Single Phase Multi Level Inverter Design for Resistive Load

Abstract

The need for multilevel inverters has grown rapidly in recent years, particularly in applications involving high power and high voltage. Their ability to generate output waveforms that closely resemble a pure sine wave makes them highly effective in minimizing harmonic distortion and enhancing overall power quality.This paper presents the design and development of a five-level cascaded H-bridge multilevel inverter, realized through MATLAB/Simulink simulations as well as a hardware prototype driven by a microcontroller. The cascaded H-bridge configuration is chosen because of its modular structure, ease of control, and capability to produce higher output voltages using medium-voltage switching devices. By producing multiple voltage steps that shape a smoother sinusoidal waveform, the proposed system successfully lowers switching losses, improves output waveform quality, and offers strong potential for use in high-power industrial systems and renewable energy applications.

Introduction

Power electronic circuits are critical in modern energy systems, particularly for renewable energy integration, where they convert, regulate, and control electrical power. Multilevel inverters (MLIs), especially cascaded H-bridge (CHB) topologies, have gained prominence in medium- and high-power applications due to their ability to produce multiple voltage steps. This results in reduced harmonic distortion, lower switching losses, improved voltage handling, and enhanced electromagnetic performance. The number of voltage levels is determined by the number of isolated DC sources, following n=2s+1n = 2s + 1n=2s+1. For example, a five-level inverter uses two H-bridge modules in series.

Objective

The project aims to design and implement a five-level cascaded H-bridge inverter that converts DC to AC with improved power quality. Key goals include generating a smooth sinusoidal waveform, reducing harmonics, enhancing conversion efficiency, and validating the system through both MATLAB/Simulink simulations and hardware testing.

Cascaded Multilevel Inverter

Cascaded MLIs consist of multiple H-bridge cells connected in series, where each cell contributes a portion of the output voltage. This modular design offers advantages such as fewer switches, simplified scalability, easier maintenance, fault isolation, and suitability for high-power and renewable energy applications.

Literature Insights

• Increasing voltage levels improves waveform quality but adds design complexity.

• SPWM control strategies enable precise switching and eliminate the need for complex phase-locked loops.

• MATLAB simulations confirm reduced Total Harmonic Distortion (THD) for 5-, 7-, and higher-level configurations.

Methodology

The methodology included:

1. Theoretical study of five-level CHB inverters and PWM-based control.

2. Simulation in MATLAB/Simulink to analyze output waveform, switching behavior, and harmonic performance.

3. Hardware implementation using MOSFETs (IRFZ44N), TLP250 gate drivers, Arduino UNO (ATmega328P), isolated DC sources, rectifiers, LC filters, and associated circuitry.

4. Experimental verification capturing stepped AC waveforms and validating switching accuracy, waveform smoothness, and operational stability.

Hardware Design Highlights

• Modular two H-bridge cells for five voltage levels: +Vdc, +Vdc/2, 0, –Vdc/2, –Vdc.

• Independent DC sources provide flexibility and improved control.

• PWM-based switching ensures precise waveform synthesis and reduced switching losses.

• LC filter smooths the stepped waveform into a near-sinusoidal AC output.

Simulation and Results

MATLAB/Simulink simulations verified the expected five-level output waveform with significant harmonic reduction. Scope analysis confirmed waveform smoothness, demonstrating the inverter’s efficiency and reliability.

Advantages

• Improved output waveform quality and reduced THD.

• Modular, scalable, and versatile design.

• Reduced stress on switching components, enhancing safety and reliability.

• Compatible with multiple DC sources and adaptable to renewable energy systems.

Future Scope

• Integration with renewable sources like solar or wind for sustainable energy applications.

• Optimization for single DC source operation.

• Industrial real-time deployment for smart-grid applications.

Conclusion

Multilevel inverters play a crucial role in modern power conversion systems, especially in applications requiring high voltage and high power such as industrial drives, power transmission, and transportation systems. Among different topologies, the cascaded multilevel inverter stands out due to its flexibility, modular structure, and improved output waveform quality. In this project, a five-level cascaded inverter was successfully modeled in MATLAB/Simulink and implemented in hardware using an ATmega328 microcontroller. The output waveform was verified using a CRO, and the results confirmed that the hardware closely matched the simulation, proving the effectiveness of the design and its potential for real-world applications.

References

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Copyright

Copyright © 2025 Tarakeshwari V, Roshan Naika S, Raghavendra M, Ullasgouda V Patil, Tilak S. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.