Gas turbine engines are well known and widely used for electrical power generation, operating pumps and compressors, in aeronautical applications for thrust, and in still other applications. Control systems governing gas turbine engines receive many types of data from instruments onboard the gas turbine engine, and others coupled with equipment that is powered by the gas turbine engine. Operating properties in the nature of compressor discharge pressure, shaft speed, firing temperature, and still others relating to operation of the gas turbine engine are typically monitored. Electrical output of an electrical generator coupled with a gas turbine engine is also commonly monitored for various purposes. Due to the complexity of the machinery, the relatively harsh operating conditions, and an environment associated with significant signal noise, gas turbine engine control systems can be quite complex.
In one conventional strategy for controlling a gas turbine engine, data from onboard instruments such as temperature and shaft speed sensors is gathered, and a desired fueling rate determined according to a suitable control law in a closed loop fashion. While such conventional techniques have been suitable in certain engine systems for many years, when an engine load of the gas turbine engine changes, there is by necessity some delay in the ability of conventional control systems to observe and compensate for the engine load change. This is due to the fact that the response of engine process variables to an engine load change is not instantaneous, nor is the signal processing that is necessary to reliably observe the response. For instance, it has long been observed that when a gas turbine engine experiences a relatively sudden engine load change or transient, the shaft speed of the gas turbine engine, as well as other operating properties, will change in response. The control system will eventually react to the speed change and increase or decrease fueling, but typically not before the speed has increased or decreased to a greater extent or for a greater length of time than is considered optimal. Such excursions, commonly accompanied by fluctuations, in speed and various other parameters are undesired from the standpoint of efficiency and for other reasons.
U.S. Pat. No. 4,349,744 to Reuther et al. is directed to a system for operating multiple gas turbines for a coordinated dead load pickup, and discloses a specialized mode of operation where one turbine-generator is controlled as a lead unit, and operated in conjunction with the operation of a synchronized turbine-generator, with each connected to an auxiliary bus. The two units can then together be used for a load pickup from the bus, presumably to provide for a desired pattern of load sharing between the turbine-generator units. Reuther et al. may have provided some improvements as to how large load transients are shared among turbine-generator units. There remains ample room for other developments, however, respecting the monitoring and management of load transients on and among gas turbine engines.
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