Loss minimization control of interior permanent magnet motor drives

In this thesis a novel on-line adaptive loss minimization control strategy for electric motor drives is introduced. Based on this strategy an adaptive loss minimization controller (ALMC) is proposed for inverter-fed interior permanent magnet (IPM) motor drives after the minimum loss operation of one of these motors is analyzed. The ALMC provides a new pattern of change in d-axis stator current to achieve a minimum drive input power at any operating condition. Gaining insight from the analysis of the motor speed variations in response to the changes in d-axis current, a concept of forced compensation is introduced. Using this concept a non-linear speed controller (NLSC) is proposed to achieve desirable motor dynamics in transient state and maintain the output power constant in steady state while the input power is being reduced by the ALMC. The harmonized operation of the ALMC and the MSC results in a smooth and fast system performance thus overcoming the major drawbacks of other on-line loss minimization control approaches like the torque pulsations and a long search time to reach a minimum input power. The proposed loss minimization strategy provides more energy saving in comparison with other methods and extends the application of loss minimization control to a new class of motor drives requiring an efficient and smooth operation in the face of frequent changes in the operating point like in electric vehicles. The analysis, design, simulation, DSP implementation and extensive test results of a current vector control system including the proposed ALMC and NLSC, when applied to an experimental 1 hp IPM motor drive are presented in detail. The simulation confirmed by the experimental results proves the validity of this new loss minimization control strategy.