Voltage Stability-Based DG Placementin Distribution Networks

1. M. Ettehadi , H. Ghasemi , S. Vaez-Zadeh
Electr. & Comput. Eng., Univ. of Tehran, IEEE Power & Energy society 2013
Student ; Reza Shahbazi
2014 December
Voltage Stability-Based DG Placement
in Distribution Networks
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2. Power system stability
Rotor angle stability
Transient
stability
Small
Disturbance
Frequency stability
Short term Long term
Voltage stability
Small
Disturbance
Large
Disturbance
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View on Stability :

3. I. Introduction
 DG
II. Voltage-stability Problem In Distribution Networks
 Problem Identification
 Modal Analysis
 CPF : Continuous Power-Flow Methodology
III. DG Placement Algorithm
 DG Placement Process
 DG Placement Evaluation Indices
IV. Short-term Reactive Power Ranking
 Qualified Load Index (QLI)
 Ranking Process
V. Case Study
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4.  Introduction :
DG
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5. DG (Distributed Generation)
 Distributed generation (DG) is any electricity generating technology installed by
a customer.
 Generating power on-site (close to the load), rather than centrally, eliminates the
cost, complexity, interdependencies, and inefficiencies associated with
transmission and distribution.
 Since reactive power cannot travel over long distances, system
operators/dispatchers should provide it locally.
DG units are good local reactive power sources.
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6.  Voltage-stability Problem In Distribution Networks
 Problem Identification
 Modal Analysis
 CPF : Continuous Power-Flow Methodology
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7. Problem Identification
‫ولتاژ‬‫پاشی‬‫و‬‫فر‬:
‫گر‬‫بدل‬ ‫کلی‬‫ولتاژ‬ ‫پاشی‬‫و‬‫فر‬‫ت‬‫ر‬‫بصو‬ ‫میتواند‬‫که‬ ،‫است‬ ‫ای‬‫ناحیه‬‫پدیده‬‫یک‬‫خود‬ ‫طبیعت‬‫در‬‫ولتاژ‬ ‫ی‬‫ناپایدار‬‫این‬‫ر‬‫بناب‬‫پاسخ‬‫هیچ‬‫بدون‬‫دد‬
‫سریعی‬.
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‫ایش‬‫ز‬‫اف‬‫بار‬(‫بار‬ ‫تقاضای‬‫ایش‬‫ز‬‫اف‬)‫ناحی‬ ‫در‬‫ولتاژ‬ ‫شدن‬ ‫کنترل‬‫غیرقابل‬‫ه‬
‫قدرت‬‫سیستم‬‫از‬‫مشخصی‬‫ولتاژ‬ ‫ی‬‫ناپایدار‬

8.  Voltage stability (IEEE ):
refers to the ability of a power system to maintain steady voltages at all
buses in the system after being subjected to a disturbance from a given
initial operating condition
 Voltage collapse :
usually occurs in heavily loaded systems that do not have sufficient local
reactive power sources.
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This reactive power shortage may
lead to wide-area Blackouts

9. Tools for voltage stability analysis
Different methods exist in the literature for carrying out a steady state
voltage stability analysis:
 P-V curve method.
 V-Q curve method and reactive power reserve.
 Methods based on singularity of power flow Jacobian matrix at the
point of voltage collapse.
 Continuation power flow method.
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10. Modal analysis :
‫ی‬‫پایدار‬ ‫د‬‫ر‬‫مو‬‫در‬ ‫بینی‬‫پیش‬‫و‬ ‫سی‬‫ر‬‫بر‬‫ای‬‫ر‬‫ب‬ ‫ریاضی‬‫شهای‬‫و‬‫ر‬‫از‬ ‫یکی‬/‫ولتاژ‬ ‫ی‬‫ناپایدار‬.
 A modal analysis can discover the instability characteristics and can be
used to find the best sites for reactive power compensation
 For a (n*n) square matrix A, left and right eigenvectors are defined as
follows:
A.x = λx
y.A = λy
λ = eigenvalue of the matrix A
x (n*1) = right eigenvector
y (1*n) = left eigenvector
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11. The characteristic equation of both equations
det (A-λ*I) = 0
The solution of this equation: [ λ1 , λ2,…. , λn] are the eigenvalues of A
if λi > 0 The system is voltage stable
if λi < 0 The system is voltage unstable
if λi > 0, then the variation of Vi and Qi are in the same direction.
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12. Continuous Power-Flow ( CPF ( Methodology
 VSM : Voltage Security Margin
The higher the VSM ,the more secure the system
Near the voltage collapse point It is difficult to obtain a power flow solution
Continuation power flow is a technique by which the power flow solutions
can be obtained near or at the voltage collapse point
According to the proposed algorithm, a CPF is executed on the system
under study
In this step we use CPF to identify the most sensitive bus to voltage collapse.
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13.  DG Placement Algorithm
 DG Placement Process
 DG Placement Evaluation Indices
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14. DG Placement Process
The DG placement problem can be formulated by many objective
Functions including
 Loss Minimization
 Voltage Profile Improvement
 Economical Revenue
 Environmental Impact Reduction
 Improvement On Reliability Aspects
 Voltage security margin enhancement and loss reduction
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15. the modal analysis is used concurrently to determine
the critical modes and their associated buses.
The CPF can be used for the determination of
the VSM and the bus voltages at collapse points.
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 bus with a minimum voltage at the collapse point is defined as the most
sensitive bus to voltage collapse.
 This bus is selected as a candidate for DG placement.

16. 16start
Receive the network data
Execute the CPF and determine the most sensitive bus to voltage collapse as a candidate
Execute the modal analysis and determinate the worst modes
Determine the most participating bus in each mode as a candidate
Add a DG to the candidate bus
Execute CPF and calculate the maximum loading
Is it the last candidate?
Next candidate
Select the candidate bus with the highest loading
Do we want to place another DG ?
Print the result
Locate a DG at the
bus which has the
maximum loading
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17. DG Placement Evaluation Indices
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The higher the VSM, the more secure the system.
ALR and RLR show active and reactive loss
reduction after installing DG/DGs.
Higher values of and indicate better performance
of ALR and RLR DGs in loss reduction.
The lower the VI, the better the performance of
DG units.

18. • Application of the Placement Algorithm
CASE STUDY
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Application of the placement method and the corresponding
indices are examined on the well-known 33-bus radial distribution
Network.
Single-line diagram of the 33-bus radial distribution network
The system total apparent load
is 4.3694 MVA and DG
penetration is considered to be
40% (i.e., 1.7477 MVA).

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23. I. Voltage Stability-Based DG Placement in Distribution Networks
M. Ettehadi , H. Ghasemi , S. Vaez-Zadeh : Electr. & Comput. Eng., Univ. of Tehran, IEEE Power & Energy
society 2013
II. Voltage Stability Evaluation of The Khuzestan Power System in Iran Using CPF
Method and Modal Analysis(2010)
Farbod Larki-Ahvaz, Iran ; Mahmood Joorabian-Ahvaz, Iran ; Homayoun Meshgin Kelk, Mojtaba Pishvaei-
Tafresh, Iran
III. Notes on Power System Voltage Stability By S. Chakrabarti, Dept. of EE, IIT,
Kanpur
Refrences
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24. I Really Appreciate Your Concern.
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