Vinod John

Research Highlights

General Purpose Inverter Stack

A pulse width modulation (PWM) based power converter is the prime component in many power electronic applications, and particularly in renewable energy based distributed generation (DG) systems. Insulated gate bipolar transistor (IGBT) is the semiconductor device of choice for converters whose power rating exceed 2kW. With advancement in IGBT technologies and the growing need to minimize system size and weight, design based on discrete IGBT devices is now an attractive alternative to the conventional module based design approach. A General Purpose Inverter Stack (GPIS) is presented for a state-of-the-art general-purpose power converter of 20kVA rating, which comprises of a 2-level converter in three-phase-four-leg configuration, that would facilitate students to practically realize different power converter topologies as required that are typical for renewable energy conversion process. The GPIS can be used in three-phase, three or four wire, single-phase and in non-isolated dc-dc power conversion applications.

Name of the people involved: Student –  Shimul K Dam

Soft-switched modular equalizer circuit for batteries and hybrid ultracapacitors

Battery voltage equalizer circuit is an essential part of many energy storage systems. It makes the cell voltages equal in the case of series connected battery stack to avoid overcharging or over-discharging. A fastcell-to-cell voltage equalizer topology is designed that can operate with extremely rapid charging and discharging environments. The equalizer has a modular structure consisting of one power converter leg for each battery which results in lower cost. Capacitors are used to block dc voltage for ground reference shifting, rather than magnetic isolation, leading to lower energy loss and high power density. This equalizer can transfercharge among multiple batteries in a string simultaneously or selectively resulting in fast equalization with minimal cycling of energy. The equalizer also performs well in fast charge and discharge cycles that are experienced by hybrid ultracapacitor banks.

Solid State Crowbar

Microwave tubes require protection to prevent system failure and economic loss. A fast-acting crowbar can be used for this. The solid-state crowbar (SSC), shown in the picture, is designed and developed at IISc-Bangalore and CDAC-Thiruvananthapuram. It is India’s first 10kV, 10 MegaWatt pulse-power SSC for MWT protection. The SSC is currently in operation at the Institute for Plasma Research, Ahmedabad.