Comparing the performance of bipolar and unipolar switching frequency to drive DC-AC Inverter

The inverter is a device that is used as an interface between the photovoltaic energy and the grid. The harmonic and distortion of the output current, and efficiency of the inverter are the main issues. This paper presents a model of Sinusoidal Pulse Width Modulation (SPWM) methods of unipolar and bipolar inverters in MATLAB and Psim software. A numerical model of the LC filter is derived in order to design and test the DC-AC inverter. The SPWM control is created by comparing triangle signal (a carrier waveform) and a reference signal (a sine waveform) whose frequency is the desired frequency. The simple circuit is used to characterize the scheme of SPWM techniques in order to obtain the pure output voltage and reduce the harmonic component. Empirical results show that the unipolar switching scheme is used in widespread a commercial PV inverter in order to have the flexibility to choose a filter and reduce the harmonic components. The switching frequency of the Sunny Boy inverter is found around 15 kHz and its transformer is estimated. Unipolar switching SPWM is very useful in low switching frequency than bipolar switching SPWM. The output voltage and current in both techniques have been analyzed in frequency and time domains.