A novel induction motor direct torque control (DTC) algorithm with synchronous modulation is presented. Compared to the traditional DTC method, whose main drawback is the presence of low-frequency torque harmonics (sub-harmonics), in the proposed method, the PWM switching frequency is imposed to be an integer multiple of the main supply frequency. This is achieved by continuously adjusting the PWM switching period to significantly reduce low-frequency harmonics. The devised algorithm has been tested on an inverter-fed induction motor drive system, and the obtained results show an important reduction of the sub-harmonic spectral content of the developed torque with respect to a conventional direct torque control while maintaining at the same time a high dynamic response.

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A new Cascaded Multilevel converter structure is proposed, which allows a remarkable reduction of the dclink voltage ripples, owing to the implementation of a new devised control strategy. The new topology uses only an additional controllable switch-diode couple for each basic H-bridge cell, with a small increment in cost and complexity of the converter system. Several results are presented, which confirm the validity of the proposed approach.Index Terms--Boost converter, cascade multilevel converter, dc-link filter reduction, medium voltage drives.

In this paper a self-commissioning procedure for direct-drive with elastic coupling based on Particle Swarm Optimization (PSO) and PI controller is presented. The solution is oriented to industrial plants which are usually based on DSP with low computational ability. Initially a model-based identification procedure is carried out to find the system parameters. Subsequently the controller parameters are optimized using a time-domain performance criterion. Experimental results are also presented to validate the work.

In this paper an exhaustive analysis of the utilization of the second harmonic component of the circulating currents in a modular multilevel converter for HVDC application is presented, with the aim of highlighting the effects on the maximum arm energy ripple, i.e. capacitors voltage ripple, and on semiconductor losses. Simulation results are presented and design remarks are indicated.