Abstract:
Some of the countries around the world including Sri Lanka are facing crucial problems
on supplying electricity due to the economic crisis generated by Covid-19 pandemic. It
has caused frequent power outages which dramatically affects daily life. This research
work highlights an off-grid inverter system which can be used in such situations where
it converts 12V DC battery voltage into 230V, 50Hz AC. The output can be used to
power up the home appliances without performing many modifications to existing electrical
installations. The 12V DC supply is fed into a boost converter and subsequently
connected to a center-tapped step-up transformer with two complementarily operated
MOSFETs which converts DC supply into AC. MOSFETs are switched using switching
signals generated from the Atmega328P microcontroller. Square wave-based inverter
model was realized in this research project. To separate the signal side from the power
side, opto-isolators were used. Input of those was connected to the microcontroller. A
software implemented deadtime was introduced to prevent any shoot-throughs. Two
separate auxiliary power supplies were used on the output sides of the opto-isolators
to drive the MOSFETs. Upon testing, it was found that this system can maintain a
230V output even when the battery voltage drops to 9V thanks to the boost converter.
Moreover, this system is capable of detecting power outages itself and automatically
switches on the backup power and switches off the backup power when mains power is
available because of the feedback sensors attached to the system.
