IEEE UK Chapter Seminar 15 December 3 Senorle PM Bruhle Drive Prof. D. Howe and Prof. Z. Q. Zhu The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Outline Review of enorle technique Zero-croing detection of bac-emf waveform 3rd bac-emf detection Flux oberver Rotor aliency Extended Kalman filter Deign of high-peed >1rpm BDC motor for enorle operation Vector control Flux weaening control Direct torque control The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Senorle Technique Why enorle? Reduced component count Improved reliability Eliminate mechanical/hyterei problem of dicrete enor Key conideration: Simple algorithm Accurate rotor poition etimate to dynamic load diturbance Robut to parameter variation The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Bruhle DC: Senorle Technique - Bac-emf zero croing detection - Third harmonic voltage detection - Freewheel diode approach -... Bruhle AC - Flux/poition oberver - Inductance variation - Kalman filter - The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Senorle Technique Exiting problem Senitive to parameter variation Poor performance at low peed Initial poition not identifiable May not wor at zero peed Rotor aliency baed approache Operational at zero & low peed Rotor aliency required Key iue: -two zero Zero croing of bac-emf waveform for BDC Zero peed for both BDC & BAC The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Typical Senored Bruhle Drive Sytem DC lin 3 Inverter 3 BAC machine DSP Poition enor Speed demand - Speed controller Current feedbac - Current controller Switching logic Speed etimator The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Typical Senorle Bruhle Drive Sytem DC lin 3 Inverter Meaurement from motor terminal 3 PM machine No enor DSP Speed demand - Speed controller Current feedbac - Current controller Switching logic Rotor Poition & Speed etimator Senorle controller The Univerity of Sheffield Electrical Machine & Drive Reearch Group
1 Detection of Zero-Croing of Bac-EMF Waveform emf ideal current waveform phae voltage detection point 3 6 9 1 15 18 1 4 7 3 33 36 Diode conduction angle current waveform Mot common technique for enorle operation of bruhle DC motor Appropriate witching device commutated 3 o elec. after detection of zerocroing of bac-emf waveform when phae i unexcited Conduction angle of free-wheeling diode mut <3 o elec. - may be problem at high peed or high load condition - not uitable for flux-weaening operation Starting and low peed operation problem due to abence of emf The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Detection of zero-croing of bac-emf waveform Example: Current.5A/div Voltage 5V/div Time.1m/div Phae Current Phae Voltage Meaured @1rpm Mode of operation: Initial alignment Synchronou open-loop run-up Senorle cloe-loop Variou commercial IC, e.g. - Micro-linear 445/446/448 Senorle PWM motor controller The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Deign of 1rpm high-peed motor for enorle operation Optimal deign: within ame pace envelope, maximum efficiency, diode conducting duration ignificantly <3 o elec. Motor A onger tator core Fewer turn/coil Shorter end winding More iron, le copper Relatively high unbalanced magnetic pull. Motor B Shorter tator core More turn/coil onger end winding e iron, more copper ower unbalanced magnetic pull The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Deign of 1rpm high-peed motor for enorle operation Motor A Motor B Sinuoidal bac-emf waveform ow diode conduction angle High conduction angle, almot continuou current waveform The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Deign of 1rpm high-peed motor for enorle operation Motor A Suitable for enorle control Motor B Unuitable for enorle control emf emf Zero-croing Phae terminal voltage No zero-croing Phae terminal voltage emf emf Zero-croing ine terminal voltage No zero-croing ine terminal voltage The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Senorle high-peed PM bruhle motor Current A 1.5 1.5 -.5-1 Meaured Predicted.1..3.4.5.6.7 Senorle control board -1.5 - Time Inverter connection board Current waveform on no-load, 15,rpm Heat in The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Pro & con of bac-emf zero-croing detection Simple, fat, commercial IC chip available Cae in which zero-croing of bac emf i not detectable: BDC - High peed operation high reactance BDC - High load BDC - Flux-weaening operation BAC - Bruhle ac operation Current i continuou or almot continuou Alternative enorle technique i required The Univerity of Sheffield Electrical Machine & Drive Reearch Group
3rd Harmonic Bac-EMF Detection 3 way of detecting e 3 in literature: u n,u hn,u h u n e3 E m 3 in 3 r u n u xn re K re K 1 rm t c The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Feature of 3rd harmonic bac-emf detection 3rd harmonic bac-emf can be extracted from voltage Only voltage u n i uitable for extracting 3rd harmonic bac EMF in both BDC and BAC drive Independent of motor operation mode Applicable to both BDC and BAC operation Open-loop tarting & cloe-loop operation a conventional bac-emf detection Mot uitable for high-peed application Example: 18 lot, 6 pole, urface-mounted magnet rotor, overlapping winding, 1 lot pitch ew The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Detection of 3 rd harmonic bac-emf - Voltage u n The Univerity of Sheffield Electrical Machine & Drive Reearch Group
BDC operation with/without commutation advance ow peed 3rpm, 4.6Nm; without advanced commutation, ad o High peed 195rpm,.5Nm; with advanced commutation, ad 45 o The Univerity of Sheffield Electrical Machine & Drive Reearch Group
BDC operation with/without commutation advance 5 5 Toque Nm 4 3 1 with optimal commutation advance without commutation advance optimal commutation angle 4 3 1 Optimal angle elec-deg. 5 1 15 Speed rpm The Univerity of Sheffield Electrical Machine & Drive Reearch Group
BAC operation with/without flux-weaening control ow peed 3rpm, 4.63Nm; without flux-weaening control High peed 1rpm,.7Nm; with flux-weaening control The Univerity of Sheffield Electrical Machine & Drive Reearch Group
BAC operation with/without flux-weaening control 5 optimal angle 1 Toque Nm 4 3 1 with optimal flux-weaening without flux-weaening 8 6 4 Optimal angle elec-deg. 5 1 15 Speed rpm The Univerity of Sheffield Electrical Machine & Drive Reearch Group
E Retriction of 3rd harmonic bac-emf detection B 3 m3 3 w3 3 p3 d 3 Abented Em3 B3 - Sinuoidal haped magnet, 1 o elec. pole arc magnet, Halbach magnetied motor p3 - Conventional 3 lot / pole BDC 1 o elec. coil pitch Reduced Em3 d3 - Ditributed winding 3 - Sewed winding/magnet ow peed, a conventional bac-emf baed technique B The Univerity of Sheffield Electrical Machine & Drive Reearch Group
3 Baed on rotor aliency Applicable to PM motor with rotor aliency interior and inet magnet rotor Winding inductance i rotor poition dependent I di V dt 1 di / dt Method 1: Inject high frequency ignal into motor terminal AC current component reulting from injected ignal i i in in i t in i t intantaneou difference between etimated rotor poition and actual rotor poition fed into oberver that update velocity and poition to force error to zero Method : Current variation from hyterei current PWM controller Inductance 1/ I/ t Icurrent variation over t tcurrent rie or decay time Rotor poition obtained from variation of winding inductance t The Univerity of Sheffield Electrical Machine & Drive Reearch Group
4 Flux oberver and rotor poition etimation Suitable for bruhle ac machine Baed on machine model Influenced by parameter variation due to temperature & aturation Speed obtained from differentiation of etimated rotor poition Filtering neceary 1. Voltage and current vector - meaured:. Stator flux-linage vector - oberved: 3. Excitation flux-linage vector - oberved: 4. Rotor poition - calculated: U &, I& t U& R I& dt Ψ Ψ& & Ψ& f r _ Ψ& I& ψ et. arctan ψ fβ fα The Univerity of Sheffield Electrical Machine & Drive Reearch Group
High pa filter to eliminate influence of DC offet on flux oberver Stator flux-linage vector t U& R I& dt Ψ Ψ& & time Flux locu without high pa filter Flux locu with high pa filter The Univerity of Sheffield Electrical Machine & Drive Reearch Group
ow pa filter on oberved excitation flux-linage vector Rotor poition - calculated from oberved excitation flux-linage vector With low pa filter: r _ et. ψ arctan ψ Smooth locu of flux-linage vector. Reduced ripple in etimated poition. Time delay in poition etimation. High frequency poition error till exit, caue ripple in etimated peed. fβ fα The Univerity of Sheffield Electrical Machine & Drive Reearch Group
ow pa filter on oberved excitation flux-linage vector Flux locu Etimated and meaured rotor poition Without low pa flux-filter High frequency ripple exit in flux locu arge poition error exit β-axi.5wb/div Rotor poition pule 4 3 1 actual poition etimated poition etimation error 1-1 - Error of etimated poition pule α-axi.5wb/div.1..3.4.5 Time With low pa flux-filter Smooth flux locu Significant phae hift exit β-axi.5wb/div Rotor poition pule 4 3 1 actual poition etimated poition etimation error 1-1 - Error of etimated poition pule α-axi.5wb/div.1..3.4.5 Time The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Speed etimation 1 - Differential of etimated rotor poition p d dt r _ et. r _ et. t r _ act. t r _ err. _et.: etimated value; _act.: actual value; _err.: error. t mall, r_act. mall comparable to error r_err. Comparion of Etimated and Actual Speed 4 4 3 3 Speed rpm Speed rpm 1 1 etimated peed actual peed etimated peed actual peed 1 3 4 5 Time 1 3 4 5 Senored operation Senorle operation Error in etimated poition caue ripple in etimated peed. Sytem maybe untable if etimated peed ued a feed-bac. Time The Univerity of Sheffield Electrical Machine & Drive Reearch Group
d 4 Speed etimation - Average peed etimation PF p r _ PF t et. Comparion of Etimated and Actual Speed 4 PF: low pa filter. time delay 3 3 Speed rpm Speed rpm 1 Time.5/div etimated peed actual peed etimated peed actual peed Senored operation Accurate etimation during teady-tate operation. Time delay in etimated peed during tranient operation. Sytem maybe untable if etimated peed ued a feed-bac. 1 1 3 4 5 Time etimated peed actual peed Senorle operation The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Speed etimation 3 - from induced EMF & excitation flux-linage E u m q Ψ Ri q f pi i q d E m e u q Ψ Ri f q i d pi q e u q Ψ Ri f q 4 Comparion of Etimated and Actual Speed no time delay 4 3 3 Speed rpm Speed rpm 1 1 etimated peed actual peed etimated peed actual peed 1 3 4 5 Time Senored operation No time delay in etimated peed. Sytem table if etimated peed ued a feed-bac. Etimation error even during teady-tate operation. 1 3 4 5 Time Senorle operation The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Speed etimation 4 - Improved etimation combined & 3 h d d 1 T e T 1 T 1 T dif. T 1 d d e com. d T T 1 dif. : difference of etimation. & 3.; com : compenation. Accurate peed etimation during teady-tate, h d. Fat dynamic repone to peed change, h e. Sytem table if etimated peed ued a feed-bac. The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Comparion of etimated and actual peed Senored operation Senorle operation 35 3 no time delay 4 5 3 etimated peed Speed rpm 15 1 actual peed Speed rpm 5 peed difference peed compenation 1-5 1 3 4 5 Time etimated peed actual peed 1 3 4 5 Time Accurate peed etimation during teady-tate, h d. Fat dynamic repone to peed change, h e. Sytem table if etimated peed ued a feed-bac. The Univerity of Sheffield Electrical Machine & Drive Reearch Group
5 Baed on Extended Kalman Filter EKF - An optimal recurive etimation algorithm for nonlinear ytem Application - High-accuracy etimate of non-linear ytem State variable current, peed from meaured terminal variable and machine model Model parameter influence of temperature on reitance and bac-emf, or aturation Eliminating meaurement noie combined tate oberver & filtering function Pro and con Pro Non-linear ytem Con: Computation requirement Parameter enitivity Initial condition particularly noie behaviour The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Extended Kalman filter only for illutration Non-linear dicrete model with white noie x 1 f x, u w y h x v I. Prediction tage - calculate tate at time 1 from thoe at time a State etimation neglecting noie x ˆ 1/ f xˆ /, u b Etimation of an error covariance matrix P T 1/ Γ P / Γ Q II. Correction tage filtering tage - correct etimation proce in recurive manner baed on deviation of etimated value from meaured value c Computation of a Kalman filter gain d Update of an error covariance matrix e State etimation K T [ P 1/ ] 1 T 1 P 1/ R [ I K 1 ] P 1/ P 1/ 1 [ y 1 h xˆ 1/ ] x ˆ 1/ 1 xˆ 1/ K 1 The Univerity of Sheffield Electrical Machine & Drive Reearch Group
The Univerity of Sheffield Electrical Machine & Drive Reearch Group Extended Kalman filter only for illutration inearization i required at each ampling interval,...,,, 1 u x f u x f u x f u x f N If Jacobian matrice are given by: / ˆ 1 1 1 1 1 1..................... x x N N N N N N x f x f x f x f x f x f x f x f x f Γ / ˆ, x x x i u x f Γ 1/ ˆ x x x i x h
The Univerity of Sheffield Electrical Machine & Drive Reearch Group Surface-mounted PM motor only for illutration λ λ λ α β β β α α β α J T n J D i i J n u i R u i R i i dt d p m p m m in co 3 co in I& β α a, d Ψ& f Ψ& ψ f α ψ f β r q I & V λ λ β β α α β α co in m m u i R u i R i i dt d Decoupled electrical and mechanical equation
The Univerity of Sheffield Electrical Machine & Drive Reearch Group Salient-pole PM motor only for illutration β α β α i i R R u u in co co in β α i i & & co in in co λ co in m β α β α i i R R R R R R i i in co co in co in in co 1 & & λ β α co in co in in co 1 u u m where q d q d αβ β α in co co where, d d axi inductance q q axi inductance
Comment on application to PM bruhle machine In addition to the tate oberver, uch a poition and peed It can be ued to etimate: Stator reitance and/or emf, for high temperature application Winding inductance, for better modeling of magnetic aturation oad torque and/or rotor inertia, to improve dynamic peed control It i till far too complicated to implement the full-order EKF oberver Hence, the reduced-order EKF i mot deirable The Univerity of Sheffield Electrical Machine & Drive Reearch Group
6 Example - Senorle DTC baed on implified EKF dψ Stator voltage equation: u Ri dt Stator flux linage vector obtained from meaured tator voltage and current: ψ u R i dt Thi equation can be expreed in tationary reference frame: ψ α u α Ri α dt ψ β u β Ri β dt Magnitude of tator flux linage: ψ ψ α ψ β Electromagnetic toque equation: 3 T p ψ aiβ ψ β iα The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Control trategy of DTC Bloc diagram of DTC for PM BAC drive The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Conventional approach: Senorle DTC dψ Stator voltage equation: u Ri dt Stator flux linage vector obtained from meaured tator voltage and current: ψ u R i dt Thi equation can be expreed in tationary reference frame: ψ α u α Ri α dt ψ β u β Ri β dt Etimated tator flux poition Etimated peed dt The Univerity of Sheffield Electrical Machine & Drive Reearch Group arctan ψ ψ α β d 1 T From DTC Need filter
The Univerity of Sheffield Electrical Machine & Drive Reearch Group Senorle DTC baed on implified EKF u Output variable α β ψ ψ y y 1 Input variable in co 1 1 v v y y For bruhle ac drive, fundamental of fluxe are inuoidal 1 w Fx x v x h y 1 1 1 1 T F in co x h T r w x ] ',, [ ˆ ˆ ˆ ˆ 3 1 co in in co K where 1,, and 3 are tuning parameter, and can be pre-computed from imulation, by uing, for example, the Matlab DQE command for Kalman etimator deign of dicrete-time ytem State variable State-pace model Kalman filter gain can now be ignificantly implified and i given by
The Univerity of Sheffield Electrical Machine & Drive Reearch Group Senorle DTC baed on implified EKF Simplified extended Kalman filter EKF baed enorle DTC: α β ψ ψ y y 1 Recurive Algorithm: ˆ in ˆ co 1 y y ε ] ˆ ˆ [ 1 ˆ 1 T r ε ' ˆ 1 ˆ w r r ε ' 1 ' 3 w w ε
Phae current and tator flux linage 3.75.5 Current A 1.5-1.5 Currnet 1.5A/div -.5-3.75..4.6.8 Time m a Phae current imulation.15 Time m/div c Phae current experiment.1 beta Wb.5 -.5 beta.5wb/div -.1 -.15 -.15 -.1 -.5.5.1.15 alfa Wb b ocu of tator flux linage imulation alfa.5wb/div d ocu of tator flux linage experiment The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Comparion of meaured and etimated peed Speed 1rpm/div Speed 1rpm/div With delay Time 1/div Etimated Meaured a Uing encoder for feedbac, etimated peed derived from tator flux-linage without peed filter Time 1/div Etimated Meaured b Uing etimated peed for feedbac, peed derived from tator flux-linage with peed filter Speed 1rpm/div No delay Time 1/div Etimated Meaured c Uing etimated peed for feedbac, peed derived from tator flux-linage by implified EKF The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Comparion of meaured and etimated rotor poition Poition 1 plue/div Error 1 plue/div Poition 1 plue/div Error 1 plue/div Meaured Etimated Error Meaured Etimated Error Time 1m/div Time 1m/div a Etimated directly from tator flux-linage b Etimated by uing implified EKF The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Acnowledgment Dr Jaon EDE Dr Jian Xin SHEN Mr Yan Feng SHI Mr Yong IU The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Speed and electromagnetic torque 4 35 3 5 15 1 5 Meaured peed Speed reference 1 3 4 5 6 7 8 Time a Speed imulation Meaured peed Speed reference Time 1/div c Speed experiment 1.4 1..8.6.4. -. -.4 -.6 1 Etimated torque Torque reference 1 3 4 5 6 7 8 Time b Electromagnetic torque imulation Etimated Torque Torque reference Time 1/div d Electromagnetic torque experiment The Univerity of Sheffield Electrical Machine & Drive Reearch Group
Comparion of meaured and etimated rotor poition Poition etimation: Since the electromagnetic torque can be etimated a: T p ψ i ψ i T r 3 a β 3 pψ [ψ r q in δ ψ 4d q 3pψ ψ r in δ T δ arctg 3pψ ψ δ r q β α for a urface-mounted permanent magnet BAC motor, d q Thu, d in δ ] The tator flux-linage poition i converted to the rotor poition by ubtracting the load angle, δ, that i Poition 1 plue/div Poition 1 plue/div Time 1m/div Time 1m/div Meaured Etimated Error a Etimated directly from tator flux-linage Meaured Etimated Error b Etimated by uing implified EKF Error 1 plue/div Error 1 plue/div The Univerity of Sheffield Electrical Machine & Drive Reearch Group