This paperproposes thehighfrequency (hf) voltage injection technique toDTC drives withtheobjective ofextending theirperformance tothelowandzerospeedregion. The simplicity oftheoriginal DTC algorithm isnotcompromised. The hfcarrier isintroduced by thedirect modification ofthe fundamental voltage vectors. Theposition signal isthenobtained fromthedirect demodulation oftheresulting hfcurrents. Both simulation andexperimental results areshown. I. INTRODUCTION ThePermanent MagnetSynchronous Motor(PMSM)is increasingly playing animportant roleinelectric propulsion systemsdue to itsmany advantages overcompeting technologies. ThePMSM offers ahigher efficiency, higher powerdensity andbetter dynamic performance. Foraccurate control ofthePMSM,rotor position information isrequired. Anencoder mounted ontheshaft ofthemachine canprovide this information butitalsoincreases system cost, volumeand weight. Furthermore, theoverall reliability ofthedrive is reduced, especially inharsh conditions. Extensive research has beendirected towards sensorless control ofPMSM andseveral approaches arereported intheliterature. Sensorless controlschemesbasedon conventional fundamental-frequency modelsor observer-based methods fulfill thedemandinthehigher speed rangebuthavebeen showntogivepoorandasymptotically failing performance as zerospeedisapproached. Thisoccurs duetothelossof information astheinduced backemfbecomesverysmall. Moreover, suchmethodsarestrongly dependent on the machine parameters, whichcanvaryduring operation. The desirability tooperate continuously atloworzerospeed has ledtoanother sensorless approach wherethesaliency ofthe machine istracked through someformofsignal injection to obtain fluxorposition information. Saliencies arenot restricted toaspecific machine type.Theyarewellknownin Synchronous Reluctance machines(1) (2)and buried permanent magnet machines (3)(4)(5), butthey also exist, even though muchsmaller, ininduction machines, andsurface mounted PMSM. Successful position andspeed control atlow andzerospeed region hasbeenreported intheliterature even forlowsaliency machines using highfrequency (hf) carrier injection anddiscrete voltage vector injection techniques. The approaches, however, seemtobelimited tovector controlled drives. Direct TorqueControl (DTC)hasemerged overthelast decade andhasbeenshowntobeaworthy alternative tothe well-known VectorControl. Theclassical DTC alsolends itself easily tosensorless control through thefluxmodel estimator butitsuffers thesamelackofperformance asforthe vector sensorless drives atlowandzerospeed.Thispaper addresses thisbyextending thehfinjection techniques toa PMSM DTCdrive toobtain DTCperformance eveninthelow andzerospeedregion. Thepaperstarts bygiving abrief reviewoftherotating hfinjection asapplied forvector controlled drives andthenshowsitsimplementation inaDTC drive.Theobjective istoextend thespeedrangewithout compromising thesimplicity oftheDTC. Simulation results areshownfora sensorless PMSM DTC drive.Initial experimental results fortheproposed approach arealso shown.