An Energy-Stored Quasi-Z-Source Inverter Using SVPWM Technique

Transcription

1 International Journal of Engineering ehnial Researh (IJER) ISSN: -0869, olume-, Issue-7, July 04 An Energy-Store Quasi--Soure Inverter Using SPWM ehniue Dhya k homas, Rajkumar.G Astrat he uasi--soure inverter (QSI) with attery operation ale the stohasti flutuations of photovoltai (P) power injete to the gri/loa. wo strategies are use to ontrol the new energy-store QSI when applie to the P power system. hey ontrol the inverter output power, trak the P pel s maximum power point, mage the attery power, simulteously. he voltage oost inversion, energy storage are integrate in a single-stage inverter. he QSI raws a onstt urrent from the P pel, thus, there is no nee for extra filtering apaitors. he QSI features a lower omponent (apaitor) rating; reues swithing ripples seen y the P pels. It injets the ative/reative power into the gri y the inverter regulates the attery state of harge (SOC). It ontrols the P pel output power (or voltage) to maximize energy proution. QSI is est suite interfae for photovoltai power generation system oul prove to e highly effiient, when implemente with the improve spae vetor ontrol tehniues. his tehniue reues the harmonis espeially thir fifth orer harmonis. Inex erms Energy storage, Quasi--soure inverter (QSI), SPWM, SPWM. I. INRODUCION he rapily inreasing environmental egraation aross the gloe is posing a major hallenge to evelop ommerially feasile alternative soures of eletrial energy generation. hus, a huge researh effort is eing onute worlwie to ome up with a solution in eveloping environmentally long-term sustainale solution in eletri power generation. he major players in renewale energy generation are photovoltai (P), win farms, fuel ell, iomass. Photovoltai (P) are arrays (omination of ells) that ontain a solar voltai material that onverts solar energy into eletrial energy. P ell is a asi evie for Photovoltai Systems. Suh systems inlue multiple omponents like mehial eletrial onnetions mountings various mes of regulating (if reuire) moifying the eletrial output. he urrent voltage availale at the P evie terminals e iretly use to fee small loas like lighting systems or small DC motors. Energy soures suh as solar, fuel ell, win have a wie voltage hge. he -soure inverter (SI) presents a new single-stage struture to ahieve the voltage oost/uk harater in a single power onversion stage. his type of onverter hle the P voltage variations over a wie rge without Musript reeive July 9, 04. Dhya k homas, Department of EEE, Nehru College of Engineering Researh Centre, HRISSUR Rajkumar.G, Department of EEE, Nehru College of Engineering Researh Centre, HRISSUR. overrating the inverter. As a result, the omponent ount system ost are reue, with improve reliaility ue to the allowe shoot through state. Reently propose uasi--soure inverters (QSI) have some new attrative avtages more suitale for appliation in P systems. Quasi--soure inverter (QSI) is a power onversion tehnology suitale for interfaing of renewale soures. wo strategies are with the relate esign priniples to ontrol the new energy-store QSI when applie to the P power system. hey ontrol the inverter output power, trak the P pel s maximum power point, mage the attery power, simulteously. QSI raws a onstt urrent from the P pel, thus, there is no nee for extra filtering apaitors. he voltage oost inversion, energy storage are integrate in a single-stage inverter. In aition, the intermittent unsheule harateristis of solar power limit the appliaility of P systems. herefore, muh of the literature suggests the aition of energy storage system (ESS) to work in onjuntion with P power generation to make its output power ontinuous, stale, smooth. Moreover, when applie as a gri-onnete system, it implements other importt auxiliary servies normally provie y speial expensive euipment. Most of the existing ESS tehnologies employ iiretional / onverter to mage the atteries whih makes the system omplex, inreases its ost, ereases its reliaility. A. Quasi--Soure Inverter he uasi z-soure inverter (QSI) is a single stage power onverter erive from the -soure inverter topology, employing a uniue impee network. he onventional SI CSI suffer from the limitation that triggering two swithes in the same leg or phase leas to a soure short in aition, the maximum otainale output voltage not exee the input, sine they are uk onverters proue a voltage lower th the input voltage. Both -soure inverters uasi--soure inverters overome these rawaks; y utilizing several shoot-through zero states. A zero state is proue when the upper three or lower three swithes are fire simulteously to oost the output voltage. Sustaining the six permissile ative swithing states of a SI, the zero states e partially or ompletely replae y the shoot through states epening upon the voltage oost reuirement. Quasi--soure inverters (QSI) auire all the avtages of traitional soure inverter. he impee network ouples the soure the inverter to ahieve voltage oost inversion in a single stage. By using this, the inverter raws a onstt urrent from the P array is apale of hling a wie input voltage rge. It also features lower omponent ratings, reues swithing ripples to the P 9

2 An Energy-Store Quasi--Soure Inverter Using SPWM ehniue pels, auses less EMI prolems reue soure stress ompare to the traitional SI. B. QSI Network he QSI iruit iffers from that of a onventional SI in the LC impee network interfae etween the soure inverter. he uniue LC ioe network onnete to the inverter rige moify the operation of the iruit, allowing the shoot-through state whih is forien in traitional SI. his network will effetively protet the iruit from amage when the shoot through ours y using the shoot-though state, the (uasi-) -soure network oosts the -link voltage. he impee network of QSI is a two port network. It onsists of inutors apaitors. his network is employe to provie impee soure, oupling the onverter to the loa. he soure e a attery, ioe retifier, thyristor onverter or P array. he output voltage of the QSI is regulate the output power is etermine y orresponing loa ems. C. Operating Priniple of QSI he two moes of operation of a uasi z-soure inverter are: () Non-shoot through moe (ative moe). () Shoot through moe. ) Ative moe In the non-shoot through moe, the swithing pattern for the QSI is similar to that of a SI. he inverter rige, viewe from the DC sie is euivalent to a urrent soure, the input voltage is availale as DC link voltage input to the inverter, whih makes the QSI ehave similar to a SI. A ontinuous urrent flows through the ioe D. ) Shoot hrough Moe In the shoot through moe, swithes of the same phase in the inverter rige are swithe ON simulteously for a very short uration. he soure however oes not get short iruite when attempte to o so eause of the presene LC network, while oosting the output voltage. he DC link voltage uring the shoot through states, is ooste y a oost fator, whose value epens on the shoot through uty ratio for a given moulation inex. he ioe D is turne off ue to the reverse-ias voltage. L D C L II. QSI BAERY USING SPWM Fig. shows just one of the energy-store QSI topologies, we onnet the attery in parallel to the apaitor C.hey have ommon points: ) here are three power soures/onsumers, i.e., P pels, attery, the gri/loa, ) as long as ontrolling two power flows, the thir one automatially mathes the power ifferene, aoring to the power euation P in P out + P B = 0 () where P in, P out, P B are the P pel power, the output power of the inverter, the attery power, respetively. he power Pin is always positive eause the P pel is single iretional power supply, P B is positive when the attery elivers energy negative when asoring energy, Pout is positive when the inverter injets power to the gri. in il L id C D + - C C - + C ie ib ic B il P PN L i Q Q Q5 Q Q4 Q6 N Fig.. New energy-store QSI for P power generation O AC LOAD here are three operating states of the attery. When the attery is harging, thus i >0, i L >i L,P attery >0, P P >P loa; when the attery is isharging,i <0,i L <i L, P attery <0, P P <P loa ; no harging isharging, i = 0, i L = i L,P attery = 0, P P = P loa. he gri-injete ative power is hge to ahieve the esigne operating moes. hree ases have een investigate: ) Battery harging moe ) Neither harging nor isharging moe ) Battery isharging moe. Battery Charging Moe in C Q Q Q5 O AC LOAD he P pel reeive high solar irraiation. With the MPP algorithm, the P pel outputs high output urrent i L power P in to the energy-store inverter. Light gri-injete power P out results in P in > P out. he power ifferene (P in P out = P ) presents the superfluous P power that is harge into the attery in the negative attery urrent. Q Q4 Q6. Battery Neither Charging Nor Disharging Moe Fig.. Quasi soure inverter he P pel reeive low solar irraiation. As a result, the P pel proue low output urrent i L power P in to the energy-store inverter. he gri-injete ative power is ajuste to math the P power, i.e., P in = P out. For this ase, 94

3 there is no ative power ifferene inputte into the attery, i.e., P = P in P out = 0 W. he attery will e neither harging nor isharging for the zero attery urrent.. Battery Disharging Moe he P pel reeive low solar irraiation, leaing to low urrent i L power P in. he gri-injete ative power is inrease to a high level, suh that P in < P out. he gri reuires muh more ative power th that P pel oul provie to trak the esire value. For this situation, the attery will isharge, proviing a positive urrent to supply the power shortfall. Finally, the gri injete ative power reahes its esire value through the omination (P out = P + P in ) of the P pel attery powers. A. Sinusoial pulse with moulation he voltage soure inverter that use PWM swithing tehniues have a DC input voltage (DC = S) that is usually onstt in magnitue. he inverter jo is to take this DC input to give AC output, where the magnitue freueny e ontrolle. here are several tehniues of Pulse With Moulation (PWM).he effiieny parameters of inverter suh as swithing losses harmoni reution are prinipally epene on the moulation strategies use to ontrol the inverter. In this the Sinusoial Pulse With Moulation (SPWM) tehniue has een use for ontrolling the inverter as it e iretly ontrolle the inverter output voltage output freueny aoring to the sine funtions. Sinusoial pulse with moulation (SPWM) is wiely use in power eletronis to igitize the power so that a seuene of voltage pulses e generate y the on off of the power swithes. he PWM inverter has een the main hoie in power eletroni for eaes, eause of its iruit simpliity rugge ontrol sheme. Sinusoial Pulse With Moulation swithing tehniue is ommonly use in inustrial appliations or solar eletri vehile appliations. SPWM tehniues are haraterize y onstt amplitue pulses with ifferent uty yles for eah perio. he with of these pulses are moulate to otain inverter output voltage ontrol to reue its harmoni ontent. Sinusoial pulse with moulation is the mostly use metho in motor ontrol inverter appliation. In SPWM tehniue three sine waves a high freueny trigular arrier wave are use to generate PWM signal. Generally, three sinusoial waves are use for three phase inverter. he sinusoial waves are alle referene signal they have 0 phase ifferene with eah other. he freueny of these sinusoial waves is hosen ase on the reuire inverter output freueny (50/60 Hz). he arrier trigular wave is usually a high freueny (in several KHz) wave. he swithing signal is generate y omparing the sinusoial waves with the trigular wave. he omparator gives out a pulse when sine voltage is greater th the trigular voltage this pulse is use to trigger the respetive inverter swithes. In orer to avoi unefine swithing states unefine AC output line voltages in the SI, the swithes of y leg in the inverter not e swithe off simulteously. he phase outputs are mutually phase shifte y 0 gles. International Journal of Engineering ehnial Researh (IJER) ISSN: -0869, olume-, Issue-7, July 04 Fig.. SPWM Signal Generation ehniue for hree Phase oltage Soure Inverter III. PROPOSED CONROL SRUCURE B. Spae vetor pulse with moulation Spae etor Moulation (SM) was originally evelope as vetor approah to Pulse With Moulation (PWM) for three phase inverters. It is a more sophistiate tehniue for generating sine wave that provies a higher voltage to the loa with lower total harmoni istortion. he main aim of y moulation tehniue is to otain variale output having a maximum funamental omponent with minimum harmonis. Spae etor PWM (SPWM) metho is ave omputation intensive PWM metho possily the est tehniues for variale freueny rive appliation. C. A spae vetor PWM DC S S S5 a S S4 S6 a' Fig.4. hree-phase oltage Soure PWM Inverter ' ' O AC LOAD he iruit moel of a typial three-phase voltage soure PWM inverter is shown in Figure-4. S to S 6 are the six power swithes that shape the output, whih are ontrolle y the swithing variales a, a',, ', '. When upper swith is swithe on, i.e., when a, or is, the orresponing lower trsistor is swithe off, i.e., the orresponing a', ' or ' is 0. herefore, the on off states of the upper swith S, S S 5 e use to etermine the output voltage. 95

4 An Energy-Store Quasi--Soure Inverter Using SPWM ehniue ale. Swithing etors, Phase oltages Output Line to Line oltages oltage etors Swithing etors Line to neutral voltage Line to line voltage A B C n n a a / -/ -/ / / -/ / / -/ / / / / -/ / / -/ / here are eight possile ominations of on off patterns for the three upper power swithes. he on off states of the lower power evies are opposite to the upper one so are easily etermine one the states of the upper power trsistors are etermine. he eight swithing vetors, output line to neutral voltage (phase voltage), output line-to-line voltages in terms of DC-link, are given in ale o implement the spae vetor PWM, the voltage euations in the a referene frame e trsforme into the stationary referene frame that onsists of the horizontal () vertial () axis. axis a axis Fig.5. he Relationship of a Referene Frame Stationary Referene Frame (00) (/,/ ) 4 (0) (-/,0) 4 axis 0 (000) 7 () 5 (0) ref (00) 5 6 (00) (0) ( /, / ) ( /, / ) 6 (/,/ (/,0) Fig.6. Basi Swithing etors Setors ) axis his trsformation is euivalent to orthogonal projetion of [a,, ] t onto the two imensional perpeniular to the t vetor [,, ] (the euivalent - ple) in a three-imensional oorinate system. As a result, six non-zero vetors two zero vetors are possile. Six nonzero vetors ( - 6) shape the axes of a hexagonal as epite in Fig.5. fee eletri power to the loa. he gle etween y ajaent two non-zero vetors is 60 egrees. Mewhile, two zero vetors (0 7) are at the origin apply zero voltage to the loa. he eight vetors are alle the asi spae vetors are enote y 0,,,, 4, 5, 6, 7. he same trsformation e applie to the esire output voltage to get the esire referene voltage vetor ref in the - ple. he ojetive of spae vetor PWM tehniue is to approximate the referene voltage vetor ref using the eight swithing patterns. One simple metho of approximation is to generate the average output of the inverter in a small perio, to e the same as that of ref in the same perio. herefore, spae vetor PWM e implemente y the following steps: Step. Determine,, ref, gle (α) Step. Determine time uration,, 0 Step. Determine the swithing time of eah trsistor (S to S6) 5.. SEP : Determine,, ref, gle (α),, ref, gle (α) e etermine as follows ref t freueny n 0 os60 n. n n os0 n. n n n n n.os 60.os 0 t πft, where f = funamental axis ref a, axis Fig.7. oltage Spae etor its Components in (, ). 5.. SEP : Determine time uration,, 0 he swithing time uration e alulate as follows: Swithing time uration at Setor 96

5 0 ref 0 t t... ref os( )... sin( ) ref Where, (0 sin. a. 4 sin sin. a. sin ( ), where, 0 5 fz International Journal of Engineering ehnial Researh (IJER) ISSN: -0869, olume-, Issue-7, July 04 os sin ref a SEP : Determine the swithing time of eah trsistor (S to S6) ale. Swithing ime Calulation at Eah Setor Setor Upper swithes(s,s,s 5) Lower swithes(s 4,s 6,s ) s = + + 0/ s = + 0/ s 5= 0/ s 4= 0/ s 6= + 0/ s = + + 0/ s = + 0/ s = + + 0/ s 5= 0/ s = 0/ s = + + 0/ s 5= + 0/ 4 s = 0/ s = + 0/ s 5= + + 0/ 5 s = + 0/ s = 0/ s 5= + + 0/ 6 s = + + 0/ s = 0/ s 5= + 0/ s 4= + 0/ s 6= 0/ s = + + 0/ s 4= + + 0/ s 6= 0/ s = + 0/ s 4= + + 0/ s 6= + 0/ s = 0/ s 4= + 0/ s 6= + + 0/ s = 0/ s 4= 0/ s 6= + + 0/ s = + 0/ Fig.8. shows just one of the energy-store QSI topology, where the attery is onnete in parallel with the apaitor C. Output voltage of P pel is 00, whih is given to the QUASI--soure, that oost the voltage given to the inverter. Inverter onverts the voltage into a voltage, otaining a ontain ripples whih is filtere y LCL filter. Output voltage otaine is 00 three phase a, whih is given to the a gri or to the loa. Output also ontains the power fator, ative power reative power. P pel uses MPP tehniue, whih proues uty ratio for the swithing of the QUASI--Soure inverter. Duty ratio is otaine y using ANFIS ontroller. Fig.9. Output voltage, urrent, PFC waveforms In Fig.9 output voltage is 00 three phase a voltages output urrent is 5 Ampere three phase urrent. In power fator orretion the voltage urrent of y one phase is taken, are almost in phase with eah other. Analysis:. he total harmoni istortion was alulate to e. for SPWM.40 for SPWM.. he power fator was otaine as 0.9 for SPWM.97 for SPWM. I. SIMULAIONS AND RESULS ale.simulation Parameters of SPWM & SPWM ehniue Name Power fator alue HD% SPWM.9.0% SPWM.97.40% Fig.8. Energy-store QSI for P power generation 97

6 An Energy-Store Quasi--Soure Inverter Using SPWM ehniue. CONCLUSIONS P array has een simulate integrate to the QSI with maximum power point traking algorithm (ANFIS metho). he QSI inherits all the avtages of the SI features its uniue merits. It realize uk/oost power onversion in a single stage with a wie rge of gain that is suite well for appliation in P power generation systems. Furthermore, QSI with attery has avtages of ontinuous input urrent, reue soure stress, lower omponent ratings when ompare to the traitional SI. Compare to SPWM the otal harmoni istortion (HD) lower orer harmonis (LOH) ontents are erease in SPWM. Spae etor PWM provies more effiient use of supply voltage in omparison with sine PWM. Energy-store QSI using SPWM tehniue was simulate in MALAB/SIMULINK, the output of simulate iagram experimental results was oserve alyse. REFERENCES [] Baoming Ge, Haitham Au-Ru, Fg heng Peng, Qin Lei, Aníal. e Almeia, Ferno J.. E. Ferreira, Dongsen Sun, Yush Liu, An Energy-Store Quasi--Soure Inverter for Appliation to Photovoltai Power System, IEEE rs. In. Eletron., vol. 60, no. 0, pp , Ot. 0. [] Haitham Au-Ru, Atif Ial Sk.MoinAhme, QUASI soure inverter ase photovoltai generating system with maximum power point traking using ANFIS, IEEE rs. In. Eletron., vol. 4, no pp , J. 0. [] X. Wg,. Fg, J. Li, L. Wg, S. Ni, Moeling ontrol of ual-stage high-power multifuntional Psystem in o oorinate, IEEE rs. In. Eletron., vol. 60, no. 4, pp , Apr. 0. [4] B. Inu Ri, G. Sarava Ilgo, C. Nagami, Control strategy for power flow magement in a Psystem supplying DC loas, IEEE rs. In. Eletron., vol. 60, no. 8, pp , Aug. 0. [5] S. Sreeraj,K. Chatterjee, S.Byopahyay One yle ontrolle single-stage,single-phase voltage sensor-less gri-onnete Psystem, IEEE rs. In. Eletron., vol. 60, no., pp. 6 4, Mar. 0. [6] J. Chavarria, D. Biel, F. Guinjo, C. Meza, J. Negroni, Energy ale ontrol of P asae multilevel gri-onnete inverters for phase-shifte level shifte pulse-with moulations, IEEE rs. In. Eletron., vol. 60, no., pp. 98, J. 0. [7] G. Petrone,G. Spagnuolo, M. itelli, An alog tehniue for istriute MPP P appliations, IEEE rs. In. Eletron., vol. 59 no., pp , De. 0. [8] D. innikov,i. Roasto, R. Strzeleki, M. Aamowiz, Step-up DC/DC onverters with asae uasi-z-soure network, IEEE rs. In. Eletron., vol. 59, no. 0, pp , Ot