Power Quality Improvement of Grid-Connected Photovoltaic Systems Using Trans-Z-Source Inverter Under Partial Shading Con
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RESEARCH PAPER
Power Quality Improvement of Grid-Connected Photovoltaic Systems Using Trans-Z-Source Inverter Under Partial Shading Condition Ali Moghassemi1
•
Mehdi Hosseini1 • Javad Olamaei1
Received: 16 December 2019 / Accepted: 6 April 2020 Ó Shiraz University 2020
Abstract Voltage-source inverter has been used widely in traditional photovoltaic systems which have limitations. To overcome, Z-source inverter has been introduced. In spite of all the features introduced in Z-source inverter, its configuration has been improved over the years, like trans-Z-source inverter which has added advantages compared to traditional inverters, namely buck–boost feature, lesser passive elements, and higher voltage boost gain. In this paper, photovoltaic arrays are connected to the grid via the trans-Z-source inverter with the aim of improving its power quality. Moreover, the shootthrough duty ratio is kept constant in the switching control method to add features like lower voltage stress (higher reliability), lower total harmonic distortion (lower maintenance cost), and higher voltage boost ratio. To evaluate the precision of the proposed system, the photovoltaic system is simulated on a standard grid and under partial shading condition which brings about voltage sag, and hence, a dynamic voltage restorer is used to mitigate voltage sag. Simulation results are presented to verify the validation of the proposed photovoltaic system in terms of voltage and current THD reducing 78.2% and 19.7%, respectively. Keywords PV system Trans-Z-source inverter THD Partial shading Voltage sag DVR
1 Introduction Over the years, renewable and sustainable energy systems have been revving up, photovoltaic (PV) systems in particular for their significant advantages. Zero emission, very low operation cost, and the possibility to be installed near to the end users are some of these advantages. Due to the variable nature of PV systems, it is imperative to take into account their qualities which usually measured in terms of the output voltage and power. In general, a dc–dc converter is required in PV systems for boosting the output voltage of a PV array. Then, a dc– & Javad Olamaei [email protected] Ali Moghassemi [email protected] Mehdi Hosseini [email protected] 1
Department of Electrical Engineering, South Tehran Branch, Islamic Azad University, Danesh Lane, Falamak Jonoubi St., Shahrak Gharb., Tehran 1467683394, Iran
ac inverter is needed to convert this boosted dc voltage into three-phase voltage via order to connect to either an ac load or the external network. In traditional PV systems, conventional inverters like voltage-source inverter (VSI) in most cases (Ebrahimi et al. 2020) or current-source inverter (CSI) in some cases have been applied. Yet almost since the idea of using VSI took root, its setbacks have been cropping up. To cite a few, the VSI is a step-down inverter and requires a boost converter, or switches of each leg cannot be triggered simultaneously. To eliminate these limitations, VSI and CSI
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