International Journal of Power Electronics and Drive System (IJPEDS) Vol. 10, No. 4, December 2019, pp. 2013~2020 ISSN: 2088-8694, DOI: 10.11591/ijpeds.v10.i4.pp2013-2020  2013 Journal homepage: http://iaescore.com/journals/index.php/IJPEDS Grid tied PV system using modular multilevel inverter Sujitha N., Partha Sarathi Subudhi, Krithiga S., S. Angalaeswari, T. Deepa, D.Subbulekshmi School of Electrical Engineering, Vellore Institute of Technology, India Article Info ABSTRACT Article history: Received Mar 12, 2019 Revised Apr 20, 2019 Accepted Jun 4, 2019 A grid tied photovoltaic system using modular multilevel inverter topology is proposed in this paper. Basic unit structure of modular multilevel inverter used in this system is capable of converting DC power from PV array to AC power for feeding power to the household loads or utility grid. The proposed modular multilevel inverter structure has lesser power electronic devices compared to the existing multilevel inverter topologies. The proposed system generates a nearly sinusoidal signal and achieves better output profile with low total harmonic distortion. Simulation of the proposed system is carried out in MATLAB/Simulink software and the results are presented. Keywords: Photovoltaic Array Modular Multilevel Inverter Utility grid Total Harmonic Distortion Copyright © 2019 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Krithiga S., School of Electrical Engineering, Vellore Institute of Technology, Chennai, Vandalur-Kelambakkam Road, Chennai-600127, Tamil Nadu, India. Email: s_krithiga@yahoo.com 1. INTRODUCTION Photovoltaic (PV) systems are booming in the renewable energy market due to its clean and abundantly available nature [1, 2]. Also, solar energy is easily tapped and converted into electricity which is the added advantage of PV array over other renewable energy sources [3]. Due to the intermittent nature of the PV array, power electronic interface is needed in the standalone and grid tied PV systems for obtaining the desired output [4]. For grid tied PV system, power electronic inverters are utilized as the interface to convert the generated dc power from the PV array into ac power to feed the utility grid [5-9]. Basic inverter generates a squarewave output which is considered to have higher harmonic content. Thus, large size filter has to be employed to obtain pure sinusoidal waveform inorder to feed the PV generated power to the grid. Also, this inverter has high dv/dt stress and harmonic distortion in the output waveform. To overcome these problems, multilevel inverters were developed. Multilevel inverter (MLI) is popular among industrial and research sectors due to its advantages like improved output voltage profile with low dv/dt and low common mode voltages [10, 11]. The output voltage of MLI has low distortion and low harmonic content which reduces the size and cost of the filter and the level of electromagnetic interference (EMI) [12]. The three basic MLI topologies are diode clamped MLI, flying capacitor MLI and cascaded MLI [13-15]. As the number of levels of output voltage increases, these topologies require increased number of switches, diodes and capacitors which eventually increases the cost, volume and control complexity [16-20]. To overcome these disadvantages, modular multilevel inverters (MMLI) are developed [21, 22] with two parts viz. level generator and polarity changer. Level generator creates unipolar multilevel output voltage waveforms using high frequency switches and polarity changer converts this unipolar waveform into a bipolar waveform using low frequency switches at line frequency. In this MMLI, the number of switches, conduction loss and switching loss are reduced compared to that of the conventional multilevel inverter for