A Comparative Study of Three Topologies of Three-phase (5L) Inverter for a PV System

Abstract

In this paper, we present a comparative study in the Matlab/Simulink environment between three topologies of three-phase multilevel inverter MLI (five-level). We will consider the Flying Capacitor Multilevel Inverter (FCMLI), the Neutral Point Clamped Multilevel Inverter (NPCMLI), and the Cascaded H-Bridge Multilevel Inverter (H-bridge MLI). The comparison between these inverters is based on some criteria: the spectral quality of the output voltage, the complexity of the power circuits and the cost of implementation. Each inverter is controlled by the same type of control which is the multi-carrier sinusoidal pulse width modulation (SPWM). Voltage sources supplying the inverters cells are simulated by a DC voltage representing photovoltaic panels (PV). We have chosen the 5L inverter because it is the most widespread. In literature, there is works dealing on a single topology with several levels, or developing a new topologies, or achieving a sophisticated control dedicated to very specific topologies. This study focuses on a comparison of three topologies bases. These topologies are simpler and easily controlled in an analog or digital manner. This study shows, on the one hand, that the total harmonic distortion (THD) is approximately 32% for NPCMLI and PWM H-Bridge topologies, and it is about 36% for the FCMLI topology. Moreover, the distortion factor (DF) of the FCMLI is smaller (0.94) than the NPCMLI and H-bridge (0.951). In addition, the rays spectrum are concentrated on the switching frequency (2500Hz) for the three topologies. On the other hand, the H-bridge MLI topology has fewer components compared to the others. Our study confirms that the most promising topology for photovoltaic systems is the PWM H-bridge one in view of the spectral quality, the phase shift (2π/3) between voltages, the waveform of the composed output voltage and the cost.