Nonlinear controller for maximum power extraction in asymmetric multilevel DC link reduced switch count inverter-based grid connected PV system

Abstract

This paper presents the grid integration of reduced switch count (RSC)‐based asymmetric Multilevel DC‐Link (MLDCL) inverter for photovoltaic (PV) sys tem. Among the recently reported reduced switch count multilevel inverter (RSC‐MLI) topologies, MLDCL possess modularity, switching redundancies and fault tolerant capability. MLDCL can achieve multilevel output with signif icant reduction in switch count as compared to cascade H‐bridge (CHB). Sim ilar to CHB, the structure of MLDCL allows to develop a common control strategy to obtain maximum powers from equal rated PV sources so that con trol complexity can be reduced. In this connection, a robust nonlinear sliding mode control (SMC) is designed for MLDCL‐based PV system to extract maxi mumpower from each PV source. For this, a three‐phase asymmetrical eleven level MLDCL inverter with PV sources in 2:2:1 voltage ratio is considered. Therefore, two SMCs are developed to extract maximum power from each group of equal rating PV sources. The performance of SMC under variable irra diance conditions is verified against PI controller, and the results are analyzed in MATLAB and hardware‐in‐loop OPAL‐RT test beds.