AJAY PRAKASH SINGH
EEE NIT WARANGAL
Under the guidance of
SREE B. Nagu
IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 28, NO. 1
Voltage Stability Based DG Placement in Distribution Networks
H. Ghasemi , S. Vaez Zadeh (senior member ,IEEE)
1. What is DG?
2. Why DG?
3. Earlier used techniques
4. Techniques used in this paper
5. Case study
The small energy-generation units which are connected to
distribution system are referred to as "Distributed Generation”.
The best definition for DG is, "the source of electrical energy is
connected to distribution networks or directly to the consumer
Active Management of distribution network
voltage stability index – most sensitive bus too voltage
collapse in radial distribution system
Problem – an equivalent two bus system is used for the
analysis of voltage stability
bus indices – for considering the effect of aggregated dg in
voltage security of transmission grid are developed
Voltage stability technique –
• Modal analysis
• Continuous power flow
Ranking method – priority list for dg location for compensating
A system is voltage unstable if for at least one bus in the system
bus voltage magnitude decreases as the reactive power injection at
the same bus is increased.
other words, a system is voltage stable if V-Q sensitivity is
positive or every bus and unstable if V-Q sensitivity is negative
for at least one bus.
The linearized steady state system power voltage equations are
∆P = incremental change in bus real power.
∆Q=incremental change in bus reactive power injection.
∆θ = incremental change in bus voltage angle.
∆V= incremental change in bus voltage magnitude.
at each operating point we keep P constant and evaluate
voltage stability by considering the incremental relationship
between Q and V. To reduce the above equations we assume
JR is called the reduced Jacobian matrix of the system. JR is
the matrix which directly relates the bus voltage magnitude and
bus reactive power injection.
The ith mode of the Q-V response is defined by the ith eigenvalue ,
and the corresponding right and left eigenvectors.
Using this in ∆V, we get
By defining v=η∆V vector of modal voltage variation
q= η∆Q vector of modal reactive power variation
We can write uncoupled first order equation as-
Thus for ith mode voltage variation is -
Vi=1/ λi * qi
If λi >0 , the ith modal voltage and the ith modal reactive power
variations move in the same direction, indicating voltage stability of
whereas λi <0 refers to instability of the system.
The relative contribution of the power at bus k in mode
given by the bus participation factor
Pki= ℰ ki* η ki
Participation factors determine the most critical areas
lead the system to instability.
Higher the magnitude bus participation factor
better be the remedial action taken too stabilize the
Determination of max loading is one of the most important problem
in voltage stability analysis that can’t be calculated by model analysis.
This uses successive solution, to compute the voltage profile up too
the collapse point
there jacobian become singular to determine voltage security margin
DG Placement Process
The DG placement problem is solved here by using
modal analysis and the CPF method by an objective
of voltage security margin enhancement and loss
Application of DG placement Algorithm
Application of the placement method and the corresponding indices are
examined on the well-known 33-bus radial distribution network.
The system total apparent load is 4.3694 MVA and DG penetration in all
cases is considered to be 40% (i.e., 1.7477 MVA).
Uses (QLI) – to determine priority list of dg to compensate reactive
It will not seek VSM
The proposed placement algorithm is implementable in different DG
Due to the radial nature of distribution networks, the buses of each
network branch, from the tail to the main feeder, usually have
participation factors in a descending order for a specific mode.
the 33-bus radial networks participation factors for mode 1 in descending
order when DG at bus 18
Application of the ranking method is examined on all candidate buses
obtained from the placement algorithm, bus 28 is the best site for reactive
power compensation in the case of shortage.
The places are ranked using an MERC method, which
determines a priority list of DG locations for reactive
power compensation during occasions of reactive power
The placement algorithm is executed and remedial
effect of DGs, both in loss reduction and voltage profile
improvement in normal operation, and enhancement of
the loading parameter in the case of voltage instability
The ranking method is executed over the obtained
candidates to provide a priority list from the view point of
reactive power compensation in the case of shortage.
DG placement is different from the best location for reactive
power compensation and VSM in the presence of a voltage-
Long-term DG placement problem can be solved by CPF and
modal analysis while the short-term reactive power issues can be
addressed by the ranking method
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distributed generation: Is the current regulation of electricity
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M. E. Baran and F. F. Wu, “Network recon figuration in distribution
systems for loss reduction and load balancing,” IEEE Trans. Power
H. A. Gil, M. E. Chehaly, G. Joos, and C. A. Caizares, “Bus-based
indices for assessing the contribution of DG to the voltage security
margin of the transmission grid,” presented at the IEEE Power Energy