DIRECT TORQUE CONTROL OF BLDC USING THREE
PHASE CONDUCTION MODE
Direct torque control (DTC) was proposed for the first
time by Takahashi and Noguchi in 1986 [8] and Depenbrock
in 1988 [9] for induction motors. Recently, many researches
worked on DTC of BLDC motor for specific applications
which needs precise torque control. Various methods of
implementing DTC of BLDC have been reported [10-15].
DTC technique of BLDC has been applied to drive train of
hybrid electric vehicle [15]. Overall block diagram of DTC
of BLDC motor is shown in Fig. 2.
Torque error, stator flux error and stator flux angle are
regularly used to select proper voltage space vector for
switching in DTC technique. In this paper flux linkage error
is eliminated Because of variations of stator flux magnitude
regarding changes in resistance, current and voltage and
specifically sharp dips at every commutation [10]. BLDC
operates in both constant torque region and constant power
region. Back-EMF of motor is below DC voltage source of
inverter in constant torque region (below base speed) and is
increased more than DC voltage value above nominal speed.
Therefore stator inductance avoids abrupt increase of phase
current and deteriorates output torque of motor. Therefore in
this paper operation of