Extension of the DTC concept

A novel direct torque fuzzy control of SVM-inverter-fed induction motor drive

“…Application of this scheme results in very fast and robust bang-bang control, with large torque, flux, and current ripple, and variable switching frequency. Many solutions were proposed to improve performances [3][4][5][6].…”

“…Namely is multi level inverter [5] and the second is space vector modulation (SVM) [6]. In the first method, the cost and the complexity will be increased, in the second method, the torque ripple and flux ripple can be reduced, however the switch frequency still changes.…”

Dynamic reconfiguration of direct torque and stator flux control by means of sliding mode theory

“…directly derived from (15) anld (16) Six of them are positioned on the ends of an asymmetric star in dhe plane (S,, , ST ). The star rotates at the speed of stator flux vector, fonning anl ellipsis.…”

“…In other words, the components V,', and V,', of the complete voltage vector depend on the direction of S,,, and ST, variations. This complete voltage vector can be generated either by a direct control of the VSI that is based on ail instantaneous model of the process or by anl indirect control that is based on an average model of the process (during a switching period).Direct Control of the voltage Source inverterGlobal switching function loci By substituting(16) in(15), the global switching function time-derivative, S, can then be written according to the difference between the available voltage vector (one of the eight voltage vectors which can be generated by the VSI) and the equivalent voltage vector, V__ which depends on the operating point: Loci of S wJhen the st<ator flux vector is located in the middle of (b) second-sector, (c) third-sector, (d) fith-sector, (e) sixth-sector, and (a) division ofthe angle 00, in six sectors in the plan(-a, for 1T= Te _case of a direct control of the VSI, the global switching function. S, has seven possible derivatives.…”

“…Solving(15) for V: yields the equivalent voltage vector V' e R,i d 'pk Ld [+L,5R, T+~' In this equation, the state variables are expressed in a reference frame rotating at the speed of stator flux vector.…”