In this study, an easily implementable and effective method in loss-minimisation control of interior permanentmagnet synchronous motors (IPMSMs) is proposed. Complication of loss-minimisation condition and its implementation are main problems in model-based control methods of IPMSMs. To resolve these problems, an approximate-model is used for simplification of loss-minimisation condition and a proportional-integral-controller is utilised to directly solve the loss-minimisation condition. Also, saturation and iron loss resistance variation due to frequency variation are considered in the proposed method. Furthermore, results show the high precision of the proposed method in comparison with accurate model. Steady-state performance of the proposed method is compared with look-up tablebased loss-minimisation and maximum torque per ampere (MTPA) control methods. Also, experimental results verify performance, good dynamic response and effectiveness in loss reduction of the proposed method under different conditions in comparison with look-up table-based loss-minimisation and MTPA control methods.

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In this study, a novel sensorless method for the induction motor control is proposed. In this method, magnitude and rotational speed of approximate stator flux vector are controlled. In the proposed approximate stator flux control (ASFC) method, utilisation of the mechanical sensors and current transducers is not required. Therefore implementation cost of ASFC is comparable with that of conventional v/f control method. In ASFC, in linear modulation range, to control rotating field speed and stator flux modulus, desired voltage vector components in line with and perpendicular to the stator flux vector are calculated. Based on these two components, three-phase voltages are applied to three-phase inverter using pulse-width modulation strategy. In addition, in overmodulation range, a switching-table-based approach is presented to control the rotating field speed by adjusting the stator flux modulus. The relationship between the stator flux modulus and rotating field speed is derived and it is shown that average switching frequency is calculable and under control. Through simulations and experiments, ASFC method is compared with v/f method in terms of motor behaviour in starting and steady-state operation. Also, correctness of presented formulas is validated by simulations and experimental results.

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The increasing use of medium-voltage drives and high-power equipment requires a detailed study on the switching method and topology of multi-level inverters. Asymmetric cascaded H-bridge topologies that have unequal input dc voltages with different devices in various parts of the cascaded H-bridge inverter (CHB) are representative of significant improvements in medium-voltage industrial drives. Various modulation strategies are used in multi-level power conversion applications. In the multi-carrier switching method for asymmetric CHB, the number of switches is less than carriers and is usually used in the offline switching method. These methods of switching are not applicable to online systems. In this study, equations for combining different pulse-width modulation (PWM) to use the controllability advantage of the multi-carrier method are introduced in asymmetric topologies. Then, the dual Fourier series equations are applied to model each inverter switching relation of the asymmetric cascaded blocks. To model each inverter switching relation of the asymmetric blocks using sinusoidal PWM, the dual Fourier series equations were applied. The presented analytical modelling switching method was validated using simulation and experimental case studies.