Automatic Load Frequency Control

1. AUTOMATIC LOAD FREQUENCY CONTROL
AND AUTOMATIC LOAD DISPATCH
B.TECH ELECTRICAL ENGINEERING
MADAN MOHAN MALAVIYA UNIVERSITY OF TECHNOLOGY,
GORAKHPUR
Project Mentor
Professor S.K Srivastava
Electrical Engineering Department
Presented By
Utkarsh tiwari : 2019031150
Abhishek Kumar : 2019031005
Anubhav Soni : 2019031034
Shubham Pal : 2019031131

2. CONTENTS
❖Introduction
❖Load Frequency Control
❖Response of Load Frequency Control of an Isolated
Single area Power System
❖Response of Load Frequency Control of Two area
interconnected Power System
❖Conclusion
❖Reference

3. INTRODUCTION
➢ Changes in real power affect mainly the system frequency,
while reactive power is less sensitive to changes in frequency
and is mainly dependent on changes in voltage magnitude.
➢ Thus, real and reactive powers are controlled separately.
The load frequency control (LFC) loop controls the real power
and frequency.
➢ Whenever there is increase in the load, the Frequency decrease
and increases when the load is decreased.
➢ The frequency normally vary by about 5% between light load
and full load condition.

4. Load Frequency Control
➢ The operation objectives of the LFC are to
maintain reasonably uniform frequency to
divide the load between generators, and to
control the tie-line interchange schedules.
➢ The change in frequency and tie-line real
power are sensed, which is a measure of
the change in rotor angle δ, i.e., the error
Δδ to be corrected.
➢ The error signal, i.e., Δf and ΔPtie, are
amplified, mixed, and transformed into a
real power command signal ΔPv, which is
sent to the prime mover to call for an
increment in the torque

5. Response of Load Frequency Control of an Isolated
Single area Power System
➢ The load frequency control of power system with and without
controller should be analysed for its steady state and dynamic
response behaviour.
➢ Uncontrolled: without Controller
Data used are as follows:- Δ𝑃𝐷 = 0.01 𝑇 = 20 sec 𝐾p = 100 (Generator Gain)
𝐾𝑔 ∗ 𝐾𝑡 = 1 𝑇p = 20 sec. 𝑅 = 1/2

6. Fig:1.2 Response of Uncontrolled single area of isolated power system

7. Controlled Case of Single Area
➢ Before analyzing the controlled case of a single area power system, we
shall define "Control Area".
Control Area: The power pools in which all the generators are assumed to be
tightly coupled, i.e. they swing in "unison" with change in load or due to speed
changer settings. Such an area, where all the generators are running coherently,
is termed as "control area".
Integral Control: By using the control strategy shown in fig. [1.4], we can
control the intolerable dynamic frequency changes with changes in load and
also the synchronous clocks but not without error during transient period.
Fig: 1.4 Block diagram representation of single area Power System (controlled)
Data used are as follows:-
Δ𝑃𝐷 = 0.01 𝐾𝑖 = 0.312
𝑇 = .08 sec 𝑇𝑖 = 0.3sec.
𝐾𝑔 ∗ 𝐾𝑡 = 1
𝑇p=20sec. 𝑅 = 1/2
𝐾p = 100 (Generator
Gain)

8. Fig:1.5 Response of controlled single area of isolated Power System

9. Response of Load Frequency Control of
Two area interconnected Power System
➢ An extended power system can be divided into a number of
load frequency control areas inter connected by means of
tie lines. Consider a two area case connected by a single tie
line as illustrated as below :
➢ Power transmitted from the area 1
is given by:

10. ➢ Change in angle can be expressed as the integral of change
in frequency:
➢ In general load model ,the incremental power
balance equation of area1 can be written as:

11. Fig 1.6 : Block diagram model of a two area interconnected system(Uncontrolled)
Data used are as follows:-
Δ𝑃d=0.01 Tt=0.3s 𝑇g=0.08 sec 𝐾p=100 (Generator Gain)
𝐾𝑔∗𝐾𝑡=1 𝑇p=20 sec. 𝑅1=-0.5
R2= -0.25

12. Uncontrolled Case of Two Area Interconnected system
Steady State Response
➢We consider first the uncontrolled case with ΔPC1 = ΔPCE = 0.
Suppose that the load in each area is suddenly increased by
incremental steps △ 𝑃01&Δ𝑃𝑂2∗ Due to the incremental loads,
we shall have frequency drops in the steady state and these
drops will be equal to:
Δ𝑓1stat = Δ𝑓𝑍stat = Δ𝑓stat
➢ Suppose a step load change occurs in area 1 only, then we get

13. Dynamic Response of Uncontrolled Case:-
➢The dynamic response of the two area, system is based on the
following assumptions.
➢Consider the case of two equal areas.
➢ Consider the turbine controller fast relative to the inertia part of
the system. GH = GT = 1.
➢Neglect the system damping i.e. Assume the load not to vary
with frequency D1 = D2 = 0.
➢Derive the following expression for the tie-line from the block
diagram:-

14. .
Fig 1.7: Load Frequency Response of Two Area interconnected system
(uncontrolled)
For area1 the frequency response f1 will be:-

15. Controlled case in Two Area interconnected System
➢ If frequency of two areas is to be controlled, the static
frequency drop is just one half of that of the isolated
operation of two systems If there is change in load in any
area, half of it will be shared by the other area.
➢ It is found that if a load changes in an area, the frequency
and interchange errors in that area have the same sign while
these opposite signs for the other area. Thus the relative
signs of the frequency and interchange deviations help to
identify the area where the load has changed.

16. Fig. 1.8: Load Frequency Response of Two Area Interconnected system (Controlled)
Data used are as follows:-
Δ𝑃d= 0.01 𝐾𝑖 = 0.312 𝑇g = .08 sec 𝑇𝑖 = 0.3sec. 𝐾𝑔 ∗ 𝐾𝑡 = 1 𝑇p=20sec.
𝑅1 = -1/2 𝐾p = 100 (Generator Gain)
R2= -0.025

17. Fig. 1.8: Load Frequency response of Two Area interconnected system System
(Controlled)

18. Conclusion
➢ Under normal operation the controllers keep the generator
operating around a pre-selected "normal" state with minimal
excursions.
➢ The dynamic models of all controllers that have been
discussed have therefore been linear.
➢ Simulation results have shown that the proposed approach
ensures viable evolutions to the overall power system with
respect to the prescribed operative constraints despite changes
in the loads and failure events.

19. References
➢ Research Paper on Load Frequency Control in Power System by
Md. AlAmin Sarker and A K M Kamrul Hasan - SEU Journal of
Science and
Engineering, Vol. 10, No. 2, 2016
➢ Power system Analysis by Hadi Saadat -The McGraw-Hill and
Schaum`s Elecctronic Tutors
➢ Research paper on Automatic Load Frequency Control by Shallu
Sharma and Jitendra Bhadoriya -International journal of
innovative
research in electrical, electronics, instrumentation and control
Engineering
➢ Research paper on Automatic Load Frequency Control of a Multi-
Area
Dynamic Interconnected Power System by Veerapandiyan
Veerasamy, Noor Izzri Abdul Wahab, Rajeswari Ramachandran
,Mohammad Lutfi Othman and Jeevitha Satheesh Kumar