Analysis of 7-Level Cascaded & MLDCLI with Sinusoidal PWM & Modified Reference PWM Control Methods

Multilevel inverter offers several advantages compare to the conventional three phase bridge inverter in terms of lower dv/dt stresses, lower electromagnetic compatibility and better THD features. The primary use of DC to AC conversion & speed control of machines also voltage controller and reduce the harmonics in the levels of inverter by using cascade multilevel inverter. This paper presents a comparison of cascaded and multilevel dc link inverter (MLDCLI) Using only a DC power source and capacitors. A MLDCLI can be constructed by the series connection half and full bridge cells each having its own DC source .A multilevel voltage source inverter can be formed by connecting an MLDCL with a single bridge inverter. The MLDCL provides a DC voltage with the shape of a staircase with or without pulse width modulation (PWM) to the bridge inverter, which in turn alternates the polarity to produce an AC voltage. compared with the cascaded multilevel inverter, The MLDCLI can significantly reduce the switch count as the number of voltage levels increases beyond five for a given number of voltage levels , m , the required number of active switches is 2(m -1) for the existing multilevel inverter but is m+3 for the MLDCL inverters. This paper presents the performance of a seven level cascaded multilevel inverter &MLDCLI Based on a sinusoidalPWM and modified Reference PWM control techniques. Performance analysis is made based on the results of simulation study conducted on the operation of the cascaded & MLDCLI using MATLAB/SIMULINK. The performance parameters chosen in the work include the waveform pattern harmonic spectrum, fundamental value & total harmonic distortion (THD) of the three phase cascaded H-Bridge MLI & MLDCLI.