Method for controlling wind power plants

Abstract

A method for supplying electrical energy into an electrical supply network by means of a wind power plant or wind farm, where the wind power plant or wind farm converts kinetic energy from wind with variable speed to electrical energy, the wind power plant or wind farm is prepared for supplying active power and reactive power and the reactive power to be fed in is set based on the wind velocity.

Claims

1. A method comprising: supplying electrical energy into an electrical supply network by a wind power plant or wind farm, the supplying comprising: using the wind power plant or wind farm, converting kinetic energy from wind with variable wind velocity to electrical energy; preparing the wind power plant or wind farm for supplying active power and reactive power, wherein the reactive power to be fed in is adjusted based on the wind velocity; throttling the wind power plant or wind farm for protecting the wind power plant or wind farm when the wind velocity exceeds a wind velocity threshold associated with a beginning portion of a storm; increasing the reactive power when the wind velocity exceeds the wind velocity threshold associated with the beginning portion of the storm; and decreasing the active power when the wind velocity exceeds the wind velocity threshold associated with the beginning portion of the storm.

2. The method of claim 1, wherein the wind velocity exceeds the wind velocity threshold, the method further comprising at least one of: increasing the reactive power as the wind velocity increases; and reducing the reactive power as the wind velocity decreases.

3. The method according to claim 1, wherein the wind velocity exceeds the wind velocity threshold at the beginning portion of the storm, the method further comprising at least one of: continuously increasing the reactive power as the wind velocity increases until the wind velocity has reached a wind velocity at an end portion of the storm, at which the wind power plant or wind farm no longer feeds active power into the supply network; and the reactive power is continuously reduced with falling wind velocity that is below the wind velocity at the end portion of the storm until the wind velocity has reached the wind velocity threshold.

4. The method according to claim 1, wherein: the wind power plant or wind farm is configured to supply a nominal active power; and at wind velocities above a mean storm wind velocity, the reactive power to be fed in has a higher value than a value of the nominal active power.

5. The method according to claim 1, wherein between a wind velocity at the beginning portion of the storm and a wind velocity at an end portion of the storm, the reactive power is set by a reactive power function that defines a relationship between the reactive power and the wind velocity, wherein the reactive power function is defined as at least one of: a first-order polynomial function; a second-order polynomial function; or a hysteresis function.

6. A wind power plant for supplying electrical energy into an electrical supply network using the method according to claim 1.

7. The wind power plant according to claim 6, wherein the wind power plant comprises: a generator configured to generate a generator nominal power; and a feed-in device for supplying the active power and the reactive power, wherein said feed-in device is configured to supply a maximum feed-in current that is greater than a feed-in current for supplying the generator nominal power.

8. The wind power plant according to claim 7, wherein the feed-in device includes a plurality of feed-in units, wherein the wind power plant includes more feed-in units than is utilized for supplying the nominal power generated by the wind power plant.

9. The wind power plant according to claim 8, wherein the plurality of feed-in units are power cabinets.

10. A wind farm for supplying electrical energy into a supply network, wherein the wind farm uses the method according to claim 1 for supplying electrical energy into an electrical supply network.

11. The wind farm according to claim 10, wherein the wind farm comprises: a central control unit for controlling the wind farm, and wherein the method steps for performing the supplying are implemented on said central control unit.

12. The wind farm according to claim 10, wherein the wind farm is configured to supply a larger current than the current required for supplying a maximum active power for which the wind farm is designed.

13. The wind farm according to claim 10, comprising a plurality of wind power plants.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention is now described in more detail below using embodiments as examples with reference to the accompanying figures.

(2) FIG. 1 shows the schematic perspective view of a wind power plant.

(3) FIG. 2 shows the schematic view of a wind farm.

(4) FIG. 3 shows the schematic view of a diagram that shows the interdependencies between reactive power Q to be fed in and active power P to be fed in and the wind velocity according to one embodiment.

(5) FIG. 4 shows the schematic view of the composition of a wind power plant with several feed-in units.

DETAILED DESCRIPTION

(6) FIG. 1 shows a wind power plant 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is located on the nacelle 104. When in operation, the rotor 106 is brought to a rotating movement by the wind and thereby drives a generator in the nacelle 104.

(7) FIG. 2 shows a wind farm 112 with, for example, three wind power plants 100, which may be the same or different. The three wind power plants 100 are thus representative of a basically random number of wind power plants of a wind farm 112. The wind power plants 100 provide their power, in particular the generated electricity, via an electrical wind farm network 114. The currents or, respectively, powers generated by the individual wind power plants 100 are added up. Most often, a transformer 116 will be provided, which transports the voltage at the wind farm to then feed it into the supply network 120 at the supplying point 118, which is also generally referred to as a PCC. FIG. 2 is merely a simplified illustration of a wind farm 112, which does not show, for example, a control, although a control exists, of course. Also, the wind farm network 114 may be designed differently, including, for example, a transformer at the output of each wind power plant 100, to mention just one other embodiment.

(8) In the diagram of FIG. 3, the wind velocity V.sub.W is plotted on the abscissa, wherein the illustration commences with the wind velocity at the beginning of a storm V.sub.SA. Here, weaker wind ranges are irrelevant to the following explanations.

(9) Reactive power Q and active power P are plotted on the Y-axis. The Y-axis extends from 0 to the nominal active power P.sub.N. In this respect, the scaling for reactive power Q and active power P is the same, meaning that 1 watt (W) equals 1 volt-ampere reactive (VAr).

(10) The diagram shows that the active power P has the nominal power P.sub.N for a wind velocity at the beginning of a storm V.sub.SA. With increasing wind velocity, said active power drops continuously to 0 until wind velocity at the end of a storm V.sub.SE is reached.

(11) Reactive power Q, on the other hand, increases continuously from wind velocity at the beginning of a storm V.sub.SA to wind velocity at the end of a storm V.sub.SE. In this example, it has reached the maximum reactive power Q.sub.max that can be fed in. Preferably, it can maintain such value despite increasing wind velocities.

(12) A dashed-line course shows an alternative dependence of reactive power Q on wind velocity V.sub.W, where the reactive power Q for wind velocity at the beginning of a storm V.sub.SA is already greater than 0. This course also shows that the reactive power Q has reached the nominal power value P.sub.N already at mean storm wind velocity V.sub.SM. In this case, the reactive power Q may have shown a steady value, for example in slightly lesser wind velocity conditions than the wind velocity at the beginning of a storm V.sub.SA, which was set possibly due to a network state.

(13) In this respect, FIG. 3 shows two variants of how to provide the reactive power based on the wind velocity for reactive power Q or Q. The designation Q was used only to illustrate a variant. Apart from that, said Qjust like Qspecifies the to-be-fed-in reactive power of the respectively described embodiment.

(14) FIG. 4 shows the schematic view of a wind power plant 1 featuring a generator 2. Said generator 2 is designed, for example, for a nominal power of 2 MW. The depicted embodiment features a rectifier 4 that rectifies the entire power of generator 2 and leads it to the switch cabinets or feed-in units 8 via bus-bar 6.

(15) All of the feed-in units 8 are thus connected to the same bus-bar 6, and each of these feed-in units 8 generates three-phase alternating current that is fed to output line 10. Supplying from output line 10 into the schematically shown supply network 14 takes place via a transformer 12.

(16) Each feed-in unit or switch cabinet 8 is designed for supplying three-phase current that would equal the current that would be reached if a mere active power of 1 MW were fed in. Three of these 1-MW switch cabinets are provided for, which are hence oversized merely for supplying active power for the 2-MW generator 2. With these switch cabinets 8, it is possible to feed in the full active power of 2 MW and to also feed in reactive power. It is, moreover, possible to feed in a reactive power Q of more than 2 MVAr if only the fed-in active power is correspondingly small. With these three switch cabinets 8, one can theoretically feed in up to three MVAr if no active power is fed in.