WO2013020148A2

WO2013020148A2 - Energy generation plant, in particular a wind power plant

Info

Publication number: WO2013020148A2
Application number: PCT/AT2012/000195
Authority: WO
Inventors: Gerald Hehenberger
Original assignee: Gerald Hehenberger
Priority date: 2011-08-11
Filing date: 2012-07-26
Publication date: 2013-02-14
Also published as: WO2013020148A3; AT511782A1

Abstract

The invention relates to an energy generation plant, in particular a wind power plant, comprising an input shaft connected to a rotor (1), a generator (13) connected to a network (9), a differential gear (10 to 12) by which a drive is connected to an electrical differential drive (18), and an electrical energy store (32), wherein the generator (13) comprises an excitation controller (35) and wherein the differential drive (18) is connected to a frequency converter (19). Both the excitation controller (35, 37) and the frequency converter (19) of the differential drive (14) are connected to the energy store (32).

Description

Energy production plant, in particular wind power plant

The invention relates to an energy production plant, in particular a wind turbine, with a drive shaft connected to a rotor, a generator connected to a network, a

Differential gear, of which a drive is connected to an electric differential drive, and with an electric

Energy storage, wherein the generator has an exciter control and wherein the differential drive is connected to a frequency converter.

Wind power plants are becoming increasingly important

Power generation plants. As a result, the percentage of electricity generated by wind is continuously increasing. This, in turn, requires new standards in terms of power quality and performance

On the other hand, a trend towards even larger wind turbines.

At the same time, there is a trend towards offshore wind turbines, which require system sizes of at least 5 MW of installed capacity. Due to the mentioned higher demands on the power quality here win highly dynamic or even in case of network errors controllable systems of particular importance.

All systems have in common is the need for a variable

Rotor speed, on the one hand to increase the aerodynamic

Efficiency in the partial load range and on the other hand to control the torque in the drive train of the wind turbine. The latter for the purpose of speed control of the rotor in combination with the

Rotor blade adjustment.

At present, therefore, wind turbines are in use, which meet this requirement by using variable-speed generator solutions increasingly in the form of so-called permanent magnet-excited low-voltage synchronous generators in combination with IGBT frequency converters. However, this solution has the disadvantage that (a) the

Wind turbines only by means of transformers to the

Medium-voltage network can be connected and (b) the necessary for the variable speed frequency converter very powerful and therefore a source of efficiency losses. Alternatively, therefore Also called differential drives are used, which directly connected to the medium-voltage network externally-excited medium-voltage synchronous generators in combination with a differential gear and an auxiliary drive, which preferably provides a permanent magnet synchronous machine in combination with an IGBT frequency converter low power use.

WO 2010/121783 A shows a differential system with a

electric servo drive with a permanent magnet excited

Synchronous machine in combination with an IGBT frequency converter.

The excitation of externally excited medium-voltage synchronous generators takes place, for example, by means of a so-called static excitation, which essentially supplies the rotor winding of the synchronous generator with a regulated exciting current via a slip ring (FIG. 5). Alternatively, so-called brushless excitation devices are used which have an exciter machine with a rotating diode rectifier, which is usually arranged at the end of the synchronous generator remote from the drive (FIG. 6). The exciter machine is also regulated

Energizer supplied, which, however, in comparison to the former solution with much lower currents is the Auslangen. The control of the excitation device has essentially the tasks of (a) to regulate the amplitude of the voltage at the generator terminals constant to a predetermined value, (b) the predetermined

Adjust power factor (cos-phi) and (c) protect the exciter winding from overload.

The new standards for grid feeding of

Energy recovery systems, in particular wind turbines, make it necessary that in the case of network faults, the controllability of both the differential drive and the excitation control is maintained throughout the duration of the network fault. In addition, state-of-the-art excitation control systems are only capable if they are equipped with a complex UPS system.

The invention is therefore based on the task corresponding

To make arrangements, so with the least possible effort the full function of differential drive and excitation control upright preserved .

This object is achieved with an energy recovery system having the features of claim 1.

Preferred embodiments of the invention are the subject of

Subclaims.

Hereinafter, preferred embodiments of the invention will be described in detail with reference to the attached drawings

described. It shows

Fig. 1 shows the principle of a differential gear with a

electric differential drive according to the prior art,

2 shows the principle of a static excitation control according to the prior art,

3 shows a possible emergency power supply of a dif ferential

drive,

4 shows by way of example the course of the reactive current output of a

separately excited synchronous generator during a grid fault, with and without emergency power supply for the excitation control,

Fig. 5 shows an embodiment of an inventive configuration of the emergency power supply for the excitation control and

Fig. 6 shows an alternative embodiment of an inventive

Configuration of emergency power supply for the

Exciter control.

The power of the rotor of a wind turbine is calculated from the formula

Rotor power = Rotor area * Power coefficient * Wind speed ³

* Airtightness / 2 where the power coefficient depends on the number of revolutions (=

Ratio of blade tip speed to wind speed) of the rotor of the wind turbine is. The rotor of a wind turbine is designed for an optimal performance coefficient based on a in the course of Development speed to be determined (usually a value between 7 and 9) designed. For this reason, when operating the wind turbine in the partial load range, a correspondingly low speed must be set in order to ensure optimum aerodynamic efficiency.

Fig. 1 shows a possible principle of a differential system for a variable speed wind turbine. A rotor 1 of the wind turbine, which sits on a drive shaft 2 for a main gear 3, drives the main gear 3 at. Between the main gear 3 and the generator 13 is a differential stage 4, which is driven by the main gear 3 via a planet carrier 10 of the differential stage 4. The generator 13 - preferably a third-excited medium voltage synchronous generator - is connected to a ring gear 11 of the differential stage 4 and is driven by this. A pinion 12 of the

Differential stage 4 is connected to a differential drive 14. The speed of the differential drive 14 is regulated to

On the one hand to ensure a constant speed of the generator 13 at variable speed of the rotor 1 and on the other hand to regulate the torque in the drive train of the wind turbine. In order to increase the input speed for the differential drive 14, a 2-stage differential gear is selected in the case shown, which is a matching gear stage 15 in the form of a spur gear between the

Differential stage 4 and the differential drive 14 provides. The differential stage 4 and the adjustment gear 15 thus form the 2-stage differential gear. The differential drive 14 is a three-phase machine, which is connected via a frequency converter 16 and a transformer 17 to the medium-voltage network 9.

The power of the differential drive 14 is substantially proportional to the product of percent deviation of

Rotor speed from its basic speed (usually referred to as slip) times rotor power. Accordingly, a large one requires

That is, the smaller the necessary speed range on the drive shaft, the smaller the required differential drive and therefore also the effort for its production and operation can be. Turbomachines of any kind such as wind turbines, water turbines or pumps, plants for the production of energy from ocean currents, or any kind of

Industrial plants, which work with limited speed range, are therefore the ideal fields of application for differential systems.

Fig. 2 shows the principle of a static excitation device with the following essential components: uninterruptible

Power supply (UPS), exciter transformer to adjust the voltage level (T), controlled rectifier (GR), de-excitation device (EE), exciter winding (EW) and exciter control (ER). The components UPS and de-energizing equipment (EE) are optional and only necessary if a uniform control dynamics is required in case of network faults.

Fig. 3 shows a possible basic structure of the electrical part of a differential system according to FIG. 1. With the

Three-phase machine 14 are connected to two so-called frequency converter output stage 22. These essentially consist of a controlled IGBT full bridge 19, a controller, DC link capacitors 20, a current measurement and DC fuses 21. The cooling

in particular of the IGBTs 19 is preferably a water cooling, but can also be carried out as air cooling.

The DC voltage intermediate circuit 23 is the link for the individual frequency converter output stages 22. To protect the

Frequency converter against overvoltage is here also preferably a so-called brake chopper 24 connected with resistors. This brake chopper 24 can be used at e.g. Power failure also convert excess energy into heat.

In addition, it is used for power generation plants

Differential systems also used an emergency power supply 25. This emergency power supply 25 preferably consists essentially of connected to the DC voltage intermediate circuit 23

High-performance capacitors. To the voltage level or the

Operating voltage of these high-performance capacitors optimal or

To make this flexible, these can be connected via DC / DC converters to the

DC voltage intermediate circuit 23 are connected. Depending on the operation of the power plant, the emergency power supply 25 may also take over the function of the brake chopper 24 in whole or in part. Between the

DC intermediate circuit 23 and the network 26, the same frequency converter output stages 22 are preferably used.

In the case of a differential system acc. Fig. 1 works this both regenerative and motor. That is, in engine operation, the machine-side frequency converter output stage 22 operates as

Inverter for speed / torque control and the line-side frequency converter output stage 22 as a rectifier module. in the

regenerative operation works the machine side

Frequency converter output stage 22 as a controlled rectifier module and the line-side frequency converter output stage 22 as a so-called active grid feed module (inverter).

Thus, the network-side frequency converter output stage 22 of the

Grid operators meet required power quality criteria, a so-called LCL filter 27 is provided. There are also fuses 28, circuit breaker 29 and a power transformer 30, which adapts the preferably low voltage of the differential drive to the voltage of the network 26.

In order to keep the load on the three-phase machine 14 as low as possible, the IGBT full bridges 19 are clocked at the motor side, preferably at 4 kHz, on the network side, depending on the design of the LCL filter 27, a different clock frequency can be selected. As with increasing clock frequency, the losses in the IGBT full bridges 19 increase or the allowable current load of the IGBT full bridges 19 is lower, depending on the operating point of the differential system, the

Clock frequency are set to an optimal for the utilization of the system value or the clock frequency during operation are varied accordingly.

Fig. 4 shows the course of the reactive current output of a third-excited synchronous generator during a power failure, with (continuous line) and without (dotted line) emergency power supply for Pathogen control. This assumes a fast break in the grid voltage from 100% to 10%. The mains voltage then remains at this level for ls and then goes back to the original output value. Usually, the grid rules require that during a mains voltage dip the

Energy generation systems feed at least the rated current as reactive power into the grid. Fig. 4 shows that you can not meet the grid codes without emergency power supply for the excitement, since it is no longer possible after about 200ms to give reactive power in the network (dashed line). That is exactly what is important to support the network.

Another advantage is that the generator can be more easily maintained at rated speed when the excitation remains on.

In addition, during this voltage dip of the

Generator 13 emitted reactive power can not be controlled, or sets the reactive current depending on mains voltage dips duration and - size according to the design parameters of the synchronous generator. Thus one can not possibly, deviating from it

Meet requirements.

FIGS. 5 and 6 show embodiments according to the invention of the uninterruptible emergency power supply 25 for the frequency converter 19 of the differential drive 14, which is preferably a

As has already been described in connection with FIG. 3, here too IGB full bridges 19 are connected to the three-phase machine 14 or via the transformer 30 to the medium-voltage network 26. The DC voltage intermediate circuit 23 is the connecting element for the individual IGB full bridges 19. The capacitors 31 connected in the DC voltage intermediate circuit are preferably foil capacitors and serve, above all, for smoothing the intermediate circuit voltage or the ripple current. To protect the frequency converter against overvoltage is also here preferably via an IGBT half-bridge

controlled so-called brake -Chopper 24 with resistors

connected. This brake chopper 24 has the task any occurring in the DC voltage intermediate circuit 23 voltage spikes

to suck off and thereby a system shutdown due to overvoltage avoid. In order to make sure the power supply of the frequency converter 19, for example, network faults, an energy storage is connected as an emergency power supply 25, which is preferably connected to the DC voltage intermediate circuit 23

High performance capacitors 32 exists. However, the energy store 25 can also have accumulators or other electrical storage media instead of the high-performance capacitors.

The nominal voltage of the DC intermediate circuit 23 is in the case of the use of 1700V IGBT- modules usually around the 1050Vdc and should ideally be regulated in a range of a maximum of 1150Vdc and a minimum of lOOOVdc, so as not to limit the control capacity of the differential drive. If one were to design the emergency power supply 25 for this voltage range, this would be due to the (a) necessary high number of parallel capacitors and (b) the small realizable margin between maximum and minimum allowed

Voltage of the DC intermediate circuit 23 are very large and consequently also expensive accordingly. To the voltage level or the

Operating voltage of these high-performance capacitors optimal

Therefore, they are preferably via a DC / DC converter consisting for example of an IGBT half-bridge 33 and a

Inductance 34 connected to the DC voltage intermediate circuit 23. The maximum voltage for the high power capacitors 32 may then be set to e.g. 300-400Vdc be limited. Preferably, the DC / DC converter 33 described above is a bidirectional buck converter. Optionally, the DC / DC converter can also be designed with an IGBT full bridge.

The static excitation device 35 (FIG. 5) and the

Excitation device for the exciter machine 37 (FIG. 6) of the

In contrast to the frequency converter 19, synchronous generators 13 operate at a substantially lower voltage level or operating voltage, namely typically in a range from approximately 80 Vdc to 130 Vdc with static excitation according to FIG. 5 or approximately 20 Vdc to 50 Vdc

Exciter machine according to FIG. 6. If one were to try to realize the supply of the excitation device directly from the DC voltage intermediate circuit 23 in order to use the emergency power supply 25, this would only be due to the high voltage difference with a DC / DC converter (extremely) consuming to realize. With another DC / DC converter, consisting for example of an IGBT half-bridge 36 and a

Inductance, which at the respectively optimum voltage level of

High power capacitors 32 is located, a power supply for the field winding can be realized with a voltage in the required range of 20-130 Vdc with simple means. Preferably, in this case, a unidirectional DC chopper (unidirectional buck converter) is designed in the form of an IGBT full bridge, but may also consist of an IGBT half-bridge or one or three chopper modules (half-bridge consisting of a diode and an IGBT). The IGBT full bridge has the advantage that standard converter hardware can be used and the output ripple is smaller than with a half bridge and thus the filtering at the output is facilitated. Depending on the design of energy storage, an additional

Capacitor may be required at the DC-DC input because the high current ripple reduces the life of the energy storage. The filter of the buck converter 35 can be used with regard to (a) control dynamics, (b) current ripple (improved power quality of the generator), (c)

Common mode voltage (avoidance of bearing currents) can be optimized.

If a fast de-energizing is relevant for the application, a bidirectional DC-DC converter can be used. This can be de-energized with the negative DC link voltage. Preferably, the bidirectional DC-DC converter can be implemented by an IGBT full bridge (standard converter), wherein the field winding is switched to two half-bridge outputs and a half-bridge output remains free, but can also be realized by two IGBT half-bridges.

For the purposes of the invention, this means that ideally

Voltage level or the operating voltage of the emergency power supply 25 between the necessary operating voltage levels of

DC intermediate circuit 23 and excitation control 35 is located. This is an optimal dimensioning of the energy storage 32 at

simultaneous use by both frequency 16 and excitation control 35 guaranteed.

The energy flow for the supply of the exciter control 35 takes place in normal operation via the network-side IGBT full bridge 19, DC / DC converter 33, High power capacitors 32 and DC / DC converters 36

The main advantages of the configuration described are (a) the DC link voltage of the DC intermediate circuit 23 can also be regulated in case of network errors, (b) the energy content of the

Energy storage 32 can be better used, (c) the excitation of the synchronous generator 13 can be controlled even in case of power failure and (d) the exciter control 35 can be implemented easily and inexpensively.

The described embodiments are only examples and are preferably used in wind turbines, but are also feasible in technically similar applications. This concerns v.a. Hydro-turbines and pumps and installations for generating energy from ocean currents. The same apply to these applications

Basic requirements as for wind turbines, namely variable

Flow rate. The drive shaft is in each case driven directly or indirectly by the devices driven by the flow medium, for example water.

In addition, what is said also applies to any type of system which, due to the general conditions, uses differential drives for realizing variable speed on the drive shaft, that is to say any type of drive for (industrial) systems which has limited power

Speed range can be operated.

Claims

Claims:

1. power generation plant, in particular wind turbine, with a with a rotor (1) connected drive shaft, a with a network (9) connected to the generator (13), a differential gear (10 to 12), of which a drive with an electric

Differential drive (18) is connected, and with a

electrical energy store (32), the generator (13) having an exciter control (35, 37) and wherein the differential drive (18) is connected to a frequency converter (19), characterized in that both the exciter control (35, 37) and the frequency converter (19) of the differential drive (14) are connected to the energy store (32).

2. Energy production plant according to claim 1, characterized by an emergency power supply (25) containing the energy store (32).

3. Energy production plant according to claim 1, characterized in that the exciter control (35, 37) contains the energy store (32).

4. Power generation plant according to one of claims 1 to 3, characterized in that the differential drive (18) via the frequency converter (19) with a DC intermediate circuit (23) is connected.

5. Energy production plant according to one of claims 1 to 4, characterized in that the DC intermediate circuit (23) by means of a DC / DC converter (33) to the energy store (32)

connected.

6. Energy production plant according to one of claims 1 to 5, characterized in that the

Excitation control (35, 37) by means of a DC / DC converter (36) to the energy storage device (32) is connected. Power generation plant according to one of claims 1 to 6, characterized in that the DC / DC converter (33, 36) is a preferably bidirectional DC chopper.

Power generation plant according to one of claims 1 to 7, characterized in that the DC / DC converter (33, 36) has IGBT full bridges and / or thyristors.

Energy production plant according to one of claims 1 to 9, characterized by an exciter control (35, 37) for controlling the voltage and / or the reactive current of the generator (13).

Energy production plant according to one of claims 1 to 10, characterized in that the operating voltage of the

Energy storage (32) between the operating voltages of the

DC intermediate circuit (23) and the excitation control (35, 37) is located.