Dc bus for photovoltaic power supplying computing loads

Michael Ikerionwu4th year Electronic Engineering

Project AimsThe aim of this project is to investigate if

efficiency of power delivered from a domestic PV installation can be improved by supplying such DC load through a DC bus instead of through an AC grid connection.

Progress till dateReview and research on PV panels

characteristics and circuit models

Review of PV inverters (including MPPT).

Review of power consumption of a range of DC loads.

Spice simulation of AC/DC converter such as full wave rectifier.

PV PanelsPV panels are devices that convert solar

energy directly to electricity.Consists of semiconductors poly crystalline

silicon and amorphous silicon.Light is absorbed by semiconductors which

cause electrons to move resulting in current.Solar cell model with current source and

diodes.

PV PanelsEfficiency is generally between 6 and 20%.Fossils fuels use to be main source of energy

for several generations.The use of PV panels is not viable due to high

cost of installation and upkeep of PV modules.Nowadays PV systems are becoming a truly

viable option for everyone.

I-V characteristic

PV invertersUsed for DC/AC conversionThree different types of inverters: stand

alone, grid tie and battery backup inverters. Stand alone – draws DC energy from

batteries charged by PV arrays. Battery back up –draw energy from battery and provide back up power during utility. Grid tie – designed to shut down automatically upon loss of utility supply for safety reasons and do not provide backup power.

Solar inverters uses MPPT to deal with PV arrays.

Maximum power point trackingHigh efficiency DC/DC converter converts

power by PV cells to voltage or current depending on what it is suitable for.

Used to get the maximum power from PV arrays.

Advantages is that MPPT regulators can be used during cold and cloudy weather.

Can be used with or without batteries.

Power consumption of DC loads

MPPT I-V characteristic

Full Wave rectifier

FWR simulation

Buck converter