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WO2017125769A1 - System for dc link precharging in active front end frequency converters - Google Patents

System for dc link precharging in active front end frequency converters Download PDF

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Publication number
WO2017125769A1
WO2017125769A1 PCT/HR2016/000002 HR2016000002W WO2017125769A1 WO 2017125769 A1 WO2017125769 A1 WO 2017125769A1 HR 2016000002 W HR2016000002 W HR 2016000002W WO 2017125769 A1 WO2017125769 A1 WO 2017125769A1
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WIPO (PCT)
Prior art keywords
link
frequency converter
end frequency
active
precharging
Prior art date
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Ceased
Application number
PCT/HR2016/000002
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French (fr)
Inventor
Bozo TERZIĆ
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Split Faculty Of Electrical Engineering Mechanical Engineering And Naval Arichitecture, University of
Original Assignee
Split Faculty Of Electrical Engineering Mechanical Engineering And Naval Arichitecture, University of
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Priority to PCT/HR2016/000002 priority Critical patent/WO2017125769A1/en
Publication of WO2017125769A1 publication Critical patent/WO2017125769A1/en
Anticipated expiration legal-status Critical
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Classifications

    • 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
    • H02M1/36—Means for starting or stopping converters
    • 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

Definitions

  • the present invention relates generally to power electronic converters, especially to Active Front End frequency converters (AFE converter) which are used in many industry applications. More specifically the present invention relates to a method of precharging DC link in AFE converter in order to limit charging current slope and avoid grid voltage drop caused by inrush current.
  • AFE converter Active Front End frequency converters
  • AFE frequency converter typically includes a rectifier or converter, a DC link, and an inverter.
  • the DC link voltage When electric power is applied to the AFE converter, the voltage across the DC link capacitors, referred to as the DC link voltage, rises from zero to a rated value, typically around 600 to 650 V for low voltage AC grid of 400 V. If this rise of the DC link voltage were left to occur naturally, it would happen very quickly by drawing very large electric currents from the input power lines, through the rectifier, and into the DC link capacitors. This large current, referred to as an inrush current, can be damaging to the components of the AFE converter and causes electrical grid voltage drop. Thus, to avoid damage to the AFE converter components and electrical grid voltage drop, the rise of the DC link voltage from 0 V to the rated voltage has to be accomplished in some controlled manner. This controlled raising of the DC link voltage is referred to as a DC link precharge operation.
  • the present innovation solves the problem of limiting inrush current in DC link precharge operation implementing secondary controllable active rectifying elements connected in series with DC link capacitors, that uses pulse charging in order to minimize inrush current and prevent voltage drop, where secondary controllable active rectifying elements are controlled in such manner to have both DC link capacitor bank ends disconnected during non-charging period of precharging operation.
  • a precharge contactor is used to connect precharge resistors between the input power line and the rectifier or, sometimes, between the input power line and the DC link. These precharge resistors limit the inrush current to a manageable level.
  • the precharge resistors are excluded from the circuit by opening the precharge contactor, and the input power line is connected directly to the rectifier by closing another contactor, referred to as the supply contactor.
  • the supply contactor remains closed during the operation of the system.
  • This method is well suited for frequency converters in which the rectifier is a simple diode rectifier, which offers no means for controlling the inrush current.
  • the main disadvantage of this method is in the cost and size of its components, in particular of the supply contactor, which can negatively impact the cost and size of the entire frequency converter.
  • main rectifier itself is used to accomplish precharge.
  • the rectifier in this case has at least one SCR in each phase.
  • SCRs are power semiconductors whose current conduction can be electronically controlled.
  • the conduction of the rectifier's SCRs is controlled so as to let only small pulses of inrush current flow during precharge.
  • the rectifier's SCRs are controlled to conduct at all times, i.e., the rectifier after the precharge acts as if it were a diode rectifier.
  • diode rectifier with serial resistance as secondary rectifier is connected in parallel to the main rectifier module of the VSD.
  • the inrush current is limited by resistors, that are also main disadvantage of this solution since current is by secondary rectifier is drawn throughout precharge and regular operation therefore causing energy losses due to resistor dissipation.
  • the fourth method (IV) refers to VSD with IGBT main rectifier where inrush current is controllable by additional IGBT transistor that is placed as replacement of existing IGBT antiparallel diode or as separate IGBT connected in series with the main rectifier.
  • IGBT antiparallel diode acts as rectifier, while additional IGBT transistor regulates pulses of inrush current flow, therefor limiting the current intake.
  • the present innovation as methods (III) and (IV) also uses active switching solution for precharging, but operates with line to line voltage and acts as low power secondary DC-link charging circuity.
  • the present invention solves the problem of precharging DC link in frequency converter applications, lowering the voltage drop (glitch) on grid impedance using power switching elements connected in series with DC link capacitors, and controlled in such manner to have both capacitor bank ends disconnected during non-charging period of precharging operation.
  • the DC link (200) consists of capacitors (202) and resistors (204) which filter the DC power and store energy from the DC bus.
  • the DC link has positive and negative pole, where we are in series to DC link connecting first controllable active rectifying element between first power line and DC link positive pole, and second controllable active rectifying element between DC link positive pole and second power line.
  • the controllable active rectifying elements are controlled in such manner to operate pulse charging of DC link capacitors, while in non-charging period of pre-charge operation both DC link poles are electrically disconnected from line to line voltage.
  • This construction allows quick charging of DC link capacitors while sustaining control of charging current in AFE frequency converters.
  • the present innovation is usable in non-floating applications like in AFE frequency converters with RFI filter that has electrical ground connectivity.
  • pre-charging circuitry choke can be added in series with DC link capacitor in order to limit the maximum value and slope of charging current pulses.
  • Figure 1 shows the block structure of general system configuration of the present invention.
  • Figure 2A shows a circuit diagram of DC link precharging circuit having two controllable active rectifying elements and DC link circuitry.
  • Figure 2B shows a circuit diagram of DC link precharging circuit having one controllable active rectifying element and DC link circuitry.
  • FIG. 3 shows a circuit diagram of the AFE converter in which the present invention embodied in DC link precharging circuit is implemented.
  • FIG. 1 illustrates generally system configuration of the present invention.
  • An AC power source (10) is connected via circuit breaker (3) to frequency converter (600) which supplies motor (500) in variable speed drive application or generator (500) in some renewable energy sources (wind power systems, cogeneration plants).
  • An AC power source (10) is low voltage three phase AC power grid with line voltages up to 690 V and line frequency of 50 Hz or 60 Hz.
  • the frequency converter (600) receives/gives AC power with a particular line voltage and fixed line frequency from/to AC power source (10) and provides AC power to the motor or generator (500) at a desired voltage and desired frequency, both of which can be variable.
  • the motor and generator (500) can be of different types (induction, synchronous, permanent magnet), but with capable of being operated at variable speeds.
  • the frequency converter (600) have three basic stages: Active front end (AFE) converter (100), DC link (200) and inverter (400).
  • AFE converter (100) converts the fixed line voltage and fixed line frequency from the AC power source (10) into DC power.
  • the DC link (200) filters the DC power and provides energy storage by means of capacitors.
  • the inverter (400) converts the DC power from DC link (200) into variable frequency and variable voltage AC power for the motor and generator (500).
  • the RFI filter (70) is placed between AFE converter (100) and contactor (50). It reduces high frequency interference emitted by frequency converter (600) to AC power sources (10). RFI filter is grounded.
  • DC link precharging circuit (300) Input of DC link precharging circuit (300) is connected to two phases (line to line) of the AC power source (10), and DC link (200) positive and negative pole is connected to DC link precharging circuit.
  • DC link precharging circuit is used to gradually charge capacitors in the DC link (200) and to limit charging current which could damage DC link capacitors.
  • FIG. 3 shows entire circuit diagram for AFE converter (100), DC link (200), DC link precharging circuit (300), RFI filter (70) and contactor (50).
  • the AFE converter (100) consists of LCL filter (110) and PWM rectifier (120).
  • the PWM rectifier (120) includes six power switches consisting of IGBT (122, 124) and antiparallel connected diode (121 , 123).
  • the PWM rectifier (120) also includes the corresponding control system (not shown for simplicity) to control the switching of the power switches in order to get the desired output voltages of DC link (200).
  • PWM rectifier (120) with LCL filter (1 10) operates as a boost rectifier to obtain output DC voltage of DC link (200) which is greater than maximum value of the input line to line voltage.
  • the LCL filter (110) provides almost pure sinusoidal current from AC power source (10) with THDi ⁇ 5%.
  • RFI filter (70) The components of RFI filter (70) are capacitors, chokes and resistors. There are various configurations of RFI filter, and their task is to reduce high frequency interference emitted by frequency converter on the way to carry out them into the ground.
  • the DC link (200) consists of capacitors (202) and resistors (204) which filter the DC power and store energy from the DC bus.
  • the resistors (204) have function to maintain a substantially equal DC link voltage between capacitors (202). Also, the resistors (204) have the function of discharging capacitors (202) when the frequency converter (600) is disconnected from the AC power source (10).
  • the DC link precharging circuit (300) in first embodiment consists of two controllable active rectifying elements (301 , 302), choke (303) and two fuses (305), where controllable active rectifying elements can be thyristors or IGBT transistors.
  • cathode of first thyristor (301) is connected to the positive pole of the DC link (200), while second thyristor (302) is connected to the negative pole of the DC link (200).
  • thyristors provide that both thyristors (301, 302) can conduct precharcing current at the same time during only positive halfperiod of the line to line voltage (UL1 -UL2), while during the negative half period both thyristors are reverse biased and blocked.
  • Thyristors (301) and (302) are controlled changing the firing angle in each positive half period to permit only small charging current impulses during precharging operation.
  • the choke (303) is used to limit the maximum value and slope of charging current pulses. Too high slope of charging current pulses can cause the high voltage drops (glitches) on the grid impedance.
  • the same current impulse charging and control as described can be achieved by replacing thyristors with IGBT transistors, where we can achieve even faster pre-charging by switching IGBT transistors on and off at higher frequency than in case when thyristors are used as controllable active rectifying elements that are fired once in every other input voltage half- period.
  • Frequency converters with AFE converter on grid side are used in many industry applications such as regenerative electric drives, variable speed wind turbine, solar power plants, etc. In such application, according to technical standards, it is mandatory to have RFI filter installation. Taking into account the main advantages of the present invention, fast DC link charging without losses, without electromechanical components and with impulse charging current in limited amount and slope, the invention is widely applicable in frequency converter technique, especially in cases where application often requires switching on and off during regular operation as i.e. in the crane drives with remote control.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)

Abstract

The present invention solves the problem of in rush current during precharging operation in Active front end frequency converters by using controlled power switching elements (301) connected to line to line voltage and in series with DC link capacitor bank (200), where controlled power switching elements (301) are controlled in such manner to have both DC link capacitor bank ends (P+, P-) disconnected during non-charging period of precharging operation. The solution uses pulse charging method to limit charge current, and in addition it withholds the charging current slope in the reasonable in floating and non-floating installations of frequency converter i.e. grounded RFI filter (70) installed after the main contactor (50).

Description

SYSTEM FOR DC LINK PRECHARGING IN ACTIVE FRONT END
FREQUENCY CONVERTERS
DESCRIPTION
Technical Field
The present invention relates generally to power electronic converters, especially to Active Front End frequency converters (AFE converter) which are used in many industry applications. More specifically the present invention relates to a method of precharging DC link in AFE converter in order to limit charging current slope and avoid grid voltage drop caused by inrush current.
Technical Problem
AFE frequency converter typically includes a rectifier or converter, a DC link, and an inverter. When electric power is applied to the AFE converter, the voltage across the DC link capacitors, referred to as the DC link voltage, rises from zero to a rated value, typically around 600 to 650 V for low voltage AC grid of 400 V. If this rise of the DC link voltage were left to occur naturally, it would happen very quickly by drawing very large electric currents from the input power lines, through the rectifier, and into the DC link capacitors. This large current, referred to as an inrush current, can be damaging to the components of the AFE converter and causes electrical grid voltage drop. Thus, to avoid damage to the AFE converter components and electrical grid voltage drop, the rise of the DC link voltage from 0 V to the rated voltage has to be accomplished in some controlled manner. This controlled raising of the DC link voltage is referred to as a DC link precharge operation.
The present innovation solves the problem of limiting inrush current in DC link precharge operation implementing secondary controllable active rectifying elements connected in series with DC link capacitors, that uses pulse charging in order to minimize inrush current and prevent voltage drop, where secondary controllable active rectifying elements are controlled in such manner to have both DC link capacitor bank ends disconnected during non-charging period of precharging operation.
Previous State of Art
The general information regarding state of the art can be found in: o Sinamics low voltage engineering manual, Siemens AG 2008.
o System for precharging DC link in a variable speed drive, patent application
PCT/US2006/004563, York international corporation
o AC Precharge-circuit, patent application PCT/US2013/01 19903 , Rockwell Automation
Technologies
In practice use in AFE frequency converter, inrush current problem is solved by applying next technical methods:
(I) Introducing bypass switching system that limits inrush current by connecting precharge resistors between input power line and the rectifier
(II) Charging DC link over rectifier consisting (at least partially) of thyristors, also called silicon controlled rectifiers, or SCRs.
(III) Integrating secondary diode rectifier brigde with precharge resistors in parallel to the main rectifier module of the VSD
(IV) Using IGBT transistors or thyristors as antiparallel diodes in standard IGBT inverter for precharging DC-link as described in patent application PCT/US2006/004563
In the first method (I.), a precharge contactor is used to connect precharge resistors between the input power line and the rectifier or, sometimes, between the input power line and the DC link. These precharge resistors limit the inrush current to a manageable level. After the precharge is completed, the precharge resistors are excluded from the circuit by opening the precharge contactor, and the input power line is connected directly to the rectifier by closing another contactor, referred to as the supply contactor. The supply contactor remains closed during the operation of the system. This method is well suited for frequency converters in which the rectifier is a simple diode rectifier, which offers no means for controlling the inrush current. The main disadvantage of this method is in the cost and size of its components, in particular of the supply contactor, which can negatively impact the cost and size of the entire frequency converter.
In the second method (II) main rectifier itself is used to accomplish precharge. The rectifier in this case has at least one SCR in each phase. SCRs are power semiconductors whose current conduction can be electronically controlled. The conduction of the rectifier's SCRs is controlled so as to let only small pulses of inrush current flow during precharge. After the precharge is completed, the rectifier's SCRs are controlled to conduct at all times, i.e., the rectifier after the precharge acts as if it were a diode rectifier.
In the third method (III), diode rectifier with serial resistance as secondary rectifier is connected in parallel to the main rectifier module of the VSD. The inrush current is limited by resistors, that are also main disadvantage of this solution since current is by secondary rectifier is drawn throughout precharge and regular operation therefore causing energy losses due to resistor dissipation.
The fourth method (IV) refers to VSD with IGBT main rectifier where inrush current is controllable by additional IGBT transistor that is placed as replacement of existing IGBT antiparallel diode or as separate IGBT connected in series with the main rectifier. In this method, during pre-charge operation, IGBT antiparallel diode acts as rectifier, while additional IGBT transistor regulates pulses of inrush current flow, therefor limiting the current intake.
While methods (I) and (II) have durability and energy consumption issues due to the usage of resistors for current limitation, methods (III) and (IV) incorporates active switching solutions that operates rather well in the terms of energy consumption and usability.
The present innovation as methods (III) and (IV) also uses active switching solution for precharging, but operates with line to line voltage and acts as low power secondary DC-link charging circuity.
Summary of invention
The present invention solves the problem of precharging DC link in frequency converter applications, lowering the voltage drop (glitch) on grid impedance using power switching elements connected in series with DC link capacitors, and controlled in such manner to have both capacitor bank ends disconnected during non-charging period of precharging operation.
The DC link (200) consists of capacitors (202) and resistors (204) which filter the DC power and store energy from the DC bus. The DC link has positive and negative pole, where we are in series to DC link connecting first controllable active rectifying element between first power line and DC link positive pole, and second controllable active rectifying element between DC link positive pole and second power line.
The controllable active rectifying elements are controlled in such manner to operate pulse charging of DC link capacitors, while in non-charging period of pre-charge operation both DC link poles are electrically disconnected from line to line voltage.
This construction allows quick charging of DC link capacitors while sustaining control of charging current in AFE frequency converters.
Since we have both DC link poles are electrically disconnected from line to line voltage during non-charging period of pre-charge operation, the present innovation is usable in non-floating applications like in AFE frequency converters with RFI filter that has electrical ground connectivity.
In addition, as part of pre-charging circuitry choke can be added in series with DC link capacitor in order to limit the maximum value and slope of charging current pulses.
Brief Description of the Drawings
Figure 1 shows the block structure of general system configuration of the present invention.
Figure 2A shows a circuit diagram of DC link precharging circuit having two controllable active rectifying elements and DC link circuitry.
Figure 2B shows a circuit diagram of DC link precharging circuit having one controllable active rectifying element and DC link circuitry.
Figure 3 shows a circuit diagram of the AFE converter in which the present invention embodied in DC link precharging circuit is implemented. Detailed Description
Figure 1 illustrates generally system configuration of the present invention. An AC power source (10) is connected via circuit breaker (3) to frequency converter (600) which supplies motor (500) in variable speed drive application or generator (500) in some renewable energy sources (wind power systems, cogeneration plants). An AC power source (10) is low voltage three phase AC power grid with line voltages up to 690 V and line frequency of 50 Hz or 60 Hz.
The frequency converter (600) receives/gives AC power with a particular line voltage and fixed line frequency from/to AC power source (10) and provides AC power to the motor or generator (500) at a desired voltage and desired frequency, both of which can be variable. The motor and generator (500) can be of different types (induction, synchronous, permanent magnet), but with capable of being operated at variable speeds.
The frequency converter (600) have three basic stages: Active front end (AFE) converter (100), DC link (200) and inverter (400). The AFE converter (100) converts the fixed line voltage and fixed line frequency from the AC power source (10) into DC power. The DC link (200) filters the DC power and provides energy storage by means of capacitors. Finally, the inverter (400) converts the DC power from DC link (200) into variable frequency and variable voltage AC power for the motor and generator (500).
The RFI filter (70) is placed between AFE converter (100) and contactor (50). It reduces high frequency interference emitted by frequency converter (600) to AC power sources (10). RFI filter is grounded.
Input of DC link precharging circuit (300) is connected to two phases (line to line) of the AC power source (10), and DC link (200) positive and negative pole is connected to DC link precharging circuit. DC link precharging circuit is used to gradually charge capacitors in the DC link (200) and to limit charging current which could damage DC link capacitors.
When DC link charging process is finished, DC link voltage is equal to approximately value of maximum line voltage of AC power source (10) and the contactor (50) connects the AFE converter (100) via the RFI filter (70) to the AC power source (10). Figures 3 shows entire circuit diagram for AFE converter (100), DC link (200), DC link precharging circuit (300), RFI filter (70) and contactor (50).
The AFE converter (100) consists of LCL filter (110) and PWM rectifier (120). The PWM rectifier (120) includes six power switches consisting of IGBT (122, 124) and antiparallel connected diode (121 , 123). The PWM rectifier (120) also includes the corresponding control system (not shown for simplicity) to control the switching of the power switches in order to get the desired output voltages of DC link (200). PWM rectifier (120) with LCL filter (1 10) operates as a boost rectifier to obtain output DC voltage of DC link (200) which is greater than maximum value of the input line to line voltage. Also, the LCL filter (110) provides almost pure sinusoidal current from AC power source (10) with THDi < 5%.
The components of RFI filter (70) are capacitors, chokes and resistors. There are various configurations of RFI filter, and their task is to reduce high frequency interference emitted by frequency converter on the way to carry out them into the ground.
The DC link (200) consists of capacitors (202) and resistors (204) which filter the DC power and store energy from the DC bus. The resistors (204) have function to maintain a substantially equal DC link voltage between capacitors (202). Also, the resistors (204) have the function of discharging capacitors (202) when the frequency converter (600) is disconnected from the AC power source (10).
The DC link precharging circuit (300) in first embodiment consists of two controllable active rectifying elements (301 , 302), choke (303) and two fuses (305), where controllable active rectifying elements can be thyristors or IGBT transistors.
For thyristor used as controllable active rectifying elements, cathode of first thyristor (301) is connected to the positive pole of the DC link (200), while second thyristor (302) is connected to the negative pole of the DC link (200).
This configuration of thyristors provide that both thyristors (301, 302) can conduct precharcing current at the same time during only positive halfperiod of the line to line voltage (UL1 -UL2), while during the negative half period both thyristors are reverse biased and blocked. Thyristors (301) and (302) are controlled changing the firing angle in each positive half period to permit only small charging current impulses during precharging operation. The choke (303) is used to limit the maximum value and slope of charging current pulses. Too high slope of charging current pulses can cause the high voltage drops (glitches) on the grid impedance.
The same current impulse charging and control as described can be achieved by replacing thyristors with IGBT transistors, where we can achieve even faster pre-charging by switching IGBT transistors on and off at higher frequency than in case when thyristors are used as controllable active rectifying elements that are fired once in every other input voltage half- period.
Also the same effect of impulse precharging can be achieved with only one controllable active rectifying element installed, as shown in Figure 2B, where second controllable active rectifying element (302) is replaced with rectifying diode (304). (Figure 2B).
Industrial Applicability
Frequency converters with AFE converter on grid side are used in many industry applications such as regenerative electric drives, variable speed wind turbine, solar power plants, etc. In such application, according to technical standards, it is mandatory to have RFI filter installation. Taking into account the main advantages of the present invention, fast DC link charging without losses, without electromechanical components and with impulse charging current in limited amount and slope, the invention is widely applicable in frequency converter technique, especially in cases where application often requires switching on and off during regular operation as i.e. in the crane drives with remote control.
Abbreviations
AC Alternating current
DC Direct current
RFI Radio frequency interference
AFE Active front end
IGBT Insulated gate bipolar transistor References
10 AC power source
30 Circuit breaker
50 Contactor
70 RFI filter
100 AFE converter
1 10 LCL filter
121 Antiparallel diode
122 IGBT transistor
200 DC link
202 DC link capacitor
204 DC link resistor
300 DC link precharging circuit
301 First controllable active switching element
302 Second controllable active switching element
303 Choke
304 Diode rectifier
305 Electrical fuse
400 Inverter
500 Motor
LI AC voltage first phase
L2 AC voltage second phase
P+ Positive pole of DC link capacitor bank
P- Negative pole of DC link capacitor bank

Claims

1. Active front end frequency converter that for DC link precharging uses secondary controllable active rectifying elements connected to line to line voltage in series with DC link capacitors, and controlled in such manner to have both capacitor bank ends electrically disconnected from line to line voltage during non-charging period of precharging operation
2. Active front end frequency converter of claim 1 wherein controllable active
rectifying elements are two thyristors or two isolated gate bipolar transistors
3. Active front end frequency converter of claim 1 wherein controllable active
rectifying elements are combination of thyristor and isolated gate bipolar transistor
4. Active front end frequency converter of claim 1 that have only one controllable active rectifying element on one side of capacitor bank and diode rectifier on another
5. Active front end frequency converter of claim 1 that includes choke (303)
connected in series with controllable active rectifying element that is used to limit maximum and slope of charging current impulse.
6. Control algorithm of Active front end frequency converter in embodiment of
claim 2 that uses same firing angle for thyristors or symoultaniously fires both controllable active rectifying elements in order to achive near linear DC link voltage rise
PCT/HR2016/000002 2016-01-18 2016-01-18 System for dc link precharging in active front end frequency converters Ceased WO2017125769A1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112217383A (en) * 2019-07-12 2021-01-12 伟肯有限公司 DC-link charging device and method for charging a DC-link capacitor
CN112840550A (en) * 2019-07-16 2021-05-25 东芝三菱电机产业系统株式会社 power conversion system
IT202200007097A1 (en) * 2022-04-11 2023-10-11 Imer Int S P A Device that can be used for the input stage of electronic equipment
EP3910771B1 (en) * 2020-05-14 2024-10-23 Rockwell Automation Technologies, Inc. Dc bus precharge system

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EP1363387A2 (en) * 2002-05-17 2003-11-19 Lenze Drive Systems GmbH Circuit arrangement for a DC link
EP1566880A2 (en) * 2004-02-18 2005-08-24 ABB Oy Method and arrangement for charging intermediate circuit of frequency converter
US20130119903A1 (en) 2011-11-14 2013-05-16 Rockwell Automation Technologies, Inc. Ac pre-charge circuit
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112217383A (en) * 2019-07-12 2021-01-12 伟肯有限公司 DC-link charging device and method for charging a DC-link capacitor
CN112217383B (en) * 2019-07-12 2024-11-15 伟肯有限公司 DC link charging device and method for charging a DC link capacitor
CN112840550A (en) * 2019-07-16 2021-05-25 东芝三菱电机产业系统株式会社 power conversion system
EP4002671A4 (en) * 2019-07-16 2023-01-18 Toshiba Mitsubishi-Electric Industrial Systems Corporation POWER CONVERTER SYSTEM
EP3910771B1 (en) * 2020-05-14 2024-10-23 Rockwell Automation Technologies, Inc. Dc bus precharge system
IT202200007097A1 (en) * 2022-04-11 2023-10-11 Imer Int S P A Device that can be used for the input stage of electronic equipment

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