Control of a Single-Phase Cascaded H-Bridge Multilevel Inverter for Grid-Connected Photovoltaic Systems

TLDR

The multilevel topology uses several series‑connected H‑bridge cells, each linked to a PV module string. The paper introduces a single‑phase cascaded H‑bridge converter for grid‑connected PV systems. The converter uses a control scheme that independently regulates each dc‑link voltage to track the maximum power point of each PV string, with simulation and experimental validation across various operating conditions. The topology delivers low‑ripple sinusoidal currents with near‑unity power factor and operates at lower switching frequencies and current ripple than conventional two‑level converters.

Abstract

This paper presents a single-phase cascaded H-bridge converter for a grid-connected photovoltaic (PV) application. The multilevel topology consists of several H-bridge cells connected in series, each one connected to a string of PV modules. The adopted control scheme permits the independent control of each dc-link voltage, enabling, in this way, the tracking of the maximum power point for each string of PV panels. Additionally, low-ripple sinusoidal-current waveforms are generated with almost unity power factor. The topology offers other advantages such as the operation at lower switching frequency or lower current ripple compared to standard two-level topologies. Simulation and experimental results are presented for different operating conditions.