Dynamic Simulation of an Induction-Motor Centrifugal-Pump System under Variable Speed Conditions

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1 EEKTROTEHNIŠKI VETNIK 84(): 5-, 7 ORIGINA CIENTIFIC PAPER Dynaic iulation of an Induction-Moto Centifugal-Pup yste unde Vaiable peed Conditions Xiwen Guo,,, Yuliang Wu,, Guoli i,,, Chao u, chool of Electical Engineeing and Autoation, Anhui Univesity, Hefei, Anhui, China National Engineeing aboatoy of Enegy-saving Moto & Contol Technique, Anhui Univesity, Hefei, Anhui, China Engineeing Reseach Cente of Powe Quality, Ministy of Education, Anhui Univesity, Hefei, Anhui, China E-ail: xwguo8@6.co Abstact. With the centifugal pup widely used in the industy, the chaacteistics of its high efficiency and enegy saving have gained oe attention. It has a cetain significance to analyze the efficiency of the pup unit in a odel of the oto-pup syste. In this pape, the efficiency of the centifugal pup at a vaiable otating speed is analyzed by using the vecto contol stategy. Fistly, the oto-flux-oiented vecto contol stategy is used to contol the induction oto. econdly, a centifugal pup odel was built based on stuctual chaacteistics in ihydaulics. Finally, a dynaic siulation of the oto-pup syste was copleted in MATAB/iulink unde vaiable speed conditions. The siulation esults show that the high-efficiency ate of the syste is in the ange fo /in to 5/in. Keywods: centifugal pup, thee-phase induction oto, vecto contol, vaiable speed contol Dinaična siulacija indukcijske centifugalne čpalke pi speenljivi hitosti delovanja šioko upoabo industijskih centifugalnih čpalk se je pokazala tudi poteba po njihove učinkovite in vačne delovanju. Posebna pozonost je naenjena učinkovitosti čpalne enote. V članku analiziao učinkovitost centifugalne čpalke z upoabo azličnega vektoskega kiljenja. iulacijo delovanja čpalke so izvedli v okolju MATAB/iulink pi speenljivi hitosti delovanja. Rezultati siulacij so pokazali, da je delovanje najučinkovitejše ed vt/in in 5 vt/in.. INTRODUCTION The centifugal pup has a good hydaulic pefoance, it suits fo a sall flow and lage lift occasions, which in the industial, agicultual and coecial ae doinant. In pactice, the pup is diven by the oto as a load. The efficiencies of the oto ae geneally able to each oe than 9%, and the pup efficiency can each only 5%. o the enegy efficiency in the oto-pup syste is paticulaly ipotant []. In ode to ipove the oveall efficiency of the oto-pup syste, it is necessay to educe the powe losses of the pup unit []. The efficiency of the pup is deteined by its speed, flow and head chaacteistics. The taditional way is to adjust the ate of the flow though the valve of the pup to achieve the pupose of changing the efficiency and head of the pup. Howeve, the contol valve incease the liquid esistance and fiction coefficient in the pipeline, so that the valve consues a pat of the enegy of the syste. Cuently, the speed con be adjusted to contol the flow, which to achieve the contolling efficiency. The additional losses caused by the thottle valve ae thus educed []. Geneally, the V/F constant pessue fequency atio ethod is used to adjust the speed. The disadvantages of this ethod ae open-loop contol and poo dynaic esponse. The vecto contol assues good stability, fast esponse and good accuacy to atch the needs of the pup [4-5]. Theefoe, this pape adopts the oto field oiented vecto contol stategy to quickly atch the speed of the pup. The efficiency of the centifugal pup unde vaiable speed conditions is analyzed by contolling the oto-field-oiented. It is of a geat significance to futhe eseach how to ipove the oveall efficiency of the oto-pup syste [6-7]. This pape consists of thee ain pats. A odel of the oto-flux-oiented vecto contol of induction oto is pesented in ection. A odel and chaacteistic analysis of the pup ae shown in ection. Finally, the siulation esults ae analyzed in ection.. MODEING OF VECTOR CONTRO FOR THE INDUCTION MOTOR In pactical applications, the thee-phase induction otos often need to contol diffeent speeds to eet the equieents of diffeent loads. Theefoe, it is vey Received Novebe 6 Accepted Mach 7

2 6 XIWEN, YUIANG, GUOI, CHAO ipotant to establish a easonable speed-contol odel of the induction oto. Paticulaly, the vecto contol syste can eet these equieents without changing the pefoance of the oto, slip-vecto contol, ai-gap agnetic-field-oiented vecto contol and oto-flux-oiented vecto contol. The oto-fluxoiented vecto contol enables a decoupled contol of the toque and flux linkage, so that the toque does not affect the flux linkage. In the oto-pup syste, the vecto contol tansfoes the coodinate. The atheatical odel of the induction oto in a two-phase stationay coodinate is conveted into a atheatical odel of a two-phase otating coodinate. As the oto of the uiel-cage induction oto is shot-cicuited, the voltage equations of the induction oto in the otating coodinate ae expessed as follows: u R p p i s s s u i s Rs s p p p s R p s i d s p s R p iq The flux equation is obtained as follows: () s i s i d i () d q iq The electoagnetic toque equation is obtained as follow: J d Te T p ( iid iiq ) () p dt Whee: s... the slip angle speed,... the synchonous angula velocity,... the oto angula velocity, u... the stato voltage on the d axis, u... the stato voltage on the q axis, u d... the oto voltage on the d axis, u q... the oto voltage on the q axis,... the stato cuent on the d axis,... the stato cuent on the q axis, d... the oto cuent on the d axis, q...the oto cuent on the q axis,... the stato-flux-linkage on the d axis,... the stato-flux-linkage on the q axis, d... the oto-flux-linkage on the d axis, q... the oto-flux-linkage on the q axis, p... the nube of the oto poles, p...the diffeential opeato, J... the oent of inetia. In the field-oiented vecto-contol syste, the d q coodinate syste is geneally placed in the induction otating agnetic field. The AC quantity of the stationay coodinate syste is conveted into the DC quantity in the otating coodinate syste. The d axis is set to coincide with the oto-flux linkage diection d. The q axis is pependicula to the diection of the oto flux, and the coponent of oto flux q is zeo. The oto flux is geneated by the d axis of the winding cuent. The voltage equations ae: i i (4) d d d q i i (5) Accoding to foulas (), (), () and (4): J d Te T p ( iid iiq ) p i (6) p dt d i (7) Tp Whee: T R... the oto tie constant. It is well known that the flux and toque of the oto can be copletely decoupled by the foulas (6) and (7). The electoagnetic toque is deteined by the coponent on the q axis of the stato cuent and the oto flux is deteined by the coponent of the stato cuent on the d axis. As oto flux is contolled by the stato cuent i, the toquet e is contolled by and i. o the following equation can be obtained : Tp i (8) i T (9) e p Whee:... expected value of the oto flux, T e... expected value of the toque,... excitation cuent of the stato,... toque cuent of the stato. The pocess of the field-oiented vecto-contol stategy is shown in Fig., whee is deived fo the oto odel. The speed contolle AR uses the PI contol. The calculated value of flux linkage is.7wb. The value is copaed with the flux of the oto oto, and the eo egad as the input of the flux contolle APR. Accoding to the elation between the flux and excitation cuent, the excitation coponent of the stato cuent is i. The flux and speed contolle

3 DYNAMIC IMUATION OF AN INDUCTION-MOTOR CENTRIFUGA-PUMP YTEM UNDER VARIABE PEED COND. 7 ae used to eploy the PI contolle to contol the output. Taking into account the PI contolle the satuation liits the output of the contolle. The liite liits of an extenal and intenal liite. The extenal liite is set by the ated toque and the oveload facto of the oto to contol the output of the PI contolle. The intenal liite aintains the output value at not less than the axiu value of the oto at a steady-state to contol the output of the integato. The paaetes of the PI contolle ae calculated using the engineeing expeience ethod shown in Table. Table : Paaetes of the PI contolle Contolle K Intenal-liite K p i Extenal-liite AR -8~8 5-8~8 APR.8-5~5 -~ Accoding to the oto odel, the oto-flux linkage vecto position angle signal is dt.the theephase altenating cuent of the diving oto is obtained by the invese tansfoation of the coodinate syste and the invete. Finally, the otoflux signal and the speed-signal output of the oto output ae sent to the syste as a feedback to poduce the expected value of the toque and speed unde a steady state. iulation of the oto-flux-oiented vecto-contol stategy syste is shown in Fig.. n X - n AR - X AP T e i p i. CENTRIFUGA PUMP YTEM MODE The ain paaetes of the centifugal pup include that the pup flow ate (Q), head (H), efficiency (η) and speed (n). They ae used as a citeion to easue the pup syste and the ain paaetes fo the dynaic odel analysis. The analysis of the extenal chaacteistics of the centifugal pup consists of two pats: the ated-speed analysis and the vaiable-speed analysis. At the ated speed, the chaacteistics of the pup ae deteinated by the elationship between the flow and the head. Theefoe, they ae obtained accoding to foula () by analyzing and the data fitting. Foula () is used to futhe eseach its dynaic pefoance. H f ( Q ) () Whee: H... the ated head, Q... the ated flow, H f ( Q ) a bq cq () a... a constant of oe than zeo, b... a constant, c... a constant of less than zeo. VR i i s/s i A i B i C Invete i A i B i C Moto n Pup Figue. Roto-flux-oiented vecto-contol oto odel Continuous powegui DC + - g A B C T Univesal Bidge T A B C Induction Moto phi_qd is_abc w Te phi_qd -K- Gain [n] Goto fankui Iabc 6pulses shuu Iabc pulse geneato cope n phi [n] Fo AR n n Te phi phi id APR phi Id phi calculation phi Iq Te iq calculation Id Iabc Iq theta s/ phi Theta W Ist theta calcilation Teta Iq Iabc Id /s Figue. iulation odel of the vecto-contol syste of the induction oto

4 8 XIWEN, YUIANG, GUOI, CHAO At a vaiable speed, the pup chaacteistics change. Accoding to the siilaity theoy (affinity laws) of the pup, the chaacteistic equation of the pup at any speed is[8]. Q n k () Q n H H n n k () P n k (4) P n Foulas () and () can be obtained as follows: n n Q H f Q k f n n k ( ) ( ) Whee: P... the shaft powe of the pup, P... the ated powe of the pup, n... the ated speed of the pup, (5) k... the atio of the actual and ated speed. Foula (5) is the chaacteistic equation of the pup at any speed. At the ated speed, the chaacteistic cuve of the pup is dawn using the oiginal data as shown with cuve in Fig.. Cuve is the chaacteistic cuve at any speed. H B A λl d 4 8( ) ( d g) ξ (7) Whee: H... the static head of the centifugal pup, st... the esistance coefficient of the pipeline,... the along esistance coefficient,... the local esistance coefficient, l... the length of the pipeline, d... the diaete of the pipeline, g... the gavity acceleation. Accoding to the pipeline chaacteistic foula (6), cuve can be dawn as shown in Fig.. The opeating point of the pup is deteined by the chaacteistic of the pup and the chaacteistic of the pipeline. Cuve is intesected with cuve and cuve at the A and B points espectively in Fig., which ae the opeating points of the pup at diffeent speeds []. Howeve, the position of the opeating point is diectly elated to the efficiency of the pup. The efficiency expession is: ghq P (8) P T n (9) 6 Whee:... the wate density, T... the toque load. Accoding to foula (8), the Q cuve can be fitted as shown in Fig. 4, to get the best efficiency point M. η M Figue.. Pup chaacteistics and pipeline chaacteistic cuve The pipeline chaacteistic of the pup is vey ipotant fo the dynaic odel of the centifugal pup syste, because it deteines the opeating point of the pup. Accoding to the hydaulic law [9], that can get the pup pipeline chaacteistic equation is []: H H Q (6) st Q Figue 4. Efficiency cuve of the pup Q

5 Conn Conn C R DYNAMIC IMUATION OF AN INDUCTION-MOTOR CENTRIFUGA-PUMP YTEM UNDER VARIABE PEED COND. 9 olve Configuation f(x)= Ideal Angula Velocity ouce Rap Convete P P T Centifugal Pup A B Oifice Q A B Flow ate senso Gain -K- Conn Conn Outlet pipe Flow ate Q_ V T Constant Tank peed P Convete Inlet pipe V T Constant Tank B A P Ideal Hydaulic Pessue enso P Convete Gain Q_ Hydaulic Fluid Figue 5. iulation odel of the centifugal-pup syste Continuous powegui phi_qd g + T A A is_abc DC B B w - C C Te Univesal Bidge Induction Moto is_abc -K- phi_qd Gain [n] Goto cope speed T Flow Flow pw w Vecto Contol yste output hydaulic input hydaulic Pup yste output hydaulic senso input hydaulic senso Figue 6. iulation odel of the oto-pup syste When the opeating point of the pup is aintained close to the M point, the efficiency of the pup is axially utilized. It is well known that thee ae two ways to change the opeating point of the pup in Fig.. One is to change Cuve by adjusting the valve, which deceases the efficiency of the centifugal pup. The othe is to change the position of Cuve by adjusting the speed. In the oto-pup syste, the latte is used to adjust the speed of the oto by using the vecto-contol stategy, thus aking the pup to opeate at a high-efficiency ate. The odel siulation of the centifugal pup is shown in Fig IMUATION REUT AND ANAYI To analyze the centifugal pup and thee-phase induction oto, the CD-8 and YB-8M- types, espectively, ae selected []. The ated speed and powe of the oto ae 8/in and.kw, espectively. The ated speed of the pup is 8/in. The specific paaetes ae shown in Tables and. The siulation odel of the whole oto-pup syste is shown in Fig. 6. Table : Paaetes of the thee-phase induction oto Paaete U / Rated value f 8V/ 5HZ n 8 /in P R / R s /. KW 5.Ω/ 6.959Ω l ls.9h/.9h Table : Paaetes of the centifugal pup Paaete P H Q n.67 86H N N Rated value 8/in.KW /h The siulation esults show that the oto eaches the ated speed of 8/in unde the ated voltage and load conditions. The apid esponse of the syste eaches the steady-state at about t=.s (in Fig. 7). When the speed of the oto inceases fo to 8 /in, the electoagnetic and load toque get stable at.6n. and N., espectively, (Fig. 8). The output speed and toque of the induction oto atch the set taget of the pup by using the oto-flux-oiented vecto contol in Figs. 7 and 8, which povides the basis fo the high-efficiency opeation of the centifugal pup.

6 Toque T(N.) speed n (ap/in) H( ) Flow Q( /h) XIWEN, YUIANG, GUOI, CHAO Flow Tie t(s) Figue 7. Output speed of the oto Tie t(s) Figue 9. Pup output flow and head at the ated-speed The centifugal pup and the oto ae diectly connected though the otating shaft. The output speed and the output powe of the otating shaft ae the input speed and shaft powe of the centifugal pup, espectively, and the toque is used to dive the centifugal pup load. When the pup input speed is inceased fo to 8/in, the cuve of the flow and the head incease, espectively, as shown in Fig. 9. The output flow ate is zeo at t=-.s, as deteined by the pipeline chaacteistic of the pup. The pup head is oe than the static head; it is 5 at t=.s. The flow begins to output at the pup outlet. The head quickly eaches the axiu value of 8.5 at t=.4s. ubsequently, the flow gadually inceases to.55 /h, and the head deceases until eaching stability of T Te Tie t(s) Figue 8. Electoagnetic toque and load toque Fo the efficiency of the centifugal pup to be ainly elated to the head, flow and shaft powe, foula (8) should siply be used. The expessions fo the head and shaft powe ae obtained with the flow based on the siilaity law. The efficiency and the flow ipleent the following quadatic fit: n q q Deivation of the above expession dn dq yields q.7 with the dn second deivative dq, the efficiency eaches the axiu value of 5.8% of the flow ate of.7 /h. Accoding to foula (8), could be obtained the efficiency cuve is attained based on the head and the flow output wavefo as shown in Fig.. At the tie t=.7s, the efficiency eaches the axiu value of 5.8%. The coesponding flow of the pup is about.4 /h, and the head is close to 55. The siulation esults ae vey close to the theoetical esults, thus indicating the validity and stability of the syste odel. In engineeing, the high-efficiency ate of the pup opeation is the axiu efficiency of the pup decease in the ange fo 5% to 8% []. Accoding to the calculated of 8%, the high-efficiency ate of the pup is in the ange fo 46.7% to 5.8%. The contolled speed of the oto can contol the ate of the pup output flow, while the flow ate is diectly elated to the efficiency of the centifugal pup. The oto-field-oiented vecto-contol stategy is adopted to contol the output speed of the oto in ode to analyze the efficiency of the centifugal pup. At the oto output speed in the ange fo 8/in to 7/in, evey band declines to /in until 8/in and finally ises to 8/in (Fig. ). Thee is a total of twelve bands. As shown in Fig. 9, fo the flow and head to each a steady-state, it takes about 5s at the ated speed, so the sapling tie of each speed band is 5s.

7 H( ) Flow Q( /h) Efficiency (%) peed n( /in) Efficiency ( %) DYNAMIC IMUATION OF AN INDUCTION-MOTOR CENTRIFUGA-PUMP YTEM UNDER VARIABE PEED COND peed Efficiency Tie t(s) Figue. Efficiency of the centifugal pup Flow Tie t(s) Figue. and flow output of the pup at a vaiable speed Accoding to the chaacteistics of the pup, the flow and head output change at a vaiable speed. The flow and head output of the centifugal pup ae shown in Fig.. The esponse and steady-state can be fast at the speed jup tie. The efficiency cuve of the centifugal pup is obtained as shown in Fig.. At the beginning, the speed decease coesponds to the incease in the pup efficiency. When the speed eaches /in, the pup efficiency is at its axiu value of 5.8%. Theeafte, the efficiency of the pup gadually deceases with the speed decease. At the pup highefficiency ate in the ange fo 46.74% to 5.8%, the coesponding centifugal pup opeates in the ange fo /in to 5/in. As shown in Figs. and, when the efficiency of the centifugal pup eaches the axiu value of 5.8%, the coesponding flow ate is. /h, which is vey close to the theoetical value of.7 /h Tie t(s) Figue. Output efficiency at a vaiable speed 5. CONCUION In this pape, a oto-flux vecto-contol stategy is used to analyze the dynaic popety of the induction-oto centifugal-pup syste unde vaiable otation-speed conditions. The siulation esults show the accuacy and stability of the oto-field-oiented vecto-contol stategy. The efficiency of the centifugal pup is analyzed, and the speed of the centifugal pup opeation at a high-efficiency ate is in the ange fo /in to 5/in. The attained esults povide the efeence values fo futhe eseach towads to ipoveent of the efficiency of the oto-pup syste. ACKNOWEDGMENT This wok was financed by the National cience and Technology uppot Poject of China (BAFB), the Young Coe Teache Poga of the Anhui Univesity (J56), and the Acadeic and Technology eades Ipoted Poject of the Anhui Univesity ((49)). The authos gatefully acknowledge HENG DA JIANG HAI Co. td. fo thei wok on the hydaulic-chaacteistics test. REFERENCE [] iu Hong, Zhai Qingzhi,. iulation study on iigation syste with vaiable fequency dive of wate pup, Jounal of China Agicultual Univesity, 9 (6), pp. -7, 4. [] hi Fengxia, Yang Junhui, Wang Xiaohui, Effect of otating speed on hydaulic enegy ecovey tubines pefoance, ACM. Applied Mechanics and Mateials pp. - 7, 4. [] Yang Hongyan, Hu Gejin, Copae the Dynaic Chaacteistics of Inlet and Outlet Thottle peed-regulating Hydaulic yste, ICMET. Advanced Mateials Reseach, Zhengzhou, China, 46, pp. 8-88,. [4] M.I. Jaheebacus, Flux Vecto Contol of an Induction Moto Dive fo Enegy-efficient Opeation of a Centifugal Pup, Poc. 5 IEEE Industial Engineeing and Opeations Manageen, Dubai, United Aab Eiates, pp. -5, 5.

8 XIWEN, YUIANG, GUOI, CHAO [5] Rashed, Mohaed, MacConnell, Pete F. A, tonach, A. Fase, Acanley, Paul, ensoless indiect-oto-filed-oientation speed contol of a peanent-agnet synchonous oto with statoesistance estiation, Autoation& Contol ystes, 54(), pp , 7. [6] E.Botoni, R.Aleida, A.Viana, Optiization of paallel vaiable speed diven centifugal pups opeation, Enegy Effic, (), pp. 67 7, 8. [7] F.J.T.E.Feeia, J.A.C.Fong and de A.T.Aleida, Ecoanalysis of vaiable-speed-dives fo flow egulation in puping systes, IEEE Tansactions on Industial Electonics, 58(6), pp. 7 5,. [8] ipson,angus R, Machi,Angela, Evluating the Appoxiation of the Affinity aws and Ipoving the Efficiency Estiate fo Vaiable peed Pups. Engineeing Mechanical, 9(), pp. 4-7,. [9] Keleen, Kathaina, chuch, Anna C, chuchann, Heike P, Influence of Flow Conditions in High-Pessue Oifices on Doplet Disuption of Oil-in-Wate Eulsions, CHEMICA ENGINEERING & TECHNOOGY, 7(7), pp. 7-4, 4. [] Handong Wang, Wate flow ate odels based on the pipe esistance and pessue diffeence in ultiple paallel chille systes, Enegy and Buildings, 75, pp. 8 88, 4. [] T.Ahonen, J.Tainen, J.Ahola, J.Viholainen, Estiation of pup opeational state with odel based ethods, Enegy Conves.Manag, 5(6), pp. 9 5, 5. [] W.V. Jones, Moto selection fo centifugal pup applications ade easy, Poc. IEEE Pulp and Pape Industy Technical Confeence (PPIC), Nashville, TN, United tates, pp.4-5,. [] Qinghui Wu, Xinjun Wang, Qinghuan hen, Reseach on dynaic odeling and siulation of axial-flow puping, Neuocoputing, 86, pp. 6, 6. Xiwen Guo eceived his B.c. and M.c. degees in Powe Electonics & Powe Dive fo the Anhui Univesity of cience & Technology in 5 and 8, espectively, and his Ph.D. degee in Electical Engineeing fo the Hefei Univesity of Technology in. ince, he has been a ectue with the chool of Electical Engineeing and Autoation of the Anhui Univesity of China. His cuent eseach inteests include design and analysis of the novel spheical actuato and its contol, powe electonics & powe dive, and oto-pup odeling. Yuliang Wu gaduated fo the Chuzhou Univesity of China in 5. He is cuently woking towads his M.c. degee at the chool of Electical Engineeing and Autoation of the Anhui Univesity of China. His eseach inteests include efficient coupling of the oto and pup. Guoli i eceived he Ph.D. degee in electical engineeing fo AIPP, Hefei, China, in 8. Cuently, she is a pofesso of the chool of Electical Engineeing and Autoation of the Anhui Univesity of China. He inteest is in electical & electonic engineeing and intelligent optiization techniques. Chao u gaduated fo the Anhui Univesity of China in 4. He is cuently woking towads his M.c. degee at the chool of Electical Engineeing and Autoation of the Anhui Univesity of China. His eseach inteests include intelligent optiization techniques and oto-pup odeling.