Input-delayed load-frequency control using discrete sliding mode with fast output sampling
Load-frequency control is type of control in power system where we try to follow load
demands from consumers by controlling the generation from power plants in
real time while keeping the system frequency at constant value of 50 Hz (60
Hz in the North America). Main problems in the LFC are:
- constantly changing consumption of power,
- time delays in the controller’s signal due to large distance between
controller and power plants.
system with LFCi
uncertainties and the presence of delay makes it
more difficult to achieve the satisfactory performance and stability of the
Input to the
controller is called ACE (Area Control Error) and it is calculated from the deviations of the power flow in the tie lines
between areas and frequency deviation from 50 Hz. Areas define desired power
flow one day in advance.
ACE signal has
the following form:
where is constant value.
difficulties caused by uncertainties and time delay we use sliding mode
control. It is widely used robust control technique and it’s proven to
be very effective dealing with those kind of
sampling with state estimationi
mode control is based on the assumption that all system states are known.
But, in the LFC, states are unknown and we have to estimate them from the
area’s output signals: frequency and tie line deviations. Estimation is done
by multiple sampling of the output signal during one period of the input
from sliding mode controller depends on the future value of system states and
future value of distance from the sliding surface:
of that, it is necessary to have some sort of predictor for prediction of the
of the controller