Received: 8 August 2017 Revised: 24 October 2017 Accepted: 9 December 2017 DOI: 10.1002/cta.2448 RESEARCH ARTICLE FPGA-based implementation for improved control scheme of grid-connected PV system with 3-phase 3-level NPC-VSI Satabdy Jena 1 Gayadhar Panda 2 Rangababu Peesapati 3 1 Department of Electrical Engineering, Indian Institute of Technology Delhi, New Delhi, Delhi 110016 India 2 Department of Electrical Engineering, National Institute of Technology Meghalaya, Shillong 793003, India 3 Department of Electronics and Communication Engineering, National Institute of Technology Meghalaya, Shillong, 793003 India Correspondence Rangababu Peesapati, Department of Electronics and Communication Engineering, National Institute of Technology Meghalaya, Shillong 793003, India. Email: p.rangababu@nitm.ac.in Summary The large scale penetration of renewable energy resources has boosted the need of using improved control technique and modular power electronic con- verter structures for efficient and reliable operation of grid-connected systems. This study investigates the performance of a grid-connected 3-phase 3-level neutral-point clamped voltage source inverter for renewable energy integration by using improved current control technique. For medium or high-voltage grid interfacing, the multilevel inverter structure is generally used to reduce the voltage stress across the switching device as well as the harmonic distortion. The neutral-point clamped voltage source inverter is controlled by using decou- pling technique along with the proper grid synchronization via moving average filter–based phase-locked loop. The moving average filter–based phase-locked loop is used to reduce the delay in grid angle estimation under balanced as well as distorted grid conditions. A Lyapunov-based approach for analysing the sta- bility of the system has also been discussed. In this study, the hardware-in-loop (HIL) simulation of the control algorithm and the grid synchronization tech- nique is realized using Virtex-6 FPGA ML605 evaluation kit. The performance of the system is analyzed by conducting a time-domain simulation in the Mat- lab/Simulink platform and its performance is examined in the HIL environment. The simulation and the hardware cosimulation results are presented to validate the effectiveness of the proposed control scheme. KEYWORDS field programmable gate array (FPGA), moving average filter (MAF), photovoltaic (PV), phase-locked loop (PLL), two-degree-of-freedom (2DoF) 1 INTRODUCTION Renewable energy sources are evolving as promising alternatives due to increasing global environment issues, rising prices of conventional resources, and their exhaustible reserves. 1 Harnessing electrical energy with the aid of photovoltaic (PV) systems has garnered more attention due to its abundance in availability and ease of access across the globe. 2,3 The currently used configurations for PV systems are of stand-alone/grid-connected and single-stage/2-stage. 4 How- ever, the implications of increased grid integration of PV systems are manifold and calls forth the application of suitable control and protection strategies and power converter configurations to meet the interconnection standards, improve effi- ciency, and enhance power quality. To cater to the needs, grid-interfaced inverters adapt the VSI topology with a current Int J Circ Theor Appl. 2018;1–23. wileyonlinelibrary.com/journal/cta Copyright © 2018 John Wiley & Sons, Ltd. 1