Power-Frequency & Var-Voltage Control of Hydro-Generating System
 |
| P-f and Q-v control of hydro-generating system |
in the real power system, the active and reactive power
demand are never steady and they continuously change over time.
Water input to the hydro-turbine should be continuously
regulated to match the active power demand so that the frequency of the system remains
constant.
Also, the excitation of the generator should be continuously
regulated to match the reactive power demand so that the terminal voltage
across generator terminals remains constant.
In modern power system, the frequency and the voltage regulating
system are automatic.
Power-Frequency control/Automatic Generation Control/MW control
This
control method is used to keep the real power in the system constant by
regulating frequency. When real power load connected to the generator terminal
increases then the generator current increases and the magnetic tie between the
rotor and stator of the generator also gets increased which causes decrease in
speed. The speed governor closed loop control system is used to sense the change in speed and open the
valve within prescribed limit automatically.
In practical generator, the automatic control system is
provided to regulate the amount of water delivery to turbine, which keeps the
system frequency constant.
Var-Voltage control method/AVR control
This control method maintains the system voltage within the
prescribed limit by adjusting the excitation of the generator. When the
reactive power demand increases, the voltage across generator terminals
decreases and the voltage sensor senses the decrease in voltage which is
compared with the reference voltage and error signal is generated. AVR provides
command signal to controller. The controller increases the dc excitation
current of the generator. So that, the terminal voltage increases until the
error is significantly small.
0 Comments