WO2015128101A1

WO2015128101A1 - Electric drive system

Info

Publication number: WO2015128101A1
Application number: PCT/EP2015/050197
Authority: WO
Inventors: Carsten Schroeder; Martin Braun; Stefan Butzmann
Original assignee: Robert Bosch Gmbh
Priority date: 2014-02-27
Filing date: 2015-01-08
Publication date: 2015-09-03
Also published as: DE102014203568A1

Abstract

The invention relates to an electric drive system, having a 3⋅n-phase electric machine, n>1, which has at least two three-phase winding sections, a first power inverter whose output terminals are connected to the phase terminals of a first of the three-phase winding sections of the electric machine, a second power inverter which is connected in parallel with the first power inverter whose output terminals are connected to the phase terminals of a second of the three-phase winding sections of the electric machine, a first DC voltage source which feeds input terminals of the first power inverter with a DC voltage, and a second DC voltage source which feeds input terminals of the second power inverter with a DC voltage.

Description

Description title

Electric drive system

The invention relates to an electric drive system, in particular for an electrically operated vehicle such as an electric car or a hybrid vehicle.

State of the art

As shown by way of example in FIG. 1, in an electric drive system 100, the feeding of multi-phase current into an electric machine 101 is usually carried out by an inverter 102 in the form of a

Pulse-controlled inverter. For this purpose, a DC voltage provided by a DC voltage intermediate circuit 103 can be converted into a multi-phase AC voltage, for example a three-phase AC voltage. The DC intermediate circuit 103 is fed by a string 104 of serially connected battery modules 105 or any DC voltage sources.

In order to meet the power and energy requirements of a given application, multiple battery modules or battery cells are often connected in series in an energy storage system. However, when high power is required on the electric machine, it may become necessary to take measures in the implementation of the electric drive system 100 that will meet the increased performance requirements.

For example, it may be possible to connect several strings 104 of serially connected battery modules 105 in parallel. However, this can lead to undesirable balance currents between the strands 104. In addition, it may also be necessary to increase the current carrying capacity of the components of the inverter 102 and the electric machine 101. Alternatively, the DC link voltage could be raised. In any case, extensive adaptation developments and changes in the implementation of the electric drive system are required, which in turn lead to increased implementation effort and costs.

The publication US 2007/0070667 Al discloses a drive system for an electrically operated vehicle with several parallel connected

Inverters that supply a multiphase motor with AC voltage. Document DE 10 2011 085 731 A1 discloses an electric drive system for a six-phase motor with two inverters connected in parallel. The document DE 10 2008 008 978 AI discloses modular drive converters. Document DE 10 2010 001 250 A1 discloses an electric drive system for an electric machine with two

Phase systems powered by separate inverters.

Disclosure of the invention

According to a first aspect, the present invention provides an electric drive system with a 3 * n-phase electric machine, n> l, which has at least two three-phase winding strands, a first

Inverter whose output terminals are connected to the phase terminals of a first of the three-phase winding phases of the electric machine, a second parallel to the first inverter switched

Inverter whose output terminals are connected to the phase terminals of a second of the three-phase winding phases of the electric machine, a first DC voltage source, which

Input terminals of the first inverter with a DC voltage, and a second DC voltage source, which feeds input terminals of the second inverter with a DC voltage.

Advantages of the invention One idea of the present invention is to control electrical machines by means of standardized power assemblies, such as inverters, for example in B6 topology. Such inverters are available as standardized module types, which are inexpensive to procure and implement by economies of scale. The modularization of the power modules advantageously increases the efficiency of the electric drive system without the implementation of the electrical machine or of the individual power units per se being more expensive or expensive. In addition, simple mechanical connection means can be provided for all power modules, by means of which the system modules can be interconnected. Furthermore, a central control device, for example on a central control board, can be provided equally for all power assemblies.

According to one embodiment of the electrical according to the invention

Drive system, the first and the second inverter each having a three-phase self-commutated inverter comprising three balanced half-bridges of two power semiconductor switches in series circuit.

According to a further embodiment of the electric drive system according to the invention, the switching elements may each comprise power semiconductor switches, preferably MOSFET switches or IGBT switches. These switches are particularly durable and reliable to control.

According to a further embodiment of the electric drive system according to the invention, the drive system may further comprise a control device, which is designed to control the power semiconductor switches of the first inverter and the second inverter, wherein the control device is arranged on a central control board for the first inverter and the second inverter.

According to a further embodiment of the electric drive system according to the invention, the drive system may further comprise a first

DC intermediate circuit, which between the input terminals of the coupled first inverter, and a second

Have DC voltage intermediate circuit, which between the

Input terminals of the second inverter is coupled.

According to a further embodiment of the electric drive system according to the invention, the first DC voltage source and the second

DC voltage source in each case a plurality of series-connected

Have battery modules.

According to a further embodiment of the electric drive system according to the invention, the reference potentials of the first and second

DC voltage source to be coupled via an electrically conductive connection.

Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the attached

Drawings.

Brief description of the drawings In the drawings:

Fig. 1 is a schematic representation of an exemplary conventional electric drive system; and

Fig. 2 is a schematic representation of an electric drive system according to an embodiment of the present invention.

Like reference numerals generally designate like or equivalent components. The schematic shown in the figures

Representations are only exemplary in nature, for the sake of

Clarity idealized are shown. It is understood that the

illustrated components are merely illustrative of principles and functional aspects of the present invention. FIG. 2 shows a schematic representation of an electric drive system 10 with a six-phase electrical machine 6, which may be, for example, a switched reluctance machine or a rotating field machine. The electric machine 6 has two three-phase winding strands 6a and 6b which are coupled together in their neutral point or in each case in

Triangle circuit can be executed. The electric drive system 10 also has an inverter system of at least one first

Inverter 3a and a second inverter 3b. In this case, the first inverter 3a feeds the first three-phase winding branch 6a of the electric machine 6 at its output terminals. The second inverter 3b feeds the second three-phase winding branch 6b of the electrical machine 6 at its output terminals.

The inverters 3a and 3b each have a B6 full-bridge topology, that is, each of the inverters has a three-phase self-commutated inverter, the three symmetrical half-bridges of two power semiconductor switches Hl and H2, H3 and H4 or H5 and H6 in

Series connection includes. The power semiconductor switches may be, for example, MOSFET switches or IGBT switches. However, it is also possible to use any other type of switching elements as switches Hl to H6 and to switch parallel to each switching element Hl to H6 a freewheeling diode. At a center tap of a first half-bridge of the inverters 3a and 3b, respectively, a first of the phases of the three-phase winding strands 6a and 6b is coupled, at a middle tap of a second half-bridge of the inverters 3a or 3b a second of the phases of the three-phase winding strands 6a and 6b, respectively. and at a center tap of a third half-bridge of the inverters 3a and 3b, a third of the phases of the three-phase winding strands 6a and 6b, respectively.

The first inverter 3a and the second inverter 3b can either as a separate inverter units or in a

be implemented common inverter module. In the latter case, a single inverter module with six symmetrical half-bridges

be provided that in a similar manner with the electric

Machine 6 is coupled. For controlling the power semiconductor switches H1 to H6, a control device (not explicitly shown) may be used which, for example, on a common control board

can be implemented.

The inverters 3a and 3b may each consist of a

DC intermediate circuit 2a and 2b are fed, which in turn is supplied by a DC voltage source la or lb, for example, a traction battery of an electric vehicle with electrical DC voltage. The reference potentials of the DC voltage sources la and lb can be coupled via an electrically conductive connection. The

DC voltage sources la and lb can, for example, a

Series connection of battery modules 5, whose number is shown in Fig. 2 only by way of example with 3 - any other number of battery modules 5 may also be possible. Furthermore, it is clear that the number of phases of the inverters 3a and 3b may differ from the exemplary number of three shown in FIG. 2, depending on the required number of phases of the

Winding strands 6a and 6b of the electric machine 6, whose phase number can take any number. It is also possible to connect more than two inverters 3a and 3b in parallel, in particular if the electric machine 6 has more than two polyphase winding strands 6a and 6b. For this purpose, each of the inverters one of the multi-phase

Winding strands are assigned and electrically connected with selbigem.

Due to the parallel connection of basically similar

DC sources la and lb can improve the performance of the electric drive system 10 while maintaining the desired

Output voltage levels are significantly increased. Through the use of several principally similar inverters 3a and 3b, the phase currents through each of the inverters 3a and 3b and the

Voltage load of each associated DC voltage intermediate circuits 2a and 2b are kept the same, even if the number of inverters is greater than one. As a result, the current carrying capacity of the

Power semiconductor switch Hl to H6 of the inverters 3a and 3b compared to conventional power semiconductor switches Hl to H6 are not increased. In addition, can be created by the modularization of a redundant system in which in case of failure of a single DC voltage source la and lb or a single inverter 3a or 3b may be an emergency operation function with limited performance can be established. For this purpose, the defective or defective part of the inverter system can be deactivated, and the electric machine 6 is at least temporarily by the rest

Inverter parts supplied with reduced power.

In the drive system 10 shown, the electric machine 6, for example, a synchronous or asynchronous machine, a

Reluctance machine or a brushless DC motor (BLDC, "brushless DC motor"). It may also be possible, the electric

To use drive system 10 of FIG. 2 in stationary systems,

For example, in power plants, in electrical power plants such as Windkraftan, photovoltaic or

Combined Heat and Power plants, in energy storage facilities such as compressed air storage power plants, battery storage power plants,

Flywheel accumulators, pumped storage or similar systems. Another possible use of the electric drive system 10 of FIG. 2 are

Passenger or goods transport vehicles, which are designed for locomotion on or under the water, for example, ships, motor boats or the like.

Claims

claims

1. Electric drive system (10), with:

a 3-n-phase electric machine (6), n> l, which has at least two three-phase winding strands (6a, 6b);

a first inverter (3a), whose output terminals with the

Phase terminals of a first of the three-phase winding strands (6a, 6b) of the electric machine (6) are connected;

a second parallel to the first inverter (3a) connected

Inverter (3b) whose output terminals are connected to the phase terminals of a second one of the three-phase phase windings (6a, 6b) of the electrical machine (6);

a first DC voltage source (1a) which supplies input terminals of the first inverter (3a) with a DC voltage; and

a second DC voltage source (Ib), which feeds input terminals of the second inverter (3b) with a DC voltage.

An electric drive system (10) according to claim 1, wherein said first and second inverters (3a, 3b) each comprise a three-phase self-commutated inverter comprising three balanced half bridges each of two power semiconductor switches (H1, H2; H3, H4; H5, H6 ) in series connection.

3. Electric drive system (10) according to claim 2, wherein the

Power semiconductor switches (Hl, H2, H3, H4, H5, H6) have MOSFET switches or IGBT switches.

The electric drive system (10) of any one of claims 2 to 3, further comprising:

a control device, which is designed to, the

Power semiconductor switches (H1, H2, H3, H4, H5, H6) of the first inverter (3a) and the second inverter (3b), wherein the control means is arranged on a central control board for the first inverter (3a) and the second inverter (3b).

5. An electric drive system (10) according to any one of claims 1 to 4, further comprising:

a first DC link (2a) coupled between the input terminals of the first inverter (3a); and a second DC link (2b) coupled between the input terminals of the second inverter (3b).

6. Electric drive system (10) according to one of claims 1 to 5, wherein the first DC voltage source (la) and the second

DC voltage source (lb) each having a plurality of series-connected battery modules (5).

7. Electrical drive system (10) according to any one of claims 1 to 6, wherein the reference potentials of the first and second DC voltage source (la, lb) are coupled via an electrically conductive connection.