Design of SPWM control unit based on microcontroller for photovoltaic inverters

This paper presents a new technique to generate a digital Sinusoidal Pulse Width Modulation (SPWM) control using PIC16F876 microcontroller. This technique is mainly used to control the DC/AC inverter output voltage in many applications such as photovoltaic pumping system and motor drive. It reduces significantly low harmonic components as well as distortion factor. The principle of this method is to transform the sampled dc-biased sine wave signal to a repeating pulses train. The widths of these pulses vary sinusoidally and thus as adigital SPWM. The different amplitude modulations index started from 0.5 unti11.3 (over modulation) with 1 kHz switching frequency was implemented and tested. The literature review of the existing digital SPWM techniques is presented firstly. Subsequently the proposed SPWM approach is briefly detailed. Finally, experimental results are presented to demonstrate the validity of this SPWM method and the good functionality of the realized control unit.