Study of Technical Data of Present HVDC Links in INDIA and Techniques Used For System Stability in HVDC Transmission Line

Transcription

1 Study of Technical Data of Present HVDC Links in INDIA and Techniques Used For System Stability in HVDC Transmission Line Savita Devi 1, Dr.Naresh kumar 2 1 M.tech Scholar,DCRUST 2 A.P., Electrical Deptt, DCRUST Murthal Abstract: Trend of HVDC in power system is increasing day by day due to its technical advantage over AC like long distance bulk power transmission, cost factor, indendent control over active and reactive power etc. For the system stability many researchers have used VSC for control of active and reactive power by tuning the PI controller through hit and trail method. In this paper various technical data of HVDC transmission line are present and some of few techniques for the system stability. Keywords: HVDC links, Bipolar Transmission, Back to-back transmission. I. INTRODUCTION HVDC Technology which is used for long distance bulk power transmission, asynchronous interconnection of two different systems to solve AC transmission problems. In HVDC through the controlled action of power electronics devices, AC power is converted in to DC power for transmission. For submarine cable and overhead transmission HVDC is used.hvdc is more preferred as compared to HVAC due to cost factor, synchronization method, corona losses and radio intrfrence are less in HVDC. One of the most important application of HVDC transmission is integrating offshore wind farms to onshore grid via DC cables. There are two technology in HVDC transmission line : the LCC-HVDC and VSC-HVDC transmission. The line commutated converter known as classical HVDC. It is widely used in DC line. In this thyristtor based converters are used. The switching frequency used are of 60 or 50 Hz. The problems of harmonics are reduced by the use of low pass filter and large filter are required to eliminate the the generated harmoincs. There are two type of converter classic which described above and conventional HVDC. Conventional HVDC are used to consume the reactive power. This occurs due to the lagging current which is generated by delayed firing of the converter switches. This reactive power is supplied to the AC network. Static Var compensator (SVC) at the end of the terminal. II. TYPES OF HVDC SCHEME There are three type of HVDC scheme. The requirement of schemes depends upon operational requirements, felexibility of demand, reliability isues and cost. HVDC scheme are described below [3] Mono Polar : In this configuration scheme a single line is used to connect the converters either positive terminal or negative terminal.the ground or metal can be used a return All Rights Reserved 191

2 2.Bi-polar: In this transmission of power take place through two conductors of opposite polarity.it is a combination of two monopolar link system used. Due to this doubling reliability of the system increasesd. 3.HOMO-POLAR : In this two converters are connected to each other without any DC line. Back-toback scheme is applied when two transmission system of different frequeny. 4 Back to Back system Back to back HVDC can be used for connecting the asynchronous grids. There is no need of transmission line because it is placed at same site. III. COMPONENTS OF HVDC SYSTEM CONVERTER UNIT: This usually consist of two or three phase converter bridges connected in series to form a 12 pulse converter unit. The total number of valves are 12. Converter transformer : Transformer I used to step up and step down the voltage level. There is special requirement for design and construction of transformer used in this. High stress: As compared to power transformers, the generator transformer are subjected to higher stress due to following reasons : Presence of DC voltage in addition of AC voltage, high voltage stress are there, higher magnetizing current due to dc voltage, higher harmonic content and higher abnormal over voltage. Special desigen requirements: a) Special desigen of bushing b) Special design of winding and insulating All Rights Reserved 192

3 IV. OTHER TWO COMPONENTS ARE: THYRISTER VALVE : The thyristor valves can be constructed in many ways depending on the application. The most common way of arranging the thyristor value is 12 pulse group with three quardrature valves. Each thyristor is valve is consist of a some series connected thyristor with their auxillary circuit. VSC Valves : It consist of two level or multilevel converter, phase-reactors and AC filters. In this like thyrister valves each converter bridge is connected with number of series connected IGBTs with their auxillary circuit [energy]. 4TECHNICAL DATA OF HVDC PROJECTS IMPLEMENTED IN INDIA 4.1.BIPOLAR PROJECTS: I)Chandrapur-padge HVDC bipolar project Commissioning year 1991 No. of poles 2 Length of overhead dc line Rated power AC system voltage DC voltage,nominal Over load capacity Maximum current 752 km 1,500MW 500 kv 1,650 MW for 2 hours,2,200 MW for 5 sec 1700 A No. of banks in chandarpur NO. of banks in Padghe Thyristor valve Valve Type Cooling system 4*200 MVAR 4*200MVAR quadruple All Rights Reserved 193

4 Thyristor size 45 cm2 Number of thyristors per value 96 No. of dc banks per station 2 Maximum voltage per thyrister 7 KV Converter transformer Type Single-phase,3-winding Rated power 300 MVA each AC grid at both ends synchronous Ambient temperature 33c Main reason for choosing HVDC Long distance,stability frequency and damping control Manual or automatic Power company Maharashtra state electricity board Bombay Supplier ABB/BHEL 4.2 Rihand-Delhi HVDC bipolar project: The Rihand-delhi HVDC transmission is first commercial long-distance HVDC link in INDIA configuration Single bipole circuit Power rating Mono-polar -750 MW at 1991 Bipolar MW at 1992 No. of converters per station 2 transmission overhead Main reason for choosing HVDC Long distance,stability Operating voltage for ac yard 400 KV Operating voltage for dc yard 500KV No. of converter transformer 6 each of 300 MVA,3 winding single phase. No. of quadruple valves 6 Minimum clearance phase to phsae on 5.75m 400 KV AC side Minimum clearance phase to ground on kv AC side Minimum clearance phase to phase on 12m 500 KV DC cables Minimum clearance phase to phase on 7 m 500 KV DC side Size of busbars in DC yard 10 Size of busbar in AC yard 4 Transmission line voltage 7kv Transmission line length 820 KM Power rating 1500 MW Total Mvar of ac filter in 2 station 200 Mvar Direct current 1568 All Rights Reserved 194

5 AC grid at both ends control Power company and main supplier capacitor synchronous Constant power,damping control Manual or automatic National thermal power cooperational india ltd.,bhel 4.3) Talcher-kolar HVDC bi-polar project: This is the largest power transmission project in INDIA Linking the Indian states of Karnataka and Orissa over a distance of some 1450 km with the rectifier( ac to dc) and inverter( DC to AC) stations very distant from each other. Total value 200 million euro Transmission length 1,450 km Commercial operation February 2003 Rated power 200 MW,bipolar(2003),2500 MW (2007) DC transmission voltage 500 KV Rated current 400 A Maximum allowable over load 1.15 Pu for 120 min.,1.3pu for 30 min. and 1.47 Pu for 5 sec. AC system voltage Eastern terminal(orissa),50 Hz Southren terminal (Banglore) 400 Kv,50 Hz Smoothing reacter 250mH dry air core type/pole DC filter,per station and pole 1 double-tuned filter 12/24,12/36 Ground electrode Dry type ground electrode AC filters/reactive power compensation elements Eastern terminal (talcher) 6 no. double-tunned (ac) filter 12/24,120Var,each and 3no(DT) AC filter 3/36,97Mvar each 1 no shunt capacitors,66 Mvar,2 no shunt reactor,80 Mvar,each 106 no Double tunned ac filter 12/24,120 Mvar Southern terminal (kolkar) Each 3no DT ac filter 3/36,97 Mvar each. 5no. shunt capacitor 138 Mvar each Power thyristor Converter values 3.888no (ETT) Converter transformers 7no. single phase 3 winding rated at 397 MVA ( inc. 1 spare All Rights Reserved 195

6 4.4 Lower sileru-barsoor HVDC Bipolar project : parameter Stage-1 Stage-2 Stage-3 voltage +100kv DC monopolar 6- pulse +200kv DC Monopole 12-phase +200Kv DC Bipole 12- pulse current 1000 A 1000 A 1000 A Transmitted power 1000MW 100 MW 100 MW AC side voltage 220 Kv 220 Kv 220 kv Line segment 196 km 196 km 196 km Valve type double Quadric 2 Quadric Valve cooling water.. Valve insulation air.. Converter transformer Smoothing reactor 40.5 Mvar,10 kv.. Single phase.45henry,200kv 1000A DC 4.5 Biswanath Agra HVDC Bipolar project:.45henery,200 kv,1000a DC Commissioning year 2015 Project type Multi terminal (UHVDC) No. of poles 2 No. of converter 4 Power transmitted,mw 6000 MW DC voltage,kv 800 kv Ac voltage length 1728 km capacitor Connecting region Northeastern and eastern region of india Automatic power reduction triggered by ac signal Main reason for chossing hvdc system Long distance, bulk power Power company and supplier ABB has been selected by powergrid corporation of India ltd. 4.6 Balai bhiwadi HVDC bipolar project : Commissioning year Pole1: march 2010 Pole2:march 2011 No. of poles 2 Dc voltage,kv 500kv Power transmitted,mw 2500MW Ac voltage length 780 km capacitors Connecting region North western-region and eastern region All Rights Reserved 196

7 Main reason for choosing HVDC India Automatic power reduction triggered by ac signal Long distance, bulk power 4.7 Mundra mohindergarh HVDC Commissioning year 2012 No. of poles 2 (bipole) Power transmitted, MW 1500 MW DC voltage,kv 500Kv Ac voltage length 986 km capacitors Connecting region Western-region and northen region of india Automatic power reduction triggered by ac signal Main reason for choosing HVDC sytem Long distance, bulk power 2. Back to back interconnected projects: 2.1) vizag HVDC project : Commissioning year 2005 Rated power 500 Mw (1999) vizag-1,500 Mw(2005) vizag-2 Over load capacity 550 Mw for 2 hours, 666 Mw for 5 sec Dc voltage 205 kv vizag-1,88kv vizag-2 Type of link Back to back Ac system voltage Smoothing reactor 2 no air insulated 20 MH each Station occupies an area 450*150m Ac filter No. of banks,east side 3*110 Mvar, Hp12/24(each) No. of banks, south side 3*110 Mvar,hp 12/24 (each) Shunt reactor each side 80 Mvar Max. increase of firing angle 63 degree Thyrister valve Valve type Quadruple 1 valve consists of six thyristor modules with 6 thyristor/module Cooling system De-mineralized water Thyrister size 5 inches No. of thyristor per single valve 36 Total no of thyristor 864 Max voltage per transformer 7.2 kv Converter transformer type Single phase,3 winding (6 units) Rated power 201 MVA Main reason for choosing HVDC Asynchronous All Rights Reserved 197

8 no. of pole 1 Converter per station 2*2 Direct current 2860 A Asynchronous Ac grid at both the end Powercontrol,frequency control, voltage control 2.2 Vindhyachal HVDC project : Commissioning year 1989 No. of poles 2 Power transmitted, MW 2*250 Dc voltage,kv 2*69.7 Direct current,amp capacitors Converter station location and ac grid voltage 400 kv,western system AC grid at both ends asynchronous control Constant power in either direction and damping control Automatic power reduction trigerred by ac signal Main reason Asynchronous link 2.3 Sasaram HVDC project : Year of commissioning 2002 Power rating 500 MW Dc voltage 205 kv Line/cable Back to back Power company Power grid corporation India Ltd Ac grids at both end asynchronous Rated current 2,475 A Valve configuration 50 thyrister from a valve and 4 valves staked vertically from a quadric-valve Diameter of a thyristor 100mm Reason for chossing HVDC Asynchronous link control Constant power in either direction Length of cable Back to back Technique used for system stability There are various FACTS devices are used to enhance transient and dynamic stability. STATCOM is used for the injection of active power. AC-dc line are superimposed which reduces the transmission losses. With the emerging use of voltage source converter HVDC links, the hybrid commutated converter (LCC) HVDC and the VSC-HVDC link is become a useful structure in power system. Other technology is feed-back loop is used. By this method different instability can be removed out. Modelling and simulation of mono-polar HVDC link by the PI controller using fire fly algorithm technique. In this the result of optimized technique and un-optimized technique are compared. We get better result of by optimized technique in lesser number of iteration counts. Power quality can be improved by using UPFC. UPFC is a FACT device which is used to control active and reactive power in transmission All Rights Reserved 198

9 In this we deal with the different types of fault at different fault location placing UPFC permanent at receiving end of the line so that the magnitude of fault current and variations of excitation voltage reduced and finally voltage magnitude is improved by UPFC.At the end fast fourier transformation analysis is carried out to determine total harmonic distortion with and without UPFC for different fault. V. FUTURE SCOPE Here we gave complete data about present HVDC links in INDIA which can be taken for further research work. Multi-terminal HVDC was 1 st introduced with 800kv,3000 MW upgrade to 6000 MW [1]. The proposed site for rectifier station is in Biswanath Chariali and Alipurduar handling 3000 MW and inverter station at Agra handling 6000 MW power. This system is proposed to originate from Assam and pass through west Bengal, Bihar and terminate in Uttar Pradesh with an approximate length of 1728 km. It will be the highest capacity HVDC project of the world considering the continuous 33% overload features. The earth electrode shall be desigened for 5000 Amphere DC continous current which shall be of first of its kind in the world. Thia project is expected to commission by It also include the extension of the Mundra-Mohindergarh HVDC link currently operating at 1500 MW to its full installed capacity of 2500 MW.Further project are in progress and from the stability technique VSC(voltage source converter) are better used in now a days. By modeling and simulation of vsc in matlab with various optimization technique will give less losses in every aspects VI. REFERENCE 1. REPORT On Operation and Maintenance Of HVDC Stations, Praveen Ranjan, PGCIL, HVDC Transmission Overview, M. P. Bahrman, P.E., Member, IEEE, [3] System Benefits derived from the 500MW Back to Back HVDC scheme at sasaram, India, R N Nayak, D Kumar, B N Kayibalu, R Gulati, M.H Baker,CIGRE, Operation experiences of the Chandrapur-Padge HVDC Bipolar Project M.Ahafz,R.S.Parulkar,P.B Chimaram s,npsc IIT Bombay, Basic design Aspects of Ballai Bhiwadi 2500 MW HVDC power Transmission system, R.K Chahan, M.Kuhn, D. Kumar, A.Kolz, p.riedal, Operation experience of the system projection scheme of the Talcher-kolar HVDC link, V.K Agrwal, P.R Raghu, C.S Tomar,Oomen chandy, P.Ranhga Rao, PGCIL. M. Young,The technical Writer s Handbook. Mill Valley, CA University science Special report for SC B4 ( HVDC and Power Electronics, V.F Lescale M. Takasaki, CIGRE, Anfis based HVDC control and fault identification of HVDC converter,narendra Bawanel, Anil G. Kothari, and Dwarkadas P.Kothari, HAIT Journal of science and engeneering B, volume 2, Issues 5-6,pp , copyright 2005 holon Academic Institute of All Rights Reserved 199