 Single-Phase Five Level Modified Neutral Point Clamped Grid-Tied Inverter Topology with a Front-End Multilevel Boost Converter

Abstract

Traditionally, the standalone performance of a single-phase fault-tolerant five-level neutral-point-clamped inverter (5L-NPC), powered by two rigid direct current (DC) sources, has been examined with an emphasis on the level shifted pulse width modulation (LS-PWM) method. In this configuration, the bidirectional switch setup incorporates four diodes and a single IGBT switch, which inherently leads to higher conduction losses in the system. Typically, NPC inverter topologies face challenges related to the balancing of DC-link capacitor voltages (DCL-CVs). In recent studies, researchers have addressed the front-end voltage balancing challenge by employing a dedicated control strategy, which necessitates the use of voltage sensors for implementation. This research presents an advancement in single-phase grid integration using a modified five-level neutral point clamped (M5L-NPC) inverter topology, addressing the previously mentioned issues. In this configuration, a front-end multilevel boost converter (FE-MLBC) is employed to autonomously balance the DCL-CVs while achieving voltage boosting with a reduced duty cycle. This paper discusses the operation of the M5L-NPC topology in both standalone and grid-connected modes, including the self-regulation of DCL-CVs. The grid-connected system's key objectives, such as reactive power control (RPC), active power control (APC), and the injection of sinusoidal current with minimal harmonic distortion, are comprehensively analyzed using a straightforward simple proportional resonant (PR) based control approach