An Improved Active Filter Technique for Power Quality Control under Unbalanced Dynamic Load Condition

Transcription

1 Amercan Journal of Engneerng Research (AJER) e-issn: -847 p-issn : -96 Volume-5, Issue-, pp Research Paper Open Access An Improved Actve Flter Technque for Power Qualty Control under Unbalanced Dynamc Load Condton Vsvanathan Kalaah (Department of Electrcal and Electroncs Engneerng/ ADVETI, UAE) ABSTRACT: Ths paper presented an mproved approach for actve flterng topology usng smplfed multlevel nverter. The modfed phase opposton dsposton (MPOD) scheme s presented on smplfed multlevel nverter. The multlevel nverter obtaned 9 level njectng power usng actve power swtches. The Modfed POD scheme has a sngle carrer and mult-reference sgnal for PWM mplementaton for presented actve flter topology. The enhanced reference frame method s used n PWM generaton so that t s not requred auxlary elements for mprovng power qualty and elmnatng the hgher order harmoncs. The enhancement of ths scheme s obvously verfed under unbalancng load and dynamc load condtons. The comparson wth fve level njected schemes, the present scheme has better result n the form of harmoncs elmnaton, power factor mprovement and reactve power compensaton. Keywords: Mat lab, MRFC, PFC, PWM, THD I. INTRODUCTION The study and focusng of power qualty s an mportant ngredent n electrcal feld to mantanng and mprovng the power qualty. The power converter has provdes a crucal role for focusng n power qualty. The power converter s bascally has a non-lnear property and t s drawn a saturated power n nput supply and load []. Power converter njects lne across the pont of common couplng (PCC) n between supply to load. The classcal approach for power qualty mprovement or power qualty standard are the passve elements such as capactor, nductor. Classcal scheme has bad mark on bulky n sze, fxed soluton for compensaton, resonance problem and electromagnetc ntruson []. The actve power flter s an advanced technque for mprovng power qualty or mantanng the power qualty as per the standard lmts []. The multlevel nverter s recently developed for medum to hgh power applcaton under power qualty standard. Multlevel nverter topology Appled n electrcal drves control and reactve power elmnaton. The multlevel nverter stands for low power ratng of power swtches and passve elements, suppressng Total Harmoncs Dstorton (THD) across the load. The Pulse Wdth Modulaton (PWM) generaton and mplementaton s for multlevel nverter. Ths PWM mplementaton s because of resolvng semconductor or power swtch lmtaton [4],[5]. The enhancement of multlevel nverter has reaches the necesstes such as generate a pure angle of snusodal njected voltage and low Total Harmoncs Dstorton (THD) of load current by present nverter. The classcal approach of three-level and fve-level nverter cascaded and flyng capactor type and t has requred excessve flters and excessve ranges for meet out necesstes. So lower frequency and lower ratng of power swtches used n enhancement of present smplfed multlevel nverter based actve flter topology shown n Fg.. The present scheme has low power losses, capable of reactve power elmnaton, power factor correcton by smplfed structure and modfed phase opposton and dsposton scheme. The present scheme s appled under non-lnear load, dynamc load and unbalancng load condtons and verfed by usng smulaton results. w w w. a j e r. o r g Page 97

2 Fg.. The basc confguraton of Actve flter topology II. THEBASIC CONFIGURATION OF ACTIVE FILTER The actve flter s njectng current n quadrature form and opposte to harmoncs across the pont of common couplng. The njected current from actve flter called compensaton current. The harmoncs generaton and reactance s generated by non-lnear, unbalancng and dynamc load condtons. So pulse wdth modulaton based power converter s appled as actve flter topology whch s shown n Fg.. The basc nature of multlevel nverter s not requres a couplng transformer and njected excessve passve elements. The modfed phase opposton and dsposton s used n present actve flter topology for controllng current and harmoncs suppresson shown n Fg.. III. THE ACTIVE POWER FILTER TOPOLOGY USING SIMPLIFIED MULTILEVEL INVERTER IV. THE ACTIVE POWER FILTER TOPOLOGY USING SIMPLIFIED MULTILEVEL INVERTER. w w w. a j e r. o r g Page 98

3 . V. MODES OF OPERATION OF ACTIVE POWER CONVERTER The proposed PWM method has fve levels (,,,, ) as per to the swtchng mode of the nverter. There are four manners of workng submt the rapd value of reference and outsde value of the carrer sgnal. Inverter output voltage drawn through operatng ranges shown n Table II. The Novel pulse wdth modulaton approach based on pod (phase opposton and dsposton) modulaton requres only a sngle carrer ( ). It s proposed the detaled PWM strategy s represented n fg. If the reference sgnal s postve, then the swtch par (, ) are turn on, and f reference s negatve, then the swtchng pars (, ) are turn on. w w w. a j e r. o r g Page 99

4 Fg.. PWM strategy based on MPOD wth sngle carrer sgnal Thus the swtches composng the H brdge nverter turned on and turn off once durng the perod of the reference sgnal. The voltage across the swtch at blockng state s.the swtches (, ) are operated complmentary to the swtches (, ).The PWM sgnal generates for proposed module can be explaned as follows: Mode : A sgnal wthholds from the reference sgnal by s compared wth the carrer sgnal. If - > then all swtches or are turned on. If - <, then the swtch or s turn off alternately and current flow through Dodes (,, )and are ON.then,, are OFF. Chargng and dschargng of Inductors (,,,, ) contnuously. Capactor start to charge ( and ). Mode : the reference sgnal s drectly compared wth a carrer sgnal. If > then the swtch or s turned on alternately. If then all swtches and are turned off. Then, and and are ON. Then,, are OFF.,,, s charged by Supply and are contnuous to charge. Mode : drectly compared wth a carrer sgnal. If > then the swtch or s turned on alternately. If < then all swtches and are turned off. Then,,, and are ON. Then,, are OFF.,,, s charged by and. Mode 4: a sgnal subtracted from by s compare wth carrer sgnal. If - > then all swtches and are turned on. If - < then the swtch or s turned off alternately.,,, and are ON. Then,, are OFF.,,, s charged by and. TABLE II: Operatng mode of proposed MLI w w w. a j e r. o r g Page

5 VI. CONTROL STRATEGY The man am of the control strategy s to mantan power qualty as n standard lmts. The system control s used to mantan desred range of power qualty under unbalanced dynamc load condton. The Actve Flter s compensatng reactance value but voltage rpple and current rpple s need to be reduce then easly power factor correcton s reduces. Therefore the APF needs very sensble controller and crcuts. a) Modfed Synchronous Reference Frame Control (MRFC) In tradtonal topology there are so many actve flterng methods such as reactve power control theory (p-q theory), unty power factor control, one cycle control and Fast Fourer Technque etc. the proposed scheme has used to extract the reference current generaton usng actve flterng [6].The presented modfed synchronous reference frame (MSRF) explan about harmoncs and extract the harmoncs component. The source current of and s detected and s transferred n to two-phase statonary frame from statonary reference frame. The detecton scheme has been made by the followng equaton a b c () The two phase statonary reference frame of and s transformed nto drect and quadrature axs frame by equaton (). The cosne and sne angle are generated usng phase lock loop (PLL) reference frame. d q cos sn sn cos The generaton of dq-currents obtaned by ncorporated of AC and DC parts. The fundamental component of fxed DC and AC parts represents the harmoncs component. The harmoncs or current transent can be easly extracted usng low pass flter shown n fg.4 () Fg.4 the block dagram for MSRF algorthm The drect axs current s obtaned from combnaton of actve fundamental current and load current harmoncs.the fundamental component s represents n synchronous reference frame. The drect axs component of harmoncs s obtaned by subtractng from t s presented n load. Quadrature axs harmoncs current obtaned by sum of reactve form of load current and load harmoncs. w w w. a j e r. o r g Page

6 The and reference frame s generated by followng equaton cos sn sn cos dh q () The reference current ca cb c * * * T abc T abc a *, *, b c * of are obtaned by the followng expresson (4) (5) b) Fuzzy logc controller scheme The effectve Actve Flter s adapted wth smplfed 9- level Inverter system. The basc nature of dynamc voltage restorer njects the reactance to suppress the reactve power whch s generated n load [7] and also observed harmoncs and current transent problem. The man demert of PI controller s ts ncompetence n precptate condtons of error sgnals,, because t can consder the value of sgnal alone except the change of rsng and fallng tme,.e dervatve error sgnal,. To solve power qualty problem, a smooth waveform s acheved usng proposed fuzzy logc scheme. The presented fuzzy logc scheme s based on Mamdan s system and t s used to mprove the fast transent performance n phase lock loop control crcut. The fast transent performance of fuzzy logc controller over PI controller s shown n Fg.5. The fuzzy control system as shown n Fg. 6 conssts of fuzzfcaton, defuzzfcaton and decson makng stage [8]. The proposed fuzzy logc controller appled n phase lock loop reference schemes for mprovng the angle control [9] and supplyng to effectve alpha, beta and d-q reference current generaton. The fuzzy based PLL provdes fast transent performance over the PI based PLL controller. The proposal of fuzzy logc scheme has the capablty to extract the harmoncs current from actual current sgnal and t s provded the sutable reference sgnal generaton for pulse generaton of actve dynamc voltage restorer. The modfed reference frame controller has provded satsfactory reference sgnal by crucal appearance of fuzzy logc PLL scheme and fuzzy rules s shown n Fg. 6. (a) (b) w w w. a j e r. o r g Page

7 Fg. 5 controller comparson performance: (a) fuzzy controller on APF. (b) PI controller on APF Fg. 6 Membershp functons of I/O fuzzy sets and control rules assgnment. VII. SIMULATION RESULTS AND DISCUSSION The enhancement of proposed scheme has ablty to control power qualty n the form of reactve power compensaton across load, mprovng the real power, Total Harmoncs Dstorton (THD) elmnaton and power factor correcton. The present mproved multlevel nverter topology based Actve flter s provded a maxmum level of harmoncs elmnaton over 5-level approach s shown n Fgure.7. The present system s analyss under Non-lnear and Dynamc load condton. The rpple power s dentfed and controlled by actve modfed reference frame controller. The controller s proved as a better and also promnent soluton for controllng rpple content present whch Non-Lnear and Dynamc load. The smulaton mplementaton and t s verfed by MATLAB/Smulnk software. The enhancement of modfed phase opposton and dsposton controller s mplemented usng mproved form of reference frame controller. Reference frame controller s played an mportant role n harmoncs reducton. MSRF va extractng rpple current and can Fg.7 smulaton crcut mplementaton of proposed scheme w w w. a j e r. o r g Page

8 Fg.8 Smplfed Multlevel Inverter Performance: (a) Per-Phase Inverter Voltage. (b) Three- Phase Multlevel Inverter voltage. The present multlevel nverter s obtaned Nne-Level voltage to reduce and mprovng the actve flter performance. The performance of per-phase voltage and Three-phase voltage s shown n Fgure.8. Testng of ths system s requred low ranges of passve elements and by the passve elements R-C crcuts used to draw the njected voltage whch s shown n Fgure. 9(a). The power qualty mproved performances are shown n Fgure from 9(b) to 9(d). The total harmoncs dstorton s obtaned and ths s proved as a better scheme over exstng Fve-level approach s shown n Fgure. and desred standard lmts []. By the way power factor correcton s reached.9. Fg.9 Power qualty performance of proposed system: (a) Injected Voltage. (b) Real Power (P). (c) Reactve Power (Q). (d) Power Factor Correcton w w w. a j e r. o r g Page 4

9 Mag (% of Fundamental) FFT wndow: of 5 cycles of selected sgnal Tme (s) Fundamental (5Hz) =.9, THD=.6% Harmonc order fg.. TotalHarmoncs Harmonc Dstorton (THD) usng FFT met REFERENCES [] Ran, K. Sebasth, and K. Porkumaran. "Multlevel shunt actve flter based on snusodal subtracton methods under dfferent load condtons." Computatonal Technologes n Electrcal and Electroncs Engneerng (SIBIRCON), IEEE Regon 8 Internatonal Conference on. IEEE,. [] B. Sngh. K. Al-Haddad and A. Chandra, A revew of actve flters for power qualty mprovement, IEEE Transactons on Industral Electroncs. Vol. 46. No. 5, pp , October 999. [] Zellouma, L., and S. Saad. "Three-Level Shunt Actve Flter Compensatng Harmoncs and Reactve Power."6. [4] B.-R. Ln, T.-Y. Yang, Three-level voltage-source nverter for shunt actve flter, IEE, Electrc Power Applcatons, pp , Nov.4. [5] B.-R. Ln, H. K. Chang, C.-H. Huang, Three-phase three-level actve power flter wth a clamped capactor topology, IEE, Electrc Power Applcatons, pp.5 5, July 6. [6] E. J. Acord, A. Goedtel. and L. C. B. Nascmento, A Study of Shunt Actve Power Flters Appled to Three-Phase Four-Wre Systems, ICREPQ - Span, 8 - March,. [7] Yu Jang, Hepng Lu, QunyngZheng, LanqngZheng A Novel Apparatus for Adjustng the Inserton Voltage of Transmsson Lne Based on Varable Inductors IEEE trans., on power delvery, Vol.7, Issue., Jan.. [8] AhmetTeke, LütfüSarbulut, and Mehmet Tümay A Novel Reference Sgnal Generaton Method for Power-Qualty Improvement of Unfed Power-Qualty Condtoner IEEE Transactons on Power Delvery, Vol. 6, No. 4, Oct. [9] Ahmad Osman Ibrahm, ThanhHa Nguyen, Dong-Choon Lee and Su-Chang Km A Fault Rde-Through Technque of DFIG Wnd Turbne Systems Usng Dynamc Voltage Restorers IEEE Trans., On Energy Converson, Vol. 6, No., Sept. [] Duffey, Chrstopher K., and Ray P. Stratford. "Update of harmonc standard IEEE-59: IEEE recommended practces and requrements for harmonc control n electrc power systems." Industry Applcatons, IEEE Transactons on 5.6 (989): 5-4. w w w. a j e r. o r g Page 5