COMPARISON ANALYSIS OF SHUNT ACTIVE FILTER AND TRANSFORMERLESS PARALLEL HYBRID ACTIVE FILTER

Transcription

1 COMPARISON ANALYSIS OF SHUNT ACTIVE FILTER AND TRANSFORMERLESS PARALLEL HYBRID ACTIVE FILTER Saksh Banga 1, P.R.Sharma 2 and Maneesha Garg 3 1,2 Department of Electrcal Engneerng, YMCA Unersty Of Scence and Technology, Fardabad 1 sakshbanga@gmal.com, 2 prsharma1966@gmal.com 3 Department of Humantes and Appled Scence, YMCA Unersty Of Scence and Technology, Fardabad Garg_maneesha@yahoo.com ABSTRACT Ths research work presents the comparson analyss of Shunt Acte Flter (SAF) wth Parallel Hybrd Acte Flter (PHAF). The performances of SAF and PHAF hae been analyzed wth PI controllers based on Synchronous Reference Frame theory. In each case, smulaton s carred out for three phase unbalanced non lner load condtons. The adantages of the desgned system and the proposed current reference calculaton methods are erfed by smulatons usng MATLAB Power system Toolbox. KEYWORDS Power qualty, shunt acte flter, transformer-less shunt hybrd acte flter, Total Harmonc Dstorton 1. INTRODUCTION Harmoncs are njected n source current due to the applcaton of non-lnear load. These harmonc currents nfluence the functon of other equpment connected on the smlar dstrbuton feeder, ncludng the harmonc producng loads. Among number of solutons conentonally passe flters offers a low cost soluton. They generally offer hgh seres mpedance or low shunt mpedance to block the partcular harmonc content. Howeer there are certan dsadantages lke fxed compensaton characterstcs and resonances wth the source mpedance. Thus n orders to preal oer the demerts assocated wth tradtonal passe flters, Acte Power Flters (APF) hae been ntroduced n recent years. APF plays a tal role for controllng the amount of harmonc polluton present n a dstrbuton system. They can be connected n seres, shunt or combnaton of seres and shunt wth the supply mpedance. Typcally shunt APF conssts of a three phase oltage source nerter wth capactor on dc sde. For large power applcatons, t s dffcult to mplement a low loss and a low cost PWM Jan Zzka (Eds) : CCSIT, SIPP, AISC, PDCTA pp , CS & IT-CSCP 2013 DOI : /cst

2 374 Computer Scence & Informaton Technology (CS & IT) conerter. When ths equpment s connected n shunt to the ac source mpedance t s possble to mproe the compensaton characterstcs of the passe flters n parallel connecton [1], [2].Ths forms the transformerless Parallel Hybrd Acte Flter The am of PHAF s to mtgate the problems assocated wth SAF and passe flters and to complement and enhance ther performance by addng acte or passe components to ther structure [3].Fgure 1 shows the block dagram of transformerless parallel hybrd flter. 2. PRINCIPLE OF OPERATION Fgure 1. Block Dagram of Parallel Hybrd Acte Flter Hybrd acte flters effectely mtgate the problems of a passe and an acte flter and prode cost-effecte harmonc compensaton, partcularly for hgh-power nonlnear loads [4].The parallel hybrd flter conssts of three phase oltage source nerter wth capactor on the dc sde connected n shunt wth the tuned passe flter. Shunt passe flter s a seres combnaton of a capactor and a reactor tuned to a specfc harmonc frequency. Snce nonlnear load contrbutes the major contrbuton of harmoncs n the source current manly due to lower order harmoncs thus tuned flter prodes low mpedance trap to harmonc. Remanng hgher order harmoncs only are to be fltered by shunt acte flter; hence ts power ratng can be reduced The compensaton of harmoncs n the source current through enhancement of the compensaton characterstcs of the passe flters also elmnates the chances of resonance [5]. The performance of the PHAF depends on the computaton of reference compensatng sgnal. Among many control strateges mentoned for estmatng the reference compensatng current Instantaneous Reacte Power (IRP) theory [6, 7] and Synchronous Reference Frame (SRF) are mostly used. [8].These schemes employ the computaton of the reference components through subtracton of poste sequence fundamental current component from the load/source current. These control strateges are ery attracte for ther smplcty and ease of mplementaton, but lack n prodng adequate soluton under extreme or seere condton of fault condtons n

3 Computer Scence & Informaton Technology (CS & IT) 375 passe flter branch. SRF control technque usng proportonal ntegral (PI) type controller are s mplemented to strength the currents of the flter to follow ther reference alues. 3. SYSTEM CONFIGURATION A three phase parallel hybrd acte flter s mplemented for unbalance nonlnear load. The test system conssts of shunt connected acte flter wth shunt passe LC elements tuned 5th harmonc frequency whch the most promnent frequency s causng the dstorton n source current. Passe flters are desgned to result n mnmum Root Mean Square (RMS) alue of supply current at full load [9,10]. Proposal of Synchronous Reference Frame theory s ncluded n [11]. 4. DESIGN PARAMETERS OF SHUNT ACTIVE FILTER A shunt acte flter conssts of three phase, 6 pulse oltage source nerter. The lne-lne oltage s consdered as 415V. The desgn for dc bus capactor, dc bus oltage and ac nductor are as follows DC Capactor Voltage The mnmum dc bus oltage should be greater than twce of the peak of the phase oltage of the system [13]. The dc bus oltage s calculated as V = 2 dc 3 2 V L L m (1) where, m s the modulaton ndex =1 and s consdered as 1 and VLL s the ac lne oltage of three phase source DC Bus Capactor The alue of dc bus capactor (C dc )s gen by 1 2 [( 2 ) dc dc dc1 2 C V V ) ( )] = 3V ( ai t (2) where, Vdc s the reference dc oltage and Vdc1 s the mnmum oltage leel of dc bus, a s the oer loadng factor taken as 1.2, V s the phase oltage, I s the phase current and t s tme by whch the dc bus oltage s to be recoered AC Flter The ac nductance (Lf) depends on the current rpple cr,p-p, swtchng frequency f s, dc bus oltage (V dc ).Thus Lf s gen as

4 376 Computer Scence & Informaton Technology (CS & IT) where, crp-p,= 5% L f = 3 12 a mv f s dc crp p 5. DESIGN PARAMETERS OF PASSIVE FILTER The basc of shunt passe flter s to trap the tuned harmonc component n the source current usng LC crcut. At resonance frequency nducte reactance s equal to that of capacte reactance. Hence for sngle tuned flter, resonance frequency s gen by (3) f 1 = (4) 2π L f C f Thus to desgn the sze of capactor, frst step s to fxed the reacte power compensaton.hence capactance can be calculated by X V 2 L L = (5) kvar flter c. where V L-L s lne lne source oltage kvar s the fxed reacte power compensaton 6. CONTROL STRATEGY The man functon of the SRF control strategy s to prode hgh resstance at the fundamental frequency and also zero mpedance s presented to harmonc current flowng n to the passe flter. [12].The control dagram s shown n Fg 2. Fg 2 Synchronous Reference Frame Control Scheme

5 Computer Scence & Informaton Technology (CS & IT) 377 In ths three phase load current s transformed nto d-q statonary reference frame usng Parks Transformaton. Usng ths fundamental component appears as DC quanttes and all other harmoncs are transformed as non-dc quanttes. These quanttes are not requred hence these can be flter out usng low pass flter. The extracted dc components and are transformed back nto a b c coordnates to obtan the fundamental components of source currents. To compensate for the nerter losses PI controller s appled to regulate the DC bus oltage. The output of PI controller at the dc bus oltage of acte flter s consdered as the current (l oss ) for meetng ts losses. + ( + (6) where, de de( n 1) k = ) loss ( n) loss( n 1) pd de( n) de( n 1) d de( n) s the error between the reference( dc *) and sensed ( dc ) dc oltage at the nth samplng nstant. K pd and K d are the proportonal and the ntegral gans of the dc bus oltage PI controller. The reference source current s therefore expressed as, * = + d dd loss (7) Smlarly PI controller s used to regulate reacte power + ( + (8) k = ) qr ( n) qrs( n 1) pq te( n) te( n 1) q te( n) The reference supply quadrature axs current s as k k * = + q qd qr (9) where, * te ( n) s ( n) = denotes the error between reference ( s *) and actual( s(n )) termnal oltage ampltudes at the n samplng nstant. K pq and K q are the proportonal and the ntegral gans of the PI controller. 7. MATLAB IMPLEMENTATION A three phase transformerless hybrd acte flter s mplemented usng MATLAB Power system Toolbox. Three phase nput source oltage of 415V, 50 Hz frequency wth source resstance of 0.2 ohms and nductance of 2mH s consdered. A three phase unbalance nonlnear load drawng 5A s consdered for smulaton. Shunt acte flter s consttuted of 6 pulse VSI wth 2200 e-6f of capactance attached to the DC sde. A small-rated flter has been ncluded to mnmze the swtchng rpples at the nerter output. Passe elements of the flter are calculated usng the mathematcal relaton s consderng 50% of fxed reacte compensaton. Table1 ges the detaled parameters of the system.

6 378 Computer Scence & Informaton Technology (CS & IT) Table 1. Detaled Parameters of the System. Parameters Supply oltage Loads: Shunt Acte Flter: Interfacng Inductance DC bus capactance Referenced Dc oltage Tuned Passe Flter Values 415V (L-L), 50 Hz () Lnear: phase a= 25Ω Phase b=10 Ω and 80mH Phase c =10 Ω and 80 mh () Nonlnear: Three phase full brdge rectfer drawng 15A L f = 5.5 mh 22000e-6F. 750 V C 5 =129.4e-6F ;L 5 =3.1mH 8. RESULTS AND DISCUSSION The performance of the presented SRF control strategy s ealuated usng by comparson of pure shunt acte power flter and parallel hybrd power flter. The three phase unbalance nonlnear load consdered here n the present system contans 5th harmonc content as the most promnent factor whch causes the dstorton n the source current. Hence the passe elements of the hybrd flter are tuned for the resonance frequency of 250Hz. The VA ratng requred for the nerter n the hybrd flter s much lesser than that requred n a pure shunt acte flter. The VA ratng requred of the nerter n parallel hybrd power acte flter s gen by VA ratng= 3 Where I FMAX V 13 dc I FMAX 2 2 A s the maxmum flter current. Also the apparent power ratng of nonlnear load s gen by VA ratng= 3 V Srms I Lrms Where V Srms and I Lrms are the RMS alue of source oltage taken as 415 V and load current taken as 38A. The apparent rato of the parallel hybrd flter and nonlnear load s greatly reduced by 16%. Another factor whch determnes the aldaton of acte flters s Total Harmonc Dstorton (THD) s reduced from14.74 % to 2.65 % for phase a. Table II shows the THD for all three phases for dfferent types of flter. It can be seen from Fg 5 and Table III that parallel hybrd flter system s able to reduce the 5th harmonc of supply current to 1.68%.The THD of the ac supply current reduces to 3.27% wth pure shunt acte power flters alone as the major component of the load current wthout any flter s composed of 5th harmonc.

7 Computer Scence & Informaton Technology (CS & IT) 379 TABLE III Harmonc Current n Percentage of Fundamental Current 5th 7th 11th 13th 17th 19th Load current Source current wth Passe Flter Source current wth Pure Shunt Acte Flter Source current wth Shunt Hybrd Acte Flter Fgure 3 shows the waeform of load current wthout flter. Fg 4 and 5 shows the waeform of source current wth pure shunt acte flter and parallel hybrd acte flter respectely. These waeforms clearly llustrates that load current s ery dstorted that mples source current at ths tme wthout flterng s also ery dstorted. Wth the applcaton of power flter source currents can be made snusodal.clearly wth the applcaton of parallel hybrd acte flter source current s less dstorted and contans less harmoncs content as compared to pure shunt acte flter. Fg 6 shows the uncompensated and compensated reacte power usng parallel hybrd acte flter.snce the passe elements are tuned at fxed 50% compensaton, fg 6 clearly aldates the passe parameters of hybrd flter. Fg7 demonstrates the source oltage, source current, load oltage, load current, DC bus oltage, and flter current for parallel hybrd acte flter. TABLE II THD For Dfferent Phases (n percentage) Phase Type of flter Phase a Phas e b Phase c Load current wthout flter Pure shunt acte flter Parallel hybrd flter

8 380 Computer Scence & Informaton Technology (CS & IT) Fgure 3 Load current Fgure 4 Source Current wth Pure Acte Flter Fgure 4 Source Current wth Parallel Hybrd Acte Flter Fgure 6 Load Reacte Power and Source Reacte power usng parallel Hybrd Acte Flter

9 Computer Scence & Informaton Technology (CS & IT) 381 Fgure 7 Source Voltage, Source Current, Load Voltage, Load Current, DC Bus Voltage, Flter Current. 9. CONCLUSIONS In ths work, concept of transformerless parallel hybrd acte flter s defned and erfed by MATLAB smulaton. Smulaton results erfy that presented method has good performance n the elmnaton of selecte harmonc content and Total Harmonc Dstorton. It has much better dynamc response wth less ratng compared wth the pure shunt acte flter. REFERENCES [1] B. Sngh, K. Al-Haddad, and A. Chandra, A reew of acte flters for power qualty mproement, IEEE Trans. Ind. Electron., ol. 46, no. 5, pp , Oct [2] J.W. Dxon, G. Venegas, and L. A.Moran, A seres acte power flter based on a snusodal currentcontrolled oltage-source nerter, IEEE Trans. Ind. Electron., ol. 44, no. 5, pp , Oct [3] Bhattacharya,Dan, Synchronous Frame based controller mplementaton for a hybrd seres acte flter,confeence record of IEEE Industry Apllcatons Conference Vol, 3,pp October [4] S. Sranthumrong and H. Akag, A medum-oltage transformerless AC/DC power conerson system consstng of a dode rectfer and a shunt hybrd flter, IEEE Trans. Ind. Appl., ol. 39, no. 3, pp , May/Jun [5] H. Fujta, T. Yamasak and H. Akag, "A hybrd acte flter for dampng of harmonc resonance n ndustral power systems," IEEE Trans. on Power Electroncs, ol. 15, no. 2, pp , March 2000.

10 382 Computer Scence & Informaton Technology (CS & IT) [6] H. Fujta, H. Akag, "A Practcal Approach to Harmonc Compensaton n Power Systems-Seres Connecton of Passe, Acte Flters," IEEE Trans. on Ind.. Appl., ol.27, no.6, pp , No./Dec [7] F.B. Lbano, J.A.Cobos, J. Uceda, "Smplfed control strategy for Hybrd Acte Flters", IEEE PESC Record, 1 997, pp [8] P.T. Cheng, S. Bhattacharya and D. Dan, "Expermental Verfcaton of Domnant Harmonc Acte Flter for Hgh Power Applcatons",IEEE Trans. on Ind. Appl., ol. 36, pp , March/Aprl, [9] IEEE Gude for Applcaton and Specfcaton of Harmonc Flters IEEE Std [10] V, Verma, S. Shanker, B. Sngh, A. Chandra, and Kamal Al- Haddad, "Genetc Algorthm Based Desgn of Passe Flters for Offshore Applcatons," Proc. ofieee PCIC '04, 2004, pp [11] S. Bhattacharya, D. Dan and B. Banerjee, Synchronous frame harmonc solator usng acte seres flter, EPE-Frenze, Vol. 3, pp , [12] V, Verma, S. Shanker, B. Sngh, Desgn and Implementon of Current Controlled Parallel Hybrd Power Flter. [13] B.N.Sngh, P.Rastgoufard, B.Sngh, A.Chandra and K.Al.Haddad, Desgn,smulaton and mplementaton of three pole/ four pole topologes for acte flters, IEE Eletr. Power Appl., ol. 151, no. 4, pp , July Authors Saksh Banga receed the B.Tech degree n Instrumentaton and Control from MDU Rohtak and M.Tech degree n Electrcal Engg. from YMCA UST n 2004 and 2006, respectely. She s pursung Ph.D n Power Qualty from Maharsh Dayanand Unersty, Inda. Presently she s workng as Assstant Professor n Electrcal Engneerng Department at YMCA UST Fardabad. Dr. P.R.Sharma was born n 1966 n Inda. He s currently workng as Charman of the Department n Electrcal Engg. n YMCA Unersty Of Scence and Technology, Fardabad. He receed hs B.E Electrcal Engneerng n 1988 from Punjab Unersty Chandgarh, M.Tech n Electrcal Engneerng (Power System) from Regonal Engneerng College Kurukshetra n 1990 and Ph.D from M.D.Unersty Rohtak n He started hs carrer from ndustry. He has ast experence n the ndustry and teachng. Hs area of nterest s Optmal locaton and coordnated control of FACTS deces,power system stablty and control Dr. Maneesha Garg dd her Ph.D(Physcs) n 2002 from Kurukshetra Unersty, Inda. After that she worked as Research Assocate granted by CSIR, n NIT Kurukshetra for 4 years. She has 18 publcatons n natonal, nternatonal journals and more than 30 papers n conferences to her credt. Presently she s workng as Assstant Professor n Humantes and Appled Scence Department, YMCA UST, Fardabad and gudng 4 scholars for ther research work.