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Due to the increase in electronic loads such as LED lamps, power supply units for computing loads, voltage frequency drives in industries; high-frequency distortion is introduced into the power system. These high-frequency components appear due to the switching components of different power electronic converters present in the mentioned loads. The switching frequency components are most often in the range of 2 kHz to 150 kHz referred to as supraharmonics. The paper aims to show, with simulations and measurements, how supraharmonics sum in neutral and to quantify the neutral supraharmonic current as a ratio of single-phase current. This paper defines characteristics of supraharmonic emission that influence their summation in the neutral conductor through studies of devices connected in a balanced three-phase four-wire system. The paper further defines the relation of the supraharmonics emission with the number of devices connected at each phase. A mathematical model to predict the supraharmonics in a neutral conductor based on single-phase current and the number of devices further proposed.

The bi-directional DC-DC converter has many applications, such as in hybrid vehicles, solar inverters, in power supplies for microprocessors etc. A bi-directional dc-dc converter can be alternately operated as a step down converter in one direction of energy flow and as step up converter in reverse direction of energy flow, which is from source to load and load to source. A high power supply using a single converter is not preferred as it leads to high ripple in output voltage and current, thus requiring large value of inductor and filter capacitor. To overcome these limitations multiphase interleaving technique is used in bi-directional DC-DC converters i.e. connecting the converters in parallel with the switching instants equally distributed among them. This paper presents the simulation and implementation of two phase bi-directional dc-dc converter.

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