Sliding mode controller for extraction and supply of photovoltaic power using switched series parallel sources reduced switch count multilevel inverter

Abstract

The reduced switch count multilevel inverter (RSC-MLI) is the latest trend in power electronic converters due to reduction in the switch count and cost. However, a large number of RSC-MLIs have not yet reached to the application level because of the absence of modularity, unequal load-sharing among DC sources and the absence of switching redundancies. On the other hand, multilevel dc-link (MLDCL) and switched series parallel sources (SSPS) RSC-MLI topologies are modular structures with adequate switching redundancies and can be an alternative to conventional cascaded H-bridge (CHB) for grid-connected photovoltaic (PV) systems. Therefore, in this paper, a comprehensive comparison among CHB, MLDCL and SSPS topologies has been carried out for grid connected PV application. Based on the outcome, an asymmetric 11 kV three-phase 11-level SSPS RSC-MLI is chosen. In this combination, a common non-linear sliding mode controller (SMC) is developed for generating maximum PV power from asymmetric single-stage PV sources by linearizing the non-linear PV system using an effective feedback linearization scheme. The PV power extracted is delivered to the grid by controlling SSPS RSC-MLI using another SMC. The performance of the system under wide variations of insolation levels is verified in MATLAB and further validated in hardware-in-the-loop OPAL-RT controller.