Alexandia Engineeing Jounal (212) 51, 77 83 Alexandia Univesity Alexandia Engineeing Jounal www.elsevie.com/locate/aej www.sciencediect.com ORIGINAL ARTICLE Single-to-thee phase induction moto sensoless dive system Z.M.S. El-Babay * Depatment of Electical Engineeing, Kafelsheikh Univesity, Egypt Depatment of Electical Engineeing, King Khalid Univesity, Saudi Aabia Received 19 June 211; evised 2 May 212; accepted 27 May 212 Available online 2 June 212 KEYWORDS Voltage Souce Revesible Rectifie (VSRR); Fou-Switch Thee-Phase (FSTP) invete; Six Switch Thee-Phase (SSTP) invete; Vecto contol; Digital Signal Pocesso (DSP) Abstact This pape pesented a single to thee-phase induction moto dive system to povide vaiable output voltage and fequency. The poposed dive system employs only six IGBT switches, which fom the font-end ectifie and the output invete fo the one step convesion fom singlephase supply to output thee-phase supply. The font-end ectifie pemits bidiectional powe flow and povides excellent egulation against fluctuations in souce voltage. Moeove, it incopoates active input cuent shaping featue. The contol stategy of the poposed dive system of theephase induction moto is based on speed sensoless vecto contol technique. A low cost of moto dive and much moe advantages can be achieved using the poposed dive system. Simulation and expeimental esults ae caied out to analysis and exploe the chaacteistics of the poposed dive system. ª 212 Faculty of Engineeing, Alexandia Univesity. Poduction and hosting by Elsevie B.V. All ights eseved. 1. Intoduction In home domestic appliances, ual electic systems and emote aeas the cost to bing thee-phase powe to a emote location is often high. This is due to high cost of a thee-phase extension. Futhe, the ate stuctue of a thee-phase sevice is highe than the single-phase sevice. A single-wie eath etun tansmission line has poved to be a cost-effective solution fo * Tel.: +9 581352199. E-mail addess: zelbabay@yahoo.com Pee eview unde esponsibility of Faculty of Engineeing, Alexandia Univesity. Poduction and hosting by Elsevie deliveing powe to ual communities. Single-phase powe is adequate fo many domestic applications such as lighting, heating and poweing small appliances. Howeve, poblems aise as soon as applications demand the use of medium electic motos. These applications include pumps fo iigation o dinking wate, ai conditions, elevatos, washing machines, machiney fo mills o small industies. The single-phase induction moto, up to sizes of 5 kw, has been a ubiquitous moto fo many yeas in applications whee a single-phase supply is eadily available, such as in the household. These ae used in efigeatos, washing machines, fans, food mixes, pumps and ai conditiones. In most of these applications the moto is actually a two-phase moto. Usually the moto uns at one, two o at most thee spee obtained though manual intevention. Obviously, the moto opeates at non-optimum efficiency and at low powe facto. Vaiable 111-18 ª 212 Faculty of Engineeing, Alexandia Univesity. Poduction and hosting by Elsevie B.V. All ights eseved. http://dx.doi.og/1.11/j.aej.212.5.3
78 Z.M.S. El-Babay speed opeation has been obtained though voltage contol using tiacs o back-to-back thyistos. Howeve, these suffe fom lage hamonic injection into the supply netwok and low powe facto. Fixed speed opeation often means that the pocess, which is not contolled to the desied extent, consequently cannot be made to espond well to what is desiable and adequate. A wide speed ange, tuly vaiable-speed moto, fees the designes to come up with bette opeating featues. This can be achieved by using thee-phase moto, which ae moe eadily available. Theefoe, single-phase to thee-phase convetes is a suitable solution fo these situations whee thee-phase powe is not available. Vaious metho, including static phase convete, otay phase convetes, educed topology powe electonic convetes and novel moto designs have all been investigated [1 4]. Vaiable-speed dives using thee-phase invetes and ac motos have aleady found widespead pactical application in vaious foms. Cetain applications, howeve, still equie a futhe cost eduction fo the dive. The eduction of the numbe of powe semiconducto device components in the convete should be the main consideation fo educing the cost of the contol subsystem. The use of tansistos instead of thyistos eliminates the foced commutating components and pesents distinct advantages fo dives in the powe ange up to 5 kva. A futhe eduction in components is possible by consideing altenatives to the conventional thee-phase bidge configuation fo a voltage-fed invete, since this cicuit uses six switching devices and six eactive powe diodes. These consideations lead to a bidge cicuit with only fou switching devices and fou eactive powe diodes. It has been shown that a two-level cuent contol can be implemented to yield quasi-sinusoidal cuents in the thee-phase load [5,]. This pape pesents single-to thee-phase sensoless induction moto dive system. The poposed dive system employs only six IGBTs tansistos convete fo ectifie and invete stuctue. This configuation incopoates font-end half bidge active ectifie. This ectifie povides the dc-link voltage with active input cuent shaping featue. A fou-switch invete with split capacitos in the dc-link povides a balanced thee-phase output to the moto. The convete daws nea sinusoidal cuent fom the ac mains at close to unity powe facto and theefoe satisfies stict hamonic cuent standa. Bi-diectional powe flow is possible between the ac mains and dc-link. The fou switches makes the invete less cost, less switching losses, less chances of destoying the switches due to lesse inteaction among switches, less complexity of contol algoithms and inteface cicuits as compaed to the conventional Six Switch Thee-Phase (SSTP) invete. The poposed sensoless speed contol appoach intoduces moe eduction such as, the computation fo eal time implementations. Also, the use of speed sensoless fo induction moto dives besides being educing bulky and incease the obustness, it educes additional electonics, exta wiing, and exta space. Also, educes exta cost to the dive system, speed senso. It also, implies caeful mounting which detacts fom the inheent obustness of the dive. The poposed sensoless contol method veifies the validity of model efeence adaptive system (MRAS)-based speed estimato with the six switches convete fed induction moto dive system fo cost eduction and othe advantages such as educed switching losses, educed numbe of inteface cicuits to supply logic signals fo the switches, easie contol algoithms to geneate logic signals. Thus, the main issue of this pape is to develop a cost effective, simple and efficient high pefomance induction moto dive. A closed-loop vecto contol scheme of the poposed induction moto dive system incopoating the MRAS is simulated using the MATLAB/SIMULINK. Also, a laboatoy dive system is built and tested using the six switches convete to exploe the most impotant featue of the low cost dive. 2. Six switch convete The single to thee-phase convete is configued as shown in Fig. 1. The switches T 1 and T 2 fom the font-end ectifie. Two split capacitos fom the dc-link. The output invete convets the dc-voltage to a balanced thee-phase output with adjustable voltage and fequency. This invete is configued with fou switches T 3,T 4,T 5 and T, espectively. Two output phases ae taken fom the invete legs diectly whee the thid output is taken fom the midpoint of the two capacitos. 2.1. Font-end ectifie The font-end ectifie convets a single-phase utility ac supply voltage to dc-voltage. A boost inducto, L s, is connected in seies with the utility supply voltage. The powe tansistos T 1 and T 2 ae switched on using cuent foced contol (CFC) stategy that enables the device to opeate with a sinusoidal line cuent. As a esult, little distotion, unity powe facto and egulated dc busba voltage can be achieved. Moeove, this contol stategy pemits powe tansfe in eithe diection between ac mains and dc busba voltage. So, this ectifie calls single-phase Voltage Souce Revesible Rectifie (VSRR). The two capacitos (designated C o ) initially have to be chage up to the peak voltage of the utility supply via the invese paallel diodes acoss the tansistos. The two capacitos must be lage enough to appea as an essentially constant dc voltage souce with low ipple contents [7]. The lage size of C o also means that some fom of soft stat must be included duing the initial chage up to pevent tansient inush cuent fom haming cicuit components. Once the capacitos have fully chaged and the diodes ae evesing biased, it becomes vitually constant dc voltages. The output voltages E dc+ and E dc can be kept constant by connecting the capacitos in seies with the voltage souce, V s, via the two tansisto switches T 1 and T 2. Note that only one-tansisto tun on at a time, o Figue 1 Six switch convete configuation.
Single-to-thee phase induction moto sensoless dive system 79 Figue 2 else a shot cicuit of the dc voltages will occu. If a tansisto that conducting cuent is tuned off, owing to the inductive natue of the cicuit, the cuent instantaneously feewheels though the diode acoss complementay tansisto. If the same tansisto is tuned back on, then the conducting diode will evese biased and the cuent will switch to flow back though the tansisto. In a CFC scheme, wheneve a tansisto is tuned on the complementay tansisto is always tuned off. So, the two tansistos/diodes essentially behave as a two pole bi-diectional switch. This switch conveniently is epesented as switching logic vaiable NS. Using this logic vaiable, the cicuit diffeential equations can be witten as: i s ¼ 1 Z ðv s NS E dcþ ð1 NSÞE dc Þdt ð1þ L s E dcþ ¼ 1 Z ðns i s i l Þdt ð2þ C o E dc ¼ 1 Z ðð1 NSÞi s þ i l Þdt ð3þ C o whee i l is the load cuent which may be i a, i b o i c. NS =1,if T 1 o D 1 is on and NS =,ift 2 o D 2 is on. Fom the above equations it can be seen that if T 1 is on the supply cuent i s will decease. On the othe hand, if T 2 is on, the cuent will incease. Hence, the cuent can be foced to tack a efeence wavefom i simply by switching on T 2 if the cuent is highe than i, o by switching T 1 on if the cuent is lowe than i. Fo the device to opeate with a sinusoidal input cuent and unity powe facto it is necessay to poduce a sinusoidal-cuent efeence wavefom that is eithe in phase o 18 out of phase with ac utility supply voltage. In addition, the dc voltage E dc must be maintained equal to a efeence E dc unde all load conditions. Both these can be obtained using the contol scheme of Fig. 2. Compaing a dc efeence, E dc, with the actual dc-link voltage, E dc, the output eo, e, is filteed and modified by a PI contolle. The filte output, U, multiplied by a unit vecto signal deived fom the supply voltage to poduce the equied cuent efeence i. The cuent efeence is then compaed with the actual supply cuent to detemine which tansisto should be tuned on. If E dc is too low then the eo is positive and i is poduced in phase with V s. The powe is tansfeed fom the ac to the dc side (ectifying) and consequently inceasing E dc. 2.2. Output invete MRAS speed estimation. This invete is configued with fou switches T 1, T2, T3 and T 4, espectively. Two output phases ae taken fom the invete legs diectly whee the thid output is taken fom the midpoint of the two capacitos. A detailed compaison of the fou-switch invete with the conventional six-switch invete configuation is given in [5,]. Two contol possibilities exist to contol the fou-switch bidge invete, i.e., two-level cuent contol to foce the two contolled phases cuents to sinusoidal, o using PWM to contol the voltages applied to the thee-phase quasi-sinusoidally. The two-level cuent contol of the fou-switch bidge invete is used to contol the load cuent by focing it to follow a efeence one. This is achieved by the switching action of the invete to keep the cuent within the hysteesis band. The load cuents ae sensed and compaed with espective command cuents using two independent hysteesis compaatos. The output signals of the compaatos ae used to activate the invete powe switches. This contolle is simple and povides excellent dynamic pefomance. The modulated phases voltages of fou switch invete ae intoduced as a function of switching logic NA, NA1, NB and NB1 of powe switches by the following elations [8]. V a ¼ E dc ð4na þ 2 NB 1Þ 3 ð4þ V b ¼ E dc ð 2NA þ 4 NB 1Þ 3 ð5þ V c ¼ E dc ð 2NA 2 NB þ 2Þ 3 ðþ whee NA1 and NB1 ae complementay of NA and NB. 2.3. Induction moto model and vecto contol The mathematical model of thee-phase squiel cage induction moto in d e q e is descibed as: 2 V e 3 2 3 2 R s þ pl x e L p Lm Lm x L e I e 3 L V e 7 4 5 ¼ Lm x e L R s þ pl x e p Lm L L 7 4 R L m R þ pl ðx e x ÞL m 5 : I e k e 7 4 5 q R L m ðx e x ÞL m R þ pł k e d The electomechanical equations ae given by T e T L ¼ J dx dt þ Bx ð7þ T e ¼ 3 2 P L m ði e 2 L ke d Ie ke q Þ ð8þ Eq. (8) denotes that the toque can initially popotional to the quadatue component of the stato cuent I e if the qe - axis component of the flux becomes zeo (d e -axis is aligned with the oto flux axis), and the d e -axis component k e d is kept constant. This is the philosophy of the vecto contol technique. In accodance, Eq. (8) is lineaized as: T e ¼ K t jk e d jie ð9þ This equation is simila to that of the sepaately excited dc moto. The angula slip fequency command (x sl ) is: The fou switch thee phase invete is configued as shown in Fig. 1. The invete convets the dc-voltage to a balanced thee-phase output with adjustable voltage and fequency. x sl ¼ L m s and Ie k e d ð1þ
8 Z.M.S. El-Babay I e ¼ 1 ð1 þ s L pþke d m Angula fequency is obtained as follows: x e ¼ x þ x sl Z h e ¼ x e dt ð11þ ð12þ ð13þ The toque poducing cuent component is calculated fom: I e ¼ 1 ðx x Þ K ps ½1 þ s cs SŠ ð14þ k t k e s d cs S 3. MRAS fo the sensoless contol of induction moto Model Refeence Adaptive Systems (MRAS) techniques applied in ode to estimate oto speed. This technique is based on the compaison between the outputs of two estimatos. The outputs of two estimatos may be (the oto flux, back e.m.f. o moto eactive powe). The estimato that does not involve the quantity to be estimated (the oto speed x ) is consideed as the induction moto voltage model. This model is consideed to be the efeence model (RM). And the othe model is the cuent model, deived fom the oto equation, this model consideed to be the adjustable model (AM). The eo between the estimated quantities by the two models is used to dive a suitable adaptation mechanism which geneates the estimated oto speed [9]. In this pape, the state vaiable of MRAS technique is the stato cuent and oto flux. The speed estimating pocedues fom the stato cuent eo ae as follows: fist, fom the induction moto equation the stato cuent is epesented as: i ¼ 1 Lm ½k d þ x T k q þ T pk d Š i ¼ 1 ð15þ Lm ½k q x T k q þ T pk q Š Using Eq. (15), and estimated instead of measued speed, the stato cuent is estimated as follow: i ¼ 1 Lm ½k d þ x T k q þ T pk d Š i ¼ 1 ð1þ Lm ½k q x T k q þ T pk q Š Fom the elationship between the eal stato cuent and the estimated stato cuent, the diffeence in the stato cuent is obtained as i i ¼ T h i Lm k q x x i i ¼ T h i ð17þ Lm k d x x In Eq. (17), the diffeence of stato cuent is sinusoidal value because it is the function of oto flux. Multiplying by the oto flux and adding them togethe; i i k q ¼ T h i Lm k2 q x x i i k d ¼ T h i ð18þ Lm k2 d x x By summing the above two equations. i i k q þ i i k d ¼ T h i Lm k2 q þ k2 d x x ð19þ Hence, the eo of the oto speed is obtained as follows: x x ¼ i i k q i i k d K whee K ¼ T ð2þ Lm k2 q þ k2 d The ight hand tem seems as the tem of speed calculation fom adaptive obseve, so the speed can be calculated by the following Eq. (17): x ¼ 1 K K p i i k q i i k d Z þ K I i i k q i i k d ð21þ Fig. 2 shows the MRAS system. 4. Oveall dive system The contol scheme of low cost ac induction moto dive is shown in Fig. 3. It incopoates the speed contolle which eceives the eo signal between the command speed and the actual obseved speed of the moto shaft and then geneates the toque command (T e ) though a PI speed contolle. This toque command poduces the quadatue cuent command I e in the oto flux method descibed in Eq. (14). Figue 3 Block diagam of sensoless induction moto dive system.
Single-to-thee phase induction moto sensoless dive system 81 The diect axis cuent component I e is set by the oto flux level, k e d as descibed in Eq. (11). This flux level is calculated accoding to the efeence fame (STRF) with the aid of the calculated command angle (h e ). This command angle is calculated in such a way that aligns the d e -axis of SYRF with the oto flux axis. The two stato cuent comman, I e and Ie in the SYRF ae then tansfomed to STRF and then tansfomed to thee phase efeences cuent i a, i b and i c []. Only, two cuents efeence i a and i b equied fo the hysteesis cuent contolle that geneates the switching function fo the pulse width modulated voltage souce invete. 5. Results and discussion The poposed contol system epesented by Figs. 3 and 4 is designed and implemented fo a simulation and expeimental investigation. Simulation is caied out using the geneal pupose simulation package Matlab/Simulink, while expeimental PC DS112 Inteface boad IGBT dive I a I b V b V c DC Invete IGBT Figue 4 Expeimental set up fo DSP-boad contol of induction moto. IM G Load study is implemented using a TMS32C31 floating-point Digital Signal Pocesso [1] (DSP114) hosted on a pesonal compute as shown in Fig. 4. Simulation and expeimental esults ae pesented to show the effectiveness of MRAS speed estimation method at diffeent opeating conditions. These esults ae classified into two categoies; the fist epesents stat-up and steady-state while the second epesents the dynamic pefomance. 5.1. Stat-up and steady-state pefomance Stat-up and steady-state esults ae illustated by Figs. 5 7. Fig. 5a shows measued speed signal obtained in eal time whee as, Fig. 5b shows its coesponding signal obtained off line fom simulation. Fig. a shows estimated speed signals obtained in eal time. whee as, Fig. b shows its coesponding signal obtained off line fom simulation. These esults show a good coelation between the estimated speed signal and its coesponding measued as well as simulated speed signals. In the fou figues, signals ae almost coelated fom statup point up to the steady state value, which is eached afte about 2 ms. The moto phase cuent signals coesponding to stat-up peiod is shown in Fig. 7a and b espectively. These cuent signals ae of sine wave pofiles on which contolle switching tansients ae shown. 5.2. Dynamic pefomance Fo studying the dynamic pefomances of poposed system, a seies of measuements and simulations have been caied out. In this espect, the dynamic esponse of the poposed speed estimation algoithm is studied unde speed step change unde full load condition. To study the dynamic esponse of the contol system due to a step changes in the command of speed, the moto is subjected Speed (ad/sec) Measued Speed (ad/sec) 12 1 8 4 2 Measued Refeence -2.5 1 1.5 2 2.5 3 3.5 4 4.5 5 12 1 8 4 2-2.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Figue 5 Moto measued speed at stat-up: expeimental and simulation. Speed (ad/sec) Estimated speed (ad/sec) 12 1 8 4 2 Refeence Estimated -2.5 1 1.5 2 2.5 3 3.5 4 4.5 5 15 14 12 1 8 4 2-2.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Figue Moto estimated speed at stat-up: expeimental and simulation.
82 Z.M.S. El-Babay Phase cuent (Amp.) Phase cuent (Amp) 4 2-2 -4 -.2.4..8 1 1.2 1.4 1. 1.8 2 4 2-2 -4 -.2.4..8 1 1.2 1.4 1. 1.8 2 Cuent (Amp) 15 1 5-5 -1-15.3.4.5..7.8.9 Figue 7 Moto phase cuent at stat-up: expeimental and simulation. Figue 9 Moto phase cuent at speed step change: expeimental and simulation. Refeence speed Estimated speed 1 Measued speed Supply cuent and Supply voltage/5 5-5 -1.9 1 1.1 1.2 1.3 1.4 1.5 1. 1.7 1.8 Time (sec.) Figue 1 Supply (voltage/5) and cuent (simulation). Estimated speed (ad/sec) 15 1 5.5 1 1.5 2 2.5 3 Figue 8 Moto speed at speed step change: expeimental and simulation. Dc-Link voltage (volts) 1 8 4 2.9 1 1.1 1.2 1.3 1.4 1.5 1. 1.7 1.8 Time (sec.) Figue 11 Dc-link voltage (simulation). to step incease in the speed command to evaluate its pefomance. At t =.9 s. The moto speed command is changed fom 9 ad/s to 12 ad/s. Fig. 8a and b shows the moto speed signals coesponding to these step changes. It can be seen that the moto speed is acceleated smoothly to follow its efeence value with nealy zeo steady state eo. Fig. 8a shows measued and estimated speed signals obtained in eal time. Fig. 8b shows the estimated speed signal and its coesponding signal obtained off line fom simulation. These esults show a good coelation between the estimated speed signal and its coesponding measued as well as simulated speed signals. Phase cuent coesponding to this speed step changes ae shown in Fig. 9a and b) espectively. Fig. 9a epesents the phase cuent and its efeence command also with a good coelation between them. These esults ensue the effectiveness of the poposed contolle and shows good
Single-to-thee phase induction moto sensoless dive system 83 behavio of its dynamic esponse. Fig. 1 shows the supply cuent with supply voltage. It is noticed that the supply cuent is in phase with supply voltage even duing the peiod of speed changes. This means that unity powe facto can be achieved iespective of the moto dynamics. Fig. 1 shows that the dc-link voltage is not affected by speed changes. This is one aim of ectifie design. It is shown that the contol of the ectifie woks independently (see Fig. 11).. Conclusion This pape has pesented a single-phase to thee-phase convete fo low cost induction moto dives. This convete povides vaiable output voltage and fequency. The poposed convete has maintained sinusoidal input cuent with unity input powe facto and Bidiectional powe flow has been achieved. Based on sensoless speed of vecto contol technique, a contol stategy of the poposed convete to dive induction moto has been implemented. The pefomances of the poposed MRAS-based six switches convete fed induction moto dive has been investigated. The low cost ac dive has been ensued using the poposed system. A laboatoy dive system has been built and tested to veify the most impotant featues of the poposed dive system. The esults have been shown the efficacy of the low cost ac dive system. Appendix A Machine paametes of the applied induction Rated powe 1.1 kw Rated load toque 7.5 N m No. of poles 4 Stato esistance 7.482 X Roto esistance 3.84 X Roto leakage inductance.221 H Stato leakage inductance.221 H Mutual inductance.4114 H Moto speed 15.p.m. List of symbols: L ¼ L s L2 m L ; ¼ 1 L2 m L sl, V e, V e is the q e d e axis stato voltage, I e, I e the q e d e axis stato cuent, k e, k e the q e d e axis stato flux linkage, R s, R the stato and oto esistances, J, B the moment of inetia and viscous fiction coefficients and L s, L, L m is the stato, oto and mutual inductances. Refeences [1] Jin-Su Jang, Byoung-Gun Pak, Tae-Sung Kim, Dong Myung Lee, Dong-Seok Hyun, Sensoless contol of fou-switch theephase PMSM dive using extended Kalman filte, industial electonics, IECON 28, in: 34th Annual Confeence of IEEE, pp. 138 1372. [2] M.N. Uddin, T.S. Radwan, M.A. Rahman, Pefomance analysis of a 4-switch, 3-phase invete based cost effective IPM moto dives, in: Canadian Confeence on Electical and Compute Engineeing, 24, pp. 85 88. [3] C.B. Jacobina, E.R.C. da Silva, A.M.N. Lima, R.L.A. Ribeio, Vecto and scala contol of a fou switch thee phase invete, in: Confeence on Rec., IEEE-IAS Annu. Meeting, 1995, pp. 2422 2429. [4] C.B. Jacobina, M.B. de Rossite Coea, E.R.C. da Silva, A.M.N. Lima, A geneal PWM stategy fo fou-switch theephase invetes, IEEE Tans. Enegy Conves. 21 (4) (Dec. 2) 832 838. [5] J. Klima, Analytical investigation of an induction moto fed fom fou-switch VSI with a new space vecto modulation stategy, IEEE Tans. Powe Electon 21 () (2), 118 117. [] R.J. Cuise, C.F. Landy, Phase convete fo ual applications, in: Symposium on Powe Electonics, Industial Dives, Powe Quality and Taction systems, Capi, Italy, June, 199. [7] J.T. Boys, A.W. Geen, Cuent foced single phase evesible ectifie, in: IEE Poceeding, vol. 13, Pt. B. no. 5, Septembe 1989. [8] Nalin Kant Mohanty, Ranganath Muthu, Micocontolle based PWM contolled fou switch thee Phase invete fed induction moto dive Sebian, J. Electic. Eng. 7 (2) (21) 195 24. [9] Chul-Woo Pak, Woo-Hyen Kwon, Simple and obust speed sensoless vecto contol of induction moto using stato cuent based MRAC, Electic Powe Syst. Res. 71 (24) 257 2. [1] DSP-Hadwae, dspace Digital Signal Pocessing and Contol Engineeing GmbH, Gemany, 1993.