WO2010090593A1

WO2010090593A1 - Device and method for controlling a wind turbine

Info

Publication number: WO2010090593A1
Application number: PCT/SE2010/050145
Authority: WO
Inventors: Mikael Willgert; Börje Karlsson; Johan Bergkvist
Original assignee: Morphic Technologies Aktiebolag (Publ.)
Priority date: 2009-02-09
Filing date: 2010-02-08
Publication date: 2010-08-12
Also published as: CN102124217A; SE0950065A1; CN102124217B; SE536174C2

Abstract

The present invention relates to a plant (1) comprising a support structure (2), which supports at least one wind turbine (5) comprising a rotor (52), journalled on the support structure and having at least two rotor blades (51), and wherein said wind turbine (5) is adapted to be capable of supplying electrical power, wherein the plant (1) comprises measuring means in the form of at least one data source (721, 722, 723, 724) for determining a value for the wind load, to which the support structure (2) is subjected when the wind turbine (5) is in operation, from at least one of the following factors: wind force, wind direction, support structure deflection, support structure movement, and a control system (7) comprising means for changing the load to which the support structure is subjected, and means for determining whether the load to which the support structure is subjected should be changed or maintained on the basis of the load determined by the measuring means, wherein the control system (7) is adapted to receive weather forecast data concerning future weather conditions, and the means for determining whether the load to which the support structure is subjected should be changed or maintained are adapted to use said weather forecast data for determining an allowable load, and the means for changing the load to which the support structure is subjected are adapted to adjust the load so that it does not exceed the allowable load. The invention also relates to a method for optimizing the stability of the support structure.

Description

DEVICE AND METHOD FOR CONTROLLING A WIND TURBINE

TECHNICAL FIELD

The present invention relates to a plant comprising a support structure, which supports at least one wind turbine comprising a rotor, journalled on the support structure and having at least two rotor blades, and wherein said wind turbine is adapted to be capable of supplying electrical power, wherein the plant comprises measuring means in the form of at least one data source for determining a value for the wind load, to which the support structure is subjected when the wind turbine is in operation, from at least one of the following factors: wind force, wind direction, support structure deflection, support structure movement, and a control system comprising means for changing the load to which the support structure is subjected, and means for determining whether the load to which the support structure is subjected should be changed or maintained on the basis of the load determined by the measuring means. The invention also relates to a method for optimizing the stability of a support structure.

STATE OF THE ART

Tall constructions, such as high-rise buildings, masts or towers, are subjected to considerable weather and wind loads. When it is windy, a swaying movement may occur which, if it becomes large enough or the movement starts abruptly, can impose a serious threat to the stability and result in the construction being damaged, tipping over, or even breaking off. If the construction contains sensitive equipment, which is the case for example in a communication mast or a high antenna, the consequences of the wind influence can become particularly serious because of the equipment being damaged or ruined completely. In order to counteract this problem, the construction can be provided with an extensive bracing assembly, in order to provide extra support and anchor the entire construction more firmly to the ground. However, this is complicated and occupies a lot of land, which thus cannot be used for other, more profitable purposes.

Furthermore, masts or towers intended for wireless communication need to be placed in particular locations in order to provide the desired communication and to provide an even coverage over a larger area, as is required, for example, to provide a well-extended network for mobile phones. For natural reasons, the conditions differ greatly, and service and maintenance of the plant can become both complicated and costly, above all when placed in remote and/or deserted areas. Diesel generators or the like are often used to provide the power required for operating the plant, but since diesel then has to be supplied for operating the generator this means that maintenance staff need to make frequent visits to the plant in order to replenish the fuel tank.

One way of trying to reduce the need of constant supervision described in the foregoing is to equip the plant with a renewable energy source such as, for example, a wind turbine. Such techniques are shown, for example, in US 7 138 961 (Sievert) or US2004/0232703 (Michael), where the wind turbine is integrated with the mast itself, so that a combination plant is achieved. This has the great advantage that the plant can be made self-sufficient in energy, or at least that the need of other energy sources such as diesel can be substantially reduced, but a considerable drawback is that the presence of the wind turbine implies that the forces to which the plant is subjected from wind influence are considerably increased, so that an even more advanced bracing assembly than usual is required. This increases the area of land which has to be set aside for the plant even further, and together with the anchoring devices and braces required for ensuring that the mast remains stable, the solution becomes both costly and material requiring.

There is therefore a need to find a solution to the above-described problems.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of the present invention to eliminate or at least minimize the above- mentioned problems, which is achieved by means of plant according to the preamble of claim 1 , wherein the control system is adapted to receive weather forecast data concerning future weather conditions, the means for determining whether the load to which the support structure is subjected should be changed or maintained are adapted to use said weather forecast data for determining an allowable load, and the means for changing the load to which the support structure is subjected are adapted to adjust the load so that it does not exceed the allowable load. Thereby, the control acting on the wind turbine can be changed depending on the expected amount of wind or other weather influence, so that the operation of the power plant is influenced in different ways on different occasions. Thanks to the fact that it can be predicted when the load on the plant is expected to become high, situations where the wind turbine can be damaged by excessive winds can be avoided, and inversely, it is also possible to know beforehand when a period with too weak winds will occur and it is not profitable at all to operate the plant. According to another aspect of the invention, the control system further comprises means for controlling the speed of the wind turbine. Thereby, the resulting force from the wind turbine on the mast can be changed and adapted quickly, in that the rotational speed of the turbine can be adjusted.

According to another aspect of the invention, the control system further comprises feathering means for controlling the angle of incidence of the rotor blades relative to the wind. Thereby, the air resistance generated by the plant can be changed quickly in order to capture as much as possible of the power in the prevailing wind, or in order to reduce the load on the wind turbine so that damages to the plant can be prevented when the wind is excessively strong.

According to another aspect of the invention, the control system further comprises yaw means for turning at least the rotor blades of the wind turbine relative to the support structure. Thereby, the wind turbine can be adapted to capture the wind when it changes direction, so that a higher output power can be obtained, or to reduce the wind resistance, and thereby the force on the support structure, in order to avoid overload, depending on the needs of the plant.

According to another aspect of the invention, said measuring means comprise at least one position sensor adapted to communicate with the control system. Thereby, it becomes possible to follow the displacement of a specific point on the support structure and to detect swaying or other movements.

According to another aspect of the invention, said measuring means comprise at least one acceleration sensor adapted to communicate with the control system. Thereby, the force of a movement can be detected quickly and changes in movements can be followed and analyzed.

BRIEF DESCRIPTION OF FIGURES

In the following, the invention will be described in greater detail with reference to the attached figures of the drawings, in which:

Fig. 1 shows an overview of a preferred embodiment of a plant according to the invention;

Fig. 2 shows an overview of the upper part of the plant; and

Fig. 3 shows a schematic view of a control system for the plant. DETAILED DESCRIPTION OF FIGURES

Fig. 1 shows an overview of a preferred embodiment of a plant 1 according to the invention, comprising a support structure 2, which can be a tower or a mast for wireless communication, provided with communication units in the form of components 4 and antennas 6 for receiving and transmitting various signals, such as for example for mobile phones, TV broadcasts, or radio. The support structure 2 also comprises a wind turbine 5 which, among other things, serves as a current source for the electronic components 4, 6.

The control of the plant is performed by means of a control unit 7, which can be located on or adjacent to the support structure 2, and which is in connection with the wind turbine 5 and, when required, also with other components, such as the electronic equipment 4, 6. In order to provide additional energy, if required, a separate current source can be provided, such as a diesel generator 82, the operation of which also can be controlled through the control unit 7, so that the required electrical power can be provided when there is a need.

A storage unit 81 , such as a battery or an electrolysis tube connected to a fuel cell, is also arranged adjacent to the support structure 2 for storing surplus energy from the wind turbine 5.

When required, also the support structure 2 can be anchored to the ground by means of a bracing assembly 3.

Fig. 2 shows an overview of the upper part of the plant 1, where some of the devices at the support structure 2 are shown in greater detail. The wind turbine 5 comprises a number of rotor blades 51 , which are connected to a generator 52 for producing electrical power. By means of a conventional arrangement, such as a rotor and stator, kinetic energy from the rotation of the rotor blades 51 is transformed into electrical energy, which via electrical connections can be used in the communication components 4 and/or antennas 6 which are arranged at the support structure 2. The electrical power thus produced can also be stored in a suitable storage unit 81 , as is shown in Fig. 1.

The wind turbine 5 also comprises feathering means 53 for controlling the feathering of the rotor blades 51. This, together with other operational parameters of the wind turbine, can be governed and controlled by the control unit 7 or by a separate control system. A series of sensors, such as a position sensor 91 and/or an acceleration sensor 92 for measuring position and acceleration, respectively, of a given point along the support structure, are arranged at the support structure 2. Other sensors, measuring other characteristics of the support structure, are also conceivable.

Fig. 3 shows a schematic view of the control unit 7 with a process unit 71, which receives input data from a series of measuring means in the form of data sources 721, 722, 723, 724, and models control signals therefrom, which are then forwarded to suitable units 731, 732, 721, 724. Since some of these measuring means 721, 724 also constitute data sources for input data to the process unit 71 , a feed-back system enabling an efficient control of the plant 1 has been created.

The use of the plant 1 will now be described in greater detail with reference to the above-described Figures 1-3.

The electrical current required for the operation of the plant 1 is mainly produced by the wind turbine 5, but to be able to control this optimally in a way contributing the stability of the support structure 2, a quantity of input data 721, 722, 723, 724 is collected to the process unit 71 which, in its turn, controls the characteristics of the wind turbine 5 and the energy distribution in the plant 1.

By means of the position sensor 91 and the acceleration sensor 92, data regarding position and acceleration of given points along the supporting structure 2 can be calculated. Furthermore, by using several such sensors positioned at different heights above the ground, data regarding the wind deflection of the support structure can be collected. This is used as input data 722 and 723 to the process unit 71, together with data regarding the speed of the wind turbine 5 and the degree of feathering of the rotor blades 51, in the form of input data 721 and 724, respectively. Also other types of input data can be collected and used for these analyses such as, for example, the actual wind force or weather forecast data. Collected data can also be used for changing the control of the system, so that correcting measures are implemented more quickly if strong wind is expected or so that the operation of the wind turbine is reduced to a minimum or shut down completely during periods for which it can be predicted that the possible output power will be low.

Wind measurement and/or forecast data is used to determine the amount of power which can be drawn from the power plant 5, and this can constitute input data to the process unit 71 or be used as modifications of calculations performed to interpret input data. The control system 7 comprises means for determining whether the load to which the support structure 2 is subjected lies within the allowable limits with respect to parameters of the support structure 2 and its components, such as, for example the structural strength of the materials used. For example, said means for determining whether the load is allowable can be constituted of the process unit 71 , which can also serve to change the load to which the support structure 2 is subjected by means of changing characteristics of the wind turbine 5 such as, for example, a degree of feathering of the rotor blades 51 or a speed of the wind turbine 5.

Accordingly, by continuously receiving weather forecast data, the control system 7 can calculate an expected future load on the support structure 2 and interpret the consequences for the wind turbine: if, for example, an unallowably high load will arise, the process unit 71 is ready to issue an instruction to change parameters such as feathering of the rotor blades 51, yaw movement of the wind turbine 5, or change of the speed of the rotor. If, on the other hand, the resulting estimate is that the future load is within the limits of what the wind turbine 5 can take, normally no action needs to be taken. If, on the other hand, it can be predicted that the wind, at a future point in time, will be too weak to provide a sufficient output power from the wind turbine 5, the parameters above can be changed to provide a higher load on the wind turbine. Thus, owing to these variation possibilities, the operation can be adjusted continuously to correspond to future conditions as well as possible.

In contrast to using only measurements concerning prevailing conditions, by means of this method, it can be determined whether a suddenly increasing wind force indicates an approaching storm or is just a short-lived squall which will soon blow over. In the first case maybe the best thing is to brake the rotor to a standstill and leave the wind turbine shut down while the storm blows over, rather than risking damages to the plant 1 , whereas in the second case, it is probably more profitable to briefly reduce the air resistance, for example by feathering the rotor blades 51 for a period of time, but to maintain the wind turbine 5 in operation. Naturally, measurements of the prevailing conditions are still important, in order to be able to accommodate sudden changes, complemented with the information from weather forecasts, in order to determine whether the changes should be interpreted as part of a larger trend.

In order to correctly determine the position of a given point along the support structure, the position sensor can comprise a light source, which is used for illuminating a reflector (not shown) being positioned on the ground below the support structure. By means of capturing the reflection from the reflector, it can be determined how much the current position differs from a starting position, and in that way a value for the absolute position of the point can be obtained.

By means of the collected data, the load, or load, acting on the support structure 2 is calculated by the process unit 71, and the result is compared to allowable values, based on data such as structural strength of the support structure, in order to ensure that it can take the load in question. Starting from these calculations, the wind turbine is then controlled by output data from the process unit 71 in order to minimize the load and to have as small an influence as possible on the support structure 2. Thereby, by means of input data 721 and 724, the feathering and the speed, respectively, can be influenced, so that the power output and the load from the wind turbine 5 are kept within appropriate limits. Accordingly, in these respects, a feed-back loop is created, where speed and feathering can be dynamically controlled in order to optimize the operation of the wind turbine 5.

As used herein, load refers to the influence the support structure is subjected to by its environment, that is to say the force with which the wind presses against the support structure, the deflection resulting from such a force, the speed at which a swaying movement occurs, or the like. This load can be measured by means of the described instruments, or in another way, and the thus measured values can be combined or modified by various calculations.

Other output data 731 , 732 is used for controlling the charging of the storage unit 81 and the power output of the diesel generator 82, so that the energy use of the plant 1 can be optimized and adapted to the prevailing need. Other characteristics of the plant can also be controlled by output data from the process unit 71.

Thanks to the invention, it thus becomes possible to store and use energy in an advantageous manner, so that the load from the wind turbine 5 on the support structure never exceeds the capacity of the support structure 2, thereby risking damages to the plant. At the same time, an energy output as large as possible within these limits can be obtained, so that the energy supply of the plant 1 will be as favourable as possible and the need of other energy sources, such as diesel in the diesel generator, thereby can be minimized. Accordingly, by detecting the position and movement of the support structure 2 itself, the load can be controlled so that movements due to dynamic changes of the speed of the wind turbine 5 can be minimized or even counteracted. Thereby, an initiated swaying movement could be reduced, so that the risk of resonance vibration or other uncontrolled oscillation increase can be minimized or completely avoided. The combination of speed changes and feathering of the rotor blades also makes the feedback system particularly sensitive and it can respond quickly and sensitively also to very small changes. The force thus created at the rotor can be used to counteract the external forces influencing the plant 1.

In order to counteract such an oscillation, energy may need to be supplied to the power plant 5 to thereby be able to quickly change the speed and/or feathering of the rotor blades 51. This energy can be drawn from the storage unit 81, and then implies that the already produced output power from the wind turbine can be used as input power in order to increase the rotor speed, quickly turn the rotor blades 51 , or make any other change which is required in order to change the load the support structure is subjected to. Alternatively, the energy may originate from an external power source, such as the diesel generator 82.

Also, by means of yaw means integrated with the wind turbine 5, at least some part of said wind turbine 5 can be turned, so that the angle relative to the wind direction can be selected. In order to increase the output power, a yaw turn can be performed to face more into the wind and get a larger force acting on the rotor blades and, vice versa, the load can be reduced by performing a yaw turn away from the wind. Thus, the yaw means become a complement to the other described methods of changing the load on the support structure 2 from the wind turbine 5.

The values for the load on the support structure regarded as allowable can be decided by a number of factors, such as measured and received values for the present or future influence of the environment, as well as material properties or other factors of the support structure itself. These allowable load values can be changed during operation, so that the values regarded as allowable in certain circumstances can fall outside of the allowable interval when other circumstances prevail. For example, in favourable conditions, a higher output power can be drawn from the wind turbine than what otherwise would be possible. The invention is not limited by what has been described hereinabove, but can be varied within the scope of the following claims. For instance, it is appreciated the many different types of data can be used for controlling the operation of a wind turbine, and that the actual construction of the system can be varied. The support structure can be a tower or a mast such as described above in connection with the preferred embodiment, but can also be a tall building or the like. The locations of the different components relative to each other can of course be changed so that, for example, the measuring instruments can be positioned along the support structure, inside a machine housing next to the wind turbine, or in another suitable location. Many other variation options can be accommodated within the scopes of the claims.

Claims

1. A plant (1) comprising a support structure (2), which supports at least one wind turbine (5) comprising a rotor (52), journalled on the support structure and having at least two rotor blades (51), and wherein said wind turbine (5) is adapted to be capable of supplying electrical power, wherein the plant (1) comprises measuring means in the form of at least one data source (721, 722, 723, 724) for determining a value for the wind load, to which the support structure (2) is subjected when the wind turbine (5) is in operation, from at least one of the following factors: wind force, wind direction, support structure deflection, support structure movement, and a control system (7) comprising means for changing the load to which the support structure is subjected, and means for determining whether the load to which the support structure is subjected should be changed or maintained on the basis of the load determined by the measuring means, characterized in

- that the control system (7) is adapted to receive weather forecast data concerning future weather conditions, that the means for determining whether the load to which the support structure is subjected should be changed or maintained are adapted to use said weather forecast data for determining an allowable load, and

- that the means for changing the load to which the support structure is subjected are adapted to adjust the load so that it does not exceed the allowable load.

2. The plant according to any one of the preceding claims, wherein the control system (7) further comprises means for controlling the speed of the wind turbine (5).

3. The plant according to any one of the preceding claims, wherein the control system (7) further comprises feathering means for controlling the angle of incidence of the rotor blades (51) relative to the wind.

4. The plant according to any one of the preceding claims, wherein the control system (7) further comprises yaw means for turning at least the rotor blades (51) of the wind turbine (5) relative to the support structure (2).

5. A method for optimizing the stability of a support structure (2), wherein said support structure (2) supports a wind turbine (5) and, in operation, is subjected to a wind load, comprising the steps of continuously a) obtaining, by measuring, a value for an instantaneous load on the support structure (2) from at least one of the following factors: wind force, wind direction, support structure deflection, support structure movement, and characterized in that further comprising the steps of b) receiving weather forecast data concerning future weather conditions, c) using said weather forecast data for determining an allowable load on the support structure, d) adapting the operation of the wind turbine (5) as a function of the load so that the allowable load is not exceeded by means of at least one of the following measures: - adjusting an angle of incidence of a rotor blade (51 ) of the wind turbine relative to the wind, changing a speed of a generator of the wind turbine (5).

6. The method according to any one of the claims 12-15, wherein data regarding the movement of at least one point associated with the support structure (2) is used for measuring the load on the support structure (2).

7. The method according to any one of the claims 12-16, wherein data regarding the change in movement of at least one point associated with the support structure (2) is used for measuring the load on the support structure (2).

8. The method according to any one of the claims 12-17, wherein the operation of the wind turbine (5) is at least partially feed-back controlled in that at least one data source (721, 724), used for providing input data to the control unit (7), is also capable of receiving control signals from said control unit (7).