Abstract:
A method of providing power from a wind generator includes sending a request to supply power to an operator of a power distribution network; receiving an authorization to supply power from the power distribution network operator; and connecting the wind generator to the power distribution network in response to the authorization to supply power.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The subject matter described here generally relates to wind turbines, and, more particularly, to a method and apparatus for quickly restarting wind turbines. 
         [0003]    2. Related Art 
         [0004]    A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by the machinery, such as to pump water or to grind wheat, then the wind turbine may be referred to as a “windmill.” Similarly, if the mechanical energy is converted to electricity, then the machine may also be referred to as a “wind generator” or “wind power plant.” 
         [0005]    Wind turbines are typically categorized according to the vertical or horizontal axis about which the blades rotate. One so-called horizontal-axis wind generator is schematically illustrated in  FIG. 1  and available from General Electric Company. This particular configuration for a wind turbine  2  includes a tower  4  supporting a nacelle  6  enclosing a drive train  8 . The blades  10  are arranged on a “spinner” or hub  9  to form a “rotor” at one end of the drive train  8  outside of the nacelle  6 . The rotating blades  10  drive a gearbox  12  connected to an electrical generator  14  at the other end of the drive train  8  arranged inside the nacelle  6  along with a control system  16  that typically includes a programmable logic controller and may receive input from an anemometer  18 . 
         [0006]    The blades  10  generate lift and capture momentum from moving air that is them imparted to the rotor  9 . Each blade  10  is typically secured to the hub  9  at its “root” end, and then “spans” radially “outboard” to a free, “tip” end. The front, or “leading edge,” of the blade  10  connects the forward-most points of the blade that first contact the air. The rear, or “trailing edge,” of the blade  10  is where airflow that has been separated by the leading edge rejoins after passing over the suction and pressure surfaces of the blade. A “chord line” connects the leading and trailing edges of the blade  10  in the direction of the typical airflow across the blade and roughly defines the plane of the blade. 
         [0007]    “Angle of attack” is a term that is used in to describe the angle between the chord fine of the blade  10  and the vector representing the relative motion between the blade and the air. “Pitching” refers to rotating the angle of attack of the entire blade  10  into or out of the wind in order to control the rotational speed and/or absorption of power from the wind. For example, pitching the blade “towards feather” rotates of the leading edge of the blade  10  into the wind, while pitching the blades “towards stall” rotates the leading edge of the blade out of the wind. 
         [0008]    For so-called “pitch controlled” wind turbines, the pitch may be adjusted each time the wind changes in order to maintain the rotor blades at the optimum angle and maximize power output for all wind speeds. For example, the control system  16  may check the power output of the turbine  2  several times per second. When the power output becomes too high, the control system  16  then sends a signal to the blade pitch mechanism which causes the blades  10  to be pitched slightly (or entirely) out of the wind. The blades  10  are then turned back into the wind when the wind speed slows down. 
         [0009]    Commonly-assigned U.S. Pat. No. 7,126,236 discloses “Methods and Apparatus for Pitch Control Power Conversion” and is reproduced in  FIG. 2  where the control system  16  (from  FIG. 1 ) includes one or more controllers within a control panel  112  for overall system monitoring and control including pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application and fault monitoring. However, alternative distributed or centralized control architectures are also used in some configurations. 
         [0010]    The control system  16  provides control signals to the variable blade pitch drive or actuator  114  to control the pitch of blades  10  ( FIG. 1 ) that drive hub  110 . The drive train  8  ( FIG. 1 ) of the wind turbine  2  includes a main rotor shaft  116  (also referred to as a “low speed shaft”) connected to hub  110  and a gear box  12  that, in some configurations, utilizes a dual path geometry to drive a high speed shaft enclosed within gear box. A high speed shaft from the opposite end of the gear box is used to drive a first generator  120 . In some configurations, torque is transmitted via the coupling  122 . 
         [0011]    The electricity generated by one or more of these wind turbines  2  in a wind park or “wind farm” is normally fed into an electric power transmission network that is typically operated by a utility company. Different types of wind turbine generators behave differently during transmission grid disturbances, including restarting of the turbines. Transmission system operators will therefore require a wind farm developer to follow a “grid code” that specifies the requirements for interconnection to the transmission grid. The grid code will typically specify a variety of operating parameter tolerances in areas such as power factor, frequency, voltage and current, and the requirements for parameters during various transmission events such as low voltage ride through. 
         [0012]    Various power quality issues arise when a wind generator is connected or reconnected to a power distribution network. For example, the generator  14  may be initially operated as a motor in order to bring the rotor up to the appropriate speed. During that time an in-rush current to the generator  14  may cause a voltage dip on the power distribution network. Even after the generator  14  is motoring at the appropriate speed, voltage, current, real and reactive power, and/or frequency variations may occur in the distribution networks when the turbine  2  is connected (or “cut in”) to the network as a generator and/or operated at less than full speed. 
         [0013]    For this reason, a typical procedure for staring a wind turbine  2  may involve starting with the blades at an initial “feather” position of about 85 degrees with the generator rotating at less than 60 rpm. The blades are then pitched to a “spin up” position of about 65 degrees for at least 60 seconds until the generator reaches about 350 rpm. Around that speed, the blades are pitched to a “spin up” position of about 4 degrees for about another 60 seconds until the generator reaches a speed of about 1000 rpm. At that speed the generator has reached a “cut in” state and is connected to the network and the controller  16  is allowed to control the blade pitch for efficient power production. In about 25 seconds the generator will then reach a “load” state and attain its normal operating speed of 1440 rpm. In order to maintain the grid code requirements, such startup procedures can require the wind turbine  2  to be unproductive for three minutes or more each time the turbine is reconnected to the grid. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0014]    These and other drawbacks associated with such conventional approaches are addressed here in by providing, in various embodiments, a method of providing power from a wind generator, including sending a request to supply power to an operator of a power distribution network: receiving an authorization to supply power from the power distribution network operator; and connecting the wind generator to the power distribution network in response to the authorization to supply power. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Various aspects of this technology will now be described with reference to the following figures (“FIGs.”) which are not necessarily drawn to scale, but use the same reference numerals to designate corresponding parts throughout each of the several views. 
           [0016]      FIG. 1  is a schematic side view of a conventional wind generator. 
           [0017]      FIG. 2  is a cut-away orthographic view of the nacelle and hub of the conventional wind generator shown in  FIG. 1 . 
           [0018]      FIG. 3  is a schematic view of the a wind generator connected to a power distribution network. 
           [0019]      FIG. 4  is a schematic view of a wind generator farm connected to a power distribution network. 
           [0020]      FIG. 5  is a schematic flow diagram. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    In  FIGS. 3 and 4 , each of the illustrated wind turbines  2  includes blades  10  for rotating a gearbox  12  and a generator  14 . A control system  16  sends and receives control signals from a brake  300  and a central control unit  302  for the generator  14 . For example, the central control unit  302  may help to regulate the voltage on the bus (nor shown), manages and control excitation to the generator, and work in conjunction with the control system  16  for adjusting pitch of the blades  10 . 
         [0022]    Power is provided from one or more wind turbines or wind generators  2  by sending a sending a request  306  to supply power to an operator  304  of a power distribution network. The request may be sent automatically by the wind turbine control system  16 , by a wind farm controller  312  for multiple wind turbines (shown in  FIG. 5 ), and/or via an intermediary such as a wind turbine operator and/or electrical power broker, system administrator, or regulator. The request may also be initiated from an operator  304  of a power distribution network that needs power from the wind turbine  2 . 
         [0023]    For example, the request  306  will indicate and/or warn the operator  304  that grid fluctuations are likely to occur when the wind turbine  2  is connected to the power distribution network and/or otherwise brought on-line. In this regard, the request  306  may include at least one capacity parameter for the wind generator, such as, but not limited to, a real and/or reactive power production capacity like kilowatts or kilovolt amperes. Alternatively, or in addition, the request  306  may include one or more parameters indicating the current operational status of the wind turbine  2 , such as arriving at a cut in or load state. For example, status parameters may indicate that the generator  14  is ready to be connected to the power distribution network such as, but not limited to, that it is operating at a minimum or other predetermined speed, power, frequency, phase angle, voltage, current, and/or other condition. 
         [0024]    Multiple and/or consecutive requests  306  may also be sent to, and received by, the operator  304  of the power distribution network with repeated information, updated information, historical information, and/or predicted information regarding the capacity, status, and/or other information concerning the wind turbine  2 . For example, as illustrated in  FIG. 5  a first request  306  to supply power may be sent to an operator  304  ( FIGS. 3 and 4 ) of a power distribution network with at least one capacity parameter for the wind generator. A second request  308  to supply power may also be sent to the operator  304  of the power distribution network with at least one status parameter for the wind generator, such as arriving at a cut in or load state. For example, the second request  308  may be sent when the generator  14  has achieved a predetermined status such as a predetermined speed. power, frequency, phase angle, voltage, current, and/or other condition. In this way, the operator  304  may be informed that the wind turbine  2  in a condition that will allow it connect to the power distribution network very soon. 
         [0025]    When any of the requests  306  and  308  are sent by the wind turbine  2 , and/or received by the operator  304 , the operator of the power distribution network may send, and the wind turbine  2  may receive, an authorization  310  to supply power from the power distribution network operator. The authorization  310  may be sent automatically by the power distribution network and/or via an intermediary such as a network operator and/or electrical power broker, system administrator, or regulator. For example, the authorization  310  may include an immediate or future time to connect to the power distribution network. Information concerning how to connect to the power distribution network, such as current grid code requirements, may also be included in the authorization. Multiple and/or consecutive authorizations  310  may also be sent to, and received by, the wind turbine  2  of the power distribution network with repeated information, updated information, historical information, and/or predicted information regarding the capacity, status, grid code and/or other information concerning the power distribution network. In this way, the wind turbine  2  and/or its operator may be informed that the wind turbine can supply power without upsetting the power distribution network. 
         [0026]    Various embodiments of the technology described above can be implemented in hardware, software, firmware, or a combination thereof. For example, any such software or firmware may be stored in a memory and that is executed by a suitable instruction execution system. If implemented in hardware, various technologies may be used, including discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc. Any suitable medium and/or technologies may also be used to communicate the requests  306  and  308 , and authorizations  310 , including wired and/or wireless systems such as telegraphic, telephonic, radio, optical, Internet and other computer networks, and powerline communication systems. 
         [0027]    The flow chart of  FIG. 5  discussed above, shows the general functionality and operation of a possible implementations of the system. In this regard, each block represents a module, segment, or portion of code, which may include one or more executable instructions for implementing the specified logical function(s) with various types of hardware. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in  FIG. 5 . For example, two blocks shown in succession in  FIG. 5  may in fact be executed substantially concurrently, some blocks may be omitted, or the blocks may sometimes be executed in different order. 
         [0028]    The technology described above offers various advantages over conventional approaches. For example, the wind turbine  2  may be brought up to “cut in” speed with stored energy, and/or energy from the power distribution network, before (or after) an authorization  310  is received. The wind turbine  2  may therefore be connected to the power distribution network more quickly and sooner to when it is actually needed. If the power distribution network is not capable of accepting power from the wind turbine  2 , then the turbine does not need to be spun up and/or run up to the appropriate speed for cut in connection to the network before power is needed. Consequently, available wind power supplies are more likely to match power demand. Upsets to the power distribution network may also be minimized or avoided with appropriate warning to and/or authorization from the network operator. could be minimized 
         [0029]    Any process descriptions or blocks in flow charts should be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention. 
         [0030]    It should also be emphasized that the embodiments described above, and particularly any “preferred” embodiments, are merely examples of various implementations that have been set forth here to provide a clear understanding of various aspects of this technology. One of ordinary skill will be able to alter many of these embodiments without substantially departing from scope of protection defined solely by the proper construction of the following claims.