Electrical & Electronic Systems
Electrical & Electronic Systems
Electrical & Electronic Systems
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Abstract
The idea of applying distributed generation resources in distribution systems has become increasingly important
due to changes in the distribution systems. Optimal sizing, location, type and installation time of DGs for constructing
virtual power plant is one of the important subjects in applying distributed generation in the power system. In this paper,
a new method is presented for optimal placement and type of distributed generation units and long term system planning
aim to constructing virtual power plant. Minimizing the long term total cost of the system is considered as the objective
function. The impacts of applying demand response on expansion planning is also investigated. The Binary particle
Swarm Optimization (BPSO) method is used for solving this problem. In order to evaluate the efficiency of the proposed
method, the method is tested on the IEEE 33 bus distribution system.
Literature review
Many studied have been implemented with the aim of power
loss reduction. Genetic Algorithm (GA) [2], Tabu search [3], particle
swarm optimization [4,5] and combination of PSO and GA [6] are
some of methods which their objective function is loss reduction. In
[7] an improved reinitialized social structures PSO algorithm has been
developed for optimal placement of multiple DGs in a micro grid to
minimize the real power loss within voltage and power generation
limits. The analytical approach has been demonstrated in [8,9] to find
the optimal size and location of DG to minimize the real power losses
and enhancement in voltage profile.
In [10], the optimal sizing of a small isolated power system that
contains renewable and/or conventional energy technologies was
determined to minimize the systems energy cost. In [11], DG units
were placed at the most sensitive buses to improve the voltage stability.
In [12], to determine the optimal locations of DG units in distribution
system, a new multi-objective problem based on minimized power
losses, enhanced reliability and improved voltage profile has been
presented. Several papers have focused on the use of EAs (evolutionary
algorithms), analytical methods or load flow methods to optimize the
DG placement and its sizing [13,14].
The integration of DERs is another subject which affects the
operation of a power system network. In this situation, distributed
generation and controllable demand may have the opportunity to
participate in the operation of transmission and distribution networks.
However, the aggregation of many small-capacity generators into one
large power generation project could improve the economics of DERs.
J Electr Electron Syst
ISSN: 2332-0796 JEES an open access journal
If several DER units are linked together and are operated as one unit, the
concept is often called a Virtual Power Plant (VPP). There are two types
of a VPP. Commercial Virtual Power Plant (CVPP) is one type of VPP
operation [15]. The CVPP is a competitive market actor that manages
the DER portfolio(s) to make optimal decisions on participation
in electricity markets. From the commercial point of view, VPP as a
market agent seeks to obtain the maximum benefit from the generation
and the demand portfolio without considering the network constraints.
Technical Virtual Power Plant (TVPP) is another type of VPP operation
[16]. The TVPP takes into consideration also the operation of the grid.
The TVPP aggregates and models the response characteristics of a
system containing DERs, controllable loads and networks within a
single electric-geographical (grid) area. On the other hand, a TVPP
consists of some DERs from the same geographic location. In this case,
the impact of operation on the distribution network is also considered
[17].
Demand Response (DR) is one of the important parts of a VPP.
Demand response is established to motivate changes in electricity
consumption by end users. The main benefit of DR is the improvement
of power system efficiency, since a closer alignment between customers
electricity prices and the value they place on electricity is established
[18].
Citation: Bahrami S, Imari A (2014) Optimal Placement of Distributed Generation Units for Constructing Virtual Power Plant Using Binary Particle
Swarm Optimization Algorithm. J Electr Electron Syst 3: 127. doi:10.4172/2332-0796.1000127
Page 2 of 6
of DER that can be used to make contracts in the wholesale market and
to offer services to the system operator. The VPP integrates the capacity
of distributed energy resources and represents an operation strategy with
the combination of operation parameters of each DER. Also, VPP can
consider the effect of network in the output powers of integrated DGs.
Problem Formulation
d (1 + d) n
(1 + d) n 1
CF 8760
(2)
(3)
(4)
Constraints
In the optimal placement and sizing of DG units for constructing
VPP, the following constraints should be satisfied.
i.
Nbus
(5)
=
Pi
VV
i jYij cos( ij i + j )
Optimal placement of distributed generation units in the
i =1
distribution system is a very important subject for constructing virtual
Nbus
(6)
power plant. The problem to solve is to determine the optimal location =
Qi VV
i jYij sin( ij i + j )
i =1
and size of a given number of DG units. Since, the costs of the system
must be optimized, in this paper, the long term total cost of system
ii. Active and reactive power constraints of DG units:
including the production cost of DGs, cost due to purchasing active
The output active and reactive power of each DG units must be
power from the grid, DRs cost, upgrade cost of the system and the cost
between its minimum and maximum values:
of installing smart meters in the system are considered as the objective
min
max
function. The long time total cost of system is considered as following:
PDG
,i PDG ,i PDG ,i
(7)
Ymax 24 Gn
= TC
= CDG ,i , y ( PDG ,i , y (t ))
minimize : Total Cost
=y 1 =t 1 =i 1
Ymax 24
Ymax 24 N DR
Ymax
y =1
iii.
Pn , m ( , V ) Pn , m , max
iv.
(8)
Pm , n ( , V ) Pm , n , max
QG ,min QG QG ,max
(9)
(10)
Voltage constraints
If the voltages along the feeder are not satisfied, optimal sizing and
placement of DG are changed to the nearest values to take the feeder
voltages to the voltage limits. The voltage must be kept within standard
limits at each bus [20]:
Citation: Bahrami S, Imari A (2014) Optimal Placement of Distributed Generation Units for Constructing Virtual Power Plant Using Binary Particle
Swarm Optimization Algorithm. J Electr Electron Syst 3: 127. doi:10.4172/2332-0796.1000127
Page 3 of 6
Vmin V Vmax
(11)
Proposed Method
In this section, the proposed algorithm for optimal placement of
DG units for constructing virtual power plant in distribution system
is presented. The goals of the proposed method are determining the
optimal site, capacity, and type and installation year of each DG in
distribution system and long term expansion planning of distribution
system. In order to aim to the mentioned goals, the proposed algorithm
which shown in Figure 1 is presented. The proposed algorithm has 5
stages which are explained in following:
Stage 1: determining initial data
At the first stage of the proposed algorithm the initial data including
the configuration of understudy distribution system, power market
price, the operation cost of DG units and the peneteration value of
demand response is determined.
i
Vki +1 = .Vki + C1.R1 Plbest
X ki + C2 .R2 Pgilobal X ki
(12)
=
max ((max min ) / kmax ) k
(13)
X ki + Vki +1
(14)
Binary PSO
Figure 1: Algorithm flow chart.
Citation: Bahrami S, Imari A (2014) Optimal Placement of Distributed Generation Units for Constructing Virtual Power Plant Using Binary Particle
Swarm Optimization Algorithm. J Electr Electron Syst 3: 127. doi:10.4172/2332-0796.1000127
Page 4 of 6
particles are integers in {0,1} and Vki +1 ,since it is a probability, must
be constrained to the interval [0,1]. A logistic transformation S (Vki ) is
used to accomplish this modification.
1
S (Vki+1 ) = sig mod e(Vki+1 ) =
(15)
1 + exp(Vki+1 )
The resulting change in position then is defined by the following
rule:
if rand S (Vki +1 ) then : X ki +1 = 1 ;
else : X ki +1 = 0 ;
(16)
1 Bi Bmax
0 Pi Pi , max
(17)
(18)
Ti = {1, 2,..., T f }
(19)
0 Yi Ymax
(20)
Simulation Results
In this paper, in order to evaluate the performance of the proposed
method, the method is applied on IEEE 33 bus distribution system [23].
For this purpose, four DG is placed in distribution system by using the
proposed method and an expansion planning for distribution system is
performed. The results of proposed method are compared to case which
no DG are placed in the system. Then, in order to evaluate the impact
of demand response in distribution system, two penetration value of
demand response (10% and 13%) is considered in the system and the
system planning is performed.
Network information
The understudy system (IEEE 33 bus distribution system) is
presented in Figure 3. The market price is in [24]. It should be noted
that the rate of annual load growth is considered as a fixed rate and
equal to 5%. Also, it is supposed that all of DRs have a contract with
the owner of VPP. During the contract, the amount of fines paid by
customers is considered 10 percent more than the market price of
electricity. All of the lines of distribution systems are considered as
candidates for upgrading.
DG number
site
(Bus number)
Capacity
(KW)
Types of DG
Installation time
(year)
30
500
Micro-Turbine
18
500
Micro-Turbine
14
500
CombustionTurbine
25
500
Micro-Turbine
Citation: Bahrami S, Imari A (2014) Optimal Placement of Distributed Generation Units for Constructing Virtual Power Plant Using Binary Particle
Swarm Optimization Algorithm. J Electr Electron Syst 3: 127. doi:10.4172/2332-0796.1000127
Page 5 of 6
of 6th to 23rd buses (DRT=18) are equipped with telecommunicating and
measuring instruments. The cost of installation of instruments on every
bus (Cinst) is considered $3000 [22]. Penetration rate of DR in the every
mentioned bus is 10%. Therefore, while the congestion occurs in the
lines of the system, the owner of the VPP can cancel utmost to 10% of
the loads of every buses which equipped with DR. The result of 10 year
planning of system for 4 DG placement with 10% penetration of DR
in the system is presented in Table 2. In this case, no transferring line
needs to be expanded. Also, the long term total cost of the system is
16.18549 million dollars.
Capacity
(KW)
Types of DG
Installation time
(year)
Micro-Turbine
30
500
18
500
Micro-Turbine
14
500
CombustionTurbine
25
500
Micro-Turbine
Table 2: Results of 10 years planning of the system for 4 DG placement with 10%
penetration of DR in the system.
site
Capacity
DG number (Bus number)
(KW)
Installation time
(year)
Types of DG
30
500
Micro-Turbine
18
500
Micro-Turbine
14
500
CombustionTurbine
25
500
Micro-Turbine
Table 3: Results of 10 years planning of the system for 4 DG placement with 13%
penetration of DR in the system.
1.72
1.7
With DG, No DR
1.68
The cases which are studied in this paper evaluated the impact
of DG and DR presence in VPP. While there is no DG in the 33 bus
distribution system, the lines between 1-2and 2-3buses needs to be
bundled at 3rd and 10th years, respectively. But in the case that four DG
units is placed in the system, the need for expanding the lines of VPP is
completely canceled. This matter shows that installing DG units in the
system can lead to delay in expansion of the system. In the case presented
in section 4.5, the long term total cost of the VPP is decreased at 5.53%
in respect to case which no DG installed in the system. If penetration
rate of DR at a part of system loads is 10%, the expansion planning
of lines is delayed to 5th year. The delay is resulted by decreasing the
load DRs at 1-4 years. Also, it will be completely canceled by installing
one DG unit at 4th year. Also, the total cost of system in case presented
in 4.5 reduced in respect to the cases NO DG-NO DR and 4 DG-NO
DR 8.35% and 2/99%, respectively. In condition that rate of penetration
of DR in system increases to 13%, expansion of line between 1st and
2nd buses will be delayed by load peak shaving to 5th year of planning.
Finally, it will be completely canceled by installing one micro-turbine
unit in 5th year at 14th bus of VPP. The total cost of the system During
10 year planning in case DG-13%DR in respect to cases NO DG-NODR, DG-NO DR, DG-10% DR is decreased to 9.29%, 3.99% and 1.02%,
respectively.
Conclusion
In this paper a new method is presented for optimal placement of
distributed generation units for constructing virtual power plant. Also,
the impacts of presence of demand response have been investigated in
the system and on VPP planning. Minimizing the long-term cost of
VPP is considered as objective function. Hence, the production costs
of distributed generation units (consist of capital and investment cost,
operation and maintenance and fuel cost), the costs of expanding the
lines and purchasing energy from the grid is considered. The Binary
Particle Swarm Optimization (BPSO) method is used to solve the
optimization problem and minimizing the objective function. The
proposed method is applied for placing 4 distributed generation units
in IEEE-33 bus distribution network. In order to evaluate the impact
of demand response on system planning, some parts of loads of the
system have been equipped with DR. Then by means of the proposed
method, 10 year planning of the system has been repeated with the
penetration rates of 10% and 13% penetration of DR in the system. The
results demonstrate that in case of correct placing of DGs in VPP, the
need for developing VPP will be delayed or removed during a specific
planning and the total cost of VPP will be reduced. The cost of VPP will
significantly decrease in simultaneous use of DG and DR in the system.
The more penetration rate of DR in the system, the more power of
owner of VPP for using of DR and as a result cost of VPP will decrease
more.
References
1.66
1.64
1.62
1.6
0
Discussion
10
15
20
Iteration
25
30
35
40
Figure 4: The convergence diagram of BPSO for the three investigated cases.
Citation: Bahrami S, Imari A (2014) Optimal Placement of Distributed Generation Units for Constructing Virtual Power Plant Using Binary Particle
Swarm Optimization Algorithm. J Electr Electron Syst 3: 127. doi:10.4172/2332-0796.1000127
Page 6 of 6
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