Adaptive Piezoelectric energy harvesting circuit

This paper describes an approach to harvesting electrical energy from a mechanically excited piezoelectric element. A vibrating piezoelectric device differs from a typical electrical power source in that it has a capacitive rather than inductive source impedance, and may be driven by mechanical vibrations of varying amplitude. An analytical expression for the optimal power flow from a rectified piezoelectric device is derived, and an “energy harvesting “ circuit is proposed which can achieve this optimal power flow. The harvesting circuit consists of an ac-dc rectifier with an output capacitor, an electrochemical battery, and a switch-mode dc-dc converter that controls the energy flow into the battery. An adaptive control technique for the dc-dc converter is used to continuously implement the optimal power transfer theory and maximize the power stored by the battery. Experimental result reveal that the use of the adaptive dc-dc converter increases power transfer by over 400% as compared to when the dc-dc converter is not used.

Axial-field electrical machines abstract

Axial-field electrical machines offer an alternative to the conventional machines. In the axial-field machine, the air gap flux is axial in direction and the active current carrying conductors are radially positioned. This paper presents the design characteristics, special features, manufacturing aspects and potential applications for axial-field electrical machines. The experimental from several prototypes, including d.c. machines, synchronous machines and single-phase machines are given. The special features of the axial-field machine, such as its planar and adjustable air gap, flat shape, ease of diversification, etc., enable axial-fled machines to have distinct advantages over conventional machines in certain applications, especially in special purpose applications.

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AUTOMATIC SOLAR TRACKER .Electrical seminar topics

A new control scheme for a single – phase diode clamped rectifier is proposed to achieve a unity power factor, balanced neutral point voltage and constant DC-bus voltage. Four power switches are used in the rectifier to generate a three-level PWM wave form on the rectifier terminal voltage.The line current command is derived from a DC-link voltage regulator and an output power estimator. The hysteresis current Controller is used to track the line current command. To balance the neutral-point voltage, a capacitor voltage compensator is employed. The main advantages of using a three-level instead of a two-level PWM scheme are that the blocking voltage of each power switch is clamped to half the DC-bus voltage (if the off –state resistance of  power switches is equal),and the voltage  harmonic on the AC  side of rectifier is reduced.

AUTOMATED DISTRIBUTION SYSTEM With Full seminar Report

Distribution systems are usually composed of radial feeders. Each feeder is divided into load sections with sectionalizing switches and is usually connected to other feeders via normally open tie switches.

 When a fault occurs in the distribution system, it is firstly detected by protection relays, then a circuit breaker is opened and de-energizes the feeder where the fault exists. By operating sectionalizing switches, the faulted section is isolated and the un-faulted sections disconnected are re-energized after reclosing the circuit breaker.

As automation is introduced into the distribution systems, the above switching operations can become automated. Recent advances in digital technology have made possible the development of Distribution Automation System (DAS). The DAS offers many new opportunities for improved system operation. It provides an integrated system approach to monitoring, protection, and control.

 Distribution automation includes wide spread functions, among which feeder automation is an important aspect. By controlling line switches installed on the feeder, feeder automation functions can be accomplished by identifying and isolating permanent feeder faults and restoring service to the un-faulted feeder sections sequentially and automatically, and thus reduce significantly customer outage time. The distribution automation discussed in this paper is restricted to fault isolation, reconfiguration, and service restoration switching operations.
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