This paper presents a feed-forward torque controlud(FTC) technique for interior permanent magnet (IPM) brushlessudAC (BLAC) drives in traction applications. It is shown that byudadopting the Newton-Raphson iterative method for solving theudproposed high-order nonlinear relationship between the torqueuddemand, flux-linkage and desirable dq-axis currents, FTC withuddue account of nonlinear machine parameters can be achievedudfor IPM BLAC drives. It is also proven that the comparisonudbetween the reference voltage magnitudes under maximumudtorque per ampere (MTPA) and field-weakening (FW)udoperations together with online base speed determination can beudutilized for FW operation activation to achieve full exploitationudof the available DC-link voltage during the transition betweenudthe constant torque and FW operation regions. Since both the dqaxisudcurrent references and the base speed for FW operationudactivation are computed online, the proposed FTC techniqueudprovides flexibility for online parameter update or estimationudand is able to cope with wide DC-link voltage variation. Theudproposed FTC strategy is experimentally validated byudmeasurements on a 10kW wide constant power speed rangeud(CPSR) IPM BLAC machine drive.
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