WIND FARM BLACK START

Abstract

A method of performing a black start in a wind farm is provided, the wind farm including a primary black start enabled wind turbine, at least one secondary black start enabled wind turbine, and a wind farm grid interconnecting at least a part of the wind turbines in the wind farm, the method including (a) starting the primary black start enabled wind turbine in black start mode in order to supply voltage to the wind farm grid, (b) monitoring, at the at least one secondary black start enabled wind turbine, an electric parameter value in the wind farm grid, and (c) starting the at least one secondary black start enabled wind turbine in black start mode in order to supply voltage to the wind farm grid when the monitored electric parameter value meets a predetermined condition. A corresponding wind farm is also provided.

Claims

1. A method of performing a black start in a wind farm, the wind farm comprising a primary black start enabled wind turbine, at least one secondary black start enabled wind turbine, and a wind farm grid interconnecting at least a part of the wind turbines in the wind farm, the method comprising: starting the primary black start enabled wind turbine in black start mode in order to supply voltage to the wind farm grid; monitoring, at the at least one secondary black start enabled wind turbine, an electric parameter value in the wind farm grid, and starting the at least one secondary black start enabled wind turbine in black start mode in order to supply voltage to the wind farm grid when the electric parameter value meets a predetermined condition.

2. The method according to claim 1, wherein the electric parameter value is a voltage level in the wind farm grid, and the predetermined condition is met when the voltage level is above a predetermined voltage threshold value.

3. The method according to claim 1, wherein the electric parameter value is a voltage frequency in the wind farm grid, and the predetermined condition is met when the voltage frequency is above or below a predetermined frequency threshold value.

4. The method according to claim 1, wherein the electric parameter value is a code modulated onto the grid voltage, and the predetermined condition is met when the code corresponds to a predetermined code.

5. The method according to claim 4, wherein the code is modulated onto the grid voltage when the primary black start enabled wind turbine has been operating in black start mode for a predetermined period of time and/or when the voltage level in the wind farm grid reaches a predetermined voltage level and/or when the wind farm grid frequency is above or below a predetermined frequency value and/or when the primary black start enabled wind turbine has used a pre-determined amount of capacity.

6. The method according to claim 1, wherein the at least one secondary black start enabled wind turbine comprises a plurality of secondary black start enabled wind turbines, and the predetermined condition is individual for each of the secondary black start enabled wind turbines.

7. The method according to claim 6, wherein the predetermined condition is different for each of the secondary black start enabled wind turbines.

8. The method according to claim 6, wherein the predetermined condition is identical for each of the secondary black start enabled wind turbines.

9. The method according to claim 6, wherein the predetermined condition is a first predetermined condition for a first group of the secondary black start enabled wind turbines, and the predetermined condition is a second predetermined condition for a second group of the secondary black start enabled wind turbines.

10. The method according to claim 1, wherein starting the primary black start enabled wind turbine occurs in response to receiving a black start initiation signal at the primary black start enabled wind turbine.

11. The method according to claim 1, further comprising operating the at least one secondary black start enabled wind turbine in a black start stand-by mode prior to starting the preselected black start enabled wind turbine in black start mode.

12. The method according to claim 11, wherein operating the at least one secondary black start enabled wind turbine in the black start stand-by mode is initiated when receiving the black start initiation signal at the at least one secondary black start enabled wind turbine.

13. A wind farm comprising: a primary black start enabled wind turbine; at least one secondary black start enabled wind turbine; and a wind farm grid interconnecting at least a part of the wind turbines in the wind farm; wherein the primary black start enabled wind turbine is configured to start operating in a black start mode in order to supply voltage to the wind farm grid; wherein the at least one secondary black start enabled wind turbine is configured to monitor an electric parameter value in the wind farm grid and to start operating in black start mode in order to supply voltage to the wind farm grid when the electric parameter value meets a predetermined condition.

14. The wind farm according to claim 13, further comprising at least one ordinary wind turbine that is not black start enabled.

15. The wind farm according to claim 13, further comprising a controller configured to transmit a black start initiation signal to the primary black start enabled wind turbine and/or to the at least one secondary black start enabled wind turbine.

Description

BRIEF DESCRIPTION

[0046] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0047] FIG. 1 shows a wind farm comprising a mix of ordinary and black start enabled wind turbines;

[0048] FIG. 2 shows a flowchart of a method of performing a black start in a wind farm in accordance with an embodiment; and

[0049] FIG. 3 shows a timing chart of control signals for operating black start enabled wind turbines in a wind farm during a black start in accordance with an embodiment.

DETAILED DESCRIPTION

[0050] The illustration in the drawing is schematic. It is noted that in different figures, similar or identical elements are provided with the same reference numerals or with reference numerals which differ only within the first digit.

[0051] FIG. 1 shows a wind farm 100 comprising a mix of ordinary wind turbines 114 and black start enabled wind turbines 110. The wind turbines 110, 114 are arranged in rows and interconnected by cables 122 connected to a common feeder 120 which is connected to utility grid 160 via main breaker switch 140 and transformer 150. The common feeder 120 and cables 122 form a wind farm grid. Each black start enabled wind turbine 110 is connected to its own dedicated power generator/storage unit 112 which is configured to supply auxiliary power to the black start enabled wind turbine 110 when the wind farm grid 120, 122 is deenergized. The wind farm 100 further comprises a wind farm controller 130 configured to receive internal input 132 from one sensor device 142 on the wind farm side of the main breaker switch 140 and from another sensor device 144 on the grid side of the main breaker switch 140. Measurements on both sides of the wind farm breaker is an optional feature but enables the wind farm controller 130 to resynchronize and connect the wind farm to the utility grid 160 when this part of the network has been energized. The internal input 132 to controller 130 may include measurement values of voltage frequency and magnitude on both the wind farm side and the utility grid side of main breaker switch 140. Furthermore, the internal input 132 may include a status of the main breaker switch 140. The controller 130 is further configured to receive external input 134, e.g., from a utility grid operator (not shown). The controller 130 is connected to a wind farm communication network 136 which (at least during normal operation) allows the controller 130 to communicate with each individual wind turbine 110, 114 in the wind farm 100.

[0052] The black start enabled wind turbines 110 are capable of operating in a black start mode to produce and provide electrical power in order to energize the wind farm grid 120, 122 in case of a power outage where no power is available from the utility grid 160.

[0053] FIG. 2 shows a flowchart of a method 200 of performing a black start in a wind farm 100 (see FIG. 1) in accordance with an embodiment. Here, one of the black start enabled wind turbines 110 is preselected as a primary black start enabled wind turbine T1 and the remaining black start enabled wind turbines 110 are preselected as secondary black start enabled wind turbines T2, T3.

[0054] In embodiments, the method 200 begins at 210 by starting the primary black start enabled wind turbine T1 in black start mode in order to supply voltage to the wind farm grid and thereby cause the voltage in the wind farm grid to increase. This may occur in response to receiving a black start initiation signal at the primary black start enabled wind turbine T1, either through an operational part of the communication network 136 or through a dedicated communication channel (not shown).

[0055] At 220, the at least one secondary black start enabled wind turbine (FIG. 1 shows two secondary black start enabled wind turbines T2, T3) monitors an electric parameter value in the wind farm grid, such as a voltage magnitude, a frequency, or a code modulated onto the voltage. At this time, each of the secondary black start enabled wind turbines T2, T3 may be operated in a black start stand-by mode, where the rotors are spinning and the converters are energized, etc.

[0056] The secondary black start enabled wind turbines T2, T3 may start operating in the black start stand-by mode in response to receiving the above-mentioned black start initiation signal.

[0057] At 230, the at least one secondary black start enabled wind turbine T2, T3 is started in black start mode in order to supply voltage to the wind farm grid when the monitored electric parameter value meets a predetermined condition which may be individual for each secondary black start enabled wind turbine T2, T3. The predetermined condition may for example be met when the voltage level in the wind farm grid 120, 122 is above a predetermined voltage threshold value, or when the voltage frequency in the wind farm grid is above or below a predetermined frequency threshold value, or when a code modulated onto the grid voltage is determined to correspond to a predetermined code. The predetermined condition may be different or identical for each of the secondary black start enabled wind turbines T2, T3. Alternatively, the predetermined condition may be a first predetermined condition for a first group of secondary black start enabled wind turbines 110 while the predetermined condition is a second predetermined condition for a second group of secondary black start enabled wind turbines 110.

[0058] In short, the above procedure results in that the primary black start enabled wind turbine T1 starts supplying power to the wind farm grid 120, 122, and that the secondary black start enabled wind turbines T2, T3 joins it once their respective conditions are fulfilled, i.e., sequential one after the other, all together at essentially the same time, or in groups. The trigger for the secondary black start enabled wind turbines T2, T3 to start operating in black start mode is individual conditions relating to an electric parameter value in the wind farm grid. Hence, no active interaction from the farm controller 130 or from any other control unit is needed in order to make the secondary black start enabled wind turbines T2, T3 join the primary black start enabled wind turbine T1 to perform a black start of the wind farm 100. Once the primary black start enabled wind turbine T1 has been started in black start mode, the other (secondary) black start enabled wind turbines T2, T3 will join it as soon as their monitoring reveals that the corresponding conditions are met.

[0059] FIG. 3 shows a timing chart of control signals for operating black start enabled wind turbines in a wind farm during a black start in accordance with an embodiment. More specifically, FIG. 3 shows a plot 310 showing the wind farm grid voltage V as a function of time, a control signal 321 for a primary black start enabled wind turbine T1, a control signal 322 for a first secondary black start enabled wind turbine T2, and a control signal 323 for a third secondary black start enabled wind turbine T3. In this embodiment, the wind farm grid voltage V is monitored and used to determine when to start operating the secondary black start enabled wind turbines T2, T3 in black start mode. The primary black start enabled wind turbine T1 begins operating in black start mode at time t=t.sub.1 when the corresponding control signal 321 shifts to ON. This causes the wind farm grid voltage V to increase along a first ramp segment 311. When the wind farm grid voltage V reaches a first threshold value V.sub.thres1 at time t=t.sub.2, the first secondary black start enabled wind turbine T2 determines that its predetermined condition is met and consequently switches to black start mode by toggling its corresponding control signal 322 to ON. The wind farm voltage continues to increase along a second ramp segment 312. When the wind farm grid voltage V reaches a second threshold value V.sub.thres2 at time t=t.sub.3, the second secondary black start enabled wind turbine T3 determines that its predetermined condition is met and consequently switches to black start mode by toggling its corresponding control signal 323 to ON. The wind farm voltage V then continues to increase along a third ramp segment 313. At time t=t.sub.4, the wind farm grid voltage V reaches a level V.sub.min which is the lowest voltage at which the complete wind farm may be safely operated without the risk of causing damage to the wind ordinary wind turbines. At time t=t.sub.5, the wind farm grid voltage V reaches a target level V.sub.target which is the desired voltage level in the wind farm grid during normal operation. This level is maintained along segment 314 and the wind farm 100 can now be (re)connected to the utility grid 160 and, if necessary, contribute to restoring the utility grid voltage. Alternatively, the wind farm is operated in island mode as means to supply the islanded electrical load, which could be wind turbine and substation auxiliary load, and which could also include dedicated customers as e.g., an electrolyzes plant.

[0060] The energization, that is the complete voltage ramp from 0% to V.sub.min, must be completed fast enough to avoid damaging the electrical components, i.e., it is required that t.sub.4?t.sub.1?T.sub.Limit. It is desirable to keep the time outside this window short, e.g., below 30 to 60 seconds, to avoid the risk of extended operation at voltage levels that the electrical components have not been verified for, or potentially much shorter, e.g., below 5 seconds, if electrical protection equipment cannot safely detect electrical faults during the voltage ramping. This is possible with embodiments of the present invention where the secondary black start enabled wind turbines T2, T3 join the primary black start enabled wind turbine automatically in dependency of one or more conditions relating to a monitored electrical parameter value in the wind turbine grid 120, 122.

[0061] Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0062] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.