EP3577754A1 - Battery charger for traction vehicle - Google Patents

Battery charger for traction vehicle

Info

Publication number
EP3577754A1
EP3577754A1 EP18707723.5A EP18707723A EP3577754A1 EP 3577754 A1 EP3577754 A1 EP 3577754A1 EP 18707723 A EP18707723 A EP 18707723A EP 3577754 A1 EP3577754 A1 EP 3577754A1
Authority
EP
European Patent Office
Prior art keywords
battery charger
conversion stage
voltage
converter
rectifier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP18707723.5A
Other languages
German (de)
French (fr)
Inventor
Hans-Rudolf Riniker
Gabriel Ortiz
Stefan Pfister
Yanick Lobsiger
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.)
ABB Schweiz AG
Original Assignee
ABB Schweiz AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ABB Schweiz AG filed Critical ABB Schweiz AG
Publication of EP3577754A1 publication Critical patent/EP3577754A1/en
Withdrawn legal-status Critical Current

Links

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
    • 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
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • 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
    • H02M3/01—Resonant DC/DC 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
    • 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
    • H02M3/33571—Half-bridge at primary side of an isolation transformer
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/0077—Plural converter units whose outputs are connected in series
    • 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
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4216—Arrangements for improving power factor of AC input operating from a three-phase input voltage
    • 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

Definitions

  • the invention relates to the field of the electric system of traction vehicles.
  • the invention relates to a battery charger for a traction vehicle.
  • Traction vehicles such as trains or trams, may comprise a rechargeable battery for compensating power failures of a supplying catenary network.
  • the electric system of the traction vehicle comprises a battery charger, which converts a supply current, for example provided by an auxiliary converter, into a charging voltage for the battery.
  • Current battery chargers are usually based on silicon MOSFET or IGBT semiconductor technology. The use of these types of power semiconductor devices may limit the reachable switching frequency and/or voltage level of the power electronic circuitry, resulting in comparatively large, heavy and lossy battery charger solutions.
  • US 2012 0 262 113 Al relates to a charging apparatus of a mobile vehicle, which is adapted to receive and convert an AC input source into a DC output source for charging a rechargeable battery of the mobile vehicle.
  • the charging apparatus includes an EMI filter, a power factor corrector, a DC/DC converter, and a voltage control unit.
  • US 2012 0 229 086 Al relates to a charging apparatus of a mobile vehicle which is adapted to receive and convert an external AC power source into a DC power source for charging a rechargeable battery of the mobile vehicle.
  • the charging apparatus includes an electromagnetic interference EMI filter and a power factor corrector.
  • US 2014/266044 Al relates to a battery charger for an electric vehicle, with an input filter, a first conversion stage with an active rectifier and a second conversion stage with an galvanically isolated DC-DC converter.
  • EP 1 276 218 A2 shows a power supply with a rectifier connected with a galvanically isolated DC-DC converter.
  • a primary side inverter of the DC-DC converter comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
  • a primary side inverter of a DC- DC converter which comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
  • US 2015/249395 Al shows a DC-DC conversion system, which has a first conversion stage with a buck-boost converter and a second conversion stage with a DC-DC converter having a primary side inverter, which comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
  • US 2002/064060 Al shows a further DC-DC conversion system with a voltage regulation stage in front of a DC-DC converter having a primary side inverter, which comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
  • US 2014/063860 Al describes a DC power source, which comprises a first stage with a boost converter made of three half-bridges and a second stage with a galvanically isolated DC-DC converter having a full bridge inverter as primary side inverter.
  • US 2008/112195 Al relates to a transformer circuit for a power supply, in which two rectifiers are connected to several secondary side windings of a transformer.
  • US 5461 297 A relates to a capacitor charging system with series or parallel connected rectifiers connected to secondary side windings of a transformer.
  • US 2016/294290 Al describes a power converter, which comprises a first stage with a boost converter and a second stage with a galvanically isolated DC-DC converter having a full bridge inverter as primary side inverter. MOSFETs and switches based on wide bad gap material are mentioned as switch elements. DESCRIPTION OF THE INVENTION
  • the invention relates to a battery charger for a traction vehicle.
  • the battery charger may be provided as a module, i.e. with all components assembled within one mechanical device.
  • the battery charger may be adapted for processing currents of more than 20 A.
  • at least one of the following nominal voltage and/or current ranges of batteries may be covered by the battery charger: 110 V / 75 A, 36 V / 225 A and 24 V / 337 A.
  • a traction vehicle may be any rail or track bound vehicle, such as a train or tram.
  • the traction vehicle may be fed from an AC network or DC network, for example via a catenary.
  • the battery charger comprises: a first conversion stage for receiving an input voltage and for converting the input voltage into an intermediate DC voltage, and a second conversion stage for converting the intermediate DC voltage into a DC charging voltage, wherein the first conversion stage comprises an active converter, and wherein the second conversion stage comprises a galvanically isolated resonant DC-DC converter with a primary side inverter connected via a transformer with at least one secondary side rectifier which also may be of the active rectified kind.
  • the active converter of the first conversion stage is a buck converter for generating the intermediate voltage, for example either from the input voltage or the rectified input voltage.
  • the buck converter may be controlled for power factor correction.
  • the buck converter may be connected to an rectifier via a DC link.
  • the buck converter is an interleaved buck converter, which comprises at least two half- bridges connected in parallel.
  • the midpoints of the half-bridges may be connected via an inductor with a first (such as positive) phase of the intermediate voltage and one (such as the lower) side of the half-bridges may be connected with a second (such as negative) phase of the intermediate voltage.
  • the buck converter and/or the first conversion stage may be not galvanically separated.
  • the battery charger comprises two stages of power conversion.
  • the first conversion stage may be an AC-DC conversion stage performing power factor correction or, in the case of a DC input voltage, a DC-DC conversion stage.
  • the first conversion stage may deliver an intermediate regulated voltage, which powers the second conversion stage.
  • the second conversion stage may comprise a galvanically isolated DC-DC converter. The output of this DC-DC converter may feed the rechargeable battery.
  • a converter with active rectification for the first conversion stage and a resonant converter for the second conversion stage may minimize losses.
  • a resonant converter, such as an LLC converter, for the second converter stage may have low losses due to topological reasons.
  • losses may be minimized by synchronous switching of the active rectifiers.
  • the DC-DC converter of the second conversion stage may be a series-resonant DC-DC converter, for example of the LLC type, which may be connected on its input to the intermediate voltage.
  • the DC-DC converter may provide an isolation between the input and the output of the battery charger with the aid of a transformer, which also may provide an inductor for the resonance tank of the DC-DC converter with its windings.
  • the DC-DC converter may provide a voltage and/or current adaptation between the output of the first conversion stage and the battery.
  • the primary side inverter of the second conversion stage comprises a half- bridge interconnected with its midpoint via an inductance with the transformer and a split capacitance connected in parallel with the half-bridge and connected with its midpoint with the transformer.
  • the split capacitance, the inductance and the windings of the transformer may provide the resonant tank of the DC-DC converter of the second conversion stage.
  • the secondary side rectifier of the second conversion stage is an active bridge rectifier of any type such as full- wave rectifier, voltage doubler rectifier, center-tap rectifier and alike.
  • the second conversion stage may comprise one or more rectifiers for providing the battery charging voltage.
  • these rectifiers may be connected in parallel and/or in series to adapt the output voltage and current.
  • These varying connection schemes of the multitude of rectifiers are enabled by the isolating nature of the transformer providing power individually to each of the rectifiers. Furthermore, by switching the rectifiers in a synchronous mode, i.e. synchronously with the generated voltage, losses may be minimized.
  • the second conversion stage of the battery charger may be combined with different types of a first conversion stage.
  • different types of input voltages may be supplied to the battery charger.
  • the battery charger may be linked to the traction system's internal 3- phase auxiliary grid, an internal DC link/source, or alternatively, provided that all overvoltage protection mechanisms are modified accordingly, directly to a DC input of the traction vehicle, in case of DC-powered vehicles.
  • the first conversion stage may comprise a passive rectifier in combination with a buck converter or a boost converter alone.
  • the first conversion stage may comprise the buck converter alone or the boost converter alone.
  • the first conversion stage comprises a rectifier for rectifying the input voltage, which may be a multi-phase AC voltage.
  • the rectifier may be a diode bridge rectifier with a half-bridge for each input phase.
  • the buck converter may be used for power factor correction of a multi-phase input power source, damping of a source network providing the input voltage that typically comprises an inverter with an undamped sine filter, and/or generation of a regulated intermediate voltage.
  • the input voltage is a DC voltage directly supplied to the buck converter.
  • the combination of rectifier and buck converter may be seen as a generic input stage with the possibility to be connected to a three-phase voltage or directly to the available DC voltage from the electric system of the traction vehicle.
  • the diode rectifier may be bypassed when a DC voltage is directly available.
  • the buck converter may be provided with semiconductor devices switched in synchronous mode replacing the typically used freewheeling diodes, thus achieving a reduction in conduction losses and bidirectional operation mode, needed for damping and/or optional reverse operation of the device in DC input voltage mode.
  • the output part of the battery charger and in particular of the second conversion stage may be based on galvanically isolated building blocks in the form of rectifiers together with respective windings of the transformer, which may be rearranged, for example to cover battery voltages from 110 V down to 24 V.
  • the second conversion stage comprises at least one transformer with at least two secondary windings and at least two rectifiers connected to the at least two secondary windings.
  • the at least two rectifiers may be galvanically isolated from each other.
  • the primary winding of the transformer may have a common core with the at least two secondary windings.
  • the second conversion stage comprises more than one transformer, i.e. more than one core. In such a way, wider power and voltage ranges may be reached by parallel, series, or combined parallel and series connection of units and/or rectifiers on a system level.
  • the second conversion stage may be based on a flexible transformer/rectifier configuration and/or may comprise multiple secondary windings and/or multiple transformers with multiple secondary windings each feeding a rectifier, while maintaining the rest of the battery charger's hardware unchanged.
  • All output rectifiers may be based on active semiconductors and/or may be operated in synchronous rectification mode.
  • At least one rectifier is connected to at least two secondary windings.
  • the secondary windings may be sub-grouped and/or parallel connected to feed one of the multiple rectifiers, which may provide a further level of flexibility in the output part of the second conversion stage.
  • currents of conductors connected to different primary windings of one or more transformers and/or conductors connected to different secondary windings of one or more transformers are equalized with a symmetrizing core surrounding the conductors.
  • Symmetrizing cores which may be ferrite rings surrounding two conductors, may be used for equalizing pairwise the currents of multiple primary and/or secondary transformer windings. This may ensure a more equally loading of two or more windings or transformers.
  • rectifiers of the second conversion stage are connected in series and/or in parallel for setting a specific charging voltage and/or current to adapt to a wide range of rechargeable batteries' voltage/current levels. It also may be that a first group of rectifiers connected in series is connected in parallel with a second group of rectifiers connected in series. Such a connection may be performed easily, when the rectifiers are galvanically isolated from each other.
  • the battery charger further comprises an electromagnetic interference (EMI) filter connected before the first conversion stage for filtering the input voltage.
  • EMI electromagnetic interference
  • the same EMI filter may be used for filtering a DC input voltage and an AC input voltage.
  • the EMI filter may reduce high frequency electromagnetic emissions to other neighbouring equipment and/or may reduce the susceptibility of the battery charger to external disturbances.
  • the battery charger further comprises a controller adapted for controlling the active converter of the first conversion stage for controlling the DC charging voltage and/or DC charging current via the intermediate voltage. It may be possible that the controller controls the first conversion stage based on the measurement signals, such that a requested battery charging voltage profile and/or charging current profile is attained.
  • the controller may be adapted for regulating the intermediate voltage for controlling the DC charging voltage and/or current.
  • the controller may be adapted for controlling the active converter of the first conversation stage such that a power factor correction of the input voltage is performed.
  • Both the first and second conversion stage may be controlled by one control unit providing the controller, which may regulate the intermediate voltage level in order to control the output voltage/current delivered to the rechargeable battery.
  • Using an integrated control unit allows for integration of functions, previously managed by several distributed dedicated units, into one component.
  • the controller may monitor not only electrical but also thermal quantities of the conversion stages. Electrical and thermal measurements may be available to the central control unit. Also the battery's charging state may be monitored by the controller.
  • the controller may generate and/or supply the gate signals of all converter semiconductors, i.e. for the buck converter or boost converter of the first conversion stage and/or for the DC-DC converter of the second conversion stage.
  • the controller may control the output battery charging voltage/current by controlling the converter's intermediate voltage level, i.e. by controlling the output voltage of the buck converter or boost converter.
  • the controller may control an input power factor correction and/or active damping by indirectly controlling the input current.
  • the controller may monitor relevant electrical and thermal quantities in order to perform said control task and to keep the converter within safe operating margins.
  • the controller may provide a programming interface and/or communication interfaces.
  • the battery charger may be more flexible and simple to implement in different and complex traction platforms.
  • the controller may provide communication with external interfaces for remote regulation and supervision of the battery charger and/or for load, current and/or voltage sharing among multiple interconnected battery chargers.
  • the active converter of the first conversion stage and/or the DC-DC converter of the second conversion stage are based on wide-bandgap semiconductor switches.
  • the wide-bandgap semiconductor switches may be of MOSFET type based on silicon carbide and/or of HEMT (high-electron-mobility transistor) type based on gallium nitride.
  • MOSFETs based on silicon carbide and/or gallium nitride.
  • one or both of these conversion stages may incorporate wide-bandgap semiconductor technology such as silicon carbide and/or gallium nitride.
  • wide-bandgap semiconductor technologies such as silicon carbide
  • soft switching modulation schemes may allow to reduce converter losses and consequently increase its efficiency, given their comparatively low switching losses, which in turn enables an increase in switching frequency.
  • An increase in switching frequency furthermore may result in compact magnetic and capacitive components. Moreover, with lower switching losses, the size of the cooling system (such as heat sinks, fans, etc.) required for evacuating the semiconductors' losses may be reduced, thus achieving an overall increase in power density.
  • the cooling system such as heat sinks, fans, etc.
  • the battery charger may be based on printed circuit board assemblies, reducing the manufacturing, assembly, transport and commissioning costs of the battery charger.
  • the active converter of the first conversation stage is a boost converter, which, however, is not a part of the subject-matter as described by the claims.
  • the active converter of the first conversation stage may be a boost converter for generating the intermediate voltage from the input voltage.
  • the rectifier and the buck converter may be replaced with a 2-level two or more phase boost-type active and bidirectional converter.
  • the boost converter may be used for power factor correction of a multi-phase input power, damping of a source network providing the input voltage that typically comprises an inverter with an undamped sine filter, and/or generation of a regulated intermediate voltage.
  • the first conversion stage may comprise an active boost- type converter with sinusoidal input currents.
  • the boost converter may comprise at least two half-bridges, the half-bridge connected in parallel to provide the intermediate voltage.
  • the input voltage may be a multi-phase AC voltage and/or the boost converter may be used for maintaining a sinusoidal input voltage and/or for power factor correction.
  • the half-bridges may be connected with their midpoints via inductors to phases of the input voltage.
  • the input voltage may be a DC voltage and/or the boost converter may be used to generate the DC intermediate voltage from the DC input voltage.
  • the boost converter may be fed directly by the DC input voltage, in which case the power factor correction feature need not be utilized.
  • the half-bridges may be connected with their midpoints via inductors with a first (positive) phase of the DC input voltage and with one (lower) side with a second (negative) phase of the DC input voltage.
  • Fig. 1 schematically shows a battery charger according to an embodiment of the invention.
  • Fig. 2 schematically shows a battery charger according to a further embodiment of the invention.
  • Fig. 3 schematically shows a battery charger according to a further embodiment of the invention.
  • Fig. 4 schematically shows a battery charger according to a further embodiment of the invention.
  • Fig. 5 shows a circuit diagram for a first conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 6 shows a circuit diagram for a further embodiment of a first conversion stage.
  • Fig. 7 shows a circuit diagram for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 8A schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 8B shows a circuit diagram for a rectifier for the output part of Fig. 8A.
  • Fig. 9A schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 9B shows a circuit diagram for a rectifier for the output part of Fig. 9A.
  • Fig. 10 schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 11A, 1 IB, l lC schematically show output parts for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 12 schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 13 schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
  • Fig. 1 to 4 show a battery charger 10, which comprises an EMI filter 12, a first conversion stage 14 and a second conversion stage 16, which are cascade-connected between an input 18 of the battery charger 10 and its output 20. With the output, which provides a DC output voltage or charging voltage, a rechargeable battery 22 of a traction vehicle may be charged.
  • the battery charger 10 is supplied with an input voltage, which in the case of Fig. 1 and 3 is a three-phase AC voltage and in the case of Fig. 2 and 4 is a DC voltage.
  • the input voltage is filtered by the EMI filter 12 and supplied to the first conversion stage 14. In both cases of an AC input voltage or a DC input voltage, the same EMI filter 12 may be used. In the latter case, only two of the three phases of the EMI filter 12 may be used.
  • the first conversion stage converts the input voltage into a DC intermediate voltage, which is supplied into a DC link 24 between the first conversion stage 14 and the second conversion stage 16.
  • the second conversion stage converts the DC intermediate voltage into the DC output voltage.
  • the DC output voltage may be supplied to a further DC link 26. It has to be noted that here and in the following, every DC link may comprise a DC capacitor connected between the phases of the DC link.
  • the first conversion stage 14 comprises a three-phase rectifier 28 and a nonisolated DC-DC converter 30, which are connected via a DC link 32. Furthermore, for over voltage protection, a varistor 34 may connect the two phases of the DC link 32.
  • the rectifier 28 may be a passive rectifier and/or may be supplied with input power from a three-phase on-board AC supply.
  • the DC-DC converter 30, which may be a buck converter, may convert the voltage of the DC link 32 into the intermediate voltage. Since the DC-DC converter 30 is controllable, a power factor correction of the input voltage/input power, at least to some degree, and a control of the intermediate voltage may be performed by the DC-DC converter 30.
  • the rectifier 28 may be bypassed and the input voltage may be supplied directly to the DC link 32.
  • a power factor correction is not necessary and the DC-DC converter 30 only may perform a control of the intermediate voltage in the DC link 24.
  • a buck converter 30 may be used as active converter
  • the converter 36 may be or may comprise a boost converter or a buck converter.
  • a three-phase AC input voltage for example from a three-phase on-board AC supply, is directly converted into the intermediate voltage by the boost or buck converter 36.
  • the power factor correction of the input voltage/input power and a control of the intermediate voltage may be performed by converter 36.
  • a DC input voltage for example directly from a DC supply network of the traction vehicle, is directly converted into the intermediate voltage by the buck or boost converter 36.
  • a power factor correction may be not necessary and the converter 36 only may perform a control of the intermediate voltage in the DC link 24.
  • a varistor 34 may connect the two phases of the DC link 24.
  • the converter 36 may be a three-phase bridge converter, which input phases in the case of Fig. 3 are connected to the different phases provided by the EMI filter 12, while in Fig. 4, the input phases of the converter 36 may be star-connected to one phase of the input voltage provided by the EMI filter 12.
  • the second isolated conversion stage may be provided by a galvanically isolated, resonant, LLC based DC-DC converter 38.
  • the DC-DC converter 38 may comprise a primary side inverter 40 connected via a transformer with at least one secondary side rectifier 42.
  • the active converters 30, 38 and 36, 38, respectively, are controlled by a controller 44 provided by a single control unit.
  • the controller 44 may receive measurement signals 46 from the battery charger 10, such as the input voltage magnitude, intermediate voltage magnitude, output voltage magnitude, output current magnitude, as well as temperatures of the semiconductor switches of the converters 30, 36 and/or 38. Based on these measurement signals 46, the controller 44 may generate gate signals 48 for the converters 30, 36, 38.
  • controller 44 may comprise communication interfaces 50 to other control components of the traction vehicle, such as a further battery charger 10 or a vehicle controller.
  • Fig. 5 shows an embodiment of the first conversion stage 14 of the battery charger 10 of Fig. 1 and 2.
  • the rectifier 28 comprises three diode half-bridges 52 connected in parallel with its upper side 54 and its lower side 56 to the DC link 32. Every midpoint 58 is connected to a phase of the AC input voltage.
  • the DC-DC converter 30 is a two-phase interleaved buck converter with two half-bridges 60 of semiconductor switches 62, which half-bridges 60 are connected in parallel with its upper side 54 and its lower side 56 to the DC link 32.
  • the midpoints 58 of the half-bridges 60 are connected via an inductor 64 with the positive phase of the DC link 24.
  • the lower sides of the half-bridges 60 are connected with the negative phase of the DC link 24.
  • the rectifier 28 may be omitted.
  • the semiconductor switches 62 may of the MOSFET type with their intrinsic antiparallel diode, for example based on Si or SiC.
  • the semiconductor switches 62 may be general transistors, such as IGBTs
  • the buck type embodiment, i.e. converter 30, of the first conversion stage 14 shown in Fig 5 also may be used as for the battery charger 10 of Fig. 3 and 4.
  • the block 36 of Fig. 3 and 4 may be or may comprise a buck type converter 30 as described with respect to Fig. 5.
  • Fig.6 shows a converter 36 in a two-level boost-type active rectifier embodiment, which may be composed of three half-bridges 60 connected in parallel with its upper side 54 and its lower side 56 to the DC link 24.
  • the midpoints 58 may be connected via inductors 64 with the phases of the input voltage.
  • the midpoints 58 may connected via an inductor 64 with the positive phase of the input voltage and the lower sides of the half-bridges 60 may be connected with the negative phase of the input voltage.
  • Fig. 7 shows an embodiment of the second conversion stage 16, which is a galvanically isolated LLC type resonant converter, comprising a primary side inverter 40 composed of a half-bridge 60 and a split capacitance or split DC link 66, which are connected in parallel with its upper side 54 and its lower side 56 to the DC link 24.
  • a galvanically isolated LLC type resonant converter comprising a primary side inverter 40 composed of a half-bridge 60 and a split capacitance or split DC link 66, which are connected in parallel with its upper side 54 and its lower side 56 to the DC link 24.
  • the primary side inverter 40 is connected via a transformer 68 with a secondary side rectifier 42.
  • the primary windings of the transformer 68 are connected via an inductor 70 with the midpoints 58 of the half-bridge 60 and the split capacitance 66.
  • the split capacitance 66, the inductor 70 and the primary and secondary winding of the transformer 68 provide the resonant tank of the resonant converter 38.
  • the output part of the battery charger 10 may comprise one or more rectifiers 42 as shown in the following figures.
  • the rectifiers 42 may be connected in parallel and/or in series at their output side and/or may be connected to one or more secondary windings on their input side.
  • Fig. 8A shows several rectifiers 42 in different secondary windings of the transformer 68.
  • every rectifier 42 is connected to one secondary winding.
  • Fig. 8B shows a rectifier 42 in detail.
  • the rectifier 42 may comprise two half-bridges 60 connected in parallel with its upper side 54 and its lower side 56 to an internal DC link 72.
  • the half-bridges 60 may be connected with their midpoints 58 to the ends of a secondary winding.
  • Fig. 9A several rectifiers 42 may be connected to different secondary windings of the transformer 68.
  • every rectifier 42 is connected with two or more secondary windings.
  • Fig. 9B shows such a rectifier 42 in detail, which is mainly designed like the one of Fig. 8B.
  • the half-bridges 60 may be connected with their midpoints 58 to the ends of the two or more secondary windings, such that the respective secondary windings are connected in parallel. In such a way, the maximal current processed by one rectifier 42 may be increased.
  • Fig. 10 shows a configuration with two transformers 68, which primary windings may be connected in parallel to the inverter 40. Every transformer 68 has several secondary windings, which may be connected with rectifiers 42 as shown in Fig. 8A or 9A.
  • the currents through supply conductors 76 of neighboring primary windings and/or the supply conductors 76 of neighboring secondary windings may be symmetrized with a symmetrizing core 74, which, for example, may be a ferrite ring.
  • the symmetrizing cores 74 may be used in all secondary windings and in the multiple primary windings in the case of a solution with multiple transformers 68.
  • Fig. 11A to l lC show that the rectifiers 42, such as configured as in Fig. 8A, 9A and/or 10, may be connected in series and/or in parallel at their output side. In such a way, a large range of battery voltages may be covered.
  • the rectifiers 42 are connected in series, thus providing a high output voltage.
  • the rectifiers 42 are connected in parallel, thus providing a high output current.
  • the rectifiers 42 are grouped into groups 78, in which the rectifiers 42 are connected in series.
  • the rectifier groups 78 are then connected in parallel.
  • Fig. 12 and Fig. 13 show two possible configurations of the second conversion stage 16, which comprise three transformers 68, which are connected with their primary side to an inverter 40 as described with respect to Fig. 7.
  • the secondary windings of every transformer 68 are grouped into two groups each feeding a rectifier 42 analogously to Fig. 9A. In this way, a total of six isolated rectifiers 42 may be freely connected on their outputs.
  • Fig. 12 and 13 Two of these alternatives are shown in Fig. 12 and 13.
  • the rectifiers 42 associated with one transformer 68 are grouped into a group 78 and connected in parallel. These groups 78 are then connected in series.
  • all rectifiers 42 of all transformers 68 are connected in parallel.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Dc-Dc Converters (AREA)

Abstract

A battery charger (10) for a traction vehicle comprises a first conversion stage (14) for receiving an input voltage and for converting the input voltage into an intermediate DC voltage; and a second conversion stage (16) for converting the intermediate DC voltage into a DC charging voltage; wherein the first conversion stage (14) comprises an active converter (30, 36); and wherein the second conversion stage (16) comprises a galvanically isolated resonant DC-DC converter (38) with a primary side inverter (40) connected via a transformer (68) with at least one secondary side rectifier (42).

Description

DESCRIPTION
Battery charger for traction vehicle
FIELD OF THE INVENTION
The invention relates to the field of the electric system of traction vehicles. In particular, the invention relates to a battery charger for a traction vehicle.
BACKGROUND OF THE INVENTION
Traction vehicles, such as trains or trams, may comprise a rechargeable battery for compensating power failures of a supplying catenary network.
For recharging the battery, the electric system of the traction vehicle comprises a battery charger, which converts a supply current, for example provided by an auxiliary converter, into a charging voltage for the battery. Current battery chargers are usually based on silicon MOSFET or IGBT semiconductor technology. The use of these types of power semiconductor devices may limit the reachable switching frequency and/or voltage level of the power electronic circuitry, resulting in comparatively large, heavy and lossy battery charger solutions.
US 2012 0 262 113 Al relates to a charging apparatus of a mobile vehicle, which is adapted to receive and convert an AC input source into a DC output source for charging a rechargeable battery of the mobile vehicle. The charging apparatus includes an EMI filter, a power factor corrector, a DC/DC converter, and a voltage control unit.
US 2012 0 229 086 Al relates to a charging apparatus of a mobile vehicle which is adapted to receive and convert an external AC power source into a DC power source for charging a rechargeable battery of the mobile vehicle. The charging apparatus includes an electromagnetic interference EMI filter and a power factor corrector.
US 2014/266044 Al relates to a battery charger for an electric vehicle, with an input filter, a first conversion stage with an active rectifier and a second conversion stage with an galvanically isolated DC-DC converter. EP 1 276 218 A2 shows a power supply with a rectifier connected with a galvanically isolated DC-DC converter. A primary side inverter of the DC-DC converter comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
Chapter 11, "DC-DC Converters" in "Handbook of Automotive Power Electronics and Motor Drives", January 2005 (2005-01-01), CRC Press, pages 231-254 of James P. Johnson shows several types of DC-DC converters. In Fig. 11.14, a primary side inverter of a DC- DC converter is shown, which comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
US 2015/249395 Al shows a DC-DC conversion system, which has a first conversion stage with a buck-boost converter and a second conversion stage with a DC-DC converter having a primary side inverter, which comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
US 2002/064060 Al shows a further DC-DC conversion system with a voltage regulation stage in front of a DC-DC converter having a primary side inverter, which comprises a half bridge interconnected with a midpoint via a transformer with a midpoint of a split DC link.
US 2014/063860 Al describes a DC power source, which comprises a first stage with a boost converter made of three half-bridges and a second stage with a galvanically isolated DC-DC converter having a full bridge inverter as primary side inverter.
US 2008/112195 Al relates to a transformer circuit for a power supply, in which two rectifiers are connected to several secondary side windings of a transformer.
US 5461 297 A relates to a capacitor charging system with series or parallel connected rectifiers connected to secondary side windings of a transformer.
The article of Abdelrahman Hagar: "A new family of transformerless modular dc-dc converters for high power applications", 30 August 2011, mentions series and parallel connection of converter outputs and inputs.
US 2016/294290 Al describes a power converter, which comprises a first stage with a boost converter and a second stage with a galvanically isolated DC-DC converter having a full bridge inverter as primary side inverter. MOSFETs and switches based on wide bad gap material are mentioned as switch elements. DESCRIPTION OF THE INVENTION
It is an objective of the invention to provide a flexible, efficient and cost-effective solution for battery charging of traction vehicles. Furthermore, it is an objective of the invention to provide topologies for a battery charger for a traction vehicle, which reduce losses.
This objective is achieved by the subject-matter of the independent claim. Further exemplary embodiments are evident from the dependent claims and the following description.
The invention relates to a battery charger for a traction vehicle. For example, the battery charger may be provided as a module, i.e. with all components assembled within one mechanical device. The battery charger may be adapted for processing currents of more than 20 A. For example, at least one of the following nominal voltage and/or current ranges of batteries may be covered by the battery charger: 110 V / 75 A, 36 V / 225 A and 24 V / 337 A.
A traction vehicle may be any rail or track bound vehicle, such as a train or tram. The traction vehicle may be fed from an AC network or DC network, for example via a catenary.
According to an embodiment of the invention, the battery charger comprises: a first conversion stage for receiving an input voltage and for converting the input voltage into an intermediate DC voltage, and a second conversion stage for converting the intermediate DC voltage into a DC charging voltage, wherein the first conversion stage comprises an active converter, and wherein the second conversion stage comprises a galvanically isolated resonant DC-DC converter with a primary side inverter connected via a transformer with at least one secondary side rectifier which also may be of the active rectified kind.
The active converter of the first conversion stage is a buck converter for generating the intermediate voltage, for example either from the input voltage or the rectified input voltage. In the case of an AC input voltage, the buck converter may be controlled for power factor correction. The buck converter may be connected to an rectifier via a DC link.
The buck converter is an interleaved buck converter, which comprises at least two half- bridges connected in parallel. The midpoints of the half-bridges may be connected via an inductor with a first (such as positive) phase of the intermediate voltage and one (such as the lower) side of the half-bridges may be connected with a second (such as negative) phase of the intermediate voltage. It has to be noted that the buck converter and/or the first conversion stage may be not galvanically separated. In general, the battery charger comprises two stages of power conversion. The first conversion stage may be an AC-DC conversion stage performing power factor correction or, in the case of a DC input voltage, a DC-DC conversion stage. The first conversion stage may deliver an intermediate regulated voltage, which powers the second conversion stage. The second conversion stage may comprise a galvanically isolated DC-DC converter. The output of this DC-DC converter may feed the rechargeable battery.
The usage of a converter with active rectification for the first conversion stage and a resonant converter for the second conversion stage, which also may be equipped with an actively switched rectifier, may minimize losses. Firstly, a resonant converter, such as an LLC converter, for the second converter stage may have low losses due to topological reasons. Secondly, losses may be minimized by synchronous switching of the active rectifiers.
The DC-DC converter of the second conversion stage may be a series-resonant DC-DC converter, for example of the LLC type, which may be connected on its input to the intermediate voltage. The DC-DC converter may provide an isolation between the input and the output of the battery charger with the aid of a transformer, which also may provide an inductor for the resonance tank of the DC-DC converter with its windings. Furthermore, the DC-DC converter may provide a voltage and/or current adaptation between the output of the first conversion stage and the battery.
Furthermore, the primary side inverter of the second conversion stage comprises a half- bridge interconnected with its midpoint via an inductance with the transformer and a split capacitance connected in parallel with the half-bridge and connected with its midpoint with the transformer. The split capacitance, the inductance and the windings of the transformer may provide the resonant tank of the DC-DC converter of the second conversion stage. According to an embodiment of the invention, the secondary side rectifier of the second conversion stage is an active bridge rectifier of any type such as full- wave rectifier, voltage doubler rectifier, center-tap rectifier and alike. The second conversion stage may comprise one or more rectifiers for providing the battery charging voltage. In the case of more than one rectifier, these rectifiers may be connected in parallel and/or in series to adapt the output voltage and current. These varying connection schemes of the multitude of rectifiers are enabled by the isolating nature of the transformer providing power individually to each of the rectifiers. Furthermore, by switching the rectifiers in a synchronous mode, i.e. synchronously with the generated voltage, losses may be minimized.
The second conversion stage of the battery charger may be combined with different types of a first conversion stage. For example, different types of input voltages may be supplied to the battery charger. The battery charger may be linked to the traction system's internal 3- phase auxiliary grid, an internal DC link/source, or alternatively, provided that all overvoltage protection mechanisms are modified accordingly, directly to a DC input of the traction vehicle, in case of DC-powered vehicles.
In general, for an AC input voltage, the first conversion stage may comprise a passive rectifier in combination with a buck converter or a boost converter alone. For a DC input voltage, the first conversion stage may comprise the buck converter alone or the boost converter alone.
According to an embodiment of the invention, the first conversion stage comprises a rectifier for rectifying the input voltage, which may be a multi-phase AC voltage. The rectifier may be a diode bridge rectifier with a half-bridge for each input phase.
In general, the buck converter may be used for power factor correction of a multi-phase input power source, damping of a source network providing the input voltage that typically comprises an inverter with an undamped sine filter, and/or generation of a regulated intermediate voltage.
According to an embodiment of the invention, the input voltage is a DC voltage directly supplied to the buck converter. The combination of rectifier and buck converter may be seen as a generic input stage with the possibility to be connected to a three-phase voltage or directly to the available DC voltage from the electric system of the traction vehicle. The diode rectifier may be bypassed when a DC voltage is directly available.
The buck converter may be provided with semiconductor devices switched in synchronous mode replacing the typically used freewheeling diodes, thus achieving a reduction in conduction losses and bidirectional operation mode, needed for damping and/or optional reverse operation of the device in DC input voltage mode.
In general, the output part of the battery charger and in particular of the second conversion stage may be based on galvanically isolated building blocks in the form of rectifiers together with respective windings of the transformer, which may be rearranged, for example to cover battery voltages from 110 V down to 24 V. According to an embodiment of the invention, the second conversion stage comprises at least one transformer with at least two secondary windings and at least two rectifiers connected to the at least two secondary windings. In particular, the at least two rectifiers may be galvanically isolated from each other. The primary winding of the transformer may have a common core with the at least two secondary windings. It also may be that the second conversion stage comprises more than one transformer, i.e. more than one core. In such a way, wider power and voltage ranges may be reached by parallel, series, or combined parallel and series connection of units and/or rectifiers on a system level.
In general, the second conversion stage may be based on a flexible transformer/rectifier configuration and/or may comprise multiple secondary windings and/or multiple transformers with multiple secondary windings each feeding a rectifier, while maintaining the rest of the battery charger's hardware unchanged.
All output rectifiers may be based on active semiconductors and/or may be operated in synchronous rectification mode.
According to an embodiment of the invention, at least one rectifier is connected to at least two secondary windings. The secondary windings may be sub-grouped and/or parallel connected to feed one of the multiple rectifiers, which may provide a further level of flexibility in the output part of the second conversion stage.
According to an embodiment of the invention, currents of conductors connected to different primary windings of one or more transformers and/or conductors connected to different secondary windings of one or more transformers are equalized with a symmetrizing core surrounding the conductors. Symmetrizing cores, which may be ferrite rings surrounding two conductors, may be used for equalizing pairwise the currents of multiple primary and/or secondary transformer windings. This may ensure a more equally loading of two or more windings or transformers.
According to an embodiment of the invention, rectifiers of the second conversion stage are connected in series and/or in parallel for setting a specific charging voltage and/or current to adapt to a wide range of rechargeable batteries' voltage/current levels. It also may be that a first group of rectifiers connected in series is connected in parallel with a second group of rectifiers connected in series. Such a connection may be performed easily, when the rectifiers are galvanically isolated from each other.
According to an embodiment of the invention, the battery charger further comprises an electromagnetic interference (EMI) filter connected before the first conversion stage for filtering the input voltage. The same EMI filter may be used for filtering a DC input voltage and an AC input voltage. The EMI filter may reduce high frequency electromagnetic emissions to other neighbouring equipment and/or may reduce the susceptibility of the battery charger to external disturbances.
According to an embodiment of the invention, the battery charger further comprises a controller adapted for controlling the active converter of the first conversion stage for controlling the DC charging voltage and/or DC charging current via the intermediate voltage. It may be possible that the controller controls the first conversion stage based on the measurement signals, such that a requested battery charging voltage profile and/or charging current profile is attained.
In general, the controller may be adapted for regulating the intermediate voltage for controlling the DC charging voltage and/or current.
Furthermore, the controller may be adapted for controlling the active converter of the first conversation stage such that a power factor correction of the input voltage is performed. Both the first and second conversion stage may be controlled by one control unit providing the controller, which may regulate the intermediate voltage level in order to control the output voltage/current delivered to the rechargeable battery. Using an integrated control unit allows for integration of functions, previously managed by several distributed dedicated units, into one component.
For performing the control, the controller may monitor not only electrical but also thermal quantities of the conversion stages. Electrical and thermal measurements may be available to the central control unit. Also the battery's charging state may be monitored by the controller.
In general, the controller may generate and/or supply the gate signals of all converter semiconductors, i.e. for the buck converter or boost converter of the first conversion stage and/or for the DC-DC converter of the second conversion stage.
The controller may control the output battery charging voltage/current by controlling the converter's intermediate voltage level, i.e. by controlling the output voltage of the buck converter or boost converter.
The controller may control an input power factor correction and/or active damping by indirectly controlling the input current. The controller may monitor relevant electrical and thermal quantities in order to perform said control task and to keep the converter within safe operating margins.
The controller may provide a programming interface and/or communication interfaces. When more than one communication interface is available, the battery charger may be more flexible and simple to implement in different and complex traction platforms. In this case, the controller may provide communication with external interfaces for remote regulation and supervision of the battery charger and/or for load, current and/or voltage sharing among multiple interconnected battery chargers.
According to an embodiment of the invention, the active converter of the first conversion stage and/or the DC-DC converter of the second conversion stage are based on wide-bandgap semiconductor switches. For example, the wide-bandgap semiconductor switches may be of MOSFET type based on silicon carbide and/or of HEMT (high-electron-mobility transistor) type based on gallium nitride.
be MOSFETs based on silicon carbide and/or gallium nitride.
In general, one or both of these conversion stages may incorporate wide-bandgap semiconductor technology such as silicon carbide and/or gallium nitride. The utilization of wide-bandgap semiconductor technologies, such as silicon carbide, together with soft switching modulation schemes, may allow to reduce converter losses and consequently increase its efficiency, given their comparatively low switching losses, which in turn enables an increase in switching frequency.
An increase in switching frequency furthermore may result in compact magnetic and capacitive components. Moreover, with lower switching losses, the size of the cooling system (such as heat sinks, fans, etc.) required for evacuating the semiconductors' losses may be reduced, thus achieving an overall increase in power density.
Due to a reduction in size of the complete battery charger, the battery charger may be based on printed circuit board assemblies, reducing the manufacturing, assembly, transport and commissioning costs of the battery charger.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
As described below, it also may be that the active converter of the first conversation stage is a boost converter, which, however, is not a part of the subject-matter as described by the claims. The active converter of the first conversation stage may be a boost converter for generating the intermediate voltage from the input voltage. Alternatively, the rectifier and the buck converter may be replaced with a 2-level two or more phase boost-type active and bidirectional converter.
In general, the boost converter may be used for power factor correction of a multi-phase input power, damping of a source network providing the input voltage that typically comprises an inverter with an undamped sine filter, and/or generation of a regulated intermediate voltage. In general, the first conversion stage may comprise an active boost- type converter with sinusoidal input currents.
The boost converter may comprise at least two half-bridges, the half-bridge connected in parallel to provide the intermediate voltage.
The input voltage may be a multi-phase AC voltage and/or the boost converter may be used for maintaining a sinusoidal input voltage and/or for power factor correction. In the case of an AC supply voltage, the half-bridges may be connected with their midpoints via inductors to phases of the input voltage.
The input voltage may be a DC voltage and/or the boost converter may be used to generate the DC intermediate voltage from the DC input voltage. The boost converter may be fed directly by the DC input voltage, in which case the power factor correction feature need not be utilized.
In the case of a DC voltage, the half-bridges may be connected with their midpoints via inductors with a first (positive) phase of the DC input voltage and with one (lower) side with a second (negative) phase of the DC input voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject-matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings.
Fig. 1 schematically shows a battery charger according to an embodiment of the invention.
Fig. 2 schematically shows a battery charger according to a further embodiment of the invention.
Fig. 3 schematically shows a battery charger according to a further embodiment of the invention. Fig. 4 schematically shows a battery charger according to a further embodiment of the invention.
Fig. 5 shows a circuit diagram for a first conversion stage for a battery charger according to an embodiment of the invention.
Fig. 6 shows a circuit diagram for a further embodiment of a first conversion stage.
Fig. 7 shows a circuit diagram for a second conversion stage for a battery charger according to an embodiment of the invention.
Fig. 8A schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
Fig. 8B shows a circuit diagram for a rectifier for the output part of Fig. 8A.
Fig. 9A schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
Fig. 9B shows a circuit diagram for a rectifier for the output part of Fig. 9A.
Fig. 10 schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
Fig. 11A, 1 IB, l lC schematically show output parts for a second conversion stage for a battery charger according to an embodiment of the invention.
Fig. 12 schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
Fig. 13 schematically shows an output part for a second conversion stage for a battery charger according to an embodiment of the invention.
The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Fig. 1 to 4 show a battery charger 10, which comprises an EMI filter 12, a first conversion stage 14 and a second conversion stage 16, which are cascade-connected between an input 18 of the battery charger 10 and its output 20. With the output, which provides a DC output voltage or charging voltage, a rechargeable battery 22 of a traction vehicle may be charged. At the input 18, the battery charger 10 is supplied with an input voltage, which in the case of Fig. 1 and 3 is a three-phase AC voltage and in the case of Fig. 2 and 4 is a DC voltage. The input voltage is filtered by the EMI filter 12 and supplied to the first conversion stage 14. In both cases of an AC input voltage or a DC input voltage, the same EMI filter 12 may be used. In the latter case, only two of the three phases of the EMI filter 12 may be used.
The first conversion stage converts the input voltage into a DC intermediate voltage, which is supplied into a DC link 24 between the first conversion stage 14 and the second conversion stage 16. The second conversion stage converts the DC intermediate voltage into the DC output voltage. At the output 20 of the battery charger 10, the DC output voltage may be supplied to a further DC link 26. It has to be noted that here and in the following, every DC link may comprise a DC capacitor connected between the phases of the DC link.
In Fig. 1, the first conversion stage 14 comprises a three-phase rectifier 28 and a nonisolated DC-DC converter 30, which are connected via a DC link 32. Furthermore, for over voltage protection, a varistor 34 may connect the two phases of the DC link 32.
The rectifier 28 may be a passive rectifier and/or may be supplied with input power from a three-phase on-board AC supply. The DC-DC converter 30, which may be a buck converter, may convert the voltage of the DC link 32 into the intermediate voltage. Since the DC-DC converter 30 is controllable, a power factor correction of the input voltage/input power, at least to some degree, and a control of the intermediate voltage may be performed by the DC-DC converter 30.
In Fig. 2, in the case of a DC input voltage, for example from a DC link of a drive converter of the traction vehicle, the rectifier 28 may be bypassed and the input voltage may be supplied directly to the DC link 32. In this case, a power factor correction is not necessary and the DC-DC converter 30 only may perform a control of the intermediate voltage in the DC link 24.
In Fig. 1 and 2 a buck converter 30 may be used as active converter, In Fig. 3 and 4, the converter 36 may be or may comprise a boost converter or a buck converter.
In Fig. 3, a three-phase AC input voltage, for example from a three-phase on-board AC supply, is directly converted into the intermediate voltage by the boost or buck converter 36. The power factor correction of the input voltage/input power and a control of the intermediate voltage may be performed by converter 36.
In Fig. 4, a DC input voltage, for example directly from a DC supply network of the traction vehicle, is directly converted into the intermediate voltage by the buck or boost converter 36. In this case, a power factor correction may be not necessary and the converter 36 only may perform a control of the intermediate voltage in the DC link 24.
In both Fig. 3 and 4, for over voltage protection, a varistor 34 may connect the two phases of the DC link 24.
Furthermore, the converter 36 may be a three-phase bridge converter, which input phases in the case of Fig. 3 are connected to the different phases provided by the EMI filter 12, while in Fig. 4, the input phases of the converter 36 may be star-connected to one phase of the input voltage provided by the EMI filter 12.
In all cases, the second isolated conversion stage may be provided by a galvanically isolated, resonant, LLC based DC-DC converter 38. The DC-DC converter 38 may comprise a primary side inverter 40 connected via a transformer with at least one secondary side rectifier 42.
The active converters 30, 38 and 36, 38, respectively, are controlled by a controller 44 provided by a single control unit. The controller 44 may receive measurement signals 46 from the battery charger 10, such as the input voltage magnitude, intermediate voltage magnitude, output voltage magnitude, output current magnitude, as well as temperatures of the semiconductor switches of the converters 30, 36 and/or 38. Based on these measurement signals 46, the controller 44 may generate gate signals 48 for the converters 30, 36, 38.
Furthermore, the controller 44 may comprise communication interfaces 50 to other control components of the traction vehicle, such as a further battery charger 10 or a vehicle controller.
Fig. 5 shows an embodiment of the first conversion stage 14 of the battery charger 10 of Fig. 1 and 2.
The rectifier 28 comprises three diode half-bridges 52 connected in parallel with its upper side 54 and its lower side 56 to the DC link 32. Every midpoint 58 is connected to a phase of the AC input voltage.
The DC-DC converter 30 is a two-phase interleaved buck converter with two half-bridges 60 of semiconductor switches 62, which half-bridges 60 are connected in parallel with its upper side 54 and its lower side 56 to the DC link 32. The midpoints 58 of the half-bridges 60 are connected via an inductor 64 with the positive phase of the DC link 24. The lower sides of the half-bridges 60 are connected with the negative phase of the DC link 24.
For the battery charger of Fig. 2, the rectifier 28 may be omitted. It has to be noted that in the above and in the below, the semiconductor switches 62 may of the MOSFET type with their intrinsic antiparallel diode, for example based on Si or SiC. For other wide-bandgap materials e.g. GaN similar function of the switch is preferably attained by means of another than MOSFET structure. E.g. a HEMT device with an external diode. It also may be possible that semiconductor switches 62 are general transistors, such as IGBTs
The buck type embodiment, i.e. converter 30, of the first conversion stage 14 shown in Fig 5 also may be used as for the battery charger 10 of Fig. 3 and 4. I.e. the block 36 of Fig. 3 and 4 may be or may comprise a buck type converter 30 as described with respect to Fig. 5.
Fig.6 shows a converter 36 in a two-level boost-type active rectifier embodiment, which may be composed of three half-bridges 60 connected in parallel with its upper side 54 and its lower side 56 to the DC link 24. In the case of Fig. 3, the midpoints 58 may be connected via inductors 64 with the phases of the input voltage. In the case of Fig. 4, the midpoints 58 may connected via an inductor 64 with the positive phase of the input voltage and the lower sides of the half-bridges 60 may be connected with the negative phase of the input voltage.
Fig. 7 shows an embodiment of the second conversion stage 16, which is a galvanically isolated LLC type resonant converter, comprising a primary side inverter 40 composed of a half-bridge 60 and a split capacitance or split DC link 66, which are connected in parallel with its upper side 54 and its lower side 56 to the DC link 24.
The primary side inverter 40 is connected via a transformer 68 with a secondary side rectifier 42. The primary windings of the transformer 68 are connected via an inductor 70 with the midpoints 58 of the half-bridge 60 and the split capacitance 66. The split capacitance 66, the inductor 70 and the primary and secondary winding of the transformer 68 provide the resonant tank of the resonant converter 38.
The output part of the battery charger 10 may comprise one or more rectifiers 42 as shown in the following figures. In particular, the rectifiers 42 may be connected in parallel and/or in series at their output side and/or may be connected to one or more secondary windings on their input side.
As shown in Fig. 8A, several rectifiers 42 may be connected to different secondary windings of the transformer 68. In Fig. 8 A, every rectifier 42 is connected to one secondary winding. Fig. 8B shows a rectifier 42 in detail. The rectifier 42 may comprise two half-bridges 60 connected in parallel with its upper side 54 and its lower side 56 to an internal DC link 72. The half-bridges 60 may be connected with their midpoints 58 to the ends of a secondary winding.
As shown in Fig. 9A, several rectifiers 42 may be connected to different secondary windings of the transformer 68. In Fig. 8A, every rectifier 42 is connected with two or more secondary windings.
Fig. 9B shows such a rectifier 42 in detail, which is mainly designed like the one of Fig. 8B. The half-bridges 60 may be connected with their midpoints 58 to the ends of the two or more secondary windings, such that the respective secondary windings are connected in parallel. In such a way, the maximal current processed by one rectifier 42 may be increased.
Fig. 10 shows a configuration with two transformers 68, which primary windings may be connected in parallel to the inverter 40. Every transformer 68 has several secondary windings, which may be connected with rectifiers 42 as shown in Fig. 8A or 9A.
The currents through supply conductors 76 of neighboring primary windings and/or the supply conductors 76 of neighboring secondary windings may be symmetrized with a symmetrizing core 74, which, for example, may be a ferrite ring.
In such a way, currents in a multiple transformer and/or multiple secondary windings configuration may be equalized. The symmetrizing cores 74 may be used in all secondary windings and in the multiple primary windings in the case of a solution with multiple transformers 68.
Fig. 11A to l lC show that the rectifiers 42, such as configured as in Fig. 8A, 9A and/or 10, may be connected in series and/or in parallel at their output side. In such a way, a large range of battery voltages may be covered.
In Fig. 11 A, the rectifiers 42 are connected in series, thus providing a high output voltage.
In Fig. 11B, the rectifiers 42 are connected in parallel, thus providing a high output current.
In Fig. l lC, the rectifiers 42 are grouped into groups 78, in which the rectifiers 42 are connected in series. The rectifier groups 78 are then connected in parallel.
Fig. 12 and Fig. 13 show two possible configurations of the second conversion stage 16, which comprise three transformers 68, which are connected with their primary side to an inverter 40 as described with respect to Fig. 7. The secondary windings of every transformer 68 are grouped into two groups each feeding a rectifier 42 analogously to Fig. 9A. In this way, a total of six isolated rectifiers 42 may be freely connected on their outputs.
Two of these alternatives are shown in Fig. 12 and 13. In Fig. 12, the rectifiers 42 associated with one transformer 68 are grouped into a group 78 and connected in parallel. These groups 78 are then connected in series. In Fig. 13, all rectifiers 42 of all transformers 68 are connected in parallel.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
LIST OF REFERENCE SYMBOLS
10 battery charger
12 EMI filter
14 first conversion stage
16 second conversion stage 16
18 input
20 output
22 rechargeable battery
24 DC link
26 DC link
28 rectifier
30 non- isolated DC-DC converter
32 DC link
34 varistor
36 converter
38 isolated DC-DC converter
40 primary side inverter
42 secondary side rectifier
44 controller
46 measurement signals
48 gate signals
50 communication interfaces
52 diode half-bridges
54 upper side
56 lower side
58 midpoint
60 active half-bridge
62 semiconductor switch
64 inductor
66 split capacitance
68 transformer
70 inductor
72 DC link
74 symmetrizing core conductor rectifier group

Claims

1. A battery charger (10) for a traction vehicle, the battery charger comprising:
a first conversion stage (14) for receiving an input voltage and for converting the input voltage into an intermediate DC voltage;
a second conversion stage (16) for converting the intermediate DC voltage into a DC charging voltage;
wherein the first conversion stage (14) comprises a buck converter (30) for generating the intermediate voltage and which comprises at least two half-bridges (60) connected in parallel, wherein the midpoints (58) of the half-bridges (60) are connected via an inductor (64) with a first phase of the intermediate voltage and wherein one side of the half-bridges is connected with a second phase of the intermediate voltage;
wherein the second conversion stage (16) comprises a galvanically isolated resonant DC-DC converter (38) with a primary side inverter (40) connected via a transformer (68) with at least one secondary side rectifier (42);
wherein the primary side inverter (40) of the second conversion stage (16) comprises a half-bridge (60) interconnected with its midpoint (58) via an inductance (70) with the transformer (68) and a split capacitance (66) connected in parallel with the half-bridge (60) and connected with its midpoint (58) with the transformer (68).
2. The battery charger (10) of claim 1,
wherein the at least one secondary side rectifier (42) of the second conversion stage (16) is an active bridge rectifier.
3. The battery charger (10) of claim 1 or 2,
wherein the first conversion stage (14) comprises a rectifier (28) for rectifying the input voltage, which is a multi-phase AC voltage.
4. The battery charger (10) of one of the preceding claims,
wherein the input voltage is a DC voltage directly supplied to the buck converter
(30).
5. The battery charger (10) of one of the preceding claims,
wherein the second conversion stage (16) comprises at least one transformer (68) with at least two secondary windings and at least two rectifiers (42) connected to the at least two secondary windings.
6. The battery charger (10) of claim 5,
wherein at least one rectifier (42) is connected to at least two secondary windings.
7. The battery charger (10) of claim 5 or 6,
wherein the currents of conductors (76) connected to different primary windings of one or more transformers (68) and/or conductors (76) connected to different secondary windings of one or more transformers (68) are equalized with a symmetrizing core (74) surrounding the conductors (76).
8. The battery charger (10) of one of claims 5 to 7,
wherein rectifiers (42) of the second conversion stage (16) are connected in series.
9. The battery charger (10) of one of claims 5 to 8,
wherein rectifiers (42) of the second conversion stage (16) are connected in parallel.
10. The battery charger (10) of one of claims 5 to 9,
wherein a first group (78) of rectifiers (42) connected in series is connected in parallel with a second group (78) of rectifiers (42) connected in series.
11. The battery charger (10) of one of the preceding claims, further comprising:
an electromagnetic interference filter (12) connected before the first conversion stage (14) for filtering the input voltage.
12. The battery charger (10) of one of the preceding claims, further comprising: a controller (44) adapted for controlling the active converter of the first conversion stage (14) for controlling the DC charging voltage and/or DC charging current via the intermediate voltage.
13. The battery charger ( 10) of claim 12,
wherein the controller (44) is adapted for controlling the active converter (30, 36) of the first conversation stage (14) such that a power factor correction of the input voltage is performed.
14. The battery charger (10) of one of the preceding claims,
wherein the active converter (30, 36) of the first conversion stage (14) and/or the DC- DC converter (38) of the second conversion stage (16) are based on wide-bandgap semiconductor switches (62).
15. The battery charger ( 10) of claim 14,
wherein the wide-bandgap semiconductor switches (62) are of MOSFET type based on silicon carbide and/or of HEMT type based on gallium nitride.
EP18707723.5A 2017-03-03 2018-03-02 Battery charger for traction vehicle Withdrawn EP3577754A1 (en)

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PCT/EP2018/055228 WO2018158453A1 (en) 2017-03-03 2018-03-02 Battery charger for traction vehicle

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