Turbine-governor control is crucial for maintaining power system stability by balancing turbine mechanical power output with electrical load demand. This mechanism ensures that generator frequency and rotor speed are within acceptable limits during load variations. Turbine-generator units store kinetic energy due to their rotating masses; this energy is released to meet the load requirement when the load increases. The electrical torque of turbines rises to meet the demand, whereas the mechanical torque remains constant initially, causing turbine-generator deceleration, a drop in rotor speed, and a corresponding drop in electrical frequency.
Generator frequency serves as a control signal for turbine mechanical output power. The steady-state frequency-power relation shows that changes in turbine mechanical power output are proportional to frequency deviation and changes in reference power settings. The regulation constant is the slope of the relationship between frequency deviation and mechanical power output change, typically expressed in Hz/MW, with a standard value of 0.05 per unit.
A turbine-governor block diagram includes a regulation constant block that converts frequency deviation into power output change, a time delay block modeling governor-associated delays, and speed reference input and output power limiters.
For wind turbines, power output is controlled by changing the blade pitch angle. When wind power exceeds rated capacity, blades are pitched to limit mechanical power. For Type 3 and Type 4 wind turbines, pitch control involves measuring turbine speed, combining signals for desired speed, electrical output, and setpoint power, and adjusting the blade angle to maintain desired power output.
Effective turbine-governor control ensures stable power system operation by balancing mechanical power with electrical load, maintaining rotor speed and generator frequency, and providing rapid responses to load changes to prevent instability.
