FIVE PHASE INDUCTION MOTOR
GUDLAVALLERU ENGINEERING COLLEGE
B.NEELA KUMAR
V.VEDAVYAS
R.No: 12485A0213
R.No: 11481A02B1
Email: neelakumar213@gmail.com
Email: electricalelegnat@gmail.com
Ph.No : 9640630111
Ph.No : 8008287664
ABSTRACT
This paper introduces two kinds of control
schemes:
Vector control and direct torque control
(DTC). These control schemes can be
extensively applied to the operation of a
five-phase induction motor using a fully
digital implementation. Vector control of the
five-phase induction motor not only
achieves high drive performance, but also
generates the desired nearly rectangular
current waveforms and flux profile in the
air-gap resulting in an improvement in air
gap flux density and an increase of 10% in
output torque. The DTC method has
additional advantages when applied to
multiphase, in this case a five-phase,
induction motor. The five-phase inverter
provides 32 space voltage vectors in
comparison to 8 space voltage vectors
provided by the three-phase inverter.
Therefore, a more elaborate flux and torque
control algorithm for the five-phase
induction motor can be employed. Direct
torque control of the five-phase induction
motor reduces the amplitude of the ripples
of both the stator flux and the torque,
resulting in a more precise flux and torque
control. A 32-b floating-point TMS320C32
Digital Signal Processor (DSP) enables
these two sophisticated control techniques to
be conveniently implemented with high
control precision. Experimental results show
that an ideal control capability is obtained
for both control methods when applied to
the five-phase induction motor and further
validates theoretical analysis.
INTRODUCTION
Vector control and direct torque control
(DTC) are two popular control techniques
widely applied in motor drive applications.
By directly controlling the flux and the
torque, both techniques yield fast dynamic
response and high performance. In this
paper, a corresponding vector control
Method of the five-phase induction motor is
developed based on the reference frame. The
basic underlying principle here is to
decouple the five stator phase currents into
the flux components, and the torque
components, and then to provide
independent control of both flux and torque.
The objective with vector control of the
five-phase induction motor is to generate the
fundamental
current
waveform
and
associated third harmonic of this
fundamental and appropriately to combine
these waveforms, thereby inducing the
desired nearly rectangular flux in the airgap. As a result, an improvement in the
power density and output torque of the fivephase induction motors can be achieved.
Direct torque control of the five-phase
induction motor is also introduced in this
paper. Through the optimal selection of the
space voltage vectors during each sampling
period, direct torque control provides an
effective and direct control of the stator flux
and the torque, an alternative to employing
current control, a more conventional
technique. In the case of the five phase
induction motor, direct torque control has
unique advantages. Direct torque control of
the five-phase induction motor has 32 space
voltage vectors with varying magnitudes
when employing closed loop operation.
Compared with eight space voltage vectors
associated with conventional three-phase
induction motor drives. The increased
number of space voltage vectors provides
direct torque control, when operating in
closed loop, of the five-phase induction
motor, greater flexibility in selecting the
inverter switching states and thereby
accomplishes a more precise control of the
stator flux and torque. From a maintenance
and reliability perspective, the benefit
achieved with additional space voltage
vectors is that the zero sequence vectors
need not be chosen. The implication of this
is that zero sequence mode vectors have
been shown to cause bearing currents which
result in pitting and fluting of the motor
bearing, thereby reducing the life of the
motor. In order to implement these two
sophisticated control methods, a 32-b
floating-point TMS320C32 DSP is adopted
as the central processor. Operating from a 50
MHz clock speed, a performance of 25
MIPS and a peak floating-point performance
of 50 MFLOPS allows vector control and
direct torque control of the five-phase
induction motor with higher processing
speed and precision. Experimental results
show that ideal control performance is
achieved in both control methods for the
five-phase induction motor, both of which
validate theoretical predictions and analysis.
VECTOR CONTROL OF FIVEPHASE INDUCTION MOTOR
In this paper, a five-phase induction motor
with a full pitch concentrated winding is
used. Instead of the traditional sinusoidal
winding distribution, the winding structure
of the five phase induction motor is
designed with a rectangular distribution to
better accommodate the quasi-rectangular
input currents provided by the five-phase, In
order to simplify the vector control method
of the five phase induction motor, a
combined fundamental current waveform
with the third harmonic of the fundamental
current waveform, which nearly replicates a
rectangular waveform, is considered as the
input current of the five-phase induction
motor instead of the required rectangular
currents. In conjunction with the designed
five-phase induction motor geometry, this
current profile induces the nearly
rectangular flux linkage in the air-gap and
thus results in higher power density and
more torque output. The principle goal of
vector control of the five-phase induction
motor is to decouple the stator currents into
the flux components, and the torque
components, and then to perform
independent control on the fluxes and the
torques in a manner analogous to separately
excited DC motor drives. vector control of
the five-phase induction motor enables the
fundamental flux and the torque and the
third harmonic flux and the torque to be
decoupled
respectively,
achieving
independent control of the fluxes and the
torques of the five-phase induction motor.
The overall system includes two closedloops, an inner current loop and an outer
speed loop. Whenever a reference speed is
given, the system automatically compares it
with the actual speed. According to the
motor equation of motion, the speed error
directly indicates the torque profile.
Therefore, the output of the speed PI
regulator is considered as the torque
reference value. Correspondingly, the torque
component of the stator current can be
obtained.
FIG: Vector control of a five-phase
induction motor.
DIRECT TORQUE CONTROL OF
A FIVE-PHASE INDUCTION
MOTOR
Direct torque control (DTC) of induction
motors is also a powerful control method for
use with motor drives. In principle, the DTC
method is based on instantaneous space
voltage vector theory. Through the optimal
selection of space voltage vectors during
each sampling period, direct torque control
provides the effective and direct control of
the stator flux and torque instead of current
control, a more conventional technique.
Thus, the DTC strategy is dependent upon
the motor-inverter system, the number of
space voltage vectors and the switching
frequency all of which directly influence the
performance of the DTC system. In
comparison with three-phase induction
motor drives, the five-phase motor drives
are supplied with a five-phase voltage
source inverter (VSI). In this case, there are
two zero voltage states associated with
either all of the five upper switches “on” or
all of five bottom switches “on”.
Additionally, there are thirty nonzero
switching modes. The total number of the
five-phase inverter switching combinations
is (2^5=32) and thus there are 32
corresponding space voltage vectors. In
particular, the 32 space voltage vectors are
composed of three sets of vectors having
different amplitudes and divides the
witching plane into ten sectors
FIG: Direct torque control of the five-phase
induction motor.
EXPERIMENTAL SETUP AND
HARDWARE STRUCTURES
OF THE CONTROL SYSTEM
FIG: Space voltage vectors of a five-phase
inverter-driven system.
Based on the proposed vector control and
DTC schemes, a fully digital control system
has been implemented. The five phase
current regulated inverter, on the right side
of the five phase motor, is a natural
extension of the standard three-phase
inverter. The insulated gate bipolar
transistors (IGBTs) are used as switching
devices of the inverter. The switching
frequency used in the experiment is 10 kHz.
The controller indicated at the bottom uses a
TMS320C32 DSP to provide vector control,
DTC and to drive the five-phase inverter to
generate the desired rectangular currents and
flux. In this experiment, four channels of
analog-to-digital converter (ADC) are used
for sampling four phase stator currents
through four Hall Effect current sensors of
model number HNC-050P. The speed pulse
signal generated by a Dynapar H25 speed
encoder inputs to the TMS320C32 DSP via
one digital input port. After executing the
five-phase induction motor control methods,
five channels of digital to analog converter
(DAC) output the desired current control
signals to produce the five channels
containing the PWM pulses and are then
sent to the SKHI22 IGBT drive circuits.
Furthermore, the gating signals are
generated to control the five-phase inverter
and motor. The DSP-based control system
of the five-phase induction motor consists of
three interconnected modules: the C32 DSP
board, 16I/O8 DSPLINK interface and Pulse
Width Modulated (PWM) output circuits.
TMS320C32 DSP is used as the central
processor of the control system and
implements the corresponding control
algorithms—vector control and DTC. DC
link voltage, the stator currents and the
speed are sampled and transmitted to the
DSP through the 16I/O8 DSPLINK
Interface board. Based on this information,
the control system generates the required
five-phase PWM gating signals to drive the
five-phase
induction
motor.
The
TMS320C32 DSP used is a 50 MHz, 32-bit
floating-point processor with two on-chip 32
bit timers, an enhanced external memory
interface, a two-channel DMA controller
and a serial port. This arrangement offers a
versatile and powerful development tool for
motor drives.
FIG: Experimental setup of the five-phase
induction motor drive.
FIG: Overall hardware architecture of the
control system.
Below FIG is the functional block diagram
of the PWM output circuit. This generates
ten channel PWM signals by comparing the
outputs of the current PI regulators with a
triangular carrier waveform. These signals
are then sent to the IGBT drive circuits
(SKHI22) to form the five-phase inverter
gating signals, which directly drive the fivephase induction motor. SKHI22 assures a
dead time of 2 s between the gate signals of
the upper and the lower devices as a means
to protect IGBTs in each leg from voltage
shoot through. Fault protection circuits
perform real-time monitoring of the dc link
over-voltage (OV), the stator over-voltage,
the stator low-voltage (LV) and the stator
over-currents (OI), as well as overheating
(OH) of the stator windings, so that the
PWM outputs can be blocked immediately
upon the occurrence of one or more of these
faults.
FIG: Block diagram of PWM output circuit.
CONCLUSIONS
Vector control of the five-phase induction
motor drive with the combined fundamental
and third harmonic current not only achieves
high transient and steady state performance,
but also provides the desired nearly
rectangular current and flux waveforms.
This in turn results in improvement of the
flux density and about a 10% increase of
output torque by injecting the third harmonic
of current.
Direct torque control is a very practical
control method to be applied to the fivephase induction motor. 32 space voltage
vectors result in a significant reduction of
the torque and the stator current ripples and
implement a more accurate control of the
flux and the torque.
REFERENCES
1. Huangsheng Xu, Member, IEEE,
Hamid A. Toliyat, Senior Member,
IEEE, and Lynn J. Petersen,
Member, IEEEB. K. Bose, “High
performance control and estimation
in AC drives,” in Proc. 23rd Int.
Conf. Ind. lectron. Contr. Instrum.,
vol. 2, 1997, pp. 377–385.
2. I. Takahashi and Y. Ohmori, “Highperformance direct torque control of
an induction motor,” IEEE Trans
Ind. Applicat., vol. 25, pp. 257–264,
Mar./Apr. 1989.
3. P. Vas, Sensorless Vector Control
and Direct Torque Control. New
York: Oxford University Press,
1998.