A New Control Method for the Multi-Area LFC System Based on Port-Hamiltonian and Cascade System

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1218
A NEW CONTROL METHOD FOR THE MULTI-AREA LFC SYSTEM BASED ON
PORT-HAMILTONIAN AND CASCADE SYSTEM
N. Narasimhulu 1, M.Ganesh Babu 2, K.Swathi3, Dr. R. Ramachandra4
1,3 Associate Professor and Head, Department of EEE, SKD College of Engineering, Gooty, AP, India
2,4 PG Student, SKD College of Engineering, Gooty, AP, India
--------------------------------------------------------------------------------***-------------------------------------------------------------------------------
Abstract: In this paper, a method based on the Port-
Hamiltonian (PH) system and cascade system that is
proposed to design some PID control laws for the multi-area
LFC system successfully works out the aforementioned
problem. Compared with the existed PID methods for the
multi-area LFC system, the proposed method has two
advantages, which are the decoupling of total tie-line power
flow and the robust disturbance rejection. Finally the
proposed method is simulated with and without reheated
turbine in the environment of Matlab/Simulink to validate
the advantages and robustness of proposed method.
Keywords: Interconnected Power System, Multi Area
Concept, PID controller
I. INTRODUCTION
Traditionally, frequency regulation in power system is
achieved by balancing generation and demand through
load following, i.e., spinning and non-spinning reserves.
The future power grid, on the other hand, is foreseen to
have high penetration of renewable energy (RE) power
generation, which can be highly variable. In such cases,
energy storage and responsive loads show great promise
for balancing generation and demand, as they will help to
avoid the use of the traditional generation following
schemes;
This can be costly and/or environmentally unfriendly. The
main goals of Load Frequency control (LFC) are, to
maintain the real frequency and the desired power output
(megawatt) in the interconnected power system and to
control the change in tie line power between control areas.
So, a LFC scheme basically incorporates an appropriate
control system for an interconnected power system, which
is heaving the capability to bring the frequencies of each
area and the tie line powers back to original set point
values or very nearer to set point values effectively after
the load change. This is achieved by the use of
conventional controllers. But the conventional controllers
are heaving some demerits like; they are very slow in
operation, they do not care about the inherent
nonlinearities of different power system component, it is
very hard to decide the gain of the integrator setting
according to changes in the operating point. Advance
control system has a lot of advantage over conventional
integral controller. They are much faster than integral
controllers and also they give better stability response
than integral controllers.
Traditional load frequency control (LFC) employs a
dedicated communication channel to transmit
measurement and control signals, while the LFC under
deregulated environment, such as bilateral contract
between generation companies (Gencos) and distribution
companies (Discos) for the provision of load following and
third-party LFC service, tends to use open communication
networks [1]–[4].
The load Frequency Control problem of an interconnected
power system is a well defined problem. The system is
divided into groups of generators which are
interconnected by tie--lines. Each group of generators is
called an area, and each area must be able to meet its own
load changes and any import or export targets set by the
controllers in advance. Each area has its own response
characteristics which relate the area frequency and total
generation for load changes on the specific area. This curve
is the regulation curve of an area and represents the area
gain (in MW /Hz). The area gain or regulation is a direct
measure of the effects of all the governors on the prime
movers within the area, and plays an important part in the
steady-state and dynamic performance of the system.
II. LOAD FREQUENCY CONTROL
The purpose of load frequency control loop is to achieve
power balance between generation and demand by load
tracking using speed governors. Under steady state
condition, the generator supplies power to the load. The
system will be under equilibrium i.e., the generator
delivers constant power and the turbine provides constant

accelerating torque. The equilibrium will be affected when
the system is subjected to the load change.
When there is an increase in load, the turbine generator
set will decelerate. This deceleration leads to the change in
frequency i.e. decrease in frequency. Similarly, during
removal of load, the turbine generator set will accelerate.
This leads to the incremental increase in frequency. Either
increase in load or decrease in load, the frequency is
subjected to change. This makes frequency to be an
indirect indicator to do the power balance.
Basically two types of inner control loops are there in LFC
as shown in Figure 1. They are primary control and
secondary control loop. The primary control loop adjusts
the turbine power based on frequency change using
control valve. This loop works much faster. The response
time will be in seconds. The loop does only coarse on
frequency. The secondary control loop eliminates the small
error in frequency. It works after the control action of
primary loop completes. It does the control action through
speed changer until the frequency error becomes zero. It
also controls the net power interchange between the
power pool members.
Figure 1: Schematic diagram of LFC
III. MULTI-AREA POWER SYSTEM MODEL
In a two area interconnected power system, where the two
areas are connected through tie lines, the control area are
supplied by each area and the power flow is allowed by the
tie lines among the areas. Whereas, the output frequencies
of all the areas are affected due to a small change in load in
any of the areas so as the tie line power flow are affected.
So the transient situation information’s of all other areas
are needed by the control system of each area to restore
the pre defined values of tie line powers and area
frequency. Each output frequency finds the information
about its own area and the tie line power deviation finds
the information about the other areas.
Applying the swing equation of a synchronous machine to
small perturbation, we have:
(1)
Or in terms of small deviation in speed
(2)
Figure 2: Mathematical modeling block diagram for
generator
The speed-load characteristic of the composite load is
given by:
(3)
The model for the turbine relates the changes in
mechanical power output ΔPm to the changes in the steam
valve position ΔPV.
(4)
The typical speed regulation of Governors is 5 to 6
percentage between no load and full load.
(5)
Or in s- domain
(6)
The command ΔPg is transformed through hydraulic
amplifier to the steam valve position command ΔPV. We
assume a linear relationship and consider simple time
constant τg we have the following s-domain relation:

(7)
Overall block diagrams from earlier block diagrams for a
single system as shown in Figure 3.
Figure 3: Mathematical Modeling of Block Diagram of
single system consisting of Generator, Load, Prime Mover
and Governor
Figure 4 is a control block diagram for the ith area of a
multi area power system. Although a power system is
nonlinear and dynamic, the linearized model is permissible
in the load frequency control problem because only small
changes in load are expected during its normal operation.
The largest part used control strategy in industry is P-I-D
controller. It is used for various control problems such as
automated systems or plants. A PID-Controller includes
three different fundamentals, which is why it is at times
called a three term controller. Proportional control,
Integral control and Derivative control is the expansion of
PID.
To meet up different design specifications for the system,
PID control is able to put into operation. These can include
the settling and rise time plus the accuracy and overshoot
of the system step response. The three stipulations should
be measured separately to realize the function of a
feedback controller for PID.
IV. SIMULATION RESULT ANALYSIS
In this section, simulations are given to demonstrate the
validity and advantage of the proposed method. To prove
the validity of the proposed method, a two-area LFC power
system (1) with non-reheated turbines is considered,
which rates of areas 1 and 2 are 1000 MW and 800 MW,
respectively. The synchronizing coefficients T12 =T21 = 0.2
p.u. MW/Hz. The matlab block diagram is shown in Figure
4.
Figure 4: Simulink Block diagram
When t ≥ 3s, there are load demands ΔPL1 = ΔPL2 = 0.01
p.u.MW for the two Areas 1 and 2, respectively. It is
necessary to point out that the overshoot and responding
speed of ΔPtie,i are small and fast, respectively. Thus, the
proposed method is effective and is shown in Figure 5.
Figure 5: Frequency response for LFC two-area with non-
reheated turbine
To prove the advantages of the proposed method, a four
area LFC system with non-reheated turbines containing
four areas is considered, as shown in Figure 6. Areas 1, 2
and 3 are interconnected with each other, while Area 4 is
only connected with Area 1.
Figure 6: Simplified diagram of a four-area power system
Figure 6 is simulated the response curves related to
frequency is presented in Figure 7 & Figure 8.
FREQ1
FREQ2
P TIE
PM1
PM2
num(s)
s
num(s)
den(s)
num(s)
den(s)
1
0.4s+1
1
0.44s+1
-K-
-K-
-K-
-K-
-K-
-K- -K-
-K-
-K-
-K-
1
0.06s+1
1
0.08s+1
PID
PID
0 5 10 15 20
-20
-15
-10
-5
0
x 10
-3
Time (sec)
frequency(Hz)
delta f1 delta f2

(a) Frequency response of Area1
(b) Frequency response of Area2
(c) Frequency response of Area3
(d) Frequency response of Area4
Figure 7: Frequency response curves of four area power
system with non-reheated turbines
(a) Frequency response of Area1
(b) Frequency response of Area2
(c) Frequency response of Area3
(d) Frequency response of Area4
Figure 8: Frequency response curves of four area power
system with reheated
0 5 10 15 20 25 30 35 40 45 50
-15
-10
-5
0
5
x 10
-3
Time(sec)
deltaf1(Hz)
Proposed
Conventional
0 5 10 15 20 25 30 35 40 45 50
-15
-10
-5
0
5
x 10
-3
Time (sec)
deltaf2(Hz)
Proposed
Conventional
0 5 10 15 20 25 30 35 40 45 50
-15
-10
-5
0
5
x 10
-3
Time (sec)
deltaf3(Hz)
Proposed
Conventional
0 5 10 15 20 25 30 35 40 45 50
-20
-15
-10
-5
0
5x 10
-3
Time (sec)
Frequency(f)
Proposed
Conventional
0 50 100 150 200
-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
Time (sec)
deltaf1(Hz)
Proposed
Conventional
0 50 100 150 200
-8
-6
-4
-2
0
2
4
x 10
-3
Time (sec)
deltaf2(Hz)
Proposed
Conventional
0 50 100 150 200
-20
-15
-10
-5
0
5
x 10
-3
Time (sec)
deltaf3(Hz)
Proposed
Conventional
0 50 100 150 200
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
Time (sec)
deltaf4(Hz)
Proposed
Conventional

V. CONCLUSION
In this paper, a control method based on the PH system
and cascade system for the multi-area LFC system is
proposed. In short, compared with the traditional
methods, the proposed method applies the structure and
energy properties of multi-area LFC system to design a
control law, which successfully works out the problem on
how to effectively utilize the total tie-line power flow.
Simulation results validate the effectiveness of the
proposed solution under different operating modes.
REFERENCES
[1]. S. K. Pandey, S. R. Mohanty, and N. Kishor, “A
literature survey on load frequency control for
conventional and distribution generation power
systems,” Renew. Sustain. Energy Rev., vol. 25, pp.
318–334, 2013.
[2]. S.Ali Pourmousavi and M. Hashem Nehrir,
“Introducing dynamic demand response in the
LFC model,” IEEE Trans. Power Syst., vol. 29, no. 4,
pp. 1562–1571, Jul. 2014.
[3]. A. Safaei, H. Mahdinia Roodsari, and H. Askarian
Abyaneh, “Optimal load frequency control of an
island small hydropower plant,” in Proc. 3rd Conf.
Therm. Power Plants, 2011, pp. 1–6.
[4]. M. Rahmani and N. Sadati, “Hierarchical optimal
robust load-frequency control for power systems,”
IET Gener., Transm. Distrib., vol. 6, no. 4, pp. 303–
312, 2012.
[5]. M. Farahani, S. Ganjefar, and M. Alizadeh, “PID
controller adjustment using chaotic optimization
algorithm for multi-area load frequency control,”
IET Control Theory Appl., vol. 16, no. 13, pp.
1984–1992, 2012.
[6]. W. Tan, “Unified tuning of PID load frequency
controller for power systems via IMC,” IEEE Trans.
Power Syst., vol. 25, no. 1, pp. 341–350, Feb. 2010.
[7]. W. Tan, “Decentralized load frequency controller
analysis and tuning for multi-area power
systems,” Energy Convers. Manag., vol. 52, no. 5,
pp. 2015–2023, 2011.
[8]. S. Saxena and Y. Hote, “Load frequency control in
power systems via internal model control scheme
and model-order reduction,” IEEE Trans. Power
Sys., vol. 28, no. 3, pp. 2749–2757, Aug. 2013.
[9]. Y. Mi, Y. Fu, C. Wang, and P. Wang, “Decentralized
sliding mode load frequency control for multi-
area power systems,” IEEE Trans. Power Syst.,
vol. 28, no. 4, pp. 4301–4309, Nov. 2013.
[10]. D. Rerkpreedapong, A. Hasanovic, and A. Feliachi,
“Robust load frequency control using genetic
algorithms and linear matrix inequalities,” IEEE
Trans. Power Syst., vol. 18, no. 2, pp. 855–861,
May 2003.
[11]. A. Khodabakhshian and M. Edrisi, “A new robust
PID load frequency controller,” Control Eng.
Pract., vol. 16, no. 9, pp. 1069–1080, 2008.
[12]. C. Ning, “Robust H∞ load-frequency control in
interconnected power systems,” IET Control
Theory Appl., vol. 10, no. 1, pp. 67–75, 2016.
[13]. T. H. Mohamed, H. Bevrani, A. A. Hassan, and T.
Hiyama, “Decentralized model predictive based
load frequency control in an interconnected
power system,” Energy Convers. Manag., vol. 52,
no. 2, pp. 1208–1214, 2011.
[14]. H. Yousef, K. AL-Kharusi, Mohammed H. Albadi,
and N. Hosseinzadeh, “Load frequency control of a
multi-area power system: An adaptive fuzzy logic
approach,” IEEE Trans. Power Syst., vol. 29, no. 4,
pp. 1822–1830, Jul. 2014.
[15]. A. Ersdal, L. Imsland, and K. Uhlen, “Model
predictive load-frequency control,” IEEE Trans.
Power Syst., vol. 31, no. 1, pp. 777–785, Jan. 2016.
[16]. H. Liu, Z. Hu, Y. Song, and J. Lin, “Decentralized
vehicle-to-grid control for primary frequency
regulation considering charging demands,” IEEE
Trans. Power Syst., vol. 28, no. 3, pp. 3480–3489,
Aug. 2013.
[17]. Y. Mu, J. Wu, J. Ekanayake, N. Jenkins, and H. Jia,
“Primary frequency response from electric
vehicles in the Great Britain power system,” IEEE
Trans. Smart Grid, vol. 4, no. 2, pp. 1142–1150,
Jun. 2013.

[18]. T. Pham, H. Trinh, and L. Hien, “Load frequency
control of power systems with electric vehicles
and diverse transmission links using distributed
functional observers,” IEEE Trans. Smart Grid, vol.
7, no. 1, pp. 238–252, Jan. 2016.
[19]. H. Bevrani and P. Daneshmand, “Fuzzy logic-
based load-frequency control concerning high
penetration of wind turbines,” IEEE Syst. J., vol. 6,
no. 1, pp. 173–180, Mar. 2012.
[20]. H. Bevrani, P. Daneshmand, P. Babahajyani, Y.
Mitani, and T. Hiyama, “Intelligent LFC concerning
high penetration of wind power: Synthesis and
real-time application,” IEEE Trans. Sustain.
Energy, vol. 5, no. 2, pp. 655–662, Apr. 2013.
BIOGRAPHY:
Mr. N. Narasimhulu has completed his
professional career of education in B.
Tech (EEE) from JNTU Hyderabad in the
year 2003. He obtained M. Tech degree
from JNTU, HYDERABAD, in year 2008.
He is pursuing Ph. D in the area of power
system in JNTU Anantapuramu. He has
worked as Assistant Professor from 2003-2008 and at
present working as an Associate Professor and Head of the
EEE Department in Srikrishna Devaraya Engineering
College, Gooty of Anantapuramu district (AP). He is a life
member of ISTE, FIE, IEEE. His areas of interests include
Electrical Power Systems, Electrical Circuits and Control
Systems
M.GANESH BABU has completed his
professional career of education in B.E
(EEE) at Acharya Institute of
Technology,Bangalore and pursuing
M.Tech from Sri Krishnadevaraya
engineering college, Gooty,
Anantapur(AP). He is interested in
Electrical Power Engineering .
K.SWATHI has 3 years experience in
teaching in graduate and post graduate
level and at present she is working as an
Assistant professor in the department of
EEE ,Sri Krishna devaraya Engineering
College, Gooty, AP, India.
Dr. R. RAMACHANDRA has completed
his professional career of education in B.
Tech (MECHANICAL) from JNTU
Hyderabad. He obtained M. Tech degree
from JNTU, Hyderabad. He obtained Ph.
D degree from JNTU, Hyderabad At
present working as Professor and
Principal in Sri krishna Devaraya
Engineering College, Gooty of Anantapuramu district (AP).

A New Control Method for the Multi-Area LFC System Based on Port-Hamiltonian and Cascade System

More Related Content

What's hot (18)

Similar to A New Control Method for the Multi-Area LFC System Based on Port-Hamiltonian and Cascade System (20)

More from IRJET Journal (20)

Recently uploaded (20)

A New Control Method for the Multi-Area LFC System Based on Port-Hamiltonian and Cascade System