Seven-Level Cascaded H-Bridge Multilevel Single-Phase Inverter Implemented with an ATMEGA Microprocessor

An inverter is a power electronics circuit that can convert DC power into AC power. Inverters have a wide range of applications, from battery-powered devices to renewable energy systems such as photovoltaics. Typically, inverters rely on switching devices to create an AC signal. In most cases, these switching devices are arranged in the form of an H-bridge, the circuit topology taking its name from the arrangement of the switching devices. Although most inverters rely on utilizing a single H-bridge to achieve either two or three voltage levels, the use of multiple H-bridges increases levels as well as voltage. This proves to be advantageous when trying to reduce total harmonic distortion (THD). A low-cost multilevel (ML) single-phase inverter based on a cascade of H-bridge connections and PWM voltages was developed using an ATMEGA microprocessor. The ML inverter can supply up to 30 W with an RMS output voltage of 120 V, 60 Hz, and a THD less than 30% without a lowpass filter. An 18 V battery per level provided the primary DC voltage. This document presents simulation and experimental results when the ATMEGA-based inverter prototype was tested under various lighting load technologies, including linear loads such as filament and nonlinear loads such as compact fluorescent lighting (CFL) and light-emitting diode (LED).