EP2673877A2

EP2673877A2 - System comprising an electrically excited machine

Info

Publication number: EP2673877A2
Application number: EP11805062.4A
Authority: EP
Inventors: Peter Feuerstack; Erik Weissenborn; Martin Kessler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-02-10
Filing date: 2011-12-29
Publication date: 2013-12-18
Also published as: US20130320888A1; DE102011003940A1; WO2012107150A3; WO2012107150A2; CN103354975B; CN103354975A; US9425723B2

Abstract

The invention relates to a system comprising an n-phase separately excited electrical machine (1), with n>=1, a controllable first energy store (2) which has n parallel energy supply branches (2a, 2b, 2c), every energy supply branch (2a, 2b, 2c) comprising a first connection (3a, 3b, 3c) that is connected to a respective phase connection (1a, 1b, 1c) of the electrical machine (1), and a second connection (4a, 4b, 4c) that is connected to a common reference bus (9), said reference bus (9) being connected to the neutral point (10) of the electrical machine (1) via a field winding (11) of the electrical machine (1).

Description

title

System with an electrically excited machine

The invention relates to a system with an electrically excited machine, which is controlled by means of a controllable first energy storage and supplied with electrical energy, and a method for operating the system according to the invention.

State of the art

It is becoming apparent that in the future both stationary applications, e.g.

Wind turbines, as well as in vehicles such as hybrid or electric vehicles, increasingly electronic systems are used that combine new energy storage technologies with electric drive technology. In conventional applications, as shown for example in Fig. 1, an electric machine 101, e.g. when

Rotary field machine is running, controlled by a converter in the form of a pulse inverter 102. Characteristic of such systems is a so-called

DC intermediate circuit 103, via which an energy storage 104, usually a traction battery, is connected to the DC voltage side of the pulse-controlled inverter 102. In order to meet the requirements for performance and energy given for a particular application, several battery cells 105 are connected in series. Since the power provided by such an energy storage 104 must flow through all the battery cells 105 and a battery cell 105 can only conduct a limited current, battery cells are often additionally connected in parallel in order to increase the maximum current. The series connection of several battery cells in addition to a high total voltage involves the problem that the entire energy storage fails if a single battery cell fails, because then no battery power can flow. Such a failure of the energy storage can lead to a failure of the entire system. In a vehicle, failure of the traction battery can result in the vehicle "stalling". For other applications, such as the rotor blade adjustment of

Wind turbines, it may in unfavorable conditions, such as strong Wnd, even come to safety-threatening situations. Therefore, it is always high Reliability of the energy storage, where "reliability" is the ability of a system to work for a given time error-free.

In the earlier applications DE 102010027857.2 and DE 102010027861.0 batteries are described with several battery module strings, which directly to an electrical

Machine can be connected. The battery module strands in this case have a plurality of battery modules connected in series, each battery module having at least one battery cell and an associated controllable coupling unit, which allows depending on control signals to interrupt the respective battery module strand or to bridge the respectively associated at least one battery cell or each assigned to switch at least one battery cell in the respective battery module string. By suitable activation of the coupling units, e.g. with the help of pulse width modulation, suitable phase signals for controlling the electrical machine can be provided, so that on a separate

Pulse inverter can be dispensed with. The required for controlling the electrical machine pulse inverter is so to speak integrated into the battery. To the

For purposes of the disclosure, these two earlier applications are fully incorporated into the present application. In contrast to conventional systems, there is no constant DC voltage at the output of the battery system, which can be used, for example, to feed a battery

Exciter winding a foreign-excited electric machine can be used.

Disclosure of the invention

According to one embodiment, the present invention provides a system having an n-phase, externally excited electrical machine, with n> 1, a controllable first energy store, which has n parallel power supply branches, wherein each of the power supply branches has a first connection, which in each case has one

Phase connection of the electrical machine is connected, and a second terminal, which is respectively connected to a common reference rail, has, wherein the reference rail is connected via a field winding of the electric machine with the neutral point of the electric machine. The present invention, according to a further embodiment, provides a method of operating a system having an n-phase, externally excited electrical machine, with n> 1, and a controllable first energy store, which is n parallel

Has energy supply branches. The method comprises the steps of Providing a DC voltage portion to each of the power supply branches, feeding the DC voltage portion into the phase terminals of the N-phase electric machine, and feeding a field winding of the electric power

Machine with the DC voltage component fed into the phase connections for generating a field of excitation in the electrical machine.

Advantages of the invention

An idea of the present invention is to feed a field winding of a foreign-excited electric machine via the star point of the electric machine.

As a result, an interconnection of the field winding with the neutral point can take place within the electrical machine, so that an external motor connection in the

Inventive system is no longer necessary. All necessary for the operation of the electrical machine components are already in the

Energy storage module available, so that no other components for feeding the excitation winding are necessary.

A further idea of the present invention is to change the potential at the star point of an electrical machine by simply controlling energy storage modules in the energy supply branches in order to vary the current through the excitation winding of the electrical machine and thus be able to change the excitation of the machine. The drive methods can be integrated in a simple manner into existing drive concepts for driving the stator windings of the electric machine. According to an advantageous embodiment, a system in each of the n parallel power supply branches may have at least two energy storage modules connected in series, which each comprise at least one electrical energy storage cell with an associated controllable coupling unit. The coupling units can be configured in full-bridge circuit or half-bridge circuit, depending on whether a reversal of the current direction in the power supply branches is desired or not. A part of the series-connected energy storage modules can be controlled via the coupling units so that in each of the power supply branches to the output power supply voltage, a DC component is applied. This DC component can then be fed via the phase terminals and the star point of the electric machine in the excitation winding. This allows the potential in the star point to be varied in several stages. By appropriate clocking of at least one energy storage module, the potential at the star point can also be adjusted continuously. Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

Brief description of the drawings

Show it:

1 is a schematic representation of a system with electrical machine of the prior art,

Fig. 2 is a schematic representation of a system with an electric

Machine and a controllable energy storage,

Fig. 3 is a schematic representation of a system with an electrical

Machine and a controllable energy storage according to a

Embodiment of the present invention, and

Fig. 4 is a schematic representation of a system with an electrical

Machine and a controllable energy storage according to another embodiment of the present invention.

Fig. 2 shows a system with an electric machine 1 and a controllable

Energy storage 2. The electric machine 1 is exemplified as a three-phase electric machine 1, which is powered by a controllable first energy storage 2 with energy. The controllable first energy storage 2 comprises three

Power supply branches 2a, 2b, 2c, which on the one hand with a reference potential 9 (reference rail), which leads in the illustrated embodiments with respect to phases U, V, W of the electric machine 1 a mean potential, via terminals 4a, 4b, 4c, and on the other are each connected to the individual phases U, V, W of the electric machine 1. In this case, a connection 3a of a first power supply branch 2a with a first phase connection 1a of the electric machine 1, a connection 3b of a second energy supply branch 2b with a second phase connection 1b of the electrical machine 1, and a connection 3c of a third energy supply branch 2c with a third phase connection 1 c of the electric machine 1 is coupled. Each of the power supply branches 2a, 2b, 2c has in series

Energy storage modules 5a, 6a and 5b, 6b and 5c, 6c. Exemplary is the Number of energy storage modules per power supply branch 2a, 2b, 2c in Fig. 2 two, but any other number of energy storage modules is also possible.

The energy storage modules 5a, 5b, 5c, 6a, 6b, 6c in turn each comprise a plurality of series-connected electrical energy storage cells in one

Energy storage cell device 7. In this case, the number of energy storage cells in an energy storage cell device 7 in Fig. 2 by way of example two, but any other number of energy storage cells is also possible. The energy storage modules 5a, 5b, 5c, 6a, 6b, 6c furthermore each include a coupling unit 8, which is assigned to the energy storage cells 7 of the respective energy storage module 5a, 5b, 5c, 6a, 6b, 6c. For reasons of clarity, the coupling units and the energy storage cell devices are only in the energy storage module 5c with

Provided with reference numerals. However, it is understood that the energy storage modules 5a, 5b, 6a, 6b, 6c may include similar coupling units and energy storage cell devices.

In the illustrated embodiments, the coupling units 8 are each formed by four controllable switching elements, which are connected in the form of a full bridge. The switching elements may be used as power semiconductor switches, e.g. in the form of IGBTs (Insulated Gate Bipolar Transistors) or as MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors). However, it may also be possible to

Coupling units 8 each as a half-bridge circuit with only two in each case

Form switching elements. Half-bridge circuits have the advantage of having lower power losses due to the lower number of switching elements, but have the disadvantage that the voltage at the output terminals 3a, 3c of the

Power supply branches can not be reversed.

In the exemplary case of a full bridge circuit allow the

Coupling units 8, the respective power supply branch 2a, 2b, 2c

Open all switching elements of a coupling unit 8 to interrupt. alternative

can the energy storage cells 7 by closing two of the

Switching elements of a coupling unit 8 either bridged or in the respective

Power supply branch 2a, 2b, 2c are switched. The total output voltages of the power supply branches 2a, 2b, 2c

be by the respective switching state of the controllable switching elements of

Coupling units 8 determined and can be set in stages. The gradation results in dependence on the voltage of the individual

Energy storage modules 5a, 5b, 5c, 6a, 6b, 6c.

The coupling units 8 thus allow the phases U, V, W of the electrical

Machine 1 either against a high reference potential or a low

Reference potential to switch and can therefore also the function of a

meet known inverter. Thus, the power and operating mode of the electric machine 1 can be controlled by the controllable first energy store 2 with suitable control of the coupling units 8. The controllable first energy storage 2 thus fulfills a dual function insofar as it on the one hand the electrical power supply on the other hand but also the control of

Electric machine 1 is used.

The electric machine 1 has stator windings, which in a known manner in

Star connection are interconnected. The electric machine 1 is in the illustrated embodiments as a three-phase three-phase machine

executed, but may also have fewer or more than three phases. Accordingly, the number of phases of the electric machine depends on

Number of power supply branches 2a, 2b, 2c in the controllable first

Energy storage 2.

3 shows a schematic representation of a system with an electric machine 1 and a controllable energy store 2 according to an embodiment of the present invention. The system shown in Fig. 3 differs from the system shown in Fig. 2 only in that at a neutral point 10 of the electric machine 1, a field winding 1 1 is connected, which in turn via the

Reference rail 9 respectively with the terminals 4a, 4b, 4c of the controllable

Energy storage 2 is connected. In conventional control of the controllable first energy storage 2 is located at the star point 10 to an average potential. However, this potential can be shifted by the fact that in each case the energy storage cells 7 of one or more energy storage modules 5a, 5b, 5c, 6a, 6b, 6c of each energy supply branch 2a, 2b, 2c by appropriate control of the associated coupling units 8 permanently or clocked with positive or negative Poling in the respective

Power supply branch 2a, 2b, 2c are switched. The voltages at the power supply branches 2a, 2b, 2c are thus each increased to a value or which is above or below a voltage value currently required for the power supply of the electric machine 1.

About this increase or decrease of the voltages to the

Power supply branches 2a, 2b, 2c can be a DC component over the

Phase terminals 1a, 1 b, 1c are fed into the star point 10, so that the potential in the star point 10 is variable. Via the feedback of the star point 10 with the reference rail 9 of the controllable energy storage device 2, a variable current can be conducted through the exciter winding 11, so that a variable exciter field in the electric machine 1 can be generated. About this interconnection, which can be done within the electrical machine, eliminating the need for a separate motor connection to power the excitation winding 11th

In the present embodiment of FIG. 3 with the full bridge circuit of the coupling units 8 can via a corresponding control of

Energy storage modules 5a, 5b, 5c, 6a, 6b, 6c, a reversal of the current through the excitation winding 1 1 can be achieved. However, it is also possible, for example, for one of the energy storage modules 5a, 5b, 5c, 6a, 6b, 6c with coupling units 8 in FIG

To realize half-bridge circuit. If these energy storage modules for

Provision of the DC voltage component at the phase terminals 1a, 1 b, 1 c are used, although it is no longer possible to realize a reversal of the current through the field winding, but sink by the smaller number of necessary switching elements in a half-bridge circuit of the coupling units 8

Power losses at the switching elements of these energy storage modules.

4 shows a schematic representation of a system with an electrical machine and a controllable energy store according to a further embodiment of the present invention. The system of Figure 4 differs from the system of Figure 3 essentially in that each of the power supply branches 2a, 2b, 2c has only one energy storage module. Furthermore, in the

Energy storage modules of the power supply branches 2a, 2b, 2c coupling units and energy storage cells 7 are provided which are associated with the respective energy storage modules. By way of example, in the power supply branch 2a, the

Energy storage module 5a with coupling units 8a and 8b and a

Energy storage cell device 7 shown. In Fig. 4 is the

Energy storage cell device 7 via a half-bridge circuit with the terminals 3a and 4a connected and / or bridged. For this purpose there is a coupling unit 8a in a branch parallel to the energy storage cell device 7 and a coupling unit 8b in series in the branch of the energy storage cell device 7. As further shown in Fig. 4, it is in principle possible to design each of the energy storage modules with different coupling units, for example with coupling units in half-bridge circuit and coupling units in full bridge circuit. However, it is of course also possible, all energy storage modules in Fig. 4 with

Design coupling units in half-bridge circuit.

Claims

Claims 1. System, with:

an n-phase externally excited electrical machine (1), with n> 1;

a controllable first energy store (2), which is n parallel

Having power supply branches (2a, 2b, 2c), wherein each of the

Power supply branches (2a, 2b, 2c) a first terminal (3a, 3b, 3c) which is connected to a respective phase connection (1a, 1b, 1c) of the electric machine (1), and a second terminal (4a, 4b, 4c), which is in each case connected to a common reference rail (9), wherein the reference rail

(9) via a field winding (1 1) of the electrical machine (1) with the neutral point

(10) of the electrical machine (1) is connected.

2. System according to claim 1, wherein the potential at the neutral point (10) of the electric machine (1) is variable.

A system according to any one of claims 1 and 2, wherein each of the n is parallel

Power supply branches (2a, 2b, 2c) at least two connected in series

Energy storage modules (5a, 5b, 5c, 6a, 6b, 6c), each having at least one electrical energy storage cell (7) with an associated controllable

Coupling unit (8) include.

4. Method for operating a system having an n-phase externally excited electrical machine (1), with n> 1, and a controllable first energy store (2) having n parallel power supply branches (2a, 2b, 2c), comprising the steps:

Providing a DC voltage component at each of the power supply branches (2a, 2b, 2c);

Feeding the DC component into the phase terminals (1 a, 1 b, 1 c) of the n-phase electric machine (1); and

Food a field winding (1 1) of the electric machine (1) with the in the phase terminals (1 a, 1 b, 1 c) fed DC voltage component for generating a field exciter in the electrical machine (1).

5. The method according to claim 4, wherein the exciter winding (1 1) with in the

Phase connections (1 a, 1 b, 1 c) fed DC component of the

Star point (10) of the electric machine (1) is fed.

6. The method according to any one of claims 4 and 5, wherein each of the

Energy supply branches (2a, 2b, 2c) at least two series-connected energy storage modules (5a, 5b, 5c, 6a, 6b, 6c), each having at least one electrical energy storage cell (7) with an associated controllable

Coupling unit (8), and wherein the provision of the DC component comprises the connection of at least one of the energy storage modules (5a, 5b, 5c, 6a, 6b, 6c) in the respective power supply branch (2a, 2b, 2c).