POWER QUALITY IMPROVEMENT IN MATRIX CONVERTER
POWER QUALITY IMPROVEMENT IN MATRIX CONVERTERUSING HYBRID FILTERRASHMI S. PHASATE1 & ARCHANA BAWANKAR21,2Department of Electrical Engineering , G. H. Raisoni College of Engineering, Nagpur, IndiaE-mail : rashmi.phasate@yahoo.com, archana bawankar@yahoo.comAbstract- This paper proposes a hybrid filter to minimize the power quality impact of matrix converters. Matrix convertersinject significant harmonics and nonstandard frequency components into power systems. The hybrid filter is used to reducethe harmonics. A hybrid filter constructed of a shunt active filter and distributed passive filters used for power qualityimprovement. The proposed approach has been tested and validated on the matrix converter using Matlab/Simulink. Thecomparison of Simulation results for passive and active filter separately used with matrix converter with the result of matrixconverter with hybrid filter is shown to demonstrate the advantages of the proposed scheme.Keywords - Matrixconverter, Hybrid filter, Power quality, Current harmonics.I. INTRODUCTIONThere are many nonlinear loads drawing nonsinusoidal currents from electrical power systems.These non sinusoidal currents pass through differentimpedances in the power systems and producevoltage harmonics. These voltage harmonicspropagate in power systems and affect all of thepower system components. The important harmonicsource is ac/dc converters/inverters. The matrixconverter is one of the harmonic source. Due to thediscontinuous input currents, the matrix converterbehaves as a source of current harmonics, which areinjected back into the AC mains. Since these currentharmonics results in voltage distortions that affect theoverall operation of the AC system, they have to bereduced. Therefore, it is necessary to use effectivepower quality improvement facilities for improvingthe power quality of the matrix converter. Usage ofpassive or active filters can be a successful procedurein limitation or removal of harmonics. But because ofdynamic loads, using passive filters alone cannotcompensate the harmonics greatly also it might causeresonances in the system so they cannot be effectiveregardless of their low costs. Using active filtersalone with the ability for removing system currentharmonics of dynamic loads can increase the costs ofthe project for high rating of active filters. Therefore,usage of hybrid filters would be the best solution forpower quality improvement because the problems ofusing passive or active filters alone will not be anyproblem in such a structure, also the advantages ofboth of these filters can be gained together In thispaper power quality problems of matrix converter areintroduced and the necessity of using hybrid filtersinstead of active or passive filters alone are discussed.A matrix converter with hybrid filter is simulatedwith MATLAB software. The simulation is done forthe matrix converter without any filters, with usage ofpassive filter or active filters and the hybrid filterseparately. Comparison of the waveforms of thesystem current in time domain, proves that theeffective power quality improvement of the matrixconverter can be done by using the hybrid filter.II. MATRIX CONVERTERThe matrix converter with 3Ø to 3Ø configuration isone of the possible direct AC-AC convertertopology[Tenti ect 1992].It is introduced byVentorini in 1980.Matrix converter has severaladvantages over traditional rectifier-inverter typepower frequency converters. It provides sinusoidalinput and output waveforms. It has inherent bidirectional energy flow capability and the inputpower factor can be fully controlled. Last but notleast, it has minimal energy storage requirements,which allows to get rid of bulky and lifetime- limitedenergy-storing capacitors. In spite of the advantages,the matrix converter has also some disadvantages. Ithas a maximum input output voltage transfer ratiolimited to 87 % for sinusoidal input and outputwaveforms. It requires more semiconductor devicesthan a conventional AC-AC indirect power frequencyconverter, since no monolithic bi-directional switchesexist and consequently discrete unidirectionaldevices, variously arranged, have to be used for eachbi-directional switch. It is Sensitive to thedisturbances of the input voltage system. But it ni.ect1978].A hybrid filter constructed of passive filters and anactive filter used for power quality improvement inmatrix converter is presented and the parameters ofthe passive filters and the active filter are discussed.The matrix converter consists of 9 bi-directionalswitches that allow any output phase to be connectedto any input phase. The general architecture of theInternational Journal of Power System Operation and Energy Management ISSN (PRINT): 2231 – 4407, Volume-2, Issue-1,29
Power Quality Improvement in Matrix Converter Using Hybrid Filtermatrix converter is shown in Figure 1.Nine bidirectional switches in the matrix converter cantheoretically assume 512 (29) different switchingstates combinations. But not all of them can beusefully employed. Regardless to the control methodused, the choice of the matrix converter switchingstates combinations (from now on simply matrixconverter configurations) to be used must complywith two basic rules. Taking into account that theconverter is supplied by a voltage source and usuallyfeeds an inductive load, the input phases should neverbe short-circuited and the output currents should notbe interrupted. From a practical point of view theserules imply that one and only one bi-directionalswitch per output phase must be switched on at anyinstant. By this constraint, in a three to three phasematrix converter only 27switching combinations arepermitted[1].Type of Harmonic Sources. Power electronicsconverters are a common and typical source ofharmonic currents. The distortion of the currentwaveform, i.e., the generation of harmonics, resultsfrom the switching operation. Because of theharmonic current contents and characteristic are lessdependent upon the AC side, this type of harmonicsource behaves like a current source. Therefore, theyare called current-source type of harmonic source (orharmonic current source) and represented as a currentsource. A shunt active filter is to be placed in parallelwith a load (matrix converter) to detect the harmoniccurrent of the load and to inject a harmonic currentwith the same amplitude of that of the load into theAC system. A shunt active filter senses the loadcurrent and injects a current into the system tocompensate current harmonics or reactive load. Inthis paper a shunt filter was used to compensate thecurrent harmonics of matrix converter, here the shuntactive filter acts as a current source. The sum of itscurrent and load current is the total current that flowsthrough the source. Therefore, controlling the outputcurrent of the active filter can control the sourcecurrent. High ratings of theses filters lead to anincrease in the costs.HYBRID FILTERHybrid filters constructed of active and passive filterswith different structures are used for removing thedisadvantages of passive filters such as probability ofresonances and non dynamic responses and also highcosts of active filters, while using both the advantages ofboth of them with lower costs. Different structures ofhybrid filters can be utilized in power systems such asshunt passive filter and series active power filter withnonlinear loads, shunt active and passive filter withnonlinear load, series active and passive filter parallelwith nonlinear load, etc. shown in Figure.Fig. 1: General Architecture of Matrix ConverterIII. FILTER STRUCTURE PASSIVE FILTERPassive filters as classic methods for power qualityimprovement in ac of ac system consist of series LCtuned for removing a specific or harmonic or blockinga bandwidth of severe harmonics of nonlinear linearloads current. These filters have low impedances forthe tuned tuned frequencies such as 5th and 7th and forthese frequencies, the lower impedance of the filter incomparison with system, the better better filteringcharacteristics of passive filter. Low cost is a greatbenefit of these filters but because of their LC constantparameter, they cannot be efficient power qualityimprovement facilities for dynamic nonlinear loads.Another problem of installation of passive filters isprobable resonances between the impedance of passivefilter and the system resulting in increasing theharmonics and lower power quality of the acsystem[2].ACTIVE FILTERThe most popular type of active filters is the shuntactive filter. Shunt active filters can be single-phaseor three-phase, voltage source or current source.When the filter is used to compensate the currentharmonics produced by the matrix converter, anactive filter compensates the harmonic current of amatrix converter. Shunt active filters are used tocompensate current harmonics of nonlinear loads toperform reactive power compensation and to balanceimbalance currents. The matrix converter isconsidered as one type of load i.e. Current-SourceInternational Journal of Power System Operation and Energy Management ISSN (PRINT): 2231 – 4407, Volume-2, Issue-1,210
Power Quality Improvement in Matrix Converter Using Hybrid FilterIf the active filter is not connected, the compensationcurrent Ic mitigates the main harmonics of loadcurrent Il and it is possible that a series resonancebetween the source impedance and the LC brancheswill appear.So the source current Is will include certainharmonics and the distortion is not completelyreduced. If the active filter is included an appropriatecontrol allows to modify the impedance of shuntcompensator at the resonance frequencies, and theproblem can be avoided.V. HYBRID FILTER DESIGNThe hybrid filter design depends on the load to becompensated. It must contain some passive LCbranches one for each important load currentharmonic to be removed from the source current. Inthe case of many typical loads, it is usually enough toemploy one, two or three branches for the mainharmonics. By three-phase systems it is possible toreduce or eliminate the 3rd harmonic order and itsmultiples by suitable connections of the transformerssupplying the power to the load. Therefore it is usualto include LC branches tuned for the 5th and 7thharmonic order.The values of Ln and Cn parameter of a branch tunedfor an “n” order harmonic must satisfy the equation.Fig. 2: Different structures of hybrid filters in power systemωn 2πfn 1/ Ln CnIV.THEPROPOSEDCOMPENSATIONSCHEME FOR MATRIX CONVERTERThe objective of this work is to design a shunt hybridpassive-active filter to eliminate the load harmonics.The passive filter is connected in parallel with theload. It includes some LC branches that offer nullimpedance to the main current harmonics. The APFis connected in series with the passive filter. Thescheme of the compensated system is presented infigure 3 given below. Figure 3 shows a three phasediagram of proposed shunt hybrid filter. Two passivebranches are connected in series with an active filterwith the help of three phase transformer.Where f corresponds to the fundamental frequency,that was taken as 50 Hz in this work. The active filterconnected in series with the passive branches can beseen as a controlled voltage source.Different strategies are possible to control thiscompensation voltage. In single-phase or balancedthree-phase system, a voltage vc proportional to sourceharmonic current ISH permits to modify the impedanceof the shunt compensator, and the passive filterperformance is improved. Figure 2a shows theequivalent single-phase circuit for the compensatedsystem. The non-linear load is modeled by a currentsource. For a determined harmonic of order H, theequivalent circuit is shown in figure From the circuit2b, it is possible to obtain the source harmoniccurrent, equation 2.ISH ZF / ( ZF ZS K) ILH 1/ ( ZF ZS K) VSHWhere, Zf – impedance of filter and Zs – sourceimpedance Ideally, the source harmonic currents willbe null if K . If K (Zs Zf) this strategy allowsto reduce series resonance between the source and thefilter. It avoids that the passive filter receives theharmonic current of the rest of the system. In thepractical case simulated in this work a value K 2 isused.Fig. 3: Three phase system compensated with hybrid filterInternational Journal of Power System Operation and Energy Management ISSN (PRINT): 2231 – 4407, Volume-2, Issue-1,211
Power Quality Improvement in Matrix Converter Using Hybrid Filter0.250.20.150.10.050-0.05-0.1-0.15-0.200. 0050. 010.0150.020. 025Time0. 030.0350.040.0450. 05Fig. (a) Matrix Converter without filter30(a)20Is100-10-20-3000. 0050.010.0150. 020. 025Time0. 030. 0350. 040.0450. 05Fig. (b) Matrix Converter with passive filter60(b)50Fig. 4: (a)Equivalent circuit of the compensated systemb)Equivalent circuit for harmonic of order HIs403020The output voltage of active power converter includesno desired high frequency harmonics caused by theswitching devices operation. It is necessary to carryout a passive filtering. The series connection with theLC branches is carried out by means of a transformer.This allows to have low voltage values at the dc sideof the inverter.10000.0050.010.0150.020. 025Time0. 030.0350. 040. 0450. 05Fig. (c) Matrix Converter with active filter60504030VI. SIMULATION RESULTS20In this work three phase matrix converter has beencompensated to check the hybrid filter performance.The source voltage is 440Vrms, 50Hz. Table 1 showsthe compensated system main parameters. It includessource impedance parameters L and C values forpassive branches used. The system has beensimulated with passive filter, active filter and thehybrid filter separately. Table 1 shows thecompensation system main parameter values. insimulation studies, the results are specified before andafter applying the passive, active and hybrid filter tothe matrix 0350.040.0450.05Fig. (d) Matrix Converter with hybrid filterVoltageVsabc440VrmsFrequencyF50HzLLabc1mHRL2 ohmVII. µFIn this paper a hybrid filter was used for power qualityimprovement in the matrix converter. The hybrid filteris constructed of a passive filter and a shunt activeParametersLoad0-10Fig. 5: Source current waveforms in time domain forthe system In figure a above, the source currentwaveforms for the matrix converter without applyingany filter is shown. In the simulation the input currentwave shape is non-sinusoidal and it containsharmonics. The simulation time is up to 0.05sec. Infigure b, the matrix converter is operated by applyingsecond order LC filter. the values for inductor andcapacitor are shown in table 1. In figure c, the matrixconverter is operated by applying a shunt active filter.The source current waveform is improved as comparedto the passive filter. In figure c, the matrix converter isoperated by applying a hybrid filter. The sourcecurrent waveform is improved as compared to thepassive filter and active filter. In this figure the sourcecurrent waveform is almost sinusoidal.Table 1: Simulation ParametersSource103phase lineinductance3phase loadresistanceValueInternational Journal of Power System Operation and Energy Management ISSN (PRINT): 2231 – 4407, Volume-2, Issue-1,212
Power Quality Improvement in Matrix Converter Using Hybrid Filter[10] Ahmet Altintas , “A new method for power qualityimprovement in classical AC/AC voltage controllers usingPWM technique” Scientific Research and Essays Vol. 5(10),pp. 1075-1083, 18 May, 2010.filter in series with it. This hybrid filter is connected inparallel with non linear load. The harmonic contents ofthe source current due to the nonlinear load isremoved by the use of passive filter, active filter andthe hybrid filter. Studying and comparing thewaveforms of the source current, without any filter,with only passive filter, with only shunt active filterand with the hybrid filter it is found that the hybridfilter is better solution for the harmonic reduction inthe matrix converter.[11] P. Ferracci, “ Power Quality”, Schneider Electric CahierTechniqu no.199, September 2000.[12] Cyril W. Lander, “ Power Electronics” Third Ed. McGrawHill International Editions.[13] ications”, Prentice Hall of India Private Ltd.and[14] H.Akagi, “ Modern active filters and traditional passivefilters”, Bulletin of the Polish Academy of Sciences,Technical Sciences,Vol. 54, No. 3, 2006.REFERENCES[1]JenoPaul P, Ruban Deva Prakash T, Jacob Raglend I,“Adapitive PLL controller based shunt active filter for powerquality improvement in Matrix converter” InternationalJournal of Applied Engineering Research, dindigul volume1,no 4,2011.[2]Farhad Shahnia, Seyed Hossein Hosseini, “Power QualityImprovement of PV Power Generation Systems Using HybridFilter”[3]Jusus R. Vazquez, Juan L. Flores, Patricio Salmeron,Salvador P. Litran, “A hybrid approach to compensate nonlinear loads in electric power system[4]Kennedy, Barry ,“ Power Quality Primer” Electricalengineering Primer Series, McGraw-Hill USA,1 Mar 2000[5]Tenti P., Malesani L., Rossetto L., “Optimum control of N –input K-output matrix converter” IEEE transaction on powerelectronics,7(4),pp. 707-713,1992[6]Huber L., Borojevic D., “Input filter design of 359,1991[15] Mr H. Bouchikha, M. Ghers, “Three phase shunt hybridfilters for the current harmonics suppression and the reactivepower compensation”,European Journal of ScientificResearch ISSN 1450-216X Vol.24 No.4(2008),pp.580-590[16] Antonio Martins 1, Jose Ferreira 2, Helder Azevedo 3,“Active Power Filter for Harmonic Ellimination and PowerQuality Improvement”[17] O.Ucak, I. Kocabas, A. Terciyanli, “ Design andImplimentation of a Shunt Active Power Filter with ReducedDC Link Voltage”[18] G. Bhuvaneswari, Manjula G. Nair, “Three phase hybridshunt filters for Power Quality Improvement”, Journal ofPower Electronics, Vol.7, No.3, July 2007.[19] Ali Zafari 1, Shahaboddin Shamshirband 2, “Simulation andanalysis of the harmonic[20] behavior of matrix converters as compared with conventionalconverters”, International Journal of the Physical SciencesVol. 6(12), pp. 2818-2825, 18 June, 2011[21] R. D. Patidar, S. P. Singh, “A Single Phase Hybrid Filter toImprove Power Quality”, XXXII National SystemsConference, NSC 2008,December 17-19,2008[7]Gonzalo Sandoval, John Houdek, “A Review of HarmonicMitigation Techniques”.[8]A. de Almeida, L. Moreira. J. Delgado,“Power QualityProblems and New Solutions” ISR – Department of Electricaland Computer Engineering University of Coimbra, Pólo II[22] Darwin Rivas, Luis Morán, Juan W. Dixon, José R. Espinoza,“Improving Passive Filter Compensation Performance WithActive Techniques”, IEEE Transactions On IndustrialElectronics, Vol.50, No.1, February 2003[9]P.Gani Raju, Veda Kumar.N, “Power Quality Improvementin DC Drives Using Matlab/Simulink” International Journalof Wisdom Based Computing, Vol. 1 (2), August 2011.[23] Wheeler P.W., Zhang H. And Grant D.A., “A theretical andpractical investigation of switching frequency harmonics in amatrix converter”,Proceedings of UPEC’93,pp.502-505,1993. International Journal of Power System Operation and Energy Management ISSN (PRINT): 2231 – 4407, Volume-2, Issue-1,213
effective power quality improvement of the matrix converter can be done by using the hybrid filter. II. MATRIX CONVERTER The matrix converter with 3Ø to 3Ø configuration is one of the possible direct AC-AC converter topology[Tenti ect 1992].It is introduced
CONTENTS CONTENTS Notation and Nomenclature A Matrix A ij Matrix indexed for some purpose A i Matrix indexed for some purpose Aij Matrix indexed for some purpose An Matrix indexed for some purpose or The n.th power of a square matrix A 1 The inverse matrix of the matrix A A The pseudo inverse matrix of the matrix A (see Sec. 3.6) A1 2 The square root of a matrix (if unique), not elementwise
A Matrix A ij Matrix indexed for some purpose A i Matrix indexed for some purpose Aij Matrix indexed for some purpose An Matrix indexed for some purpose or The n.th power of a square matrix A 1 The inverse matrix of the matrix A A The pseudo inverse matrix of the matrix A (see Sec. 3.6) A1/2 The square root of a matrix (if unique), not .
CONTENTS CONTENTS Notation and Nomenclature A Matrix Aij Matrix indexed for some purpose Ai Matrix indexed for some purpose Aij Matrix indexed for some purpose An Matrix indexed for some purpose or The n.th power of a square matrix A 1 The inverse matrix of the matrix A A The pseudo inverse matrix of the matrix A (see Sec. 3.6) A1/2 The square root of a matrix (if unique), not elementwise
CONTENTS CONTENTS Notation and Nomenclature A Matrix A ij Matrix indexed for some purpose A i Matrix indexed for some purpose Aij Matrix indexed for some purpose An Matrix indexed for some purpose or The n.th power of a square matrix A 1 The inverse matrix of the matrix A A The pseudo inverse matrix of the matrix A (see Sec. 3.6) A1 2 The sq
Further Maths Matrix Summary 1 Further Maths Matrix Summary A matrix is a rectangular array of numbers arranged in rows and columns. The numbers in a matrix are called the elements of the matrix. The order of a matrix is the number of rows and columns in the matrix. Example 1 [is a ] 3 by 2 or matrix as it has 3 rows and 2 columns. Matrices are .
quality improvement essentials—critical elements successful quality improvement programs have in common. This executive report defines quality improvement in healthcare, describes critical quality improvement considerations, components, and tools, and identifies the top five quality improvement essentials: 1.
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