Disco operation considering DG units and their Goodness Factor

IEEE PAPER PRESENTATION In the subject ofCMPSA (Computer Methods in Power System

Analysis)Prepared by UTSAV YAGNIK (150430707017)

M.E. Electrical SSEC, BHAVNAGAR

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ABOUT PAPER By:1. Kankar Bhattacharya,Senior Member, IEEE2. Ayed A.S. Algarni, Student Member, IEEE IEEE Transactions on Power Systems,2009

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INDEX

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 42

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ABSTRACT 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).

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ABSTRACT 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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NOMENCLATURE

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NOMENCLATURE

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NOMENCLATURE

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NOMENCLATURE

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NOMENCLATURE

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INTRODUCTION 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.

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INTRODUCTION 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.

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INCREMENTAL LOSS INDICES(ILI)

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:

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INCREMENTAL LOSS INDICES(ILI)

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:

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MUTUAL INDICES 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.

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INDICES RELATION 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.

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GOODNESS FACTOR 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.

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GOODNESS FACTOR The first/second equation denotes impact on

system losses in dollar terms, because of active/reactive power injection by DG at ith bus.

is the market price of the energy. is the payment made by the disco for the reactive

power supply.

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DISCO OPERATIONS CONSIDERING LOSS INDICES

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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DISCO OPERATIONS CONSIDERING LOSS INDICES

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.

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DISCO OPTIMAL ENERGY PROVISIONS CONSIDERING DG GOODNESS FACTORS

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:

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DISCO OPTIMAL ENERGY PROVISIONS CONSIDERING DG GOODNESS FACTORS 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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DISCO OPTIMAL ENERGY PROVISIONS CONSIDERING DG GOODNESS FACTORS 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.

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DISCO OPTIMAL ENERGY PROVISIONS CONSIDERING DG GOODNESS FACTORS 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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DISCO OPTIMAL ENERGY PROVISIONS CONSIDERING DG GOODNESS FACTORS Mathematical formula when DG are owned by

private investors is:

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DISCO OPTIMAL ENERGY PROVISIONS CONSIDERING DG GOODNESS FACTORS 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.

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NETWORK EQUATIONS These are modified to incorporate the purchase by

the disco as follow:

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GRID PURCHASE CONSTRAINTS

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

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BUS VOLTAGE LIMITS 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:

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GENERATION LIMIT ON DG UNITS

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

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FEEDER LIMITS The power handling capacity of a feeder must not

be violated which is given as below:

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CASE STUDY

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CASE STUDY 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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CASE STUDY 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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CASE STUDY

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CASE STUDY 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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COMPARISON: WITH AND WITHOUT GOODNESS FACTOR

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Case 1 = Without Goodness factors and Case 2 = with Goodness Factors

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CASE 1 = WITHOUT GOODNESS FACTORS ANDCASE 2 = WITH GOODNESS FACTORS

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CONCLUSION 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.

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MAIN CONTRIBUTIONS OF THE PAPER

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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THANK YOU