1. Disco operation considering DG
units and their Goodness Factor
IEEE PAPER PRESENTATION In the subject of
CMPSA (Computer Methods in Power System
Analysis)
Prepared by UTSAV YAGNIK (150430707017)
M.E. Electrical
SSEC, BHAVNAGAR

2.  By:
1. Kankar Bhattacharya,Senior Member, IEEE
2. Ayed A.S. Algarni, Student Member, IEEE
 IEEE Transactions on Power Systems,2009
2

3. Sr.
No.
Topic Slide
No.
1 Abstract 4
2 Nomenclature 6
3 Introduction 17
4 Incremental Loss Indices(ILI) 13
5 Mutual Indices 15
6 Indices Relation 16
7 Goodness Factor 17
8 Disco Operation Considering Loss Indices 19
9 Disco Optimal Energy Provisions Considering Goodness Factor 21
10 Network Equations 27
11 Constraints 28
12 Case Study 32
13 Conclusion 41
14 Main Contributions of the Paper 423

4.  The proposed Goodness Factor of DG units is
based on the computation of incremental
contribution of a DG unit to distribution system
losses.
 The incremental contributions of DG unit to active
and reactive losses in the distribution system are
termed as the active/reactive Incremental loss
Indices(ILI).
4

5.  The Goodness factors are integrated directly into
the Distribution systems operational model, which
is based on Optimal Power Flow (OPF)
framework.
 This model seeks to minimize the distribution
losses of the DISCO taking into account the
contribution(Goodness factor) of each DG unit.
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6. 6

7. 7

8. 8

9. 9

10. 10

11.  Due to the presence of DG sets in the distribution
system, instead of conventional unidirectional
power flow it is possible to have power flow in
many arbitrary directions.
 In this paper, first, a novel set of sensitivity indices
that quantifies the contribution of DG source at a
specific bus is developed.
 The goodness factor provide the operator “worth”
of a DG set’s active and reactive injection to the
distribution network in actual dollar terms.
11

12.  The found Goodness factors can help discos to
operated economically and payoffs to the
particular DG owner can also be made based on
the Goodness factor.
 These sensitivity indices and Goodness factors can
help disco owner to make decisions regarding DG
sitting problem and distribution related issues of
planning, although those issues have not been
discussed in this paper.
12

13.  1. Self Indices:
 Denotes the incremental change in the system
active/reactive power loss due to an incremental
active /reactive power injection at a bus:
13

14.  The ILIs are obtained from the Lagrange
multipliers of an active/reactive power loss
minimizing optimal power flow (OPF) model.
 The corresponding active and reactive power loss
functions are as below:
14

15.  The active/reactive power mutual ILI denotes the
incremental change in the system active/reactive
power loss due to an incremental reactive/active
power injection at another bus.
15

16.  In any distribution system, the change of flows in
one line would affect flows in other lines due to
interconnection.
 But in a networked configuration, the DG
injections will result in arbitrarily counter-flows in
the distribution system, and hence, the ILIs will
NOT be co-related.
16

17.  A money value is attached to the ILIs to arrive at
Goodness factor for a DG set at a given bus.
 the Goodness factor indicate the relative
importance and contribution of one unit of DG in
comparison with other unit.
17

18.  The first/second equation denotes impact on
system losses in dollar terms, because of
active/reactive power injection by DG at ith bus.
 𝜌 𝑃
is the market price of the energy.
 𝜌 𝑄 is the payment made by the disco for the
reactive power supply.
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19.  The short term model of a disco in the presence of
DG resources is appropriately modified to include
the goodness factors of DG units.
 The term “short term model” refers to the dispatch
stage typically starting from 1 hour to as close as 5
minutes before dispatching the energy.
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20.  This is because, in this time frame, a full scale
OPF is usually carried out and disco’s loss
representation is exact and due to which the
goodness factors are true indicators of a DG set’s
worth to system loss reduction rather than a time
frame of day ahead planning.
20

21.  The objective is to minimize the cost of energy in
an given hour under consideration.
 Mathematical formulation of a disco owning all
DG resources is:
21

22.  First component is the cost of power purchased
from external grid or energy market and depends
on electricity market price.
 Second component is payment for the reactive
power from the external grid, transferred over
substation transformers at a predetermined price.
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23.  The last two terms represent the benefit or cost
savings accrued by the disco because of increase in
active/reactive power generation by DG units
compared to that in the dispatch without goodness
factors.
23

24.  The disco’s objective will slightly modify when
DG sets are owned by private investors instead of
utility itself.
 Such units won’t be included in the disco’s
dispatch program, but their generation has to be
absorbed by the disco according to prior
arrangements, while making adjustments in its
own resources.
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25.  Mathematical formula when DG are owned by
private investors is:
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26.  In the last equation the third term is the price paid
by the disco to the private owner for energy
purchase.
 But as it will be already discussed before
purchasing, that term can be treated as a constant
when planning is done one hour prior to the
dispatch.
26

27.  These are modified to incorporate the purchase by
the disco as follow:
27

28.  To ensure that the purchase is within transformer
capability and given by:
28

29.  This ensures that the bus voltages are held at a
certain value and the do not violate a certain limit
of dropping and shooting voltages:
29

30.  To ensure that power generated from a given DG
set is within its limits
30

31.  The power handling capacity of a feeder must not
be violated which is given as below:
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32. 32

33.  The last bus system has been extracted from the
IEEE 30 bus system in which only 33kV network
has been considered.
 Bus 1,11 and 16 are connected with the external
market.
 DG units are located at the buses 4,7,8,12,13,15,17
and 18.
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34. 34

35.  In the table from earlier slide, it can be observed
that ILIs for transformer buses i.e. 1,11,16 are
zero, as they can locally supply and extra MVAR
or MW as they are not fully loaded.
 Also, minus sign in the table indicates direction of
power loss which is reducing.
 The minus sign should not be considered while
calculation of Goodness factor is going on since
these sign is associated with the Langrage
multipliers only.
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36. 36

37.  Based on the goodness factor, the buses
4,7,8,12,13,15,17 and 18 DG sets are selected.
 These buses can also be selected by proper OPF
planning but since the main aim of this paper is to
explain method, directly buses with highest
goodness factors are selected.
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38. 38

39. 39

40. 40

41.  This paper introduces a set of indices that assist
discos in decision making process.
 These indices utilize distribution power flow
framework and sensitivity of the system losses to
an incremental change in an active and/or reactive
power flow injection at a given node.
 In order to integrate the effects of these indices in
an optimum energy provisions framework, the
goodness factor has been introduced.
41

42.  Development of a novel concept of the bus
goodness factor to serve as an indicator of the
contribution of DG power injection at a bus, to the
system losses in dollar terms.
 Modification of “short term operations model” to
incorporate the goodness factors in its decision
making framework.
 Examination of the benefits occurred due to
inclusion of the goodness factors..
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43. THANK YOU
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