Simulation of Transformer Based Z-Source Inverter to Obtain High Voltage Boost Ability

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1 Interntionl Journl of cience, Engineering nd Technology Reserch (IJETR), olume 4, Issue 1, October 15 imultion of Trnsformer Bsed Z-ource Inverter to Obtin High oltge Boost Ability A.hnmugpriy 1, M.Ishwry Nirnjn, G.Jgdeeswrn 3 1 Assistnt Professor (ECE), Pollchi Institute of Engineering nd Technology, Pollchi Assistnt Professor(ECE),. Pollchi Institute of Engineering nd Technology, Pollchi 3 PG cholr, ri Eshwr College of Engineering,Coimbtore. Abstrct: The Trnsformer bsed Z-ource inverter is n enhnced series inductnce Z-ource impednce network. This proposed inverter is used to combine the min circuit nd the power source. This configurtion delivers strong boost cpcity to overcome the brriers of the series inductnce Z-source inverter. Further, with the usge of low voltge cpcitors nd the trnsformer, the cpcitor voltge strin gets reduced. The dvntge of projected topology over series inductnce Z-source inverter is tht two built-in cpcitors block DC currents in trnsformer windings nd prevents core sturtion, which results in esy construction with effective cost nd the efficiency is lso improved. The stry inductnce effects re reduced by trnsformer. The min point of the proposed technique is tht, very short shoot through zero stte is essentil to obtin high voltge conversion which improves the output power qulity. This circuit cn be pplied to severl power conversion pplictions which use impednce-type power inverters. The output results of the Trnsformer bsed Z-source inverters re simulted in MATLAB/imulink using 1 degree mode pulse circuit. The simulted output results of the conventionl nd proposed inverters re compred nd verified. Keywords: Improved voltge bility, switched inductor network, trnsformer bsed Z-ource, 1 degree mode pulse opertion. I. INTRODUCTION In the power electronics pplictions, the dc-dc buck/boost converter cts s mjor prt. Using this converter circuit, the input voltge is incresed or decresed corresponding to their pplictions. It is used in lite nd hevy lod conditions. For hevy lod conditions, such s drive pplictions needed high output voltge in the rnge of 415. The input voltge is boosted in order to chieve the high rnge of output voltge. The Z-source inverter services unique impednce network, which is connected between the power source nd inverter circuit, thus providing unique fetures tht cnnot be obtined in the trditionl voltge-source nd current-source inverters [4]. It llows the turning ON of both switches in the sme inverter phse leg (shoot-through stte) without dmging the inverter switches [8]. The problem in the trditionl source inverters re solved by impednce source inverter []. The inverter switches re designed with low voltge bility. The incresed input voltge does not ffect the inverter switches. In the trditionl inverter circuits single stge of power conversion circuit is not vilble. The voltge source inverter cts s buck converter, which step down the input voltge or limit the input voltge nd trnsfer the voltge to the inverter circuit. The current source inverter cts s boost converter which steps up the input voltge or increses the output voltge nd trnsfer the voltge to the inverter circuit. Either buck or boost opertion is possible in the bove mentioned trditionl inverters. An extr circuit is dded to get high or low output voltge. This cuses lower efficiency, high cost nd the circuit becomes complex. It is seriously restricted due to their nrrow obtinble output voltge rnge; shoot through problems cused by misfiring nd other difficulties due to their bridge type structures. II. Z-OURCE INERTER The two cpcitors nd two inductors re connected by mens of cross or X-hpe nd form the Z-ource network is shown in the Fig.1. This is used to boosting the output voltge by incresing the source voltge [1]. The c output voltge in the Z-ource inverter is minly depends on following two prmeters. i. Duty cycle ii. Modultion index Both re relted to ech other. In the pulse genertion circuit, the high duty cycle of the switching period is used then low modultion index is chieved. The switches in the inverter circuit is turned ON nd OFF bsed on the duty cycle vlue. Fig.1 Z-ource network IN: All Rights Reserved 15 IJETR 3495

2 Interntionl Journl of cience, Engineering nd Technology Reserch (IJETR), olume 4, Issue 1, October 15 The min drwbck is tht, lternte switching cretes oscilltions t the output when the lrge duty rtio is used. It degrdes the performnce of the inverter by reducing the mplitude of the c output voltge []. Further high voltge stress is imposed on Z-ource cpcitor nd Inverter Bridge. III. ERIE INDUCTANCE Z-OURCE INERTER In order to void the disdvntges of Z-ource inverter, the series inductnce Z-ource inverter is developed. An extr mount of one inductor nd three diodes re dded into the topmost nd bottommost rms of the Z-ource network to obtin high boost rtio nd it is shown in the Fig.. The boost fctor hs been incresed from 1/( D) to (1+D)/(1 3D). In this inverter, lrge vlue of modultion index is used to reduce the oscilltions t the c output voltges [5]. The duty cycle of the switching period is very short. The pulses for the inverter circuit re generted by using 1 degree mode method. The two operting modes re performed nd their detiled opertion is explined below. A. Non-shoot through stte: In this mode, there re six ctive sttes nd two zero sttes of the min circuit. During this sub-stte, the switch is in OFF condition, wheres both diodes D in nd D o re ON. For the L cell in the upper rm, the diodes D 1 nd D re OFF nd D 3 is ON. The mgnetic energy stored in the series connected inductors L 1 nd L 3 re trnsferred to the min circuit. For the L cell in the lower rm, the diodes D 4 nd D 5 re OFF nd D 6 is ON, the inductors L nd L 4 re connected in series nd the stored mgnetic energy is trnsferred to the min circuit. At the sme time, to supplement the consumed energy of C 1 nd C during the shoot through stte, C 1 is chrged by in vi the bottom L cell nd C is chrged by in vi the top L cell. Fig. eries Inductnce Z-ource inverter I.1 DEGREE MODE PULE CONTROL In this type of control ech switch conducts for 1 degree. Only two switches remin ON t ny instnt of time. The gting signls re shown in Fig.3, the conduction series of switches is 61, 1, 3, 34, 45, 56, 61 nd shoot through stte is represented s following sequence 14, 5, 14, 5, 14. There re three modes of opertion in one hlf cycles. 1 degree mode ws dopted to control ll the topologies discussed in the pper [3], [7]. The wveforms for the switching pulses re shown in the Fig.3. Fig.3 witching Pulse Genertion The developed impednce source inverter intentionlly utilizes the shoot-through zero sttes to boost dc voltge nd produces n output voltge greter thn the originl dc voltge [6]. But the shoot-through zero stte does not ffect the PWM control of the inverter, becuse it equivlently produce the sme zero voltge to the lod terminl. The vilble shootthrough period is limited by the zero-stte period tht is determined by the modultion index. The voltge gin of the Z- source inverter cn be expressed s During mode 1 for wt π/3, trnsistor 1nd 6 conduct. n, bn, cn (1) During mode for π/3 wt π/3, switch 1nd conduct n, bn, cn () During mode 3 for π/3 wt π, switch nd 3 conduct n, bn, cn (3) Line to neutrl voltge cn be expressed s, sinn n (4) n 1,3,5 n t 6 ) sin n bn (5) n 1,3,5 n 3sin n( t ) IN: All Rights Reserved 15 IJETR 3496

3 Interntionl Journl of cience, Engineering nd Technology Reserch (IJETR), olume 4, Issue 1, October 15 n sinn 7 n 1,3,5 n t ) (6) 6 Line to Line voltge cn be expressed s 3 (7) b n b bc c dc where, 3 sinn n 1,3,5 n t ) 3 sinn n 1,3,5 n t ) sinn t n1,3,5 n ) (8) (9) (1) M B (11) o is the output pek phse voltge, dc -input dc voltge, M - Modultion index, B- Boost fctor. B is determined by 1 B 1 D (1) where, Do is the shoot through duty rtio. The control scheme uses high frequency sine crrier tht helps to mximize the output voltge for given modultion index. A. hoot Through For the proposed PWM, the shoot through duty rtio is determined by 1 sin M D (13) The boost fctor B nd the voltge gin cn be clculted: dc M M B 1 sin M (15) In the conventionl 1 degree mode control method, tringulr crrier is used to control the shoot-through duty rtio []. In this cse, the shoot-through time per switching cycle is constnt, which mens the boost fctor is constnt. In this conventionl tringulr crrier PWM the shoot through duty rtio is given expressed s D =1-M (16) In this conventionl 1 degree mode control method, to chieve the high output voltge, it is required to increse the shoot through duty rtio which cn only be chieved with the reduction of modultion index. But smll modultion index results in greter voltge stress on the device, hence it restricts the obtinble gin becuse of the limittion of device voltge rting The proposed control strtegy uses the conventionl sinusoidl reference, wheres the crrier wve is modified for the sme modultion index. For the proposed PWM, the shoot through duty rtio is determined by 1 sin M D (17) The boost fctor B nd the voltge gin cn be clculted: B 1 sin M (18) dc M M B 1 sin M (19). TRANFORMER BAED Z-OURCE INERTER In the eries Inductnce Z-ource inverter, the output voltge (AC oltge) is incresed corresponding to DC input voltge, when incresing the number of inductor stges. The stry inductnce effects re induced, which ffects the performnce of the system. More number of stges mkes the system complexity nd increses the system cost. To remove the bove disdvntge, the trnsformer bsed Z- ource Inverter is proposed [9]. Trnsformer bsed Z-ource Network is the rrngement of the two cpcitors nd one trnsformer tht cn be connected between the dc source nd the inverter bridge while mintining the min fetures of the L Z-source network shown in Fig.4. B 1 sin M (14) IN: All Rights Reserved 15 IJETR 3497

4 Interntionl Journl of cience, Engineering nd Technology Reserch (IJETR), olume 4, Issue 1, October 15 significntly improves the relibility while reducing the output wveform distortion[1]. The exclusive property of this inverter is tht, no energy is stored in the trnsformer windings. The two DC-current blocking cpcitors connected in series with the trnsformer lso prevent the trnsformer core from sturtion during the following three operting modes. hoot through mode Non shoot through mode with ID> Non shoot through mode with ID= Only one inductive element is used to store the energy during the boost opertion. The verge currents of two trnsformer windings over the period of the output voltge re equl zero. I.IMULATION REULT In order to ccomplish single-stge power conversion with buck-boost bilities the proposed inverter is used. This inverter turns on both power switches in leg to boost the dc bus voltge. The current drwn from the dc source is continuous. Both shoot-through sttes nd the trnsformer turn rtio cn be regulted to control the boost voltge gin. The output voltge cn be djusted over wide rnge, nd cn be boosted to higher vlue.both of the power switches in leg cn be turned on t the sme time, which elimintes ded time nd To verify the mentioned theoreticl results, simultion exmple for the voltge inversion from DC 4 to AC 185 (rms) is given in MATLAB which will be difficult to chieve with the eries Inductnce Z-source inverter. Without using ny boost converter circuit high AC voltge ws obtined. The min circuit prmeters re chosen s follows: Trnsformer bsed Z-source impednce network L1 =.5 mh nd C1 = C = 8 μf; 3 phse output filter: Lf = 1 μh, Cf = 1 μf; The switching frequency fs = 1/T = 5 Hz; All components re ssumed idel. Fig.5 imultion digrm for eries inductnce Z-ource inverter IN: All Rights Reserved 15 IJETR 3498

5 Interntionl Journl of cience, Engineering nd Technology Reserch (IJETR), olume 4, Issue 1, October 15 Fig.8 imultion digrm for series inductnce Z-ource inverter Fig.6 Pulses for the circuit Fig.7 Output oltge nd Current wveform for eries inductnce Z-ource inverter (o =155) II.CONCLUION Fig.9 Output oltge nd Current wveform for Trnsformer bse Z-ource inverter (o =185) In this work, the 1 degree pulse genertion circuit is developed nd the gte pulses re generted for the inverter circuit. The eries Inductnce Z-ource inverter is designed in MATLAB environment nd the output voltge is mesured to be 155 for n input of 4. Then the Trnsformer-bsed Z-ource inverter is designed. The generted output voltge of 185 for the sme input voltge of 4 s fed in the previous conditions. The operting modes of the proposed inverter nd its reliztion re discussed. The voltge trnsfer rtios of these inverter circuits hve been observed nd tbulted. Both the inverter outputs re obtined by MATLAB/IMULINK. Among these two inverters, the trnsformer bsed Z-ource inverter provides good performnce in terms of mximum boost output voltge. The mjor dvntges of this proposed inverter re low cost, reduced number of pssive components, high efficiency, reduced stry inductnce losses nd no dditionl circuits needed to boost the output voltge, which is impossible in the trditionl inverters. IN: All Rights Reserved 15 IJETR 3499

6 Interntionl Journl of cience, Engineering nd Technology Reserch (IJETR), olume 4, Issue 1, October 15 REFERENCE [1] F. Z. Peng, Z-source inverter, in Proc. IEEE/IA Annu. Meeting,, pp [] M.. hen, A. Joseph, J. Wng, F. Z. Peng, nd D. J. Adms, Comprison of trditionl inverters nd Z-source inverter for fuel cell vehicles, IEEE Trns. Power Electron., vol., no. 4, pp , Jul. 7. [3] Ding LI, et.l., 1, Generlized Multi-Cell witched-inductor nd witched-cpcitor Z-source Inverters, IEEE ICET Conference Proceedings. [4] M. Zhu nd F. L. Luo, uper-lift dc-dc converters: Grphicl nlysis modelling, J. Power Electron., vol. 9, no. 6, pp , Nov. 9. [5] F. Z. Peng, M. hen, nd Z. Qin, Mximum boost control of the Z- source inverter, IEEE Trns. Power Electron., vol., no. 4, pp , Jul 5. [6] Miosen hen, et.l., 6, Constnt boost control of the Z- source inverter to minimize current ripple nd voltge stress, IEEE Trnsctions on Industry Applictions, ol 4,Issue:3, pp [7] A. Ioinovici, witched-cpcitor power electronics circuits, IEEE Circuits yst. Mg., vol. 1, no. 4, pp. 37 4, ep. 1. [8] B. Ned mohn, Ned Mohn, Undelnd nd Robbin, Power Electronics: converters, Appliction nd design John Wiley nd sons.inc, Newyork, [9] Ding Li, 11 Multi-cell Trns-z-source Inverters IEEE Power electronics, ingpore, 5 8. [1] Amitv Ds1, udipt Bhui, Prth rthi Mondl3,11 Power Qulity Improvement using Impednce Network Bsed Inverter Electricl & Electronics Engineering Deprtment, NHM Knowledge Cmpus West Bengl, Indi, 3 Electricl Engineering. IN: All Rights Reserved 15 IJETR 35