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Title:
POWER CONDITIONING AND UPS MODULES
Document Type and Number:
WIPO Patent Application WO/2017/134293
Kind Code:
A1
Abstract:
The present invention provides a power conditioning module (10) for connection between an AC power supply (16) and a load (24), comprising an AC power supply input (14) for connection to the AC power supply (16), whereby the AC power supply input (14) receives a first reference (42) from the AC power supply (16), a split DC link (18) with its midpoint (26) connected to a second reference (44), a power output (22) for connection to the load (24), whereby the power output (22) receives a third reference (46) from the load (24), a first converter (34) connected between the AC power supply input (14) and the split DC link (18), whereby the first converter (34) is provided to power the split DC link (18) from the AC power supply (16), a second converter (36) connected between positive and negative halves (28, 30) of the split DC link (18) and the midpoint (26), whereby the second converter (36) is provided to transfer energy between the DC link halves (28, 30), a third converter (38) connected between the split DC link (18) and the power output (22), whereby the third converter (38) is provided to power the load (24) from the split DC link (18), whereby the first, second, and third converters (34, 36, 38) enable bi-directional energy flow between at least one of the two halves (28, 30) of the split DC link (18) and the first, second or third reference (42, 44, 46), respectively, and at least one or multiple semiconductor switching devices (84, 86) of at least one of the first, second and third converter (34, 36, 38) are provided as wide band gap semiconductor switching devices (84, 86), whereby the semiconductor switching devices (84, 86) comprise controlled and/or uncontrolled semiconductor switching devices (84, 86) in an at least three-level configuration.

Inventors:
PAATERO, Esa-Kai (Korppaanmaentie 16 B 15, Helsinki 30, 00300, FI)
NOTARI, Nicola (Via Montalbano 6, 6925 Gentilino, 6925, CH)
Application Number:
EP2017/052506
Publication Date:
August 10, 2017
Filing Date:
February 06, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ABB SCHWEIZ AG (Brown Boveri Strasse 6, 5400 Baden, 5400, CH)
International Classes:
H02M5/458; H02J9/06
Foreign References:
US20110170322A12011-07-14
US20110127837A12011-06-02
US20110051478A12011-03-03
US6266260B12001-07-24
US20110170322A12011-07-14
US20140252410A12014-09-11
Other References:
UEMURA HIROFUMI ET AL., COMPARATIVE EVALUATION OF T-TYPE TOPOLOGIES COMPRISING STANDARD AND REVERSE-BLOCKING IGBTS, 2013, XP032516295
KUNO STRAUB ET AL., NEW POWER SEMICONDUCTOR MODULE COMBINES MNPC TOPOLOGY WITH SIC SWITCHES, 18 December 2014 (2014-12-18), XP055159316
UEMURA HIROFUMI ET AL., COMPARATIVE EVALUATION OF T-TYPE TOPOLOGIES COMPRISING STANDARD AND REVERSE-BLOCKING IGBTS, 2013
KUNO STRAUB ET AL., NEW POWER SEMICONDUCTOR MODULE COMBINES MNPC TOPOLOGY WITH SIC SWITCHES, 18 December 2014 (2014-12-18)
"Wide Bandgap Semiconductors: Pursuing the Promise", ENERGY EFFICIENCY & RENEWABLE ENERGY- ADVANCED MANUFACTURING OFFICE, 1 April 2013 (2013-04-01)
Attorney, Agent or Firm:
ABB PATENT ATTORNEYS, ASSOCIATION 154, C/O ABB SCHWEIZ AG, INTELLECTUAL PROPERTY (Brown Boveri Strasse 6, 5400 Baden, 5400, CH)
Download PDF:
Claims:
Claims

1. A power conditioning module (10) for connection between an AC power supply (16) and a load (24), comprising

an AC power supply input (14) for connection to the AC power supply (16), whereby the AC power supply input (14) receives a first reference (42) from the AC power supply (16),

a split DC link (18) with its midpoint (26) connected to a second reference (44),

a power output (22) for connection to the load (24), whereby the power output (22) receives a third reference (46) from the load (24),

a first converter (34) connected between the AC power supply input (14) and the split DC link (18), whereby the first converter (34) is provided to power the split DC link (18) from the AC power supply (16),

a second converter (36) connected between positive and negative halves (28, 30) of the split DC link (18) and the midpoint (26), whereby the second converter (36) is provided to transfer energy between the DC link halves (28, 30),

a third converter (38) connected between the split DC link (18) and the power output (22), whereby the third converter (38) is provided to power the load (24) from the split DC link (18), whereby

each of the first and third converter (34, 38) enables a bi-directional energy flow between at least one of the two halves (28, 30) of the split DC link (18) via the second reference (44), and

at least one or multiple semiconductor switching devices (84, 86) of at least one of the first, second and third converter (34, 36, 38) are provided as wide band gap semiconductor switching devices (84, 86), whereby the

semiconductor switching devices (84, 86) comprise controlled and/or uncontrolled semiconductor switching devices (84, 86) in an at least three-level configuration.

2. The power conditioning module (10) according to claim 1 ,

characterized in that at least one of the first, second, and third converter (34, 36, 38) is provided for operation in continuous mode, and

at least one or multiple semiconductor switching devices (84, 86) of the converter (34, 36, 38) provided for operation in continuous mode are provided as wide band gap semiconductor switching devices (84, 86).

3. The power conditioning module (10) according to preceding claims 1 or 2, characterized in that

at least one or multiple semiconductor switching devices (84, 86) of at least one of the first and third converter (34, 36, 38) are provided as wide band gap semiconductor switching devices (84, 86).

4. The power conditioning module (10) according to any of preceding claims 1 to 3,

characterized in that

the semiconductor switching devices (84, 86) comprise Si, SiC and GaN IGBT, JFET or MOSFET as high electron mobility devices.

5. The power conditioning module (10) according to any of preceding claims 1 to 4,

characterized in that

the first, second and third reference (42, 44, 46) are interconnected.

6. The power conditioning module (10) according to any of preceding claims 1 to 5,

characterized in that

at least two of the first, second and third reference (42, 44, 46) are provided as individual references.

7. The power conditioning module (10) according to any of preceding claims 1 to 6,

characterized in that

the first reference (42) is Neutral or one phase of the AC power supply (16).

8. The power conditioning module (10) according to any of preceding claims 1 to 7,

characterized in that

the first, second, and third converters (34, 36, 38) enable bi-directional energy flow between at least one of the two halves (28, 30) of the split DC link (18) and the first, second or third reference (42, 44, 46), respectively.

9. The power conditioning module (10) according to any of preceding claims 1 to 8,

characterized in that

the AC power supply input (14) is provided as a 3-wire AC power supply input (14) for connection to a three phase AC power supply (16).

10. The power conditioning module (10) according to any of preceding claims 1 to 9,

characterized in that

the AC power supply input (14) is provided as a 4-wire AC power supply input (14) for connection to a three phase AC power supply (16) including Neutral.

1 1. The power conditioning module (10) according to any of preceding claims 1 to 10,

characterized in that

the load (24) comprises an AC load unit and/or a DC load unit.

12. The power conditioning module (10) according to any of preceding claims 1 to 1 1 ,

characterized in that

at least one out of the first, second and third converter (34, 36, 38) is of a topology of more than three levels.

13. A power conditioning system (50) comprising at least two power conditioning modules (10) according to any of preceding claims 1 to 12,

an AC power bus (52) for connection between an AC power supply (16) and the AC power supply inputs (14) of the at least two power conditioning modules (10), and

a load bus (54) for connection between the load (24) and the power outputs (22) of the at least two power conditioning modules (10).

14. An uninterruptible power supply module (60) comprising

a power conditioning module (10) according to any of preceding claims 1 to 12, and

a DC power supply input (62) for connection to a DC power supply (64), whereby the DC power supply input (62) is connected to the split DC link (18) to power the split DC link (18) from the DC power supply (64).

15. An uninterruptible power supply system (70) comprising

at least two uninterruptible power supply modules (60) according to preceding claim 14,

an AC power bus (52) for connection between an AC power supply (16) and the AC power supply inputs (14) of the at least two uninterruptible power supply modules (60), and

a load bus (54) for connection between the load (24) and the power outputs (22) of the at least two uninterruptible power supply modules (60).

Description:
Description

POWER CONDITIONING AND UPS MODULES

Technical Field

[0001] The present invention relates to the area of power conditioning and

uninterrupted power supply. In particular, the present invention relates to the area of power conditioning modules for connection between an AC power supply and a load, power conditioning systems comprising at least two power conditioning modules, an AC power bus for connection between an AC power supply and the AC power supply inputs of the at least two power conditioning modules, a load bus for connection between the load and the power outputs of the at least two power conditioning modules. Furthermore, the present invention relates to uninterruptible power supply modules comprising a power conditioning module as specified above and a DC power supply input for connection to a DC power supply, and uninterruptible power supply systems comprising at least two uninterruptible power supply modules, an AC power bus for connection between an AC power supply and the AC power supply inputs of the at least two uninterruptible power supply modules, and a load bus for connection between the load and the power outputs of the at least two uninterruptible power supply modules.

Background Art

[0002] Power quality events in electrical three-phase installations are an

important issue. Power quality events comprise any kind of

disturbances of an AC power supply covering from e.g. sags or failures of a single phase of the AC power supply up to outages of the entire AC power supply. In order to deal with power quality

events, power conditioning and uninterruptible power supply are generally known in the Art. Hence, different devices have been provided in the Art comprising power conditioning systems and uninterruptible power supply systems (UPS systems). Power conditioning systems and UPS systems distinguish in especially the presence of a secondary power supply, typically a DC power supply, which is provided in UPS systems. Depending on the system design, the power conditioning systems and UPS systems can handle different kinds of power quality events. Also the size of the DC secondary power supply has influence on the capability to deal in particular with long-lasting power quality events.

[0003] Power conditioning systems and UPS systems typically have a

modular setup. Accordingly, multiple power conditioning modules or multiple UPS modules are provided in parallel. The modules are also referred to as power electronic building blocks (PEBBs). The modules are connected at a power supply side to an AC power bus, and the modules are connected at a load side to a load bus. The AC power bus is further connected to the AC power supply, and the load bus is connected to the load.

[0004] The respective modules typically have a similar or even identical setup to make the power conditioning systems and the UPS-systems scalable and easy to maintain. Hence, a power conditioning system or an UPS-systems can easily be adapted to different loads by adding or removing modules. In case of failure, a faulty module can be easily be replaced with a working module.

[0005] In this area, on-line static systems are of major importance. A typical module of such a system comprises an AC power supply input for connection to the AC power supply, a split DC link, and a power output for connection to the load. The split DC link has a midpoint and a positive and a negative half. A first, power supply side converter, which is an AC/DC converter, also referred to as rectifier, is connected between the AC power supply input and the split DC link. A second converter is provided at the split DC link and connected between positive and negative halves of the split DC link and the midpoint to transfer energy between the DC link halves. A third converter connects the split DC link to the power output to power a load. The load is typically an AC load, so that the third converter typically is a DC/AC converter, also referred to as inverter. A UPS module typically comprises an additional DC converter, which connects the DC power source to the split DC link.

[0006] Each of the converters typically has a setup with multiple

semiconductor switching units. The semiconductor switching units may comprise controlled and/or uncontrolled semiconductor switching devices, i.e. the semiconductor switching devices can generally be provided as diodes or transistors.

[0007] In this area, multi-level technology is becoming more and more

important in the area of power conditioning systems and the UPS- systems, since it enables counterbalancing of system efficiency vs. other criteria, e.g. audible noise of the converters due to switching operations. The resulting added complexity is balanced by overall system level benefits.

[0008] In this context, document US 201 1/0170322 A1 refers to a power conversion device including an inverter for converting DC power to AC power to supply the AC power to a load. The power conversion device further comprises a converter for converting AC power from an AC power supply to DC power to supply the DC power to the inverter. The power conversion device also comprises a DC voltage converter for converting a voltage value of power stored in a storage battery to supply DC power from the storage battery to the inverter when power supply by the AC power supply is abnormal.

Furthermore, the power conversion device comprises a filter which includes a reactor and a capacitor and removes harmonics generated by the inverter. The inverter includes a three-level circuit constituted of an arm and an AC switch.

[0009] Furthermore, UEMURA HIROFUMI ET AL: "Comparative evaluation of T-type topologies comprising standard and reverse-blocking IGBTs", 2013, discusses a selection of most suitable semiconductor components for a Three-Level Three-phase T-type (3LTTC) rectifier and inverter of a high efficiency Uninterruptible Power Supply (UPS) with an output power of 20 kVA. For this purpose, conduction and switching loss models of T-type rectifiers and inverters are

discussed. Subsequently, the total semiconductor losses achieved for RB-IGBTs and for different types of conventional IGBTs are compared. Improvements achieved if the Si rectifier diodes are replaced by SiC Schottky Barrier Diodes (SiC SBDs) are evaluated. The switching loss model is parameterized with measured switching losses. According to the results of this comparison, the rectifier preferably employs RB-IGBTs to realize the bi-directional switch and SiC SBDs for the rectifier diodes; switching frequencies up to 32.5 kHz are feasible for total semiconductor losses of the rectifier of 250 W. For the inverter, a realization of the bi-directional switch using an anti-series connection of conventional IGBT/SiC SBD modules is found to be most suitable and facilitates a switching frequency of 19.7 kHz for maximum allowed losses of 250 W.

[0010] Document US 2014/252410 A1 refers to a power semiconductor module having four power terminals. An IGBT has a collector connected to the first power terminal and an emitter coupled to the third power terminal. An anti-parallel diode is coupled in parallel with the IGBT. A DC-link is connected between the second and fourth power terminals. The DC-link may involve two diodes and two IGBTs, where the IGBTs are connected in a common collector configuration. The first and second power terminals are disposed in a first line along one side of the module, and the third and fourth power terminals are disposed in a second line along the opposite side of the module. Two identical instances of the module can be interconnected together to form a three-level NPC phase leg having low stray inductances, where the phase leg has two parallel DC-links.

[001 1] Still further, KUNO STRAUB ET AL: "New Power Semiconductor Module Combines MNPC Topology with SiC Switches", 18

December 2014 refers to power semiconductor modules combining MNPC topology with SiC switches. [0012] The document "Wide Bandgap Semiconductors: Pursuing the

Promise", Energy Efficiency & Renewable Energy- Advanced

manufacturing office, 1 April 2013 refers to wide bandgap

semiconductors. Wide bandgap (WBG) semiconductor materials allow power electronic components to be smaller, faster, more

reliable, and more efficient than their silicon Si-based counterparts.

[0013] However, further improvements are desired in order to improve

system efficiency. Furthermore, based on an increased system

efficiency, further system optimizations are desired.

Disclosure of Invention

[0014] It is an object of the present invention to provide a power conditioning module, a power conditioning system comprising at least two power conditioning modules, an uninterruptible power supply module comprising a power conditioning module, and an uninterruptible power supply system comprising at least two uninterruptible power supply modules, which have an increased system efficiency. It is a further object of the present invention to enable further optimization apart from system efficiency.

[0015] This object is achieved by the independent claims. Advantageous

embodiments are given in the dependent claims.

[0016] In particular, the present invention provides a power conditioning module for connection between an AC power supply and a load, comprising an AC power supply input for connection to the AC power supply, whereby the AC power supply input receives a first reference from the AC power supply, a split DC link with its midpoint connected to a second reference, a power output for connection to the load, whereby the power output receives a third reference from the load, a first converter connected between the AC power supply input and the split DC link, whereby the first converter is provided to power the split DC link from the AC power supply, a second converter connected between positive and negative halves of the split DC link and the midpoint, whereby the second converter is provided to transfer energy between the DC link halves, a third converter connected between the split DC link and the power output, whereby the third converter is provided to power the load from the split DC link, whereby each of the first and third converter enables a bi-directional energy flow between at least one of the two halves of the split DC link via the second reference, and at least one or multiple semiconductor switching devices of at least one of the first, second and third converter are provided as wide band gap semiconductor switching devices, whereby the semiconductor switching devices comprise controlled and/or uncontrolled semiconductor switching devices in an at least three-level configuration.

[0017] The present invention also provides a power conditioning system

comprising at least two of the above power conditioning modules, an AC power bus for connection between an AC power supply and the AC power supply inputs of the at least two power conditioning modules, a load bus for connection between the load and the power outputs of the at least two power conditioning modules.

[0018] The present invention further provides an uninterruptible power supply module comprising a power conditioning module as specified above, and a DC power supply input for connection to a DC power supply, whereby the DC power supply input is connected to the split DC link to power the split DC link from the DC power supply.

[0019] The present invention still further provides an uninterruptible power supply system comprising at least two uninterruptible power supply modules as specified above, an AC power bus for connection between an AC power supply and the AC power supply inputs of the at least two uninterruptible power supply modules, and a load bus for connection between the load and the power outputs of the at least two uninterruptible power supply modules.

[0020] The basic idea of the invention is to use the wide band gap semiconductor switching devices in a multi-level topology, which allows for a reduction of turn-on and turn-off losses of the controlled and/or uncontrolled

semiconductor switching devices. The semiconductor switching devices are typically arranged in semiconductor switching units. The reduction depends on current envelopes of inductors used in the different converters. Hence, when the losses on turn-on and turn-off of the semiconductor switching devices are reduced, the respective inverters can be operated with reduced losses. Accordingly, also the module losses and the overall system efficiency can be increased, both for power conditioning and UPS. This enables the possibility to modify the control of the systems converters, the respective modules, and the respective overall systems in order to achieve further improvements, which have not been possible before due to unacceptable system efficiency reductions. In particular, by way of example, improvements in converter frequency audible noise can be achieved. Therefore, also overall system level benefits can be achieved. The use of inductors in power converters is considered common knowledge.

[0021] The improvements in system efficiency can be achieved in particular by performing an optimization on a positional basis of individual

semiconductor switching devices. Hence, optimum choice of

semiconductor switching device technology as wide band gap

semiconductor switching devices can be made for each semiconductor switching device individually and can depend on a particular position in the individual multi-level converters. The optimum choice of semiconductor switching device technology can be made under consideration of additional features including e.g. voltage stress, current distribution, forward voltage, switching behavior.

[0022] The first, second, and third references are intended as current returns for control purposes, i.e. to maintain a desired current envelope, while maintaining also voltage control of the DC links.

[0023] In a conventional two-level configuration of a converter, a hot end of an internal inductor is clamped to either positive or negative DC of the DC link, depending on a conduction state of the semiconductor switching devices or the semiconductor switching units as set by pulse width modulation (PWM) from a converter control.

[0024] In a three-level configuration, additional switches from the inductor hot end to an additional voltage are provided. The additional voltage in a three- level configuration is typically a midpoint of the split DC link. This allows clamping a voltage swing to half of the split DC link voltage. The benefit is half the switching losses. The switching losses can be calculated as inductor current * voltage swing for the duration of a switching event. These source and load voltage levels switching losses tend to dominate the overall losses, so that a reduction of these losses in the three-level configuration is beneficial.

[0025] According to a modified embodiment of the invention at least one of the first, second, and third converter is provided for operation in continuous mode, and at least one or multiple semiconductor switching devices of the converter provided for operation in continuous mode are provided as wide band gap semiconductor switching devices. The converter e.g. in the case of a DC/AC converter, switches the semiconductor switching devices to achieve an AC current output according to an envelope based on the provided DC power. Hence, pulsed DC current is provided to achieve the AC output, whereby the pulses are generated by the semiconductor switching devices. On a rising edge of the pulse, a controlled

semiconductor switching device, e.g. an IGBT, of a semiconductor switching unit carries the current, on the falling edge, an uncontrolled semiconductor switching device, e.g. a diode, of the semiconductor switching unit carries the current.

[0026] There are two general scenarios, which are continuous or discontinuous current. With continuous current, a ripple amplitude, i.e. a peak to peak amplitude between two switching events, can be kept smaller than when providing discontinuous current. This is because in continuous mode, the current is still flowing when the next switching event occurs. Accordingly, the current will not drop to zero until the AC current output turns zero. In case the semiconductor switching device has reverse recovery losses, these losses occur using known semiconductor switching devices.

However, using wide band gap semiconductor switching devices, these losses can be reduced.

[0027] As mentioned before, the use of inductors in power converters is

considered common. Inductor losses depend heavily on ripple amplitude. When the ripple amplitude is smaller, the inductor works better but turn-on current becomes higher. Hence, a wide band gap device, which helps to reduce the ripple amplitude, may enable an overall efficiency benefit. In this case, diode recovery losses can be avoided, whereby the inductor losses are only slightly increased. Accordingly, when using wide band gap semiconductor switching devices, these losses can be reduced, so that the system efficiency can be increased.

According to a modified embodiment of the invention at least one or multiple semiconductor switching devices of at least one of the first and third converter are provided as wide band gap semiconductor switching devices. In particular for the first and third converter, the current usually is continuous. This is based e.g. on filter scaling on source and/or load side of the respective module or system. Filter are required based on e.g. EMC and functional requirements, according to which current injection can be limited to a certain ripple amplitude. However, the ripple amplitude also depends on the application, thus there will be both turn-on and turn-off losses. The loss distribution depends on the design of a particular module. However, trade-offs are possible between inductor cost/power loss or general cost/power loss in semiconductor switching devices. With a large ripple amplitude, e.g. diode turn-off current will be relatively low so the above will apply, but a higher ripple current can be injected to the AC power supply side or the load side, which may be disadvantageous for some applications. Furthermore, for some positions of the semiconductor switching units or even the individual semiconductor switching devices, e.g. the semiconductor switching units/devices in the second converter, e.g. operation in discontinuous mode may be desired, e.g. based on a very simple control, the current not seen by source or load, and relatively modest EMC considerations. Thus there will be no turn-on losses related to diode commutation for the controlled switches and thus only turn-off losses for the controlled semiconductor switching devices. As there are no diode related turn-on loss, wide band gap devices offer a smaller benefit for the diode position and due to higher cost may be not applied, so that overall costs can be kept small. [0029] According to a modified embodiment of the invention the semiconductor switching devices comprise Si, SiC and GaN IGBT, JFET or MOSFET as high electron mobility devices. In particular, silicon carbide (SiC) and gallium nitride (GaN) are suitable materials for providing wide band gap semiconductor switching devices. In particular, the controlled

semiconductor switching devices, e.g. IGBT, JFET or MOSFET, can be provided as wide band gap semiconductor switching devices. Anyway, also uncontrolled semiconductor switching devices, i.e. diodes, can benefit from the implementation as wide band gap semiconductor switching devices. In the area of wide band gap semiconductors, in particular silicon carbide and gallium nitride have proven suitable.

[0030] According to a modified embodiment of the invention the first, second and third reference are interconnected. Hence, a single reference can be provided and used throughout the voltage conditioning module/voltage conditioning system/UPS module/UPS system, which facilitates setup and installation.

[0031] According to a modified embodiment of the invention at least two of the first, second and third reference are provided as individual references. Hence, depending e.g. on availability of references, different references can be used. This enables a high variety in installations, e.g. when using 3- or 4-wire installations of the AC power supply and the load. The first, second, and third references are intended as current returns for control purposes, i.e. to maintain a desired current envelope, while maintaining also voltage control of the split DC link.

[0032] According to a modified embodiment of the invention the first reference is Neutral or one phase of the AC power supply. Hence, any wire of the AC power supply can be used as reference, independently from the

installation of the AC power supply being provided as a 3- or 4-wire installation. Also an artificial Neutral can be generated and provided as first reference.

[0033] According to a modified embodiment of the invention the third reference is Neutral or one phase of the load. Hence, any wire of the load can be used as reference, independently from the installation of the load as a 3- or 4- wire installation. Also an artificial Neutral can be generated and provided as third reference.

[0034] According to a modified embodiment of the invention, the first, second, and third converters enable bi-directional energy flow between at least one of the two halves of the split DC link and the first, second or third reference, respectively.

[0035] According to a modified embodiment of the invention the AC power supply input is provided as a 3-wire AC power supply input for connection to a three phase AC power supply. 3-wire installations are typical e.g. for installation made in the US. However, also the internal generation of an artificial Neutral within a module is possible, so that this can be used as reference.

[0036] According to a modified embodiment of the invention the AC power supply input is provided as a 4-wire AC power supply input for connection to a three phase AC power supply including Neutral. 4-wire installations including three phases and Neutral are typical e.g. for installation made in Europe.

[0037] According to a modified embodiment of the invention the load comprises an AC load unit and/or a DC load unit. For the voltage conditioning module/voltage conditioning system/UPS module/UPS system, there is no general difference in providing AC or DC power to the load. Merely the third converter has to be selected appropriately as DC/AC converter, also referred to as inverter, in the case of an AC load, or as DC/DC converter to provide a desired DC voltage in case the load is a DC load. Also combinations of DC loads and AC loads are possible. This merely requires the use of parallel converters for providing AC or DC output to the respective load.

[0038] According to a modified embodiment of the invention at least one out of the first, second and third converter is of a topology of more than three levels. In a multi-level configuration more than three levels, additional switches from the inductor hot end to additional voltages are provided. This allows to further reduce a voltage swing, which further reduces switching losses. Since the source and load voltage level switching losses tend to donninate the overall losses, a further reduction of these losses compared to the 3-level configuration is beneficial.

Brief Description of Drawings

[0039] These and other aspects of the invention will be apparent from and

elucidated with reference to the embodiments described hereinafter.

[0040] In the drawings:

[0041] Fig. 1 shows a power conditioning module according to a first,

preferred embodiment as schematic drawing,

[0042] Fig. 2 shows a power conditioning system according to a second embodiment with multiple power conditioning module of the first embodiment as schematic drawing,

[0043] Fig. 3 shows an uninterruptible power supply module according to a third embodiment as schematic drawing,

[0044] Fig. 4 shows an uninterruptible power supply system according to a fourth embodiment with multiple uninterruptible power supply modules of the third embodiment as schematic drawing,

[0045] Fig. 5 shows an exemplary setup of an AC/DC power converter in accordance with the first and third embodiment according to a fifth embodiment as schematic drawing,

[0046] Fig. 6 shows an exemplary setup of an AC/DC power converter in accordance with the first and third embodiment according to a sixth embodiment as schematic drawing,

[0047] Fig. 7 shows an exemplary setup of an AC/DC power converter in accordance with the first and third embodiment according to a seventh embodiment as schematic drawing,

[0048] Fig. 8 shows a detailed view of a semiconductor switching unit in accordance with the first and third embodiment according to an eighth embodiment as schematic drawing,

[0049] Fig. 9a shows a detailed view of an AC power supply provided as 4- wire power supply and connected at a power supply side of a module in accordance with the first and third embodiment according to a ninth embodiment as schematic drawing,

[0050] Fig. 9b shows a detailed view of an AC power supply provided as 3- wire power supply and connected at a power supply side of a module in accordance with the first and third embodiment according to a tenth embodiment as schematic drawing,

[0051] Fig. 10 shows the AC/DC power converter of the fifth embodiment with a PWM switching scheme as schematic drawing, and

[0052] Fig. 1 1 shows a current diagram with an AC envelope and PWM

current pulses for continuous and discontinuous current.

Detailed Description of the Invention

[0053] Fig. 1 shows a power conditioning module 10 according to a first,

preferred embodiment. At its power supply side 12, the power

conditioning module 10 comprises an AC power supply input 14 for connection to an AC power supply 16. In this embodiment, as can be seen in detail in Fig. 9a with respect to the ninth embodiment, the AC power supply input 14 is provided as a four-wire AC power supply input 14 for connection to a three phase AC power supply 16

including Neutral. According to a modified embodiment of the

invention the AC power supply input 14 is provided as a three-wire

AC power supply input 14 for connection to a three phase AC power supply 14, as can be seen in detail in Fig. 9b with respect to the tenth embodiment.

[0054] The power conditioning module 10 further comprises a split DC link

18. At its load side 20, the power conditioning module 10 comprises a power output 22 for connection to a load 24. The split DC link 18 has a midpoint 26 and a positive and a negative half 28, 30.

Capacitors 32 are provided between the positive and negative half 28, 30 and the midpoint 26 for buffering the split DC link 18.

[0055] A first converter 34 is provided at the power supply side 12. The first

converter 34 is an AC/DC converter, also referred to as rectifier, which is in detail connected between the AC power supply input 14 and the split DC link 18. A second converter 36 is provided to connect the positive and negative halves 28, 30 of the split DC link 18 with the midpoint 26 to transfer energy between the DC link halves 28, 30. A third converter 38 connects the split DC 18 link to the power output 22 to power the load 24. In this embodiment, the load 24 is an AC load, and the third converter 38 is a DC/AC converter, also referred to as inverter.

[0056] Still further, the power conditioning module 10 shown in Fig. 1 comprises a module controller 40, which controls the operation of the three converters 34, 36, 38.

[0057] Further details in respect to the converters 34, 36, 38 will be

discussed below.

[0058] As can be further seen in Fig. 1 , the AC power supply 26 has a first

reference 42, which is Neutral in this embodiment. The power conditioning module 10 receives the first reference 42 - in a way not explicitly shown in Fig. 1 - via the AC power supply input 14. The midpoint 26 of the split DC link 18 is connected to a second reference 44. As can be further seen in Fig. 1 , the load has a third reference 46, and the power conditioning module 10 receives the third reference 46 - in a way not explicitly shown - via the power output 22. The first, second, and third converters 34, 36, 38 enable bi-directional energy flow between the two halves 28, 30 of the split DC link 18 and the first, second or third reference 42, 44, 46, respectively. Hence, the first, second, and third references 42, 44, 46 are provided as current returns for control purposes, i.e. to maintain a desired current envelope, while maintaining also voltage control of the split DC link 18.

[0059] In this embodiment, the first reference 42 is Neutral of the AC power

supply 16. Furthermore, in this embodiment, the third reference 46 is Neutral of the load 24. In alternative embodiments, the first and third reference 42, 46 are formed by a phase of the AC power supply 16 and the load 24, respectively.

[0060] In this embodiment the first, second and third reference 42, 44, 46 are provided as individual references. Accordingly, the first, second, and third references 42, 44, 46 are intended as individual current returns for control purposes, i.e. to maintain a desired current envelope, while maintaining also voltage control of the split DC link 18.

[0061] According to a modified embodiment, the first, second and third reference 42, 44, 46 are interconnected.

[0062] Fig. 2 shows a power conditioning system 50 according to a second

embodiment. The power conditioning system 50 comprises multiple power conditioning modules 10 according to the first embodiment. The power conditioning system 50 further comprises an AC power bus 52 for connection between an AC power supply 16 and the AC power supply inputs 14 of the power conditioning modules 10 and a load bus 54 for connection between the load 24 and the power outputs 22 of the power conditioning modules 10. Hence, the power conditioning modules 10 are connected in parallel between the AC power bus 52 and the load bus 54. The setup of each of the power conditioning modules 10 of the power conditioning system 50 is as described above with respect to the first embodiment. A repeated discussion of the power conditioning module 10 is omitted.

[0063] Fig. 3 shows an uninterruptible power supply (UPS) module 60 according to a third embodiment. The UPS module 60 comprising a power conditioning module 10 according to the first embodiment and a DC power supply input 62 for connection to a DC power supply 64. The DC power supply input 62 is connected to the split DC link 18 to power the split DC link 18 from the DC power supply 64. The setup of the power conditioning module 10 of the UPS module 60 is as described above with respect to the first embodiment. Accordingly, the same reference numerals of the power conditioning module 10 of the first embodiment are used also for the UPS module 60. A repeated discussion of the power conditioning module 10 is omitted.

[0064] Fig. 4 shows an uninterruptible power supply (UPS) system 70 according to a fourth embodiment. The UPS system 70 according to the fourth embodiment comprises multiple uninterruptible power supply modules 60 of the third embodiment. The UPS system 70 further comprises an AC power bus 52 for connection between an AC power supply 16 and the AC power supply inputs 14 of the UPS modules 10 and a load bus 54 for connection between the load 24 and the power outputs 22 of the UPS modules 10. Hence, the UPS modules 10 are connected in parallel between the AC power bus 52 and the load bus 54. The setup of each of the UPS modules 10 of the UPS system 70 is as described above with respect to the third embodiment. A repeated discussion of the UPS module 60 is omitted.

[0065] Typical configuration for the converters 34, 36, 38 of the power

conditioning module 10 of the first embodiment and the UPS module 60 of the third embodiment, as shown in Figs. 1 and 3, can be seen in Figs. 5 to 7 with respect to the fifth, sixth, and seventh

embodiment, respectively. The principles of the converters of the fifth, sixth, and seventh embodiment can be applied to any of the first, second and third converter 34, 36, 38 of any of the previous embodiments.

[0066] Fig. 5 shows by way of example a setup of the first converter 34

according to a fifth embodiment. The first converter 34 of the fifth embodiment corresponds to the first converter 34 used in the power conditioning module 10 of the first embodiment and the UPS module 60 of the third embodiment.

[0067] As can be seen in Fig. 5, the first converter 34 comprises an

inductance 80 and multiple semiconductor switching units 82, also denoted as SD in the figures. Each semiconductor switching unit 82 implements a functional switch and comprises at least one

semiconductor switching device 84, 86, typically at least two

semiconductor switching devices 84, 86. As can be seen with respect to Fig. 8 and the eights embodiment, the semiconductor switching unit 82 can be implemented in different ways using controlled and uncontrolled semiconductor switching devices 84, 86, i.e. transistors and diodes, respectively. The different implementations of the

semiconductor switching unit 82 are given merely by way of example. Also different configurations of the semiconductor switching unit 82 can be provided within the scope of this invention. Furthermore, each of the shown senniconductor switching units 82 can have a different setup compared to other senniconductor switching units 82.

[0068] The principles discussed above with respect to the first converter 34

of the fifth embodiment apply identically to the first converter 34 of the sixth embodiment, which is shown in Fig. 6.

[0069] Fig. 7 shows the setup of the first converter 34 according to the

seventh embodiment. In general, the principles discussed above with respect to the first converter 34 of the fifth or sixth embodiment apply also to the first converter 34 of the seventh embodiment. However, as can be seen in Fig. 7, the first converter 34 of the seventh

embodiment also comprises single diodes 88.

[0070] In the above embodiments, at least one or multiple semiconductor

switching devices 84, 86 of at least one of the first, second and third converter 34, 36, 38 are provided as wide band gap semiconductor switching devices 84, 86 in a three-level configuration. According to a modified embodiment at least one out of the first, second and third converter 34, 36, 38 is of a topology of more than three levels.

[0071] Accordingly, individual semiconductor switching devices 84, 86 can

be provided with a wide band gap. In this embodiment, the wide band gap is achieved using semiconductor switching devices 84, 86

comprising Si, SiC and GaN IGBT, JFET or MOSFET as high

electron mobility devices. Further preferred, the semiconductor

switching devices 84, 86 are made of silicon carbide (SiC) and

gallium nitride (GaN).

[0072] The operation of the first converter 34 in three-level configuration is by way of example indicated in Fig. 10 with reference to the first converter 34 of the fifth embodiment. The first converter 34 operates between the positive half 28 and the negative half 30 of the split DC link 18. As additional voltage in the three-level configuration is used the midpoint 26 of the split DC link 18. Accordingly, a voltage swing 90 is limited to half of the voltage of the split DC link 18. A PWM switching scheme is applied to the voltage swing 90. In a two level configuration, the voltage swing would be between positive half 28 and negative half 28 of the split DC link 18. [0073] The individual senniconductor switching devices 84, 86 to be provided with a wide band gap can be selected depending on the operation of the respective converters 34, 36, 38. There are two general scenarios, which are continuous or discontinuous current, as can be seen in Fig. 1 1 , which shows a current diagram with an AC envelope and PWM driven current pulses for continuous and discontinuous current. With continuous current, a ripple amplitude 92, i.e. a peak to peak amplitude between two switching events, can be kept smaller than when providing discontinuous current. This is because in continuous mode, the current is still flowing when the next switching event occurs. Accordingly, the current will not drop to zero until the AC current output 94 turns zero. However, with the wide band gap semiconductor switching devices 84, 86 having low reverse recovery losses, no essential losses occur.

[0074] Preferably the first and third converter 34, 38 is provided for

operation in continuous mode, and the semiconductor switching devices 84, 86 of the first and third converter 34, 38 are provided as wide band gap semiconductor switching devices 84, 86. As can be seen in Fig. 1 1 , by way of example the third converter 38 switches its semiconductor switching devices 84, 86 to achieve the AC current output 94 based on DC power provided from the split DC-link 18. Hence, pulsed DC current is provided to achieve the AC current output 94, whereby the pulses are generated by the semiconductor switching devices 84, 86. On a rising edge of the pulse, a controlled semiconductor switching device 84, e.g. an IGBT, of a semiconductor switching unit 82 carries the current, the current is on a controlled semiconductor switching device 84. On the falling edge, an

uncontrolled semiconductor switching device 86, e.g. a diode, of the semiconductor switching unit 82 carries the current, i.e. the current is on an uncontrolled semiconductor switching device 86.

[0075] Furthermore, for some particular positions of the semiconductor

switching units 82 or even the individual semiconductor switching devices 84, 86, e.g. operation in discontinuous or continuous mode may be desired, so that individual semiconductor switching units 82 or even the individual semiconductor switching devices 84, 86 are provided as wide band gap semiconductor switching devices 84, 86. Hence, improvements in system efficiency can be achieved in particular by performing an optimization on a positional basis of individual semiconductor switching devices 84, 86. The choice of a technology for each semiconductor switching device 84, 86 can be made individually under consideration of additional features including e.g. voltage stress, current distribution, forward voltage, switching behavior or others.

[0076] 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 be disclosed embodiments can be understood and effected by those skilled in the art in practicing 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. 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 scope.

Reference signs list

10 power conditioning module

12 power supply side

14 AC power supply input

16 AC power supply

18 split DC link

20 load side power output

load

midpoint

positive half

negative half

capacitor

first converter

second converter

third converter

module controller

first reference

second reference

third reference

power conditioning system

AC power bus

load bus

uninterruptible power supply module

DC power supply input

DC power supply

uninterruptible power supply system

inductance

semiconductor switching unit

controlled semiconductor switching device, transistor uncontrolled semiconductor switching device, diode diode

voltage swing

ripple amplitude

AC current output

current on controlled semiconductor switching device current on uncontrolled semiconductor switching device