PV-Powered Grid-Tied Fault Tolerant Double-Stage DC-AC Conversion Chain Based on a Cascaded H-Bridge Multilevel Inverter

Abstract

This paper is dedicated to a comprehensive study of a complete DC/AC conversion chain. Motivated by the high power demand of a variety of industrial applications, this work puts an emphasis on a double stage conversion system composed of N photovoltaic energy supplies, N DC-DC boost converters, a DC-link containing N capacitors, N H-bridge inverters connected in cascade forming the core of the structure, an LCL filter and an electrical grid. With the use of an appropriate regulator, the following control objectives are aimed to be achieved: i. the extraction of the maximum available power via the regulation of the voltage across the PV panels, ii. the fulfillment of a unitary power factor, iii. the regulation of the DC-link voltage to a desired reference. Reaching the pre-mentioned objectives requires the design of a multi-loop regulator that upgrades the features of the system under investigation to work under matching and mismatching irradiations efficiently thanks to the individual control of each PV module. As for the power factor correction (PFC) requirement and the DC link regulation, two cascaded loops are developed. The designed regulator in this study is based on the sliding mode control strategy combined with Lyapunov theory. The controlled system's performances are examined by means of simulation on Matlab/SimPowerSystems environment. The obtained results prove the effectiveness of the designed controlled system and demonstrate the fault tolerance property of the conversion chain.