A Dual Second-Order SOGI based Control Algorithm for UPQC under Distorted Grid and Load Conditions

Transcription

1 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp A Dual SecondOrder SOGI baed Control Alorithm for UPQC under Ditorted Grid and Load Condition Hareehkumar Yada 1 Reearch Scholar, Department of Electrical Enineerin, JNTU, Hyderabad, Telanana, India. 1 ORCID: Dr.M.S.R Murthy Profeor, Department of Electrical Enineerin, CMRCET, Hyderabad, Telanana, India. Raju Chintakindi 3 At.Prof, Department of EEE, aadevi Collee of Enineerin, Waranal, Telanana, India. Abtract Thi paper preent a SecondOrder Second Order Generalized Interator (SOSOGI) baed control alorithm for UPQC (Unified Power Quality Conditioner), an interation of DR and DSTATCOM. Thi paper mainly aim to mitiate ource voltae and load current harmonic, unbalance and power factor improvement. In thi paper, SOSOGIPLL (PhaeLocked Loop) i employed for UPQC to enerate reference voltae and current inal for enhancin power quality at the utility main. SOSOGI baed PLL i utilized for power quality enhancement becaue of it dynamic repone, better harmonic and inter harmonic compenation, trackin accuracy and fater detection of reference inal under all varyin load and rid condition. The propoed threephae UPQC i utilized for mitiation of voltae harmonic, current harmonic, a and well with a imple control technique. The control alorithm i teted and evaluated uin MATLAB/Simulink. Keyword: Power Quality (PQ), Phae Locked Loop (PLL), SecondOrder Second Order Generalized Interator (SO SOGI), and Unified Power Quality Conditioner (UPQC). INTRODUCTION Nonlinear load are increain widely and cauin mot evere problem at the point of common couplin (PCC). Today day of interet i toward renewable enery ource for production of electricity. In thi reard, inlephae and threephae photovoltaic (P) power eneration i increain widely for reidential and commercial application. In order to interate thee P ytem, Grid connected converter are utilized. But, thee are creatin evere power quality (PQ) iue at the rid ytem like harmonic eneration, ource unbalancin and power factor deterioration. Similarly, nonlinear load uch a rectifier, arc furnace and fluorecent lamp etc are cauin current related problem uch a harmonic, unbalance and exceive reactive power demand etc. [14]. 9% of interruption are due to voltae a and to be compenated within 3 cycle. oltae well are le frequent; but, thee well are producin electromanetic tre in power tranformer due to flux aturation [5]. Nearly 48% of power quality problem are due to voltae a/well and % are due to harmonic [6]. Any problem in voltae / current will lead to the malfunctionin of cutomer load and may damae enitive load in term of power quality [7]. Cutom power device (CPD ) uch a DR (Dynamic oltae Retorer), DSTATCOM (Ditribution Synchronou Compenator and UPQC (Unified PQ Conditioner) are more uperior to paive filter and provide bet olution for power quality iue. A UPQC i a combination of DR and DSTATCOM and provide inle olution for both voltae and current related problem with a common DC link capacitor at the DC bu. An attempt to improve the performance of UPQC i made by introducin SOSOGI baed QSG and PLL for etimation and extraction of fundamental voltae and current inal under ditorted rid and load condition. Different UPQC topoloie are explained in the literature uch a Intantaneou PQ theory [8], Synchronou Reference Frame (SRF) theory [9], In [1], three control alorithm uch a UT (Unit oltae Template), DQ Theory and theory baed on Fourier analyi are compared for inlephae application. The performance of UPQC depend on the trackin accuracy of voltae and current, peed and control method that wa employed. Keepin accuracy and reliability in view, many PLL technique are propoed in literature uch a SRFPLL, 489

2 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp EPLL, ParkPLL [11][1], and SOGIPLL [13] etc. Every PLL ha it own advantae and diadvantae and SOGI PLL i found atifactory under ditorted condition with low computational burden a only one control ain aociated with it. In thi paper, SOGI baed control alorithm i employed for UPQC to compenate a, well, unbalance and harmonic. A inlephae SOGIPLL i ued for all the three phae to increae the effectivene, better etimation and accuracy of threephae balanced inuoidal inal. However, thi implementation for UPQC baed on PLL alorithm are reported le in the literature. Simulation are carried out uin MATLAB / Simulink, and impower ytem block et. PROPOSED CONFIGURATION AND CONTROL ALGORITHM The UPQC hown in Fi. 1 comprie of two voltae ource converter with 6 IGBT witche in each converter feedin Linear/Nonlinear load. The UPQC i a combination of DR connected in erie by an injection tranformer and DSTATCOM connected in hunt between the ource and load. The propoed controller for UPQC i capable of maintainin the total harmonic ditortion (THD %) of voltae and current within the IEEE limit and load voltae i maintained at 1 p.u. even under ditorted rid condition like a, well ad harmonic condition. Similarly, the ource current i maintained balanced and inuoidal even under unbalance and harmonic load. The propoed control alorithm ha peak amplitude extraction for both voltae and current and unit template eneration uin Dual SOSOGI PLL. Linear / Non Linear Load PCC C B A Lc Lc Lc A B C DSTATCOM Cdc DR Injectin Tranformer A Fiure 1: UPQC Confiuration. B C Line Impedance Sabc Second Order Generalized Interator + Σ K Σ X ʃ β ʃ ^ W Fiure : Second Order Generalized Interator Two ine wave X α and are produced with a phae difference of 9 a hown in fi. The SOGI i alo called a adaptive filter with an infinite ain and i defined a: SOGI( ) W ˆ (1) ˆ W The tranfer function baed on cloedloop hown in fi. are decribed a follow: G G kw ˆ ˆ ˆ kw W kwˆ kw ˆ Wˆ In eneral, SOGIQSG ue a tandard DC Interator and it i replaced by eneralized interator to form SOSOGI PLL ued for etimation of inuoidal inal and thu formed a a fourthorder function a hown in Fi.3. α Σ K 1 Σ X ʃ Σ K Σ X ʃ + + W^ W^ X SecondOrder SOGI (SOSOGI) ʃ Fiure 3: SOSOGIQuadrature Sinal Generation (QSG) Then, the openloop tranfer function can be expreed a: G( ) ( ˆ K1KW ˆ ˆ K W W )( β Wˆ ) X ʃ (3) α () The cloed loop tranfer function baed on SOSOGI i A. SOSOGIPLL The eneralized block diaram of SOGI baed PLL i hown in Fi.. The k hown in fi. i called a dampin factor that affect the bandwidth of the cloedloop ytem. The repone and level of filterin i decided by the dampin factor k. expreed a: ' G ( ˆ K1KW ˆ ˆ K W W )( Wˆ ) ( ˆ K K W 1 ) 49

3 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp ' G ( ˆ 3 K1KW ˆ ˆ )( ˆ ) ( ˆ K W W W K K W Park tranformation i ued to convert αβ to dq. co ˆ in ˆ T (4) in ˆ co ˆ The tranformation output d i ued to eliminate hih frequency noie by pain it throuh a Loop Filter (LF) and the etimated phae anle ˆ i enerated by addin fundamental frequency (W). SOGI baed QSG i replaced by SOSOGI for better etimation under harmonic and inter harmonic condition includin DC offet a hown in Fi.3. Dual SOSOGIPLL W abc Σ 1/ SOSOGI αβ α β LF Σ ʃ abc d Δw dq W ^ αβ Σ 1/ SOSOGI β α Manitude rm 1 Loop Filter and CO Fiure 4: Dual SOSOGI Baed PLL Fi.4 how the block diaram of threephae Dual SOSOGI baed PLL for phae anle etimation under all teady tate and dynamic condition. Proper tunin of K 1 and K are required in uch a way that the filterin repone hould be effective under ditorted condition. Where, K 1 and K are called Dampin Factor and choen a 1 and 1.6. In order to extract exact manitude of in phae and quadrature output, the input nominal frequency mut be equal to the frequency etimated by the SOSOGIPLL. The entire dein procedure of SOSOGIPLL i clearly explained by Xin et al. [14] The ain K 1 and K can be computed a follow: 1 K W /( W ) (5) K (4 W ) / W (6) Where, W = UnDamped Natural Anular Frequency θ PLL ) peak current. Thee two filter are alo eliminated becaue of uin SOSOGIPLL for etimation. B. Etimation of Unit Template A cloed loop block diaram of threephae Dual SOSOGI PLL i hown in Fi.4. The propoed PLL i ued for eneration of unit template baed ource voltae ( abc) inal and peak manitude etimation baed on load current (I Labc) a hown in Fi.5. The output phae anle (U a=sin (θ a), U b=sin (θ b), U c=sin (θ c)) that are enerated from the Dual SOSOGIPLL are conidered a unit template. The phae anle enerated by the PLL i converted to ine anle which act a unit template (U PLL) of a, b, c phae repectively. C. Reference Source Current Generation The peak amplitude of active component of current i calculated imilarly a hown in fi. 3. I Labc i upplied to SO SOGI baed quadrature inal eneration for etimation of peak load current. The voltae ( dc) acro the DC bu capacitor i compared with the dc * (reference DC bu voltae) and the error inal i paed throuh a Proportional Interal Controller to reulate the DC bu voltae [15]. The error of the inal i iven by: loop(n)= * dcref(n) dc(n) (7) The error i then upplied to PI controller to reulate the voltae of DC bu of DSTATCOM. The output of the PI controller i iven by: I cd(n)=i cd(n1)+k p{ loop(n)}+k i dcer(n) (8) Where, k p and k i are ain of PI controller. The averae manitude of current (I p) and the output of the PI controller (I cd) are ummed up (I P=I p + I cd). Finally, the reultant active component of current i multiplied with the unit template (U a, U b, U c) that are enerated by the rid voltae to enerate three reference ource current. Thee three etimated threephae reference ource current (i* a, i* b, i* c) are compared with the ource current ened at the point of common couplin (i a, i b, i c) to etimate the error in current. The error current enerated are upplied to a PWM controller to enerate PWM atin pule for DSTATCOM a hown in Fi. 5. W = Input Sinuoidal Frequency = Dampin Factor In eneral, two lowpa filter are ued to eliminate the ripple produced acro the DC link voltae and at etimatin the 491

4 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp dc * dc Σ I Labc Sabc PI Dual SOSOGI QSG DUAL SO SOGI PLL I cd Σ I p U abc X Gate pule I* for Sabc PWM DSTATCOM Σ GENERATOR I Sabc Ma Σ Labc Gate pule PWM for DR GENERATOR Fiure 5: Control Block Diaram of the Propoed UPQC Sytem D. Reference Load oltae Generation The peak value amplitude of reference load voltae i enerated by uin unit template (U PLL) enerated by Threephae Dual SOSOGIPLL. Thee reference unit vector template are ued to produce reference load voltae by multiplyin the manitude of load voltae with the unit template. The reference voltae i then compared with the ened load voltae and the error i fed to the PWM controller to enerate atin pule to the DR a hown in fi. 5. SIMULATION RESULTS AND DISCUSSION In thi ection, A ThreePhae Dual SOSOGI baed PLL wa propoed in the control alorithm for reference voltae and current eneration and evaluated uin MATLAB / Simulink on a Threephae ditribution ytem. Fixed time tep of µ with ode1 (Euler) olver i choen for imulation. Source oltae ( Sabc), Load oltae ( Labc), Injected oltae ( inj), Unit Template (U abc), Source Current (I Sabc), Load Current (I Labc), Injected Current (I inj) and DC link oltae ( dc) are oberved. ariou tet cae are choen in the imulation to tet the performance of UPQC with the propoed Dual SOSOGI control alorithm. The ource current i maintained inuoidal and load voltae i balanced in all varyin and ditorted condition that prove the effectivene of the controller. 35 Source oltae () Load oltae () Injected oltae () DC Link oltae () Fiure 7: Performance of UPQC under Unbalanced Linear/Nonlinear Load. 49

5 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp Source oltae () Load oltae () Injected oltae () DC Link oltae () Fiure 8: Performance of UPQC with Increae in Nonlinear Load. 35 Source oltae () Load oltae () Injected oltae () DC Link oltae () Fiure 9: Performance of UPQC under Balanced oltae Sa (3%). 493

6 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp Source oltae () Load oltae () Injected oltae () DC Link oltae () Fiure 1: Performance of UPQC with Unbalance in Grid oltae. 35 Source oltae () Load oltae () Injected oltae () DC Link oltae () Fiure 11: Performance of UPQC under Grid oltae Harmonic (5 th & 7 th ). 494

7 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp Source oltae () Load oltae () Injected oltae () DC Link oltae () Fiure 1: Performance of UPQC with DC Offet (1%) in Grid oltae. CONCLUSION A imple control alorithm with dual econdorder SOGI baed PLL for three phae UPQC ha been teted and validated uin MATLAB / Simulink. Thi theory i adopted to work in inuoidal and noninuoidal rid voltae uch a balanced and unbalanced a, harmonic and load condition uch a unbalance, harmonic and increae in load. The ource current i maintained within IEEE limit. The control alorithm i very effective and eay to implement becaue of imple equation involved in it compared to thoe propoed in the literature. SOSOGI PLL ha proved it efficiency under all advere condition with it imple tructure and accuracy. The ource and load balancin, reactive current and harmonic compenation i effectively done under teadytate and dynamic condition prove the controller performance. REFERENCES [1] F. F. Ewald and A. S.M.Mohammad, Power Quality in Power Sytem and Electrical Machine. London, U.K.: Elevier Academic Pre, 8. [] Gz. Arindam and L. Gerard, Power Quality Enhancement uin Cutom Power Device, Spriner International Edition ed. Delhi, India: priner, 9. [3] C. Sankaran, Power Quality. Boca Raton, FL: CRC, 1. [4] IEEE Recommended Practice and requirement for Harmonic Control on electric power Sytem, IEEE Standard 519, 199. [5] Bollen. M. Undertandin power quality problem voltae a and interruption (IEEE Pre, Picataway, NJ, 1999). [6] Baini A. Handbook of power quality (John Wiley & Son Ltd, 8). [7] T. Devaraju,. C. eera Reddy, and M. ijaya Kumar, Role of cutom power device in power quality enhancement: a review, International Journalof Enineerin Scienceand Technoloy, ol., No. 8, pp , 1 [8] J.S. Hul, Intantaneou phaor method for obtainin intantaneou balanced fundamental component for power quality control and continuou dianotic, IEEE Tran. Power Del., vol. 13, no. 4, pp , Oct [9] H. Akai et al., Intantaneou reactive power compenator compriin witchin device without enery torae component, IEEE Tran. Ind. Appl., vol. IA, no. 3, pp , May/Jun

8 International Journal of Applied Enineerin Reearch ISSN olume 1, Number 1 (17) pp [1] Yah pal, A.Swarup, Bhim Sinh., Comparion of three control alorithm for SinlePhae UPQC in Proc. 11 International conference on Enery, Automation and Sinal, Dec, 11. [11]. Kaura and. Blako, Operation of a phae locked loop ytem under ditorted utility condition Indutry Application, IEEE Tranaction on, vol. 33, no. 1, pp. 5863, [1] Maoud KarimiGhartemani, A Unifyin Approach to SinlePhae Synchronou Reference Frame PLL, IEEE Tran. Power Electron., 13, 8, (1), pp eneralized interator in Proc.37th IEEE PESC, Jun. 6. [14] Z Xin, X Wan, Z Qin, P C Loh, F. Blaabjer, An Improved SecondOrder Generalized Interator Baed Quadrature Sinal Generator, IEEE Tran. Power Electron., vol. 7, no. 1, pp , Jan. 1. [15] Yada, Hareeh Kumar, and M. S. R. Murthy. A new topoloy and control tratey for extraction of reference current uin inle phae SOGIPLL for threephae fourwire Shunt Active Power Filter, 14 IEEE International Conference on Power Electronic Drive and Enery Sytem (PEDES), 14. [13] M. Ciobotaru, R. Teoderecu, and F. Blaabjer, A new inlephae PLL tructure baed on econd order APPENDIX AC Supply Source & Frequency ThreePhae, 415, 5Hz Source Impedance R=.5 Ω, L =.5mH NonLinear Load R L=4 Ω, L=.6H Ratin of Tranformer 5 KA, 1:1 ratio Switchin frequency 8kHz Reference dc bu voltae 8 Interfacin inductor L=3.5mH Gain of PI controller for dc bu K p =.4, K i=6 Gain of SOSOGI K 1=1, K =1.6 Gain of PI controller for SOSOGIPLL K p =67.5, K i=1 THD (%) of Tet Cae (TableI) Fi No. a La Ia ILa