Cascaded Multilevel Inverters (CMIs) play a
crucial role in renewable and medium-voltage systems due
to their high efficiency and excellent harmonic
performance. However, selecting the proper switching
frequency remains a critical design challenge, as it directly
affects converter efficiency, harmonic distortion, and
semiconductor thermal reliability.
This paper presents a comprehensive analytical–
simulation framework developed in MATLAB/Simulink to
determine the optimal switching frequency range for a
nine-level cascaded H-bridge inverter. The methodology
integrates loss modeling, harmonic spectrum analysis, and
electro-thermal evaluation within a unified platform,
enabling quantitative correlation between switching
frequency, total efficiency, total harmonic distortion
(THD), and device junction temperature.
Simulation results demonstrate that at an optimal
switching frequency of 2.7–3.0 kHz, the inverter achieves a
balanced trade-off between key performance metrics:
efficiency improves to approximately 96.8%, voltage THD
decreases to 1.7%, and the average junction temperature
rise is limited to 58 °C, representing a thermal stress
reduction of nearly 22% compared to higher-frequency
operation.
The novel contribution of this work lies in establishing a
multi-criteria optimization-based frequency selection
approach that simultaneously considers efficiency,
harmonic quality, and thermal constraints. This integrated
methodology provides a practical design guideline for grid-
connected and renewable-energy CMI applications,
enhancing both performance and long-term reliability.
This paper introduces a comprehensive analytical–
simulation framework to determine the optimal switching
frequency region for nine-level CMIs. The proposed
approach integrates loss modeling, harmonic analysis, and
electro-thermal evaluation within a unified
MATLAB/Simulink platform. Unlike previous works that
treat these parameters separately, the presented model
quantitatively correlates switching frequency with total
efficiency, THD, and semiconductor junction temperature.
Simulation results validate the analytical trends, showing
that the optimal operating range lies between 2.7–3.0 kHz,
where efficiency (≈96–97%) and THD (≈1.7%) achieve a
balanced trade-off without excessive thermal stress. The
novelty of this study lies in formulating a multi-criteria
optimization-based frequency selection methodology that
simultaneously considers efficiency, harmonic quality, and
thermal reliability—providing a practical design guideline
for CMI-based power systems. |
