Synchronous condensers may be utilized in a wide variety of applications, such as power generation. Typically, synchronous condensers may be utilized to adjust conditions on an electric power distribution grid. Synchronous condensing may be necessary to produce reactive power (vars) in order to maintain the voltage to deliver active power (watts) through transmission lines. Motor loads and other loads may require reactive power to convert the flow of electrons into useful work. When there is insufficient reactive power, the voltage may sag and it may not be possible to push the power demanded by such loads through the transmission lines. A synchronous condenser may be a specialized motor with an unattached rotor shaft that spins freely during operation. 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.
In power generation systems, synchronous generators may be coupled to and driven by gas turbine engines or other types of power sources to produce electrical energy. In some cases, it may be desirable to use generators as synchronous condensers to generate reactive power for or absorb reactive power from the electric power grid. Various approaches exist for converting a synchronous generator to operate as a synchronous condenser. According to one approach, the synchronous generator may be decoupled from the turbine rotor shaft of the gas turbine engine, and a starting motor or other driving mechanism may be provided to accelerate the rotor shaft of the synchronous generator to an operational speed. Potential problems with this approach may include a high added cost of providing and powering the starting motor, a significant amount of time required to install the starting motor, and/or a limited amount of space in which the starting motor may be installed and operated. According to another approach, the rotor shaft of the synchronous generator may be coupled to the turbine rotor shaft of the gas turbine engine via a clutch, such as an automatic overriding clutch, which may allow the generator rotor shaft to rotate relative to the turbine rotor shaft. Although this approach may be suitable in certain applications, the added cost of the clutch may be significant, the clutch may present reliability issues over time, and/or a limited amount of space may not allow for use of the clutch. Still other approaches may utilize other mechanisms for driving the generator rotor shaft and/or coupling the generator rotor shaft to the turbine rotor shaft, which may increase the complexity of the system, increase the cost of the system, and/or present reliability issues over time.
There is thus a desire for improved systems and methods for power generation synchronous condensing using a gas turbine engine and a synchronous generator. Such systems and methods may enable synchronous condensing function while avoiding one or more of the above-described problems experienced with existing approaches. In particular, such systems and methods may allow the synchronous generator to operate as a synchronous condenser with no or minimal additional hardware. In this manner, synchronous condensing function may be provided, either upon original manufacture or as a retrofit, at no or minimal added cost. Furthermore, such systems and methods may eliminate the need for a clutch or other similar mechanism coupling the generator rotor shaft to the turbine rotor shaft and thus may avoid potential reliability issues associated therewith.