ATC for congestion management in deregulated power system

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

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

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 commitments TTC 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 Contingency Element CONTINGENCY Flow gate direction

Post contingency situation 50 + 0.18 * 900 Flow gate direction Bart SE Nrth Bart N.E.S. Delaware Flow 0 Flow 212 Rating 210 contingency

Transfer Capacity… on 28/1/2010 • Present Status: Transfer Capacity state NORMAL Transfer capacity state Normal- No Violation- color Green Alert- ATC Violation- color Yellow Emergency- TTC Violation- color Red 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

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 ( Δ Pij) in a transmission line –k, connected between bus i & j, due to unit change in the power injection( Δ Pn) at bus-n.

QTCDF is defined as the change in reactive power flow ( Δ Qij) in a transmission line –k, connected between bus i & j, due to unit change in the reactive power injection( Δ Qn) at bus-n It is also called sensitivity because it relates the amount of one change – transaction amount – to another change – line flow. 1 5 2 3 4 7 6

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

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. power ex india .com www.iex india .com www. pserc .cornell.edu/tcc www. powergrid india.com www.nldc.in www.erldc.org www.wrldc.com www.spp.org Atc_jan2010_powergrid

ATC for congestion management in deregulated power system

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ATC for congestion management in deregulated power system