Abstract:
The present application thus provides a method of operating a synchronous condenser. The method may include the steps of accelerating a gas turbine engine to full speed no load conditions, connecting a generator attached to the gas turbine engine to an electric power grid, turning off a flow of fuel to the gas turbine engine, operating the generator in a synchronous condenser mode, and providing or absorbing reactive power to or from the electric power grid.

Description:
TECHNICAL FIELD 
       [0001]    The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to a synchronous condenser attached to a gas turbine engine to provide electric power grid stability without further mechanical and/or electrical components. 
       BACKGROUND OF THE INVENTION 
       [0002]    Synchronous condensers are utilized in a wide variety of applications such as power generation. Synchronous condensers typically are utilized to adjust conditions on an electric power distribution grid. A synchronous condenser is a specialized motor with an unattached shaft that spins freely. The synchronous condenser may generate or absorb reactive power as needed to support the voltage and/or maintain a power factor on the electric power distribution grid. 
         [0003]    Similarly, synchronous generators driven by turbines or other types of power sources are commonly used by utilities to produce electrical energy. After years of use, a power utility may retire or decommission a synchronous generator from use as a power generation unit. In some cases, it may be desirable to use these retired synchronous generators as synchronous condensers to generate reactive power or absorb reactive power from the electric power grid. A retired synchronous generator generally must be decoupled from the turbine shaft before being used as a synchronous condenser. Instead, a starting motor may be attached to the shaft to bring the synchronous generator up to operational speed. Attaching the starting motor to the shaft, however, may be time consuming. Moreover, the starting motor needs to be designed to withstand any operational events such as electrical faults in the motor or the synchronous condenser, overspeed events, shaft failures, and the like. A sufficient amount of space and power also may be required to position and drive the starting motor or other device used to rotate the shaft. 
         [0004]    There is thus a desire for an improved and/or simplified synchronous condenser. Such a synchronous condenser may generate and/or absorb reactive power so as to provide stability to an electric power grid without the need for a starting motor or types of mechanical and/or electrical devices that may require space and parasitic power to operate. 
       SUMMARY OF THE INVENTION 
       [0005]    The present application and the resultant patent thus provide a method of operating a synchronous condenser. The method may include the steps of accelerating a gas turbine engine to full speed no load conditions, connecting a generator attached to the gas turbine engine to an electric power grid, turning off a flow of fuel to the gas turbine engine, operating the generator in a synchronous condenser mode, and providing or absorbing reactive power to or from the electric power grid. 
         [0006]    The present application and the resultant patent further provide a gas turbine engine. The gas turbine engine may include a combustor, a turbine, a generator, and a shaft connecting the turbine and the generator. The turbine rotates the shaft to drive the generator when the generator is in an active power mode and the generator rotates the shaft when the generator is in a synchronous condenser mode providing reactive power. 
         [0007]    The present application and the resultant patent further provide a synchronous condenser system. The synchronous condenser system may include a combustor, a turbine, a generator, and a shaft. The generator freely spins the shaft when the generator is in a synchronous condenser mode to provide and absorb reactive power to the electric power grid. 
         [0008]    These and other features and improvements of the present application and the resultant patent will become apparent to one skilled in the art upon review of the following detailed description and taken in conjunction with the several drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is schematic diagram of a gas turbine engine with a synchronous condenser system as may be described herein. 
           [0010]      FIG. 2  is a flow chart showing the operation of the synchronous condenser system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a schematic diagram of gas turbine engine  10  as may be used herein. The gas turbine engine  10  may include a compressor  15 . The compressor  15  compresses an incoming flow of air  20 . The compressor  15  delivers the compressed flow of air  20  to a combustor  25 . The combustor  25  mixes the compressed flow of air  20  with a pressurized flow of fuel  30  and ignites the mixture to create a flow of combustion gases  35 . Although only a single combustor  25  is shown, the gas turbine engine  10  may include any number of the combustors  25  arranged in a circumferential array or otherwise. The flow of combustion gases  35  is delivered in turn to a turbine  40 . The flow of combustion gases  35  drives the turbine  40  so as to produce mechanical work. The mechanical work produced in the turbine  40  drives the compressor  15  via a shaft  45  and an external load such as an electrical generator  50  and the like. A number of bearings  55  may support the shaft  45  about the generator  50 . The generator  50  may be in communication with an electric power grid  60  and the like via a generator circuit breaker  65 . Other components and other configurations may be used herein. 
         [0012]    The gas turbine engine  10  may use natural gas, liquid fuels, various types of syngas, and/or other types of fuels and blends thereof. The gas turbine engine  10  may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine  10  may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. 
         [0013]    In the present example, the generator  50  also may be used as a synchronous condenser system  100  as may be described herein. Instead of using a starting motor and the like as described above, the synchronous condenser system  100  may be brought up to speed by the gas turbine engine  10 . Once up to speed, the shaft  45  may remain attached to the gas turbine engine  10  and spin freely. The gas turbine engine  10  thus may provide active power in an active power mode and reactive power in a synchronous condenser mode. 
         [0014]    An example of the operation of the synchronous condenser system  100  is shown in the flow chart of  FIG. 2 . At step  110 , the gas turbine engine  10  may be accelerated to full speed no load conditions via a static start or other types of conventional starting procedures. At step  120 , the generator circuit breaker  65  may be closed once the generator  50  reaches the frequency, the voltage, and/or the phase angle of the electric power grid  60 . At step  130 , the generator  50  now may produce power for the electric power grid  60  in the active power mode. At step  140 , the flow of fuel  30  may be turned off to the combustor  25  and the compressor  15  may operate at minimal conditions, i.e., starting bleeds may be open, inlet guide vanes may be set at low positions, and the like. At step  150 , the controls of the generator  50  may be set to begin operation as the synchronous condenser system  100 . At step  160 , the synchronous condenser system  100  may begin providing megavars to the electric power grid  60 , i.e., reactive power (volt-amperes reactive) in the synchronous condenser mode. The synchronous condenser system  100  thus may produce or absorb reactive power in the synchronous condenser mode with the gas turbine engine  10  attached to the spinning shaft  45 . At step  170 , the gas turbine engine  10  may be restarted if desired by refueling and following conventional restart procedures. The gas turbine engine  10  thus may again produce active electrical power in the active power mode. 
         [0015]    The gas turbine engine  10  thus provides both active and reactive power to help provide grid stability. The generator  50  provides active power while in the active power mode and reactive power while in the synchronous condenser mode. Moreover, the use of the synchronous condenser system  100  also provides improved turndown capability and a reduction in overall emissions. Gas turbine engines typically have a minimum load required to remain in emissions compliance. The use of the synchronous condenser system  100  allows a utility to stay synchronized with the electric power grid but with the fuel turned off and, hence, zero emissions. The gas turbine engine  10  may be refueled and provide active power when needed. The gas turbine engine  10  thus may use the synchronous condenser system  100  without the use of a clutch or disengagement of the shaft  45  and the space required to do so. The synchronous condenser system  100  and the methods described herein may be original equipment or part of a retrofit. The synchronous condenser system  100  thus provides grid stability, emissions turndown, and load rejection/load shedding in an efficient manner without the use of additional mechanical and/or electrical components and the space generally required. 
         [0016]    It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.