부산대학교 도서관

Modern hybrid or electrical vehicles require the motor drives with high power density, high efficiency, efficient regenerative braking, wide speed range and high controllability. The electric motor provides greater efficiency by replacing the starter and alternator with a single device which assists the powertrain. Mild hybrids do not require the same level of battery power and do not achieve the same levels of fuel economy improvement as compared to full hybrid models. Compared to a full hybrid vehicle, however, mild hybrids may provide some of the benefits of the application of hybrid technologies, with less of the cost–weight penalty that is incurred by installing a full hybrid series-parallel drivetrain. Fuel savings would generally be lower than expected with use of a full hybrid design, as the design does not facilitate high levels of regenerative braking or necessarily promote the use of smaller, lighter, more efficient internal combustion engines. this thesis introduces Starter-Generator used for this mild hybrid systems, which is called Hybrid Excitation Synchronous Motor(HESM). HESM combines the advantages of the PM machine and the wound rotor machine. the excitation flux in the machine produced by two different sources : the PMs and a DC field winding. Therefore, the flux can be weakened or strengthened by controlling the direction and value of field current. For this reasons, the superiority regarding high torque capability in low-speed region and wide speed operation range can be sufficiently achieved in HESM, thus HESM possesses considerable applicability for hybrid and electrical vehicle applications by using advantages of PMSM and WRSM.In this thesis, Maximum Torque Per Ampere(MTPA) control method that reflects varying according to the current in the low speed region below the base speed is proposed. Specifically, This thesis suggests Boost MTPA control strategy using Lagrange function for Hybrid Excitation Synchronous Motor(HESM), which can achieve higher copper loss reduction than Conventional MTPA control method.