Method for controlling a wind power installation

Abstract

A method for controlling a wind power installation includes measuring a grid voltage of an electrical power supply grid, setting a DC-link voltage at a converter of the wind power installation depending on the measured grid voltage and using a first time constant and a second time constant, wherein the first time constant is different than the second time constant.

Claims

1. A method for controlling a wind power installation, comprising: measuring a grid voltage of an electrical power supply grid over a period of time, and setting a DC-link voltage at a converter of the wind power installation depending on the measured grid voltage and according to a first time constant over the period of time and a second time constant over the period of time, wherein the first time constant is different than the second time constant, operating the converter of the wind power installation at the DC-link voltage setting; and establishing a positive grid voltage change or a negative grid voltage change depending on the measured grid voltage, wherein the first time constant is assigned to the positive grid voltage change, and wherein the second time constant is assigned to the negative grid voltage change.

2. A method for controlling a wind power installation, comprising: measuring a grid voltage of an electrical power supply grid over a period of time, and setting a DC-link voltage at a converter of the wind power installation depending on the measured grid voltage and according to a first time constant over the period of time and a second time constant over the period of time, wherein the first time constant is different than the second time constant, operating the converter of the wind power installation at the DC-link voltage setting, and measuring an impedance of a line reactor, wherein setting the DC-link voltage depends on the measured impedance.

3. The method for controlling a wind power installation as claimed in claim 1, further comprising: measuring at least a phase angle or an amplitude of a current to be injected into the electrical power supply grid, wherein setting the DC-link voltage depends on the measured phase angle or the measured amplitude of the current to be injected into the electrical power supply grid.

4. The method for controlling a wind power installation as claimed in claim 1, wherein the first time constant is in a range of between 0 and 1 second.

5. The method for controlling a wind power installation as claimed in claim 4, wherein the first time constant is less than 0.2 seconds.

6. The method for controlling a wind power installation as claimed in claim 1, wherein the second time constant is in a range of between 0 and 5 seconds.

7. The method for controlling a wind power installation as claimed in claim 6, wherein the second time constant is in a range of between 0.5 and 4 seconds.

8. A wind power installation connected to an electrical power supply grid, wherein the electrical power supply grid has a higher line impedance than a line impedance of a line reactor of the wind power installation, wherein the electrical power supply grid has a short-circuit power ratio of less than 6, the wind power installation being configured to perform the method for controlling the wind power installation as claimed in claim 1.

9. A wind power installation, comprising: a converter having a DC link with a DC-link voltage, wherein the converter is coupled to an electrical power supply grid and configured to inject electrical power into the electrical power supply grid depending on a measured grid voltage, and a controller coupled to the converter and configured to: receive the measured grid voltage of the electrical power supply grid over a period of time, cause the converter to set the DC-link voltage depending on the measured grid voltage and according to a first time constant over the period of time and a second time constant over the period of time, wherein the first time constant is different than the second time constant, and establish whether there is a positive grid voltage change or negative grid voltage change within the electrical power supply grid.

10. The wind power installation as claimed in claim 9, further comprising a sensor configured to measure a phase angle of a current to be injected in the electrical power supply grid or amplitude of the current to be injected in the electrical power supply grid, or both.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The present disclosure will now be explained in more detail below by way of example and using exemplary embodiments with reference to the attached figures, wherein the same reference symbols are used for identical or similar component parts. In the drawings:

(2) FIG. 1 shows a schematic illustration, by way of example, of a perspective view of a wind power installation in one embodiment,

(3) FIG. 2 shows a schematic illustration, by way of example, of a design of an electrical phase of a wind power installation according to the invention, and

(4) FIG. 3 shows a schematic illustration, by way of example, of the characteristic of a DC-link voltage of an inverter, which is operated using a method according to the invention, depending on a grid voltage.

DETAILED DESCRIPTION

(5) FIG. 1 shows a perspective view of a wind power installation 100.

(6) The wind power installation 100 has, in addition, a tower 102 and a nacelle 104. An aerodynamic rotor 106 having three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. The rotor 106 is set in rotary motion during operation by the wind and thus drives a generator in the nacelle. As a result, the generator generates a current to be injected, which is injected into an electrical power supply grid by means of an inverter.

(7) FIG. 2 shows a schematic illustration, by way of example, of an electrical phase 100′ of a wind power installation 100 according to the disclosure, as shown preferably in FIG. 1.

(8) The aerodynamic rotor of the wind power installation 106 is connected to the generator 120 of the wind power installation. Preferably, the generator 120 is in this case in the form of a six-phase ring generator.

(9) In addition, the generator 120 is connected to an electrical power supply grid 200 via a converter 130 by means of a grid protection device 140 and a transformer 150.

(10) In order to convert the electrical power generated by the generator 120 into a current I.sub.INJ to be injected, the converter 130 has, at the converter input, a rectifier 132. The rectifier 132 is additionally connected to a first DC link 133. The first DC link 133 is in turn connected to a step-up converter 134. The step-up converter 134 is in turn connected to a chopper 135. The chopper 135 is in turn connected to a second DC link 136. The second DC link 136 is in turn connected to an inverter 137. The inverter 137 itself in this case forms the converter output, which is provided with a grid protection device 140.

(11) The grid protection device 140 comprises, for example, an interaction-limiting reactor 142, a filter 144 and a line reactor 146. In a preferred embodiment, the grid protection device 140 is therefore in the form of an LCL filter.

(12) In order to inject the current I.sub.INJ to be injected into the electrical power supply grid 200, in addition a wind power installation transformer 150 is provided, which is preferably star-delta connected.

(13) The electrical power supply grid 200 to which the wind power installation 100 is connected by means of the transformer 150 may be, for example a wind farm grid or an electrical power supply grid or distribution grid.

(14) In order to control the electrical phase 100′, in addition a controller 160 is provided.

(15) The controller 160 is designed to measure the current I.sub.INJ to be injected by means of a current measurement sensor 162. In addition, the controller also has voltage measurement sensor 164, which are designed to measure a grid voltage of the electrical power supply grid 200.

(16) In a particularly preferred embodiment, the controller 160 is additionally designed to measure the phase angle and the amplitude of the current I.sub.INJ to be injected as well.

(17) In a further embodiment, the controller is also designed to determine the impedance of the grid protection device 140. This can take place, for example, via a measurement or by a parameterization of the controller 160.

(18) From the thus measured values, i.e., for example, the grid voltage and the phase angle, the controller then determines the time constants T1 and T2, which are passed on to the converter 130 by means of a signal line 166. Alternatively, the time constants can also be calculated or simulated and then parameterized in the wind power installation.

(19) However, it is also conceivable for the converter 130 to have an active rectifier, which combines the principles of operation of the component parts 132, 133, 134 such that the time constants T1 and T2 are then used to activate this active rectifier.

(20) In addition, the converter 130 has a field current unit 138, which is designed to provide a field current for the generator 120 from the DC link 133.

(21) The principles of operation resulting from such a design will now be described below with reference to FIG. 3.

(22) FIG. 3 shows a schematic illustration, by way of example, of the characteristic of a DC-link voltage of an inverter of a wind power installation depending on a measured grid voltage using the method according to the disclosure.

(23) In an upper graphical representation 301, the grid voltage of the electrical power supply grid V.sub.grid is plotted over time.

(24) In a lower graphical representation 302, the DC-link voltage V.sub.D2 is plotted over time. Preferably, the DC-link voltage V.sub.D2 is the DC-link voltage of a second DC link 136, as shown in particular in FIG. 1.

(25) The time characteristic in the graphical representations 301 and 302 is substantially time-synchronous. This is indicated by the dashed lines t1, t2, t3, t4, t5.

(26) The graph 310 in the upper graphical representation 301 in this case shows the characteristic of the grid voltage V.sub.grid of the electrical power supply grid.

(27) At time t1, this grid voltage V.sub.grid collapses, whereupon the DC-link voltage V.sub.D2, which is indicated by the graph 320 in the lower graphical representation 302, is reduced slowly by means of the time constant T1.

(28) At time t2, the grid voltage V.sub.grid recovers again or rises to its original level, whereupon the DC-link voltage V.sub.D2 is raised directly again by means of the time constant T2.

(29) At time t3, the grid voltage V.sub.grid of the electrical power supply grid rises suddenly, whereupon likewise the DC-link voltage V.sub.D2 is raised directly again by means of the time constant T2.

(30) At time t4, the grid voltage V.sub.grid drops again to its original level, whereupon the DC-link voltage V.sub.D2 is lowered again slowly by means of the time constant T1.

(31) The direct rise in the DC-link voltage V.sub.D2 at times t2 and t3 is in this case caused by the time constant T1, which is substantially 0 seconds.

(32) The slow reduction in the DC-link voltage from times t1 and t4 is in this case caused by the second time constant T2, which is substantially set to a value in the range of between 0.5 and 4 seconds.

(33) By virtue of such a parameterization of the time constants T1 and T2, it is possible to smooth the DC-link voltage.

(34) It has therefore been identified in accordance with the disclosure that such a design for the time constants T1 and T2 results in a better quality of the current I.sub.INJ to be injected.

(35) This enables in particular operation of wind power installations on grids with sources of interference (for example large steel factories), on grids with a low SCR and/or enables a greater safety distance from stability limits of the electrical power supply grid and/or the wind power installation.

(36) The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.