Maximum voltage angle optimization of uninterruptible power supply on three-level transformer-less photovoltaic inverter

This paper presents a new topology of three-level transformer-less photovoltaic (PV) inverter. In this topology, a 240V AC system is developed from a full bridge inverter circuit using PIC microcontroller (PIC16F628A-I/P) connected to an array of PV panel through a power factor correction circuit. The output waveform of the inverter depends on the type of pulse driver. The inverter is connected to the utility supply, on the clear day, the ac load is served by the inverter but on the cloudy day or night where solar irradiance is low, the inverter through its PIC microcontroller automatically changes from the usage of inverter to the utility supply. Objective of this paper is to optimize the maximum voltage angle to obtain the lowest current total harmonic distortion (CTHD) of the uninterruptible power supply (UPS) on the three-level single phase transformer-less inverter. In this paper, the maximum voltage angle optimization of the AC three-level waveform transformer-less PV inverter is developed and created by a microcontroller PIC16F627A-I/P changing maximum voltage angle of the AC three-level waveform from 20° to 180°. Resistive load of 30 W lamp and inductive load of 20 W water pump are applied to the transformer-less PV single phase inverter. The result shows that the lowest CTHD of 15.448% is obtained when the maximum voltage angle is 134°.