Khulna University of! ring & Technology Sc. Engineering 4" Year 2™ (Regular) Examination, 2019 Department of Electrical and Electronic Engineering BE 4223, High Voltage DC and Flexible AC Transmission Time: 3 hours Full Marks: 210 i) Answer ANY THREE questions from each section in separate scripts. (Gi) Figures in the Fight margin indicate fll marks, NB. q ‘What are the advantages (15) and disadvantages of HVDC transmission? What is the break-even distance for HVDC in comparison to HVAC transmission? Prove that almost 40 percent more power ean be transmitted using $0 percent less (10) copper in HVDC than HVAC. Give a short description ofthe components of HVDC transmission system. (19) @. | (a) For 6-pulse bridge line commutated HVDC converter, prove thatthe de output (15) voltage Vg = VegCost without any veri, The symbols been usual meaning. (©) A theesphase 12-pulse resifier is fed fiom a transformer with nominal volage (20) rating of 20 KVALIO RV, 445 Aethe primary voltage is 230 KV and the effective tums ratio T is 0.84, determine the de output voltage when the ignition delay angle a is 20° Zand the commutation angle jis 18" (iy ~ Ifthe direct current delivered by the restifier is 2.900 A, Calculate the effective commtating reactance Xe, RMS fundameital component of alterating current, power factor oS 9, and the reactive power at the primary side of the transformer. AE. | (2) Deduce the equation for harmonies ina 12-pulse converter system. What ae non- (15) characteristic harmonies in HVDC system? ~ (b) What are the limitations of line commutated converter? Explain the operating (10) principle ofa two-level singe phase VSC indicating possible curtent paths. (c) A six-pulse HVDC convi rter is connected to a 330 kV/220 kV, 800 MVA,X,= (10) 12% tansformer. Determine the commutation overlap angle if the converter is ‘operating at 20° fring angle and 1800 A DC current. Q4. (@) Describe a coupling capacitor based three level voltage source converter ciruitand (13) explain its operation. What are the advantages and disadvantages of capacitor coupled converters over dice clamped converters? (0) Sketch the basic diagram of a VSC substotion and explain the different eomponents (10) briefly (©) A tvee-phase Vsc operates with 180° conduction and it is connected to delta (12) resistive load R = 600 ©. The converter frequency, f= 60 Hz and the DC voltage is 280 KV. (@ Write down the expression of instantaneous line to line voltage and line current. (Wi Caleulate RMS line and phase voltage. (iii) Calculate the Joad power. Page 1 of 2Section B Show that for a single phase TCR, the susceptance is given by Brex(@) = Bux 2%), where the symbols bea sul meaning Stow the circuit diagram of a practical -pulse TCR-TSC compensitor c Giagram and explain is operation. Dedce the eqvation for ave oF the Paar dexplem te operation ofa general SVC measurement and onto system explain the load sharing aspect of ple eonncted SVCs, Dedue the equation for ESCR. Explain the apliaions of SVC for: steasy site snl unui Salty enhancement. Give necessity diagrams and provide relevant equations. Deserbe the SSSC based tine compenssted system. Explain te real and reactive power compensation with SSSC. Draw thé circuit diagram of a TCSC and explain its modes of operation Dicer the constant erent and onsan angle modes of contol of TCS Discuss onthe aplication of 'CSC for (i) improvement of system stability limit and (i) enhancement of power system Desribe the four quadrant P and Q control of STATCOM. Deduce the state-space model of STATCOM. Show the schematic diagram ofa UPFC and explain the modes of control possible witha UPFC. ‘seit the rel and reactive ower conto ofa transmission system using UPFC. Deuce the relevant equations, Draw a simplified UPFC: contol tock digrem and ‘explain its operation, Page bof 2) ay (2) (2) a (10) (2) ‘Scanned with CamScannerQu Q2 @. NB: @) ) © @) \b) ©) ) © (@) () © @ Khulna University of Engineering & Technology B, Se, Engineering 4% Year 24 Term (Regular) Examination, 2018 Departntent of Electrical and Electronic Engineering EE 4223 High Voltage DC and Flexible AC Transmission Time: 3 hours Full Marks: 210 (i) Answer ANY THREE questions from each section in separate scripts. i) Figures in the right margin indicate full marks, Section A ‘Mention five advantages and inherent problems of HVDC over AC transmission. (10) Define and expl [break even distance in HVDC using proper illustration, Write down the type of HVDC links. Which type is being used in Bangladesh? (15) Draw the schematic diagram of any one type of the HVDC links identifying the ‘main components, State at least two functions of each component. Prove that around 40 percent more power can be transmitted using $0 percent less (10) ccopper in HVDC system than HVAC. ‘What are the converters used for HVDC transmission? Draw the circuit diagram of (13) a voltage source converter and explain the current control of the converter. Explain the basic principle of operation of a shunt-active filer with neat sketch of (12) block diagram and waveforms. A six-pulse HVDC converter is connected to 330 kV AC grid using a 330 KV/220 (10) KV, 800 MVA, X= 1296 transformer. Determine the commutation overlap angle if the converter is operating at 20° firing angle and an 1800 A DC current ‘What is the main drawback of LCC. Explain the operating principle of a two level (10) single-phase VSC indicating possible current paths, For a line commutated converter deduce the equations for de and ac side harmonies. (10) A single-phase VSC inverter has pure inductive load with L = 215 mH. The (15) inverter operates in a square wave fashion with an AC frequency of 50 Hz and DC voltage of 200 V. (H Express the instantaneous converter voltage and load current using the Fourier series, (ii) Calculate the peak and RMS load current, and (iii)Calculate the power absorbed by the load Explain the inverter operation of a three-phase converter. (10) ‘Mention the operating mode of VSC. How does a VSC act as an inverter and (08) reactive power controller? Explain with proper vector diagrams, Sketch the circuit diagram of neutral point clamped multilevel converter and (12) explain the principle of operation ‘State and briefly explain multi-terminal HVDC. Page | of 2 (05)05. (@) Svc 6) © @ eger|® ) © Svc a) Tcsc (b) srarewd] © eS 8.) ox f ©) v| Section B Explain the construction and operation of TCR and TSC, Explain the operating (10) characteristic of TCR and multiple TSC based static var compensator. Deduce the equation for SVC current. Draw the SVC characteristic with mismatched TCR and TSC. Draw and explain general SVC control scheme. Explain the current measurement (09) system for SVC. Explain the IEEE Base Model-I for the SVC control system, (08) ATTCR has a reactance 0.52.0 and firing angle a = 40°, Find out fren (08) Explain the load sharing aspect of parallel connected SVCs. Deduce the equation (10) for ESCR Describe the application of SVC for (i) enhancement of power system transient (13) stability and (i) augmentation of power system damping, ‘An SVC connected to a 735 kV system has a reactive power range of 350 MVAR_ (12) production to 100 MVAR absorption. The droop is set to 5%. The system short circuit level is specified as follows Maximum short-citeuit current, SO KA ‘The minimum short-circuit current under normal operating conditions, 5 kA ‘The minimum short-circuit current during system restoration after loss of transmission line, 500 A Determine (the pu regulator gain that ensures stable operation from 5 kA to 50 kA system short-circuit current, (id) the change of voltage-control response for the system variation and regulator setting in (i) and (iii) the pu regulator gain for stable operation of the system Draw the schematic diagram of a TCSC module used in practice and explain its (13) operation, What are the advantages and requirements of TCSC? Explain the modes of TCSC operation with necessary diagrams. Explain the constant current and constant angle control modes of TCSC. (12) Deduce and explain the steady state model of a STATCOM, 00) Describe the applications of SSSC in power system. (10) Draw the schematie diagram of a UPFC and explain the different control modes of (11) UPFC. Explain real power and var control methodology of'a UPEC. Explain the maximum (14) and minimum power and var control characteristics. Page 2 of 2i patil University of Engineering & Technology oS SNgincering 4 year 2! Term, (Regular) Examination, 2017 tment Of Electrical and Electronic Bing ineering. ER 4223, High Voltage DC and Flexible AC ‘Transmission ime: 3 hours NSB. (i) Answer ANY. Full Marks: 210 q (i) Figures int "THREE questions from eath ection in separate scripts, sight margin indieate fll marks, relly. (© Sie the opening mae of VSC How does 2 VSC act as a9 inveier and reactive (08) St SONI? Explain wid proper vestr Togans sa lay Whee the connected to 330 KV, 50 Hz AC id using a 330 (10) 12% vansformer, Calculate the commutation Bi rating a 10° Ting angle and an T8007 srosformer reactance affects commiaton over ‘he Fimiatons of shanpasive Fier? Eeplain the asc piel of penton (12) shn-atve hr wih ne keh lek dram ud proper wero Menvon sme advantages of VSC oe LEC. substi nd expan edits conponen Wh a te pases uote in cove Show ta harnics i a twelve (12) els OUD 8 mich mor ls tan es cnfguations, Deduee te nie, for Yo and VAY TE pleco (Whats he porn of mi Ay raw the schematic diagram of a VSC.(11) rely. Tevel convener? Deseibe the operation ofa three-level (0) tor malilevel conver, oe a, emat inrm of halide and fulrige MMC cll. Menin some (10) perational advantages of ful bridge over half-bridge MMC. Se aver Bs a ate indutive and with L= 20 ml. The invett (1) Stays Hit wave fchion wih an ACTHEGUETEPO Soe and De veg 200. (Express the instantaneous converter volt iy lage and current. . ee |S) (i) Cate the poner stared th ed we Section B-“ the schema ism ala sgl se TCR and exh is woking paige (11) ‘Show that- ot Brca(0) = Bas (= ="2) 4 cnn ceeaton ofa Grpuse TCR-TSC compenor with tee TSCS. Exlin (07) 5 current characteristics, eee Beant of general SVC contol system, Exphin its operation, (09) c “plain the operation of pulse ratio modulated (PRM) mepawat transducer, (08) (0G schnal dagm of UPFC w JPFC ith back to back VSCs. Explain the contol (12) ‘modes of UPFC for different conditions, Page | of 2 ‘Scanned with GamScannerlication of SVC: in power system ta (i and (i) power system dam fd 10.4 TIS KV 100 MVA absor ed 2 follows, Maximum short-circuit current 50 kA, THe minim short-circuit euten under nornah operating conditions! 5 KA The minima shore “Hrcuit current during system restaration after loss of {ransmission ine: Su0 9, Determine. ver (19) rease steady state power_(10 ae ping contr ae sem has anne poner age of 350 6 1m short circuit tion. The droop is set to 4%6, The syste a3) Production to 1 level is specitie Svc wo ‘The per unit resnletor pein that ‘sites stable operation from:S.kA 10.30 KA system short-circuit curren Show the change of volingen egulator setting as mentione Teermine theeaulior Gun So Sabie operant ie Wie shoes level range S00 A 19 50 ka, ontrol response for the system varintion with d eer iBtfation of 2 TCSC and explain its modes of ‘operation. Whial are the (12) Antages of TSC? Describe the application of TC: Power system stabil (6). Exp Biawe and explain the operating principle of a ST, STAT eo, Cs BPSiraint of the SLATCOM tir Contyal functions « ~Veduce the stealy state mathematical move ot a STATC OM. a9 ¢) Deseribe the architecure of a SSSC° Fa, esse L TC&c 'SC tor imp vement af io g and (12) ATCOM: Deduce the oy wower eXchange via DC tink. What are the STATCOM? yperating (14) 'S operation with modes of real and (11) reactive power changes Scanned by CamScanner ‘Scanned with CamScanner2) tbe te conponens of VDC converte, (0s) Ate the environmental issues in VDC transmissio (7) 2 Qa. (9) Explain the construction and ‘opetation of line commutated converter for HVDC (12) plications Deduce the equation for DC output voltage for 12-pulse eonvertr. Dav the sfemute dagam ote iees ic diagram of a homopolar HVDC system identifying the (12) Z¢_Titin components and explain them briefly. : | JS rw that a grid controled bridge converter without anvaverapacts 2s ason (11) A os ca having a fixed current ratio. 3. Describe the principle of operation of a shunt-active filter with net.sketch of ay Jock diagram and Proper waveforms. To is meant a TEXpl ams (12) erent “SB ‘Six-pulse HVDC converter is connected to 200 kV, 50 Hz AC grid using a (12) ¥ transformer of 220 kV/330 KV, 800 MVA, x, = 12%. Calculate, (9 the communication overt if the rectifier is operating at 30° firing angle I and an 1800 A DC current (1) the safe extinction angle of the converter if the valves have 700 ys tum-off time. Q4. (a) Draw the schematic diagram of | half-bridge and full-bridge MMC cell. Mention (10) some important operational advantages of full-bridge over hal-bridge MMIC. (©) Describe the H-bridge technology of multilevel converters. Show the formation (15) of cascaded multilevel Ti-bridge converters. Explain the applications of ‘multilevel converters for HVDC transmission and FACTS (©) What is meant by minimum ignition dela are not fied at the mi 'y angle? What will happen if valves (10) uum ignition delay angle? Show the proper waveforms. Section B 05.0 (@Show the diferent 'ypes of FACTs devices with theit applications in tabular (08) form 470) Draw'the schematic diagram of a UPFC and explain its regulation (08) characteristics with phasor diagram. (©) Draw and explain the operating principle of a STATCOM. Deduce the ( ‘Scanned with CamScanner/ svt are the control tunctuns of SALOME -nseped of TOSC “Shi the gram of TCSC and mention the avantee 4 the statement “A STATCOM is a controlled reactive power source” - ea Gite AC Show’ the power exchange principle between the STA _ system, rnodel of the Fora STATCOM connected to AC system, deduce the state-space nodel 0 system as , {Explain the subsynchionaus resonance mitigation by STATCOM. Show! ‘control block diagram andl explain its operation Draw the circuit arrangement of single phase TCI and show thal the Fandamental component ofthe TCR curren i aiven bY fy- “2 = VBwox (=S") . where wis the fring angle and a i the oe 7 ' sonduction angle of thyristor. {22} £ Svc. “ For a fixed capacitor-hased SVC. explain the operating characteristics and find Gt the “equations for maximum and minimum susceplance values if it 1s ri Tea Trou ep Gown sioner Jescribe the principle of power massaremigul, Diaw and explain the IEE[ asic let 2 for the SVC control systern and the voRage regulator wie 4 (Deline effective shor citeuit ratio (ESCR). Eyplain operation of tyeo parallel SVP for system bus voltage control t Gscribe the applications of SVC im enhancing. steady state and transient Stability: “A SVC connected to a 735 kV system has a seactive power range of 350 MVAR production to 100 MVA absorption. "The droop is set 16 4%, ‘The system short circuit level is specified as follows The maximum short circuit current: 30 KA ‘The minimum short circuit curren! wader normal operating condition: 5 kA Svc The maximum short circuit current dong system restoration alter loss of a fransnusston line. 500 A. (i) Determine the pu teguluor gain that ensures stable operation from 5 kA to 50 KA short circuit current, (ii) Show the change in voltaye conteol response fe (ii) Determine the pu regulsior gain for sicble operation of the system short circuit levet range 500 A 10 50 kA ange inv the system variation, iv) Show the ‘Scanned with CamScanner ‘ ay (19) tyEAN . i Time: 3 pone” Vole DC and Flexible AC Transminson ij Full Mars 210 j { f / { | 1 atthe minimum ignition delay ange? Show wath FFOP= Jised PF FSS ae be aero BE rainy etap prove ha cosa =easg. nterem (7 idpare delay and power factor angle A sin-pule HYDE converter is comectd 12 220KY, She AC gid wing 2 (19) OK, SOOMVA, x= 12% transformer Calcul, the communication overlap if the ret is operating at "Sing arcis gz he hamonics remove : is meant by miniium inition delay angle? What will agen iLvalves art aa (O77 -wavelorre | tran 800A DC eure! iif teste xno ne oe sme ie vse Tt 2 lee afi cls “Yog = FOIE KBD FEU way = ITE @ is meant by operating mode of VSC? Explain with pope phar gars wer the VSC acts esanmesneandassacisepmosr cpl. EL a Explain the prineipl of operation of a thee-phase VSC. Dost the waveforms ofall (12) a eral ape ti exgession of ineohnae. ©) a meron tock (9) spain the basi principle of operation of 08) mn and proper waveforms. ’Mention the main differences between LCC and multilevel converter (MMC) base VSCHVDC (62) Ot, A whar is meant by modulator sm aytem? Draw the schematic diagram of ells taf bride and ol transmis és MC | Clan te operating priscipe of Fying capacitor mutilevel somveier (Aetion the i sages of this converter. : | lyon 'VSC operates with ‘180 conduction andi is comect to ax existe us ; ad of = 2000. The converter fequency i SOHzand the DC voltage HK )Oblin the expression of nsntnens linet ine volgen ine ete Calculate the RMS line and phase voltage the fundamental remueney. vt a) (iii). Calculate the RMS fine and phase voltage at (iv) Calculate the Joad_power ard total harmonic Sistortion (THD) of te AC j voltage Page 1 of 2 ‘Scanned with CamScannerLs * Section B a Tlasify FACTS devrces and ge a brictantetion to cach of then Menton the 8s dion PSO explicatens of FACT devrces in power stem efeation Draw and explain the operating prnciple af a STATCOM Dice te epenime 126 NO constant of he STATCOM for ati poner exchange wake” nk What are the OL GL/ © contol fmctions of STATCOM? = Se , ab, } yho-tor iyprcal STA ICOM connected to powver system deduce thy seats exuativin HE the as Eelam the operation of Ha Fest Henchman sytem for SSK damn 4 By Co Eroiaite adsantapes of mili evel consereis sn STATCOM operation om f ; cin es n po jaton for TCR watha fring anglew YE, - o A Explain.theopernting characterise of afpractical G-pulse TCR-FSC.compensator with (42 id gilt TSCs Show the current clmnucteniatic ot the system <0" wr vs the block diagram of the measurement system for a yeqeral SVL cos (LY Ca ener eee Y F Memon the que inputs foie wert asc modes stg vat compenssir_0%) (SVC) contrat fc rica er gent TR (ete be yes & o a, Explain the operation Df v0 parallel SCs with (1) a difference in reference voltage (17 indastESCR G) = gait SVC in power syste for fUyifa reas dy sae power Sm diene tof texient sabi Jo a TSK system, kas.a reactive power range ef 350 MVAR (1 produetioi's 14 100 MVA absception. The droop is get 10 3 (To eee is 2petified 2: follows, Vie wacimim ations GMrer ‘ite curent under norma! operat sireuit current during system restoration af tranemussivn line. 580A, (0) Deterruing the pu regulator gain thar enautes stable operation frum SKA to SOKA system short eeu current 6) Gi} Sow the change of veliage control response for the systein variation and FeBulator scting i item ¥ of hos sublst (hi Determine the pu rg. yo caret Revel range S00 19 “The systems shart eirentit ) ¢ gain for stabie operation in the syste short ska, Qs Draw the schematic disgran of a TCSC module used tn practice and explain ts “Ge> What are the advantages and requirements of TCSC? Expain the modes of a ees TC$Coperatjon with necessary diagrams FS e Pe Describe thelconstant, OL Le enhances dantping? # - + Draw the schematic diagram of aFFC and explain its operation. Exptam the voltage 11 70" regulation, impedance compensation, angie contiol and mutatis nh © UPPC. Deduce thie power & VAK contol possible with UPFC. - aa Ny : a oe etek eoatrat oF ‘ ‘Scanned with CamScanner