21 Multi-level Inverters based on Cascaded H-Bridge Converter using Nearest Level Modulation

Abstract

In recent years, due to the increasing demand for electricity from grid users and the emergence of high-power energy-consuming industries, the energy demand from society for grids has significantly increased, which has led to an increase in the global power generation from traditional energy sources. Therefore, the penetration of renewable energy (wind power, photovoltaic power) resources into the grid has increased significantly, making the grid unstable due to fluctuations in its output. In order to overcome grid fluctuations, this research proposes 21 multi-level inverters (MLI) based on cascaded H-bridge inverters to solve the problems mentioned above in large-scale energy storage systems. This article focuses on the number of components in a variety of multi-level converters with different topologies (neutral point clamped inverter (NPC), flying capacitor inverter (FC), cascaded H-bridge multi-level converter), the control program and the complexity of the hardware circuit, the power state and the system loss are studied and compared, and the inverter with the cascaded H-bridge as the main topology is established and its characteristics are studied. This paper depicts the three different modulation techniques, namely phase-disposition sinusoidal pulse width modulation (PD-SPWM), carrier phase shift pulse width modulation (CPS-SPWM), and nearest level modulation (NLM) applied to modular Multiple Stage (MMCs). It further details the implementation and analysis of each modulation technique. The performance of 5,7,9,11,13,15,17,19 and 21 level MMC with three aforementioned modulation techniques is evaluated and compared in terms of output voltage, current and harmonic distortion. The simulation is carried out using Matlab/Simulink software. The simulation results are presented and validated.