Download thus, online fault diagnosis of the power inverter is

ONLINE INVERTER FAULT DIAGNOSIS OF BUCK-CONVERTER
BLDC MOTOR COMBINATIONS
ABSTRACT:
Brushless dc (BLDC) motors are commonly used in space application for its
simplicity and high reliability. The fault tolerant control (FTC) of the motor is
important for its continuous operating capacity even under the faulty situation. The
fault diagnosis should be achieved in advance in order to implement the FTC
strategy. This paper proposes an online model-based inverter fault diagnosis
method for three-phase full bridge inverter with buck dc–dc converter based on the
high-speed BLDC motor with low inductance and no ideal back electromotive
force in a magnetically suspended control moment gyro. The method can detect
and identify both open-circuit and short-circuit damages of single switch in buck
converter or three-phase full bridge. Also, protective measures are proposed to
isolate the fault and avoid the secondary fault. Both simulation and experimental
results are taken out to prove the validity and effectiveness of the proposed fault
diagnosis method.
INTRODUCTION:
Magnetically suspended control moment gyro (MSCMG) is considered to be the
key actuators for the attitude control of space stations, satellites, etc. It has the
character of high precision, large moment, and long life owing to the zero friction
and enhanced damping of high-speed rotor. Since the operational environment in
vacuum is harsh, high reliability and long-life operating ability are required.
Normally, the high-speed motor in MSCMG is operating at a constant high speed
to supply angular momentum for the high-speed rotor system. The reliability of the
motor drives is one of the most important factors to guarantee the safe, continuous,
and high performance operation under even some accidents or faults.
The research mentioned that about 38% of the motor failures are found in the
power inverter and most of faults are occurred to the power switches. Generally, a
fault-tolerant control (FTC) system is composed of fault detection, identification,
and remedial actions.
The fault detection and identification considered as fault diagnosis which is the
basic and important part in FTC system can detect the fault and determine the fault
type and location.
thus, online fault diagnosis of the power inverter is important for MSCMG to
ensure the continuous operating ability even in the faulty state
EXISTING SYSTEM:
The switching devices have been replaced by an ideally switched voltage source.
This is indicated by the multiplication of Ue with the switching variable u ∈ {0, 1}.
An additional resistance RL has been added to the model in order to take into
account the ohmic resistance of the coil windings. The motor has been modeled by
an inductance LM with ohmic resistance RM and electromagnetic voltage source
ωKE
PROPOSED SYSTEM:
This paper proposes a model-based and low-cost switch fault diagnosis method for
motor inverter composed of a buck converter and a three-phase full bridge. Based
on the analysis of the faulty operating state in closed-loop control system, the
residual signals of the voltage observers and the measurements are extracted to
diagnose the inverter fault. The effect of nonideal back electromotive force (EMF)
caused by practical reasons in production on the estimated voltage is taken into
account in the proposed voltage observer. The method can detect and identify both
open-circuit and short circuit faults fast and exactly with reduced hardware. The
faults in buck converter and three-phase full bridge can be distinguished in real
time. Meanwhile, protection measures are carried out to prevent the system from
secondary fault.
BLOCK DIAGRAM:
TOOLS AND SOFTWARE USED:
MPLAB – microcontroller programming.
ORCAD – circuit layout.
MATLAB/Simulink – Simulation
APPLICATIONS:
BLDC drives