1. INTRODUCTION
Power Engineer has the responsibility to deliver economically, adequate and
quality power to consumer. In order to achieve this, the power system must be
maintained at the desired operating level by suitable modern control strategies.
Load frequency control (LFC) is a simple mechanism to maintain or restore the
frequency and tie line power flow among the interconnected power systems
within the specified limit.
For safe, secure, reliable and economic operation, it is found necessary to
interconnect neighboring powers, forming power pools. In power system
network, power is exchanged between the utilities over the tie - lines by which
they are connected. In an interconnected network a disturbance in one line leads
to effects on the neighboring systems change in tie-line power and frequency
causing serious problem of load frequency control (LFC). This change in tie-line
power and frequency is called an area control error.
LFC is very important item in power system operation and control for sufficient
and reliable electric power with good quality. Many control strategies have been
proposed to achieve improved performance. The Integral and Proportional plus
Integral control approach is one such strategy. In this thesis proportional and
integral controller technique is employed for the design of an efficient load
frequency controller.

2. SCOPE AND OBJECTIVES
1. Zero steady - state error of area control error.
2. Ensure good transient response under disturbance.
3. Closed loop stability of the system to be assured.
4. Reliable operation and control of power system.
5. Controller must be easy for implementation.

3. DESIGN OF LOAD FREQUENCY CONTROLLER FOR TWO AREA
INTERCONNECTED HYDRO POWER SYSTEMS
Transfer Function Model of an Interconnected Two Area Hydro Power
Systems (Closed Loop)

4. DESIGN OF DIGITAL CONTROLLER
Proportional Controller:
Pout = Kp e(t)
Two Area Hydro Electric Power System - P controller Design
t
dtACEwJ
0
2
)(1

5. Integral Controller:
t
0
2
J dtACEi ACEi = Fi + Ptiei
Two Area Hydro Electric Power System - I controller design

6. PI Controller :
PI out = Kp ACEi + Ki ACEi
2 dt
Two Area Hydro Electric Power System - PI controller design

7. FLOW CHART

8. BLOCK DIAGRAM

9. Frequency Response for Area -1

10. Frequency Response for Area -2

11. Frequency Response for Area -1 and Area -2

12. PI APPLICATION TO POWER SYSTEMS
PI were used in many of the power system application such as
Reactive power and voltage control, Economic dispatch problem,
Power system reliability and security, Generation expansion
problem, State estimation, Load flow and optimal power flow,
Power system identification and control.
Other application to non-linear optimization problems are electric
machinery, capacitor and Facts placement , generator maintenance
and unit commitment scheduling, short term load forecasting,
generator contribution to transmission system etc.

13. CONCLUSION
PI controller has been successfully applied to tune the
parameters of load frequency control systems of the
proportional plus integral type. A two area interconnected
Hydro power system was assumed to demonstrate the
method. The Integral Square of the error (ISE) was used as
objective function.
The Design of Load Frequency Controller for an Inter-
Connected Two Area Hydro Power Systems was simulated
using MATLAB Simulink and the results were observed. The
responses of the power system with Proportional Integral
controller gain were simulated and their Peak Over Shoot and
Settling time were analyzed.

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15. Thanking You