CN111884200B - Automatic switching circuit and method for two-way direct-current input power supply of power electronic converter - Google Patents

Automatic switching circuit and method for two-way direct-current input power supply of power electronic converter Download PDF

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Publication number
CN111884200B
CN111884200B CN202010873653.6A CN202010873653A CN111884200B CN 111884200 B CN111884200 B CN 111884200B CN 202010873653 A CN202010873653 A CN 202010873653A CN 111884200 B CN111884200 B CN 111884200B
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branch
power supply
main
standby
direct
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CN111884200A (en
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彭力
徐茂宁
刘新民
康勇
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/109—Scheduling or re-scheduling the operation of the DC sources in a particular order, e.g. connecting or disconnecting the sources in sequential, alternating or in subsets, to meet a given demand
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H11/00—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result
    • H02H11/002—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result in case of inverted polarity or connection; with switching for obtaining correct connection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/345—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering using capacitors as storage or buffering devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/061—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for DC powered loads
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/322—Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses an automatic switching circuit and method of two paths of direct current input power supplies of a power electronic converter, wherein the circuit structure comprises the following steps: the main/standby direct current power supply comprises a pre-charging branch, a working branch, a switching branch, a de-pumping voltage branch and a negative working branch. Pre-charging of an electrolytic capacitor at a direct current input side before starting up of the power electronic converter is realized by utilizing a main/standby direct current power supply pre-charging branch circuit; the main or standby direct-current power supply after the power electronic converter is started is supplied with power by using the main/standby direct-current power supply working branch, the cathode working branch and the switching branch, and the main/standby direct-current power supply is quickly switched according to the power supply condition of the main/standby direct-current power supply when the subsequent power electronic converter works; the pump-up voltage of the electrolytic capacitor is removed when the load of the motor is decelerated or suddenly stopped by using the main/standby direct-current power supply pump-up voltage branch circuit and the working branch circuit. The invention has reliable principle and convenient realization.

Description

Automatic switching circuit and method for two-way direct-current input power supply of power electronic converter
Technical Field
The invention belongs to the field of power electronic converters, and particularly relates to an automatic switching circuit and method of two paths of direct current input power supplies of a power electronic converter.
Background
As the application of power electronic converters is becoming more extensive, people also put higher demands on their safety. The direct current input side of the power electronic converter faces the problems of overlarge direct charging current of an electrolytic capacitor, higher fault shutdown probability when one direct current power supply supplies power and overhigh pumping voltage of the electrolytic capacitor when the load of a motor decelerates or suddenly stops in the working process, and the problems can influence the safe and stable operation of the power electronic converter.
When the existing power supply scheme aiming at the direct current power supply of the power electronic converter solves the problems of overlarge charging current of an electrolytic capacitor and power supply of a single power supply, a main direct current power supply and a standby direct current power supply are arranged, and the two direct current power supplies are switched through a contactor or an IGBT (insulated gate bipolar transistor), so that certain limitation exists, and the flexibility and the reliability are not high. In addition, the pre-charging branch and the switching branch are set to be the same branch in the existing scheme, the designed resistance value is large, the charging process is slow, and the switching process is slow when the direct current main/standby direct current power supply is switched. When the problem of pumping voltage is solved, the existing solution is to connect a branch of a resistor in series with an IGBT in parallel on a dc capacitor, and when the pumping voltage exists, the IGBT is turned on to release energy, so that the economy is not high, and the complexity of the circuit is increased.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides an automatic switching circuit and method of two paths of direct current input power supplies of a power electronic converter, and aims to solve the technical problems that the direct charging current of an electrolytic capacitor is overlarge, the fault shutdown probability is high when one path of direct current power supply supplies power, and the pumping voltage of the electrolytic capacitor is overhigh when the load of a motor is decelerated or suddenly stopped.
In order to achieve the above object, an aspect of the present invention provides an automatic switching circuit for two dc input power sources of a power electronic converter, including: two power supply modules, a power electronic converter DC input side electrolytic capacitor;
wherein the power module includes: the system comprises a positive and negative connecting end of a direct current power supply, a pre-charging branch, a working branch, a switching branch, a de-pumping voltage branch and a negative working branch; the two power supply modules are mutually used as a master and a standby;
the pre-charging branch, the working branch and the switching branch are connected in parallel and are positioned between the positive electrode of the direct-current power supply and the positive electrode of the electrolytic capacitor; the de-pumping voltage branch is connected with the negative working branch in parallel and is positioned between the negative electrode of the direct current power supply and the negative electrode of the electrolytic capacitor;
the pre-charging branch is composed of a first contactor and a first current-limiting resistor; the working branch is composed of a second contactor; the switching branch is composed of a first thyristor and a second current-limiting resistor; the de-pumping voltage branch is composed of a second thyristor; the negative working branch is composed of a diode.
Further, the pre-charging branch is composed of a first contactor and a first current-limiting resistor. The driving power of the first contactor is low, and auxiliary electricity of the control circuit can be directly used as a driving power supply; the resistance and power of the first current-limiting resistor are designed to be appropriately large, so that the pre-charging current can be effectively reduced.
Furthermore, in the switching branch circuit, one end of the second current-limiting resistor is connected with the cathode of the first thyristor, and the other end of the second current-limiting resistor is connected with the anode of the electrolytic capacitor; or one end of the second current-limiting resistor is connected with the positive electrode of the direct-current power supply, and the other end of the second current-limiting resistor is connected with the anode of the first thyristor. The conduction speed of the first thyristor is high; the resistance value of the second current-limiting resistor is designed to be small, the charging speed is high, the switching time is short, and the value of the resistance value is designed to ensure that the current caused by the voltage difference of the main/standby direct current power supply is smaller than a limit value in the switching process of the main/standby direct current power supply.
Furthermore, the working branch is directly formed by a contactor, the working current is large, the driving power of the contactor is large, and the output voltage of the power electronic converter after working is required to be used as the driving power supply of the power electronic converter. In addition, the contactor has small conduction loss and small conduction voltage drop, and the voltage at two ends of the thyristor of the switching branch circuit driven by narrow pulse can be basically 0. Therefore, when the working branch is conducted, the thyristor of the switching branch kept conducted by the latch effect is automatically turned off.
Furthermore, in the de-pumping voltage branch, the anode of the second thyristor is connected with the cathode of the direct current power supply, and the cathode of the second thyristor is connected with the cathode of the electrolytic capacitor.
Furthermore, in the negative working branch, the cathode of the diode is connected with the negative electrode of the direct current power supply, and the anode of the diode is connected with the negative electrode of the electrolytic capacitor.
In order to achieve the above object, in another aspect, the present invention further provides an automatic switching method for two dc input power sources of a power electronic converter, where the automatic switching circuit includes:
(1) before the power electronic converter is started to work, when a main direct current power supply is normal, a pilot leads to a main pre-charging branch circuit to pre-charge an electrolytic capacitor at the direct current input side of the power electronic converter;
(2) when the power electronic converter is started to work, the main switching branch is conducted and the main pre-charging branch is cut off, and after a first preset time, the main working branch is conducted and the main switching branch is cut off at the same time;
(3) in the working process of the power electronic converter, under the condition that the standby direct-current power supply is normal, when the main direct-current power supply is suddenly powered off, the standby switching branch is switched on in a pilot mode, after the second preset time, the standby working branch is switched on, the standby switching branch is switched off at the same time, and finally the main working branch is switched off; when the condition that the main direct-current power supply is recovered to be normal is detected to reach a third preset time, the pilot switches on the main switching branch, after the fourth preset time, the main working branch is switched on, the main switching branch is switched off, and finally the standby working branch is switched off;
(4) when the motor load carried by the power electronic converter decelerates or suddenly stops, the pumping voltage is released by conducting the corresponding pump-up voltage removing branch and the working branch.
In order to achieve the above object, in another aspect, the present invention further provides an automatic switching method for two dc input power sources of a power electronic converter, where the automatic switching circuit includes:
(1) before the power electronic converter is started to work, when a main direct-current power supply is abnormal and a standby direct-current power supply is normal, a standby pre-charging branch is switched on in a pilot mode to pre-charge an electrolytic capacitor at the direct-current input side of the power electronic converter;
(2) when the power electronic converter is started to work, the standby switching branch is conducted and the standby pre-charging branch is cut off, and after the fifth preset time, the standby working branch is conducted and the standby switching branch is cut off at the same time;
(3) in the working process of the power electronic converter, when the fact that the restoration of the main direct-current power supply is normal is detected to reach the sixth preset time, the pilot switches on the main switching branch, after the seventh preset time, the main working branch is switched on, the main switching branch is cut off, and finally the standby working branch is cut off;
(4) when the motor load carried by the power electronic converter decelerates or suddenly stops, the pumping voltage is released by conducting the corresponding pump-up voltage removing branch and the working branch.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) the main/standby direct current power supply pre-charging branch, the working branch and the switching branch are connected in parallel and are positioned between the positive electrode of the direct current power supply and the positive electrode of the electrolytic capacitor; the main/standby direct current power supply de-pumping voltage branch circuit is connected with the negative working branch circuit in parallel and is positioned between the negative electrode of the direct current power supply and the negative electrode of the electrolytic capacitor. Through controlling the on-off of each branch circuit, the pre-charging of the electrolytic capacitor at the direct current input side of the power electronic converter, the power supply of the main/standby direct current power supply, the quick switching of the main/standby direct current power supply and the removal of the pumping voltage of the electrolytic capacitor are realized, the principle is reliable, and the realization is convenient.
(2) The working branch is directly formed by the contactor, and the voltage at two ends of the switching branch thyristor driven by narrow pulse is basically 0 due to small conduction loss and small conduction voltage drop of the contactor, so that the switching branch thyristor kept in conduction by the latch-up effect is automatically turned off when the working branch is conducted.
(3) The resistance value of the current-limiting resistor in the pre-charging branch circuit is valued according to the condition that the initial electrifying current of the electrolytic capacitor does not overshoot before the power electronic converter works, the resistance value of the current-limiting resistor in the switching branch circuit is valued according to the condition that the current does not exceed the allowable upper limit in the switching process, the pre-charging of the electrolytic capacitor is realized, and the switching time is shortened.
(4) According to the invention, the cathode of the diode is connected with the cathode of the direct current power supply, and the anode of the diode is connected with the cathode of the electrolytic capacitor, so that the anode and the cathode of the direct current power supply are prevented from being reversely connected, and the electrolytic capacitor and equipment are prevented from being damaged.
Drawings
Fig. 1 is a schematic diagram of an automatic switching circuit of two dc input power sources of a power electronic converter according to the present invention;
wherein: 1-main direct current power supply anode, 2-standby direct current power supply anode, 3-main direct current power supply cathode, 4-standby direct current power supply cathode, 5-main pre-charging branch, 6-main working branch contactor, 7-main switching branch, 8-standby pre-charging branch, 9-standby working branch contactor, 10-standby switching branch, 11-main de-pumping voltage branch thyristor, 12-main cathode working branch diode, 13-standby de-pumping voltage branch thyristor, 14-standby cathode working branch diode, 15-power electronic converter direct current input side electrolytic capacitor, 16-power electronic converter, 51, 81-contactor, 52, 72, 82. 102-current limiting resistor, 71, 101-thyristor.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention is further explained below with reference to the drawings.
As shown in fig. 1, the schematic diagram of an automatic switching circuit for two-way dc input power of a power electronic converter according to the present invention includes a main/standby power pre-charging branch, a working branch, a switching branch, a de-pumping voltage branch, and a negative working branch.
Specifically, the main/backup dc power supply pre-charging branches 5 and 8 are composed of contactors 51 and 81 and current-limiting resistors 52 and 82 with large resistance values, the main/backup dc power supply switching branches 7 and 10 are composed of thyristors 71 and 101 and current-limiting resistors 72 and 102 with small resistance values, the main/backup dc power supply working branch is directly composed of contactors 6 and 9, the main/backup dc power supply de-pumping voltage branch is directly composed of thyristors 11 and 13, and the main/backup power supply negative working branch is directly composed of diodes 12 and 14. The main/standby direct-current power supply pre-charging branch, the working branch and the switching branch are positioned at the positive pole of the direct-current input side, and the pump-up voltage removing branch and the negative pole working branch are positioned at the negative pole of the direct-current input side. The anodes of the thyristors 71, 101, 11 and 13 are respectively connected with the anode 1 of the main direct-current power supply, the cathode 2 of the standby direct-current power supply, the cathode 3 of the main direct-current power supply and the cathode 4 of the standby direct-current power supply, and the cathodes of the diodes 12 and 14 are respectively connected with the cathode 3 of the main direct-current power supply and the cathode 4 of the standby direct-current power supply.
Specifically, the main/standby direct-current power supply voltages are U1 and U2, the values are basically equal, the resistance values of the pre-charging branch current limiting resistors 52 and 82 are R, and the resistance values are designed to be appropriately large, so that pre-charging peak currents U1/R and U2/R are smaller than the rated pulsating current of the electrolytic capacitor 15 on the direct-current input side. Therefore, the driving power required by the contactors 51 and 81 is small, and the auxiliary power supply of the control circuit can be directly used as the driving power supply.
Specifically, the main/standby power switching branch current limiting resistors 72, 102 have resistance values R1, R2 designed to be appropriately small. During operation of the power electronic converter, there are two cases of switching of the dc input power: when the main voltage drop rate is larger than a given value, the direct current power supply needs to be switched to standby, and when the standby direct current power supply detects that the main direct current power supply recovers to normal for a period of time during power supply, the direct current power supply needs to be switched to main. Under two conditions, when the main voltage U10 and the standby voltage U20 are switched, the voltage difference value is larger, the voltage difference value is U10-U20, generally dozens of volts, the peak current caused by the standby switching branch is (U10-U20)/R2, the upper limit of the current is set to be less than 3 times of the rated pulse current of the electrolytic capacitor and about 100A, and then the value of the resistance value R2 can be obtained; the difference between the main voltage U11 and the standby voltage U21 is small, generally several volts and tens of volts, the peak current caused by the main switching branch is (U11-U21)/R1, the upper limit of the current is set to 100A, and then the value of the resistance value R1 can be obtained. In addition, the current limiting resistors R1 and R2 should be resistors with larger power.
Specifically, the contactors 6 and 9 of the working branch of the main/standby power supply have large working current, and the contactors 6 and 9 have large driving power, so that the output voltage of the working branch of the main/standby power supply needs to be used as a driving power supply after the power electronic converter works. In addition, since the conduction loss of the contactors 6 and 9 is small, the conduction voltage drop is small, and the voltage across the switching branch thyristors 71 and 101 driven by the narrow pulses can be made substantially 0. Therefore, when the working branch is conducted, the thyristor of the switching branch kept conducted by the latch effect is automatically turned off.
Specifically, diodes 12 and 14 of the negative branch of the main/standby power supply point to the negative electrode from the positive electrode of the power supply, so that the direct current positive electrode and the direct current negative electrode are prevented from being connected reversely, and the electrolytic capacitor is prevented from being damaged.
The invention also provides an automatic switching method of two paths of direct current input power supplies of the power electronic converter, which comprises the following specific working procedures:
(1) before the power electronic converter is started to work, judging whether a main power supply and a standby power supply are normal, and if the main/standby direct current power supplies are normal or only the main direct current power supply is normal, supplying power by the main direct current power supply; if the main power supply abnormally supplies power and the standby power supply normally supplies power, the standby direct-current power supply supplies power. When the main/standby direct current power supply needs to supply power, the main (or standby) pre-charging branch contactor 51 (or 81) is conducted to pre-charge the electrolytic capacitor 15 at the direct current input side of the power electronic converter.
(2) When the power electronic converter is started to work, at the moment, according to the main/standby power supply condition, the main (or standby) switching branch thyristor 71 (or 101) is led to be conducted and the pre-charging branch contactor 51 (or 81) is cut off at the same time, after a certain time, the main (or standby) working branch contactor 6 (or 9) is conducted, and when the working branch is conducted, the voltage at two ends of the thyristor 71 (or 101) is 0, so that the main (or standby) switching branch is cut off at the same time. The power electronic converter then operates normally.
(3) When the power electronic converter with the motor load decelerates or suddenly stops, the electrolytic capacitor 15 generates pumping voltage, the pumping voltage is larger than the power supply direct current power supply voltage, the thyristor 11 (or 13) of the voltage pumping branch circuit is conducted according to the main/standby power supply condition, and therefore the pumping voltage is released through the voltage pumping branch circuit 11 (or 13) and the working branch circuit 6 (or 9).
(4) In the operation of the power electronic converter, under the condition that the standby direct-current power supply is normal, when the main direct-current power supply supplies power and the main direct-current power supply suddenly loses power (the voltage drop rate is greater than a given value), the main direct-current power supply needs to be switched to the standby direct-current power supply to supply power, the standby switching branch thyristor 101 is switched on in a pilot mode, the standby working branch contactor 9 is switched on after a certain time, the voltage at two ends of the thyristor 101 is 0 while the working branch is switched on, and therefore the standby switching branch 10 is automatically switched off at the same time, and finally the main working branch contactor 6 is switched off; when the standby direct-current power supply supplies power and detects that the main direct-current power supply is recovered to be normal for a period of time, the standby direct-current power supply of the power electronic converter needs to be switched to the main direct-current power supply, the main switching branch thyristor 71 is switched on in a pilot mode, the main working branch 6 is switched on after a certain period of time, and when the working branch is switched on, the voltage at two ends of the thyristor 71 is 0, so that the main switching branch 7 is automatically switched off at the same time, and finally the standby working branch contactor 9 is switched off.
The invention realizes the pre-charging of the electrolytic capacitor at the direct current input side of the power electronic converter, the power supply of the main/standby direct current power supply, the quick switching of the main/standby direct current power supply and the removal of the pumped voltage of the electrolytic capacitor, and has reliable principle and convenient realization.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. An automatic switching circuit of two-way direct current input power of a power electronic converter is characterized by comprising: two power supply modules, a power electronic converter DC input side electrolytic capacitor;
wherein the power module includes: the system comprises a positive and negative connecting end of a direct current power supply, a pre-charging branch, a working branch, a switching branch, a de-pumping voltage branch and a negative working branch; the two power supply modules are mutually used as a master and a standby;
the pre-charging branch, the working branch and the switching branch are connected in parallel and are positioned between the positive electrode of the direct-current power supply and the positive electrode of the electrolytic capacitor; the de-pumping voltage branch is connected with the negative working branch in parallel and is positioned between the negative electrode of the direct current power supply and the negative electrode of the electrolytic capacitor;
the pre-charging branch is composed of a first contactor and a first current-limiting resistor; the working branch is composed of a second contactor; the switching branch is composed of a first thyristor and a second current-limiting resistor; the de-pumping voltage branch is composed of a second thyristor; the negative working branch is composed of diodes;
when the main direct-current power supply is switched to the standby direct-current power supply, the standby switching branch is switched on in a leading mode, the standby working branch is switched on after the first time, the standby switching branch is switched off at the same time, and finally the main working branch is switched off;
when the standby direct-current power supply is switched to the main direct-current power supply, the pilot leads to the main switching branch, and after the second time, the main working branch is switched on, the main switching branch is cut off, and finally the standby working branch is cut off.
2. The automatic switching circuit according to claim 1, wherein the resistance of the first current limiting resistor is selected to ensure that the electrolytic capacitor is not energized for the first time before the power electronic converter operates, and the resistance of the second current limiting resistor is selected to ensure that the current does not exceed an allowable upper limit during switching.
3. The automatic switching circuit according to claim 1, wherein in the switching branch, one end of the second current limiting resistor is connected to the cathode of the first thyristor, and the other end of the second current limiting resistor is connected to the anode of the electrolytic capacitor; or one end of the second current-limiting resistor is connected with the positive electrode of the direct-current power supply, and the other end of the second current-limiting resistor is connected with the anode of the first thyristor.
4. The automatic switching circuit of claim 1 wherein said de-pumped voltage branch has said second thyristor anode connected to said dc power supply cathode and said electrolytic capacitor cathode.
5. The automatic switching circuit of claim 1 wherein said negative working branch has said diode cathode connected to said dc power supply cathode and said electrolytic capacitor cathode connected to said anode.
6. A method for automatically switching two-way direct current input power supplies of a power electronic converter, which is characterized by adopting the automatic switching circuit of any one of claims 1 to 5, and the method comprises the following steps:
before the power electronic converter is started to work, when a main direct current power supply is normal, a pilot leads to a main pre-charging branch circuit to pre-charge an electrolytic capacitor at the direct current input side of the power electronic converter;
when the power electronic converter is started to work, the main switching branch is conducted and the main pre-charging branch is cut off, and after a first preset time, the main working branch is conducted and the main switching branch is cut off at the same time;
in the working process of the power electronic converter, under the condition that the standby direct-current power supply is normal, when the main direct-current power supply is suddenly powered off, the standby switching branch is switched on in a pilot mode, after the second preset time, the standby working branch is switched on, the standby switching branch is switched off at the same time, and finally the main working branch is switched off; when the condition that the main direct-current power supply is recovered to be normal is detected to reach a third preset time, the pilot switches on the main switching branch, after the fourth preset time, the main working branch is switched on, the main switching branch is switched off, and finally the standby working branch is switched off;
when the motor load carried by the power electronic converter decelerates or suddenly stops, the pumping voltage is released by conducting the corresponding pump-up voltage removing branch and the working branch.
7. A method for automatically switching two-way direct current input power supplies of a power electronic converter, which is characterized by adopting the automatic switching circuit of any one of claims 1 to 5, and the method comprises the following steps:
before the power electronic converter is started to work, when a main direct-current power supply is abnormal and a standby direct-current power supply is normal, a standby pre-charging branch is switched on in a pilot mode to pre-charge an electrolytic capacitor at the direct-current input side of the power electronic converter;
when the power electronic converter is started to work, the standby switching branch is conducted and the standby pre-charging branch is cut off, and after a fifth preset time, the standby working branch is conducted and the standby switching branch is cut off at the same time;
in the working process of the power electronic converter, when the situation that the restoration of the main direct-current power supply is normal and reaches the sixth preset time is detected, the pilot switches on the main switching branch, after the seventh preset time, the main working branch is switched on, the main switching branch is switched off at the same time, and finally the standby working branch is switched off;
when the motor load carried by the power electronic converter decelerates or suddenly stops, the pumping voltage is released by conducting the corresponding pump-up voltage removing branch and the working branch.
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