Double inverter, method for operating the double inverter and vehicle

Abstract

The invention relates to a double inverter (1), comprising a first inverter module (2.1) and a second inverter module (2.2) with respective half-bridges (HB1 to HB6) made of semiconductor switches (S1 to S12) and phase conductors (U, V, W) at center taps of the half-bridges (HB1 to HB6), wherein a load (3) is connected or switchable between a respective phase conductor (U, V, W) of the first inverter module (2.1) and a phase conductor (U, V, W) of the second inverter module (2.2), wherein a control unit (6) for controlling the semiconductor switches (S1 to S12) is further arranged, wherein the inverter modules (2.1, 2.2) have outer conductors which are connected to an energy source (5), wherein the control unit (6) is configured to operate the second inverter module (2.2) in a fundamental frequency clock when the power demand of the load (3) is high, and to operate the first inverter module (2.1) with any clock speed.

Description

The invention relates to a dual inverter according to the preamble of claim 1, a vehicle according to the preamble of claim 8 and a method of operating the dual inverter according to the preamble of claim 9.DE 10 2022 132 370 A1 describes a device which allows a two-stage inverter to switch between a plurality of modes. The apparatus includes a first inverter unit, a second inverter unit, a load connected between the first inverter unit and the second inverter unit, a mode switching unit connected between the load and the second inverter unit, a control unit configured to drive the load in a single-stage inverter mode or a two-stage inverter mode by performing control in which the mode switching unit is turned on or off.When the dual inverter is operated in the mode with the star point open (S1 to S3 active and S4 to S6 active), switching losses occur in both inverters which are proportional to the clock frequency. Above all, the switching losses in the IGBT inverter (S 4 to S 6) are high, since the clock frequency is selected to be high by the operation (DPWM or SVPWM) and the loss energy per switching operation in the case of IGBT is high.It is an object of the invention to provide a novel dual inverter, a novel vehicle and a novel method for operating the dual inverter.The object is achieved according to the invention by a dual inverter having the features of claim 1, by a vehicle having the features of claim 8 and by a method for operating the dual inverter having the features of claim 9.Advantageous embodiments of the invention are the subject matter of the dependent claims.A dual inverter is proposed, comprising a first inverter module and a second inverter module having respective half bridges made of semiconductor switches and phase conductors at center taps of the half bridges, wherein a load is connected or switchable between a respective phase conductor of the first inverter module and a phase conductor of the second inverter module, wherein a control unit for driving the semiconductor switches is furthermore arranged, wherein the inverter modules have outer conductors which are connected to a power source. According to the invention, the control unit is configured to operate the second inverter module at a fundamental frequency clocking and to operate the first inverter module at any desired clocking when the load has high demanded power.In one embodiment, the control unit is configured to operate the first inverter module with a control method with a clock frequency higher than the fundamental frequency clocking when the power of the load is high.In one embodiment, the inverter modules have three phase conductors, wherein a switchable star point former having three switches is arranged between the second inverter module and the load, with which the phase conductors can be connected together to form a star point, wherein the control unit is configured to open the switches of the star point former when the power of the load is high. When the power demanded by the load is low, the control unit may be configured to close the switches of the star point former and not to operate the second inverter module.In one embodiment, the switches of the star point former are designed as semiconductor switches or as mechanical switches, for example relay contacts.In one embodiment, the load is designed as an electric machine.The inverter modules can be designed, for example, as B6 bridges and each have three half bridges made of semiconductor switches.The semiconductor switches can be designed, for example, as MOSFETs or IGBTs.In one embodiment, the semiconductor switches of the first inverter module and / or of the star point former are designed as MOSFETs.In one embodiment, the semiconductor switches of the second inverter module are designed as IGBTs, in particular with a freewheeling diode.According to one aspect of the present invention, a vehicle having an electric drive machine and a battery as a power source is proposed. According to the present invention, the vehicle comprises a dual inverter as described above in which the electric drive machine is connected as a load.According to one aspect of the present invention, a method of operating a dual inverter as described above is provided. According to the invention, at a high requested power and / or rotational speed of the load, the second inverter module is operated at a fundamental frequency clocking and the first inverter module is operated at any desired clocking, in particular with a control method with a higher clock frequency than the fundamental frequency clocking.In one embodiment, the switches of the star point former are also opened when the power of the load is high.The solution according to the invention improves the efficiency during operation with two active inverter modules, for example B6 bridges.Exemplary embodiments of the invention are explained in more detail below with reference to drawings.The following are shown: FIG. 1 shows a schematic circuit diagram of a dual inverter comprising two inverter modules between which a three-phase load is connected, and FIG. 2 is a schematic view of an electrically driven vehicle.Corresponding parts are provided with the same reference numerals in all figures.FIG. 1 is a schematic circuit diagram of a dual inverter 1 comprising two inverter modules 2.1, 2.2, in particular B6 bridges, between which a three-phase load 3, in particular an electric machine 3, having three stator windings is connected. Between the two inverter modules 2 a switchable star point former 4 is provided, with which the phase conductors U, V, W of the load on the side of the second inverter module 2.2 can be connected together to form a star point. The electric machine 3 can be designed as a drive machine of an electrically driven vehicle 10.The inverter modules 2.1, 2.2 each have three half bridges HB1 to HB6 made of semiconductor switches S1 to S12. The star point former 4 has three semiconductor switches S 13 to S 15. Furthermore, a control unit 6 for driving the semiconductor switches S 1 to S 15 is provided.The half bridges HB 1 to HB 6 of the inverter modules 2.1, 2.2 further have outer conductors which are connected to a power source 5, for example a battery 5.The control unit 6 may be configured to drive the first inverter module 2.1 so that a step voltage (e.g., a six-step voltage) is applied to the load 3. Furthermore, the control unit 6 can be configured to switch the star point former 4 on and off. Thus, the load 3 can be operated in a single stage inverter mode or in a two stage inverter mode.For example, it can be provided to operate the load 3 in a two-stage inverter mode (i.e. in a high-power mode) when the star point former 4 is switched off by control by means of the control unit 6, and to operate the load 3 in the single-stage inverter mode (i.e. in a high-efficiency mode) when the star point former 4 is switched on.The star point former 4 comprises three semiconductor switches S 13, S 14 and S 15 for one phase U, V, W respectively. The three semiconductor switches S 13, S 14 and S 15 each have an input terminal which is connected to a line for one of the phases U, V, W respectively. The three semiconductor switches S 13, S 14, and S 15 each further have an output terminal, the output terminals being connected to each other.The first inverter module 2.1 and the second inverter module 2.2 each have three half bridges HB 1 to HB 6, each having a pair of semiconductor switches S 1 to S 12.The semiconductor switches S 1 to S 15 can be embodied as MOSFETs or IGBTs. The semiconductor switches S 1 to S 6, S 13 to S 15 of the first inverter module 2.1 and / or of the star point former 4 can be designed, for example, as MOSFETs. The semiconductor switches S 7 to S 12 of the second inverter module 2.2 can be designed, for example, as IGBTs, in particular with a freewheeling diode.The load 3 designed as a motor can be, for example, an electric drive motor 3 of an electrically driven vehicle 10, in particular of a passenger car, of a commercial vehicle or of a bus.FIG. 2 is a schematic view of an electric powered vehicle 10.During the travel of the vehicle 10 at high power and / or high rotational speed, the control unit 6 can be configured to open the semiconductor switches S 7 to S 9 and to operate the second inverter module 2.2 at a fundamental frequency timing (also referred to as block timing). In this case, the second inverter module 2.2 clocks in proportion to a frequency of a fundamental wave of the electric drive motor 3.The control unit 6 can furthermore be configured to clock the first inverter module 2.1, comprising the half bridges HB1 to HB3, differently therefrom at any desired timing, in particular with a control method with a higher clock frequency. Thus, the full intermediate circuit voltage can continue to be applied per stator winding of the electric drive motor 3 and at the same time the current ripple in the stator windings can be kept low due to the high clock frequency of the half bridges HB 1 to HB 3.The clock frequency in the half bridges HB 4 to HB 6 of the second inverter module 2.2 is reduced. Thus, the power loss in this operating mode is reduced and / or the efficiency of the dual inverter 1 is increased.The method can reduce the NVH (noise vibration roughness) and the torque ripple of the electric drive motor 3, in particular at high loads and / or high torque. By decoupling and distributing the control in fundamental frequency clocking and additional clocking, an improvement in the efficiency in the control in the fundamental frequency range can be achieved, which contributes to the overall improvement in the efficiency.List of reference characters1 Dual inverter 2.1, 2.2 inverter module 3 load, electric machine, electric drive motor 4 star point former 5 energy source, battery 6 control unit 10 vehicle HB 1 to HB 6 half bridge S 1 to S 15 semiconductor switch U, V, W phaseReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2022 132 370 A1

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Claims

Dual inverter (1) comprising a first inverter module (2.1) and a second inverter module (2.2) having respective half bridges (HB1 to HB6) made of semiconductor switches (S1 to S12) and phase conductors (U, V, W) at center taps of the half bridges (HB1 to HB6), wherein a load (3) is connected or switchable between a respective phase conductor (U, V, W) of the first inverter module (2.1) and a phase conductor (U, V, W) of the second inverter module (2.2), wherein a control unit (6) for driving the semiconductor switches (S1 to S12) is furthermore arranged, wherein the inverter modules (2.1, 2.2) have outer conductors, Which are connected to a power source (5), characterized in that the control unit (6) is configured, in the case of high demanded power of the load (3), to operate the second inverter module (2.2) at a fundamental frequency clocking and to operate the first inverter module (2.1) at any desired clocking.Dual inverter (1) according to Claim 1, characterized in that the control unit (6) is configured, when the power demanded by the load (3) is high, to operate the first inverter module (2.1) with a control method with a clock frequency which is higher than the fundamental frequency clocking.Dual inverter (1) according to Claim 1 or 2, characterized in that the inverter modules (2.1, 2.2) have three phase conductors (U, V, W), wherein a switchable star point former (4) having three switches (S7 to S9) is arranged between the second inverter module (2.2) and the load (3), with the aid of which the phase conductors (U, V, W) can be connected together to form a star point, wherein the control unit (6) is configured to open the switches (S7 to S9) when the power of the load (3) is high and demanded.Dual inverter (1) according to Claim 3, characterized in that the switches (S7 to S9) of the star point former (4) are designed as semiconductor switches (S13 to S15).Dual inverter (1) according to one of the preceding claims, characterized in that the load (3) is designed as an electric machine (3).Dual inverter (1) according to one of the preceding claims, characterized in that the semiconductor switches (S1 to S6, S13 to S15) of the first inverter module (2.1) and / or of the star point former (4) are designed as MOSFETs.Dual inverter (1) according to one of the preceding claims, characterized in that the semiconductor switches (S7 to S12) of the second inverter module (2.2) are designed as IGBTs, in particular with a freewheeling diode.Vehicle (10) having an electric drive machine (3) and a battery (5) as energy source (5), characterized bya dual inverter (1) according to one of the preceding claims, in which the electric drive machine (3) is connected as load (3).Method for operating a dual inverter (1) according to one of Claims 1 to 7, characterized in that, at a high demanded power and / or rotational speed of the load (3), the second inverter module (2.2) is operated at a fundamental frequency clocking and the first inverter module (2.1) is operated at any desired clocking, in particular at a control method with a higher clock frequency than the fundamental frequency clocking.Method according to Claim 9, characterized in that, when the power demanded by the load (3) is high, the switches (S7 to S9) of the star point former (4) are opened.

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