Wind turbine with pitch controller

p0001The present invention relates to a wind power plant with at least one rotor blade, the blade pitch is adjustable over a blade pitch control. Furthermore, the wind turbine has a generator-converter unit, wherein at least one electrical quantity via a converter regulator is adjustable. The wind power plant has a power train, which begins with a rotor which carries the at least one rotor blade. The drive train continues with a rotor shaft, which is connected with the rotor. The rotor shaft is coupled to a gear, opens the output shaft of the generator shaft into the generator.

p0002The blade pitch angle of a rotor blade is fachsprachlich referred to as "pitch angle", so that the blade pitch control is also called "pitch control".

p0003The power of the wind turbine is controlled in the rated load range significantly above the speed setpoint. The control takes place via one converter, which is sometimes referred to as Hauptumrichterregler. The regulatory approach is currently used in wind turbines considered as the source for the converter regulator the generator speed. The accuracy of the measured generator speed is highly dependent on various factors, because the measured generator speed usually drivetrain vibrations, elasticities of transmission, vibrations of the machine carrier and the tolerances are superposed in a possible provided clutch. So far, a strong filtering and damping of the measured values ​​was to hide these factors in the generator speed, made. In particular, the measured values ​​of the generator speed were smoothed and suppressed in certain frequency ranges partially. In the past, as filtered values ​​of the generator speed were also applied to a Blatteinstellwinkelregler to adjust the blade pitch depends here on the generator speed. Particularly when wind turbines with large rotor diameter, the filtered values ​​of the generator speed result in a slow response in controlling the blade pitch.

p0004The invention has the technical object to provide a wind turbine with a blade pitch control for the available that allows dynamic control of the blade pitch without unnecessary is that frequently intervened in the control of the inverter.

p0005According to the invention the object is achieved by a wind power plant with the features of claim. 1 Advantageous embodiments form the subject matters of the subclaims.

p0006The wind power plant according to the invention has at least one rotor blade, the blade pitch is adjustable over a blade pitch control. Furthermore, the wind power plant according to the invention is equipped with a generator-converter unit, wherein at least one electrical variable on one converter generated is adjustable. The generator-converter unit is not necessarily formed as a constructive or structural unit, but merely referred to the generator and inverter, which cooperate with each other to provide the desired electrical quantity. The wind power plant according to the invention is further equipped with a drive train, at the front end, a rotor with the disposed at least one rotor blade and opens with its other end in the generator inverter unit. The drive train thus extends from the rotor toward the generator.

p0007According to the invention, the wind turbine is equipped with two speed detection units to the drivetrain. A first rotation speed detection unit is provided on the drive train near the front end. The second rotation speed detection unit is provided on the drive train near the generator-converter unit. In the inventive design wind turbine, the measured speed of the first rotational speed detection unit to the Blatteinstellwinkelregler and the measured speed of the second rotation speed detection unit to the converter regulator located at each as an input to the controller. The controllers perform the determination of the pitch or the control of the converter, irrespective of the respective measured input variables of the speed and the other, necessary for controlling input variables. In the embodiment of the wind turbine according to the invention the first rotation speed detection unit detects the rotational speed to the drive train or to its rotor shaft substantially independently of interfering influences, and vibrations in the drive train, so that the detected speed signals largely present without interference. The second rotational speed detection unit to the drive train near the generator-converter unit detects a value for the generator speed indicating the speed of the generator and can be set via the converter regulator to control the inverter.

p0008In a preferred embodiment of the wind turbine according to the invention is the first speed detection unit, preferably a high-resolution speed detection unit, arranged at the front end of the drive train. Preferably, the rotational speed of the rotor shaft is detected optically with the first rotational speed detection unit, wherein a resolution of more than 2,000 pulses per revolution takes place. The first rotational speed detection unit is in this preferred embodiment, a high-resolution, optical pulse counting, which is located at the front end of the drive train. The use of such a high resolution optical pulse counting arrangement makes it possible to detect the rotational speed of the rotor shaft in the region of the rotor precisely.

p0009The second rotational speed detection unit is preferably arranged between an output shaft of a transmission and an input shaft of the generator or directly at the generator. Appropriately, the measured speed of the second rotational speed detection unit for the converter regulator is filtered by a signal processing to remove noise, for example, from the measured values ​​for the generator speed. By the signal processing is preferably carried out a smoothing of the measured speed values, it being also provided that certain frequencies of drive train vibrations are filtered out of the measured speed values.

p0010Preferably, an additional speed monitoring unit is provided in the wind power plant, which compares the measured speed values ​​with each other and at a deviation of the measured speed values, a control signal to settle, indicating an error in the drive train. The speed monitoring unit performs a plausibility check of the measured speed values, it being understood that the ratio of the transmission when comparing the speed values ​​is taken into account. The speed monitoring unit allows to detect a transmission error or a defect in the clutch. In the speed monitoring unit, the measured speed values ​​are compared by the gear with each other in consideration of the gear ratio.

p0011In a particularly preferred embodiment is where Blatteinstellwinkelregler addition to the output signal of the second rotation speed detection unit. This signal input to the Blatteinstellwinkelregler allows a control of the blade pitch angle may additionally or alternatively be carried out depending on the measured speed values ​​of the second rotation speed detection unit. Preferably the Blatteinstellwinkelregler for predetermined operating conditions of the wind turbine blade pitch regulates solely on measured values ​​of the second rotational speed detection unit. In one development of the invention, the blade pitch controller intervenes to control the blade pitch back to measured values ​​of the first rotational speed detection unit when the measured speed of the first or second rotational speed detection unit has exceeded a predetermined threshold. Based on the operating conditions of the wind turbine is the speed-dependent switching to the Blatteinstellwinkelregler that above a certain minimum speed of the rotor shaft, the regulation of the blade pitch depending on the measured at the first rotation speed detection unit speed values.

p0012The wind power plant according to the invention is illustrated below with reference to two figures:<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>shows the schematic structure of the drive train with two speed detection units and</dd><dt>Fig.2</dt><dd>a flowchart for switching between the measured speed values.</dd></dl>

p0013<figref idrefs="f0001">figure 1</figref> shows a schematic view of the drive train of a wind turbine with a rotor 10 and two rotor blades 12. The rotor 10 includes a rotor shaft 14 with a clutch 16 and a transmission 18 is connected. The transmission has a gear ratio, the rotational speed of the rotor shaft is set high. The output shaft 20 of the transmission 18 ends in a generator 22. The shaft 20 is hereinafter referred to as a generator shaft 20 or as a quick wave.

p0014At the generator 22, an incremental encoder 24 is arranged, which detects the rotational speed of the generator shaft 20 or a shaft in the generator 22nd The output of the incremental encoder 24 is further passed through a signal conditioner 26 to the Hauptumrichterregler 28, via the regulation of the inverter and possibly. Also the generator. Governed this is the fed into the grid active power of the generator-converter unit.

p0015Also in <figref idrefs="f0001">figure 1</figref> shown is the incremental encoder 30 which is arranged at the front end of the rotor shaft 14 in the rotor 10th In the incremental encoder is a high-resolution incremental encoder, which can, preferably even 16 bits per revolution, optically detect 14 bit per revolution. The measured speed of the incremental encoder 30 is a pulse transformer 32 and an evaluation unit 34 as n_red forwarded to a pitch control 36th The pitch control 36 generates the appropriate signal for adjusting the blade pitch angle φ (n_red, ...). If no evaluation 34 for n_red are used, the rotor speed can duct 35 n_red also lie directly on the control unit 42nd

p0016in addition, in <figref idrefs="f0001">figure 1</figref> is a speed monitoring system represented 38, against which the measured rotor speed 30 and the measured generator speed 24th The speed monitoring system 38 compares, taking into account the gear ratio in the transmission 18, the two speed values, and sets the event of deviations over the link 40 from an error signal to a control unit 42nd The control unit 42, for example, in response to the error signal out that the measured speed values ​​do not relate to each other in the right proportion, trigger a shutdown of the plant.

p0017In operation of the wind turbine, the controller 42 fulfills yet another object. The control unit 42 checks whether the measured rotor speed of the incremental encoder 30 is to be applied to the regulator 36 this. To this end, checks the control unit 42 as shown in<figref idrefs="f0002">figure 2</figref> shown that the generator speed which has been detected at the encoder 24, is below a predetermined threshold. In<figref idrefs="f0002">figure 2</figref> is exemplified as such a threshold 700 U / min displayed. Depending on the design and type of the wind turbine, but other values ​​can be used as a threshold value for the generator speed. In a first measurement, it has proven advantageous, the threshold for the generator speed selected such that the wind turbine when reaching the threshold produces about two thirds of its nominal power.

p0018In the event that the generator rotational speed n_gene is less than the predetermined threshold value of 700 U / min, is applied to the pitch control the generator speed as an input variable to φ (n_gene, ...). If the generator speed n_gene greater than or equal to the predetermined value of 700 U / min, the pitch control works depending on the measured rotor speed φ (n_red, ...). In<figref idrefs="f0002">figure 2</figref> is the respective dependence of the pitch control shown, φ on the pitch angle as a function of n_gene or by n_red, Here, of course, to take into account the current transmission ratio of the transmission. The corresponding query 44 takes place in the control unit 42nd

p0019During operation of the wind turbine at first a pitch control in a conventional manner in which the pitch control is carried out depending on the measured and appropriately filtered generator speed. If a certain minimum speed is exceeded at the generator shaft 20, so the rotor shaft 14 rotates fast enough to reliably determine the incremental encoder 30, the speed values ​​on the rotor shaft. In this case, the control unit 42 and a pitch control is effected depending on the measured via the incremental encoder 30 rotating speed of the rotor shaft, which is substantially free from vibrations in the drive train. The incremental encoders 24 and 30 are both configured as a high-resolution incremental encoders that allow accurate detection of the rotational speed.