CHAPTER 1
INTRODUCTION
1.1. Introduction to Load Frequency Control
Automatic generation control (AGC) is very important issue for supplying
sufficient control, good quality and reliable power. Power systems consist of control
are representing a coherent group of generators i.e generators which swing in unison
characterized by equal frequency deviations. In addition to their own generations and
demand these control areas are interconnected through tie-lines for providing
contractual exchange of power under normal operating conditions. In a power system,
both active and reactive power demands are never steady and they continually change
with the rising or falling trend. Water input to hydro-generators must be continuously
regulated to match the active power demand, failing which the machine speed will
vary with consequent change in frequency and it may be highly undesirable. The
maximum permissible change in frequency is ±2%.
One of the control problems in power system operations is to maintain the
frequency and power interchange between the areas at their rated values. Automatic
generation control is to provide control signals to regulate the real power output of
various electric generators within a prescribed area in response to changes in system
frequency and tie-lie loading so as to maintain the scheduled system frequency and
established interchange with other areas. The performance of the automatic generation
control depends upon how various power generating units respond to these signals.
When generated load is smaller than load power, frequency will drop. When
generated load is larger than load power, frequency will rise. So Automatic
Generation Control (AGC) system is used to control the fluctuate of frequency.
A two area power system comprises power generations from hydro, thermal,
and gas sources in area-1 and area-2. An interconnected power system consists of
control areas which are connected to each other by tie lines. In a control area, all the
generators speed up or slow down together to maintain the frequency and relative
power angels to scheduled values in static as well as dynamic conditions .In case
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of an interconnected power system having two or more areas connected through tie
lines, each area supplies its control area and tie lines allow electric power to flow
among the areas. However, a load perturbation in any of the areas affects output
frequencies of all the areas as well as the power flow on tie lines. In modern large
interconnected systems, manual regulation is not feasible and therefore automatic
generation equipment is installed on each generator. The controllers are set for a
particular operating condition and they take care of small changes in load demand
without exceeding the limit of frequency. As the change in load demand becomes
large, the controllers must be reset either manually or automatically.
1.2. Aim and Objectives
The main objectives of Automatic Generation Control (AGC) are:
1. To know Automatic Generation Control (AGC) used in power generation
2. To maintain frequency and power interchange between control areas at
rated values
3. To maintain the balance between the generation and demand of a
particular power system
4. To maintain the transient deviations in area frequency and tie-line power
interchange
5. To provide zero steady state errors of these variables in a very short time.
1.3. Scope of the Thesis
In this thesis, Automatic Generation Control (AGC) is desired by using hand
calculation and MATLAB-Simulink. In hand calculation, governor speed regulation
and steady-state frequency deviation step response. This thesis is based on the load
frequency control caused by fluctuation power loads. This thesis purposes the
different between Load Frequency Control (LFC) and Automatic Generation Control
(AGC). Calculation results are described with MATLAB-Simulink software.
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1.4. Implementation Programs
Theoretical studies of load frequency control caused by fluctuation power
loads are described in this thesis. This thesis can be implemented according to study
how to use MATLAB-Simulink software, and how to solve load frequency control
problem using automatic generation control technique. This thesis can be
demonstrated the application of proportional integral derivative (PID) controller
technique for AGC of interconnected power systems with two areas characteristics.
1.5. Outlines of the Thesis
This thesis composed of five chapters. The Chapter one describes the
introduction of the thesis. Chapter two deals review of literature on AGC studies
related to power system models with PID techniques. Chapter three deal with the
mathematical modeling of Automatic Generation Control (AGC) systems. Chapter
four is described MATLAB Calculation and MATLAB Simulation for two area
system. Chapter five is described Discussion and Conclusion.
