EP2411665A1

EP2411665A1 - Method and circuit configuration for operating a wind power plant on an electrical supply grid

Info

Publication number: EP2411665A1
Application number: EP09776482A
Authority: EP
Inventors: Matthias Bartsch; Jochen Anemüller
Original assignee: Powerwind GmbH
Current assignee: Powerwind GmbH
Priority date: 2009-03-26
Filing date: 2009-03-26
Publication date: 2012-02-01
Also published as: WO2010108515A1

Abstract

The invention relates to a method for operating a wind power plant on a load formed by an electrical supply grid (VN), wherein the electrical output power of the electrical generator (G) thereof driven by the wind-powered rotor thereof is accepted by the supply grid (VN) in a normal condition, and wherein the wind power plant is transitioned into a safe condition upon occurrence of an interruption in the power acceptance, wherein the wind power plant is provided with a replacement load (R1), from which the acceptance of the output power of the generator (G) is maintained for a transition time during the transition from the normal condition thereof to the safe condition, and to a circuit configuration suitable for performing the method.

Description

ZIMMERMANN

PATENT OFFICES EUROPEAN PATENT ATTORNEYS EUROPEAN TRADEMARK ATTORNEYS EUROPEAN DESIGN ATTORNEYS

Dipl.-Ing. H. Leinweber (1930-1976) Dipl.-Ing. H. Zimmermann (1962-2002) Dipl.-Phys. Dr. Jürgen Kraus Dipl.-Ing. Thomas Busch Dipl.-Phys. Dr. Klaus Seransky

Rosental 7 D-80331 Munich

TEL. + 49-89-231124-0 FAX + 49-89-231124-11

the krsd / wegs

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PowerWind GmbH, 20537 Hamburg

Method and circuit arrangement for operating a wind turbine on an electrical supply network

The invention relates to a method for operating a wind turbine on a load formed by an electrical supply network, in which in a normal state of the wind turbine, the electrical output of their driven by their wind rotor rotor electric generator is removed from the supply network, and wherein the wind turbine Entry of a failure of the power loss is transferred to a safe state, as well as a suitable circuitry for this purpose.

In such methods and circuit arrangements, in the normal state of the wind power plant, the electrical supply network decreases the output power generated by the generator. However, if a malfunction, which may be caused for example by a fault in the electrical supply network or a converter of the wind turbine, the power loss is interrupted, this means for the generator, a sudden shutdown of the electrical load fed by him the counter torque exerted by him on the rotor drops abruptly. This leads to an increase in speed on the mechanical side, which can cause both the rotor and the generator to reach an overspeed range. On the electrical side, there is a voltage increase that can lead to overvoltages. Therefore, it is necessary in such disturbances of the power take-off, to convert the wind turbine into a safe state. This is done conventionally by the well-known in wind turbines pitch adjustment, with which it is possible to regulate the torque generated by the windangeströmten rotor. However, the settling time of the blade adjustment is greater than 5 seconds and amounts in particular to 7 to 8 seconds. This results in the transfer of the wind turbine in its safe state, a transitional period during which the above-mentioned mechanical and electrical overloads can not be excluded. Although conventional wind turbines are provided with a brake that could be used to limit the speed. However, this has the disadvantage of high mechanical stress.

The invention has for its object to provide a method of the type mentioned, with which the wind turbine can be transferred in a failure of the power loss without the risk of overuse in a safe state, and to provide a suitable circuitry for this purpose.

According to the invention this object is achieved in terms of the method in that the wind turbine is provided a replacement load from which the decrease in the output power of the generator is maintained for a transition occurring during the transition from its normal state to its safe state transitional time.

The inventively provided derivation of the output power of the generator by the substitute load sets in comparison to the settling time of a mechanical control, for example, the pitch of the wind turbine, virtually instantaneously. As a result, the mechanical and electrical load conditions of the wind turbine are kept virtually unchanged until the mechanical control takes effect, so that the wind turbine can be converted by the latter without harmful load jumps in their safe state. In the ideal case, the decrease in the replacement load corresponds to that of the supply network before the fault occurs. Although in the method according to the invention the temporary loading of the very high, but this is required only during the relatively short transitional period, which requires the mechanical control in order to down-regulate the torque absorption of the rotor from the incoming wind. In practice, the transitional period in which the replacement load must take over the output of the electric generator lasts only a few seconds, for example 2 to 3 seconds.

An advantageous embodiment of the method according to the invention is that the wind turbine is disconnected from the supply network when the disturbance occurs and the equivalent load is connected directly to the output of the generator. This has the particular advantage that errors in the downstream equipment parts of the generator, for example, one of the power supply serving in the power supply inverter, do not affect the decrease in power by the equivalent load.

Furthermore, it is preferred that the replacement load emits the electrical power supplied to it as dissipation heat. Since the load of the replacement load lasts only a few seconds, it is possible even at a relatively high power rating of the wind turbine to deliver the generator power removed from the surplus load as Dissipationswärme to the ambient air. In this context, it is expedient that the temperature of the substitute load is monitored and the excess of a predetermined limit value, the decrease in the output of the generator is stopped. This temperature monitoring and responsive decommissioning of the replacement load ensures that the latter is not thermally damaged or even destroyed.

A circuit arrangement provided for achieving the object according to the invention for operating a wind energy plant on a load formed by an electrical supply network, having an electric generator which can be driven by a wind-driven rotor of the wind energy plant, at the electrical output of which the electrical output power which can be generated by it is detachable, on the input side to the output of the generator and electrical converter connected on the output side to the supply network, and a safety device monitoring the decrease of the electrical output of the generator, by the wind turbine from a normal state in which the output power of the generator is removed from the supply network upon the occurrence of a power failure is, in a safe state can be transferred, according to the invention is characterized in that the wind turbine of the safety device for a during the transfer of their Normal state occurring in their safe state transitional time can be separated from the supply network and the output of the generator to a power loss maintaining spare load is switched on.

Further advantageous embodiments of the invention are specified in the dependent claims 6 to 15.

Further features, advantages and details of the invention will become apparent from the following description in which a Ausfϋhrungsbeispiel the invention is explained in detail with reference to the drawings.

In the single FIGURE 1 of the drawing, an embodiment of a circuit arrangement according to the invention is shown schematically. This comprises a generator G which is driven by a wind-driven rotor, not shown, and which in this exemplary embodiment is designed as a three-phase current generating asynchronous generator. Accordingly, although in Fig. 1 schematically illustrated only as a single-pole line, the line L emanating from the generator G, designed as a three-phase three-phase line.

In the normal operation of the wind power plant equipped with the switching arrangement shown, the generator for outputting its electrical output power to a supply network VN via a converter 12 is connected. In this case, the converter 12 has in the usual way a rotor-side pulse-controlled inverter and a line-side pulse-controlled inverter, which are connected to one another via a DC intermediate circuit, and the detailed structure of the converter 12 will not be described further here, just as the coupling designed in the usual way to the supply network VN, in which the voltage is possibly further transformed via a medium voltage transformer to the mains voltage.

On the output side of the inverter 12, a first switch S1 is arranged to take the wind turbine off the grid in the event of a fault in the electrical supply network VN or in the inverter 12 through its opening.

Furthermore, a second switch S2 may be connected upstream of the input of the converter 12. When using an asynchronous machine, as in the example shown, this second switch S2 is dispensable and is usually not used. Much more the second switch S2 is used when using synchronous generators. Thus, on the one hand, when the switch S2 is open, it is possible to work without voltage on the converter 12. On the other hand, the switch S2 is operated to shut down the system in case of faults, which are due to an error of the inverter 12.

Thus, the wind turbine can be taken off the grid by operating the switch S1 and / or the switch S2, if a fault occurs. In order to compensate for the abrupt drop in the electrical load supplied by the generator G, a substitute load, which is indicated schematically in FIG. 1 as a dissipative resistor R1, is connected to the switching group designated by a third switch S3. In a specific embodiment, the substitute load may be formed by a number of load resistors which are connected in star configuration. Alternatively, it can also be provided to switch the load resistors in a triangular arrangement. The load resistors are housed in the tower base of the wind energy plant.

As can be clearly seen from FIG. 1, the switching group 20 or the line section L3 leading to the switch S3 is switched on at a point P into the line L connecting the generator G and the supply network VN, which is connected directly downstream of the generator G. In other words, in the line section L1 between the generator G and the branch point P no power electronics of the inverter 12 is arranged more. The latter is instead arranged in the section L2 of the line L which adjoins the branch point P downstream. Thus, the replacement load R1 can be reliably switched on by closing the switch S3, since no errors or interruptions are to be feared in the simply executed line section L1.

If a fault occurs, be it due to a fault in the supply network VN or an error in the inverter 12, the switching arrangement is connected as follows:

The fault is detected by a sensor, not shown, and signaled to a likewise not shown control of the circuit arrangement. The latter outputs control signals for opening the first switch S1 and possibly the second switch S2. The separation of the system from the supply network VN is typically carried out on a scale well below the mentioned settling time of the rotor blade adjustment. D

Simultaneously with the opening of the switch S1 and possibly S2 or after a predetermined waiting time, the pitch control of the wind-driven rotor is controlled to change the angle of attack of the rotor blades in order to convert the rotor into a spinning movement. In order to be able to deliver the output power generated in the meantime from the disconnection of the supply network VN until complete transfer of the rotor to the spin position, the closing of the third switch S3 is effected by the controller. For this purpose, two alternative embodiments of the switch S3 are conceivable. It can be designed as a normally open contact, is then open in the normal state of the switching arrangement and is actuated by a corresponding control signal (active) to close. Alternatively, the switch S3 can also be designed as normally open in the open position, which automatically falls when detected power failure.

After closing the switch S3, the electric output power of the generator G is removed from the equivalent load R1. The resistances of the equivalent load R1 can be dimensionally adjustable, so that they are designed either to a partial load of the rated load, the rated load, but also a higher load than the rated load, z. B. up to 1, 5 times the rated load. Ideally, the resistances are set such that the equivalent load substantially corresponds to the load of the supply network VN at the time of its disconnection.

By providing the substitute load can thus be avoided on the mechanical side speed increase and consequent mechanical stresses. On the electronic side voltage increases and as a result of overvoltages can be prevented. The switching group 20 therefore has the function of a brake chopper and can be decoupled by opening the switch S3 again, as soon as the torque generated by windangströmömten rotor has dropped by the made pitch under a predetermined limit.

The opening of the switch S3 is effected by the controller even if a temperature monitoring, not shown, the equivalent load R1 determines that the temperature of the resistors due to the high dissipatively converted electrical energy reaches a predetermined (critical) temperature limit, so as not to damage the

Replacement load R1 comes. With regard to the technical design of the switch S1 also several designs are conceivable. It can be designed, for example, as a fuse load disconnector or as a circuit breaker. In particular, the use of a power contactor with protection is also intended. It is also possible to use power-electronic components with a switching function, in particular with regard to the protection and monitoring aspects of the entire switching group. In particular, the use of insulated gate bipolar transistors (IGBTs) is intended. Of course, the switch S3 is designed in accordance with three-phase conductor connection L3 as a triple switch. With regard to their nominal values, the proposed switches are generously designed in order to switch the high voltages in the line branch L1, L3, which occur when the switch S1 is disconnected, to the equivalent load R1 in a failsafe manner, without a malfunction of the switch S3 having to be obtained.

Claims

oPatentansprüche:

1. A method for operating a wind turbine at a load formed by an electrical supply network, wherein in a normal state of the wind turbine, the electrical output of its driven by its wind rotor rotor electric generator (G) is removed from the supply network (VN), and wherein the Wind energy plant is transferred to a safe state on the occurrence of a failure of the power take-off,

characterized in that the wind turbine is provided with a substitute load (R1) from which the decrease in the output power of the generator (G) is maintained for a transitional time occurring during its transfer from its normal state to its safe state.

2. The method according to claim 1, characterized in that the wind turbine is separated at the onset of the disturbance of the supply network and the equivalent load is connected directly to the output of the generator.

3. The method according to claim 1 or 2, characterized in that the replacement load emits the supplied electrical power as dissipation heat.

4. The method according to claim 3, characterized in that the temperature of the substitute load is monitored and when exceeding a predetermined limit, the decrease in the output power of the generator is stopped.

5. Circuit arrangement (G, 10, 20) for operating a wind energy plant on a load formed by an electrical supply network (VN), with a drivable by a wind driven rotor of the wind turbine electric generator (G), at whose electrical output from him can be removed, an electrical input (12) connected on the input side of the generator (G) and on the output side to the supply network, and a safety device (10, 20) monitoring the decrease of the electrical output power of the generator (G) ), by which the wind turbine is switched from a normal state in which the output power of the generator of the supply network (VN) is removed, in a safe state on the occurrence of a power failure. feasible, characterized in that the wind turbine of the safety device (10, 20) separable from the supply network for a transient occurring during its transition from its normal state to its safe state and the output of the generator (G) to a replacement load maintaining the power loss ( R1) is connectable.

6. Circuit arrangement according to claim 5, characterized in that the substitute load is a dissipative resistance arrangement (R1).

7. Circuit arrangement according to claim 6, characterized in that the replacement load (R1) is provided with a temperature monitoring.

8. Circuit arrangement according to one of claims 5 to 7, characterized in that the substitute load (R1) is arranged in the tower base of the wind turbine.

9. Circuit arrangement according to one of claims 5 to 8, characterized in that the generator (G) is a via a full converter to the supply network (VN) coupled synchronous generator.

10. Circuit arrangement according to one of claims 5 to 8, characterized in that the generator (G) is an asynchronous machine.

11. Circuit arrangement according to one of claims 5 to 10, characterized in that between the output side of the inverter (12) and the supply network (VN), a first switch (S1) is provided, through which the separation from the supply network (VN) can be effected.

12. Circuit arrangement according to one of claims 5 to 1 1, characterized in that between the output of the generator (G) and the input side of the inverter (12) a second switch (S2) is provided.

13. Circuit arrangement according to one of claims 5 to 12, characterized in that between the output of the generator (G) and the replacement load (R1), a third switch (S3) is provided, through which the connection of the equivalent load (R1) to the genes - Rator (G) is effected.

14. Circuit arrangement according to one of claims 5 to 13, characterized in that the generator (G) is a three-phase generator and the equivalent load (R1) has load resistors connected in star configuration.

15. Circuit arrangement according to one of claims 5 to 14, characterized in that the generator (G) is a three-phase generator and the equivalent load (R1) has load resistors connected in a triangular arrangement.