Abstract-AC-to-DC converters based on one-cycle control exhibit instability in current control at light load conditions as well as when they are operating in the inverting mode. In this paper, a modified one-cycle controller for bidirectional ac-to-dc converter is proposed. A fictitious current component in phase with the utility voltage is synthesized. The sum of this current component and the actual load current is compared with the sawtooth waveform to generate the gating pulses for the switches. This modification not only renders stability to the converter at light load conditions and the inverting mode of operations but also enables the converter to seamlessly transfer its operation from the rectifying mode to the inverting mode and vice versa. Detailed simulation studies are carried out to verify the effectiveness of the proposed scheme. To validate the viability of the scheme, detailed experimental studies are carried out on a 2-kW laboratory prototype.Index Terms-Bidirectional ac-to-dc converter, high-powerfactor converter, improved light load stability, one-cycle control (OCC).
Experimental measurements of torque, traverse force and thermal cycles in friction stir welding (FSW) are challenging due to the simultaneous rotational and linear motions of the tool and the deformation of workpiece material around the tool pin. We propose here a methodology to measure the torque and the traverse force by monitoring the current and power transients of the electrical motors that drive the rotational and linear motions of the FSW tool respectively. The measured values of torque and traverse force in FSW of AA 7075-T6 and AA 2524-T351 at different combinations of tool rotational speed and tool shoulder diameter are validated with the corresponding computed results from a well tested numerical model. The proposed method alleviates the need to use expensive torque and force dynamometers, and provides an economical and robust route for indirect measurement of real time torque and traverse force in FSW.
Abstract-In this paper, a simple control strategy for an optimal extraction of output power from grid connected variable speed wind energy conversion system(VSWECS) with reduced switch count power converters is presented. In order to improve the overall efficiency and to reduce the cost, B-4 PWM converters are used. The system consists of a variable speed wind turbine coupled to a permanent magnet synchronous generator(PMSG) through a gear box, two PWM B4-power converters. Output power from PMSG is first converted into dc and then it is fed to the grid. Both the power conversions are performed at unity power factor and the de link voltage is maintained constant. The (MPF'T) extracts optimum power from the wind turbine from cut-in to rated wind velocity by sensing only the turbine output power. The complete system has been simulated for various wind velocities. The control algorithm is implemented on TMS320F243 DSP and the simulated results are validated by experimental results.
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