Lecture 6
AGC in a Multi Area System
J. Fisher (PhD)
Senior Lecturer
Multi Area Network
 In an interconnected (multi area) system, there will
be one ALFC loop for each control area (e.g
interconnection of POM (Rouna) and Ramu grids).
POM
RAMU
P12 is the power transferred over the tie-line
• For small deviation in the tie-line flow from nominal value,
Power Angle Curve
• where PS is the slope of the power angle curve at
operating angle
Ps is the slope of the power curve
the
at theinitial
initial operating angle
• For small deviation in Tie-line power
Ps is the synchronizing power coefficient at the initial operating
angle
The Tie-line power deviation takes on the form
Area 1
Area 2
Considering ∆f deviation only
Expression of Tie-Line Power Flow in a Two
Area Interconnected System
Consider a change in load demand ∆PD1 or ∆PL1 in area1
The steady state frequency deviation ∆f is the same for both areas.
That is:
∆f = ∆f1 = ∆f2
For Area1
∆Pm1 - ∆PD1 - ∆P12 = D1∆f
For Area 2
∆Pm2 + ∆P12 = D2∆f
∆P12 is the tie line power flow from Area1 to Area 2
The mechanical power depends on regulation, thus,
and
∆Pm1 - ∆PD1 - ∆P12 = D1∆f
∆Pm2 + ∆P12 = D2∆f
Solving for ∆f, we get (see next slide)
β1 = (D1+1/R1)
β2 = (D2+1/R2)
β1 and β2 are the composite
frequency response characteristic
In the case of a change in Area 2 load ∆PD2, we have
Frequency Bias Tie-line Control
Corrects for
Df only
Corrects for both ∆P12 + β∆f
Considering both ∆f and ∆P12 deviations
Strategy to cause both the frequency and tie-line deviations to
vanish
As in Single Area case, adopt INTEGRAL CONTROL but with the tieline deviation added to the AREA CONTROL ERROR
For this purpose the area control error (ACE) is used
For Area 1 ACE1 = ∆P12 + B1∆f
For Area 2 ACE2 = ∆P21 + B2∆f
The constants KI1 and KI2 are the integrator gains and B1 and B2 are the
frequency bias parameters
Do Solved Example 12.5 (Glover et al)
Assignment 1B
Problem 1: Do Example 12.5 (in textbook by H. Sadaat).
Problem 2: Do Problem 12.14 in textbook by Glover et al.
Problem 3: Do Problem 12.15 in textbook by Glover et al.
Problem 4: Do Problem 12.16 in textbook by Glover et al.
Problem 5: Do Problem 12.17 in textbook by Glover et al.
Problem 6: Do Problem 12.18 in textbook by Glover et al.
Problem 7: Do Example 12.7 in textbook by H. Sadaat).
Deadline: Monday 22/04/23.
END OF LECTURE