Enhancement of Available Transfer Capacity

for Congestion Management

In Deregulated Power System

Guided by : Prof. S. K. Joshi

M.S.U. Baroda

Presented by B.P.Pandya , BE(E) IV

Roll No. : 424

Project Theme

• Deregulated Electricity Market – Open Access• Congestion Management• Available Transfer Capacity

• To propose a new set of AC sensitivity referred as “ AC Power Transfer Congestion Distribution Factor (ACPTCDF) “ for 6 bus system.• Calculate ATC of transmission line

• Enhancement of ATC using facts devices for congestion management

Significance of Topic

• Conversion of Vertically integrated utilities to Open Access market system

[ May 2003,Indian Electricity Act]• To promote competition through open access among

utilities ATC must be calculated [ ATC posted on OASIS]• Because of Open Access, Congestion is prime problem for

power system• Congestion can be managed by Facts devices. Fact

devices can enhance ATC.• So we develop a set of congestion distribution factors in

terms of real as well as reactive power• Most sensitive congested line is identified by sensitive

analysis and ATC calculation

Regulation

Deregulation

Advantages of Deregulation

• The need for regulation changed – former vertically integrated utility is disaggregated into separate companies devoted to each function.

• Privatization• Cost is expected to drop• Customer focus will improve• Encourages innovation• Power production and retail sales will be

competitive, monopoly franchise business

Benefits & Issues involved in Deregulation

Benefits Issues

Improved generation Network Congestion

Planning Efficiency Optimal bidding for Genco

Cheaper electricity due to competition and innovation

Transmission pricing

Improved Economy Ancillary Services Management

New jobs for power engineers

Risk Analysis

Network Congestion

• When the producers and consumers of the electric energy desire to produce and consume in total that would cause the transmission system to operate at or beyond one or more transfer limit, the system is said to be congested.

• Congestion is a consequence of network constraints characterizing a finite network capacity that prevent the simultaneous delivery of power from an associated set of power transactions.

Constraints

• Thermal limit :- The maximum amount of electrical energy that transmit on transmission line without

overheating.

• Voltage limit :- System voltage and change in voltage must

be maintained with the range of acceptable

deviation• Stability limit :- Transmission system capable of

surviving disturbances through the transient and dynamic period

Graph showing congestion

Objective of Congestion Management

• Minimized interference of the transmission network in the market for electric energy

• Secure operation of the power system • Improvement of market efficiency• Manage power flow with existing Transmission

line

Available Transfer Capacity (ATC)

“ATC is a measure of the Transfer Capability Remaining in the transmission network for further commercial activity* over and above already committed uses”

(* while ensuring system security)Mathematically,

ATC = TTC – TRM – (ETC+CBM)

[In accordance with the recent FERC (Federal Energy Regulatory Commission) Order 888 (Promoting Utility Competition Through Open Access, Non discriminatory Transmission service by Public Utility)& 889(OASIS , Open Access Same time Information system) ,

ATC must be calculated for electric utility].

ATC = TTC – TRM – (ETC+CBM)

ETC is the existing transfer commitmentsTTC is the maximum amount of power which can be

transferred over the network while satisfying all security constraints.

TRM is the margin required for uncertainties in the system conditions.

CBM is the margin reserved by load serving entities for generation reliability requirements.

Pre- Contingency Situation

Bart. SE

Nrth Barth.

N.E.S.

Delaware

Flow 900

Flow 50

Rating 210

ContingencyElement

CONTINGENCY

Flow gate direction

Post contingency situation

N.E.S.

Delaware

Flow 0

Flow 212

Rating 210

contingency

50 + 0.18 * 900

Flow gate direction

Bart SE

Nrth Bart

• Transfer Capacity… on 28/1/2010

• Present Status: Transfer Capacity state

1.

Congestion charges applicable NO

2.

Total transfer capacity(TTC) of NR

4250 MW

3.

Available transfer capacity(ATC) of NR

3750 MW

4.

IR Schedule 2749 MW

5.

IR Actual 2930 MW

6.

TTC Violation -1320 MW

7.

ATC Violation -820 MW

NORMALNORMAL

Transfer capacity state1)Normal- No Violation- color Green2)Alert- ATC Violation- color Yellow3)Emergency- TTC Violation- color Red

Role of ISO

• ATC is a measure of how much additional electric power could be transferred.

• Each ISO is responsible for monitoring its own regional transmission system and calculating ATC for potentially congested paths.

• ATC values would be placed on a website known as ‘Open Access Same-time Information System (OASIS) operated by ISO.

• Anyone wishing to do transaction, would access OASIS web pages and use ATC information available there to determine if system could accommodate the transaction.

AC Load flow based Approach

•A.C. based approach utilized two sets of sensitivity factors terms as Real Power Transmission Congestion Factor (PTCDF) & Reactive Power Transmission Congestion Factor (QTCDF)

•Most sensitive transmission line can be found & manage this line with use of FACTS device.

Real Power Transfer Congestion Distribution Factor ( PTCDF)

• For ATC determination the MW flow must be allocated to each line or group of lines in proportion to MW being transmitted by each transaction.

• A transaction is a specific amount of power that is injected in to the system at one bus by a generator & removed at the another bus by load.

• PTCDF is defined as the change in real power flow (ΔPij) in a transmission line –k, connected between bus i & j, due to unit change in the power injection(ΔPn) at bus-n.

• QTCDF is defined as the change in reactive power flow (ΔQij) in a transmission line –k, connected between bus i & j, due to unit change in the reactive power injection(ΔQn) at bus-n

• It is also called sensitivity because it relates the amount of one change – transaction amount – to another change – line flow.

1 52 3 4 7766

ATC Calculation using PTCDF• Recognizing new flow on line from bus i to bus j

(line k) due to transaction at bus n.

Line Outage Distribution Factor (LODF)

• ATC is also limited by the effects of contingencies.

• The line flows could be used to calculate the effect of each line outage, then PTCDF applied to find transfer limit.

• LODF’s & PTCDF’s can be combined to calculate the first contingency incremental transfer capability, which is the maximum increase in transaction amount from one bus to another bus.

• LODF can be defined as the measure of redistribution because of line outage.

1 2 3 4 5 6

ATC using PTCDF & LODF

Congestion Management by FACTS devices

• For efficient utilization of the existing network with penetration of additional power FACTS devices are used.

• Effective FACTS based power flow control can be applied to relieve transmission congestion & Improve the transfer capability of the network with high penetration of power. While voltage security & voltage stability constraint are satisfied & transmission net work can be effectively utilized.

Principle of Control• The inserted series voltage can be regulated to

change the impedance (X) of Transmission line hence power flow of the line can be controlled.

• FACTS is power Electronics based system that provide dynamic control of the power transfer parameters transmission voltage, line impedance & phase angle, active and reactive power when storage becomes viable storage then they can supply & absorbed active power as well

• Consider unity power factor load, real power transferred is given by

• Similarly Reactive power transferred is given by

FACTS Technology and their potential

• Definition[3] of FACTS by IEEE as: “ Alternating current transmission system

incorporating power Electronics based & other static controller to enhance controllability and increase power transfer capability”

• FACTS controller [14] :- “It is power electronic-based system and other static equipment that provide control of one or more AC transmission parameters.

• For ATC enhancement the FACTS devices are placed at weak-bus.

FACTS Devices

1. Shunt controller : Adjusting the system voltage by means of

shunt reactive elements is known as shunt compensation.

2. Series Controller : Adjusting the system voltage by means of series reactive elements is known as shunt compensation.

3. Combined shunt-series controller (Unified Power Flow Controller) :- – It provides independent series reactive

compensation for each line bus also transfer real power among the line via d.c. power link (Inter line power flow controller).

– Used in multiple line

Conclusion & Future Scope

• It conclude that ATC calculation is very important & mandatory for Open Access in power system in Deregulated Electrical Market .

• In future with the help of some optimization techniques like genetic algorithm, Particle Swam Optimization, we can optimized reactive power injection at weak bus.

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Reference Websites

• www.powerexindia.com• www.iexindia.com• www.pserc.cornell.edu/tcc• www.powergridindia.com• www.nldc.in• www.erldc.org• www.wrldc.com• www.spp.org• Atc_jan2010_powergrid