A new control technique for achieving wide constant power speed operation with an interior PM alternator machine

A new flux weakening control algorithm is presented for achieving wide constant power operation with an interior permanent magnet (IPM) synchronous machine operating as an alternator. The algorithm is designed to initiate flux weakening only when necessary by recognizing the threshold conditions for current regulator saturation, making the algorithm inherently adaptive to changes in the inverter bus voltage. A 6 kW 42 V automotive integrated starter/alternator (ISA) using a direct-drive IPM machine serves as the target application for this development. Simulation results show that the new algorithm is capable of delivering very good static and dynamic bus regulation characteristics over a 10:1 engine operating speed range. Tests are presently under way to confirm these performance predictions using a prototype IPM starter/alternator system.