THD minimization for Z-source-based inverters with a novel sinusoidal PWM switching method

Abstract

This paper presents a modified sinusoidal pulse width modulation (SPWM) switching method for one-phaseand investigated two-phase impedance-source inverter structures. The proposed structure generates pulses for a quasiZ-source converter and this block produces a unilateral voltage sine wave in the block’s output. This signal is appliedto the inverter as its input wave. For this purpose, the novel SPWM method is proposed for power switches whilebeing switched complementarily. Two power switches are used in the structure to generate the pure sinusoidal outputvoltage and to minimize total harmonic distortion (THD), which is an essential parameter in inverter design. The resultsshow that the proposed method generates the pure sinusoidal voltage and current signals for resistive and inductiveloads and pure voltage and improved current waves for capacitive loads in comparison with existing techniques, sincethe THD of the output voltage and current signals is strongly affected by the dynamic loads. This method leads tofinal cost improvement and reduction of the size of the system with fewer number of components, which are essentialparameters for renewable energy resource applications. A mathematical model is validated with the 2017a version ofMATLAB/Simulink and 1.51% and 1.33% THD values are reported for low and high power loads, respectively, in theone-phase structure and 0.95% and 0.87% in the two-phase system. Finally, a 120 W prototype has been implementedand tested. A sine-wave with 620 Vac peak to peak amplitude and 50 Hz frequency has been gained in the inverter’soutput and the quality of the voltage and current waveforms has been evaluated for different two 1.8 kΩ and 600 Ωresistive loads in the one-phase structure. Experimental results confirm all mathematical and simulation results.