(19) (10) DE 103 35 575 B4 10/06/2005

Description

[0001] The invention relates to an emergency operating device for adjusting the rotor blades for a wind power system. A wind power system exhibits rotor blades, which are mounted on a hub of a rotor shaft and which are connected to a generator. The positioning of the rotor blades about their longitudinal axis can be varied by means of a motor.

Background Art

[0002] Modern wind power systems in a power range of approximately 500 kW with preferably horizontally designed rotor shaft have adjustable rotor blades. As a result, the attack area of the wind velocity can be adapted; and an approximately constant power of the wind power system can be set. Thus, wind power systems of this type can still be operated at comparatively high wind velocities. Upon reaching a threshold wind velocity, for which a wind power system is designed, it is necessary to limit the power. In this way damage to the wind power systems due to mechanical overloads can be avoided.

[0003] Another case of a mechanical loading on a wind power system is the possible absence of the electric load owing to the main generator. The reason for this emergency situation may be, for example, the failure of the power grid, the converter or also the main generator itself. Therefore, it is possible for the rotor shaft to accelerate very quickly due to the now absent load moment of the main generator. A mechanical overload of the wind power system due to inadmissibly high speeds would be the result. In order to avoid such a loading situation, the standard procedure is to turn the rotor blades or just one rotor blade into a so-called "flag position". All of the rotor blades are rotated in an advantageous way out of the wind. At the same time either the front edge or the rear edge of the rotor blade profile is rotated into the wind, so that it is no longer possible to generate a driving lift at the rotor blade profile.

[0004] The device for adjusting the rotor blades into the flag position has to be designed reliably from an engineering aspect. Consequently it has to be guaranteed that, for example, even in the emergency situation of a power grid failure, the energy supply for the adjusting drives of the rotor blades will be guaranteed. For this reason it is known to use an independent auxiliary energy device in the form of an accumulator as the energy storage unit, which in the event of an error is connected directly to the servomotors of the actuators. Upon reaching the flag position, the actuators are isolated, for example, from the accumulator by means of limit switches.

[0005] Therefore, in emergency situations, such as in the absence of the electrical power supply, it must be guaranteed with certainty that the position of the rotor blades can be adjusted. Such an adjustment is necessary, for example, even when too high a wind is acting on the blades. The motor(s) for adjusting the position of the rotor blades of the wind power system is/are fed, for example, by means of a converter. The converter exhibits a rectifier, an intermediate circuit and an inverter. The converter is fed by means of an electric power supply grid. For the emergency operation of the adjustment of the rotor blades of the wind power system, the intermediate circuit of the converter is fed by means of an accumulator, such as a lead gel accumulator. In this way a self-reliant, power grid-independent operation is guaranteed. The accumulator is chargeable by means of a power supply unit, which constitutes a rectifier. This charging power supply unit increases not only the cost of a wind power system, but also the system's susceptibility to errors, because each additional component of the wind power system enhances the failure probability of the whole wind power system. The drawback is that for rare situations of an error or for emergency situations a charger has to be provided for the independent energy supply - thus, for the energy storage unit - with the respective costs for the acquisition and maintenance.

[0006] The DE 200 20 232 U1 discloses, for example, a wind power system, which exhibits means for adjusting the rotor blades. In this case an actuator for adjusting at least one rotor blade is provided; and at least one auxiliary generator for uncoupling the electric energy from the kinetic energy of at least the rotor shaft is provided. Upon detection of a fault, a switch-over device conveys the electric energy of the auxiliary generator to at least one servomotor for adjusting at least one rotor blade into a flag position.

Technical Problem

[0007] The object of the present invention is to provide an emergency operating device, by means of which the failure probability of the whole wind power system is reduced and/or the costs for the wind power system are reduced.

[0008] This object is achieved by means of an emergency operating device with the features that are disclosed in claim 1. The dependent claims 2 to 6 disclose the further developments of the emergency operating device.

[0009] Furthermore, the object is achieved with a wind power system exhibiting the features disclosed in claim 7. The dependent claim 8 relates to a further development of the wind power system.

[0010] In an emergency operating device of the invention for a wind power system, the emergency operating device exhibits an energy storage unit. In this case the energy storage unit can be charged by means of a rectifier. The wind power system exhibits a power converter for feeding a direct voltage intermediate circuit. This power converter for feeding the direct voltage intermediate circuit is in the function of a rectifier a part of the converter. The converter is provided for feeding an electric motor, which is provided for adjusting the position of the rotor blade of the wind power system. The electric motor is in an advantageous manner an alternating current motor, in particular, a three phase motor, which in comparison with a direct current motor, is lighter, a feature that offers weight advantages. Furthermore, said alternating current motor is less maintenance intensive than the direct current motor. Thus, a converter exhibits a rectifier, a voltage intermediate circuit, and an inverter. According to the invention, the rectifier of the converter can be provided for both feeding the intermediate circuit in the converter mode and for charging the energy storage unit of the emergency operating device. Hence, it is possible to avoid the necessity of having to use an expensive power supply unit for charging the accumulators or also for charging a capacitor, by means of which the intermediate circuit can be backed up during an emergency operation - as a result of which, the number of error sources is reduced. The result of the elimination of a power supply unit, which is used as a charger and which, owing to the surrounding conditions, is susceptible, is a lower inspection and maintenance cost as well as a reduction in weight. This weight reduction is especially advantageous with respect to the wind load.

[0011] In one advantageous embodiment of the energy storage unit, this energy storage unit can be designed as an accumulator and/or as a capacitor. Ultracaps can be used advantageously as the capacitor. In this case, these ultracaps are also referred to as supercapacitors and/or as ultracapacitors. The capacitor is, for example, a single capacitor or a capacitor battery and/or a capacitor bank. The advantage of a capacitor and, in particular, an ultracapacitor is that it can be operated, as compared to the accumulator, in a broader temperature range. Furthermore, in contrast to the accumulator, the capacitor has a longer service life, requires less maintenance and does not exhibit a comparable memory effect.

[0012] In one advantageous embodiment, the energy storage unit can be charged via a charging resistor. The charging resistor serves to limit the current, when the energy storage unit is charged by way of the intermediate circuit of the converter.

[0013] The converter can also be designed with a self-commutated converter as a rectifier. In an embodiment of this type it is possible to dispense in an advantageous way with the charging resistor.

[0014] In an additional advantageous embodiment, the charging resistor can be bridged by means of a parallel circuit. The parallel circuit exhibits, for example, a diode. During the charging process, the diode blocks; and during the discharging process the electric current flows over the diode, so that during the discharging process there is hardly any voltage drop over the charging resistor; and hence, hardly any energy is lost.

[0015] In an additional advantageous embodiment, the energy storage unit can be isolated from the intermediate circuit. The isolation is produced, for example, by means of a contactor. If voltage is available at the converter, the charging of the energy storage unit can be activated by means of a contactor, which serves as switch. In this way it is guaranteed that the energy storage unit will not continuously draw a charging current.

[0016] In another advantageous embodiment the emergency operating device exhibits at least one fuse. The fuse protects the emergency operating device from currents that are too high.

[0017] One model for dimensioning an emergency operating device is discussed below with reference to one example. In this case the variables that are used are named only as examples and do not restrict any other possible dimensioning of the emergency operating device. The converter exhibits, for example, a power of 15 kW. If the converter has already, for example, double terminal connections for the intermediate circuit, then, for example, 4 sq.mm terminal connections carry the charging and/or operating current in the emergency operation. If, for example, a capacitor is provided as the energy storage unit, then the energy content of the capacitor at the design voltage is calculated as follows:

W = 1/2 CU²

When C = 1F, U = 620 V, then W = 192.2 Kws.

[0018] The capacitor backs up the intermediate circuit and can, consequently, also be referred to as the backup capacitor.

[0019] The object of the invention is also achieved by means of a wind power system, which exhibits an emergency operating device, according to one of the aforementioned embodiments. The wind power system exhibits rotor blades. In this case the rotor blades can be adjusted by means of at least one electric machine; and the electric machine is fed by means of a converter. In this case the converter exhibits a rectifier, an intermediate circuit, and a power inverter; and the emergency operating device is connected to the intermediate circuit.

Embodiment

[0020] The invention is explained in detail by means of one example with reference to the following figures.

[0021] Figure 1 depicts an emergency operating device for a wind power system, and

[0022] Figure 2 is a schematic drawing of the design of a rotor of a wind power system.

[0023] The drawing, according to Figure 1, shows an emergency operating device 1 for an electric machine 5. The electric machine 5 can be operated by means of a converter 3. This converter 3 exhibits a rectifier 11, an intermediate circuit capacitor 7 and a power inverter 9. The rectifier 11 exhibits diodes 21 in the illustrated configuration for the rectification of a three phase alternating current, which can be fed into the converter 3 by way of the supply terminals 35. The intermediate circuit capacitor 7 is connected by means of the supply terminals 37, which are designed internally in the converter 3, into the direct voltage intermediate circuit. The direct voltage intermediate circuit exhibits switches 27 and 29. Owing to these switches 27 and 29, the resistors 15 in the function of charging resistors for the intermediate circuit capacitor 7 can be connected into the intermediate circuit. If the switches 27 and 29 are closed, then the resistors 15 are short circuited. The intermediate circuit capacitor 7 is either a single capacitor and/or a capacitor battery and/or a capacitor bank - that is, multiple capacitors connected together. The emergency operating device 1 exhibits at least one energy storage unit 17. The energy storage unit 17 is, for example, an accumulator or also a capacitor and/or a capacitor bank. It is possible to use ultracapacitors in an advantageous way for the capacitors. The energy storage unit 17 can be charged by means of a charging resistor 13. In order to discharge the energy storage unit 17, there is a diode 22, which is connected in parallel to the charging resistor 13. The energy storage unit 17 is isolated from the intermediate circuit of the converter 3 by means of a switch 25. Furthermore, the emergency operating device 1 exhibits a fuse 19 on both sides of the voltage intermediate circuit. The fuse 19 protects the energy storage unit 17.

[0024] The switch 25 is advantageously a contactor.

[0025] The energy storage unit 17, which exhibits, for example, backup capacitors, is charged intelligently by means of the contactor 25. That is, the charging state is monitored; and the contactor 25 is switched correspondingly. In this case the charging resistor 13 limits the charging current. When the power grid fails, the backup capacitors feed the energy over the uncoupling diode (diode 22) into the intermediate circuit. The size of this energy storage unit can be adapted flexibly and accurately to the energy demand of the respective application and is not dependent on the rigid sizes of the prefabricated capacitor modules.

[0026] The intermediate circuit of the converter 3 can be expanded by means of the energy storage unit 17 and as a function of the switching state of the switch 25.

[0027] The expansion of the intermediate circuit by means of a capacitor module is charged by means of the precharging circuit of the converter and/or the supply unit.

[0028] The converter 3 is connected by means of throttles 23 to an external three phase supply network, which is not illustrated in Figure 1. The electric machine 5 can be used in a wind power system, for example, to adjust the rotor blades of the wind power system.

[0029] The dimensioning of the charging resistors shall be calculated with reference to one example.

[0030] On charging the capacitors, energy is converted into heat in the charging resistor R, 13. This energy matches approximately the energy to be stored. The charging resistor 13 determines the maximum current during the charging process and, thus, protects the rectifier 11 and the energy storage unit 17. Therefore, it holds: maximum current = intermediate circuit voltage / charging resistor. The charging period is determined with the charging resistor 13 and the effective capacitance C of the capacitors.

[0031] The drawing, according to Figure 2, depicts a rotor 50 of a wind power system. At the same time Figure 2 shows a hub 52 with two adjustable rotor blades 54, which are mounted on said hub. The rotor blades 54 can be adjusted about a longitudinal axis 58 in the illustrated rotational directions 56. The flag position 60, which was described in the introductory part, is shown with the dashed lines. Furthermore, the example in Figure 1 shows the bearings 62 on the hub 52 for the variable accommodation of the rotor blades 54. Inside the hub 52 each of the rotor blades 54 is connected mechanically, for example, to an electric motor 64 as the actuator for adjusting the rotor blades 54. As an alternative, it is also possible to use for the rotor blade 54 a number of actuators - an option that is not shown.

[0032] The hub 52 is connected to a rotor shaft 66, which is designed as a horizontal hollow shaft in the example shown in Figure 1. This hollow shaft is mounted rotatably by means of two bearing blocks 68, which are permanently connected to a support system 70. The support system 70 represents a rigid mechanical connection to a gondola body, which is mounted rotatably to the mast of the wind power system - a feature that is, however, not illustrated in Figure 2. Furthermore, the rotor shaft 66 is connected to an input of a gear mechanism 72 with a set of sliprings 74. A generator 78 is connected to the correspondingly translated output of the gear mechanism 72 by way of the generator shaft 76.

[0033] The two servomotors 64 are connected to the converter 3 by way of the motor lines 80. Furthermore they are connected to an electrical power supply system 84 over the slipring 74 by way of the electrical lines 82.

[0034] When the wind power system is operating under normal conditions, the two converters 2 are supplied electricity from the electrical power supply system 84 - for example, from a conventional 50 Hz/400V three phase network.

[0035] In the event of an error, the energy is fed to the electric motors 64 by way of the emergency operating devices 1, which are connected to the intermediate circuit (not illustrated in Figure 2) of the converter 3.

Patent Claims

1. Emergency operating device (1) for a wind power system, wherein the wind power system exhibits rotor blades (54), which can be adjusted by means of at least one electric motor (64), said electric motor (64) being supplied by at least one converter (3), said converter (3) exhibiting a rectifier (11), an intermediate circuit, and a power inverter, and wherein the emergency operating device exhibits an energy storage unit, which can be used to feed energy to the electric motor (64), characterized in that the energy storage unit (17) can be charged by means of the rectifier (11).

2. Emergency operating device (1), as claimed in claim 1, characterized in that the energy storage unit (17) is an accumulator and/or a capacitor and/or, in particular, an ultracapacitor.

3. Emergency operating device (1), as claimed in claim 1 or 2, characterized in that the energy storage unit (17) can be charged by means of a charging resistor (13).

4. Emergency operating device (1), as claimed in claim 3, characterized in that the charging resistor (13) can be bridged by means of a parallel circuit.

5. Emergency operating device (1), as claimed in any one of the preceding claims, characterized in that the energy storage unit (17) can be isolated from the intermediate circuit.

6. Emergency operating device (1), as claimed in any one of the preceding claims, characterized in that the emergency operating device (1) exhibits at least one fuse (19).

7. Wind power system, which exhibits an emergency operating device (1), as claimed in any one of the claims 1 to 6.

8. Wind power system, as claimed in claim 7, characterized in that the wind power system exhibits rotor blades (54), said rotor blades (54) being adjustable by means of an electric motor (64); and the electric motor (64) being fed by means of a converter (3), the converter exhibiting an intermediate circuit; and the emergency operating device (1) being connected to the intermediate circuit.

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2 sheets of drawings to follow.

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Attached Drawings

[see figure]