Lec-5 Fundamentals of AGC

5/20/2018 Lec-5 Fundamentals of AGC

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Fundamentals of

Load Frequency Control (LFC)and

Automatic Generation Control(AGC)


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The system frequency reaches steady-state at a value

that causes the sum of the on-line generator output

MW to be equal to the system load MW.

With this type of governor Control (Primary Control),when the system load increases, the system

frequency decreases and visa versa.

How do we control frequency to 50HZ, no matter whatthe load is?

We need Secondary Control also

Limitation of Governor Control (Pr. Control)

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Governor with

Speed-droop

Feedback Loop

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(Ref. W&W p. 337)

By changing the load

reference set pointThe generators governor

characteristics

can be set to give

reference frequency fo

at any desired unitoutput.

The bas ic con tro l input to th e

generat ing un it as far as generat ion

contro l is co ncerned is the load

reference set po int (Raise/Lower).By adjusting this set point on each

unit, a desired unit dispatch can be

maitained while holding system

frequency close to the desiredvalue


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Speed-Changer Settings

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Steady-state speed characteristic

with speed changer

50

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Power output as a function of frequency

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Primary Control

Secondary Control

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How does the addition of the Raise/Lower Speed

Changer( Sec. Control) to the Governor Control (Pr.Control) facilitate the control of frequency?

Hint: It causes the sum of the on-line generator

output MW to be equal to the system load MWexactly at desired value of steady-state system

frequency.

Governor alone can not eliminate frequency errorcaused by load changes. Advantage of governor is its

quick response and reasonable frequency correction

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Primary Control and Secondary Control


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From a central control site, you increase or decrease

the no-load frequency set-points of generating unitsuntil the sum of the generated power is equal to the

present system load, then the frequency will stabilize

at 50HZ.

This form of supplemental control is called Automatic

Generation Control (AGC) and more specifically, Load

Frequency Control (LFC).

AGC, and LFC

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Automatic Generation Control, AGC

AGC is usually implemented in EnergyManagement System(EMS) of Energy

Control Centers(ECC).

The components of AGC in modern powersystem are:

Load Frequency Control(LFC)

Economic Dispatch(ED)

Interchange Scheduling(IS)

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To

50 Hz


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ACE Calculation


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Generation Allocation


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Losses, Loads, Export PowerGenerated, Import

50 Hz, in ourcountry

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Lec-5 Fundamentals of AGC

Documents

agc agc

control of frequency

components of agc

control25202018 lec

desiredvalue5202018

lfc105202018 lec

loadfrequency control

system frequency