Wind turbine controller and method for controlling a power production of a wind turbine

Abstract

A wind turbine controller for controlling power production of a wind turbine is provided. The wind turbine is arranged within a wind farm coupled to a public power network via a point of common coupling. The wind turbine controller has a receiving unit for receiving a measured value of a property of the wind farm taken at the point of common coupling and for receiving a reference value for the property, and a control unit for controlling the power production of the wind turbine by regulating a local property of the wind turbine based on the received measured value and the received reference value such that the measured value of the wind farm taken at the point of common coupling corresponds to the reference value. Further, a wind turbine having such a controller, a wind farm and a method for controlling a power production of a wind turbine are provided.

Claims

1. A wind turbine controller for controlling a power production of a wind turbine, the wind turbine being arranged within a wind farm being coupled to a public power network via a point of common coupling, the wind turbine controller comprising: a receiving unit for receiving a measured value of a property of the wind farm taken at the point of common coupling and for receiving a reference value for the property, a control unit, in communication with the receiving unit, for controlling the power production of the wind turbine in a PCC-control mode by regulating a local property of the wind turbine based on the received measured value of the property and the received reference value of the property according to a current control mode of a plurality of control modes such that the measured value of the property of the wind farm taken at the point of common coupling corresponds to the reference value for the property, and a monitoring unit, in communication with the control unit, for monitoring a value of a local voltage generated by the control unit to control the power production of the wind turbine, wherein the monitoring unit configured to generate a voltage alert signal in response to determining by the monitoring unit the value of the local voltage is below a lower voltage limit value or above an upper voltage limit value of a voltage range, and wherein the control unit configured to receive the voltage alert signal from the monitoring unit and, in response to the voltage alert signal, the control unit switches from the current control mode to a local voltage control mode of the plurality of control modes of the control unit, in which the control unit controls the power production of the wind turbine by regulating the local property of the wind turbine based on the voltage range.

2. The wind turbine controller according to claim 1, wherein the property of the wind farm is at least one of a current, a voltage, a reactive power and a power factor.

3. The wind turbine controller according to claim 1, wherein the local property of the wind turbine is at least one of the local voltage and a local reactive power.

4. The wind turbine controller according to claim 1, wherein the control unit is further configured to determine a difference between the measured value and the reference value.

5. The wind turbine controller according to claim 1, wherein the receiving unit is configured to receive a number of wind turbines being active within the wind farm, and wherein the control unit is further configured to control the power production based on the number of wind turbines.

6. The wind turbine controller according to claim 1, wherein the monitoring unit monitors a value of a current set-point of the wind turbine.

7. The wind turbine controller according to claim 6, wherein the monitoring unit is further configured to generate a current alert signal in response to determining by the monitoring unit the value of the current set-point is below a lower current limit value or above an upper current limit value of a current converter range.

8. The wind turbine controller according to claim 7, wherein the control unit is further configured to receive the current alert signal and to switch to a local current control mode of the plurality of control modes of the control unit, in which the control unit controls the power production of the wind turbine by regulating the local property of the wind turbine based on the current converter range.

9. The wind turbine controller according to claim 8, wherein the control unit is further configured to turn off an integrating unit of the control unit when receiving the current alert signal, and to turn on the integrating unit when the value of the current set-point is within the current converter range.

10. A wind turbine being arranged within a wind farm, the wind turbine comprising: a power production unit for producing power, and a wind turbine controller according to claim 1 for controlling the power production unit.

11. A wind farm being coupled to a public power network via a point of common coupling, the wind farm comprising: a plurality of wind turbines according to claim 10, and a wind farm administration unit for measuring a value of a property of the wind farm taken at the point of common coupling and for sending the value of the property of the wind farm and a reference value for the property to the plurality of wind turbines.

12. The wind turbine controller according to claim 1, wherein the control unit comprises a voltage controller producing a first local signal, an active power controller producing a second local signal, and a converter current controller producing a third local signal, based on an error signal from the point of common coupling wherein the monitoring unit is configured to monitor the first local signal, the second local signal and the third local signal so that the monitoring unit generates an alert signal to switch the control unit to a corresponding different control mode of the plurality of control modes of the control unit in response to the monitoring unit determining when one of the first local signal, the second local signal and the third local signal exceeds a corresponding limit.

13. A method for controlling a power production of a wind turbine, the wind turbine being arranged within a wind farm being coupled to a public power network via a point of common coupling, the method comprising: receiving, by a wind turbine controller of the wind turbine, a measured value of a property of the wind farm taken at the point of common coupling (PCC), receiving, by the wind turbine controller, a reference value for the property, controlling, by a control unit of the wind turbine controller in a PCC-control mode, the power production of the wind turbine by regulating a local property of the wind turbine based on the received measured value of the property and the received reference value of the property according to a current control mode of a plurality of control modes such that the measured value of the property of the wind farm taken at the point of common coupling corresponds to the reference value for the property, monitoring, by a monitoring unit of the wind turbine controller, a value of a local voltage generated by the control unit to control the power production of the wind turbine wherein the monitoring unit is in communication with the control unit, generating, by the monitoring unit, a voltage alert signal in response to determining by the monitoring unit the value of the local voltage is below a lower voltage limit value or above an upper voltage limit value of a voltage range, and switching, in response to the generated voltage alert signal, the control unit of the wind turbine controller from the current control mode to a local voltage control mode of the plurality of control modes of the control unit, in which the power production of the wind turbine is controlled by regulating the local property of the wind turbine based on the voltage range.

14. A non-transitory computer program product comprising a program code for executing the method according to claim 13, when run on at least one computer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiments, features and advantages of the present invention will become apparent from the subsequent description and dependent claims, taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 shows a schematic block diagram of an embodiment of a wind turbine controller;

(3) FIG. 2 shows a schematic block diagram of an embodiment of a wind farm with a plurality of wind turbines;

(4) FIG. 3 shows a schematic block diagram of an embodiment of the control unit of the wind turbine controller of FIG. 1;

(5) FIG. 4 shows an embodiment of a sequence of method steps for switching between different operation modes of the wind turbine controller of FIG. 1; and

(6) FIG. 5 shows an embodiment of a sequence of method steps for controlling a power production of a wind turbine.

DETAILED DESCRIPTION OF INVENTION

(7) In the Figures, like reference numerals designate like or functionally equivalent elements, unless otherwise indicated.

(8) FIG. 1 shows a wind turbine controller 10 for controlling a power production of a wind turbine 1. The wind turbine 1 is arranged within a wind farm 100 (shown in FIG. 2) being coupled to a public power network 6 via a point of common coupling 2.

(9) The wind turbine controller 10 comprises a receiving unit 11, a monitoring unit 12 and a control unit 13. The receiving unit 11 receives a measured value of a property of the wind farm 100 taken at the point of common coupling 2 and receives a reference value for the property. The measured value and the reference value can be received as one signal 3.

(10) The control unit 13 then controls the power production of the wind turbine 1 by regulating a local property of the wind turbine 1 based on the received measured value of the property and the received reference value of the property such that the measured value of the property of the wind farm 100 taken at the point of common coupling 2 corresponds to the reference value for the property. For this purpose, control unit 13 controls a power production unit 20 of the wind turbine 1. The power production unit 20, which can be a generator, produces power 4 which is then supplied to the public power network or grid 6.

(11) The monitoring unit 12 monitors a value of a current and/or a value of a voltage at an output terminal of the wind turbine 1. If the current value or the voltage values are below a lower limit value or above an upper limit value of a defined range, the monitoring unit 12 generates an alert signal and the control 13 adjusts the power production accordingly. This behavior is explained in greater detail with reference to FIGS. 3 and 4.

(12) An overall structure of a wind farm 100 comprising a plurality of wind turbines 1 as shown in FIG. 1 is illustrated in FIG. 2.

(13) The wind farm 100 comprises a plurality wind turbines 1 being coupled via a wind farm circuit 7 to the PCC 2. The PCC 2 connects the wind farm 100 with the grid 6. The power 4 from the wind turbines 1 is sent via the wind farm circuit 7 and the PCC 2 to the grid 6.

(14) A wind farm administration unit 5 reads the current and voltage measurements at the PCC 2 and sends them to all turbines 1 together with the control mode information. Further, the wind farm administration unit 5 sends the PCC reference values to all turbines. Moreover, the wind farm administration unit 5 sends the number of active turbines 1 within the wind farm 100 to all turbines 1.

(15) In the wind farm 100 as shown in FIG. 2, no central farm controller is needed. Hence, the common hierarchical farm control structure is substituted with a single-level structure.

(16) With the wind turbine controller 10 and the wind farm 100, the following advantages can be achieved. A possible saturation of the terminal controller may be avoided since the integral action of the voltage controller is disabled as soon the converter limits are encountered (this is shown in detail with reference to FIGS. 3 and 4). The wind farm administration unit 5, also called FAU, may provide information, among others, about the number of active turbines 1 which can be used to scale the turbine controllers' gains. The overall farm control system is simplified. The farm PCC control system is faster because a farm controller is not present, i.e. the reaction to any disturbances are now delayed only due to the latency of the communication between the FAU 5 and the turbines 1 and not due to any other processing and decision making like it is the case with the common farm controller. The omission of the central farm controller may also shorten the response time of the frequency control since the turbines 1 may directly change their power generation in order to compensate the frequency deviation. The frequency-power droop function can be scaled by the number of active turbines 1 which is provided by the FAU 5. A Fault Ride Through (FRT) would be more effective in this wind farm 100 since it may consider the PCC information. The FRT control is commonly done at each wind turbine 1 without any coordination and without any information about the PCC measurements. But with the distributed control structure of the wind farm 100, a FRT response can be achieved in relation to the PCC 2 as it is also requested in the grid codes. The control of large farms 100 may be significantly simplified since no centralized controllers are needed. In common wind farms, common central farm controllers can handle only a limited number of turbines which means that several of these controllers have to be installed and coordinated with a so called master farm controller. In the herein described wind farm, no central controllers are needed.

(17) Additional features of this distributed control scheme can be achieved in the case where the turbines 1 are time synchronized with each other. Time synchronization accuracy higher than the converter switching frequency may enable noise cancelling and general power quality improvements via distributed converter control.

(18) Further, the described distributed control of the wind farm 100 may avoid a control signal saturation by restricting the (current) reference point within the limits of the applied converters. This is now explained with reference to FIGS. 3 and 4.

(19) FIG. 3 shows the control unit 13 of FIG. 1. The control unit 13 comprises a voltage PI controller 15, an active power controller 14 and a converter PI current controller 17.

(20) The voltage PI controller 15 produces, based on an error signal 3 from the PCC, i.e. the difference between a reference value and a measured value, a reference Iq current value Idq_ref 16 for the converter PI current controller 17. The power controller produces the reference Iq current as Id=P/|Vter|. The obtained terminal current results in the terminal voltage Vter 18. The Idq_ref signal 16 is limited by the converter characteristics. The terminal voltage magnitude |Vter| is also limited.

(21) The monitoring unit 12 monitors these signals. In case, that any limits are exceeded, the monitoring unit generates an alert signal and the control unit 13 switches the operation mode. This is now explained with reference to FIG. 4.

(22) In a first step 101, is it determined whether the current set point Iq at the converter is between its maximum and minimum values.

(23) If no, the control unit 13 switches (step 102) from the normal operation mode into a local current control mode, in which no integral action in the voltage controller 15 is performed. If yes, it is determined in step 103 whether the terminal voltage magnitude |Vter| is between its maximum and minimum value.

(24) If no, the control unit 13 switches (step 104) to the local terminal voltage control mode. If yes, the control unit 13 stays (step 105) in the normal operation mode, i.e. the PCC control mode.

(25) FIG. 5 shows a method for controlling a power production of a wind turbine 1.

(26) In a first step 201, a measured value of a property of the wind farm 100 taken at the point of common coupling 2 is received.

(27) In a second step 202, which can also be simultaneous to the first step 101, a reference value for the property is received.

(28) In a third step 203, the power production of the wind turbine 1 is controlled by regulating a local property of the wind turbine 1 based on the received measured value of the property and the received reference value of the property such that the measured value of the property of the wind farm 100 taken at the point of common coupling 2 corresponds to the reference value for the property.

(29) Although the present invention has been described in accordance with preferred embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments.

(30) The respective units and/or controllers can be realized with hardware, software or in a combination by hard- and software. Hereby at least parts of the functionalities of the respective units and/or controllers can be implemented by machine-readable code that is stored in a memory and can be read and executed by a processor. The processor is connected to the memory and to one or several other units that allow an exchange of data from and/or to the processor.