Introduction to permanent-magnet synchronous motor drive and brushless DC motor drive

• Motor types and section (SPMSM, IPMSM, SynRM?).• Governing equations.• Key parameters and variables measurements.’• Inverter-fed PMSM drives:

- (Sinewave PMSM + sinewave inverter): Complicated control scheme. - (Square-wave PMSM + square-wave inverter).- Hybrid: e.g., (Square-wave PMSM + sine-wave inverter).

• Control schemes and realized environments?• Filter between inverter and motor.• AC/DC front-end converter.

1

Motor types and selection

2

Some typical rotor structures of synchronous motors (SMs): (a), (b), (c) SPMSM; (d), (e), (f) IPMSM; (g) PMASynRM; (h) SynRM; (i) SRM.

(a) (c)

(f)(d)

(b)

(e)

S

N S

N

SN

S N

NS

NS N

S

NS

(g) (h)

q-axis

d-axis

q-axis

d-axis q-axis

d-axis

q-axis

d-axis

q-axis

d-axis

q-axis

d-axis

d-axis

N

S

N

SS

N

NS

NN

S

S

N

N

N

N

S

S

S

S

(i)

A

B

C

A

B

C

q-axis

N

N

S S

N

S

N

N

N

S

S

S

q-axis

d-axis

PMSM >> PMSM >> PMSMPMSM + RM >> + RM >> SynRMSynRM

• PMASynRM: Permanent magnet assisted SynRM

• SynRM: Synchronous reluctance motor

3

Some typical stator structures

(a) 如圖(a)，為salient pole，係集中式電樞繞組(Concentrated winding)之定子結構：具有短的end turns，相與相間之 coupling 較小，每一相之線圈不同時，與所有轉子磁鐵作用時，導致性能之降低。

(b) 如圖(b)，沒有slot (Slot-less)，故沒有齒隙轉矩(Cogging torque)，但線圈與後鐵間之熱導低，不利負荷之增加。又因沒有靜子齒，使得氣隙增長成轉子表面至後鐵，為維持適當大之PC值，磁鐵之長度須增長。

(c) 如圖(c)，為槽式用以容置分佈式繞組(Distributed winding) ，具有shoes在氣隙處，可減少氣隙磁導隨位置之變化，而減少Cogging torque。

3

4

Difference between square-wave and sine-wave BDCMs

SquareSquare--wave BDCM:wave BDCM:---- Rectangular distribution of airRectangular distribution of air--gap magnet flux;gap magnet flux;---- Rectangular winding current waveforms;Rectangular winding current waveforms;---- Concentrated stator armature winding. Concentrated stator armature winding.

SineSine--wave BDCM:wave BDCM:---- Sinusoidal or quasiSinusoidal or quasi--sinusoidal distribution of airsinusoidal distribution of air--gap magnet flux;gap magnet flux;---- Sinusoidal or quasiSinusoidal or quasi--sinusoidal winding current waveforms;sinusoidal winding current waveforms;---- QuasiQuasi--sinusoidal stator armature conductors, i.e., shortsinusoidal stator armature conductors, i.e., short--pitchedpitched

and distributed stator armature conductors. and distributed stator armature conductors.

If the stator winding current is not pure sine wave, and if the stator winding distribution is not purely sinusoidal, the time harmonics of the current can interact the space-harmonics of the conductor distribution to produce large torque ripple with only a slight increase of average torque.

A

A

BB

C

C

Concentrated armature winding(Square-wave motor)

Distributed armature winding(Sine-wave motor)

N

N

Three-phase armature currents

5

Speed servo drive (square-wave BDCM): not suited for lower operation speeds (a) Normally: concentrated armature windings. (b) Usually called BDCM.

Using photo sensorUsing photo sensorUsing Hall sensorUsing Hall sensor

Position servo drive: sine-wave BDCM(a) Normally: distributed armature windings.(b) Usually called PMSM..

SineSine--wave motor driven by squarewave motor driven by square--wave inverter:wave inverter:theoretical torque ripple at low speed >= 13%.theoretical torque ripple at low speed >= 13%.

Classification of BDCMs

6

7

signalsSwitching

ase

bsi

asi

bse

cse

csi

r

r

r

axisq

0 90 180 27090

)( 25 TT

)( 63 TT

)( 41 TT

BDCM PWM switching signal waveforms

1T 3T 5T

2T6T 4T

Sine-wave Square-wave

Ideal waveforms of Ideal waveforms of a Ya Y--connected connected BDCM with BDCM with flatflat--top back EMF.top back EMF.

NonNon--ideal windingideal windingcurrent and voltagecurrent and voltagewaveforms andwaveforms andcommutation commutation yielding torqueyielding torqueripple.ripple.

o120

B

CA

1 3 5

4 6 2

Vd+

−

dtdJBTT

TiePr

rLe

rekkmωω

ω

++=

=∑=

Non-conducting phase back-EMF

PMSMPMSM

Three-phase square-wave BDCM

8

Sine-wave BDCM Operation principle and commutation instant tuning

1T 3T 5T

4T 6T 2T

dcV

61 ~ TT

asi

bsi

csi

rθ

4πθ =r

Brushless DC Motors (BDCMs): PMSM with winding commutation according to the sensed rotor position.

9

10

Special application cases: The SPMSMs are also found in high-speed applications. However, some key affairs should be treated: (1) The permanent-magnet volume and thus the

back-EMF at the maximum speed must be properly determined.

(2) Inverter DC-link voltage must be properly set.

(3) The demagnetization risk in real operationmust be cared, especially for the positionsensorless controlled PMSM drive.

+

-

Inverter

Vd

Rectifier

EC

Mechanical load

~L −+ Ae

→Ai→di

~

~

n

Induction motor

Control

re ,T ω B,J

Δt,t,f cs

reTP ω≈

Three-PhaseAC

source

Effects of non-ideal current waveforms

)/( dtdJBTT rrLe ωω ++=

eL

Externalinductors

Coupler

⇒++=+= )/( dtdJBTTTT rrLehave ωω

rhavr ωωω +=

LeV

dtdi AdA −

∝Voltage boosting.Field-weakening.

Ah

Ah

hA

AAA Z

vZ

evi∞

=∑+

−≈

21

11AhA ii +≡ 1

affairs. cMechatroni )/( >>↓↑⇒ rhBJ ωThe coupler between motor and load, themechanical time constant, the ripple torque spectrum must be properly considered for the given mechanical load specifications.

)/(1 sA Lfi ∝δ

Cause ripple torque and extra armature copper losses.

The ripple current ↑⇒↑ losses switchingsf

The external filter between inverter and motor is needed for the case with high fundamental frequency and low switching frequency.

11

Experimental mechanism for making parameter estimation

SourcePower

AC

SW

deviceDriving

+ −

n

a

b

c

+

−

'n

IPMSM

rθrω

ase

asv

․Equivalent circuit parameter estimation: rotor is locked at a particular position andthe winding is excited with a variable-frequency and variable-current AC source.

․Slip test: the rotor is driven at a speed slightly different from synchronous speed. ․The voltage, current and power are recorded.․Back-EMF: measure motor open-circuit terminal voltages at different driven speeds.

永磁同步馬達之參數估測(Parameter estimation of PMSM)

12

換相時刻調整

相位校準及霍爾感測信號

機械對位調整

電氣對位調整

anv bnv cnv aH bH cH

霍爾位置感測信號相位調校之機構

anv

bnv

cnv

aH

bH

cH

調整後量測所得之感測馬達之開路端電壓

13

14

Per-phase equivalent circuit model

),,( fiR rθ ),,( fiL rθ

+

−

asv )(e rd ωasi

Back EMF constant estimation: rtd ke ω=

'mλ Flux linkage amplitude estimation:

(a) Considering the correct measurement; (b) observing the wave shape of the back EMF.

15

rBAlsasas LLLL θ2cos++=

)3

2(2cos πθ −++= rBAlsbsbs LLLL

)3

2(2coscscπθ +++= rBAlss LLLL

)3

(2cos21 πθ −+−== rBAbsasasbs LLLL

)3

(2cos21 πθ ++−== rBAcsasascs LLLL

)(2cos21 πθ ++−== rBAcsbsbscs LLLL

Winding inductances

Sensor

N

S

d- axis

q- axis

as-axis

bs-axis

cs-axis

as

bs

cs

Sensor

Sensor32

1

+

+

+

bsi

csi

asi

srcsv

asv

rθ

'as

'bs 'cs

rs

- -

-

bsbsLsLcsc

asasL

srbsvbscsL

ascsLasbsL

rω

n

n

a

b

c

(a)

(b)

16

Y-connected with non-isolated neutral

−

0=bsi0=csi

rθ

( )[ ] [ ]asrasasassasrBAlsassass i)(LdtdiricosLLL

dtdirvv θθ +=+++== 2

BAlsrasasasas LLLLL ++=== )0(max, θ

BAlsrasasasas LLLLL −+=== )5.0(min, πθ

min,max, 23,

23

asasdasasq LLLL ≈≈

),LL(LL BAlsq ++=23Δ

)(23Δ

BAlsd LLLL −+=

+

-

17

bsass vvv −= asbs ii −= 0=csi 0=rω

)( asrabasabs iLdtdiRv θ+Δ

sab RR 2=

)3/22cos(332)( πθθ −−+= rBAlsrab LLLL

bsi

−sv

asi

bsi

0=csi

asv−

bsv

a

a′

b

b′−

c

c′ rθ−

sv

asia

b

abs RR21

=

max,21

asbsq LL =

min,21 asbsd LL =

Y-connected with non-isolated neutral

18

Estimation of Key Motor Parameters: Example

PM Flux Linkage and Back EMF Constant .

rm'λ

ek

2ms

2V

ase

5ms

2V

ase

1000rpm

400rpm

• Three Y-connected resistors with reasonably high resistance ( ) are connected at the stator terminals to measure the motor phase back-EMF at no-load.

kΩ100

0=== csbsas iii

asrdrr

mras eEv ΔΔ′= θθλω cosˆcos

,ˆ

r

drmEω

λ =′

• Let the PMSM be driven at a constant speed with terminal open-circuited.

red kE ω=

Web,00858.0' =rmλ /krpmV81.3 rms=ek

Estimated parameters:

18

400

450

500

550

600

650

700

0 30 60 90 120 150 180 210 240 270 300 330 360

)( HLab μ

Hz745

Hz50

Hz100

Hz200

Hz300

)degrees(rθ

S-pole

N-pole

q-axis

• For simplicity, the parameters and are measured using off-the-shelf LCR meter (3532-50 LCR HiTester, HIOKI)

abR )( rabL θ

μH635.214)(2/1 min, == abd LL

Ω= 60625.0sR

Hz200=fEstimated parameters( ):

μH415.328)(2/1 max, == abq LL

• The parameters measured using LCR meter will not be accurate owing to its small-signal level excitation.

• The effects of inaccuracy and variations of motor parameters on the motor driving controlperformance will be handled by the proposedrobust control approaches.

19

Possible control schemes for BDCMs

Square-wave BDCM drive using direct duty ratio control(without current-mode control)

Without current control loops.Without current control loops.Simple implementation. Simple implementation. Lower driving performance. Lower driving performance.

T1 D1T3 T5

T4 T6 T2

D3 D5

D4 D6 D2

GT1 GT2GT3 GT4GT5 GT6

Vdc+

−a

bc

sensingposition Rotor

L

L

L

Rs

Rs

Rs

eas

ebs

ecs

BDCM

scheme estimationor

ias

ibs

ics Te ωr

n

N

Speedcontroller

Σ*rω

rω

+

−

Comparator

rθ

generator signal Switching

)(td

GT1

GT2

GT3

GT4

GT5

GT6

20

Measured results

ms5

A0.5

HA

asi

(a)

1GT

4GT

ms2

A0.5

HA

asi

(b)

1GT

4GT

Fig. 2.14. Measured waveforms of Hall sensor signal HA, motor linecurrent asi , the switching signals 1GT and 4GT of square-wave type BDCM drive with °120 conduction: (a) 1000rpm,

Ω= 7.32LR ; (b) 2500rpm, Ω= 7.32LR .

21

Sine-wave BDCM Operation principle and commutation instant tuning

1T 3T 5T

4T 6T 2T

dcV

61 ~ TT

asi

bsi

csi

rθ

4πθ =r

22

BDCM drive using sine-wave current-mode control (abc-domain)

*asi

acontv ,1T

4Ttrivasi

Currentcontroller

*bsi

bcontv ,3T

6Ttrivbsi

*csi ccontv ,

5T

2Ttrivcsi

Σ

rω

*rω *I

Currentcontroller

Currentcontroller

T1 D1T3 T5

T4 T6 T2

D3 D5

D4 D6 D2

Vdc+

−a

bc

sensingposition Rotor

L

L

L

Rs

Rs

Rs

eas

ebs

ecs

BDCM

scheme estimationor

ias

ibs

ics Te ωr

n

N

rθ

Speedcontroller

Current

generatorcommand

×*I

Unitcommand

0* =dsi

**ˆ qsiI =

23

Measured results

ms5

A0.5

HA

asi

(a)

1GT

4GT

*asi

ms2

A0.5

HA

asi

(b)

1GT

4GT

*asi

Fig. 2.16. Measured waveforms of Hall sensor signal HA , motor linecurrent asi and command *

asi , the switching signals 1GT and 4GT ofsine-wave type BDCM drive with current-controlled PWM switchingcontrol: (a) 1000 rpm , Ω= 7.32LR , (b) 2500 rpm , Ω= 7.32LR .

24

BDCM drive using robust sine-wave current-modecontrol with d-axis excitation control (dq-domain)

a

b

c

L

L

L

sr eas

ebs

ecs

PMSM

ias

ibs

ics

n

N

dcV

LT

eT rω+

−PMSG

T1 T3 T5

T4 T6 T2

dci

RL

EC

sr

sr

a,contv

1T4T

Robustcurrent

controllerbcontv ,

3T6T

triv

ccontv ,

5T2T

triv

Robustcurrent

controller

Σ

rω*rω

*qsi

)(sGcω

board control based-DSP

Hall

EC

HC HB, HA, PWM signals

rθ

mationtransfor

abc/dq−

'csi

'qsi

'asi'bsi

*dsi

'dsi rθ

trivd,contv

q,contvmationtransfor

dq/abc−

schemesectiondetspeedandpositionRotor

Fig. 4.3. Configuration of the CCPWM scheme in dq-domain. 25

Measured results

(a) ms2

A3

A3

asi

∗asi

qsi

∗qsi

A62.4

(b) ms2

A3

A3

asi

∗asi

qsi

∗qsi

A61.4

Fig. 4.12. Measured winding currents and commands due to a step speed command change ( , = 2700rpm 3000rpm) in dq-domain:(a) PI controller ( = 0); (b) robust controller ( = 0.9).

Ω= 6.21LR rω →W W

PI control only PI and robust controls

26

Measured results

(a)ms20

rpm100

rpm3000

rpm2700

9.0=W

5.0=W

onlyPI

(b) ms100

rpm100rpm3000

9.0=W 5.0=W

onlyPI

Fig. 4.13. Measured speed tracking and regulation responses in dq-domain by the PI controller and robust controller with different values of : (a) , = 2700rpm 3000rpm; (b) = 3000rpm,

WΩ= 6.21LR rω → rω

.6.219.43 Ω=→Ω= LL RR

27

dqtoabc

Reference frame transformation

⎥⎥⎦

⎤

⎢⎢⎣

⎡

⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢

⎣

⎡

+−

+−

=⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

csbsas

rrr

rrr

ros

rds

rqs

fff

fff

21

21

21

)3

2sin()3

2sin(sin

)3

2cos()3

2cos(cos

32 πθπθθ

πθπθθ

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢

⎣

⎡

++

−−=⎥⎥⎦

⎤

⎢⎢⎣

⎡

rs

rds

rqs

rr

rr

rr

csbsas

fff

fff

01)3

2sin()3

2cos(

1)3

2sin()3

2cos(

1sincos

πθπθ

πθπθ

θθabctodq

The sineThe sine--wave winding current can also be roughly obtainedwave winding current can also be roughly obtainedby applying SPWM voltage mode excitation:by applying SPWM voltage mode excitation:

Without current control loops.Simple implementation (however, how to realize SPWM schemes?). Lower current and thus torque dynamic performances. The driving performance can be improved via commutation instant shift(Example (Example IPMsIPMs: Toshiba:: Toshiba: TB6551 TB6551 sinesine--wave controller,wave controller, TB6581H TB6581H 33--Phase fullPhase full--wave wave sinesine--wave PWM brushless motor wave PWM brushless motor rriverrriver = TB6551 + = TB6551 + TPD4103AK highTPD4103AK high--voltage drivervoltage driver. .

positionangular absoluterotor =rθ

28

Some example commercialized sine BDCM drives

29

B. Standard Square-wave PMSM Driven Cooling Fan System Configuration and Commutation Signal Generation

iP

sR

sR

sR

sL

sL

sL

ase

bse

cse

N

1Q

2Q

3Q

4Q

5Q

6Q

dcP

asi

bsi

csiacv dcC dcV

contv

triv

*rω )(sGcωωε

cmv

β

rω′

1Q

2Q

3Q4Q

5Q6Q

1Q

2Q

3Q4Q

6Q

5Q

aHcba

HHHc

ba

HHH61 ~ qq

aciacP

30

Operating Performance

Low speed:

High speed:

rpm400* ≤rω

rpm2000rpm400 * ≤< rω

,22)(ss

KKsG Ipc +=+=ω

,62)(ss

KKsG Ipc +=+=ω

500ms

20rpmrω′300rpm

20ms

0.25A

asi′

(a)

aH

500ms

20rpmrω′2000rpm

5ms

1A

asi′

(b)

aH

*rω

*rω

(a)

50rpm

200ms

300rpm rω′

*rω

1Aasi′

50rpm

200ms

2000rpm rω′

*rω

1A

asi′

(b)

Standard Square-wave

31

對於一變頻器供電之交流馬達而言，雖然變頻器之PWM控制具有變頻變壓控制能力，但在變頻器之前端加裝一切換式整流器(Switching-mode rectifier, SMR)以建立直流鏈電壓，更具調壓彈性，可得良好之高速驅動特性，及提升入電之電力品質。(The equipment of SMR front-end: can provide well-regulated and boosted DC-link voltage to improve the operationperformance of a motor drive, particularly the high speed operations.)

變頻器直流鏈之電壓如為可調變一般稱為 (Pulse-width modulated, PAM)變頻器，藉由直流鏈電壓之調變可使方波變頻器之輸出成為近乎弦波。然而PAM之操控性能較差，僅適用於速度驅動。但如將PWM佐以PAM，可得較佳之控制彈性及性能。((PAM + PWM) >> can increase the controlflexibility and performance of a motor drive.)

+

-

Inverter

Vd

Rectifier

EC Load~

L −+ Ae→Ai→di

~

~

n

AC motor

Control

re ,T ω

reTP ω≈

sourceAC

phaseThree −

SMR Application examples: Front-end of motor drives

32

Some typical single-phase SMRs:(a) boost SMR; (b) buck SMR; (c) buck- boost SMR; (d) Ćuk SMR; (e) buck-boost cascade SMR; (f) boost-buck hybrid SMR; (g) flyback SMR; (h) isolated ZETA SMR.

acv

aci

(a)

acv

Load

aciS

(b)

Load

(c) (d)

acv

aciS

acv

aci

S

(e)

acv

aci

oC

(f)

(g)

acv

aci

acv

DoC

aci

S

(h)

acv

aciS

C

D1L

2L

oC oVoV

oV

oV

oV oV

oV

oVoC

oC

2L

L

2D

2S1D

1C1S

1L

L C

D oC

2L

D

2S

1S L 2D

1D

L

D

oC

oCS

DL

33

Flyback SMR (Flyback 切換式整流器)

Isolated buck/boost type

Perfect one-stagestructure

Lower rating

34