Performance Analysis of Modulation Strategies in Single-Phase HBNPC Inverter Across Variable Operating Conditions

Abstract

This study investigates the performance of a single-phase 5-level H-Bridge Neutral Point Clamped (HBNPC) inverter across various operating conditions. These conditions encompass variations in output power, frequency, modulation index, and modulation techniques. To adapt modulation strategies typically employed in three-phase inverter structures, we apply them to a single-phase HBNPC inverter. The modulation strategies under consideration include level-shifted (LS) based on phase disposition pulse width modulation (PD-PWM), third harmonic injection pulse width modulation (THI-PWM), space vector pulse width modulation (SV-PWM), and modified PWM (MPWM). These strategies are developed using different types of reference signals (RS) and carrier signals (CS). Initially, we analyze the inverter's output voltage and current waveforms across various modulation strategy states. Subsequently, we explore the relationships between efficiency, total harmonic distortion (THD), and variable output power across different modulation strategy states. We uncover distinct patterns between modulation strategy-THD, efficiency, and output voltage for maximum inverter output power. Furthermore, we examine the relationship between the modulation index and THD for each modulation strategy state, considering different switching frequencies. Additionally, we investigate the relationship between switching frequency and THD across different modulation index values, approaching the analysis from multiple perspectives.