An Improved Conventional Diode-Clamped Multilevel Inverter Using Non-Zero Triangular- Based Unipolar Modulation Scheme

Abstract

This paper presents an improved conventional diode-clamped multilevel inverter using non-zero triangular-based unipolar modulation scheme. The proposed scheme is meant to reduce the number of carrier waves, minimize the circuits of modulation scheme and obtain stabilized output voltage waveforms. Non-zero triangular-based unipolar modulation scheme is actualized by using two zero-free triangular wave carriers and two modulating sinewaves for line-to- line five level output voltage waveforms in single phase full bridge diode-clamped multilevel inverter unlike conventional multicarrier sinusoidal pulse width modulation that uses four triangular waves and one modulating sinewave for the same inverter type. The proposed system also used microcontroller in the combinational of its wave signals in order to generate the appropriate triggering signals for switching the power semiconductor switches. The proposed system has the following features: (i) It produces two distinct triggering trains (W1 and W2) meant to reduce the low and high harmonics unlike conventional modulation techniques (ii) All its carrier waves operate in continuous current mode which makes it unique from other multicarrier and other related modulation schemes (iii) it has low component counts. The proposed scheme on the conventional diode-clamped inverter produced the following results: voltage and current with total harmonic distortions of 0.4547%, stabilized 400V output voltage and 20A output current, probability results at each level of voltage and current occurrences are 0.10, 0.25, 0.25, 0.75 and 0.90; power output of 80kW, low component counts of modulation circuit scheme and experimental prototype.