Automatic generation control

The remaining units would be controlled with speed droop to share the load in proportion to their ratings.

[1] Turbine generators in a power system have stored kinetic energy due to their large rotating masses.

All the kinetic energy stored in a power system in such rotating masses is a part of the grid inertia.

Since the mechanical power of these turbines correlates with the delivered electrical power, the turbine generators have a decrease in angular velocity, which is directly proportional to a decrease in frequency in synchronous generators.

The purpose of the turbine-governor control (TGC) is to maintain the desired system frequency by adjusting the mechanical power output of the turbine.

Load-frequency control (LFC) is employed to allow an area to first meet its own load demands, then to assist in returning the steady-state frequency of the system, Δf, to zero.

[3] Load-frequency control operates with a response time of a few seconds to keep system frequency stable.

The goal of economic dispatch is to minimize total operating costs in an area by determining how the real power output of each generating unit will meet a given load.

An economic dispatch algorithm will run every few minutes to select the combination of generating unit power setpoints that minimizes overall cost, subject to the constraints of transmission limitation or security of the system against failures.

[5] Further constraints may be imposed by the water supply of hydroelectric generation, or by the availability of sun and wind power.