppressed from rising, the IGBT and the body diode of the IGBT are protected from being damaged due to large short circuit current, and the reliability of the power electronic transformer is improved.
Drawings
Fig. 1 is a flowchart of a method for suppressing short-circuit current of a dc port of a power electronic transformer according to the present invention.
Fig. 2 is a schematic circuit diagram of a single-phase power electronic transformer.
Fig. 3 is a schematic diagram of a DC/DC converter pole-to-pole short circuit fault.
Fig. 4 is a schematic structural diagram of a short-circuit current suppressing device for a dc port of a power electronic transformer according to the present invention.
Fig. 5 is a block diagram of a power electronic transformer dc port short-circuit current suppression apparatus according to the present invention.
Fig. 6 is a waveform diagram of a short circuit current without taking protective measures in an embodiment of the invention.
Fig. 7 is a graph of diode freewheel current waveforms without taking protective measures in an embodiment of the present invention.
FIG. 8 is a graph of a short circuit current waveform after the over-damped threshold resistance is applied in an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings and detailed description.
A method for suppressing short-circuit current of a direct current port of a power electronic transformer comprises the following steps:
the fault detection circuit and the power electronic full-control switching device are connected in series between the output inductance of the power electronic transformer and the direct current port, and the adjustable rheostat is connected in parallel with the fault detection circuit and the power electronic full-control switching device;
calculating the theoretical short-circuit current maximum value under the conditions of over-damping critical resistance and under-damping resonance;
the over-damping critical resistanceThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is equivalent inductance; />Is equivalent capacitance;
when the DC/DC modules in the power electronic transformer are connected in parallel,short-circuit fault equivalent capacitor of DC/DC module with parallel paths>The method comprises the following steps:
；
in the method, in the process of the invention,the capacitor is a direct current bus capacitor;
when the DC/DC modules in the power electronic transformer are connected in series,short-circuit fault equivalent capacitor of DC/DC module with series circuit>The method comprises the following steps:
；
theoretical short-circuit current maximum value under short-circuit fault under underdamped resonance conditionThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is the voltage of a direct current bus; />Is equivalent inductance; />Is equivalent capacitance;
judging whether a direct current port short circuit fault occurs or not through a fault detection circuit, and detecting the maximum short circuit current value after the short circuit fault occurs;
the power electronic full-control switch device is switched from an on state to an off state, and the adjustable rheostat is switched from a bypass state to a series connection access state;
maximum short-circuit current valueMaximum value of short-circuit current->Comparing, if the maximum short-circuit current value +.>Less than the theoretical short-circuit current maximum +.>It can be known that the current system is under-damped resonanceA stage, namely a capacitor discharging stage, of putting an over-damping critical resistor as a short-circuit current suppression resistor through an adjustable rheostat; if the maximum short-circuit current value +.>Is greater than or equal to the maximum value of theoretical short-circuit current->The system is shown to be in the second stage of underdamped resonance, namely the inductance and IGBT body diode follow current stage, all resistors are put into the system to serve as short-circuit current suppression resistors through the adjustable varistors, whether the IGBT and the body diode of the power electronic transformer are damaged due to overheating or not is judged, and if the IGBT and the body diode are damaged, the system is replaced after the fault;
when the R-L-C underdamped resonance caused by the current short circuit fault is detected to be in the first stage of capacitor discharge, namely the second stage of body diode freewheeling of the IGBT is not entered, the short circuit current suppression device is connected with the selected overdamped critical resistor to convert the original underdamped resonance into overdamped resonance, so that the short circuit current cannot freewheel through the body diode of the IGBT, expensive and fragile power electronic devices are protected, meanwhile, the short circuit current value is effectively reduced, and the capacitor devices and the inductor devices are effectively protected;
when the fault detection circuit detects that the current short circuit fault is in the underdamped resonance second stage of diode freewheel, the IGBT and a body diode thereof are indicated to bear the impact of the peak value of the short circuit current, the first time is cut into the maximum value to inhibit the short circuit current, the IGBT and the body diode thereof are protected from being damaged due to overhigh junction temperature, and then whether the junction temperature of the diode is over the upper limit due to heat of the body diode of the IGBT before and after the short circuit current inhibition device is cut into is calculated, so that whether the short circuit fault causes damage to the IGBT and the body diode element thereof can be effectively judged, and the method has important guiding significance for maintenance and replacement of devices after the short circuit fault.
Calculating current value of IGBT and body diode during under-damped oscillation in follow current stageThe method comprises the following steps:
；
in the method, in the process of the invention,is the voltage of a direct current bus; />Is equivalent inductance; />Is equivalent capacitance; />Is a short circuit fault equivalent resistance; />The time when the occurrence time of the short circuit fault is zero;
in the follow current stage of IGBT and its body diode, the short-circuit current suppresses the current value after the resistance cuts inThe method comprises the following steps:
；
in the method, in the process of the invention,IGBT and body diode current when the short-circuit current suppression resistor is cut in; />The internal resistance of the body diode is the internal resistance of the IGBT; />Suppressing the maximum resistance value for the cut-in short-circuit current; />The time when the occurrence time of the short circuit fault is zero;
when the short-circuit current suppression resistor is cut in, the IGBT and the body diode thereof bear heat energyThe method comprises the following steps:
；
in the method, in the process of the invention,the switching-in moment of the adjustable rheostat; />The saturation voltage drop is generated when the IGBT and the body diode thereof are conducted;the on-resistance of the body diode is IGBT;
if the IGBT and the body diode bear the heat energyIs greater than or equal to the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Namely:
；
the junction temperature of the IGBT and the body diode thereof exceeds the upper limit of 175 ℃, the IGBT and the body diode thereof are damaged, and the IGBT and the body diode thereof should be replaced after the fault;
if the IGBT and its body diode have been subjected to heat energyLess than the maximum heat energy which can be borne by IGBT and body diode thereof>Namely:
；
the junction temperature of the IGBT and the body diode thereof does not exceed the upper limit of 175 ℃, and the IGBT and the body diode thereof are still normal;
after the short-circuit current suppression resistor is cut in, the IGBT and the body diode generate heat energy until the discharge is completedThe method comprises the following steps:
；
if IGBT and its body diode generate heat energyLess than or equal to the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Thermal energy which is already received by IGBT and its body diode>I.e.:
；
the junction temperature of the IGBT and the body diode thereof does not exceed the upper limit of 175 ℃, and the IGBT and the body diode element thereof are still normal;
if IGBT and its body diode generate heat energyIs larger than the maximum heat energy bearable in the follow current stage of IGBT and its body diode>IGBT and IGBTThe body diode of which is subjected to heat energy +.>I.e.:
；
the junction temperature of the IGBT and the body diode thereof exceeds the upper limit of 175 ℃, the IGBT and the body diode thereof are damaged, and the IGBT and the body diode thereof should be replaced after the fault;
the IGBT and the body diode thereof can bear the maximum heat energy in the follow current stageThe method comprises the following steps:
；
in the method, in the process of the invention,the upper limit of junction temperature of the IGBT and the body diode thereof; />Is at room temperature; />The thermal resistance of the IGBT and the body diode thereof;
the calculation formula of the thermal resistance of the IGBT and the body diode thereof is as follows:
；
in the method, in the process of the invention,junction-to-case thermal resistance in the transistor; />Is a shell-heat sink thermal resistance; />Is the heat resistance of the radiator;
the adjustable rheostat is cut in at the momentTime of occurrence of short-circuit fault->At the same time, the occurrence time of the short-circuit fault is +.>The calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is equivalent inductance; />Is the voltage of a direct current bus; />Is the maximum short circuit current value; />Is equivalent capacitance.
Because the circuit parameters are fixed, the under-damped resonance curve of the short-circuit fault is also fixed, and the time from the occurrence of the fault to the current time can be deduced from the maximum value of the short-circuit current of the under-damped resonance.
According to inductance and capacitance parameters in the power electronic transformer, the resistance value required by over-damped resonance is calculated, and the short-circuit current suppression resistance is set to the value. After the direct-current port short-circuit fault occurs and the power electronic transformer control system locks the switch signal of the switch module, the power electronic full-control switch deviceThe adjustable rheostat is converted from an on state to an off state from a bypass state to a state of series connection, so that the resonance type of the current short-circuit fault is changed, namely the underdamped resonance after the fault is changed to an over-damped resonance, thereby avoiding the follow current of an IGBT body diode of the power electronic transformer in the underdamped resonance process, avoiding the short-circuit current which far exceeds the rated current of the IGBT body diode, reducing the short-circuit current value and effectively protecting a capacitor device and an inductor device.
Example 1:
a 10 kv power electronic transformer prototype of 500 kv amperes for field application will be described as an example. The single-phase circuit of the power electronic transformer is formed by cascading 6 power modules, and can independently operate, and input phase voltage is 5774VAC. Wherein the rated voltage of a high-voltage direct current bus of the high-voltage side H-bridge converter is 1500V, the rated voltage of a direct current bus of the isolated DC/DC converter is 10000V, and a DC/DC module of the isolated DC/DC converter operates in cascade through two paths, so that the DC/DC module has equivalent inductance value2mH, equivalent capacitance value +.>Is 0.2mF, adopts IGBT model Infineon FF225R65T3E3, and has homomorphic voltage drop of body diode +.>3.1V, on-resistance +.>Is 0.06 ohm and the short-circuit failure equivalent resistance +.>Set to 0.1 ohm. The fault detection circuit monitors the maximum short-circuit current value which has been detected currently +.>2000A.
Calculating the critical resistance of over-dampingThe method comprises the following steps:
；
here it may be rounded up to 7 ohms.
Calculating to obtain the theoretical maximum value of short-circuit currentThe method comprises the following steps:
；
if no protection is taken, the short-circuit current waveform is shown in fig. 6, and the diode freewheel current is shown in fig. 7. It is known that the diode freewheeling current is up to more than 3000A, and the rated current 225A and the short-time surge current 450A specified in the far-ultra Infineon FF225R65T3E3 specification will also damage the diode.
In the present embodiment, the maximum short-circuit current is recorded when the fault detection circuit of the short-circuit current suppressing device detects2000A, the failure time can be calculated as:
；
i.e. the current fault detection time has been 0.421 milliseconds from the occurrence of the short circuit fault.
Since the detection circuit has recorded the maximum short-circuit currentIs less than the theoretical short-circuit current maximum value +.>R-L-C under-damped resonance due to short circuit failure does not enter diode freewheelIn this stage, the over-damping critical resistance can be put into the circuit, so that the circuit enters over-damping resonance, and the short-circuit current is shown in fig. 8.
Example 2:
the specific content is the same as that of example 1, except that:
when the fault detection circuit detects that the maximum short-circuit current value is recorded3085A, and the current value has fallen to 2500A, the calculated failure time is:
；
i.e. the current fault detection time has been 3.622 milliseconds from the occurrence of the short circuit fault.
Since the detection circuit has recorded the maximum short-circuit current valueAnd theoretical short-circuit current maximum +.>Similarly, and with a current of 2500A, the R-L-C underdamped resonance caused by this short circuit fault has entered the diode freewheel phase.
Junction-to-case thermal resistance in transistors according to body diode parameters provided by Infinion FF225R65T3E3 module data handbookShell-radiator thermal resistance->Taking the thermal resistance of Infinion FF225R65T3E3 heat dissipation module as an example, the heat dissipation module has a radiator thermal resistance +.>Thus, the body diode thermal resistance of the Infinion FF225R65T3E3 module is:
；
therefore, under the underdamped resonance caused by the short circuit fault, all heat energy which can be born by the IGBT and the body diode thereof in the follow current stage, namely the heat energy required by the junction temperature of the diode crystal to rise from 25 ℃ to 175 ℃ is as follows:
；/>
short-circuit current suppressing resistorWhen the IGBT is cut in at the moment, the heat energy born by the IGBT and the body diode is as follows:
；
after all short-circuit current inhibition resistors are input for 50 ohms, the heat energy of the IGBT and the body diode thereof after the resistors are cut in can be calculated as follows:
；
the diode thermal energy after the short-circuit current suppression resistor cuts in does not exceed the diode thermal energy upper limit:
；
it is known that the input of the short-circuit current suppression resistor prevents the junction temperature of the IGBT and the body diode thereof from exceeding the upper limit, and effectively protects the IGBT and the body diode element thereof in the power electronic transformer.
Example 3:
the specific content is the same as that of example 1, except that:
when the fault detection circuit detects that the maximum short-circuit current value is recorded3085A, and is currently electricIf the current value has fallen to 2000A, the calculated failure time is:
；
i.e. the current fault detection time has been 6.426 milliseconds from the occurrence of the short circuit fault.
Since the detection circuit has recorded the maximum short-circuit current valueAnd theoretical short-circuit current maximum +.>Similarly, and the current value is 2000A, the R-L-C under-damped resonance caused by the short circuit fault already enters the diode freewheel phase.
Junction-to-case thermal resistance in transistors according to body diode parameters provided by Infinion FF225R65T3E3 module data handbookShell-radiator thermal resistance->Taking the thermal resistance of Infinion FF225R65T3E3 heat dissipation module as an example, the heat dissipation module has a radiator thermal resistance +.>Thus, the body diode thermal resistance of the Infinion FF225R65T3E3 module is:
；
therefore, under the underdamped resonance caused by the short circuit fault, all heat energy which can be born by the IGBT and the body diode thereof in the follow current stage, namely heat energy required by the junction temperature of the IGBT and the body diode thereof to rise from 25 ℃ to 175 ℃ is as follows:
；
short-circuit current suppressing resistorWhen the IGBT is cut in at the moment, the heat energy born by the IGBT and the body diode is as follows: />
；
The heat energy generated by the diode before the diode is put into the short-circuit current limiting resistor is larger than the theoretical heat energy upper limit of the IGBT and the body diode thereof;
the current IGBT and the junction temperature of the body diode are calculated as follows:
；
at this time, the junction temperature of the IGBT and its body diode is 256.046 ℃, the upper limit of 175 ℃ has been exceeded, the IGBT and its body diode element have been damaged, and should be replaced after a failure.
Referring to fig. 4, a short-circuit current suppressing device for a dc port of a power electronic transformer is provided, where the device is configured to implement the method described above, and includes a fault detection circuit, a power electronic fully-controlled switching device, and an adjustable varistor, where the fault detection circuit and the power electronic fully-controlled switching device are connected in series between an output inductance of the power electronic transformer and the dc port, and the adjustable varistor is connected in parallel with the fault detection circuit and the power electronic switching device;
the fault detection circuit is used for judging whether a direct current port short circuit fault occurs or not, detecting the maximum short circuit current value after the short circuit fault occurs, and judging the current fault state according to the maximum short circuit current value;
the power electronic full-control switch device is an IGBT and is used for switching from an on state to an off state when a direct current port short circuit fault occurs, so that the adjustable rheostat is switched from a bypass state to a series connection access state;
the adjustable rheostat is used for adjusting the input resistance according to the current fault state.
The hardware structure of the device is simple, and no extra capacitor or inductor is needed.
Referring to fig. 5, a power electronic transformer dc port short circuit current suppression apparatus includes a memory and a processor;
the memory is used for storing computer program codes and transmitting the computer program codes to the processor;
the processor is configured to perform the method as described above according to instructions in the computer program code.
A computer readable storage medium having stored thereon a computer program which when executed by a processor implements the method described above.
In general, the computer instructions to implement the methods of the present invention may be carried in any combination of one or more computer-readable storage media. The non-transitory computer-readable storage medium may include any computer-readable medium, except the signal itself in temporary propagation.
The computer readable storage medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAn), a read-only memory (ROn), an erasable programmable read-only memory (EKROn or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROn), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
The computer program code for carrying out operations of the present invention may be written in one or more programming languages, or combinations thereof, including an object oriented programming language such as Java, snalltalk, C ++ and conventional procedural programming languages, such as the "C" language or similar programming languages, particularly Kython languages suitable for neural network computing and TensorFlow, kyTorch-based platform frameworks may be used. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any number of types of networks, including a Local Area Network (LAN) or a Wide Area Network (WAN), or be connected to an external computer (for example, through the Internet using an Internet service provider).
The above-mentioned devices and non-transitory computer readable storage medium may refer to specific descriptions of the multi-frequency multi-GNSS precise single point positioning method and the beneficial effects, and are not repeated here.
While embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (10)
1. The method for suppressing the short-circuit current of the direct-current port of the power electronic transformer is characterized by comprising the following steps of:
the fault detection circuit and the power electronic full-control switching device are connected in series between the output inductance of the power electronic transformer and the direct current port, and the adjustable rheostat is connected in parallel with the fault detection circuit and the power electronic full-control switching device;
calculating the theoretical short-circuit current maximum value under the conditions of over-damping critical resistance and under-damping resonance;
judging whether a direct current port short circuit fault occurs or not through a fault detection circuit, and detecting the maximum short circuit current value after the short circuit fault occurs;
the power electronic full-control switch device is switched from an on state to an off state, and the adjustable rheostat is switched from a bypass state to a series connection access state;
comparing the maximum short-circuit current value with a theoretical short-circuit current maximum value, and if the maximum short-circuit current value is smaller than the theoretical short-circuit current maximum value, putting an over-damping critical resistor as a short-circuit current suppression resistor through an adjustable rheostat; if the maximum short-circuit current value is larger than or equal to the theoretical short-circuit current maximum value, all resistors are put into the adjustable rheostat to serve as short-circuit current suppression resistors, whether the IGBT and the body diode of the power electronic transformer are damaged due to overheat is judged, and if the IGBT and the body diode are damaged, the IGBT and the body diode are replaced after the fault.
2. The method for suppressing short-circuit current of direct current port of power electronic transformer as recited in claim 1, wherein said over-damping critical resistanceThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is equivalent inductance; />Is equivalent capacitance.
3. A method for suppressing a short-circuit current at a DC port of a power electronic transformer according to claim 2,
when the DC/DC modules in the power electronic transformer are connected in parallel,short-circuit fault equivalent capacitor of DC/DC module with parallel paths>The method comprises the following steps:
；
in the method, in the process of the invention,the capacitor is a direct current bus capacitor;
when the DC/DC modules in the power electronic transformer are connected in series,short-circuit fault equivalent capacitor of DC/DC module with series circuit>The method comprises the following steps:
。
4. the method for suppressing short-circuit current of direct-current port of power electronic transformer according to claim 1, wherein theoretical short-circuit current maximum value under-damped resonance condition after short-circuit faultThe calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is the voltage of a direct current bus; />Is equivalent inductance; />Is equivalent capacitance.
5. The method for suppressing short-circuit current of dc port of power electronic transformer according to claim 1, wherein said determining whether the IGBT and the body diode of the power electronic transformer are damaged due to overheat, if damaged, is replaced after the fault, comprises:
calculating current value of IGBT and body diode during under-damped oscillation in follow current stageThe method comprises the following steps:
；
in the method, in the process of the invention,is the voltage of a direct current bus; />Is equivalent inductance; />Is equivalent capacitance; />Is a short circuit fault equivalent resistance; />The time when the occurrence time of the short circuit fault is zero;
in the follow current stage of IGBT and its body diode, the short-circuit current suppresses the current value after the resistance cuts inThe method comprises the following steps:
；
in the method, in the process of the invention,IGBT and body diode current when the short-circuit current suppression resistor is cut in; />The internal resistance of the body diode is the internal resistance of the IGBT; />Suppressing the maximum resistance value for the cut-in short-circuit current; />The time when the occurrence time of the short circuit fault is zero;
when the short-circuit current suppression resistor is cut in, the IGBT and the body diode thereof bear heat energyThe method comprises the following steps:
；
in the method, in the process of the invention,the switching-in moment of the adjustable rheostat; />The saturation voltage drop is generated when the IGBT and the body diode thereof are conducted; />The on-resistance of the body diode is IGBT;
if the IGBT and the body diode bear the heat energyIs greater than or equal to the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Namely:
；
the junction temperature of the IGBT and the body diode thereof exceeds the upper limit of 175 ℃, the IGBT and the body diode thereof are damaged, and the IGBT and the body diode thereof should be replaced after the fault;
if the IGBT and its body diode have been subjected to heat energyLess than the maximum heat energy bearable by IGBT and its body diodeNamely:
；
the junction temperature of the IGBT and the body diode thereof does not exceed the upper limit of 175 ℃, and the IGBT and the body diode thereof are still normal;
after the short-circuit current suppression resistor is cut in, the IGBT and the body diode generate heat energy until the discharge is completedThe method comprises the following steps:
；
if IGBT and its body diode generate heat energyLess than or equal to the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Thermal energy which is already received by IGBT and its body diode>I.e.:
；
the junction temperature of the IGBT and the body diode thereof does not exceed the upper limit of 175 ℃, and the IGBT and the body diode element thereof are still normal;
if IGBT and its body diode generate heat energyIs larger than the maximum heat energy bearable in the follow current stage of IGBT and its body diode>Thermal energy which is already received by IGBT and its body diode>I.e.:
；
the IGBT and its body diode junction temperature at this point has exceeded the upper limit of 175 c, and the IGBT and its body diode elements have been damaged and should be replaced after failure.
6. The method for suppressing a short-circuit current at a DC port of a power electronic transformer according to claim 5, wherein,
the IGBT and the body diode thereof can bear the maximum heat energy in the follow current stageThe method comprises the following steps:
；
in the method, in the process of the invention,the upper limit of junction temperature of the IGBT and the body diode thereof; />Is at room temperature; />The thermal resistance of the IGBT and the body diode thereof;
the calculation formula of the thermal resistance of the IGBT and the body diode thereof is as follows:
；
in the method, in the process of the invention,junction-to-case thermal resistance in the transistor; />Is a shell-heat sink thermal resistance; />Is the heat resistance of the radiator.
7. The method for suppressing a short-circuit current at a dc port of a power electronic transformer according to claim 5, wherein said adjustable varistor is switched in at a timeTime of occurrence of short-circuit fault->At the same time, the short circuit fault occursRaw time->The calculation formula of (2) is as follows:
；
in the method, in the process of the invention,is equivalent inductance; />Is the voltage of a direct current bus; />Is the maximum short circuit current value; />Is equivalent capacitance.
8. A power electronic transformer direct current port short-circuit current suppression device, characterized in that the device is used for realizing the method of any one of claims 1-7, the device comprises a fault detection circuit, a power electronic fully-controlled switching device and an adjustable rheostat, the fault detection circuit and the power electronic fully-controlled switching device are connected in series between an output inductance of the power electronic transformer and the direct current port together, and the adjustable rheostat is connected with the fault detection circuit and the power electronic switching device in parallel;
the fault detection circuit is used for judging whether a direct current port short circuit fault occurs or not, detecting the maximum short circuit current value after the short circuit fault occurs, and judging the current fault state according to the maximum short circuit current value;
the power electronic full-control switch device is an IGBT and is used for switching from an on state to an off state when a direct current port short circuit fault occurs, so that the adjustable rheostat is switched from a bypass state to a series connection access state;
the adjustable rheostat is used for adjusting the input resistance according to the current fault state.
9. A short-circuit current suppression device for a DC port of a power electronic transformer is characterized in that,
comprising a memory and a processor;
the memory is used for storing computer program codes and transmitting the computer program codes to the processor;
the processor being configured to perform the method of any of claims 1 to 7 according to instructions in the computer program code.
10. A computer readable storage medium, characterized in that the computer readable storage medium has stored thereon a computer program which, when executed by a processor, implements the method according to any of claims 1 to 7.
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