Implementation of Sensorless Vector Control for Super-High-Speed PMSM of Turbo-Compressor Bon-Ho Bae,Member,IEEE,Seung-Ki Sul,Fellow,IEEE,Jeong-Hyeck Kwon,Member,IEEE,and Ji-Seob Byeon
Abstract—This paper describes the implementation of two
vector control schemes for a variable-speed131-kW perma-
nent-magnet synchronous motor drive in super-high-speed
applications.The vector control with a synchronous reference
frame current regulator was implemented with challenging
requirements such as an extremely low stator inductance(28
Fig.3.Power circuit diagram of the proposed super-high-speed PMSM drive.
and the operation of the current regulator was tested up to
an excitation frequency of1200Hz.In addition,the vector
control schemes with and without the discrete Hall sensors are
proposed.In the case of a vector control with three discrete
Hall sensors,the discrete Hall sensors provide rough position
information with a resolution of
s.Because
the general-purpose microprocessors cannot meet the required
calculation time,the TMS320VC33-150digital-signal-pro-
cessor(DSP)-based digital controller was developed for the
implementation.The experimental data showed that it takes
less than20
BAE et al.:SENSORLESS VECTOR CONTROL FOR SUPER-HIGH-SPEED PMSM OF TURBO-CO
MPRESSOR813
Fig.4.Block diagram of the synchronous reference frame current regulator with the inductor.usb暖手
鼠标垫 (a)(b)(c)
Fig.5.Current waveform of synchronous reference frame current regulator with an inductor load.(a)Current waveforms with excitation frequency of20Hz.
(b)Current waveforms with excitation frequency of1200Hz.(c)Current waveforms with excitation frequency of1200Hz.(Magnitude of current reference is changed from350to200A
s,which is relatively large consid-
ering the short PWM update period,33.33
814IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS,VOL.39,NO.3,MAY/JUNE2003 Fig.5shows the experimental results with the proposed cur-
rent regulator.A three-phase air-core reactor is used for the test,
and the inductance is set to the same value of the stator induc-
tance of the PMSM,28
,-phase
current measured by the current probe set(Tektronix CT-4,
A6302and AM503),.The traces shown in Fig.5(a)
present the experimental results using an excitation frequency
of20Hz.From the results shown in Fig.5(a),it can be seen
that the performance of the current regulator was degraded at
the zero crossings of the phase currents because of the effect
of the dead time and the zero-current clamping even after
careful compensation[7],[8],[10].The traces in Fig.5(b)
show the experimental results with an excitation frequency of
1200Hz.Because the dead-time effect and the zero-current
clamping effect are reduced at high frequency,the currents are
well controlled sinusoidally without degradation.However,the
measured currents in Fig.5(a)and(b)show large ripples
due to the very small load inductance.The delay in the sampled
current
to200A.
The bottom trace in Fig.5(c)shows the magnitude of the
current vector,
,
砭石
能量房
谢宇风
30
from the input of the latest
angle pulse to the sampling point was measured by the pro-
grammable logic device.The speed of the motor,
BAE et al.:SENSORLESS VECTOR CONTROL FOR SUPER-HIGH-SPEED PMSM OF TURBO-COMPRESSOR
815
Fig.9.Block diagram of sensorless vector control scheme without position sensor.
Based on the assumption that the rotor speed does not change between the pulses,the rotor angle at the sampling
point s at the
normal speed and the speed does not change rapidly,reasonably accurate speed information can be calculated by the algorithm.The test results with the proposed vector control scheme using the angle information of the Hall-effect sensors are shown in Fig.7.For the experiment,three discrete Hall-effect sensors with a sensing magnet were installed in the PMSM and a special digital logic circuit was implemented to measure
the
angle
of Fig.8using the programmable logic device.
From top to bottom,the traces show
the
-axis current ,the motor phase
current
-axis current are shown.
For the test,the extrapolation of the rotor angle has not been carried out at low speed,where the speed information is not reliable.Therefore,the discontinuous angle information deteriorated the performance of the current regulator.Fig.7(b)shows the acceleration from 17000to 20000r/min.Because precise angle information is available using the extrapolation,the vector control scheme provides the effective current and speed regulation.
Compared to the conventional position sensors,the discrete Hall sensors were much more reliable in a super-high-speed op-eration.However,the installation of the Hall sensors and the sensing magnet limits the mechanical design,and the sensorless control is a better solution for super-high-speed applications.In the case of the turbo-compressor application,the installation of a sensing magnet even causes difficulties in the aerodynamic design.
V .S ENSORLESS V ECTOR C ONTROL S CHEME W ITHOUT
ANY P OSITION S ENSOR Fig.9shows a block diagram of the sensorless vector control scheme without the position sensor.In the diagram,the feedfor-ward
terms
is the error between the real rotor
-axis voltage
error,which has to be compensated for by
the
is small,
the output voltage of
the
(11)
In the proposed estimator in Fig.9,the error signal of (11)is processed by the PI compensator to derive the rotor speed and the rotor angle is calculated by integrating the estimated speed.In the conventional method [3],a differentiation process
816IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS,VOL.39,NO.3,MAY/JUNE2003
Fig.10.Frequency pattern for constant current control with pre-patterned
frequency.
is used to calculate the speed but this makes the system vul-
nerable to measurement noise.The experimental study reveals
that the proposed estimator provides a very accurate and robust
speed information for the application.However,at the zero and
low speed,the back-EMF voltage is not high enough for the
proposed vector control.Hence,for the initial alignment and
starting from zero speed,the current was controlled with a con-
stant magnitude using a pre-patterned angular frequency.In ad-
dition,the angle for the synchronous reference frame was calcu-
lated by integrating the frequency.Fig.10shows the frequency
一个度导航pattern for the initial alignment and starting.As shown in step I
of Fig.10,the initial value of the frequency pattern is set to a
small but constant speed for the initial rotor alignment.
After the alignment,according to the speed pattern in step II,the
motor is accelerated up to the threshold speed.Over the
threshold speed,the motor is then controlled by the proposed
sensorless control and the speed is estimated by the proposed
estimator shown in Fig.9.
VI.E XPERIMENTAL R ESULTS W ITH S ENSORLESS C ONTROL
The experimental results with the proposed sensorless con-
trol are shown in Figs.11–14.Fig.11shows the starting char-
acteristics from zero speed to20000r/min.The PMSM was
accelerated by the rotating current vector with the precalcu-
lated frequency pattern shown in Fig.10.In order to align the
rotor,the current vector was rotated with the starting frequency
-axis current tracks the command with a small
ripple current,which is caused by the dead time and zero-current
clamping effects.Because the current control bandwidth was set
low for the sensorless algorithm,the actual current tracks the
command with a delay.The bottom trace shows the measured
phase current,,which was measured by a current probe
set(Tektronix AP504CX and AM503B).Due to the extremely
small stator inductance,the fundamental current was accompa-
nied by a significant ripple current,which was caused by the
15-kHz PWM switching.Fig.13(b)shows the magnified wave-
forms of the last two periods in Fig.13(a).The traces show that
the phase current is controlled sinusoidally by the precise sam-
pling of the fluctuating current.
In Fig.13,the measured phase current shows a rela-
tively large current ripple,which can increase the temperature
of the rotor.Because a high temperature can degrade the
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