« FAULT TOLERANT CONTROL FOR 7 PHASE BLDC MACHINES

EMR’18

Hanoi (Vietnam)

June 2018

« FAULT TOLERANT CONTROL FOR 7 PHASE BLDC

MACHINES »

Duc Tan VU, Dr. Ngac Ky NGUYEN, Prof. Eric SEMAIL

L2EP Laboratory, Arts et Métiers ParisTech, Lille, France

Joint Summer School EMR’18

“Energetic Macroscopic Representation”

2

« Fault tolerant control for 7 phase BLDC machines»

EMR’18, Hanoi, June 2018

- Introduction -

1. Introduction

2. Role of EMR in the system design

3. Role of EMR in the system control

4. Biographies and references

A

B

C

DE

F

G

51,43°

7 phase BLDC machine developed by L2EP

EMR’18

Hanoi (Vietnam)

June 2018

« INTRODUCTION »

4



• Electrical machines are more and more interesting in many means of

transportation and also in electricity generation.

• Reliability required for the drives of on-board systems such as:

automotive, aircraft, marine propulsion, offshore wind-generator

- Introduction -

5



1. Decrease the phase current comparing to a three phase machine for a given low DC bus (48V) reduce the power-per-phase converter and machine rating.

2. Increase fault-tolerance capabilities (open-circuit and short-circuit).

3. Reduce torque ripples at low harmonics.

4. Different possibilities of stator winding configuration high speed range without flux weakening.

Multiphase machines

- Introduction -

Why ?

6



- Introduction -

1 1

dn nd d dk

k s k k k

k k

div v R i e

dt= =

= = + +

rrr r r

According to vectorial formalism, the voltage and electromagnetic torque

are expressed as:

Real n-phase machine TORQUE

TORQUE

L L

Fictitious Machines (diphase + homopolar)

Fictitious machines Shape of the back-EMF

(sinusoidal/trapezoidal or others)

T

1

dT 2

dT d

nT

7



- Introduction -

Real 7-phase PMSMTORQUE

Fictitious Machines (3 diphase + 1 homopolar)

Main

Machine

Second

Machine

h = 1, 13, 15, 27

h=7k ± 1

h = 5, 9, 19, 23,

h=7k ± 2

h = 7, 14, 21, …

h=7k

Notes

-Wye connection: current of homopolar machine.

i0=0 T0=0

-Symmetrical machines: there are no even harmonics of the back-EMF.

MM SM HM

Simplification

Third

Machine

TM

h = 3, 11, 17, 25, …

h=7k ± 3

Homo.

Machine

EMR’18

Hanoi (Vietnam)

June 2018

« ROLE OF EMR IN THE SYSTEM

DESIGN »

9



Equivalence of a 7-phase machine to

a set of 3 fictitious 2-phase machines

- Role of EMR in the system design -

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

DC busElectrical

coupling

Fictitious

machineLoad

Mecanical

coupling

+ = −

uuruur uuur uuur

M1M1 M1 M1 M1 M1

diR i L v e

dtM1 M1 M1e .i T .=

uuur uurM1 M2 M3T T T T= + +

+ = − Load

dF J T T

dt

SE SM

DC busElectrical

coupling Fictitious machinesMechanical

coupling Load

10



Basic original idea

Wye-coupled 7 phase machine

6 degrees of freedom:

control of the 3 2-phase

fictitious machines

In case of 1 open phase


control of only 2 2-phase

fictitious machines


In case of 2 open phases


control of only 2 2-phase fictitious

machines

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

11



0 1 3 5 7 9 11 13 15 17 19 21 230

20

40

60

80

100

Order of harmonics

Bac

k-e

mf

(%

)EXPERIMENTAL

3D-FEM

M2

M1

M3

0 1 3 5 7 9 11 13 15 17 19 21 230

20

40

60

80

100

Order of harmonics

Bac

k-e

mf

(%

)EXPERIMENTAL

3D-FEM

M2

M1

M3

First IDEA after EMR

representation

FOR the DESIGN:

Cancellation of

the fifth harmonic


TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

12



By the cancellation of the fifth harmonic of EMF

No torque produced by the fictitious M2 machine

even if supplied

Without changing modeling of the 7-phase machine

No torque ripples by change of M2 reference currents

Constant torque references for M1 and M3


1st CONCLUSION: the EMR is a tool for the drive design

EMR’18

Hanoi (Vietnam)

June 2018

«ROLE OF EMR IN THE SYSTEM CONTROL»

14



- Role of EMR in the system control-

• Especially, EMR is interesting for the definition of control strategies:

→Control in normal mode when the number of freedom degrees are

higher than the minimum (two currents are only necessary for a constant

torque):

– Minimization of Copper Losses

– Minimization of Peak Current

– Minimization of Peak Voltage

– Minimization of Losses under voltage constraints

– …

→Control in faulty modes also with optimization

EMR is also a tool for the design of the control!

We will focus on fault mode control

15



- Role of EMR in the system control -

Structure of the control thanks to EMR approach

Apply causal inversions to find the controller (IBC) of each element of the

structure

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

SE SM

16



- Role of EMR in the system design and control -

TREFTM2REF

TM3REF

TM1REF

KR

TREFTM2REF

TM3REF

TM1REF

KR

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

TREF

ΩREF

KR is distribution coefficient to determine which machine is used to generate torque

strategy

SE SM

17




iM1REF

iM2REF

iM3REF

iM1REFiM1REF

iM2REFiM2REF

iM3REFiM3REF

TREFTM2REF

TM3REF

TM1REF

KR

TREFTM2REF

TM3REF

TM1REF

KR

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

TREF

ΩREF

eM1lleM1ll

2

TM1REF.iM1REF =

strategy

SE SM

18




iM2dREF

vM2REF

vM2REFR(9)R(9)

R-1(9)R-1(9)

PIPI-+-+

-+-+iM2qREF

PIPI

iM2

iM2

iM2d

iM2q

++

++

++

++

eM2d eM2q

( )cosp sin p

Rsin p cosp

− =

strategy

iM1REF

iM2REF

iM3REF

iM1REFiM1REF

iM2REFiM2REF

iM3REFiM3REF

vM1REF

vM2REF

vM3REF

vM1REFvM1REF

vM2REFvM2REF

vM3REFvM3REF

TREFTM2REF

TM3REF

TM1REF

KR

TREFTM2REF

TM3REF

TM1REF

KR

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

TREF

ΩREF

SE SM

iM1dREF

iM1qREF

eM1deM1q

iM1α

iM1β

iM1d

iM1q

ϴ

vM1αREF

vM1βREF

19




iM1REF

iM2REF

iM3REF

iM1REFiM1REF

iM2REFiM2REF

iM3REFiM3REF

vM1REF

vM2REF

vM3REF

vM1REFvM1REF

vM2REFvM2REF

vM3REFvM3REF

TREFTM2REF

TM3REF

TM1REF

KR

TREFTM2REF

TM3REF

TM1REF

KR

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

TREF

ΩREF

2nd CONCLUSION: the EMR is a tool for a control design

strategy

SE SM

20



Experimental torques of the seven-phase machine

0 1 2 3 4 5 60

5

10

15

20

25

Order of harmonics

Torq

ues

(N

m)

normal mode (NM)

without modification (DM1)

with modification (DM2)

Spectral analysis of torques

In normal operation

In fault operation

Interaction between the non-symmetrical system

of currents and the symmetrical EMFs


1 opened phase fault

2

opened

phase

fault

To

rqu

es (

Nm

)

Time (s)

21



A

B

C

DE

F

G

51,43°


A

B

C

DE

F

G

51,43°

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14-5

-4

-3

-2

-1

0

1

2

3

4

5

Time (s)

Cu

rren

ts (

A)

iA

iB

iC

iD

iE

iF

iG

Curr

ents

(A

)

Time (s)

Strategy without

constrains on voltage

and current

22




Constraints on voltage and current?

Modified strategy

iM1REF

iM2REF

iM3REF

iM1REFiM1REF

iM2REFiM2REF

iM3REFiM3REF

vM1REF

vM2REF

vM3REF

vM1REFvM1REF

vM2REFvM2REF

vM3REFvM3REF

TREFTM2REF

TM3REF

TM1REF

KR

TREFTM2REF

TM3REF

TM1REF

KR

TM3

TM1

SMT

vM1

eM1

M1

M2

M3

iM1

iM2

iM3

vM2

vM3

eM3

eM2

TM2

iM1

iM2

iM3

SE

VBUS

iBUS

TLoad

m

TM3

TM1

SMSMT

vM1vM1

eM1eM1

M1M1

M2M2

M3M3

iM1iM1

iM2iM2

iM3iM3

vM2vM2

vM3vM3

eM3eM3

eM2eM2

TM2

iM1iM1

iM2iM2

iM3iM3

SE

VBUS

iBUS

TLoad

mm

TREF

Fault information

Modified Strategy

with constraints on

voltage and current

SE SM

2nd CONCLUSION: the EMR is a tool for a control design

23




7-phase

machine

7-phase

VSI+PWM

Optimization

Machine

parameters

Vmax ,Imax

Look-up table

Ω

Fault

information

VDC

T,H1,H2,H3,H4

and PI controller

θ

iabcdefg

d/dt

ic ie if ig Imaxid

Modified strategy with constrains

on voltage and current

D. T. Vu, N. K. Nguyen, E. Semail, and T. J. d. S. Moraes, "Torque optimization of seven-phase BLDC machines in normal and

degraded modes with constraints on current and voltage," in The 9th International Conference on Power Electronics, Machines and

Drives, Liverpool, UK, 4/2018.

24



- Conclusions -

• EMR provides tools for the machine design and also control design.

• It enables to have an overview as well as detailed elements of the

system.

Conclusions

EMR’18

Hanoi (Vietnam)

June 2018

« BIOGRAPHIES AND REFERENCES »

26



- Authors -

Dr. Ngac Ky NGUYEN

Arts et Métiers ParisTech, L2EP, France

PhD in Electrical Engineering at University of Mulhouse (2010)

Associate Professor since 2012

Research topics: Multiphase machines control, fault tolerance systems, EMR

Prof. Eric SEMAIL


PhD in Electrical Engineering at University of Lille 1 – Science and Technology (2000)

Full Professor since 2010

Research topics: Multiphase machines design and control, multi-converter modelling

Duc Tan VU


PhD student in Electrical Engineering

Research topics: Multiphase machines control, fault tolerance system, modelling

and control of multi-physique systems

27



-Conclusions and references-

[1] F. Locment, E. Semail, and X. Kestelyn, "Optimum use of DC bus by fitting the back-

electromotive force of a 7-phase permanent magnet synchronous machine," in 2005 European

Conference on Power Electronics and Applications, 2005, pp. 1-9

[2] F. Locment, E. Semail, and F. Piriou, "Design and study of a multiphase axial-flux machine," IEEE

Transactions on Magnetics, vol. 42, pp. 1427-1430, 2006.

[3] F. Jen-Ren and T. A. Lipo, "Disturbance-free operation of a multiphase current-regulated motor

drive with an opened phase," IEEE Transactions on Industry Applications, vol. 30, pp. 1267-1274,

1994.

[4] O. Fall, N. K. Nguyen, J. F. Charpentier, P. Letellier, E. Semail, and X. Kestelyn, "Variable speed

control of a 5-phase permanent magnet synchronous generator including voltage and current limits in

healthy and open-circuited modes," Electric Power Systems Research, vol. 140, pp. 507-516, 11/2016.

[5] D. T. Vu, N. K. Nguyen, E. Semail, and T. J. d. S. Moraes, "Torque optimization of seven-phase

BLDC machines in normal and degraded modes with constraints on current and voltage," in The 9th

International Conference on Power Electronics, Machines and Drives, Liverpool, UK, 4/2018.

[6] D. T. Vu, N. K. Nguyen, E. Semail, “Sensitivity of Torque Control for Seven-phase BLDC

Machine with One Opened Phase under Constraints on Voltage and Current”, the 24th edition of the

International Symposium on Power Electronics, Electrical Drives, Automation and Motion, Amalfi,

Italy, 6/2018.

References

28



THANK YOU FOR YOUR ATTENTION!

29



• Smooth torque in fault mode operation (two open phases)

Why seven phases ?

A

B

C

DE

F

G

51,43°

• Using the third harmonic of back-EMF for the torque

jsB1jsB2

jsB3

jsA1

jsA2

jsA3

30

°

6-phase

i1

v1

i5

i2

ik

v2

vn

vk

N

S(k-2)

5-phase 7-phase

• Reasonable number of connections

- Introduction -

Documents

« FAULT TOLERANT CONTROL FOR 7 PHASE BLDC MACHINES