Load Frequency control

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.

8. Load frequency control of the Isolated power
system is

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.

10. AGC of a single area:

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.

14. Thank you
Presented by
S.L.D.Saisree