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.

Computer Simulation and Implementation of Stiff DC Input Voltages of Cascaded Multilevel Inverter from Single-Phase Grid Supply

“…Any over-voltage occurrences across any of the inputs of the cascaded multilevel inverters will lead to disconnecting the supply through relayed-controlled logic scheme. The single phase supply voltage is represented as in eq.1 [1], [10]…”

“…The stiff input voltages to the input of the multilevel inverters enhance the performance stability of the synthesized staircase of output voltage levels. Therefore, fluctuations of input power per current are the major problems that bring about imbalances at output waveforms of the cascaded multilevel inverters [1]- [3]. The authors in [4] worked on cascaded full bridge converter dependent on current source Inverter with direct current that links magnetically fixed to minimize the direct current inductor value.…”

Effect of supply voltage variations on single-phase capacitor clamped multilevel inverter fed induction motor drive

“…A three-level diode clamped inverter topology has been reported in [17], [18]. The configuration of the cascaded H-bridge multilevel inverter [19]- [22] is a series connection of conventional single-phase inverters with separate dc sources. This system enables unequal values of different DC voltage sources.…”