WO2010034760A2

WO2010034760A2 - Excitation machine for a synchronous generator

Info

Publication number: WO2010034760A2
Application number: PCT/EP2009/062349
Authority: WO
Inventors: Thorsten Löw
Original assignee: Kenersys Gmbh
Priority date: 2008-09-29
Filing date: 2009-09-24
Publication date: 2010-04-01
Also published as: DE102008049309A1; WO2010034760A3

Abstract

The invention provides an excitation machine for a synchronous generator, said machine both making it possible for the synchronous generator to generate high outputs and also providing independent cold-starting or system operation at low rotational speeds or where there is no grid for reducing high output, in particular in variable-speed operation. According to the invention, the solution of this objective is found in an excitation machine for a synchronous generator (13, 14), characterized in that said generator comprises at least two excitation modules (10, 9; 8, 9), a first (10, 9) module of which is a self-excited module and a second (8, 9) module of which is an externally-excited module. The invention further provides a method for operating a synchronous generator of a wind energy system, said generator connected to a rotor, and a wind energy system of improved design.

Description

PatXML 1/13

description

[0001] Exciter machine for a synchronous generator

Technical area

The invention relates to an exciter machine for a synchronous generator. It further relates to a method for operating a synchronous generator connected to a rotor of a wind turbine and a wind turbine with a synchronous generator and an exciter itself.

State of the art

Synchronous generators are used in particular in the generation of electrical energy in power plants or power plants many uses. So they are used in particular in the field of wind turbines. There, the mechanical energy absorbed by the rotor of the wind power plant is supplied to it via a drive shaft of the drive train with variable speed.

For synchronous generators from the supplied mechanical energy can gain electrical energy, they must be energized to form a magnetic excitation field with DC. For this purpose so-called excitation machines are used. These excitation machines are usually even small generators that generate alternating current at the output, which must be rectified for the excitation of the synchronous generator.

For the formation of the exciting magnetic field in the exciter two different possibilities are conceivable and find use. On the one hand, it is possible to generate the magnetic field for excitation of the excitation machine with permanent magnets. One speaks in this context of a self-excitation or a self-excited exciter machine. On the other hand, excitation machines are also constructed as so-called externally excited machines, in which the exciting magnetic field is generated by current-carrying coils, for which purpose an electric current has to be introduced into the system from the outside.

Self-excited exciters find today rather rare PatXML 2/13

Use. They have the particular disadvantage that they can only provide a limited output power due to the limited field strength of the exciting magnetic field. Such limited output power is often no longer sufficient for the excitation of the synchronous generators at high power throughputs, so that the power that can be generated with such a synchronous generator is limited. For this reason, externally excited exciter machines are currently preferred for the excitation of synchronous generators, in particular in the power station sector, and here in particular in the field of wind turbines. An example of an externally excited excitation system is described in German Patent DE 2 504 894 C2.

Excited excitation machines not only offer the advantage that they produce higher output powers and thus can excite the synchronous generator with a higher power, it also offers a way of controlling the entire generator system by controlling the exciter current in the exciter. Such a control facility naturally does not apply to a self-excited exciter machine.

However, externally excited excitation machines involve a disadvantage that particularly affects the area of wind turbines and makes it clear. In order to be able to start the system as a whole and to energize the synchronous generator for the generation of energy, the exciter machine itself must be supplied with energy. Wind turbines are often exposed in remote locations, such as on remote fields or other land, or even offshore in the water. If it comes to a standstill of a wind turbine, either due to lack of wind or due to a forced stop, for example in the event of a power failure, the system is dead altogether, if not (which is often not the case), an emergency power supply is available.

If the wind turbine does not have its own emergency power supply, so can in a power failure and this braked rotor despite existing PatXML 3 / -13

Wind the plant no longer run and generate electricity, for example, for the maintenance of their own systems. Even in the case of a so-called cold start, so a start of the systems out of a complete rest, this can only be done with an external supply for the exciter. For this purpose, energy must be taken from the grid, which the wind turbine operator has to remove from the grid at comparatively high costs.

Presentation of the invention

This is where the object of the invention. The object of the invention is in fact to provide an exciter for a synchronous generator, which allows both the generation of high power with the synchronous generator in a variable-speed operation as well as a standalone cold start or system operation at low speeds or lack of power for the decrease high power , In addition, a method for operating a synchronous generator connected to a rotor of a wind turbine is to be specified, which satisfies the criteria indicated above. Furthermore, a wind turbine of improved design should also be created.

This object is achieved by an exciter machine for a synchronous generator with the features of claim 1. A procedural solution of the problem is given in claim 6. In the dependent claims 2 to 5 advantageous embodiments of an exciter machine according to the invention are shown, the dependent claims 7 to 10 contain advantageous developments of the method according to the invention. Finally, in claim 11, the invention also specifies a wind turbine of improved design.

The essential and inventive idea of the novel development and design of an exciter for a synchronous generator is to provide two modules in an exciter, both of which can be used for the excitation of the synchronous generator and of which a first a self-energized PatXML 4/13

and a second is a foreign excited module. Although it is within the scope of the invention that in principle more than two modules can be provided, so it is currently preferred to arrange exactly two such modules, namely a self-excited and a foreign excited module.

Modules of the exciter are here understood essentially housed in the context of a common machine units, each of which can generate and deliver an excite voltage or an exciting current for the synchronous generator detached from each other. It is readily conceivable that the individual excitation modules are structurally completely separated from each other. Likewise, however, it is also within the scope of the invention that individual components of the exciter are equally attributable to both modules, the self-excited and the externally excited module. In the widest scope of the invention, it is ultimately also possible that the exciter modules of the exciter machine are so far separated that they can be considered as two separate excitation machines. Ultimately crucial is that the two excitation modules can be placed with their outputs to an input for the excitation voltage or the excitation current of the synchronous generator, with an optional circuit of the one or the other module or possibly even both modules together for the actual excitation of the Synchronous generator should be possible.

In that regard, a control is usually provided in the context of the invention, depending on predeterminable parameters or by manual selection that or those exciter module (s) provides and interconnects that are to be provided in the respective operating mode for excitation of the synchronous generator.

It should be readily understood that the excitation of a synchronous generator in a variety of operating situations reliably and demand-dependent is possible with the exciter according to the invention, especially in a variable-speed operation of the synchronous generator. The achievable so PatXML 5 / -13

Advantages have a particular effect in the field of wind turbines.

A particularly compact design of an inventive

Exciter machine results when it is formed as mentioned in claim 3. The thus mounted on a common shaft with the rotor of the synchronous generator runner of the excitation machine with anchors and arranged around the armature power windings so far represents the "power component" of the exciter for both modules, the self-excited and the externally excited module, this runner opposite and arranged as a stator are then on the one hand excitation coils with corresponding leads of the externally excited module, on the other permanent magnet of the self-excited module.To rectify the AC voltage supplied by the exciter or the AC for the DC excitation of the synchronous generator, is followed by the power windings on the common shaft From there, the excitation voltage or the exciting current is fed into the rotor of the synchronous generator which forms the exciting magnetic field ann, when the permanent magnets are arranged on the stator in the region of the cores of the exciting coils. The combined exciter thus differs in terms of their dimension and the basic design essentially not from a conventional exciter machine with only external excitation. The only and essential difference is the additional arrangement of permanent magnets in the region of the cores of the excitation coils, this constructive measure brings no, at least no significant additional space requirements. This fact is especially in the field of wind turbines of crucial advantage, since there is limited space in the drive train and the generator typically receiving nacelle.

As a rectifier circuit is preferably a simple diode bridge can be selected, which is low maintenance and easily on a rotating PatXML _6/13

Shaft can be arranged.

Advantageously, a equipped with a synchronous generator and equipped with an exciter machine according to the invention wind turbine operated in different operating mode. For a start of the synchronous generator at the start of the wind turbine, especially in a so-called cold start, in which the systems of the system had fallen dead, initially the self-excited excitation module is used to excite the synchronous generator. On the one hand, no energy needs to be drawn from the grid and costly to start up in order to energize the synchronous generator. On the other hand, it is possible to generate sufficient power with the externally excited excitation module already at comparatively low speed of the rotor and thus the generator shaft (for example, speeds in a range of 300 rev / min) with the self-excited excitation module to start the synchronous generator for energy allow. When using a foreign excited excitation machine or the externally excited module of the exciter machine according to the invention higher speeds would be required for this purpose.

If the synchronous generator is then started and generates enough energy for at least a self-supply of the systems of the wind turbine, then the excitation of the synchronous generator can be made with the externally excited exciter module. This has the advantage that the output voltage of the synchronous generator for self-supply of the systems of the wind turbine is regulated by regulating the excitation voltage branched off from the generator for the externally excited exciter module of the exciter. This operating state is particularly relevant in a so-called "idle" mode in which the wind energy plant does not feed into the grid, but can generate sufficient energy itself for the maintenance of its own systems, in particular for feeding the controller and other consumers In particular, self-sufficiency does not require the wind energy plant to be PatXML 7/13

or in the medium term failure of the network to be fed into, to completely stop and shut down the systems.

If the wind turbine drives under full load and generates electrical energy that is fed into the grid, the excited exciter module is preferably used for the excitation of the synchronous generator. In this case, the operating voltage of the system or the wind energy plant can then be regulated by regulating the exciter voltage for the externally excited exciter module.

Finally, it is also possible in an operating condition that largely neutralized by the self-excited excitation module excitation voltage originating from the self-excited excitation module and so the output voltage of the synchronous generator at a lowest possible level is kept near zero, ideally even at zero, with the externally excited excitation module ,

In principle, it is always conceivable to share the excitation power generated by the self-excited exciter module and to use it together with the excitation power generated by the externally excited exciter module to excite the generator. Alternatively, it may be provided with appropriate design to turn off the self-excited excitation module or short circuit. If the power coils are identical for both modules, ie only one component with power coils is used, which are excited both by the permanent magnets of the self-excited excitation module and by the excitation coils of the externally excited excitation module, can always largely neutralization and elimination of the self-excitation counteracted by a correspondingly controlled external excitation, for example to a "zero excitation", in which, as already described above, the output voltage of the synchronous generator is set to a low value close to zero.

Part of the invention is finally a wind turbine with a synchronous generator and an exciter machine, as described above.

Brief description of the drawings

Further advantages and features of the invention will become apparent from the PatXML 8 / -I3

following description of an embodiment with reference to the accompanying figures. Showing:

Fig. 1 is a schematic representation of the excitation of a

Synchronous generator according to an embodiment of the invention; and

Fig. 2 is a schematic, partially cut away partial view of the stator of the exciter in an embodiment according to the invention.

Way (s) for carrying out the invention

In the figures is in a greatly simplified and schematic form a

Embodiment of an inventive exciter of a synchronous generator shown. The representations make no claim to completeness, are limited to pure schematic representations to explain the essential components and components of the embodiment according to the invention.

In Fig. 1, an embodiment of an exciter according to the invention together with control and downstream rectification and to be excited synchronous generator is shown in an electrical circuit diagram. An exciter actuator 1 is connected to a mains supply 2. The excitation controller 1 contains a rectifier 3 for generating a DC voltage from the AC voltage provided by the mains supply 2 available. The rectifier 3 is controlled by a control unit 4, which sets the rectifier at 5 a setpoint and is fed at 6 with an actual value. The controller 4 also controls a power switch 7, with which the power supply 2 to the rectifier can be switched on or off.

From the exciter actuator 1, the rectified rectifier 3 voltage can be applied to the excitation coils 8 of the stator of the exciter. With the excitation coils 8, a magnetic field for excitation of the rotor 9 of the exciter machine is generated. The excitation coils 8 and the rotor 9 thus constitute a first module of the exciter, which is a foreign excited module.

In addition, in the stator or stator of the exciter machine with respect PatXML 9 / -13

arranged on the rotor 9 in a suitable arrangement of permanent magnets 10, which together with the rotor 9 form a second excitation module, which is self-excited.

Downstream of the rotor 9 of the exciter machine is a rectifier bridge 12 formed from diodes 11, the output of which is connected to the exciter coils 13 arranged on the rotor of the synchronous generator. Opposite this, the stator 14 is the actual generator unit of the synchronous generator. Further, in the circuit between the rectifier bridge 12 and the exciter coil 13 is still a surge arrester 15 interposed.

With a dashed line is finally indicated which of the elements shown are located on the rotating shaft 16 of the system.

In operation, from the rotating excitation coils 13 and the

Stand 14 formed synchronous generator excited by means of excitation current generated by the exciter. The rectified with the rectifier bridge 12, tapped by the rotor 9 of the exciter current is supplied to the exciting coils 13 of the synchronous generator. There, a magnetic field is generated by means of the direct current, which generates an alternating current in the coils there by the movement of the rotor and the exciter coils 13 arranged therein relative to the stator 14. The excitation of the exciter machine can now either via one of the modules, via the externally excited or via the self-excited module, take place (an excitation on the self-excited module always takes place in the embodiment shown here). Thus, without external supply 2 only the self-excited module formed by the permanent magnets 10 and the rotor 9 can be used to generate the excitation voltage for the excitation coils 13 of the synchronous generator.

Alternatively, with the involvement of the power supply 2 and the externally excited module, formed by the excitation coils 8 and 9 find the runner use.

If the system according to the invention in particular in a

Wind turbine used, so is the rotating shaft 16 with the PatXML _{1 O} / 13

Rotor of the wind turbine connected and is driven by this. The mains supply 2 can either be a mains supply originating from the power grid to which the wind energy plant is connected, or else be branched off from the output voltage of the synchronous generator when the synchronous generator is already running.

In normal operation, the exciter machine will be operated mainly with the externally excited module, ie mainly by interaction of the excitation coils 8 with the rotor 9 and the windings arranged thereon. In particular, however, in the case of a cold start, e.g. After a power failure, can be used for the first startup of the wind turbine on the self-excited module of the exciter, so the combination of permanent magnet 10 and rotor 9, without the excitation coils 8 are supplied with the power supply 2. This has the particular advantage that for a cold start of the wind turbine no electrical energy has to be removed from the connected network and must be purchased costly.

In Fig. 2 is a section of the stator 17 of the present invention containing two modules exciter machine according to the invention is shown in a schematic representation. In this embodiment variant, the exciter coils 8 are wound around corresponding armatures 18, which serve as magnetic field reinforcing core of the coils. In a region 19, the lateral turns of the coils 8 are cut away, and the cores 18 are shown partially cut. Here it is easy to see that in the cores 18, the permanent magnets 10 are embedded. The permanent magnets 10 are alternately facing the north and the south pole of the inner surface of the annular stator 17 to generate in the usual way an alternating magnetic field in the stator for the excitation of the rotor 9. The coils 8 are connected so that they generate a corresponding magnetic field as the permanent magnet 10 to the associated armature 18.

From the illustration in Fig. 2 is again clearly seen that PatXML 11/13

the exciter machine in this embodiment is a kind of hybrid machine in which both modules, the self-excited module formed by the permanent magnets 10 and the rotor 9 as well as the externally excited module formed by the exciting coils 8 and the rotor 9 realized with a stator and a rotor are. Of course, it is within the scope of the invention, however, also possible to separate the modules, if necessary to provide two independent stand and two independent runners.

[0039] List of Reference Numerals

[0040] 1 exciter plate

2 mains supply

3 rectifier

4 control unit

5 setpoint

6 Actual value

7 power switch

[0047] 8 exciting coil

9 runners

10 permanent magnet

11 diode

12 rectifier bridge

[0052] 13 exciter coil

14 stands

15 surge arrester

16 rotating shaft

17 stands

18 anchors

19 area

Claims

PatXML 12/13 claims

1. excitation machine for a synchronous generator (13, 14), characterized in that it comprises at least two excitation modules (10, 9, 8, 9), of which a first (10, 9) a self-excited and a second (8, 9 ) is a foreign excited module.

2. Exciter according to claim 1, characterized in that it contains a controller (4) and that controlled by the controller (4) for energizing the synchronous generator (13, 14) used exciter module (10, 9; 8, 9) selectable and is interconnected accordingly.

3. Exciter according to one of the preceding claims, characterized in that it comprises a on a common shaft (16) with the rotor of the synchronous generator (13, 14) mounted rotor (9) with anchors and arranged around the armature power windings, a stator (17 Having a plurality of circumferentially distributed, each wound around a core (18) excitation coils (8) and circumferentially distributed permanent magnet (10) and arranged on the shaft (16), the power windings downstream rectifier circuit (12).

4. Excitation machine according to claim 3, characterized in that the permanent magnets (10) on the stator (17) in the region of the cores (18) of the excitation coils (8) are arranged.

5. Excitation machine according to one of claims 3 or 4, characterized in that the rectifier circuit (12) is a diode circuit, preferably a diode bridge.

6. A method for operating a rotor connected to a synchronous generator of a wind turbine, characterized in that this is selectively energized by means of a foreign excited and / or by means of a self-excited exciter module of an exciter machine.

7. The method according to claim 6, characterized in that for starting the synchronous generator at a start of the wind turbine, the self-excited exciter module energized the synchronous generator.

8. The method according to claim 6, characterized in that excited for low rotational speeds of the rotor of the synchronous generator via the externally excited exciter module and the excitation voltage, the output voltage PatXML _{13/1 3}

the synchronous generator is regulated for self-supply of the systems of the wind turbine.

9. The method according to claim 6, characterized in that energized in grid operation, in which the wind turbine feeds electrical energy into a connected network, the externally excited exciter module the synchronous generator.

10. The method according to claim 6, characterized in that the externally excited excitation module is controlled so that it neutralizes the excitation voltage resulting from the self-excited excitation module and keeps the output voltage of the synchronous generator to zero.

11. Wind energy plant with a wind-driven rotor and a drive train to this connected synchronous generator (13, 14), characterized in that it comprises for exciting the synchronous generator (13, 14) an exciter machine according to one of claims 1 to 5.