Rectifier, motor unit and method for rectification

Abstract

The invention relates to a rectifier (110a) having two DC voltage connections (B +, B-) and a plurality of AC voltage connections (122U, 122V, 122W), the rectifier having a first partial rectifier (110.1 a) and a second partial rectifier (110.2 a), the first partial rectifier having first semiconductor switching elements (TU1H, TV1H, TW1H, TU1L, TV1L, TW1L, 116U, 116V, 116W, 118U, 118W) and being designed as a three-level rectifier or a three-level or higher rectifier, the second partial rectifier having first semiconductor switching elements (TU1H, TV1H, TW1H, TU1L, TV1L, TW1L, 116U, 116V, 116W, 118U the first partial rectifier has a first semiconductor switching element (TU2H), the second partial rectifier has a second semiconductor switching element (TU2H, TV2H, TW2H, TU2L, TV2L, TW2L) and is designed as a two-level rectifier, and wherein the first partial rectifier and the second partial rectifier are each connected or connectable between two DC voltage connections (B +, B-) and a plurality of AC voltage connections (122U, 122V, 122W).

Description

Technical Field

[0001] The invention relates to a rectifier, in particular for an electric machine, an electric machine unit having an electric machine and a rectifier, and a commutation method using such a rectifier. Background Art

[0002] In electrical machines, in particular those used as motors and / or generators, and in particular when used in vehicles, inverters (rectifiers) are used to rectify the alternating current that is generated or to invert the direct current that is present. However, rectifiers can also be used in many other areas, such as electrical devices. Summary of the invention

[0003] According to the invention, a rectifier, a motor unit and a method for commutation are proposed having the features of the independent patent claims. Advantageous developments are the subject matter of the dependent claims and of the following description.

[0004] The present invention relates generally to rectifiers or inverters and in particular to rectifiers or inverters for electric machines and their operation. Within the scope of the present invention, the combination of an electric machine and an associated rectifier is also referred to as an electric machine unit. Typically, the rectifier is in this case mounted or attached to the electric machine. The electric machine unit can here be part of a vehicle and in particular also serve as a traction drive. Examples of electric machines that come into consideration are synchronous machines, synchronous reluctance machines, induction machines, permanent magnet machines, etc.

[0005] For example, a typical electric motor has three or more phases; although the present invention is mainly explained for electric motors with three phases, this also applies to different numbers of phases, such as six, nine, twelve or fifteen. In principle, the electric motor can also have only one or two phases.

[0006] Furthermore, the electric machine has a rotor which can be permanently and / or externally excited.Preferred use is also in so-called high-voltage applications, in which the electric machine is operated at voltages of, for example, 48 V, 60 V or higher.

[0007] As mentioned, rectifiers may also be used in other areas, for example in electrical equipment or when operating electrical equipment, for example if direct current is to be converted into alternating current (eg single-phase or three-phase) or vice versa.

[0008] The rectifier has two DC voltage connections and a plurality of AC voltage connections. When used with or for an electric machine having, for example, three phases, each of the three phases can be connected to a respective one of the three AC voltage connections. For example, if there is only one phase, it can be connected to two AC voltage connections. When used in a vehicle, the DC voltage connection can be connected to, for example, an energy storage device, such as a battery.

[0009] The rectifier usually has a plurality of half bridges, each of which has two semiconductor switching elements, usually a high-side switching element and a low-side switching element. With a center tap, i.e. between two semiconductor switching elements, the plurality of half bridges are usually connected to one of the plurality of AC voltage connections. On the other hand, the DC voltage sides of the plurality of half bridges are usually connected to one another and thus to one of the DC voltage connections. In addition, an intermediate circuit capacitor can be connected between the DC voltage connections. If there are two different voltage levels on the DC voltage side, this can in particular be a so-called two-level rectifier, which are then in particular directly connected to one of the two DC voltage connections respectively and thus correspond to their voltage levels.

[0010] There are also so-called three-level rectifiers, in which a third voltage level is provided on the DC voltage side, which third voltage level is usually located midway between the voltage levels of the two DC voltage connections. The operating noise of a three-level rectifier is lower than that of a two-level rectifier. In particular, at high currents and / or input voltages, the change in current and voltage over time is smaller than with a two-level rectifier. A two-level rectifier requires fewer components.

[0011] It has now proven to be particularly efficient and advantageous to combine a three-level rectifier with a two-level rectifier. Here, the three-level rectifier can be regarded as a first sub-rectifier and the two-level rectifier can be regarded as a second sub-rectifier, both of which are part of the actual rectifier.

[0012] The two partial rectifiers can be connected in parallel with one another and can in particular be designed separately from one another, for example with a separate control unit. This makes the design of the rectifier more flexible. The partial rectifiers can be arranged in different housings, for example, and even at different locations or on different sides of the motor if necessary. Likewise, the two partial rectifiers can also be designed to be integrated with one another, in which case there is also a parallel connection. This makes the design of the rectifier more compact, although any parasitic inductances may have to be taken into account.

[0013] Additionally, one or more intermediate circuit capacitors (depending on the type of three-level rectifier) ​​can be connected between the two DC voltage connections, which capacitors can then be used for both sub-rectifiers. In this context, the rectifier may also be referred to as a hybrid rectifier.

[0014] Instead of a three-level rectifier, a rectifier with more than three levels, for example a four-level or five-level rectifier, can also be used as the first partial rectifier. In this case, there are corresponding additional voltage levels.

[0015] The semiconductor switching elements of the rectifier themselves may comprise, for example, several parallel chips or several parallel discrete semiconductor switches in a power housing in order to achieve the desired maximum current. Commonly used types of semiconductor switching elements are, for example, IGBTs or MOSFETs, such as SiC-MOSFETs or GaN-HEMTs (gallium nitride transistors). For example, SiC-MOSFETs are more efficient due to their lower RDSon resistance at partial load and lower switching losses. On the other hand, IGBTs have a lower resistance than SiC components at currents above the threshold, which is why IGBTs are particularly advantageous over SiC components at high current loads. In addition, IGBTs are generally much cheaper than SiC-MOSFETs. IGBTs are also a more robust component compared to SiC components.

[0016] Generally speaking, different types of semiconductor switching elements have different advantages and disadvantages.

[0017] As has been found, it is particularly efficient and advantageous to use two sub-rectifiers in the rectifier, each sub-rectifier having a plurality of semiconductor switching elements, wherein the semiconductor switching elements of the two sub-rectifiers are particularly different, i.e. in particular of different types or kinds, preferably IGBTs (possibly based on GaN) in one of the sub-rectifiers and MOSFETs in the other of the sub-rectifiers, for example SiC-MOSFETs and / or GaN-HEMTs.

[0018] The first sub-rectifier can have a plurality of, for example, three, first half-bridges, each of which has two first semiconductor switching elements, for example IGBTs. As already mentioned, the first two semiconductor switching elements can also be high-side and low-side semiconductor switching elements. In addition, the first sub-rectifier can have one or more additional first semiconductor switching elements for each first half-bridge in order to be able to generate a third voltage level.

[0019] A distinction can be made between different types of three-level rectifiers. For example, the first sub-rectifier can be designed as a so-called T-type, NPC-type or flying capacitor-type three-level rectifier. However, other types of three-level rectifiers can also be considered, such as active NPC-type, cascaded H-bridge multilevel rectifiers or other types. For a more detailed explanation and illustration of these types of three-level rectifiers, in particular with regard to the wiring and the necessary first semiconductor switching elements, see the figure.

[0020] The second sub-rectifier can also have a plurality of, for example three, half-bridges, each half-bridge having two second semiconductor switching elements, for example MOSFETs. As already mentioned, the second semiconductor switching elements can also be high-side and low-side semiconductor switching elements. The first semiconductor switching element and the second semiconductor switching element are different from each other, in particular of different types.

[0021] This means that two different technologies can be used for the semiconductor switching elements, so that the power of the rectifier at partial load is similar to that of a pure SiC-MOSFET rectifier, for example. Using IGBTs, for example, means that the SiC-SiC-MOSFET does not have to be dimensioned for the peak power, so the cost of the rectifier will be significantly reduced.

[0022] By using IGBT modules / switches, the robustness of the rectifier is significantly increased. By using two half-bridges per phase, the switching pattern of the rectifier can have greater freedom and the size of the intermediate circuit capacitor can be reduced.

[0023] For example, two-level rectifiers are typically used for the 1200 V level, while three-level rectifiers (especially IGBT-based or even GaN-based three-level rectifiers) are typically used for the 650 V level. The hybrid rectifier can then be used to operate an 800 V electronic drive, for example, but the invention is not limited to 800 V.

[0024] The proposed rectifier now also allows different operating modes. In a sub-operating mode, for example, only one of the two sub-rectifiers can be used as a rectifier, while the other can be inactive.

[0025] In a first sub-operating mode, for example in the case of partial or light load up to medium load, or generally in the case of a requested load below a predetermined threshold, for example only the second sub-rectifier is used for rectification, while the first sub-rectifier is not activated. For example a control or regulating unit for the motor controls the motor, for example only via the second sub-rectifier with, for example, a MOSFET.

[0026] In the second sub-operating mode, for example with high load or high torque, but at least with a higher load and / or higher torque than in the first sub-operating mode, or generally with a requested load below a predetermined threshold, for example the first sub-rectifier is used for rectification and is operated, for example, in a PWM circuit, while the second sub-rectifier is not activated. The control or regulation unit controls the motor, for example, only with the first sub-rectifier, for example with an IGBT.

[0027] Furthermore, a hybrid operation mode may be provided, in which the first sub-rectifier and the second sub-rectifier are active and used together.

[0028] Here, for example, in a first hybrid operating mode (which may also be referred to as boost mode), the first sub-rectifier (three-level rectifier, in particular with IGBT) may be switched on or activated first. Then, the second sub-rectifier (two-level rectifier, in particular with MOSFET) is switched on or activated; this allows the current intensity to be increased (since the power rating of the second sub-rectifier is usually lower). The gate voltage and the line impedance should be adjusted so that the current is correctly distributed between the two sub-rectifiers and overload is avoided.

[0029] If the nominal powers of the two sub-rectifiers are almost identical (i.e. within a certain tolerance), a second mixed operating mode can be used. Here, the bridge with lower switching losses can be switched on or activated first, followed by the other bridge; typically, the switching losses in the second sub-rectifier will be lower than the switching losses in the first sub-rectifier (e.g. a three-level rectifier with IGBTs). By distributing the current between the bridges (or sub-rectifiers), the line losses can be significantly reduced without significantly increasing the switching losses. When switching off, the bridge or sub-rectifier with higher switching losses can be switched off first, followed by the bridge or sub-rectifier with lower switching losses.

[0030] Furthermore, for example, a charging or energy transfer mode, in particular an integrated charging mode, can be provided. It is preferred that the charging of the battery (or generally the energy transfer between the energy storage device and the grid) takes place via a second partial rectifier (i.e., in particular with MOSFETs); in this case, the combination of the machine winding and the second partial rectifier can form an AC rectifier, or in the case of charge regulation, they can operate like a DC-DC converter, for example, converting 400 V to an 800 V DC charging system. The second partial rectifier is suitable here due to its better energy efficiency.

[0031] Furthermore, for example, an active short-circuit mode can be provided. In this mode, all low-side or high-side switches can be closed. To do this, first the low-side switches of the first sub-rectifier (e.g. IGBT) are closed (all switches between the center tap and the negative DC voltage connection B-, which are usually two series switches for Fly Cap and NPC, and only one switch for T-type), and then the low-side switches of the second sub-rectifier (with MOSFET). In order to open, the second sub-rectifier can be turned off first and then the first sub-rectifier. In the event of an active short circuit, the same procedure can be used for the high-side switch. This mode is very useful when the machine active short-circuit current is very high in the first few cycles and there is no need to increase the switch size according to this current. Special care should also be taken when distributing the current between the IGBT and SiC switches.

[0032] Further advantages and improvements of the invention are apparent from the description and the accompanying drawings.

[0033] The invention is schematically illustrated in the drawings using exemplary embodiments and is described below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1a Schematically shows a preferred embodiment of a rectifier according to the present invention;

[0035] Figure 1bAnother preferred embodiment of the rectifier according to the present invention is schematically shown;

[0036] Figure 2a , 2b A diagram is shown explaining the present invention.

[0037] Figure 3a Another preferred embodiment of the rectifier according to the present invention is schematically shown;

[0038] Figure 3b Another preferred embodiment of the rectifier according to the present invention is schematically shown;

[0039] Figure 4a Another preferred embodiment of the rectifier according to the present invention is schematically shown;

[0040] Figure 4b Another preferred embodiment of the rectifier according to the present invention is schematically shown;

[0041] Figure 5 A preferred embodiment of the method according to the invention is schematically shown. DETAILED DESCRIPTION

[0042] exist Figure 1a , a motor unit 100a is schematically shown, which has a rectifier 110a and a motor 130. In addition, an energy storage device 150 designed as a battery and a computing unit 140 designed as an MCU are exemplarily shown, wherein the computing unit 140 can be part of the motor unit 100a and can be configured to operate the motor unit.

[0043] The electric machine 130 is connected to a rectifier or inverter 110a. The rectifier 110a is in turn connected to an energy storage device 150 via two intermediate circuit capacitors 120, 121 connected in series. Instead of two intermediate circuit capacitors connected in series, a single (possibly larger) intermediate circuit capacitor can also be used. Via the rectifier 110a, the DC voltage provided by the battery 150 can be converted into an AC voltage for the motor operation of the electric machine 130. Likewise, vice versa, during the generating operation of the electric machine 130, the AC voltage generated there can be converted into a DC voltage via the (thus bidirectional) rectifier 110a in order to charge the battery 150.

[0044] In a preferred embodiment, the rectifier 110a can in particular be a rectifier according to the invention. As already mentioned, the rectifier can be used not only for the operation of the motor, but also for other electrical devices, for example if a DC voltage is to be converted into an AC voltage or vice versa. However, the invention will be explained below using the example of its use for the operation of a motor, for example in a vehicle having a battery in addition to the motor.

[0045] In the case of an electric machine 130, three phases U, V and W are shown here, each comprising a phase winding 132 (labeled only once). It should be noted that the terms "phase" and "phase winding" may also be used synonymously, wherein a "phase winding" usually (only) refers to a winding or coil within a stator. The phase winding 132 is here part of the stator of the electric machine; the rotor of the electric machine is not shown here.

[0046] The rectifier 110a has two sub-rectifiers, a first sub-rectifier 110.1a and a second sub-rectifier 110.2a. In addition, the rectifier 110a has two DC voltage connections B+, B- and a plurality of (for example three) AC voltage connections 122U, 122V, 122W. The rectifier 110a can be (electrically) connected or, as shown here, can be (electrically) connected to an energy storage device 150 via the DC voltage connections B+, B-. Intermediate circuit capacitors 120, 121 are also connected between the DC voltage connections. The rectifier 110a can be (electrically) connected or, as shown here, can be (electrically) connected to the phases of the motor via the AC voltage connections 122U, 122V, 122W.

[0047] The first partial rectifier 110.1a has, for example, three first half-bridges 112.1U, 112.1V, 112.1W. The number of half-bridges corresponds in particular to the number of AC voltage connections. Each of the three first half-bridges has two first semiconductor switching elements in turn: a high-side switching element T U1_H 、T V1_H or T W1_H And the low-side switching element T U1_L 、T V1_L or T W1_L Each first half-bridge has a center tap 124.1U, 124.1V, 124.1W, which is arranged between two first semiconductor switching elements and via which the associated half-bridge is electrically connected or electrically connectable to the respective phase connection.

[0048] The DC voltage sides of the first half bridge are here all connected to one another and (electrically) to one of the two DC voltage connections. The DC voltage side on the high-side switching element side is connected to the positive DC voltage connection B+, and the DC voltage side on the low-side switching element side is connected to the negative DC voltage connection B-.

[0049] Furthermore, the first sub-rectifier 110.1a has, for example, a plurality of further first semiconductor switching elements 116U, 118U, 116V, 118V, 116W, 118W (intermediate switching elements), two of which are respectively connected between the center taps 124.1U, 124.1V, 124.1W corresponding to their markings on the AC voltage side and the center tap 120m between the two intermediate circuit capacitors 120, 121. The first semiconductor switching elements 116U, 118U are connected in series in opposite directions here; in this way, a bidirectional switch is formed. These intermediate switching elements and the high-side and low-side switching elements thus form a T-shape. These switching elements can be combined in the package of each half bridge. The same is true for the first semiconductor switching elements 116V, 118V and 116W, 118W.

[0050] These further first semiconductor switching elements 116U, 118U, 116V, 118V, 116W, 118W may be used to generate a further average voltage level in addition to the voltage level of the DC voltage connection. This means that it is a T-type three-level rectifier.

[0051] Furthermore, the first partial rectifier 110.1a has a control unit 114.1 designed as a gate driver, via which the first semiconductor switching element can be controlled, ie can be opened and closed or switched to be non-conductive and conductive. It should be mentioned that distributed gate drivers can also be used.

[0052] The second partial rectifier 110.2 has, for example, three second half-bridges 112.2U, 112.2V, 112.2W. The number of half-bridges corresponds in particular to the number of AC voltage connections. Each of the three second half-bridges has two second semiconductor switching elements in turn: a high-side switching element T U2_H 、T V2_H or T W2_H And the low-side switching element T U2_L 、T V2_L or T W2_L Each second half-bridge has a center tap 124.2U, 124.2V, 124.2W, which is arranged between two second semiconductor switching elements and via which the associated half-bridge is electrically connected or electrically connectable to the respective phase connection.

[0053] The DC voltage sides of the second half bridge are here all connected to one another and (electrically) to one of the two DC voltage connections. The DC voltage side on the high-side switching element side is connected to the positive DC voltage connection B+, and the DC voltage side on the low-side switching element side is connected to the negative DC voltage connection B-.

[0054] Therefore, the second sub-rectifier is a two-level rectifier.

[0055] Furthermore, the second partial rectifier 110 . 2 a has a control unit 114 . 2 designed as a gate driver, via which the second semiconductor switching element can be controlled, ie can be opened and closed or switched to be non-conductive and conductive.

[0056] The first sub-rectifier 110.1a and the second sub-rectifier 110.2a are each constructed similar to a common three-level power rectifier or a two-level power rectifier, wherein the two are connected in parallel to each other and are each located between two DC voltage connections B+, B- and a plurality of AC voltage connections 122U, 122V, 122W. In addition, the first sub-rectifier 110.1a and the second sub-rectifier 110.2a are designed separately from each other.

[0057] The MCU 140 may, for example, be configured to control the first and second sub-rectifiers 110.1a, 110.2a via their respective gate drivers 114.1, 114.2 (eg via suitable PWM signals).

[0058] There is another difference between the first sub-rectifier 110.1a and the second sub-rectifier 110.2a. The first semiconductor switching element T U1_H 、T V1_H 、T W1_H 、T U1_L 、T V1_L 、T W1_L , 116U, 118U, 116V, 118V, 116W, 118W and the second semiconductor switch element T U2_H 、T V2_H 、T W2_H 、T U2_L 、T V2_L 、T W2_L Different, especially as to their kind or their type.

[0059] The first semiconductor switching element is preferably designed as an IGBT (IGBT stands for "insulated gate bipolar transistor"), and the second semiconductor switching element is designed as a MOSFET (MOSFET stands for "metal oxide semiconductor field effect transistor"), in particular a SiC MOSFET. SiC stands for silicon carbide, and such a SiC MOSFET is a wide bandgap MOSFET.

[0060] In this way, the first sub-rectifier 110.1a and the second sub-rectifier 110.2a are adapted to different situations, and only one of the sub-rectifiers may be used, or both may be used together. In any case, the use of two sub-rectifiers connected in parallel allows for inherent fault tolerance.

[0061] Figure 2a 2 shows a diagram showing typical current-voltage characteristics of an IGBT (curve 201 ) and a SiC-MOSFET (curve 202 ). Here, the current I in A is DS or I CE Relative to the voltage V in V DS or V CE Draw. DS in this index stands for drain-source, which is applicable to SiC-MOSFET. CE stands for collector-emitter, which is applicable to IGBT. V t and I t represent the threshold voltage and threshold current respectively.

[0062] SiC-MOSFETs are more efficient due to their lower RDSon resistance at partial load and lower switching losses. Figure 2a It can be seen that the resistance of the IGBT is higher than the threshold current I t This is lower than the resistance of SiC components, which is why IGBTs are particularly advantageous over SiC components under high current loads, or at least comparable.

[0063] The first semiconductor switching elements or MOSFETs are preferably dimensioned in such a way that they are t The UPSs provide maximum power at currents of 100 Hz and are also designed in particular so that they are cheap and sufficient for partial load operation, ie below a threshold of the requested load (eg 30% to 40% of full load).

[0064] Figure 2b A graph is shown in which the torque M is plotted against the angular velocity ω of the motor. Region 211 indicates the preferred operating range of the second sub-rectifier (i.e., the two-level rectifier) ​​and is intended for lower powers or loads, but with better efficiency. On the other hand, region 212 indicates the preferred operating region of the first sub-rectifier (i.e., the three-level rectifier), which is intended for higher powers or loads, but may also be used for lower efficiency.

[0065] exist Figure 1b , a motor unit 100b is schematically shown, which has a rectifier 110b and a motor 130. In addition, an energy storage device 150 designed as a battery and a computing unit 140 designed as an MCU are exemplarily shown, wherein the computing unit 140 can be part of the motor unit 100b and can be configured to operate the motor unit.

[0066] The motor unit 100b basically corresponds to the Figure 1a The only difference between the motor unit 100a and the motor unit 100a is the rectifier 110b.

[0067] The rectifier 110b basically has the same Figure 1a The rectifier 110b also has a first sub-rectifier 110.1b and a second sub-rectifier 110.2b, which are assigned to the rectifier 110a according to the embodiment of the present invention. Figure 1a The same components as the rectifier 110a.

[0068] However, according to Figure 1a Unlike the rectifier 110a of FIG. 1 , the first sub-rectifier 110.1b and the second sub-rectifier 110.2b are designed to be integrated with each other. Here, the first three half-bridges 112.1U, 112.1V, 112.1W and the three second half-bridges 112.2U, 112.2V, 112.2W are arranged geometrically slightly differently, i.e., the first half-bridges and the second half-bridges are alternated. However, the electrical connections correspond to those according to Figure 1a However, it is also conceivable that the first sub-rectifier 110.1b and the second sub-rectifier 110.2b are arranged very close to each other.

[0069] In addition, according to Figure 1a Unlike the rectifier 110a of FIG. 1 , the rectifier 110b has a control unit 114 designed as a gate driver, by means of which the first and second semiconductor switching elements can be controlled, i.e. can be opened and closed or switched between non-conducting and conducting. This is possible, for example, because the two sub-rectifiers are also integrated into one another and are therefore designed to be compact. In principle, two separate control units designed as gate drivers can also be provided here, as according to Figure 1a As in the rectifier 110a.

[0070] exist Figure 3a , a motor unit 300a is schematically shown, which has a rectifier 110b and a motor 130. In addition, an energy storage device 150 designed as a battery and a computing unit 140 designed as an MCU are exemplarily shown, wherein the computing unit 140 can be part of the motor unit 300a and can be configured to operate the motor unit.

[0071] The electric machine 130 is connected to a rectifier or inverter 310a. The rectifier 310a is in turn connected to the energy storage 150 via two intermediate circuit capacitors 120, 121 connected in series. Via the rectifier 310a, the DC voltage provided by the battery 150 can be converted into an AC voltage for the motor operation of the electric machine 130. Likewise, vice versa, during the generating operation of the electric machine 130, the AC voltage generated there can be converted into a DC voltage via the (thus bidirectional) rectifier 310a in order to charge the battery 150.

[0072] In a preferred embodiment, the rectifier 310a can in particular be a rectifier according to the invention. As already mentioned, the rectifier can be used not only for the operation of the motor, but also for other electrical devices, for example if a DC voltage is to be converted into an AC voltage or vice versa. However, the invention will be explained below using the example of its use for the operation of a motor, for example in a vehicle having a battery in addition to the motor.

[0073] In the case of an electric machine 130, three phases U, V and W are shown here, each comprising a phase winding 132 (labeled only once). It should be noted that the terms "phase" and "phase winding" may also be used synonymously, wherein a "phase winding" usually (only) refers to a winding or coil within a stator. The phase winding 132 is here part of the stator of the electric machine; the rotor of the electric machine is not shown here.

[0074] The rectifier 310a has two sub-rectifiers, a first sub-rectifier 310.1a and a second sub-rectifier 310.2a. In addition, the rectifier 310a has two DC voltage connections B+, B- and a plurality of (for example three) AC voltage connections 122U, 122V, 122W. The rectifier 310a can be (electrically) connected or, as shown here, can be (electrically) connected to the energy storage 150 via the DC voltage connections B+, B-. The intermediate circuit capacitors 120, 121 are also connected between the DC voltage connections. The rectifier 310a can be (electrically) connected or, as shown here, can be (electrically) connected to the phases of the motor via the AC voltage connections 122U, 122V, 122W.

[0075] The first partial rectifier 310.1a has, for example, three first half-bridges 312.1U, 312.1V, 312.1W. The number of half-bridges corresponds in particular to the number of AC voltage connections, although only the first half-bridge 312.1W is shown in detail; however, the other first half-bridges are also designed accordingly.

[0076] The first half bridge 312.1W has four first semiconductor switching elements, the high-side switching element T W1_H , another high-side switch element 318W, a low-side switch element T W1_L and a further low-side switching element 316W. Furthermore, the first half-bridge 312.1W has a center tap 324.1W which is arranged between the two high-side switching elements and the two low-side switching elements and via which the relevant half-bridge is electrically connected or electrically connectable to the respective phase connection.

[0077] The DC voltage sides of the first half bridge are here all connected to one another and (electrically) to one of the two DC voltage connections. The DC voltage side on the high-side switching element side is connected to the positive DC voltage connection B+, and the DC voltage side on the low-side switching element side is connected to the negative DC voltage connection B-.

[0078] Both high-side switching elements or both low-side switching elements can be controlled together in order to connect the basic function of a half bridge, ie to connect the center tap to the positive DC voltage connection B+ or to the negative DC voltage connection B−. Intermediate steps are also conceivable.

[0079] Furthermore, the first semiconductor switching elements 316W, 318W can be used to connect the center tap 324.1W to the center tap 120m between the two intermediate circuit capacitors 120, 121. For this purpose, on the one hand, the two first switching elements T W1_H and 318W, and on the other hand, the two first switching elements T W1_L An electrical connection is provided between and 316W. In addition, two diodes are connected in parallel with the two first semiconductor switch elements 316W, 318W. The same applies to the other first half-bridges, wherein the center tap 120m is connected or connectable to all first half-bridges.

[0080] These further first semiconductor switching elements 316W, 318W can be used to generate a further average voltage level in addition to the voltage level of the direct voltage connection. This means that it is a three-level rectifier of the NPC type.

[0081] Furthermore, the first partial rectifier 310 . 1 a has a control unit 314 . 1 designed as a gate driver, via which the first semiconductor switching element can be controlled, ie can be opened and closed or switched to be non-conductive and conductive.

[0082] The second partial rectifier 310.2 has, for example, three second half-bridges 312.2U, 312.2V, 312.2W. The number of half-bridges corresponds in particular to the number of AC voltage connections. Each of the three second half-bridges has two second semiconductor switching elements in turn: a high-side switching element T U2_H 、T V2_H or T W2_H And the low-side switching element T U2_L 、T V2_L or T W2_L Each second half-bridge has a center tap 124.2U, 124.2V, 124.2W, which is arranged between two second semiconductor switching elements and via which the associated half-bridge is electrically connected or electrically connectable to the respective phase connection.

[0083] The DC voltage sides of the second half bridge are here all connected to one another and (electrically) to one of the two DC voltage connections. The DC voltage side on the high-side switching element side is connected to the positive DC voltage connection B+, and the DC voltage side on the low-side switching element side is connected to the negative DC voltage connection B-.

[0084] Therefore, the second sub-rectifier is a two-level rectifier.

[0085] Furthermore, the second partial rectifier 310 . 2 a has a control unit 314 . 2 designed as a gate driver, via which the second semiconductor switching element can be controlled, ie can be opened and closed or switched to be non-conductive and conductive.

[0086] The first sub-rectifier 310.1a and the second sub-rectifier 310.2a are each constructed similar to a common three-level power rectifier or a two-level power rectifier, wherein the two are connected in parallel to each other and are each located between two DC voltage connections B+, B- and a plurality of AC voltage connections 122U, 122V, 122W. In addition, the first sub-rectifier 310.1a and the second sub-rectifier 310.2a are designed separately from each other.

[0087] The MCU 140 may, for example, be configured to control the first sub-rectifier 310.1a and the second sub-rectifier 310.2a via their respective gate drivers 314.1, 314.2 (eg, via suitable PWM signals).

[0088] There is another difference between the first sub-rectifier 310.1a and the second sub-rectifier 310.2a. The first semiconductor switching element T W1_H 、T W1_L , 316W, 318W and other semiconductor switching elements of the first half bridge and the second semiconductor switching element T U2_H 、T V2_H 、T W2_H 、T U2_L 、T V2_L 、T W2_L Different, especially as to their kind or their type.

[0089] The first semiconductor switching element is preferably designed as an IGBT (IGBT stands for "insulated gate bipolar transistor"), and the second semiconductor switching element is designed as a MOSFET (MOSFET stands for "metal oxide semiconductor field effect transistor"), in particular a SiC MOSFET. SiC stands for silicon carbide, and such a SiC MOSFET is a wide bandgap MOSFET.

[0090] In this way, the first sub-rectifier 310.1a and the second sub-rectifier 310.2a are adapted to different situations, and only one of the sub-rectifiers may be used, or both may be used together. In any case, the use of two sub-rectifiers connected in parallel allows for inherent fault tolerance.

[0091] It should be noted that the aspects and advantages explained with respect to the rectifier 110a also apply.

[0092] exist Figure 3b , a motor unit 300b is schematically shown, which has a rectifier 310b and a motor 130. In addition, an energy storage device 150 designed as a battery and a computing unit 140 designed as an MCU are exemplarily shown, wherein the computing unit 140 can be part of the motor unit 300b and can be configured to operate the motor unit.

[0093] The motor unit 300b basically corresponds to the Figure 3a The only difference between the motor unit 300a and the rectifier 310b is the rectifier 310b.

[0094] The rectifier 310b basically has the same Figure 3a The rectifier 310b also has a first sub-rectifier 310.1b and a second sub-rectifier 310.2b, which are assigned to the rectifier 310a according to the embodiment of the present invention. Figure 3a The same components as the rectifier 310a.

[0095] However, according to Figure 3a Unlike the rectifier 310a of FIG. 1 , the first sub-rectifier 310.1b and the second sub-rectifier 310.2b are designed to be integrated with each other. Here, the first three half-bridges 312.1U, 312.1V, 312.1W and the three second half-bridges 312.2U, 312.2V, 312.2W are arranged slightly differently in geometry, i.e., the first half-bridge and the second half-bridge of each phase are together. However, the electrical connections correspond to those according to Figure 3a However, it is also conceivable that the first sub-rectifier 310.1b and the second sub-rectifier 310.2b are arranged very close to each other.

[0096] In addition, according to Figure 3a Unlike the rectifier 310b of FIG. 1 , the rectifier 310b has a control unit 314 designed as a gate driver, by which the first and second semiconductor switching elements can be controlled, i.e. can be opened and closed or switched between non-conducting and conducting. This is possible, for example, because the two sub-rectifiers are also integrated into each other and are therefore designed to be compact. In principle, two separate control units designed as gate drivers can also be provided here, as according to Figure 3a As in the rectifier 310a.

[0097] exist Figure 4a, a motor unit 400a is schematically shown, which has a rectifier 410a and a motor 130. In addition, an energy storage device 150 designed as a battery and a computing unit 140 designed as an MCU are exemplarily shown, wherein the computing unit 140 can be part of the motor unit 400a and can be configured to operate the motor unit.

[0098] The electric machine 130 is connected to a rectifier or inverter 410a. The rectifier 410a is in turn connected to the energy storage 150 via two intermediate circuit capacitors 120, 121 connected in series. Via the rectifier 410a, the DC voltage provided by the battery 150 can be converted into an AC voltage for the motor operation of the electric machine 130. Likewise, vice versa, during the generating operation of the electric machine 130, the AC voltage generated there can be converted into a DC voltage via the (thus bidirectional) rectifier 410a in order to charge the battery 150.

[0099] In a preferred embodiment, the rectifier 410a can in particular be a rectifier according to the invention. As already mentioned, the rectifier can be used not only for the operation of the motor, but also for other electrical devices, for example if a DC voltage is to be converted into an AC voltage or vice versa. However, the invention will be explained below using the example of its use for the operation of a motor, for example in a vehicle having a battery in addition to the motor.

[0100] In the case of an electric machine 130, three phases U, V and W are shown here, each comprising a phase winding 132 (labeled only once). It should be noted that the terms "phase" and "phase winding" may also be used synonymously, wherein a "phase winding" usually (only) refers to a winding or coil within a stator. The phase winding 132 is here part of the stator of the electric machine; the rotor of the electric machine is not shown here.

[0101] The rectifier 410a has two sub-rectifiers, a first sub-rectifier 410.1a and a second sub-rectifier 410.2a. In addition, the rectifier 410a has two DC voltage connections B+, B- and a plurality of (for example three) AC voltage connections 122U, 122V, 122W. The rectifier 410a can be (electrically) connected or, as shown here, can be (electrically) connected to the energy storage 150 via the DC voltage connections B+, B-. The intermediate circuit capacitors 120, 121 are also connected between the DC voltage connections. The rectifier 410a can be (electrically) connected or, as shown here, can be (electrically) connected to the phases of the motor via the AC voltage connections 122U, 122V, 122W.

[0102] The first partial rectifier 410.1a has, for example, three first half-bridges 412.1U, 412.1V, 412.1W. The number of half-bridges corresponds in particular to the number of AC voltage connections, although only the first half-bridge 412.1W is shown in detail; however, the other first half-bridges are also designed accordingly.

[0103] The first half bridge 412.1W has four first semiconductor switching elements, the high-side switching element T W1_H , another high-side switch element 418W, a low-side switch element T W1_L and a further low-side switching element 416W. Furthermore, the first half-bridge 412.1W has a center tap 424.1W which is arranged between the two high-side switching elements and the two low-side switching elements and via which the relevant half-bridge is electrically connected or electrically connectable to the respective phase connection.

[0104] The DC voltage sides of the first half bridge are here all connected to one another and (electrically) to one of the two DC voltage connections. The DC voltage side on the high-side switching element side is connected to the positive DC voltage connection B+, and the DC voltage side on the low-side switching element side is connected to the negative DC voltage connection B-.

[0105] Both high-side switching elements or both low-side switching elements can be controlled together in order to connect the basic function of a half bridge, ie to connect the center tap to the positive DC voltage connection B+ or to the negative DC voltage connection B−. Intermediate steps are also conceivable.

[0106] In addition, the first semiconductor switching elements 416W, 418W can be used to connect the center tap 424.1W to the capacitor 423. For this purpose, on the one hand, the two first switching elements T W1_H and 318W, and on the other hand, the two first switching elements T W1_L An electrical connection is provided between and 316 W. The same applies to the other first half-bridge; corresponding capacitors are provided there as well (ie for each phase).

[0107] These further first semiconductor switching elements 416W, 418W may be used to generate a further average voltage level in addition to the voltage level of the direct voltage connection. This means that it is a three-level rectifier of the flying capacitor type.

[0108] Furthermore, the first partial rectifier 410 . 1 a has a control unit 414 . 1 designed as a gate driver, via which the first semiconductor switching element can be controlled, ie can be opened and closed or switched to be non-conductive and conductive.

[0109] The second partial rectifier 410.2 has, for example, three second half-bridges 412.2U, 412.2V, 412.2W. The number of half-bridges corresponds in particular to the number of AC voltage connections. Each of the three second half-bridges has two second semiconductor switching elements in turn: a high-side switching element T U2_H 、T V2_H or T W2_H And the low-side switching element T U2_L 、T V2_L or T W2_L Each second half-bridge has a center tap 424.2U, 424.2V, 424.2W, which is arranged between two second semiconductor switching elements and via which the associated half-bridge is electrically connected or electrically connectable to the respective phase connection.

[0110] The DC voltage sides of the second half bridge are here all connected to one another and (electrically) to one of the two DC voltage connections. The DC voltage side on the high-side switching element side is connected to the positive DC voltage connection B+, and the DC voltage side on the low-side switching element side is connected to the negative DC voltage connection B-.

[0111] Therefore, the second sub-rectifier is a two-level rectifier.

[0112] Furthermore, the second partial rectifier 410 . 2 a has a control unit 414 . 2 designed as a gate driver, via which the second semiconductor switching element can be controlled, ie can be opened and closed or switched to be non-conductive and conductive.

[0113] The first sub-rectifier 410.1a and the second sub-rectifier 410.2a are each constructed similar to a common three-level power rectifier or a two-level power rectifier, wherein the two are connected in parallel to each other and are each located between two DC voltage connections B+, B- and a plurality of AC voltage connections 122U, 122V, 122W. In addition, the first sub-rectifier 410.1a and the second sub-rectifier 410.2a are designed separately from each other.

[0114] The MCU 140 may, for example, be configured to control the first and second sub-rectifiers 410.1a, 410.2a via their respective gate drivers 414.1, 414.2 (eg, via suitable PWM signals).

[0115] There is another difference between the first sub-rectifier 410.1a and the second sub-rectifier 410.2a. The first semiconductor switching element T W1_H 、T W1_L , 416W, 418W and other semiconductor switching elements of the first half bridge and the second semiconductor switching element T U2_H 、TV2_H 、T W2_H 、T U2_L 、T V2_L 、T W2_L Different, especially as to their kind or their type.

[0116] The first semiconductor switching element is preferably designed as an IGBT (IGBT stands for "insulated gate bipolar transistor"), and the second semiconductor switching element is designed as a MOSFET (MOSFET stands for "metal oxide semiconductor field effect transistor"), in particular a SiC MOSFET. SiC stands for silicon carbide, and such a SiC MOSFET is a wide bandgap MOSFET.

[0117] In this way, the first sub-rectifier 410.1a and the second sub-rectifier 410.2a are adapted to different situations, and only one of the sub-rectifiers may be used, or both may be used together. In any case, the use of two sub-rectifiers connected in parallel allows for inherent fault tolerance.

[0118] It should be noted that the aspects and advantages explained with respect to the rectifier 110a also apply.

[0119] exist Figure 4b , a motor unit 400b is schematically shown, which has a rectifier 410b and a motor 130. In addition, an energy storage device 150 designed as a battery and a computing unit 140 designed as an MCU are exemplarily shown, wherein the computing unit 140 can be part of the motor unit 400b and can be configured to operate the motor unit.

[0120] The motor unit 400b basically corresponds to the Figure 4a The only difference between the motor unit 400a and the rectifier 410b is the rectifier 410b.

[0121] The rectifier 410b has basically the same Figure 4a The rectifier 410b also has a first sub-rectifier 410.1b and a second sub-rectifier 410.2b, which are assigned to the rectifier 410a according to the embodiment of the present invention. Figure 4a The same components as the rectifier 410a.

[0122] However, according to Figure 4a Unlike the rectifier 410a of FIG. 1 , the first sub-rectifier 410.1b and the second sub-rectifier 410.2b are designed to be integrated with each other. Here, the first three half-bridges 412.1U, 412.1V, 412.1W and the three second half-bridges 412.2U, 412.2V, 412.2W are arranged slightly differently in geometry, i.e., the first half-bridge and the second half-bridge of each phase are together. However, the electrical connections correspond to those according to Figure 4a However, it is also conceivable that the first sub-rectifier 410.1b and the second sub-rectifier 410.2b are arranged very close to each other.

[0123] In addition, according to Figure 4a Unlike the rectifier 410a of FIG. 4 , the rectifier 410b has a control unit 414 designed as a gate driver, by means of which the first and second semiconductor switching elements can be controlled, i.e. can be opened and closed or switched between non-conducting and conducting. This is possible, for example, because the two sub-rectifiers are also integrated into each other and are therefore designed to be compact. In principle, two separate control units designed as gate drivers can also be provided here, as according to Figure 4a As in the rectifier 410a.

[0124] Figure 5 A preferred embodiment of the method according to the invention is roughly schematically shown. Figure 1a , 1b , 3a, 3b, 4a, 4b, and the like. This may also be referred to as the operation of the rectifier.

[0125] In the sub-operation mode, only one of the first sub-rectifier and the second sub-rectifier is used for rectification, and the other of the first sub-rectifier and the second sub-rectifier is not activated. Therefore, in the first sub-operation mode 510, for example, at partial load or light load to medium load, only the second sub-rectifier can be used for rectification, and the first sub-rectifier is not activated. For example, the MCU controls the motor only through the second sub-rectifier with SiC-MOSFET.

[0126] However, in the second sub-operation mode 520, for example at high load or high torque, but at least with a higher load and / or higher torque than in the first sub-operation mode 510, for example the first sub-rectifier is used for switching rectification and, for example, operates in a PWM circuit, while the second sub-rectifier is not activated. For example, the MCU controls the motor only via the first sub-rectifier with an IGBT. For example, a threshold value can be specified for the requested load, which is used to decide whether to use the first sub-operation mode or the second sub-operation mode.

[0127] from Figure 2a As can be seen in the diagrams in , the properties of the semiconductor switching element in question lead to particularly efficient operation in this way, depending on the load or torque.

[0128] However, in a hybrid operating mode, the first sub-rectifier and the second sub-rectifier may be active and used together. Here, for example, in a first hybrid operating mode 530 (which may also be referred to as a boost mode), the first sub-rectifier (three-level rectifier, in particular with IGBT) may be switched on or activated first. Then, the second sub-rectifier (two-level rectifier, in particular with MOSFET) is switched on or activated; this allows the current intensity to be increased (because the power rating of the second sub-rectifier is usually lower). The gate voltage and line impedance should be adjusted so that the current is correctly distributed between the two sub-rectifiers and overload is avoided.

[0129] If the nominal powers of the two sub-rectifiers are almost the same (i.e. within a certain tolerance), a second mixed operating mode 540 can be used. Here, the bridge with lower switching losses can be switched on or activated first, and then the other bridge; usually, the switching losses in the second sub-rectifier will be lower than the switching losses in the first sub-rectifier (e.g. a three-level rectifier with IGBTs). By distributing the current between the bridges (or sub-rectifiers), the line losses can be significantly reduced without significantly increasing the switching losses. When shutting down, the bridge or sub-rectifier with higher switching losses can be shut down first, and then the bridge or sub-rectifier with lower switching losses.

[0130] Furthermore, for example, a charging or energy transfer mode 550, in particular an integrated charging mode, can be provided. It is preferred that the battery is charged (or generally the energy transfer between the energy storage device and the grid) via a second partial rectifier (i.e., in particular with MOSFETs); in this case, the combination of the machine winding and the second partial rectifier can form an AC rectifier, or in the case of charge regulation, they can operate like a DC-DC converter, for example, converting a 400 V to an 800 V DC charging system. The second partial rectifier is suitable here due to its better energy efficiency.

[0131] Furthermore, for example, an active short-circuit mode 560 can be provided. In this mode, all low-side or high-side switches can be closed. To this end, the low-side switches of the first sub-rectifier (e.g. IGBT) are first closed (all switches between the center tap and the negative DC voltage connection B-, which are usually two series switches for Fly Cap and NPC, and only one switch for T-type), and then the low-side switches of the second sub-rectifier (with MOSFET) are closed. In order to open, the second sub-rectifier can be closed first, and then the first sub-rectifier. In the event of an active short circuit, the same process can be used for the high-side switch. This mode is very useful when the machine active short-circuit current is very high in the first few cycles and there is no need to increase the switch size according to this current. Special care should also be taken when distributing the current between the IGBT and SiC switches.

Claims

1. A rectifier (110a, 110b, 310a, 310b, 410a, 410b) having two DC voltage connections (B+, B-) and a plurality of AC voltage connections (122U, 122V, 122W), in, The rectifier comprises a first sub-rectifier (110.1a, 110.1b, 310.1a, 310.1b, 410.1a, 410.1b) and a second sub-rectifier (110.2a, 110.2b, 310.2a, 310.2b, 410.2a, 410.2b), The first sub-rectifier has a first semiconductor switching element (T U1_H , T V1_H , T W1_H , T U1_L , T V1_L , T W1_L , 116U, 116V, 116W, 118U, 118W, 316W, 318W, 416W, 418W) and designed as a three-level rectifier or a rectifier above three levels, The second sub-rectifier has a second semiconductor switching element (T U2_H , T V2_H , T W2_H , T U2_L , T V2_L , T W2_L ) and is designed as a two-level rectifier, and The first sub-rectifier and the second sub-rectifier are respectively connected or connectable between two DC voltage connection parts (B+, B-) and a plurality of AC voltage connection parts (122U, 122V, 122W).

2. The rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to claim 1, wherein: The first semiconductor switching element and the second semiconductor switching element are different from one another, in particular of different types.

3. The rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to claim 2, wherein: The first semiconductor switch element (T U1_H , T V1_H , T W1_H , T U1_L , T V1_L , T W1_L ) has IGBT or is IGBT.

4. The rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to claim 2 or 3, wherein: The second semiconductor switch element (T U2_H , T V2_H , T W2_H , T U2_L , T V2_L , T W2_L ) has or is a MOSFET, in particular a SiC-MOSFET and / or a GaN-HEMT.

5. The rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to any one of the preceding claims, wherein The first sub-rectifier is designed as a three-level rectifier of T-type, NPC type or flying capacitor type.

6. The rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to any one of the preceding claims, wherein: The second sub-rectifier has a plurality of second half-bridges (112.2U, 112.2V, 112.2W), each of which has a plurality of second semiconductor switching elements (T U2_H , T V2_H , T W2_H , T U2_L , T V2_L , T W2_L ) in two.

7. The rectifier (110a, 310a, 410a) according to any one of the preceding claims, wherein: The first sub-rectifier (110.1a, 310.1a) and the second sub-rectifier (110.2a, 310.2a) are connected in parallel to each other and are designed separately from each other.

8. The rectifier (110b, 310b, 410b) according to any one of claims 1 to 6, wherein: The first sub-rectifier and the second sub-rectifier are integrated with each other.

9. A motor unit (100a, 100b, 300a, 300b, 400a, 400b), comprising a motor (130) having one or more phases and a rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to any one of the preceding claims, wherein: One or more phases are respectively connected to a respective one of the plurality of alternating voltage connections.

10. The motor unit (100a, 100b, 300a, 300b, 400a, 400b) according to claim 9, the motor unit being designed as a traction drive of a vehicle.

11. A method for rectifying by using the rectifier (110a, 110b, 310a, 310b, 410a, 410b) according to any one of claims 1 to 8 or the motor unit (100a, 100b, 300a, 300b, 400a, 400b) according to claim 9 or 10.

12. The method according to claim 11, wherein: In the sub-operation mode (510, 520), only one of the first sub-rectifier and the second sub-rectifier is used for rectification, and wherein the other of the first sub-rectifier and the second sub-rectifier is not activated.

13. The method according to claim 12, wherein: In the first sub-operation mode (510), the second sub-rectifier is used for rectification when the required load is below a predetermined threshold, and / or wherein in the second sub-operation mode (520), the first sub-rectifier is used for rectification when the required load is above a predetermined threshold.

14. The method according to any one of claims 11 to 13, wherein: In the hybrid operation mode (530, 540), the first sub-rectifier and the second sub-rectifier are used for rectification.

15. The method according to claim 14, wherein: In the first hybrid operation mode (530), the first sub-rectifier is activated first, and then the second sub-rectifier is activated.

16. The method according to claim 14 or 15, wherein: In the second hybrid operation mode (540), and if the first sub-rectifier and the second sub-rectifier have the same nominal power within a predetermined tolerance, the one of the first sub-rectifier and the second sub-rectifier having the lower switching loss is activated first, and then the other of the first sub-rectifier and the second sub-rectifier is activated.

17. The method according to any one of claims 11 to 16, wherein: In the energy transmission mode (550), energy transmission between the energy storage device and the power grid is performed via the rectifier, and the second sub-rectifier is used for rectification.

18. The method according to any one of claims 11 to 17, wherein: In the active short-circuit mode (560), all low-side or high-side semiconductor switching elements are closed, wherein the low-side or high-side semiconductor switching elements of the first sub-rectifier are closed first and then the low-side or high-side semiconductor switching elements of the second sub-rectifier are closed.

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