• SOUMITRA DAS

      Articles written in Sadhana

    • Analytical evaluation of DC capacitor RMS current and voltage ripple in neutral-point clamped inverters

      K S GOPALAKRISHNAN SANTOSH JANAKIRAMAN SOUMITRA DAS G NARAYANAN

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      The sizing of the DC-link capacitor in a three-level inverter is based on the RMS current flowing through it. This paper analyses the DC-link capacitor RMS current in a neutral-point clamped (NPC) inverter and expresses the same as a function of modulation index, line-side current amplitude and power factor. Analytical closed-form expressions are derived for the capacitor RMS current for single-phase half-bridge,single-phase full-bridge and three-phase three-leg topologies of a three-level inverter. The worst-case capacitor current stress is determined for each topology based on the analytical expressions. Further, analytical expressions are derived for the RMS values of low-frequency and high-frequency capacitor currents. These expressions are then used to estimate voltage ripple across the DC capacitor for sinusoidally modulated three-phase NPC inverter. The analytical expressions for the RMS current and voltage ripple are validated experimentally over a wide range of operating points.

    • Extending lifetime of wireless sensor networks using multi-sensor data fusion

      SOUMITRA DAS S BARANI SANJEEV WAGH S S SONAVANE

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      In this paper a multi-sensor data fusion approach for wireless sensor network based on bayesian methods and ant colony optimization techniques has been proposed. In this method, each node is equipped with multiple sensors (i.e., temperature and humidity). Use of more than one sensor provides additional information about the environmental conditions. The data fusion approach based on the competitive-type hierarchical processing is considered for experimentation. Initially the data are collected by the sensors placed in the sensing fields and then the data fusion probabilities are computed on the sensed data. In this proposed methodology, the collected temperature tand humidity data are processed by multi-sensor data fusion techniques, which help in decreasing the energy consumption as well as communication cost by fusing the redundant data. The multipledata fusion process improves the reliability and accuracy of the sensed information and simultaneously saves energy, which was our primary objective. The proposed algorithms were simulated using Matlab. The executions of proposed arnd low-energy adaptive clustering hierarchy algorithms were carried out and the results show that the proposed algorithms could efficiently reduce the use of energy and were able to save more energy, thus increasing the overall network lifetime.

    • Analysis of generalized continual-clamp and split-clamp PWM schemes for induction motor drive

      SOUMITRA DAS V S S PAVAN KUMAR HARI ARUN KUMAR G NARAYANAN

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      Continual-clamp pulse width modulation (CCPWM) clamps each phase of a three-phase inverter to one of the two dc buses continually for 60°duration in each half of the fundamental cycle. Split-clamp pulse width modulation (SCPWM) divides the 60° clamping interval into two sub-intervals, which are not necessarily equal, and falling in two different quarter cycles. Whether continual clamp or split clamp, the positioning of the clamping interval in case of CCPWM, and the ratio of splitting the clamping interval in SCPWM – all influencethe waveform quality of the inverter output. This paper derives analytically closed-form expressions for the total RMS harmonic distortion factor and torque ripple factor pertaining to CCPWM with any arbitrary position of the clamping interval (i.e., generalized CCPWM) and also corresponding to SCPWM with any arbitrary ratio of splitting of the clamping interval (i.e., generalized SCPWM). The analytical results are well supported by experimental results on 3-hp and 5-hp induction motor drives.

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