THE UNIVERSITY OF NEW SOUTH WALES. School of Electrical Engineering & Telecommunications

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George Allen
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1 THE UNIESITY OF NEW SOUTH WAES School of Electical Engineeing & Telecommunications EE97 POWE EETONIS FO ENEWABE AND DISTIBUTED GENEATION EXAMINATION Session (Supplementay Exam) TIME AOWED: 3 hous TOTA MAKS: 6 maks TOTA NUMBE OF QUESTIONS: 4 THIS EXAM ONTIBUTES 8% TO THE TOTA OUSE ASSESSMENT. eading time: minutes. This pape contains 5 pages. andidates must ATTEMPT ONY 3 questions. Answe each question in a sepaate answe book. Maks fo each question ae indicated beside the question. This pape may NOT be etained by the candidate. Pint you name, student ID and question numbe on the font page of each answe book. Authoised examination mateials: One A4 sheet of mm gaph pape will be povided. andidates should use thei own UNSW-appoved electonic calculatos. This is a closed book examination. Assumptions made in answeing the questions should be stated explicitly. All answes must be witten in ink. Except whee they ae expessly equied, pencils may only be used fo dawing, sketching o gaphical wok.

2 QUESTION [ Maks] Fo the esonant ZS D-D of Figue 4, the inducto and capacito ae sufficiently lage so that I and o may be consideed to emain constant duing a switching peiod. Switch T epesents an uni-diectional switch. T i i + v D o - Figue 4. The following paametes ae given: = 8, =.5μH, =.μf, o = and P o = W. (a) Sketch the wavefoms fo i and v. [7 maks] (b) Find the peak values of inducto cuent i and capacito voltage v c, and values of impotant tansition times. Useful fomulae: [ maks] The esonant cuent pulse that occus in this convete is given by i I sin t t d o o Zo whee I o is the initial inducto cuent i () which occus at t. Z o Ω o ad/sec. (c) Find the opeating switching fequency, f s, so that o = 4. [3 maks] Please tun ove fo Question

3 QUESTION [ Maks] (a) Non-ideal convetes: Pove fom fist pinciples that the non-ideal boost convete shown in Figue. has the following voltage tansfomation atio and efficiency: d D ( D ) ( D ) [ maks] D T Figue. (b) A half-bidge, seies esonant dc-dc convete, Figue. is fed fom a voltage souce of and is switched at a fequency f. Pove the following expession, sketch the expession showing how it vaies with Q, and descibe the poblem with no-load opeation: Whee and ω o is the esonant fequency. [ maks] T v i v oi o T Figue. 3 Please tun ove fo Question 3.

4 QUESTION 3 [ Maks] (a) Descibe the pupose of the electical enegy geneation system in a wind tubine, making efeence to the following aspects and how they ae contolled: i. Aeodynamic efficiency and tip-speed atio ii. Gid compliance iii. Maximum powe point tacking iv. Ovespeed conditions v. System to deal with loss of mains [ maks] (b) An H-bidge invete connects a D powe souce to the gid though an intefacing inductance of 5mH. The gid is 3, 5Hz with a vaiance of +% and -6% on the supply voltage. i. What is the minimum equied D voltage at the input of the H-bidge if the maximum powe flow fom the D souce to the gid is.5kw at unity powe facto? [4 maks] ii. Unde the conditions in pat (i), what is the load angle of the invete output voltage elative to the gid? [ maks] iii. Detemine the equied modulation index if the input D voltage is 36 and the invete is deliveing full-load (.5kW) into the minimum gid voltage. [3 maks] Please tun ove fo Question 4. 4

5 QUESTION 4 [ Maks] (a) Discuss the main technical easons fo adopting HD tansmission systems ove HA tansmission. [ maks] (b) Daw a schematic diagam of a -pulse, bi-pole HD scheme. lealy mak the tansfome winding connections (delta/wye) fo each tansfome. [3 maks] (c) A six-pulse convete D tansmission system connects a 3kms, A, 5 Hz system to a kms, A, 6 Hz system. The 6-pulse convetes at each tansmission line end ae intefaced by delta-wye (gid:convete) tansfomes of tuns atio 3: such that the tansfome D-side line voltage is double the A side line voltage. The powe tansmission is 5MW to the invete which is maintained at a D voltage level of 5k. The total D line esistance is 8Ω. Detemine: i. The invete delay angle, α i. [ maks] ii. The D-link cuent, ectifie output voltage and ectifie delay angle, α. [3 maks] iii. The ectifie input powe and A, the invete A, and the system efficiency. [3 maks] (d) Daw the schematic diagam of a 3-level diode-clamped bidge leg. Detail all the usable switching states of the bidge leg used in a voltage souce convete. Fo each switching state, identify what effect load cuent polaity has on the state of chage of each individual D-link capacito and note whethe chage o dischage occus fo positive and negative load cuents. [7 maks] End of Pape 5

Sliding Mode Control for Half-Wave Zero Current Switching Quasi-Resonant Buck Converter

Sliding Mode Control for Half-Wave Zero Current Switching Quasi-Resonant Buck Converter Sliding Mode Contol fo Half-Wave Zeo Cuent Switching Quasi-Resonant Buck Convete M. Ahmed, Student membe, IEEE, M. Kuisma, P. Silventoinen Abstact This pape focuses on the pactical implementation of sliding