Pulse-width modulation inverters have widely been used in
motor drives. However, these inverters produce voltage distortion
due to nonlinear characteristics of switching devices
such as turn-on/turn-off times, voltage drops on switches
and diodes. A further important nonlinearity is caused by
necessary dead-time introduced to avoid the so-called shootthrough
of the dc link. In fact, to guarantee that both
switches never conduct simultaneously, a small time delay is
applied to the gate signal of the turning on device. This
small time interval, in order of μs, introduces magnitude and
phase errors in the output voltage. The voltage distortion
increases with switching frequency, introducing harmonic
components that may cause instabilities and additional
losses in the machine being driven. Relative voltage
deviation effect is more significant for low modulation
indexes [1]-[5].
The dead-time problem has already been investigated by
the industry [2], [3] and various solutions have been proposed.
In most cases the compensation techniques are based
on an average value theory, the lost volt-seconds are averaged
over an entire switching period and added to the commanded
value. A pulse-based compensation method has
been proposed in [2], where the compensation is realized for
each pulse. The compensation voltages in [3] are calculated
by using dead-time, switching period, current command and
dc-link voltage. Regardless of the method used, all deadtime
compensation techniques are based on polarity of the
current in the switching leg. This is especially true around
the zero crossing where an accurate measurement is needed
to correctly compensate for the dead-time. In [4] an online
dead-time compensation technique is presented, acquiring
the additional computation burden to determine the phase
angle of currents.
The area of multiphase variable-speed motor drives, in
general, and multiphase induction motor drives, in particular,
has experienced a substantial growth since the beginning
of this century. Detailed overview of the current state-of-theart
in this area is given by [6]. The inverter dead-time effect
on the steady-state and dynamic performances of a multiphase
induction machine with current control is analyzed in
[7]. The paper suggests a modified current control scheme
that is able to compensate inverter dead-time and provides
sinusoidal currents. Although in this case it is possible to
have perfect compensation of dead-times, the problem remains
for the drives that are based on machine flux estimation,
since dead-time introduces errors if input dc voltage
and switch patterns are used for calculations instead of actual
ac output voltages. Analysis and compensation method
for a five-leg inverter driving two three-phase ac motors independently
has been done in [8]. Practically, this analysis
can be simplified as for three-phase inverters, since the motors
are independent. An analysis of the effect of dead-time
introduced for multi-phase inverters is given by [9], first for
the case of three-phase, then with a general extension to n
phases, with specific numerical verifications on five- and
seven-phase inverters. An overview on dead-time analysis
on multi-phase inverters is given as well in [10], where is
the dead-time effect on load voltage also represented in
terms of multiple space vectors, and analysis of harmonics
content for each α-β plane is given.
2nd IEEE ENERGYCON Conference & Exhibition, 2012 / Advances in Energy Conversion Symp
978-1-
Pulse-width modulation inverters have widely been used in
motor drives. However, these inverters produce voltage distortion
due to nonlinear characteristics of switching devices
such as turn-on/turn-off times, voltage drops on switches
and diodes. A further important nonlinearity is caused by
necessary dead-time introduced to avoid the so-called shootthrough
of the dc link. In fact, to guarantee that both
switches never conduct simultaneously, a small time delay is
applied to the gate signal of the turning on device. This
small time interval, in order of μs, introduces magnitude and
phase errors in the output voltage. The voltage distortion
increases with switching frequency, introducing harmonic
components that may cause instabilities and additional
losses in the machine being driven. Relative voltage
deviation effect is more significant for low modulation
indexes [1]-[5].
The dead-time problem has already been investigated by
the industry [2], [3] and various solutions have been proposed.
In most cases the compensation techniques are based
on an average value theory, the lost volt-seconds are averaged
over an entire switching period and added to the commanded
value. A pulse-based compensation method has
been proposed in [2], where the compensation is realized for
each pulse. The compensation voltages in [3] are calculated
by using dead-time, switching period, current command and
dc-link voltage. Regardless of the method used, all deadtime
compensation techniques are based on polarity of the
current in the switching leg. This is especially true around
the zero crossing where an accurate measurement is needed
to correctly compensate for the dead-time. In [4] an online
dead-time compensation technique is presented, acquiring
the additional computation burden to determine the phase
angle of currents.
The area of multiphase variable-speed motor drives, in
general, and multiphase induction motor drives, in particular,
has experienced a substantial growth since the beginning
of this century. Detailed overview of the current state-of-theart
in this area is given by [6]. The inverter dead-time effect
on the steady-state and dynamic performances of a multiphase
induction machine with current control is analyzed in
[7]. The paper suggests a modified current control scheme
that is able to compensate inverter dead-time and provides
sinusoidal currents. Although in this case it is possible to
have perfect compensation of dead-times, the problem remains
for the drives that are based on machine flux estimation,
since dead-time introduces errors if input dc voltage
and switch patterns are used for calculations instead of actual
ac output voltages. Analysis and compensation method
for a five-leg inverter driving two three-phase ac motors independently
has been done in [8]. Practically, this analysis
can be simplified as for three-phase inverters, since the motors
are independent. An analysis of the effect of dead-time
introduced for multi-phase inverters is given by [9], first for
the case of three-phase, then with a general extension to n
phases, with specific numerical verifications on five- and
seven-phase inverters. An overview on dead-time analysis
on multi-phase inverters is given as well in [10], where is
the dead-time effect on load voltage also represented in
terms of multiple space vectors, and analysis of harmonics
content for each α-β plane is given.
2nd IEEE ENERGYCON Conference & Exhibition, 2012 / Advances in Energy Conversion Symp
978-1-
การแปล กรุณารอสักครู่..
![](//thimg.ilovetranslation.com/pic/loading_3.gif?v=b9814dd30c1d7c59_8619)