The direct torque contr ol theor y has achieved g reat success in the control of induction
motor s. How ever, in the DT C dr ive system of Permanent Mag net Synchronous M achine ( PMSM )
pr oposed a few years ago, ther e are many basic theoretical problems that must be clarified. This paper
describes an investigatio n about the effect of the zer o voltage space v ector s in the DTC sy stem of
PMSM and points out that if using t he zero voltage space vectors rat ionally , not only can the DTC
sy stem be driven successfully but also the tor que r ipple is reduced and the perfo rmance of the sy stem
is impr oved. This paper also st udies the senso rless technique in the DT C system of PMSM and configures
the DTC system o f PMSM w ith sensor less technique including zero voltage space v ecto rs. Numer
ical simulations and ex per iment al tests have pr oved the theo ry corr ect . In the conditio n of sensorless,
the DTC sy stem of PMSM is wide-rang ely speed adjusting, and the ratio o f speed adjustment is
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