 Open Access
 Total Downloads : 1630
 Authors : M. Lokanatha, K. Vasu
 Paper ID : IJERTV3IS110621
 Volume & Issue : Volume 03, Issue 11 (November 2014)
 Published (First Online): 17112014
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Load Frequency Control of Two Area Power System using PID Controller
M. Lokanatha1
PG scholar, Department of EEE, Madanapalle institute of Technology and science,
Chittoor, A.P, India.
K. Vasu 2
Assistant professor, Department of EEE, Madanapalle institute of Technology and science, Chittoor, A.P, India.
Abstract–Recently, PID controller is widely used for different applications. In this project a particle swarm optimization tuned Proportional Integral Derivative (PSO PID) controller has been proposed. The performance of the proposed controller has been compared with the other classical controllers under different loading conditions. It is shown the performance PID controller tuned with Particle swarm algorithm was better than classical controller in terms of transient stability
Keywords: LFC, proportional integral controller, PSOPID controller transient stability of LFC.

INTRODUCTION
Modern days of the electrical power system are interconnected to neighboring power plants. Each power plant to generate own electrical power generation, during maximum load conditions all plants share electrical power through Tieline control. Because, if load demand of the plant increases [12]. This can be effect on the power angle delta, delta angle decreases due to speed of the generator decreases; speed is directly proportional to the frequency. Hence the load demand is increase frequency of the system is decreases. Once frequency exceeds the within the limits

MATHEMATICAL MODELING OF LFC
i.e. 50+5% HZ, the entire power system goes to blackout conditions and alternators comes to rest position.
The power systems, frequency are dependent on active power and voltage dependence on reactive power limit. The control power system is separated into two independent problems. The control of frequency by active power is called as load frequency control (LFC) [34]. An important task of LFC is to maintain the frequency deviation constant against due to continuous variation of loads, which is also referred as un known external load disturbance. Power exchange error is an important task of LFC. Generally a power system consists of several generating units connected together; these generating units are interconnected through tielines to become fault tolerant. This use of tieline power creates a new error in the control problem, which is the tie line power exchange error. Area controller error (ACE) is play major role in interconnected power system and also minimizing error functions of the given system. In this paper particle swarm optimization tuned PID controller is proposed and performance of the load frequency control on the two area power system and also performance of the proposed PSOPID controller as compared to conventional PI and PID controller.
Control Area 1
Control Area 2
The power transfers from area 1 to area 2 are
V1 V 2
V1, 1,
V2, 2,
ptie12
X12
sin(1 2) ——— (1)
Ptie12, X12
Tie line X12=X21
Ptie21, X21
If the change in load demands of two areas there will be incremental change in power angle.1 and 2 be the incremental changes in 1 and 2 the Change in power is
Fig 1: Two Area power system Control block diagram
ptie12 ptie12
V1 V 2
X
sin[(1 1) ( 2 2)
For the two Area power systems is
2H d
— (2)
12
V1 V 2
PG PD
f 0 dt f Bf Ptie12
ptie12 X
cos(1 2)(1 2) — (3)
P (s) P (s) 2Hs d f (s) Bf (s) P
(s)
12
V1 V 2
G D f 0 dt
tie12
T12 X
cos(1 2) — (4)
* P1
P (s) P
(s) P
(s)
12
P ( p.u) T
(1 2) — (5)
f 1(s) G1 D1 Tie12 —13)
B1( 2H1s 1)
tie12 12
V1 V 2
P (
) — (6)
f 0B1
k ps
– (14)
max12 X 1 2
f 1(s) [PG1(s) PD1(s) PTie12 (s)] 1 sT s
12
P Where Kps=1/B1 and Tps= 2H/B1f0
p
12
T max12 cos(1 2) — (7)
P1
d
Similarly
f 2(s) [P
(s) P
(s) P
(s)]
k ps
—— (15)
2f —– (8)
dt
G2 D2
Tie21
1 sTps
Incremental tie line power output of area1
A power system can be divided into various areas each area
Ptie12 (P.U ) 2T12 (
f 1
s
f 2
s
) ——– (9)
connected into its neighboring areas through tielines.[7] Load frequency control means to control the Active power and frequency kept constant while any load deviations occurring on
On taking Laplace transform on both side, then
the power system
Ptie21
(s) 2T12 ( f 2(s) f 1(s)) — (10)
s
T21 a12T12 Then
Ptie21
(s) 2T21 (f 1(s) f 2(s)) — (11)
s
According to swing equation [5].Let PD is increases in load at area 1 the power balance is
PG

PD
2H d f Bf — (12)
f 0 dt
Where
H Inertia constant, f0 Nominal frequency,
f change in frequency, B Area parameter
Area control error plays a major role in interconnected
Fig 2: Block diagram of two area interconnected power system with controller
N
power system, because controller input is Area control error.
ACEi
j1
Pij Bii ——————— (16)
Where is the speed deviation
N is number of areas interconnected areas i,
Pij is the power deviation between areas i and j from the scheduled values.
Bi
Di ——————————— (17)
1
R
i


PARTICLE SWARM OPTIMIZATION
James Kennedy an American Social Therapist alongside Russell C.Eberhart developed another evolutionary computational strategy termed as Molecule Swarm Advancement in 1995.The methodology is suitable for taking care of nonlinear issue. The methodology is focused around the swarm conduct, for example, flying creatures discovering sustenance by rushing. An essential variety of the PSO calculation satisfies desires by having a masses (called a swarm) of candidate result (called particles). These particles are moved around in the interest space according to a few essential formulae. The advancements of the particles are guided by their own particular specific best known position in the request space and furthermore the entire swarm's best known position. Modeling of
f1and f2 applied on partial swarm optimization algorithm.
1.2S5 (1.072S 4Kd 1.2S 4Kp) (2.06S3Kd
10.72KpS3 1.2S3Ki) (0.12S 2Kd 2.06S 2Kp
Bi is frequency bias factor.
f 1
1.072KiS 2 ) 0.12KpS 2.06KiS 0.12Ki 5 4
(60 35.28Kd )S S (22.08Kd 24.72Kp
54.8) S3(42.43Kd 22.08Kp 24.72Ki
102.09) S 2 (2.472Kd 42.43Kp 24.08Ki
80.6) S (2.47Kp 42.43KI 0.12) 2.472Ki
Fig 3: Flow chart of PSO algorithm

SIMULATION AND RESULTS
The practical swam optimization tuned in proportional integral derivative controller using design of LFC in two area power system, the controller plays regulating power flow between different areas while holding frequency is
.
constant. The performance of the proposed controller has less peak value and quick settling time and improves the stability of the system
Fig 4: Frequency deviations of Area1 and Area2 with PI controller Fig 5: Frequency deviations of Area1 and Area2 with PID controller
Fig 6: Tieline power deviation of PI controller
Fig 7: Tieline power deviation of PID controller
Fig 8: Frequency deviations of Area1 and Area2 with PSOPID controller
Fig 9: Tieline power deviation of PSOPID controller
From Fig 8 and 9 shows, PSOPID controller using LFC on the power system at change in power of Area1 is 25% and change power of Area2 is 10% of the base load. The performances of PSO tuned proportional derivative controller tuned in LFC as quick settling time [9] i.e. area1 settling time is 18 sec and area2 settling time is 16 sec respectively. Peak overshoots of the area1 and area2 has
very less then compared to the PI and PID controllers as shown in fig 4 and 5 as PI controller applied to LFC and fig 6 and 7 shows to the PID controller applied to the LFC. Hence, the performances of PSOPID controller using LFC of the power system, reduces the error and improve the dynamic response of the system.
Fig 10: Comparison of Frequency in Area1 with PI, PID and PSOPID controllers
Fig 12: Comparison of Tieline power with PI, PID and PSO PID controllers
Table 1: summarized Area1 frequency deviation
Controller
Rise time (s)
Peak
overshoot
Settling
time(S)
PI
0.0075
0.015
35
PID
0.006
0.012
20
PSOPID
0.0055
0.011
16
Case Study:
Case 1: Change in Active power of Area1 is 10% and Area2 is 0% with PSOPID controller
Table 3: Valid proportional, integral and Derivative constants are shown below
Fig 11: Comparison of Frequency in Area2 with PI, PID and PSOPID controllers
From fig 10 and 11 shows, comparison of LFC of two area power systems with proportional integral, proportional integral derivative and practical swarm optimization tuned PID controller at area1 25% of change in load and Area2 is 10% of change in Load. By observing the wave forms of the following figures PSO tuned proportional integral derivative controller has better performance than that of the conventional PI and Conventional PID controller. The performance of the Rise time, peak time and settling time of the given system summarized different types of controllers.
Table 2: summarized Area2 frequency deviations
Controller
Rise time (s)
Peak oversho
Settling Time(s)
PI
0.0035
0.007
40
PID
0.0015
0.003
25
PSOPID
0.001
0.002
20
Case 2: Change in Active power of Area1 is 25% and Area2 is 10% with PSOPID controller
%
Change in Lo
Area
Kp
Ki
Kd
25%
Area1
0.2816
0.8179
0.2610
10%
Area2
2.5306
2.5026
2.5475
Table 4: Valid proportional, integral and Derivative constants are shown below
%
Change in Load
Area
Kp
Ki
Kd
10%
Area1
0.1458
0.6458
1.5468
0%
Area2
0.4121
0.5027
0.863
Fig 13: LFC on power system with PSOPID controller at PL1=10% and PL2=0% of change in Active power.
Fig 14: LFC on power system with PSOPID controller at PL1=25% and PL2=10% of change in Active power.
By comparing Fig 14 and Fig 15 shows, if change in Active power of both areas+ 25% and +10% of the base load, the response of the frequency deviation curves to
increases peak overshoot, more no of oscillations and Fast settling time compare to change in Active power of 10% and 0% of the base load.

CONCLUSION:
In this paper, it can be concluded that practical swarm optimization tuned proportional integral derivative controller give optimal value for load frequency control on the two area power system. The performance of the given proposed controller has more accurate than that of the other conventional PI and PID controller under different load conditions.
Therefore the proposed controller of two area power systems, the transient response was improved with less peak overshoot and settling time .The performance and robustness of proposed controller was analyzed for different change in load disturbance.
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