Download sensorless drive for high-speed brushless dc motor

SENSORLESS DRIVE FOR HIGH-SPEED BRUSHLESS DC MOTOR
BASED ON THE VIRTUAL NEUTRAL VOLTAGE
ABSTRACT:
The brushless dc (BLDC) motor can be driven by either pulse-width modulation
(PWM) or pulse-amplitude modulation (PAM) techniques. Unfortunately, neither
of them can be the most suitable method for the high-speed BLDC motor in the
wide speed range, so a hybrid drive method combining PWM and PAMis first
introduced. Then, this paper proposes a new sensor less control method based on
the virtual neutral voltage for high-speed BLDCmotor to suit for this hybrid drive
method. In order to obtain the commutation signals from this seriously unclear
voltage signal due to the commutation notches and electromagnetic interference, a
low-pass filter with super low cutoff frequency is employed at the price of a large
phase delay. Meanwhile, a novel sensor less control method based on the transition
between “90–α” and “150–α” is introduced to handle the severe phase delay. At
last, the feasibility and effectiveness of the proposed drive method and the sensor
less control method are verified by several experiment results.
INTRODUCTION:
In recent years, high-speed brushless dc (BLDC) motor, which due to its high
efficiency, compactness, low cost, and maintenance compared with a brush dc
motor, is receiving more and more interest in industrial automation, especially on
blowers and compressors.
Since the rotation speed of a high-speed motor can reach up to tens of thousands
revolutions per minute(r/min) due to the development of bearing technology, a
proper drive method to ensure low loss and high efficiency in a wide speed range
becomes a critical issue.
Meanwhile, it is well known that the BLDC motor requires six discrete rotor
positions for the inverter operation. These are typically generated by Hall sensors
mounted on a motor. However, it is a well-known fact that these sensors increase
the cost of the motor and need special mechanical arrangements to be mounted.
To break through the aforementioned restriction, many position sensorless methods
have been considered as potential solutions, thus prompting the sensorless
operation of the BLDC motor to be a hot issue in recent years.
Therefore, to cope with these two issues effectively will promote the development
of the high-speed BLDC motor
EXISTING SYSTEM:
Generally, the BLDC motor can be driven by either pulse-width modulation
(PWM) or pulse-amplitude modulation (PAM) techniques. It is well known that
the inverter, which applied to most of the BLDC motor drive systems, is controlled
by the PWM scheme for varying the voltage. When the PWM control is valid, the
dc-link voltage is fixed, and the duty of the inverter is controlled by the speed and
load conditions.
Also, it is popular in the low-speed BLDC motor control. Unfortunately, for a high
speed BLDC motor, the high-frequency and large-range current ripple will
inevitably increase the copper and rotor iron losses. The PAM scheme is another
popular control mode for the BLDC motor, especially at high speed.
For PAM control, 120-degree commutation control, i.e., the so called six-step
mode is generally used with lower switching frequency than the PWM control.
Meanwhile, the dc-link voltage can be adjusted according to the error between the
speed and its reference. Moreover, the conclusion that the PAM control for the
BLDC motor can provide lower harmonic content and higher efficiency than the
PWM control shows the superiority of PAM control at high speed
PROPOSED SYSTEM:
Generally, the BLDC motor can be driven by either pulse-width modulation
(PWM) or pulse-amplitude modulation (PAM) techniques. It is well known that
the inverter, which applied to most of the BLDC motor drive systems, is controlled
by the PWM scheme for varying the voltage. When the PWM control is valid, the
dc-link voltage is fixed, and the duty of the inverter is controlled by the speed and
load conditions. Also, it is popular in the low-speed BLDC motor control.
Unfortunately, for a high speed BLDC motor, the high-frequency and large-range
current ripple will inevitably increase the copper and rotor iron losses. The PAM
scheme is another popular control mode for the BLDC motor, especially at high
speed. For PAM control, 120-degree commutation control, i.e., the so called sixstep mode is generally used with lower switching frequency than the PWM control.
Meanwhile, the dc-link voltage can be adjusted according to the error between the
speed and its reference. Moreover, the conclusion that the PAM control for the
BLDC motor can provide lower harmonic content and higher efficiency than the
PWM control shows the superiority of PAM control at high speed
ADVANTAGES:
Simplicity of implementation, robust to electronic noise, and eliminating the need
for the motor neutral wire
BLOCK DIAGRAM:
TOOLS AND SOFTWARE USED:
MPLAB – microcontroller programming.
ORCAD – circuit layout.
MATLAB/Simulink – Simulation
APPLICATIONS:
Motor drives