Application of PI and MPPT Controller to DC-DC Converter for Constant Voltage & Power Application

Transcription

1 IOSR Journal of Electrcal and Electroncs Engneerng (IOSR-JEEE) e-issn: ,p-ISSN: 3-333, Volume, Issue 5 Ver III (Sep - Oct 6), PP 8-5 wwwosrjournalsorg Applcaton of PI and MPPT ontroller to - onerter for onstant Voltage & Power Applcaton Nbedta Swan, r K Pangrah, r SM Al 3 Ph Scholar, KIIT Unersty,3 Prof, KIIT Unersty Abstract: Ths artcle presents smulaton of perturb and obsere maxmum power pont trackng (MPPT) algorthm used n solar PV systems wth drect control method The man dfference of the proposed system to exstng MPPT systems ncludes addton of PI control loop along wth MPPT control crcut and nestgaton of the effect of addng to control crcut The resultant system s capable of trackng MPPs accurately wth change n rradaton leel rapdly wthout steady-state oscllaton, and also, ts dynamc performance s satsfactory MATAB and SIMUINK software were employed for smulaton studes I Introducton Renewable energy systems are growng ery fast n all oer the world and the research n PV and wnd motate the researchers to thnk about new control mechansms to mplement for some useful task Ths artcle manly focuses on MPPT based PV system PV modules hae nonlnear characterstcs whch are determned by solar nsolaton and temperature that affects the oerall output power of the system To account for ths nonlnearty, maxmum power pont trackng (MPPT) technque s mplemented to ncrease the effcency of the photooltac system A UK onerter s fed from PV source wth dfferent electrcal characterstcs for transferrng power to a load In ths paper, a PI controller s desgned for the UK conerter to extract the maxmum power from the PV source keepng constant output oltage for a partcular load The Perturb and obsere (P&O) algorthm along wth PI controller mproes the oerall performance of the conerter system One of the energy sources whch are profusely aalable on earth s solar energy The unaalablty of grd power n rural area makes solar energy a better alternate So a standalone PV system can be utlzed there Solar photo oltac system can be connected to grd also for utlsng the PV power Solar panel effcency depends on the solar cell materals and the control mechansm used Maxmum Power Pont Trackng (MPPT) algorthm whch s a new control mechansm s used for extractng maxmum power from PV array rrespecte of enronmental condtons Ths results n ncreased effcency of solar modules UK conerter s placed n between load and PV source The proposed model for ths for ths conerter s gen n Fg: Fg: Schematc representaton of proposed system II esgn of PV Module And MPPT PV module conssts of number of solar cells whch are connected n seres or parallel It conerts sunlght drectly to dc power PV panel works under the phenomenon of photoelectrc effect When solar cell s exposed to sunlght, t conerts solar energy drectly nto electrcal energy Here the PV module conssts of 44 solar cells n seres each hang open crcut oltage of 6 olt and short crcut current of 475 ampere Ths array deelops the power from the solar energy drectly and t wll be changng dependng upon the temperature and solar rradances Fg: show the equalent crcut dagram of a solar cell OI: 979/ wwwosrjournalsorg 8 Page

2 Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage Fg: Equalent crcut dagrams for a solar cell AMPPT Technque Photooltac systems generally use a maxmum power pont trackng (MPPT) technque to extract maxmum possble power from the PV module rrespecte of the perturbaton n nsolaton and temperature PV modules hae relately ery low conerson effcency; therefore t requres MPPT technque for controllng the solar array power The Maxmum Power Pont Trackng (MPPT) s a technque by means of whch maxmum power can be extracted from the Photooltac (PV) Systems To mproe the energy effcency, t s releant to operate the total PV module always at ts maxmum power pont Many maxmum power pont Trackng (MPPT) technques are aalable n the present era and among all these technques P&O and ncremental conductance algorthms are generally used n PV system for obtanng maxmum power pont In ths paper P&O MPPT technque s descrbed n whch t noles the perturbaton n termnal oltage There are arous methods used for maxmum power pont trackng Few are lsted below: Perturb and Obsere method (P&O) Hll clmbng(h) method Incremental onductance (I) method onstant Voltage(V) method onstant urrent ()method Fuzzy logc control(f) Perturb and Obsere method In ths method the power of the module changes due to slght perturbaton If the power ncreases due to the perturbaton then the perturbaton s contnued n that drecton After the peak power s reached the power at the next nstant decreases and hence after that the perturbaton reerses The algorthm s deeloped for settng a reference oltage of the module correspondng to the peak oltage of the module A PI controller then acts mong the operatng pont of the module to that partcular oltage leel Ths algorthm s ery smple and easy to mplement Among descrbed all MPPT methods P&O method s used here for maxmum power pont trackng The flow chart for ths method s shown n fg: 3 Fg:3 Flow chart of Perturb and Obsere method OI: 979/ wwwosrjournalsorg 9 Page

3 Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage The man am of ths controller s to regulate the operatng pont of the system when the enronment condtons ary The dc-dc conerter along wth the solar-pv array regulates the operatng pont through a MPPT controller Here perturb and obsere (P&O) method s used as a MPP trackng The algorthm s programmed n MATAB embedded functon and PI controller s desgned for regulatng the oltage at the output sde From the characterstc cure t s obsered that the maxmum power wll be ncreased and the system effcency wll be decreased by ncreasng the rradance leel In ths paper two control mechansms are used, one s MPPT controller another one s PI controller The MPPT controller s used for maxmum power pont trackng rrespecte of the araton n rradance and temperature and the output of the MPPT controller s the reference oltage whch s compared wth the conerter output oltage The error goes to the PI controller and the output of the PI controller s compared wth the repeatng sequence for generatng gate pulse whch goes to the swtch The use of PI controller makes the output oltage constant III Selecton Of Proper onerter Swtch mode power supples are the replacement of the lnear regulators due to certan factors such as hgh effcency, lght weght, smaller sze and low swtchng losses Buck-boost conerter and UK conerter are often used for ths operaton because both buck operaton and boost operaton for the output oltage can be acheed Although the buck boost confguraton s cheaper than the UK conerter but the dsadantages are dscontnuous nput current, hgh peak currents n power components, and poor transent response, make t less effcent The UK conerter also prodes better output oltage due to the presence of nductor at the output sde Fg: 4 show the crcut confguraton of UK conerter o V R Fg: 4 crcut confguraton of UK conerter In ths conerter the output oltage s opposte to the nput oltage Here the non-solated UK conerter s descrbed n contnuous conducton mode The conerter has two modes of operaton such as swtch on and swtch off mode The dynamc analyss s based upon the oltage equatons and current equatons of nductor and capactor respectely Fg:5 shows the on state of the UK conerter when the swtch s on o V S R Fg: 5 UK onerter durng ON state When the swtch S s on, current flowng n both the nductances ncrease, at the same tme the oltage through capactance reerse bases dode and turns t off When the swtch S s OFF, at the same tme the nput oltage s turned on and the dode s forward based and capactance s charged through, and the nput supply V Fg: 6 shows the off state crcut confguraton of UK conerter o V R Fg: 6 UK onerter durng OFF state OI: 979/ wwwosrjournalsorg Page

4 Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage OI: 979/ wwwosrjournalsorg Page The conerter s operatng n boost mode for PV applcaton The relatonshp between output and nput currents and oltages are gen n equaton () and () respectely () ) ( () ) ( I I V V n o n o The oltage rato and current rato are same as buck boost conerter The only dfference s the nput and output currents are contnuous and rpple free The specfcaton for the UK conerter used n smulaton was selected as follows: Input oltage=5 olt Source sde nductance =mh uty rato=8% Source sde apactance (PV sde )=uf Flter nductance = mh apactor (flter capactor at output sde ) =45uF Resste load =3 ohm Swtchng frequency =5kHz IV Transfer Functon Model of UK onerter The state space model for ON state mode and OFF state mode are gen n equaton (3) and (4) respectely whch can be obtaned from dfferental equaton model and the output oltage remans same for both the states and gen n (5) ) (5 Usng state space aeragng technque as gen n equaton (6) and (7) (7) )] ( [ (6) )] ( [ )] ( [ x d d d B B d x d A A d x o n The transfer functon model wth respect to nput and duty rato s obtaned as n (8) and (9) (4) V R (3) V R

5 Imagnary Axs output oltage (n olt) o ( s) ( SI A) ( s) n ( s) [ SI A] [( A d( s) Where A A d A ( d) Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage B B d B ( d) d ( d) B (8) A ) x ( B B ) n ] ( ) x(9) A, A are the on state and off state matrx, B and B are the on state and off state nput matrx and and are the on state and off state output matrx respectely The transfer functon wth respect to duty rato s obtaned as n () usng equaton (9) Vo( s) d( s) s 778 s 8889 s s s 9 s 5 s 8889 () A Implementaton of PI ontroller The functon of the controller s to reduce the steady state error and to regulate the oltage all tme rrespecte of the load condton and nput oltage araton The magntude of the output oltage for open loop conerter s found to be 9937 olts wth a large oershoot of 9% To reduce the oershoot at the begnnng and to regulate the output oltage PI controller s requred Here the controller parameters are obtaned from Zegler Nchols method The crtcal gan and crtcal tme perod whch are needed for desgnng controller parameters are obtaned from root locus plot Fg: 7 show the root locus plot of the aboe transfer functon and Fg: 8 show the output oltage of the conerter wthout controller x 4 Root ocus output oltage of cuk conerter wthout controller Vo Fg: 7 Root locus plot Real Axs Fg: 8 output oltage of the conerter wthout controller The crtcal gan and crtcal tme perod s calculated from the root locus plot and t s found to be 5 and 45 sec respectely Usng Zegler Nchols table gen n table- the K p and K alues are found to be 76 and 48 respectely Table- ontroller Kp T PI 5 K cr 5T cr The transfer functon of the PI controller s obtaned as n () K Gc ( s) K p s 85s 7 Gc ( s) () s tme(n sec) OI: 979/ wwwosrjournalsorg Page

6 Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage V losed oop Smulaton Model The closed loop model of PV based UK conerter wth MPPT and PI controller s shown n Fg: 9 The MPPT s programmed n MATAB embedded functon and the block s smulated usng the Smulnk blocks aalable n the MATAB lbrary Fg: 9 closed loop model of PV system wth MPPT & PI controller VI Smulaton Results The proposed model s smulated by aryng the rradance leel keepng the temperature constant Aerage annual solar radaton arrng at the top of the Earth's surface s roughly 366 Wp/m So here the rradance alue s ared n between the ranges 8 to 3 watt/m Table- shows the maxmum power at dfferent nsolaton leel Table- Irradance(Wp/m ) V out (olt) P out (watt) V MPP (olt) I MPP (amp) P max (W) effcency % % % % % % From the table t can be obsered that the operatng pont wll change at each tme by aryng the rradance leel keepng constant V MPP The effcency wll be ncreased by decreasng the rradance leel I-V and P-V characterstcs for nsolaton watt peak/m are shown n fg: The effcency can be calculated by usng the formula as gen n () Pmax () V MPP I MPP OI: 979/ wwwosrjournalsorg 3 Page

7 Po(n watt) Vo(n olt) Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage Fg: I~V and P~V characterstc at Wp/m The output oltage and output power waeform shown n fg: and respectely output oltage tme(n sec) Fg: output oltage waeform of the conerter 7 output power tme(n sec) Fg: output power waeform of the conerter The output oltage and output power of the conerter remans constant by aryng the rradance Fg: 3 shows the gate pulse whch goes to the swtch Fg: 3 Gate Pulse to the swtch VII oncluson Here the stand-alone solar-pv generaton system wth UK conerter has been desgned and the performance analyss of the system has been presented usng MATAB/Smulnk software wth dfferent rradance From the steady state analyss t can be obsered that the system attans the maxmum power pont trackng successfully despte of fluctuatons n nsolaton The system can track the maxmum power pont ery quckly when the enronmental condton changes OI: 979/ wwwosrjournalsorg 4 Page

8 Applcaton of PI And MPPT ontroller to - onerter for onstant Voltage References [] Tekeshwar Prasad Sahu, TV xt and Ramesh Kumar, Smulaton and Analyss of Perturb and Obsere MPPT Algorthm for PV Array Usng ĊUK onerter Adance n Electronc and Electrc Engneerng ISSN 3-97, Volume 4, Number (4), pp 3-4 [] uauhtemoc Rodrguez, Member, IEEE, and Gehan A J Amaratunga, Member, IEEE, Analytc Soluton to the Photooltac Maxmum Power Pont Problem IEEE TRANSATIONS ON IRUITS AN SYSTEMS I: REGUAR PAPERS, VO 54, NO 9, SEPTEMBER 7 [3] rvnarasmharao RameshVadd, Smulaton uk onerter Usng Incremental onductance MPPT wth rect ontrol Method Internatonal Journal of Scence, Engneerng and Technology Research (IJSETR), Volume 3, Issue 4, Aprl 4 [4] RBWankhede PROFUBVadya, Energy omparson of MPPT Technques Usng uk onerter Internatonal Journal of Innoate Research n Adanced Engneerng (IJIRAE) ISSN: Volume Issue 6 (July 4 [5] a atherne, Katha Bhaskar, SIMUATION OF A SOAR MPPT HARGER USING UK ONVERTER FOR STANAONE APPIATION Internatonal Journal of Electrcal, Electroncs and omputer Systems (IJEES), ISSN (Onlne): 347-8, Volume-, Issue -, 3 [6] Srusht Rhafle, Uttam B Vadya, ZJKhan, ESIGN OF UK ONVERTER WITH MPPT TEHNIQUE INTERNATIONA JOURNA OF INNOVATIVE RESEARH IN EETRIA, EETRONIS, INSTRUMENTATION AN ONTRO ENGINEERING Vol, Issue 4, July 3 [7] RAHU RAWAT & S S HANE, HI IMBING TEHNIQUES FOR TRAKING MAXIMUM POWER POINT IN SOAR PHOTOVOTAI SYSTEMS-A REVIEW Specal Issue of Internatonal Journal of Sustanable eelopment and Green Economcs (IJSGE), ISSN No: 35-47, V-, I-, 3 [8] W Hart, Introducton to Power Electroncs, Prentce-Hall, Englewood lffs, NJ, 997 [9] Ned Mohan, TMUndeland and WP Robbns, Power Electroncs: onerter, Applcatons and eces, Second Edton, John Wley and Sons, 995 OI: 979/ wwwosrjournalsorg 5 Page