Maximum Control Structure of a Series Hybrid Electric Vehicle by dla17169


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									                 Maximum Control Structure of a Series
               Hybrid Electric Vehicle using Supercapacitors

                      W. Lhomme, Ph. Delarue, Ph. Barrade, A. Bouscayrol


The main problem with Hybrid Electric Vehicles (HEV) is the management of batteries. We suggest to
replace the batteries by an energy storage system made of supercapacitors on a series HEV with two
traction drive. A Maximum Control Structure (MCS) of such an HEV is presented to organize the
control of the different subsystems. MCS is based on specific inversion rules of Energetic
Macroscopic Representation (EMR). This methodology leads to a global model of the system and its
deduced control. Moreover, this enable to identify precisely the maximum control for the chopper
associated with the supercapacitors. The simulation of an Extra Urban Driving Cycle (EUDC) is

Keywords: Series HEV, Supercapacitor, Modelling, Control System, Simulation.

1       Introduction
The ecosystem and environmental protection becomes a challenge for car manufacturers. Many works
are made today in order to design vehicles with zero emission. The electric vehicle carries out well this
task but with a too weak autonomy. Regarding the thermal vehicle, pollution and consumption are the
main drawbacks but with the advantage of a strong autonomy. This is the reason why manufacturers
prefer to move towards an alternative solution, the Hybrid Electric Vehicle (HEV) [1], [2]. As an
example, we can quote Toyota (Prius), Honda (Insight), Renault (Kangoo), Ford (Maverick), Nissan
(Tino) [3], [4].

For most of the marketed hybrid vehicles, the main electrical source is made of batteries. The vehicle
studied in this paper uses supercapacitors instead of batteries. The main reason is that these new
storage elements are defined with power densities compatible with the requirements of an HEV, with a
number of charge/discharge cycles considerably increased compared to batteries. However, the energy
density of supercapacitors is still lower than the conventional batteries. But as the target in using a
storage element in HEV is not necessarily to store energy, but mainly to provide or absorb the peak
power from the traction system, supercapacitors appear to be well dedicated [5], [6].

In order to control these multi-source systems (thermal engine, supercapacitors, electrical motors), the
energy flows coming from each element have to be managed. The Energetic Macroscopic
Representation (EMR) has been developed to propose a synthetic description of electromechanical
conversion systems. A Maximal Control Structure (MCS) can be deduced by from EMR using
inversion rules [7].

In this paper, specific strategies are carried out to manage the energy exchange between the
components of the series Hybrid Electric Vehicle (HEV) with two traction drives. The control is made
with an Extra Urban Driving Cycle (EUDC), using Matlab-SimulinkTM software.
2          Modelling of the studied series Hybrid Electric Vehicle
2.1        The studied architecture
The studied architecture is a series HEV with two traction drives (Figure 1). Two machines thus
replace the standard case with a single machine and a differential mechanical. The storage element of
these traction systems is chosen to have a fast storage, an important number of cycles and a large
lifetime. The battery, electrochemical accumulator used many manufacturers, has as disadvantage not
to have these characteristics, by thus decreasing the performances of the vehicle.

Nowadays two technologies allow respecting the conditions quoted above: supercapacitors and
flywheels [8]. In this paper the studied vehicle use supercapacitors. The Internal Combustion Engine
(ICE) is a spark ignition engine of 1700 cm3.

The series HEV is composed of four parts (Figure 2). Part 1 is called thermals/electric transmission. It
realises a conversion from a thermal energy via the ICE to electrical energy by the generator (G) and
the rectifier. Part 2 corresponds to the storage subsystem. It is made of supercapacitors (Scaps), an
inductor (L) and a chopper. A braking chopper (TB and RB) is set up (part 3) in the case where the
supercapacitors could not store energy anymore. Part 4 represents the traction subsystem. It is made of
two induction machines (Mr and Ml), two inverters, two wheels and two gearboxes. A capacitor (C) is
needed for the main DC bus which links all four parts.
2.2        EMR of the series HEV
The EMR is a synthetic graphical tool based on the principle of action and reaction between connected
elements [9]. Each of these components can be internally described by transfer functions, state models,
causal ordering graphs, or other more precise modelling tools. The energy distribution is obtained by
specific elements, which link several upstream and downstream, drawn by interleaved pictograms (see

The EMR of studied system (Figure 3) is deduced from work already realised on the series HEV but
without supercapacitors and with DC machines instead of AC machines [10].

Modelling of the tank and ICE – The modelling of ICE is made very simply. Admission of the fuel
and combustive is not represented. An equivalent chemical source will correspond to the gas mixing of
these chemical species (green oval pictogram CSeq on Figure 3). The spark ignition engine is regarded
as an element of conversion transforming a calorific energy into mechanical energy with for
adjustment entry, the inlet valve of mixing, a (orange hexagon pictogram on Figure 3). Models much
more complicated make it possible to represent the thermal engine more finely [11].

Modelling of the shaft – The shaft connecting the thermal engine to the induction generator stores a
kinetic energy. This energy is due to an energy accumulation of the kinetic variable Ωshaft, the speed of
the thermal engine and the generator. This speed is thus produced from an interaction between the
engine and generator torques, Tice and Tig:

    dW shaft                                                                                       (1)
J              + f W shaft = Tice - Tig

Where f and J are the friction coefficient and the inertia moment of the shaft. As the shaft induces the
state variable Ωshaft, it has to be represented by an accumulation element (orange rectangular pictogram
with an oblique bar).

                                 Electric                               ~                                                                     =                            Electric
                                Generator                                    =                                                                    ~                        Machine

                                                                                                                                              =                            Electric
                                                                        =                                                                         ~                        Machine
                     Bank                                                    =

Figure 1. Synoptic of studied architecture

                                            Induction                                                                                             Electric                                                                       Induction
  Tank         ICE             Shaft        Generator                        Rectifier                                  Capacitor                 Coupling                                   Inverters                           Machines                            Wheels

                                                                                                                            irect icoup           iinv
                                                   1                                                                                                                   iinv_l                                                                                       4
                              Tice Tig                       src11           src21                     src31                                                           sin11_l          sin21_l                 sin31_l                           T im_l
                                              G                                                                                                   uC                                                                                      Ml                  Tgear_l
                               Wshaft                                                                                         iC                                                                                                               Wgear_l
                                                             src12           src22                     src32                                                           sin21_l          sin22_l                 sin32_l
                 a                                                                                                                           icoup2
                                                                             2                                     scS1                                               sin11_r           sin21_r                 sin31_r                           T im_r            vvehic              Fres
                                                                                     iL            L
                                                                                                                                           i RB                                                                                          Mr                   Tgear_r
                                                                     Scaps                                                                RB                                                                                                   Wgear_r
                                                                                                                   scS2                                               sin21_r           sin22_r                 sin32_r
                                                                                           uScaps                                          3

                                                                     Supercapacitor                                Scaps                      Braking                                                                                             Gearboxes Environment
                                                                         Bank                                     Chopper                     Chopper

Figure 2. Components of studied architecture

                                         Induction                                                                  Supercapacitor Bank                               Electric                                  Induction         Gearboxes
 Tank      ICE         Shaft             Generator               Rectifier           Capacitor                     and dissipation resistor                           Coupling         Inverters                Machines          and Wheels               Vehicle              Environment

                                                                                                                                                                                                       uinv_l      iim_l         Tim_l         Ft_l

                                                                                                                                                                           uC                           iim_l       eim_l       Wgear_l
                                                                                                                                                                                             sinv_l                                            vvehic
                 Tice         W shaft        eig       iig                       irect                      uC                                        uC                                                                                                       Ft            vvehic
 CSeq                                                                                                                                                                                                                                                                                       MS
                     Wshaft     Tig           iig      urect                      uC                            icoup                                    iinv                                                                                                  vvehic        Fres
           a                                                srect                                                                        uC                                            uC              uinv_r       iim_r        Tim_r         Ft_r
                                                                                                                          icoup2                                           iinv_r

                                                                                                                        ichopS                 uC                                                       iim_r       eim_r       Wgear_r           vvehic
                                                                                         uScaps            iL                                               uchopB
                                                                                   ES                                              uC                                 DS                        sinv_r
                                                                                           iL          uchopS                             ichopB                iRB
                                                                                                       schopS                                 schopB

                                 Tig_ref     iig_ref     urect_ref                                     uchopS_ref                                                                                     uinv_r_ref    iim_r_ref     Tim_r_ref
                        W shaft _ref                                                                                                                                  uScaps          sinv_l
                                                        uScaps                                                                                       kRE                                                                                                            Ft_ref          vvehic_ref
                                            PM                                                                                                                        Ptract
                                                        Ptract                                    iL_ref                 ichopS_ref
                              Tice_ref                                                                                                                                                                uinv_l_ref    iim_l_ref     Tim_l_ref Ft_l_ref                          kRF = 0,5

 Source          EMR
                                                                                  uC_ref                          icoup_ref
Strategy         MCS

Figure 3. EMR and MCS of studied architecture
Modelling of the induction machines – The studied machines (generator included) are squirrel-cage
induction machines. These are represented in EMR pictogram by two distinct blocks: an element of
energy accumulation for the equivalent stator windings of the machines and an electromechanical
converter (orange circle pictogram). The inputs are the converter voltages (rectifier or inverter)
u conv = [uconv13 , uconv23 ]T and the shaft speed Wshaft; and the outputs are the machine currents (generator
or motor) i im = [iim1 , iim 2 ]T and the machine torque Tim. The equations and explanations of this
representation are presented in [12].

Modelling of the rectifiers, inverters and choppers – Rectifiers, inverters and choppers are an electric
converter (without energy accumulation). They are then represented as elements of electric conversion
(orange square pictogram). The relationships of the rectifier are:

ì         éu rect 13 ù é src 11 - src 31 ù           é mrect 1 ù
ïu rect = ê          ú = ês              ú uC = ê m            ú uC = m rect uC
ï         ëurect 23 û ë rc 21 - src 31 û             ë rect 2 û                      ìm Î {- 1;0;1}     (2)
í                                                                               with í
ïi = [s - s                                   éiig 1 ù
                            src 21 - src 31 ] ê ú = mT i ig                          îs Î {0 ;1}
ï rect     rc11       rc 31
                                              ëiig 2 û

With mrect is the modulation vector, s is the switching function, uC is the capacitor voltage, iig and urect
are the currents and voltages of the induction generator, and irect is the rectifier current.

For the simulation, a mean value modelling (averaged model) can be deduced from this discrete
modelling in order to reduce the computation time for simulations. In this case, the modulated voltages
and currents are replaced by their averaged values during the modulation period, as the modulation
and the switching functions:

ìs Î {0 ;1}        ì s Î [0;1]
ï                  ï
ím Î {- 1;0;1} Þ í m Î [- 1;0;1]
ïu Î {- u ;0 ; u } ï u Î [- u ;0; u ]
î         C     C  î         C     C

The modelling of the inverters and choppers are made the same manner as above.

Modelling of the DC bus capacitor – A capacitor stores potential energy. It is represented by
accumulation element whose state variable is the DC bus capacitor voltage. This voltage depends of
the current delivered by the rectifier irect and of the current coming from the traction parts and
supercapacitors icoup:

         duC uC                                                                                         (4)
iC = C       +    = irect - icoup
          dt   rC

Where C is the capacitor and rC the parallel resistor of the capacitor

Modelling of the filter inductor – An inductor stores kinetics energy. It is represented by
accumulation element whose state variable is the filter inductor current. This current depends of the
voltage delivered by the supercapacitors uScaps and of the output voltage of chopper uchopS:

         diL                                                                                            (5)
uL = L       + rL iL = uchopS - u Scaps
Modelling of the supercapacitors – There are many models representing the operating features of a
supercapacitor. However, for the majority of the studies, the model of Zubieta and Bonert can be used
[13]. This model takes into account a non-linear equivalent capacity (Co and Cu on Figure 4), the load
losses when the supercapacitor is not any more solicited (Rl), the fall of tension during the phases of
load and discharge (Rs), and relaxation phenomenon (R1, C1; R2, C2; …; Rn, Cn). To characterise the
supercapacitors of other models much more complicated exist [14]. But for the traction applications
the model of Zubieta and Bonert is sufficient. Besides, the load and discharge frequencies being
enough weak in this application type, the relaxation phenomenon can be neglected. The
supercapacitors are represented by an electric source (ES on Figure 3 and Figure 4) having for input
the filter inductor current and for output the components voltage.


     il       Rs               R1      R2                       Rn
    Rl                                                                 uScaps                      ES
               Co             Cu      C1       C2              Cn

Figure 4. Model of the supercapacitors

Modelling of the braking resistor – The braking resistor is solicited if the supercapacitors cannot store
energy any more. Resistor dissipates the excess of energy due to the vehicle deceleration. Its
representation can thus corresponds to a dissipative source (DS on Figure 3) of energy (copper losses).

Modelling of the electric coupling – For such a system, one takes note a great number of couplings:
- Electric coupling (overlapped orange square pictogram) between the thermals/electric
  transmission part, the supercapacitor bank, the braking resistor and the traction part of the vehicle.
  This coupling can be divided in two sub-couplings. This enable to visualise directly the energy
  flux between the braking resistor and the supercapacitor bank:

ìicoup = iinv - icoup 2                                                    ìicoup 2 = ichopS + ichopB
í                                        (6)                               í                                        (7)
îu coup = uC                                                               îu coup 2 = uC

-        Electric coupling between the two inverters of the induction machines:

ìiinv = iinv _ l + iinv _ r                                                                                        (8)
îu inv = uC

Where icoup, ucoup, icoup2, ucoup2, iinv, uinv, iinv_l, iinv_r, ichopS and ichopB respectively represent the currents and
the voltages of the electric coupling 1 and 2, the current of the electric coupling between the inverters,
the voltage and the currents of the inverters, the current of supercapacitors chopper and the current of
braking chopper.

Modelling of the gearboxes and wheels – Modelling of wheel and gearbox are carried out in a
classical way. These elements of mechanical conversion can be brought back in only one, are
equivalent with:
ìvvehic = Rwhe W whe = Rwhe r W gear
ï           Tgear   h gear                                                                             (9)
ïFt _ whe = R     =
                    r Rwhe
î             whe

Where r, hgear and Rwhe designate the speed ratio and the efficiency of the gearbox and the radius of the
wheel. Tgear, Wgear, Tim, Wwhe, vvehic, Ft_whe respectively represent the torque and the angular speed of the
gearbox, the torque of the induction machine, the angular speed of the wheel, the linear speed of the
vehicle and the force of traction developed by one wheel.

Modelling of the vehicle – The wheel/road contact is neglected, one can represent the mass of vehicle
by an equivalent mass Meq. The chassis of potential energy is modelled by an element of energy

        dvvehic                                                                                       ( 10 )
M eq            = Ft - Fres

With Ft the sum of the two forces of traction developed by the left and right wheels Ft_l and Ft_r
represented by a mechanical coupling (overlapped double triangle pictogram) with:

ìFt = Ft _ r + Ft _ l                                                                                 ( 11 )
îvl = vr = vvehic

Where vl, vr are the linear speeds of the left and right wheels.

Modelling of the environment – The external environment is represented by a mechanical source
(MS on Figure 3) leading to the resistance force to the motion of vehicle Fres (aerodynamic forces of
resistance, resistance forces of bearing, gravity forces, …).

3          MCS of the series HEV
From the EMR of a system, one can deduce a control structure, which is composed of the maximum of
control operations and measurements. Continuous lines are associated with the inversion of action
variables while dotted lines are related to the rejection of disturbance variables. All control blocks are
depicted by blue parallelograms because they handle only information (see Appendix). The bottom of
Figure 3 gives the MCS of the studied system. This MCS is composed of several inversion blocks and
two different management parts. In this section, parts 2 and 3 of Figure 2 are detailed. Parts 1 and 4
are already detailed for other applications [10]. Finally the strategy block for the thermal engine
control is presented.
3.1        MCS of the supercapacitor bank and the braking resistor

3.1.1      Control of the supercapacitor bank
In order to manage the system, the voltage of the DC bus must have a constant value. Moreover the
current delivered by the supercapacitors has to be kept in given limits to ensure a high efficiency. A
main difficulty is that the supercapacitor chopper is a two quadrants DC/DC converter, only reversible
in current. There is then only one degree of freedom (connection function of the chopper) to control
DC bus and to control the current in the supercapacitors. From these requirements, the chopper control
is determined by direct inversion of EMR (Figure 3 and Figure 5).
3.1.2      Control of the braking resistor
When the braking resistor system is active, the supercapacitors are disable. The constraint to control
the voltage of the DC bus is not carried out any more by the supercapacitor chopper. Thus the braking
chopper must carry out the DC voltage. The constraint being uC and the freedom degree of the system
the connection function of the braking chopper schopB, the MCS is deducted (Figure 3 and Figure 5).
3.1.3      Global control
As presented in the previous sections, the modelling of the electric coupling between the
thermals/electric transmission, the supercapacitors, the braking resistor and the traction part are
divided into two parts. For the first coupling, its inversion is directly made by the measurement of the
current in the traction part. But with regard to the second coupling, a repartition criterion of energy kRE
between the supercapacitors and the braking resistor must be set up in order to distribute correctly the
energy flows that occur in such a system:

ìichopB _ ref = k RE icoup 2 _ ref                                                                       ( 12 )
îichopS _ ref = (1 - k RE ) icoup 2 _ ref

By acting on kRE, we can active both subsystems:

-     if the traction power Ptract is negative and the voltage uScaps is maximum, then the dissipation
      chopper is activated (kRE = 1),

-     if the voltage uScaps is not to its maximal value, the supercapacitor chopper is activated for any
      traction power (kRE = 0).

In order to initiate the reader with EMR and MCS, a detailed representation of the control
supercapacitors chopper and braking resistor is shown by using bloc diagrams (Figure 6).
3.2        Management part of the ICE
The ICE control in a series hybrid vehicle depends primarily on the state of charge of the storage
system [15]. The strategy block of Power Management (PM on Figure 3) enables to fix the references
of the speed and torque of the thermal engine:

-     if the traction power Ptract is positive and if the voltage of the supercapacitor uScaps is lower or equal
      to 70% of its maximum value, then the ICE is activated,

-     if the traction power Ptract becomes negative or if the voltage of the supercapacitor uScaps reaches
      90% of its maximum value, then the ICE is off.

There are control strategies much more complicated for the HEV. As example, we can quote the
vehicle load prevision HEV by a recurrent neural network [16].
 iL_mea        uScaps_mea                                          schopS _ ref                                         schopB _ ref
                                                                                       uC_mea                                             iRB_mea

                                       uchopS_ref                                                        ichopB_ref


    uC_ref                                         icoup_ref                                               iinv_mea

Figure 5. MCS of the control supercapacitors bank and braking resistor

 iL_mea                                                            schopS _ ref                                           schopB _ ref
                                                                                  uC_mea                                                  iRB_mea

         +     –            uL_ref +    +        uchopS_ref                                                ichopB_ref
                                                                      %                                                      %
                        %                                              1
                                ichopS_ref                     –

    uC_ref +       –           iC_ref –      +            icoup_ref                                      iinv_mea
                                                                                  –      +

Figure 6. Bloc diagrams of the supercapacitors bank and braking resistor control

4             Simulation results
Simulations are carried out for an Extra Urban Drive Cycle (EUDC) on the Matlab-SimulinkTM
software. This is a European cycle test, which is useful for measurement of pollutants and
consumption [4]. The number of supercapacitors is deduced from a first cycle, the Urban Drive Cycle
(UDC). The number of supercapacitors used for this application is 62 units of 2’600 F. This
corresponds to a volume of 26 l for a weight of 32.5 kg (without power electronics interface).

In order to avoid too frequent start and stop processes for the thermal engine, a main criterion is to
stop this one when the voltage of bank is 90% of its maximum value. The phases of starting decreased,
this will allow less to consume and less to pollute.
As power requirements are very strong for an EUDC, the thermal engine has to provide a consequent
power. The ICE is then designed and controlled for two operating points, corresponding to two
different powers. The first one (low power) delivered by this engine corresponds to an urban operation
(low speed). The second one (strong power), it corresponds to an EUDC of motorway type (strong
speed). These operating points are chosen so as to have the best efficiency on the thermal engine.

For the speed profile of the vehicle (Figure 7), the terminal voltage of the supercapacitors fluctuates
between its maximum value and 70% of the maximum value (Figure 8). The ICE has to provide a
supplement of energy at constant power according to the power required and thus re-fills the
supercapacitors (Figure 9). The braking energy is very high at the end of the cycle: as the
supercapacitors bank cannot absorb such an energy, the braking resistors system is turned on
(Figure 10). In order to work at high speed without increasing the DC bus voltage uC, the electrical
machine fluxes is reduced (Figure 11). The DC bus voltage uC is well controlled (Figure 12).

         vvehic (km/h)                           150                                                   Wshaft
100                                                                                              400
                                                 100                                             300
                                                                     uScaps (V)
 50                                                                                              200
                                     t (s)                                              t (s)                         t (s)
    0                                              0                                               0
     0      100      200          300      400      0          100       200      300      400         0        100       200   300      400
 Figure 7. Linear velocity of the                          Figure 8. Voltage of the              Figure 9. Angular velocity of the
             vehicle                                         supercapacitor bank                              ICE

    1                                             1.1                                            900
                                                                                                           uC (V)

0.5                                              0.56
                                                               F R (Wb)                          860

                                                                                        t (s)    840
                          t (s)                                                                                                       t (s)
    0                                                  0
     0      100     200           300     400              0    100       200     300      400         0        100       200   300      400
Figure 10. Averaged duty cycle                      Figure 11. Rotor flux of an                   Figure 12. Voltage of the DC
    of the braking chopper                              induction machine                                     bus

5          Conclusion
A complex control is suggested for a series HEV, using supercapacitors. This control is obtained from
the inversion of the system model using a synthetic representation. This method leads to define blocks
of strategies for managing the energy flows between the various elements. Simulation results have
been obtained for an extra-urban drive cycle.

This work shows also that the use of supercapacitors bank instead of batteries can be possible for the
hybrid vehicles. Indeed their cost in strong decrease and their lifetime are indicators of
competitiveness. The energy density is still low, but if power density is the main criteria, one can think
that the weight and volume are not prohibitory, in spite of electronic associated. Nevertheless, studies
for the reliability of such system, together with their integration in HEV have to be realised to
demonstrate it. The best compromise at the moment would be to use the battery and supercapacitors.
Appendix: Synoptic of Energetic Macroscopic Representation

                                    Mechanical source         Chemical source of
   ES       source of          MS                        CS
                                    of energy                 energy

            Dissipative             Electrical                Electromechanical
            source of               converter                 converter (without
            energy (copper          (without energy           energy
            losses)                 accumulation)             accumulation)

                                    Mechanical                Element with
                                    chemical converter        energy
                                    (without energy           accumulation

            Electrical                                        Control block
            coupling                                          with coupling
                                    (distribution of
            (distribution of                                  criterion
            electric energy)

            Control block           Control block
            without                 with                      Strategy block
            controller              controller
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          Walter Lhomme, Ph.D. student
          Laboratory of Electrical Engineering (L2EP)
          University of Sciences and Technologies of Lille, France (USTL)
          Phone: +33 3 20 43 42 80, Fax: +33 3 20 43 69 67,

          W. Lhomme received the Master degree from USTL. Since September 2004, he has
          been a Ph.D. student at the L2EP, USTL. His research fields are energy management
          of Multi-machine Multi-converter Systems, application in hybrid vehicles.

          Philippe Delarue, Assistant Professor
          Laboratory of Electrical Engineering (L2EP)
          University of Sciences and Technologies of Lille, France (USTL)
          Phone: +33 3 20 43 49 06, Fax: +33 3 20 43 69 67,
          Ph. Delarue received the Ph.D. degree from USTL, France, in 1989. Since 1991, he
          has been engaged as assistant Professor at Polytech’Lille (Ecole Polytechnique
          Universitaire de Lille) and at L2EP. His main research interests are power
          electronics and multi-machine systems.

          Philippe Barrade, First Assistant
          Laboratory of Industrial Electronics (LEI)
          Federal Ecole Polytechnique of Lausanne (EPFL)
          STI-ISE-LEI, CH-1015 Lausanne, Switzerland
          Phone: + 41 21 693 26 51, Fax: + 41 21 693 26 00,
          In 1997, Ph. Barrade received the Ph.D. degree in Electrical Engineering from INP,
          Toulouse, France. In 1998, he was working at SAFT, in the field of power
          electronics and energy management for UPS applications. Since 1999, he has been
          First Assistant, Lecturer at EPFL, Switzerland. His main research fields are power
          electronics applications, energy management and storage.

          Alain Bouscayrol, Assistant Professor
          Laboratory of Electrical Engineering (L2EP)
          University of Sciences and Technologies of Lille, France (USTL)
          Phone: +33 3 20 43 42 53, Fax: +33 3 20 43 69 67,
          A. Bouscayrol received the Ph.D. degree from INP Toulouse, France, in 1995. Since
          1996, he has been engaged as assistant Professor at the L2EP of the USTL. He
          received the "Habilitation à Diriger des Recherches" degree from the USTL in 2003.
          His research interests include electrical machine controls and multi-machine
          systems. Since 1998, he has managed the Multi-machine Multi-converter Systems
          project of GdR-ME2MS, a national research program of the French CNRS.

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