Single area load frequency control by using pi,fuzzy logic control1
1. Single area Load Frequency Control :
a comparative study Based on PI and
Fuzzy logic controllers
By
S.L.D..Saisree
2. Contents
Main Theme Of the paper
Introduction
Reasons for Maintaining constant frequency
Load Frequency control
Single Area System
Automatic Generation Control (AGC)
Block diagram representation AGC of Single Area System
PI controller
Fuzzy Logic Control
Comparison Between PI and Fuzzy logic controllers
3. Main Theme of the paper
• This Paper is about the single area load frequency control of an
Isolated powersystem . The automatic control over the generation
by using controllers i.e., Proportional Integral Controller or Fuzzy
Logic controller.
• The frequency get improved by using the controller
when ever the load change occurs
• The comparison between the conventional ( PI controller) and
the fuzzy logic controller(FLC).
4. Introduction
Isolated power generating units leads in instability due to load variations and
there by the frequency changes.
Load Frequency Control (LFC) is a system to maintain reasonably uniform
frequency, by balancing the generation and demand
The Frequency sensor, electronic based controllers, Speed governor will operate
when there is change in frequency.
The integral controller is linear type controller, provides zero steady state error
(Δf =0)with less transient state performance.
Fuzzy logic controller is robust, nonlinear type, less cost than conventional
controllers and better transient performance.
The performance of the PI controller is compared with Fuzzy logic controller.
5. Why to maintain the frequency
constant?
The Machines will operate at different speed.
Steam turbine blades will damage.
Transformer losses are depends on the frequency.
protective and control equipment may operate case of under/over
frequency.
Electrical clocks used for the synchronous motors will lose
operation.
In continuous process industry it affects the process operation.
6. Load Frequency control
LFC is used give sufficient amount of the active power demand when
ever load change occurs & maintain the steady state frequency.
If we use only Speed governor we cannot achieve the steady state
frequency. It alone operate in other than steady state frequency.
To obtain the steady state frequency we use the controllers.
Control over the load is complex & that depends on the consumer
requirement.
Hence, generation is controller and maintained at constant frequency
when load variations occur.
7. Single area
A coherent area in which all generators supplying the sufficient
generation to the load.
Assume there is no tie line connection with any other area.
No connection with the grid
The generators are unison respond with the change in frequency.
9. Automatic Generation Control(AGC)
The control of the generation automatically by using the
controllers command power (ΔPc ) is given there by
generation will controlled.
In AGC the speed governor ,controllers either conventional or
fuzzy based controllers are used
Where as in manual control there is only speed governor
action is exists & no use of any controllers. (For smaller
generating units manual actions is preferred)
Under balanced condition the speed governor will not operate.
11. PI controller
PI controller is proportional + Integral controller.
It is the electronic based PI controller combination of the
Operational amplifier,Power ampilifier,inverter amplifier
It increases the type by 1 thus the steady state error will be zero.
The PI controller have poor transient performance (takes time to
make Δf =0)
All this conventional controllers are linear type i.e., the values will
change based on the operating condition.
12. Fuzzy Logic control
• Fuzzy logic is one of the soft computing method.
• Fuzzy means “ vagueness“& It deals with imprecision, uncertainty.
• Transient performance is improved than PI controller
13. Comparison
PI controller
• Transient state performance is
more(settle down time is slow)
• Not robust
• linear type
• Simple in construction
• Cost is high
• So such data is required.
Fuzzy Logic Controller(FLC)
• Transient state performance is
less(settle down time is fast)
• Robust
• Non linear type
• Complex
• Cost is low
• Requires more data for different
linguistic variables.