Transformer Based Cascaded Multilevel Inverter with Reduced Number of Switches

This project presents the simulation of “transformer based cascaded multilevel inverter with reduced number of switches” with R-load and. It has the advantages of reduced number of switches and dc sources compared to conventional configurations and consequently higher efficiency. The simulation is accomplished for one stage (3-level), two stage (5-level, 7- level, 9-level), three stage (7-level, 11-level, 15-level, 19-level, 27-level) and four stage (29-level, 31-level, 33-level, 35-level). And their performance is analysed in terms of THD (Total Harmonic Distortion) for output voltages and currents. The FFT (Fast Fourier Transform) analysis is used in order to evaluate the harmonic distortion. The simulation is carried out by using MATLAB/SIMULINK software. Index Terms: cascaded asymmetric multilevel inverter, transformer-based cascaded multilevel inverter, balance of power distribution.

Pulse-Width Modulation Template for Five-Level Switch-Clamped H-Bridge-Based Cascaded Multilevel Inverter

This article presents a carrier-based pulse-width modulation (PWM) template for a 5-level, H bridge-based cascaded multilevel inverter (MLI). The developed control concept generates adequate modulation template for this inverter topology wherein a sinusoidal modulating waveform is modified to fit in a single triangular carrier signal range. With this modulation approach, classical multiplicity and synchronization of the triangular carrier signals criterion for the extension of sinusoidal pulse-width modulation, SPWM, to several cascaded 5-level, H-bridge-based MLI topology are removed. The proposed template can be used on the inverter configuration of any level with no further control modification. Nearly even distribution of switching pulses and equalized individual cascaded cell output power were achieved with the proposed modulation scheme. Three 5-level, H-bridge-based MLI units were cascaded for 1-phase, 13-level inverter operation; simulation and experimental results are adequately presented.

Symmetrical Cascaded Switched-Capacitor Multilevel Inverter Based on Hybrid Pulse Width Modulation

Multilevel inverters have been widely used in various industrial applications such as renewable energy generation and electric vehicles. An improved circuit of symmetrical cascaded switched-capacitor multilevel inverter is proposed so that the reactive power is absorbed by its power supply instead of capacitors. Then, a special hybrid pulse width modulation strategy combing level-shifted pulse width modulation (LS-PWM) and phase-shifted pulse width modulation (PS-PWM) was developed for the inverter. With this modulation algorithm, the power between cascaded units is automatically balanced, and the voltage of the capacitor in each unit is also automatically balanced to the dc input voltage. In addition, the optimized capacitor voltage ripple makes it possible to use a smaller capacitor to produce a better output voltage waveform. Theoretical analysis, simulation and experimental results show that the equivalent switching frequency of the cascaded multilevel inverter is twice the original frequency so that the output voltage harmonics are only distributed near even multiples of the carrier frequency.