Research On SVM Strategy For Matrix Converter And Its .
WSEAS TRANSACTIONS on CIRCUITS and SYSTEMSYongchao Chen, Zhenwei Liu, Yuwei Zou, Yanda LiResearch on SVM strategy for Matrix Converter and Its SimulationYONGCHAO CHEN1， ZHENWEI LIU2 ，YUWEI ZOU1 and YANDA LI11) College of Physics & Electrical EngineeringAnyang Normal University436，Xuange st., 455000, Anyang, HenanP.R. China2) Research and development departmentXu Ji Power Company LIMI TEDNorthern Part of Weiwu st., 461000, Xuchang, HenanP.R. ChinaRandy827@163.com, 13569051580@163.com，zyu.gg@163.com, liyd@aynu.edu.cnAbstract: - This paper presents double space vector modulation (SVM) strategy for three-phase to three-phasematrix converter and discusses the modeling method based on Matlab/ Simulink in detail. The process ofswitches conversion is analyzed and a novel modulation mode is proposed. Simulation waveforms arepresented which demonstrate the feasibility and validity of the proposed modulation mode. The methoddiscussed in this paper lays strong basis for its further researches and approaching to applications and it can bedirectly implemented to practical matrix converter system.Key-Words: - matrix converter, modulation, SVM, modeling, simulationstrong basis for its furtherapproaching to applications.1 IntroductionSince the matrix converter (MC) topology was firstproposed in 1976, people have obtained lots ofachievements with great efforts [1-5]. Comparedwith traditional converter, matrix converter is a kindof direct AC-AC power conversion without energystorage in dc-link. It has many advantages such asbidirectional energy flow, controllable input powerfactor and a compact power circuit design [6].The control strategy and modulation method arekey points, which directly determine theperformance of matrix converter. At present, theMatrix Converter control strategy can be generallycategorized into four classes including directtransformation method, hysteresis current method,two-voltage method and space vector modulationmethod. Among all strategies, SVM is the mostwidely used and investigated in recent years.Because the SVM strategy can not only control theoutput voltage and the input current respectively,but also modify the input power factor conveniently.In this paper, dual space vector modulation strategyfor three-phase to three-phase MC system isintroduced at first. After that, the modelling methodis explained in detail based on Matlab/Simulink.And a novel modulation mode is proposed whenarranging the PWM sequences, which is superior tothe commonly used one for MC. And this may layE-ISSN: 2224-266Xresearchesand2 Dual SVM Strategy of MC2.1 Topology of Three-Phase to Three-PhaseMCThe three-phase to three-phase matrix converterutilizes 9 bidirectional switches for connecting theinput phases to the output phases as shown in Fig.1(a). Each bidirectional switch can be replaced bytwo anti parallel unipolar turn-off powersemiconductor such as insulated gate bipolartransistor (IGBT) with coupled diodes. The LC filterof the input grid side is adopted to prevent excessivevoltages. Then, indirect matrix converter topologycan be proposed with an imaginary DC-link withoutusing any energy storage element as shown in Fig.1(b). It can be observed that the virtual sourcerectifier (VSR) stage is connected to voltage-sourcewhile the virtual source inverter (VSI) is connectedto current-source.The indirect matrix converter topology arefunctionally equivalent to the standard matrixconverter, and for each valid switching state of theequivalent indirect AC-DC-AC converter, there is aunique switch state of direct matrix convertercorresponding to it. Therefore, the existing mature35Volume 15, 2016
WSEAS TRANSACTIONS on CIRCUITS and SYSTEMSYongchao Chen, Zhenwei Liu, Yuwei Zou, Yanda Livectors divide coordinate plane into 6 equal sectors.The three-phase instantaneous input current can bemapped to rotating reference vector by Parktransformation, while rotating space vector can besynthesized from pulse width modulation of staticcurrent vectors. That is, when the desired targetvector is located in a certain sector, the rotatingspace vector can be synthesized from two staticvectors and one zero vector which compose thesector triangle. In a single switching cycle, effectivevectors operate for a period of time in accordancewith the requirements of the reference current vector,and output line voltage. The rest of the time isallotted for zero vector duration, there is no voltageoutput and only provides free-wheeling load current[8].The current space vectors of the rectifier areshown as in Fig.2. Static current space vectors are corresponding to Table 1. I i is the target currentspace vector modulation algorithm can be applied toVSR and VSI respectively, both of them are finallyintegrated to obtain the modulation function matrixand to complete a transformation [7].(a) Topology of three-phase to three-phase MC. space vector and θi is the sector angle of I i .VSRDC-linkVSI(b) Equivalent circuit of MC.Fig.1 Topologies of MC and its equivalent circuit.2.2 SVM of VSRConsidering that the VSR need to meet therequirements of short circuit avoidance between anytwo phases, and output current cannot bedisconnected at the same time. There are 9 differentcombination switch states as shown in Table 1.Fig.2 Synthesis of input current vector.Table 1 Current space vectorVector I1 I2 I3 I4 I5 I6 I7 I8 I9S apSbpS anSbnScpScn Assume that the target current space vector I i 100100100001001001011000010010000110110000 1 dα d β d 0i 001100Where mi is the modulation factor of VSR.000011 and one zero vector according to current-secondbalance principle. The switching-on timerepresented by duty cycle of the selected vectors canbe obtained as follows. dα mi sin(60 θi ) (1) d β mi sin θi 2.3 SVM of VSIIn the above table, I1 I 6 are effective vectorsAs for VSI, considering the output current of eachphase must not be disconnected and the DC-link while I 7 I 9 are zero vectors. These 6 effectiveE-ISSN: 2224-266X falls into sector 1. It can be synthesized by I1 , I 636Volume 15, 2016
WSEAS TRANSACTIONS on CIRCUITS and SYSTEMSYongchao Chen, Zhenwei Liu, Yuwei Zou, Yanda Liit carries out both the output line voltage spacevector modulation and the input current space vectormodulation [9]. The switch state of VSR and VSIcan be equalized to 9 switch states of MatrixConverter. Since the input phase current and outputline voltage has six non-zero space vectorsrespectively, there are 36 kinds of combinations,each corresponding to one combination of the 9switches, as table 3 shows it.must not be short-circuited, six switches cangenerate eight kinds of possible combinationsincluding six effective space vectors and two zerovectors as shown in Table 2.Table 2 Voltage space vectorVector U1 U2 U3 U4 U5 U6 U7 U8S ApS AnS BpS 010101Table 3 Correspondence of switch combination U1 U2 U3 U4 U5 U6The modulation of VSR and VSI are very similar, as shown in figure 3. U o is the target voltage space vector and θu is the sector angle of U o . I2 I3 I4 I5 bbabcaccbcIn the above table, 3 lowercase letters indicateinput connection with output in A, B, C phase order. Still, assume that both I i and U o fall into sector 1respectively. There are five kinds of combinationand one PWM cycle corresponds to five duty cyclesof voltages and currents. Each duty cyclecorresponds to one certain switch combination ofmatrix converter. I1 U1 : d1 dα d µ m sin(60 θi ) sin(60 θu ) I1 U 2 : I 2 U1 : I2 U 2 : I 0 U 0 :d 2 dα dν m sin(60 θi ) sin θud3 d β d µ m sin θi sin(60 θu )(3)d 4 d β dν m sin θi sin θud 0 1 d1 d 2 d3 d 4So the corresponding switching-on time can begeneralized as:(4) Ti d 0,1, 2,3, 4)i TS (iWhere TS is a switching period and T0 T4 are timeof switching on of 5 kinds of switch combinationsrespectively.Fig.3 Synthesis of output voltage vector.Assume that the target vector also falls into sector1. When synthesizing the rotating voltage spacevector from static vectors, there is: d µ mu sin(60 θu ) (2) dν mu sin θu d 1 d µ dν 0u3 Modeling for MC System3.1 Selection of Simulation ToolsWhere mu is the modulation factor of VSI.Matrix Converter simulation requires a largenumber of power devices and many real-timecomputations of complex control strategy. In thispaper, Matlab/Simulink is adopted to implement themodels, which is very powerful for matrix andvector operations and is flexible and convenient in2.4 Synthesis of SVM for MCThe SVM of MC can be synthesized by the abovetwo types of space vector modulation. For matrixconverter, one switch is responsible for not onlyrectification but also inversion. In each PWM cycle,E-ISSN: 2224-266X I137Volume 15, 2016
WSEAS TRANSACTIONS on CIRCUITS and SYSTEMSYongchao Chen, Zhenwei Liu, Yuwei Zou, Yanda Liprogramming. Simulink function blocks, embeddedM-file as well as S-function can all be used inmodelling. M-file and Simulink function block areoften used in building simple models. For complexalgorithm S-function is preferred as it runs 10 timesfaster or more than those implemented by Simulinkfunction blocks [10].The matrix converter is a hybrid system becausethe modulator is a digital discrete component whilethe grid, input filter, and load are continuouscomponents. Hence discrete modulator should bebuilt as a subsystem that is triggered in switchingfrequency. When discussing the performance ofMC, the impact of discrete components like zeroorder-holder and one-sample-delay which resultfrom digital implementation of the modulation can’tbe ignored. Because it will leads to difference whilestudy MC characteristics like stability [11-12].Simulation step is another important setting that willaffect the simulation results and should be chosencarefully in purpose of accuracy and speedy.3.3 Modulation Mode ModuleMost of published papers related to matrix converterare based on nine-step modulation mode shown asin Fig.3 [13-14]. It is symmetrical sequencescentered by a zero vector. There are 10 times ofcommutation and only one zero vector to act in aswitching period.Fig.4 Common modulation mode for MC.A novel modulation mode is adopted as isrepresented in Fig.5. When the sum of input andoutput sector numbers is even, the switch order isT1 T2 T4 T3 T0. When the sum of input andoutput sector numbers is odd, the switch order isT2’ T1’ T3’ T4’ T0’, as indicated by the arrow intable 3. Zero vector of the last step is selectedaccording to the principle of minimum commutation.They are asymmetrical sequences and there are only4 times of commutation in a switching period. Thereare two zero vectors act on for equal timerespectively in a switching period, which is morereasonable than that of one zero vector for equaltime. Besides, there are much fewer commutationtimes greatly reducing loss of switches. So, themodulation mode proposed here is obviouslysuperior to the modulation mode which is oftenstudied for MC.3.2 Time Calculation ModuleAccording to formula (22), sector angle of outputvoltage and input current vector are needed whencompute the switching-on time of different switchcombination.The phase angle of output line voltage vector Ѳu’can be calculated as follows.ϖ o t ϕo θ u '(5) ϖ o 2π f oWhere ω0 is the output angular frequency and φois the initial phase angle of output line voltagevector. If phase angle is divided by π/3 and rounded,the sector number can be obtained. Meanwhile, itsremainder should be the sector angle. Embedded Mfile can be used to carry out the computation asfollows. θu '), 6) 1; N u mod( fix((6)π /3 θ mod(θ ' , π /3)u uIn above formula, both ‘fix’ and ‘mod’ arefunctions provided by matlab. The ‘fix’ functionrounds the element towards zero and the ‘mod’function produce remainder after division. Noticethat the syntax rules of M-file should be respectedwhen programming the formula. Also, the sectorangle and the vector number of input current vectorcan be obtained in a similar way. After that, theswitching-on time of different switch combinationcan be calculated according to formula (3) and (4).E-ISSN: 2224-266X(a) Modulation mode while the sum of sectornumbers is even.(b) Modulation mode while the sum of sectornumbers is odd.Fig.5 Novel modulation mode for MC.Modulation mode is realized by S function.Different switch combinations are defined at first,and then look up table for switch combinationaccording to each vector combination.38Volume 15, 2016
WSEAS TRANSACTIONS on CIRCUITS and SYSTEMSYongchao Chen, Zhenwei Liu, Yuwei Zou, Yanda Li4 SimulationSimulation study is carried out under thesymmetrical three phase power supply and loadcondition. Followings are the parameters employedin simulations.Table 4 Parameters CategoriesParametersValueGrid phase voltage(RMS)220 VGrid frequency50 HzInput filter inductance0.8mHInput filter capacitance20uFOutput frequency100 HzSwitching frequency10kHzModulation factor0.6Resistance of load3.5ΩInductance of load10mHFig.7 Spectrum analysis of output line voltageThe simulation results of output voltage, outputcurrent and input current waveforms are obtained aswell as respective spectrum analysis. As arepresented in Fig.6 Fig.11. According to thewaveforms and their spectrum analysis, it can beseen clearly that the input and output currentwaveform are satisfying sinusoidal waveforms. Andthe output line voltage is fair to good quality ofsinusoidal PWM wave despite that the THD is alittle bit high.Time/sFig.8 Output current of MCFig.9 Spectrum analysis of output currentTime/sFig.6 Output line voltage of MCTime/sFig.10 Input current drawn from gridE-ISSN: 2224-266X39Volume 15, 2016
WSEAS TRANSACTIONS on CIRCUITS and SYSTEMSYongchao Chen, Zhenwei Liu, Yuwei Zou, Yanda Li[5] Li Zhiyong ， Zhu Jianlin ， Yi Lingzhi etc.“Simulationresearchofspace-vectormodulated matrix converter”, Proceedings ofthe CSEE, 2003, Vol. 23, No. 3, pp. 80-84．[6] Hou Rongjun, Wang Ben, Zhao Sicheng, etc.“Research of the AC-AC converter controlstrategy based on the direct power”, ElectricalMeasurement & Instrumentation, 2012, Vol. 49,No. 5, pp. 60-64.[7] Huber L, Borojevic D., “Space vectormodulated three-phase to three-phase matrixconverter with input power factor correction”,IEEE Trans. on IA, 1995, Vol. 31, No. 6, pp.1234-1246.[8] Ding Wei, Zhu Jianlin, Fan Lv, etc. “Matrixconverter and its research situation”, NaturalScience Journal of Xiangtan University (S10005900), 2002, Vol. 24, No. 2, pp. 185-187.[9] Mo Zhijuan. “Research of Matrix Convertercontrol method simulation”, Tianjin Universitymaster's degree thesis, 2006.[10] LIU Fu-rong, Klumpner Christian, BlaabjergFrede, “ Modeling and simulation of matrixconverter”, Proceedings of the CSEE, 2005,Vol. 25, No. 9, pp. 62-67.[11] Liu F, Klumpner C, Blaabjerg F. “Stabilityanalysis and experimental evaluation of amatrix converter drive system”, Proc. ofIECON’ 03, 2003, U.S.A.[12] Casadei D, Serra G, Tani A etc. “Analysis ofdigital implementation effects on matrixconverter stability”, Proc. of EPE’03, 2003,Durham, UK.[13] Larsen K B, Jorgensen A H, Helle L, etc.“Analysis of symmetrical pulse widthmodulation strategies for matrix converters”,Proc. of PESC’ 2002, 2002, Paris, France.[14] Liu Zhihua. “Research of doubly-fed motorspeed control system and its ExcitationController”, Wuhan: Huazhong University ofScience and Technology Master's degree thesis,2005.Fig.11 Spectrum analysis of input current5 ConclusionsThis paper introduces dual space vector modulationstrategy for matrix converter and explains how thesimulation models are built up. A novel optimizedmodulation mode is proposed which is superior tothe commonly used one. Finally, simulationwaveforms are presented which demonstrate thefeasibility and validity of the proposed modulationmode. And the method can be directly implementedto practical MC system. It lay strong basis for itsfurther researches and approaching to applicationsand is very helpful to the realization of MC.AcknowledgementThis work was supported by Henan provincescientific and technological brainstorm project(152102210294).References:[1] P. Wheeler, J. Rodriguez, J. C., etc. “Matrixconverters: A technology review”, IEEE Trans.Ind. Electron., Vol. 49, No. 2, 2002, pp. 276–288.[2] J. W. Kolar, F. Schafmeister, etc. “Novel threephase AC-AC sparse matrix converters” , IEEETrans. Power Electron., Vol. 22, No. 5, 2007,pp. 1649–1661.[3] A. S. Oshaba, E. S. Ali, and S. M. Abd-Elazim.“Speed control of switched reluctance motorfed by PV system using ant colonyoptimization algorithm”, WSEAS Transactionson Power Systems, Vol. 9, 2014, pp. 376- 387.[4] A. S. Oshaba, E. S. Ali and S. M. Abd-Elazim.“Artificial bee colony algorithm basedmaximum power point tracking in photovoltaicsystem”, WSEAS Transactions on PowerSystems, Vol. 10, 2015, pp. 123-134.E-ISSN: 2224-266X40Volume 15, 2016
The indirect matrix converter topologyare functionally equivalent to the standard matrix converter, and for each valid switching state of the equivalent indirect AC-DC-AC converter, there is a unique switch stateof direct matrix converter
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prediction of their share prices by using SVM. Again the parameters those are used in SVM are passed in the proposed Genetic Algorithm to make the optimal values. The same data are also implemented in SVM-GA to compare the prediction accuracy of share price with SVM. 4.1 Data Sets The model of forecasting is used with the following real
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SVM regression models are widely used in time series forecasting domain. Such as, in the paper of [23], the authors examined the feasibility of SVM in financial time series forecasting by comparing with neural network model. For the paper of [24], a SVM regression model was used to predict the stock price index.
implementation details of the SVM classification prob-lem. We present our results in Section 6 and conclude in Section 7. 2. Support Vector Machines We consider the standard two-class soft-margin SVM classification problem (C-SVM), which classifies a given data point x Rn by assigning a label y { 1,1}. 2.1. SVM Training
