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  Bidirectional Inverter with Buck/Boost MPPTSystem for PV Application   ANUJA PRASHANT DIWAN PRANATI KATYAL M.ANANDAN, PG student Associatet Proessor, !o. r#,Associate Proessor, !o. r#,De$t o %&ectrica& And %&ectronics, De$t o %&ectrica& And %&ectronicsDe$t o %&ectrica& And %&ectronics,M.N.M Jain %n ineerin 'o&&e e, M.N.M Jain %n ineerin 'o&&e e,M.N.M Jain %n ineerin 'o&&e e,,Jot(i Na ar, Jot(i Na ar, Jot(i Na ar,T(orai$a))a*+-- -/, T(orai$a))a*+-- -/, T(orai$a))a*+-- -/,Ta*i&nadu,India Ta*i&nadu,India Ta*i&nadu,India adiwan_p@yahoo.com  Abstract   : In this paper the workin! of idirectional inverter with uck/ oost MPPT system for PV application is descri ed#Bidirectional inverter is essential for the power flow control etween dc us and ac !rid# Also idirectional inverter is used forthe re!ulation of dc us volta!e within certain ran!e of volta!e#Also  as the PV array volta!e varies accordin! to theirradiation  cell temperature etc# MPPT is analysed usin! uck  oost converter to e$tract ma$imum availa le power from PVarray# This also reduces the volta!e stress on the inverterconnected across it# The comparison etween the conventionalmethod and the proposed method is also presented# %inally thesimulation results for the proposed method is presented#  Keywords  0 Bidirectional inverter, buck/boost maximumpower point trackers (MPPTs), dc-distribution applications. I.I  NTR1DU'TI1N SI&'(  $ast e2 3ears ,*an3 t3$es o rene2a4&eener 3, suc( as $(oto5o&taic !P6#, 2ind, tida&, and eot(er*a&ener 3, (a5e attracted a &ot o attention . A*on t(ese natura&resources, 4ein c&ean, 7uiet, $o&&ution ree, and a4undant, t(eP6 ener 3 is a *ain and a$$ro$riate rene2a4&e ener 3 or &o2+5o&ta e dc+distri4ution s3ste*s.8i . 9. 'oni uration o a dc+distri4ution s3ste*.In t(e dc+distri4ution a$$&ications, a $o2er s3ste*, inc&udin rene2a4&e distri4uted enerators !DGs#, dc &oads !&i (tin , air conditioner, and e&ectric 5e(ic&e#, and a 4idirectiona& in5erter,is s(o2n in 8i . 9, in 2(ic( t2o P6 arra3s 2it( t2o*a:i*u* $o2er $oint trac)ers !MPPTs# are i*$&e*ented.Since t(e i–v c(aracteristics o t(e P6 arra3s are non&inear,and t(e3 re7uire MPPTs to dra2 t(e *a:i*u* $o2er ro*eac( P6 arra3. Moreo5er, t(e 4idirectiona& in5erter (as tou&i&& rid connection !se&& $o2er# and rectiication !4u3 $o2er# and to contro& t(e $o2er &o2 4et2een dc 4us and ac rid, and to re u&ate t(e dc 4us to a certain ran e o 5o&ta es. T(e e:istin *et(od consistin o t2o+sta econi uration (a5in a 4oost con5erter to ste$ u$ t(e P6+arra35o&ta e c&ose to t(e s$eciied dc+&in) 5o&ta e, as s(o2n in 8i .;. T(e 4oost con5erter is o$erated in 43+$ass *ode 2(en t(eP6+arra3 5o&ta e is (i (er t(an t(e dc+&in) 5o&ta e, and t(ein5erter 2i&& unction as an MPPT. Ho2e5er, since t(ec(aracteristics o P6 arra3s are dierent ro* eac( ot(er, t(ein5erter o$erated in 43+$ass *ode cannot trac) eac(indi5idua& *a:i*u* $o2er $oint accurate&3, and t(e in5erter suers ro* as (i (+5o&ta e stress as t(e o$en 5o&ta e o t(earra3s. To re&ease t(is &i*itation, an MPPT to$o&o 3, 2(ic(co*4ines 4uc) and 4oost con5erters is $ro$osed in t(is $a$er.8i . ;. 'on5entiona& t2o+sta e P6 in5erter s3ste* 2it( 4oost+t3$e MPPTs.  T(e contro& a& orit(* or trac)in *a:i*u* $o2er $oints is 4ased on a constant 5o&ta e *et(od. T(e MPPT 2i&& s2itc(o$eration *odes 4et2een 4uc) and 4oost 2(en t(e out$ut5o&ta e o a P6 arra3 is c&ose to t(e dc+4us 5o&ta e. To e&i*inate &ea)a e round current circu&atin t(rou ( P6arra3s and round, se5era& transor*er&ess in5erter to$o&o ies2ere $ro$osed. %5en t(ou ( t(e3 can ac(ie5e (i ( eicienc3,t(e3 re7uire *ore co*$onents t(an t(e con5entiona& u&&+ 4rid e to$o&o 3. To re u&ate t(e dc+4us 5o&ta e or t(e rid+connected in5erter,t(e contro&s, suc( as ro4ust, ada$ti5e, andu<<3 2ere ado$ted. W(en ado$tin t(ese contro&s or t(estudied dc+distri4ution s3ste*, a (ea53 ste$+&oad c(an e at t(edc+4us side 2i&& cause (i ( dc+4us 5o&ta e 5ariation and&uctuation,and t(e s3ste* *i (t run a4nor*a&&3 or dro$ intounder or o5er 5o&ta e $rotection. =u&)3 dc+4us ca$acitors can 4e ado$ted to increase t(e (o&d+u$ ti*e and su$$ress t(e&uctuation o t(e dc+4us 5o&ta e >9?@, 4ut it 2i&& increase t(esi<e and cost o t(e s3ste* si niicant&3. Additiona&&3, e5ent(ou ( t(ere are a$$roac(es to ac(ie5in ast dc+4us 5o&ta ed3na*ics, t(e s3ste*s 2it( &oad connected to t(e dc 4us (a5enot 4een studied 3et >9@, >9/@. T(ereore, to o$erate t(e dc+distri4ution s3ste* eicient&3 2(i&e reducin t(e si<e o dc+ 4us ca$acitors, a droo$ re u&ation *ec(anis* accordin to t(ein5erter current &e5e&s is $ro$osed in t(is stud3.In t(is $a$er, o$erationa& $rinci$&e and contro& &a2s o t(es3ste* are irst descri4ed, and t(e MPPT contro& a& orit(*,2or)in o 4idirectiona& in5ereter is t(en addressed.%:$eri*enta& resu&ts ro* a sin &e+$(ase4idirectiona& in5erter 2it( t2o 4uc)4oost MPPTs are $resented.8i . B. 'oni uration o t(e studied P6 in5erter s3ste* 2it(t(e 4uc)4oost MPPTs.II. 1P%RATI1N   AND   W1RKING   18   =IDIR%'TI1NAL   IN6%R%TR  To ac(ie5e t(e desired $eror*ance o t(e $ro$osed P6in5erter s3ste*, its o$erationa& $rinci$&e is irst $resented andt(e contro& &a2s or t(e in5erter o$eration are t(en deri5ed.8i . B s(o2s a coni uration o t(e $ro$osed sin &e+$(ase 4idirectiona& in5erter 2it( t2o 4uc)4oost MPPTs, 2(ic( canu&i&& eit(er rid+connection *ode or rectiication *ode 2it(P8'.D'+to+A' con5erters are )no2n as in5erters. T(eunction o an in5erter is to c(an e a dc in$ut 5o&ta e to acout$ut 5o&ta e o desired *a nitude and re7uenc3. T(eout$ut 5o&ta e cou&d 4e i:ed or 5aria4&e at i:ed or 5aria4&ere7uenc3. A 5aria4&e out$ut 5o&ta e can 4e o4tained 435ar3in t(e in$ut dc 5o&ta e and *aintainin t(e ainconstant. 1n t(e ot(er (and, i t(e dc in$ut 5o&ta e is i:edand it is not contro&&a4&e, a 5aria4&e out$ut 5o&ta e can 4eo4tained 43 5ar3in t(e ain o t(e in5erter, 2(ic( is nor*a&&3acco*$&is(ed 43 $u&se+2idt(+*odu&ation !PWM# contro&2it(in t(e in5erter. T(e in5erter ain *a3 4e deined as t(eratio o t(e ac out$ut 5o&ta e to dc in$ut 5o&ta e.T(e out$ut 5o&ta e 2a5eor*s o idea& in5erterss(ou&d 4e sinusoida&. Ho2e5er, t(e 2a5eor* o $ractica&in5erters are non sinusoida& and contain certain (ar*onics.8or &o2+and *ediu*+$o2er a$$&ications, s7uare+2a5e or 7uasi+s7uare C2a5e 5o&ta es *a3 4e acce$ta4&e and or (i (+ $o2er a$$&ications, &o2 distorted sinusoida& 2a5e or*s arere7uired. Wit( t(e a5ai&a4i&it3 o (i (+s$eed $o2er se*iconductor de5ices t(e (ar*onic conductor de5ices, t(e(ar*onic contents o out$ut 5o&ta e can 4e *ini*i<ed or reduced si niicant&3 43 usin &o2 $ass i&ters.  A. FORWARD MODE OF OPERATION  In or2ard *ode o o$eration t(e in5erter 2or)s asD'+A' con5erter t(at con5erts D' 5o&ta e o4tained ro*so&ar $ane& and 4uc)4oost con5erter into A' 2(ic( can 4esu$$&ied to rid.It consists o t2o ar*s 2it( a t2o se*iconductor s2itc(es on 4ot( ar*s 2it( anti$ara&&e& ree2(ee&in diodesor disc(ar in t(e re5erse current. In case o resisti5e+inducti5e &oad, t(e re5erse &oad current &o2 t(rou ( t(esediodes. T(ese diodes $ro5ide an a&ternate $at( to inducti5ecurrent 2(ic( continue so &o2 durin t(e Turn 188condition.T(e s2itc(es are T9, T;, TB and TE. T(e s2itc(es in eac( 4ranc( is o$erated a&ternati5e&3 so t(at t(e3 are not in sa*e*ode !1N 188# si*u&taneous&3 .In $ractice t(e3 are 4ot(188 or s(ort $eriod o ti*e ca&&ed 4&an)in ti*e ,to a5oids(ort circuitin . T(e s2itc(es T9 and T; or TB and TE s(ou&do$erate in a $air to et t(e out$ut. T(ese 4rid es &e s ares2itc(ed suc( t(at t(e out$ut 5o&ta e is s(ited ro* one toanot(er and (ence t(e c(an e in $o&arit3 occurs in 5o&ta e2a5eor*. I t(e s(it an &e is <ero, t(e out$ut 5o&ta e is a&so<ero and *a:i*a& 2(en s(it an &e is F.  %i!ure )# Sin!le Phase %ull wave Brid!e Inverter T9T;TBTE6 A 6 = 6 A= 1N1881881N 6 S ;++6 S ;6 S 1881N1N188 6 S ; 6 S ;++6 S 1N1881N188 6 S ;++6 S ;-1881N1881N++6 S ; 6 S ;- Ta le * Switchin! States T(is is t(e 4asic t3$e o in5erter. Its out$ut is aa&ternatin s7uare 2a5e. T(e (ar*onic content in t(is 2a5e is5er3 &ar e. T(is in5erter is not eicient and can i5e seriousda*a e to so*e o t(e e&ectronic e7ui$*ent. =ut due to &o2cost, it (as so*e &i*ited nu*4er o a$$&ications in (ouse(o&da$$&iances. %i!ure + S,uare -ave Inverter .utput So 2(i&e desi nin a sin &e $(ase in5erter o ratin ;;-6 or ;B-6, t(e 4asic t(in s 2e (a5e to desi n is L' 8i&ter and 2e (a5e to c(oose an a$$ro$riate ste$+u$ Transor*er.  ' %ilter A &o2 $ass L' i&ter is re7uired at t(e out$ut ter*ina&o 8u&& =rid e 6SI to reduce (ar*onics enerated 43 t(e $u&satin *odu&ation 2a5eor* %i!ure 0 ' %ilter . W(i&e desi nin L+' i&ter, t(e cut+o re7uenc3 isc(osen suc( t(at *ost o t(e &o2 order (ar*onics ise&i*inated. To o$erate as an idea& 5o&ta e source, t(at *eansno additiona& 5o&ta e distortion e5en t(ou ( under t(e &oad5ariation or a non&inear &oad, t(e out$ut i*$edance o t(ein5erter *ust 4e )e$t <ero. T(ereore, t(e ca$acitance 5a&ues(ou&d 4e *a:i*i<ed and t(e inductance 5a&ue s(ou&d 4e*ini*i<ed at t(e se&ected cut+o re7uenc3 o t(e &o2+$assi&ter. %ac( 5a&ue o L and ' co*$onent is deter*ined to *ini*i<e t(e reacti5e $o2er in t(ese co*$onents 4ecause t(e reacti5e $o2er o L and ' 2i&& decide t(e cost o L' i&ter and it is se&ected to *ini*i<e t(e cost, t(en it isco**on t(at t(e i&ter co*$onents are deter*ined at t(e set o a s*a&& ca$acitance and a &ar e inductance and conse7uent&3t(e out$ut i*$edance o t(e in5erter is so (i (. Wit( t(esedesi n 5a&ues, t(e 5o&ta e 2a5eor* o t(e in5erter out$ut can 4e sinusoida& %i!ure 1# output votla!e of inverter with ' filter  B. REVERSE MODE OF OPERATION  W(en t(e so&ar ener 3 is not suicient o itis not a5ai&a4&e , to re u&ate t(e D' &ine 5o&ta e , t(e su$$&3 ista)en ro* t(e rid !4u3 $o2er#. W(ic( needs to con5ert t(eA' $o2er ro* t(e rid to t(e re7uired D' 5o&ta e. T(at*eans t(e in5erter (as to 2or) as a rectiier.   %i!ure 2 'ircuit dia!ram for 3everse power flow T(us , 2(en t(e so&ar ener 3 is &ess, t(e i5erter ta)esA' $o2er ro* rid , con5ert it into D' and eed t(e Dc &ine.In con5ertin A' 5o&ta e to D' , t(e in(erent diodesconnected ani$ara&&e& to M1S8%T $&a3s i*$ortant ro&e. T(us 2(i&e o$eratin in re5erse *ode o o$eration ,t(e ate $u&ses to t(e M1S8%Ts are re*o5ed. So t(e s2itc(es2i&& 4e in 43$ass *ode . no2 t(e diodes connected anti$ara&&e&2i&& act as uncontro&&ed 4rid e rectier , and con5erts A' toe7ui5a&ent D' 2(ic( 2i&& 4e su$$&ied to &oad. III.1P%RATI1N 18 TH% PR1P1S%D =U'K=11STMPPTST(e MPPT to$o&o 3 is or*ed ro* a 4uc) con5erter anda 4oost con5erter.8or 5arious P6+arra3 a$$&ications, t(e t2oMPPTs 2i&& 4e connected se$arate&3 or in $ara&&e&. T(e MPPTsenses P6 5o&ta e v P6, dc+4us 5o&ta e v dc  , and inductor current iLm into t(e sin &e+c(i$ *icrocontro&&er !98E A# todeter*ine o$erationa& *ode and dut3 ratio or trac)in t(e*a:i*u* $o2er $oint accurate&3. W(en 5o&ta e v P6 is(i (er t(an v dc, t(e MPPT is o$erated in 4uc) *ode, ands2itc(  M  9 is turned 1N to *a neti<e inductor  Lm and t(usincrease inductor current iLm . W(i&e s2itc(  M  9 is turned 188,inductor  Lm re&eases its stored ener 3 t(rou ( diodes  D 9 and  D ; . 1n t(e ot(er (and, t(e MPPT is o$erated in 4oost *ode2(en 5o&ta e v P6 is &o2er t(an v dc, and s2itc(es  M  9 and  M  ;are turned 1N to *a neti<e inductor  Lm . W(i&e s2itc(  M  ; isturned 188, inductor  Lm re&eases its stored ener 3 t(rou (diode  D ; . T(us, t(e contro& &a2s can 4e e:$ressed as o&&o2sAndTo dra2 *a:i*u* $o2er ro* P6 arra3s, constant 5o&ta eor trac)in *a:i*u* $o2er $oints is ado$ted. I t(e*a:i*u* $o2er &e5e& o a P6 arra3 is(i (er t(an t(e $o2er ratin o an MPPT, t(e t2o MPPTs 2i&& 4e in $ara&&e& o$eration to unction as a sin &e MPPT. T(us, itre7uires an on&ine coni uration c(ec) to deter*ine t(econnection t3$es o t(e t2o MPPTs, se$arate&3 or in $ara&&e&. A. Costat Vo!ta # m#t$o% T(e constant 5o&ta e a& orit(* is 4ased on t(eo4ser5ation ro* IC6 cur5es t(at t(e ratio o t(e arra3s*a:i*u* $o2er 5o&ta e, 6*$, to its o$en+circuit 5o&ta e,6oc, is a$$ro:i*ate&3 constant 6*$  6oc  K  9. T(econstant 5o&ta e a& orit(* can 4e i*$&e*ented usin t(e&o2c(art s(o2n in 8i ure T(e so&ar arra3 is te*$orari&3 iso&ated ro* t(eMPPT, and a 6oc *easure*ent is ta)en. Ne:t,t(e MPPTca&cu&ates t(e correct o$eratin $oint and t(e $reset 5a&ue o K, and adusts t(e arra3s 5o&ta e unti& t(e ca&cu&ated 6*$ isreac(ed. T(is o$eration is re$eated $eriodica&&3 to trac) t(e $osition o t(e MPP. A&t(ou ( t(is *et(od is e:tre*e&3si*$&e, it is diicu&t to c(oose t(e o$ti*a& 5a&ue o t(econstant K. T(e &iterature re$orts success 2it( K 5a&ues ran in ro* /B to -. 'onstant 5o&ta e contro& can 4e easi&3i*$&e*ented 2it( ana&o (ard2are. Ho2e5er, its MPPTtrac)in eicienc3 is &o2 re&ati5e to t(ose o ot(er a& orit(*s.Reasons or t(is inc&ude t(e aore*entioned error in t(e 5a&ueo K, and t(e act t(at *easurin t(e o$en+circuit 5o&ta ere7uires a *o*entar3 interru$tion o P6 $o2er.It is a&so $ossi4&e to use a constant current MPPTa& orit(* t(at a$$ro:i*ates t(e MPP current as a constant $ercenta e o t(e s(ort+circuit current. To i*$&e*ent t(isa& orit(*, a s2itc( is $&aced across t(e in$ut ter*ina&s o t(econ5erter and s2itc(ed on *o*entari&3. T(e s(ort+circuitcurrent is *easured and t(e MPP current is ca&cu&ated, and t(eP6 arra3 out$ut current is t(en adusted 43 t(e MPPT unti& t(eca&cu&ated MPP current is reac(ed. T(is o$eration is re$eated $eriodica&&3. Ho2e5er, constant 5o&ta e contro& is nor*a&&3a5ored 4ecause o t(e re&ati5e ease o *easurin 5o&ta es,and 4ecause o$en+circuitin t(e arra3 is si*$&e to acco*$&is(, 4ut it is not $ractica&&3 $ossi4&e to s(ort+circuit t(e arra3 !i.e.,to esta4&is( <ero resistance across t(e arra3 ter*ina&s# and sti&&*a)e a current *easure*ent.
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