Device for converting a direct current into a single-phase or multi-phase alternating current

Abstract

Device for converting a direct current into a single-phase or multi-phase alternating current, comprising - a power switching device (10) comprising a switching unit (11, 12, 13) with a number of power switching elements for each phase (P1, P2, P3), - a driver device (20) which, for controlling a respective switching unit (11, 12, 13), comprises a driver unit (21, 22, 23) assigned to the switching unit (11, 12, 13), - an intermediate circuit capacitor device (30), and - a control unit (40) for controlling and monitoring the power switching device (10), wherein the components required for the conversion of a phase (P1, P2, P3) are arranged in a respective module (1, 2, 3).

Description

[0001] The invention relates to a device for converting a direct current into a single-phase or multi-phase alternating current.

[0002] Such a device is called an inverter and is used, for example, in vehicles in which a multi-phase drive motor is fed from an energy storage device that provides a direct voltage or direct current. In the application described in this vehicle, a rechargeable high-voltage (HV) battery or a fuel cell is used as the energy source. The drive motors are generally three-phase. Inverters are also used, for example, in photovoltaics, uninterruptible power supplies (UPS) or for lighting purposes. In the following description, reference is made exclusively to an application in a vehicle; this is done merely as an example and is not to be regarded as limiting.

[0003] Fig. Figure 1 shows a schematic, exploded view of the structure of a typical three-phase inverter 100. The inverter 100 includes a power switching device 10, a driver device 20, a DC link capacitor device 30, and a control unit 40.

[0004] The power switching device 10 comprises a switching unit 11, 12 and 13 for each phase P1, P2, P3. The switching units 11, 12, 13 are, for example, half-bridges formed from two power switching elements, e.g., MOSFETs, connected in series. The switching units 11, 12, 13 are arranged in a common housing (not explicitly shown), in which the switching units 11, 12, 13 are arranged in a common plane on respective carrier plates or a common carrier plate (so-called circuit board(s)). The carrier plate or the carrier plates are connected to a common heat sink, which dissipates the heat (power loss) generated during operation of the power switching elements to the outside and represents, for example, a base plate of the housing.

[0005] A multitude of electrical connections lead out of the housing. A direct voltage or direct current is supplied to the switching units 11, 12, 13 via the DC and BP connections, which are provided separately for each switching unit 11, 12, 13. The DC connections of a respective switching unit 11, 12, 13 can be electrically connected to one another outside or inside the housing. Likewise, the BP connections of a respective switching unit 11, 12, 13 can be electrically connected to one another outside or inside the housing. An output OUT_P1 of the switching unit 11 represents the output of the first phase P1 of the inverter, which is connected to an associated first phase of a drive machine (not shown). An output OUT_P2 of the switching unit 12 represents the output of the second phase P2 of the inverter 100, which is connected to an associated second phase of the drive machine.An output OUT_P3 of the switching unit 13 represents the output of the third phase P3 of the inverter 100, which is connected to an associated third phase of the drive machine.

[0006] Further connections are provided for each control unit 11, 12, 13 to the driver device 20 for transmitting a respective driver signal TS_P1, TS_P2, and TS_P3 and for connecting the respective control units 11, 12, 13 to the intermediate circuit capacitor device 30. These are designated L2_P1, L2_P2, and L2_P3.

[0007] The driver device 20 comprises a driver unit 21, 22, 23 for each phase P1, P2, P3. The driver unit 21 is assigned to the switching unit 11 and outputs the driver signal TS_P1 to it. The driver unit 22 is assigned to the switching unit 12 and outputs the driver signal TS_P2 to it. The driver unit 23 is assigned to the switching unit 13 and outputs the driver signal TS_P3 to it. The driver units 21, 22, 23 are arranged in a common housing (hereinafter: driver housing), not explicitly shown, wherein this driver housing is arranged on the housing of the power switching device 10. A mechanical connection between the two units is established, at least in part, by the connection contacts for the driver signals TS_P1, TS_P2, and TS_P3. The driver housing also includes electrical connections L1_P1, L1_P2, L1_P3 to the intermediate circuit capacitor device 30.

[0008] The control unit 40 is arranged on the driver device 20. The control unit 40 comprises all components necessary for controlling and monitoring the inverter. These components are arranged in a common housing (hereinafter referred to as the control unit housing) not explicitly shown, with this control unit housing being arranged on top of the driver housing. To establish an electrical connection between the control unit housing and the driver housing, corresponding connections are led out of the housings. In particular, a respective driver signal GDS_P1, GDS_P2, GDS_P3 for controlling the switching units 11, 12, 13 is transmitted from the control unit to the driver device.

[0009] The intermediate circuit capacitor device 30, which comprises one or more capacitors, is coupled as a separate component laterally to the housing stack comprising the power switching device 10, the driver device 20 and the control unit 40.

[0010] The connections of the power switching device 10 are designed, for example, as screw connections, ie the mentioned connections DC, BP, OUT_P1, OUT_P2, OUT_P3, L2_P1, L2_P2, L2_P3 are designed as contact surfaces with a respective bore, which can be mechanically and electrically connected, for example, with a screw bolt.

[0011] Due to the described design, the inverter 100 is significantly large. Particularly when used in a vehicle, this can lead to installation problems in confined spaces, since optimal cooling of the power switching device 10 is essential for proper operation. In some cases, the inverter may then have to be installed in locations that are not suitable.

[0012] A further disadvantage of the described inverter is that both the power paths (DC, BP, OUT_P1, OUT_P2, OUT_P3, L1_P1, L1_P2, L1_P3, L2_P1, L2_P2, L2_P3) and the logic paths (GDS_P1, GDS_P2, GDS_P3, TS_P1, TS_P2, TS_P3) require a complex connection technology that must withstand the vibrations occurring in a vehicle.

[0013] A further disadvantage is that, although the power switching elements of the switching units 11, 12, 13 are well cooled due to their direct connection to a heat sink, the intermediate circuit capacitor device 30 is not optimally connected to the heat sink, which is crucial for the service life of the inverter.

[0014] In addition, EMC (electromagnetic compatibility) issues can arise, partly due to the relatively long cables used to transmit high-frequency signals. To avoid EMC problems, complex and expensive connection technology must be used between the individual mechanical components.

[0015] From WO 2012 / 164 099 A2 an inverter is known, comprising a DC interface, an AC interface, a set of switchable half-bridges coupled to the DC interface, each half-bridge comprising two blocks each having a switch and a diode, a control unit configured to switch the switches of the half-bridges with a predefined relative phase shift between different half-bridges, and a filter unit arranged between the AC interface and a plurality of parallel paths relating to the plurality of half-bridges, the filter unit comprising a coupled inductor inductively coupling the plurality of parallel paths.

[0016] From DE 197 11 016 A1, a converter with a modular, at least two-part structure is known, which has a carrier module and at least one module that can be connected to the carrier module and withdrawn from the carrier module, wherein all electrical connections between the carrier module and the withdrawable module are designed to be pluggable.

[0017] From DE 10 2005 045 072 A1 a converter arrangement with a modular structure is known, wherein the converter arrangement has a plurality of independent converter units and a one-piece wire-written printed circuit board on which the plurality of converter units are connected in parallel, wherein at least one predetermined breaking point is arranged between the converter units, so that the converter units remain connected in parallel even if they break at the predetermined breaking point through wires in the printed circuit board.

[0018] From US 2008 / 0 136 265 A1, a power conversion device is known which comprises a plurality of power modules, a plurality of capacitors and a busbar, wherein each of the power modules has a DC connection section and an AC connection section, wherein each of the power modules is configured and arranged to convert a DC current input from the DC connection section into a corresponding phase of a multi-phase AC current and output the multi-phase AC current to the AC connection section, wherein the busbar forms an inter-phase current path between the adjacent power modules and an inter-phase current path between one of the power modules and a corresponding capacitor, such that the impedance of the inter-phase current path is smaller than the impedance of the inter-phase current path.

[0019] It is therefore an object of the present invention to provide a device for converting a direct current into a single-phase or multi-phase alternating current, which is structurally and / or functionally improved.

[0020] This object is achieved by a device according to the features of patent claim 1. Advantageous embodiments emerge from the dependent patent claims.

[0021] A device for converting direct current into single-phase or multi-phase alternating current is proposed, which device comprises a power switching device, a driver device, an intermediate circuit capacitor device, and a control unit. The power switching device comprises a switching unit with a number of power switching elements for each phase. The switching unit is, for example, a half-bridge formed from two power switching elements, such as MOSFETs, connected in series. The driver device comprises a driver unit assigned to the switching unit for controlling a respective switching unit. This means that the number of driver units depends on the number of switching units and thus the number of phases. The intermediate circuit capacitor device comprises one or more capacitors with very high power density and serves to couple the DC voltage and the AC voltage network.The control unit is intended to control and monitor the power switching device. According to the invention, the components required for converting a phase are arranged in a respective module.

[0022] The device according to the invention has a number of modules corresponding to the number of phases. The fact that cable lengths can be minimized within a module results in reduced EMC emissions due to the low-inductance connection of the intermediate circuit capacitor to the other electronic components. The integration of all components required for a phase also enables a reduction in system interfaces. This makes an inverter according to the invention less susceptible to vibrations, which favors its use in vehicles.

[0023] Furthermore, a better thermal connection of the DC link capacitor to a heat sink is possible, which leads to an increased service life of the DC link capacitor.

[0024] In one embodiment, the components required for converting a phase comprise at least the switching unit with the number of power switching elements (e.g., the respective half-bridge), the driver unit assigned to the switching unit for controlling the number of power switching elements of the switching unit, and a phase intermediate circuit capacitor. Optionally, the components required for converting a phase can comprise a control unit that controls the driver unit. Alternatively, a common control unit can also be provided for all phases of the device, which is then implemented in a component different from the module(s). The components required for controlling a device according to the invention (such as, for example, a microcontroller, passive components, etc.)) can also be arranged in a distributed manner, so that the components required for converting a particular phase are located in the module's control unit, and higher-level components, which are required, for example, for the interaction of several phases, are located in a control unit external to the module. Optionally, the components required for converting a phase can also include a current measuring device.

[0025] The components can be selectively integrated into a common semiconductor. For example, the power switching unit and the driver unit can be integrated into a common semiconductor. The intermediate circuit capacitor can also be integrated into the semiconductor. A current measuring device that measures the current flowing on the AC side can be integrated into the semiconductor. The intermediate circuit capacitor can be designed as a film capacitor, for example. The intermediate circuit capacitor can also be designed as a ceramic capacitor.

[0026] The components required for phase conversion can be arranged in a common housing. This allows the module to be manufactured with a small number of components and a low level of complexity. It requires only a small amount of space. The weight of such a module can be kept low.

[0027] The components required for phase conversion can be arranged and interconnected in a common plane on a carrier or circuit board. The carrier or circuit board can be arranged in the housing. The carrier or circuit board can be arranged on a, preferably thin, base of the housing. The carrier or circuit board can form the base of the housing. The carrier or circuit board can be formed as a single piece or in multiple pieces.

[0028] The components required for phase conversion can be directly connected to a common heat sink, with the components arranged in a common plane being equidistant from the heat sink. The heat sink can be connected to the bottom of the housing. The heat sink can be connected to the carrier or the circuit board. The heat sink can form the bottom of the module. The heat sink is preferably made of a material with good thermal conductivity, e.g., a metal. Aluminum is preferred for weight reasons. The heat sink can be designed as a plate. The heat sink can have a number of cooling fins.

[0029] The module components required for phase conversion can be encapsulated. This prevents electrical connections made within the module, such as bonding wires, from degrading due to vibrations during module operation. The encapsulation material also provides mechanical protection for the components within the module. A permanently elastic encapsulation material, such as soft encapsulation (silicone) or hard encapsulation (epoxy resin), can be used as the encapsulation material.

[0030] A phase of the device can be formed by one module or several modules connected in parallel. This is useful if, on the one hand, the current flowing through each module needs to be reduced compared to a single module per phase. This also means that less heat needs to be dissipated to the outside per module. Furthermore, the respective intermediate circuit capacitor is not subjected to as much stress, which increases the service life of the device. On the other hand, by connecting several modules in parallel, the current per phase can be increased compared to a single module. In this configuration, it is useful to provide a common control unit for the modules connected in parallel.

[0031] The modular design facilitates easy scaling of the device for converting direct current into alternating current. In particular, there is no limitation on the number of phases. Only a number of modules corresponding to the desired number of phases needs to be provided and connected appropriately. The advantage of scalability is particularly evident when deviating from a B6 bridge circuit (i.e., 3 phases or 6 phases, or generally 3 * n phases) and, for example, four phases are required to control an electrical machine.

[0032] The modules, especially those of different phases, can be arranged or positioned at spatially separate locations. This allows for the installation of a multi-phase inverter (or a single-phase inverter comprising several modules connected in parallel) even in unfavorable spatial conditions, such as those often found in a vehicle. For example, it is possible to install the modules in locations that enable particularly good cooling performance, which is usually not possible given the size of a conventional multi-phase inverter.

[0033] The modules of one and / or more phases can be designed as mechanically independent units. This facilitates their arrangement at spatially separate locations, with the advantages described above.

[0034] A device as described above is intended in particular for controlling an electric drive motor of a vehicle. In general, the device can also be used, for example, in photovoltaics, uninterruptible power supplies (UPS), or for lighting purposes.

[0035] The invention has a number of advantages:

[0036] Modularization can reduce the complexity of multiphase inverters. Modularization enables, for example, easy scaling, independent of the number of phases and / or the currents required per phase, by interconnecting modules in a suitable manner.

[0037] The fact that cable lengths can be minimized within a module results in reduced EMC emissions due to the low-inductance connection of the driver unit to the switching unit. The low-inductance connection of the DC link capacitor to the other electronic components reduces switching overshoot, resulting in higher performance of the overall component. The integration of all components required for a single phase also enables a reduction in system interfaces.

[0038] Furthermore, a better thermal connection of the DC link capacitor to a heat sink is possible. The improved cooling connection of the modules has a direct impact on the service life and reliability of the components within them. It offers the possibility of a high degree of cost and energy efficiency.

[0039] Cross-component use leads to further savings. This innovative approach creates several possibilities for scalability and modularization of entire inverter systems. All inverter systems within a vehicle can thus be constructed from the new modules.

[0040] The invention is explained in more detail below using an exemplary embodiment. The figures show: Fig. 1 is a schematic exploded view of the structure of a known three-phase inverter (B6 bridge); Fig. 2 a schematic representation of a module according to the invention with the components necessary for the conversion of a phase in a plan view; Fig. 3 a section along III-III through the Fig. 2 shown module; and Fig. 4 a three-phase inverter (B6 bridge) constructed from three modules.

[0041] Fig. 2 shows a schematic representation of a module 1 according to the invention with the components necessary for converting a phase in a plan view. The module 1 represents an inverter 100 when only one phase needs to be converted. The module 1 comprises a switching unit 11 with a number of power switching elements, a driver unit 21 for controlling the power switching elements of the switching unit 11, a phase intermediate circuit capacitor 31 and a control unit 41 for controlling and monitoring the driver unit 21 (so-called logic) and the switching unit 11. The switching unit 11 comprises, for example, a half-bridge formed from two power switching elements, e.g., MOSFETs, connected in series. The switching unit 11 receives a driver signal TS_P1 from the driver unit 21, which in turn receives a driver signal GDS_P1 from the control unit 41.The phase intermediate circuit capacitor 31 is connected to the driver unit 21 via a line L1_P1 and to the switching unit 11 via a line L2_P1. The phase intermediate circuit capacitor 31 can be designed, for example, as a film capacitor. The intermediate circuit capacitor can also be designed as a ceramic capacitor. In addition, the module can include a current measuring device (not shown in detail), which detects the current flowing on the output side and is evaluated by the control unit 41 to generate the driver signal GDS.

[0042] The switching unit 11, the driver unit 21, the phase intermediate circuit capacitor 31, the control unit 41, and the optional current measuring device (generally: components) are arranged in a common housing 60 on a printed circuit board 62 or another carrier. The electrical interconnection of the components is carried out via the printed circuit board 62, optionally via bonding wires 64 (cf. Fig. 3 shown cross-sectional view along the Fig. 2) or via a conductor pattern provided on and / or in the printed circuit board 62. The printed circuit board 62 can represent the base 61 of the housing or be attached adjacent to the housing base 61. Due to this design, cable lengths can be kept short, which reduces EMC emissions. Furthermore, due to the short L1_P1 and L2_P1 lines, the phase intermediate circuit capacitor can be dimensioned smaller compared to a conventional arrangement, which in turn favors module integration.

[0043] The components can be selectively integrated into a common semiconductor. For example, the switching unit 11 and the driver unit 21 can be integrated into a common semiconductor. Additionally, the phase-link capacitor 31 can also be integrated into the semiconductor. The optional current measuring device, which measures the current flowing on the AC side, can also be integrated into the semiconductor.

[0044] The circuit board 62 is on its back (see Fig. 3) is connected to a plate-shaped heat sink 50, preferably made of metal in this embodiment, through which heat generated during operation of the module is dissipated. Because all components are arranged on the circuit board 62, all components (in particular the phase intermediate circuit capacitor, which determines the service life) are also connected to the heat sink.

[0045] The components arranged in the housing 60 are surrounded by a potting material 63, e.g. soft potting (silicone) or hard potting (epoxy resin), which has flowable properties during processing and hardens, e.g. by a temperature treatment.

[0046] Leading out of the housing 60 are DC and BP terminals for a direct voltage and a direct current, respectively (DC denotes a direct voltage supply terminal, BP a reference potential terminal), an output terminal OUT_P1, to which an alternating voltage or an alternating current generated by the module is applied, as well as a control signal terminal GD for generating the GDS signal by the control unit 41, and one (or more) status signal terminals ST, via which information about a temperature, an error, safety-related status signals, etc., is transmitted. At least the DC, BP, and OUT terminals can be designed as screw terminals (not shown).

[0047] Fig.Figure 4 shows a plan view of a three-phase inverter 100 (a so-called B6 bridge) constructed from three identical modules 1, 2, and 3. Each module 1, 2, and 3 is responsible for providing an AC voltage or AC current signal for a phase P1, P2, and P3. Modules 1, 2, and 3 each comprise the switching unit 11, 12, and 13, the driver unit 21, 22, and 23, the phase intermediate circuit capacitor 31, 32, and 33, the control unit 41, 42, and 43, and the optional current measuring device (not shown). The outputs of modules 1, 2, and 3 are labeled Out_P1, Out_P2, and OUT_P3, where P1, P2, and P3 represent the respective phase. The control signals GD_P1, GD_P2, GD_P3 are generated, for example, by a common control device (not shown in detail). This control device also receives the status signals ST_P1, ST_P2, ST_P3 of modules 1, 2, and 3. The supply potential terminals DC and BP can be connected to the same supply lines of a power source, e.g.a high-voltage battery or a fuel cell, and a reference potential, e.g. the body of a vehicle.

[0048] Modules 1, 2, 3 can be arranged in different locations, contrary to the drawing.

[0049] Several modules can be connected in parallel per phase to either carry a higher current per phase or to reduce the current flowing through a single module.

[0050] The inverter 100 can also be designed with a different number of phases, e.g., 4, 5, or 6, without requiring a redesign of the inverter. The number of phases depends on the AC voltage / current load to be supplied, e.g., an electrical machine. List of reference symbols 1 module 2 Module 3 Module 10 Power switching device 11 Switching unit for first phase 12 Switching unit for second phase 13 Switching unit for third phase 14 Half bridge with two power switching elements 20 Driver device 21 Driver unit for first phase 22 Driver unit for second phase 23 Driver unit for third phase 30 DC link capacitor device 31 Phase intermediate circuit capacitor for first phase 32 phase intermediate circuit capacitor for second phase 33 phase intermediate circuit capacitor for third phase 40 Control unit (logic) 41 Control unit (logic) for first phase 42 Control unit (logic) for second phase 43 Control unit (logic) for third phase 50 heat sinks 60 housings 61 Bottom of the case 62 circuit board 63 Potting material 64 bonding wire 100 inverters P1 first phase P2 second phase P3 third phase DC direct voltage connection GD control signal for driver unit 21, 22, 23 OUT output connector OUT_P1 Output connection of the first phase OUT_P2 Output connection of the second phase OUT_P3 Output terminal of the third phase BP reference potential connection ST_P1 Status signal connection for first phase ST_P2 Status signal connection for second phase ST_P3 Status signal connection for third phase TS_P1 Driver signal to switching unit for first phase TS_P2 Driver signal to switching unit for second phase TS_P3 Driver signal to switching unit for third phase GDS_P1 Driver signal to control unit for first phase GDS_P2 Driver signal to control unit for second phase GDS_P3 Driver signal to control unit for third phase L1_P1 line L1_P2 line L1_P3 line L2_P1 line L2_P2 line L2_P3 line

Claims

[1] Device for converting a direct current into a single-phase or multi-phase alternating current, comprising - a power switching device (10) comprising a switching unit (11, 12, 13) with a number of power switching elements for each phase (P1, P2, P3), - a driver device (20) which, for controlling a respective switching unit (11, 12, 13), comprises a driver unit (21, 22, 23) assigned to the switching unit (11, 12, 13), - an intermediate circuit capacitor device (30), and - a control unit (40) for controlling and monitoring the power switching device (10), wherein the components required for the conversion of a phase (P1, P2, P3) are arranged in a respective module (1, 2, 3). [2] Device according to claim 1, wherein the components required for the conversion of a phase (P1, P2, P3) comprise at least the switching unit (11, 12, 13) with the number of power switching elements, the driver unit (21, 22, 23) assigned to the switching unit (11, 12, 13) for controlling the number of power switching elements of the switching unit (11, 12, 13) and a phase intermediate circuit capacitor (31, 32, 33). [3] Device according to claim 1 or 2, in which the components required for the conversion of a phase (P1, P2, P3) are arranged in a common housing (60). [4] Device according to one of the preceding claims, in which the components required for the conversion of a phase (P1, P2, P3) are arranged and interconnected in a common plane on a carrier or a printed circuit board (63). [5] Device according to one of the preceding claims, in which the components required for the conversion of a phase (P1, P2, P3) are directly connected to a common heat sink (50) in that the components arranged in a common plane have an equal distance from the heat sink (50). [6] Device according to one of the preceding claims, in which the components of the module (1, 2, 3) required for the conversion of a phase (P1, P2, P3) are encapsulated. [7] Device according to one of the preceding claims, in which a phase (P1, P2, P3) is formed by a module (1, 2, 3) or several modules (1, 2, 3) connected in parallel. [8] Device according to one of the preceding claims, in which the modules (1, 2, 3) of different phases (P1, P2, P3) are arranged or can be arranged at spatially separate locations. [9] Device according to one of the preceding claims, in which the modules (1, 2, 3) of one and / or more phases (P1, P2, P3) are designed as mechanically independent units. [10] Use of a device according to one of the preceding claims for controlling an electric drive motor of a vehicle.

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