**AIM:**

To become familiar with modelling and analysis of the frequency and tie-line flow

dynamics of a power system without and with load frequency controllers (LFC) and to design

better controllers for getting better responses.

**THEORY:**

Active power control is one of the important control actions to be perform to be normal

operation of the system to match the system generation with the continuously changing system

load in order to maintain the constancy of system frequency to a fine tolerance level. This is one of

the foremost requirements in proving quality power supply. A change in system load cases a

change in the speed of all rotating masses ( Turbine – generator rotor systems) of the system

leading to change in system frequency. The speed change form synchronous speed initiates the

governor control (primary control) action result in all the participating generator – turbine units

taking up the change in load, stabilizing system frequency. Restoration of frequency to nominal

value requires secondary control action which adjust the load - reference set points of selected (

regulating) generator – turbine units. The primary objectives of

automatic generation control

(AGC) are to regulate system frequency to the set nominal value and also to regulate the net

interchange of each areas to the scheduled value by adjusting the outputs of the regulating units.

This function is referred to as load – frequency control(LFC).

**PROCEDURE:**

1. Enter the command window of the MATLAB.

2. Create a new Model by selecting File - New – Model

3. Pick up the blocks from the simulink library browser and form a block diagram.

4. After forming the block diagram , save the block diagram.

5. Double click the scope and view the result.

**EXERCISE:**

1.An isolated power station has the following parameters

Turbine time constant tT = 0.5sec

Governor time constant tg = 0.2sec

Generator inertia constant H = 5sec

Governor speed regulation = R per unit

The load varies by 0.8 percent for a 1 percent change in frequency , i.e,D = 0.8

(a) Use the Routh – Hurwitz array to find the range of R for control system stability.

(b) Use MATLAB to obtain the root locus plot.

(c) The governor speed regulation is set to R = 0.05 per unit.The turbine rated output is 250MW

at nominal frequency of 60Hz. A sudden load change of 50MW( PL = 0.2 per unit) occurs.

(i) Find the steady state frequency deviation in Hz.

(ii) Use MATLAB to obtain the time domain performance specifications and the frequency

deviation step response.

**RESULT:**

Finally, became familiar with modelling and analysis of the frequency and tie-line flow

dynamics of a power system without and with load frequency controllers (LFC) and to design

better controllers for getting better responses.

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