METHOD FOR THE OPERATION OF WIND POWER PLANTS

Abstract

Method for the operation of a wind power plant with controllable effective power, wherein an idle power interval defined by a minimum idle power and a maximum idle power is assigned to each value of the effective power and the actual idle power can be controlled within this interval, characterized in that the effective power is reduced when a target idle power lies outside of the idle power interval assigned to the current effective power.

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The invention is explained in greater detail below based on an exemplary embodiment shown in two figures.

FIG. 1 shows a diagram with the assignment of idle power intervals to the effective power,

FIG. 2 shows a diagram with time progression of the effective and idle power when using the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

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.

FIG. 1 shows the connection between the idle power Q and effective power P.

The effective power P is shown on the abscissa. The shown effective power range begins at zero and extends up to a maximum effective power, which may exceed the nominal power of the wind power plant by a certain amount. On the ordinate, a maximum idle power Q (curve 2) and a minimum idle power Q (curve 4) are assigned to each effective power P. The amounts of the minimum and maximum idle powers assigned to a certain effective power value in curves 2 and 4 correspond with a specified or registered idle power, which corresponds with a capacitive or inductive idle power. The amounts must not be equal.

The curves 2 and 4 are identified taking into consideration the permissible current carrying capacity of all relevant components of the wind power plant. The current carrying capacities and the thermal capacities of the rotor and stator coils as well as the converter are incorporated in particular. As a result, the curves 2 and 4 show a progression that approximates a root function. One would obtain a progression that is exactly equal to a root function if one would only include a constant apparent power when calculating the permissible idle powers.

FIG. 2 shows the mode of operation of the power control system over time.

The dashed curve 10 shows a maximum effective power P_max resulting from the amount of wind power. In the time segment shown in the diagram, this theoretically possible maximum effective power includes, beginning from relatively low values, a maximum around point t₂ and then drops again.

In line with the correlation between the effective power and the maximum or minimum idle power shown in FIG. 1, the two dotted curves are shown in the diagram in FIG. 2 starting from curve 10 for the minimum idle power Q_min (curve 12) and the maximum idle power Q_max (curve 14). Thus, an idle power interval depending on the maximum possible effective power P_max (curve 10) between the two curves 12 and 14 is assigned to each point in time. It is easy to see that, in the case of a lower maximum possible effective power P_max, this interval is greater than in the case of a comparatively large maximum possible effective power P_max.

Furthermore, a specified target idle power Q_target (curve 16) is shown as a thin solid line 16 in the diagram. This target idle power corresponds with an external specification. The shown target idle power proceeded up to time t₂ at a first constant level, then increases up to time t₃ and subsequently proceeds at a second constant level.

The mode of operation of the controller according to the invention is now on the bold curves 18 and 20, which show the actual released idle power Q_actual (solid curve 18) and effective power P (dashed curve 20).

The release idle power Q_actual corresponds with the specified idle power Q_target during the entire time progression. A regulation of the released idle power to the specified target value Q_target takes place. The insignificant displacement of the two curves 16 and 18 only serves to improve recognizability.

The released effective power P only partially corresponds with the maximum possible effective power P_max. In the time interval between t₁ and t₄, the released effective power P is lower than the theoretically possible effective power P_max. The deviation begins at point in time t₁. At this time, the upper limit of the attainable idle power interval shown by curve 14 for the maximum possible effective power P_max drops below the specified idle power Q_target (curve 16). Thus, the effective power P_max is reduced with respect to the maximum possible effective power P_max. It runs up to time t₂ at a constant value. This value corresponds with that of the effective power value, in which the upper limit of the idle power interval corresponds with the target idle power, i.e. with the value shown at time t₁. The target idle power is increased beginning with time t₂. This required target idle power cannot be achieved with the effective power P released at time t₂, because it lies outside of the idle power interval assigned to this effective power. Thus, the released effective power P by time t₃ is further reduced. The released idle power Q_actual can thus be increased according to the target value Q_target.

At time t₃, the specified target idle power assumes a constant value again. Accordingly, the effective power P also remains at a constant level, which is compatible with the required target idle power. At time t₄, the maximum creatable effective power P_max drops to the current value P at time 4 as a result of a reduced amount of wind. The maximum possible effective power P_max is subsequently reduced as a result of the decreasing amount of wind. In this case, the actual effective power P provided follows the maximum possible level P_max. The released idle power Q_actual thereby remains at the level of the target idle power value, which as of time t₄ again lies within the idle power interval assigned to the maximum possible effective power P_max.

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.

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.

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.

Claims

1. Method for the operation of a wind power plant with controllable effective power, wherein an idle power interval defined by a minimum idle power (12) and a maximum idle power (14) is assigned to each value of the effective power (20) and the actual idle power (18) can be controlled within this interval, characterized in that the effective power (20) is reduced when a target idle power (16) lies outside of the idle power interval assigned to the current effective power.

2. Method according to claim 1, characterized in that the actual idle power is controlled to the maximum idle power or to the minimum idle power of the idle power interval assigned to the current effective power and the effective power is not reduced when the target idle power is outside this idle power interval and the current effective power is smaller than a specified minimum effective power.

3. Method according to claim 1, characterized in that the assignment of the minimum idle power and the maximum idle power to each value of the effective power takes place based on the maximum current carrying capacity of a component of the wind power plant, wherein the dependency of the maximum current carrying capacity of the components is taken into consideration by at least one operating variable of the wind power plant.

4. Method according to claim 1, characterized in that the assignment of the minimum idle power and the maximum idle power to each value of the effective power takes place based on the maximum current carrying capacity of a component of the wind power plant, wherein the dependency of the maximum current carrying capacity of the component is taken into consideration by at least one environmental condition of the wind power plant.

5. Method according to claim 1, characterized in that the minimum idle power and the maximum idle power for each effective power are calculated from the permissible current carrying capacity of the stator and rotor coils of the generator of the wind power plant.

6. Method according to claim 1, characterized in that the minimum idle power and the maximum idle power for each effective power are calculated from the permissible current carrying capacity of all current-carrying components of the wind power plant.

7. Method according to claim 1, characterized in that a control parameter is provided, which can accept two different values, wherein the method is executed for a first value of the control parameter and the effective power may be reduced, while no reduction of the effective power takes place for a second value of the parameter.