Abstract:
Controller for a blade adjustment angle for at least one rotor blade of a wind power plant, in which a first controller branch is switched for the determination of the blade adjustment angle depending on the operating states of the wind power plant, wherein at least one differentiating member is provided in the switched first controller branch.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wind power plants with a controller of the blade adjustment angle are known. The controller of the blade adjustment angle makes it possible to balance the power and torque fluctuations of the wind power plant. The effectiveness with respect to the reduction of load peaks depends decisively on the reaction time of the controller, i.e. on the blade adjustment speed. Due to the inertia of the mass to be moved and because an overload of the actuating elements needs to be avoided, the blade adjustment angle controller is not in the position to react to short-term fluctuations in wind speed (see Erich Hau, Windkraftanlagen [Wind Power Plants], 3 rd  Edition, Springer Verlag, Chapter 6.3), the entire contents of which is incorporated herein by reference. 
         [0004]    With the demands on wind power plants due rotor blade diameters that are constantly increasing in size, the previous pitch controller approaches can no longer be used. The controller becomes increasingly slow so that power and torque deviations in the case of large rotor blade diameters of future wind power plants cannot be effectively corrected. 
         [0005]    The object of the invention is to provide a controller for the blade adjustment angle of at least one rotor blade that permits an effective regulation for a large rotor blade diameter without overloading the actuating elements and that can simultaneously be used for wind power plants with smaller rotor blade diameters. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The controller according to the invention serves to regulate a blade adjustment angle for at least one rotor blade of a wind power plant. Occasionally, this controller is also called a blade adjustment angle controller or pitch controller for short. In the case of the controller according to the invention, a regulation takes place, in which, depending on an operating state of the wind power plant, a first controller branch is switched on for the determination of the blade adjustment angle. With the switchable controller branch, the controller of the blade adjustment angle according to the invention can perform two different regulation processes for the target value determination of the blade adjustment angle depending on an operating state of the wind power plant. According to the invention, at least one differentiating member is provided in the first controller branch, which permits a fast and dynamic regulation even in the case of large rotor blade diameters. Through the switching on of the first controller branch with its at least one differentiating member, it is possible to change the controller behavior depending on the operating state. The special advantage of the controller according to the invention is also that it can be used both for wind power plants with smaller rotor blade diameters and, through suitable selection of the operating state, which triggers a switch, for wind power plants with large rotor blade diameters. 
         [0007]    In the case of a preferred embodiment of the controller according to the invention, a regulation of the blade adjustment angle takes place in a first operating state via a second and a third controller branch. The first operating state is preferably defined as a partial load mode of the wind power plant. In partial load mode of the wind power plant, it does not work with the nominal power, but is instead operated with a lower power value. 
         [0008]    In a preferred embodiment of the controller according to the invention, a first predetermined switch-over value is available for a generator and/or a rotor speed. A measured actual value for the generator and/or rotor speed is compared with the first predetermined switch-over value. If the actual value is less than the switch-over value, then the controller according to the invention works with the second and third controller branch. In the case of the preferred embodiment of the controller according to the invention, a regulation takes place exclusively via the second and third controller branch for speed values less than the first switch-over value. In the range of the low speeds, a regulation can take place in the generally known manner via the second and third controller branch. This embodiment of the invention is based on the knowledge that, in the case of high speeds, a faster, more dynamic regulation of the blade adjustment angle is possible than in the case of lower speeds, in which a too frequent correction of the pitch angle is undesirable. Furthermore, the switch-over also makes it possible, depending on a switch-over value for the generator and/or rotor speed, to use the controllers used up until now and modified for the wind power plants in wind power plants with large rotor blade diameters, which require dynamic regulation for high speeds. 
         [0009]    In the case of the controller according to the invention, a regulation of the blade adjustment angle also takes place via the first controller blade, if a second operating state is determined. The second operating state is preferably present in full load mode of the wind power plant. The second operating state can also be present for a transition range from partial load mode to full load mode. 
         [0010]    A second predetermined switch-over value for the generator and/or rotor speed is preferably specified in the controller. The second switch-over value is compared with an actual value for the generator and/or rotor speed. If the actual value for generator and/or rotor speed is greater than the second switch-over value, the first controller branch switches to the second and third controller branch. The switching can also include the fact that one or both of the previously used controller branches are no longer used. The first and second switch-over value can have the same value. 
         [0011]    In a particularly preferred embodiment, a proportional filter coordinated with the power train oscillations is provided in the second controller branch. The proportional filter suppresses the oscillations in the power train, i.e. speed deviations in the rotor shaft, a transmission and potentially in a coupling. The signals of the second controller branch are also preferably supplied to the output of the controller in addition to the signals of the third controller branch. 
         [0012]    The third controller branch, which is preferably always in use regardless of the operating states of the wind power plant, has an integration member, with which the regulation difference supplied to the controller is integrated. 
     
    
     
       BRIEF DESCRIPTION OF THE VIEW OF THE DRAWING 
         [0013]      FIG. 1  is a schematic block diagram of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    While this invention may be embodied in many different forms, there are described in detail herein a specific preferred embodiment of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiment illustrated 
         [0015]      FIG. 1  shows a schematic view of the structure of the pitch controller to which an actual value  10  of the generator speed is supplied. The target value  12  of the generator speed is subtracted from the actual value of the generator speed in order to form an error variable  14 . The error variable  14  is supplied to the controller  16 . The signal on the controller output  18  is converted to an output variable  25  of the blade adjustment angle via a proportional amplification  20  and a characteristic field  22 . An adjustment of the blade adjustment angle takes place depending on the converted output variable  25 . 
         [0016]    The controller  16  has an integrating member  24 , which amplifies the signals in an integrating manner regardless of the operating state of the wind power plant. In a second controller branch  26 , the supplied signals are filtered through a proportional filter  28 . The proportional filter  28  consists of a band-stop filter  30  and a differentiating member  32 . The band-stop filter  30  is designed such that oscillations in the power train are suppressed before they are transferred to the differentiating member  32 . The signals are subsequently amplified via a proportional member  34  and are forwarded to the output of the controller. 
         [0017]    The first controller branch can be seen in the middle of the controller shown. The first controller branch has two series-connected differentiating members  36  and  38  and a proportional member  40 . A switch  43 , which switches depending on the actual value of the generator speed, can be provided between the differentiating members  36  and  38 . A query of the threshold value  42  checks for the switching whether the actual value of the generator speed is greater than a predetermined threshold value. If the test shows that the actual value is less than the threshold value, then differentiating members  36  and  38  are connected with each other via switch  43 . On the other hand, if the current value of the generator speed is greater than the threshold value, the differentiating member  38  is connected with the output of the proportional filter  28 . 
         [0018]    Furthermore, a second switch  44  is provided in the second controller branch, making it possible to connect the first controller branch with the controller output  18  in production mode. 
         [0019]    When the controller according to the invention is used, the following process takes place: 
         [0020]    The wind power plant always works with open switch  44 , i.e. rotor blades with normal rotor blade lengths are used. The overall operation of the wind power plant always takes place via the third controller branch (the integrating member  24 ) and the second controller branch  26 . Due to the proportional filter  28 , the controller is insensitive to the oscillations of the power train. At the same time, time constants of the differentiating member  32  are selected such that a slow regulation takes place. Switch  43  has no effect in this type of operating. 
         [0021]    The wind power plant works with closed switch  44 , i.e. rotor blades with large rotor blade lengths are used. If the actual value  10  of the generator speed is below the predetermined threshold value  42 , the output of the first differentiating member  36  is fed over switch  43  and the first controller branch with the differentiating members  36 ,  38  contributes to the controller result. In this state, the second controller branch  26  also delivers a result via the controller output  18 . The series connected differentiating members  36 ,  38  allow the selection of time constants, which permit a fast regulation, in particular for switching the wind power plant to the network, in which the regulation of the speed only takes place via the pitch controller. Since the first controller branch is independent of the filtered values of the proportional filer  28 , a direct regulation takes place here, which permits in this working range a reliable and fast compensation of oscillations of the generator speed. 
         [0022]    The wind power plant works with closed switch  44 , if the wind power plant is equipped with long rotor blades. If the actual value  10  of the generator speed is higher than the threshold value  42 , then production mode is present and the signal processing takes place via the integrating member  24  and the second controller branch  26 . Due to the proportional filter  28 , the second controller branch is insensitive to the oscillations of the power train. At the same time, time constants of the differentiating member  32  are selected such that a slow regulation takes place. The switch  43  connects the output of the proportional filter  28  with the input of the differentiating member  38  and the output signals of the proportional filter  28  are supplied to the output  18  of the controller via the differentiating member  38  and the proportional member  40 . The additional differentiating member  38  now allows the provision of a time constant, which permits a fast reaction of the controller to the supplied signals. The effects of the power train oscillation are thus attenuated. However, the regulation remains dependent on the filtered values of the proportional filter  28 . 
         [0023]    The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims. 
         [0024]    Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim  1  should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below. 
         [0025]    This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.