DIRECT TORQUE CONTROL OF PERMANENT MAGNET SYNCHRONOUS MOTORS WITH NON-SINUSOIDAL BACK-EMF A Dissertation by SALIH

Direct Torque Control of Permanent Magnet Synchronous Motors With Non-Sinusoidal Back-EMF. (May 2008) Salih Baris Ozturk, B.S., Istanbul Technical University, Istanbul, Turkey; M.S., Texas A&M University, College Station Chair of Advisory Committee: Dr. Hamid A. Toliyat This work presents the direct torque control (DTC) techniques, implemented in fourand six-switch inverter, for brushless dc (BLDC) motors with non-sinusoidal backEMF using two and three-phase conduction modes. First of all, the classical direct torque control of permanent magnet synchronous motor (PMSM) with sinusoidal back-EMF is discussed in detail. Secondly, the proposed two-phase conduction mode for DTC of BLDC motors is introduced in the constant torque region. In this control scheme, only two phases conduct at any instant of time using a six-switch inverter. By properly selecting the inverter voltage space vectors of the two-phase conduction mode from a simple look-up table the desired quasi-square wave current is obtained. Therefore, it is possible to achieve DTC of a BLDC motor drive with faster torque response while the stator flux linkage amplitude is deliberately kept almost constant by ignoring the flux control in the constant torque region. Third, the avarege current controlled boost power factor correction (PFC) method is applied to the previously discussed proposed DTC of BLDC motor drive in the constant torque region. The test results verify that the proposed PFC for DTC of BLDC