A New Transformer-Less Five-Level Grid-Tied Inverter for Photovoltaic Applications

• Published in: IEEE transactions on energy conversion Vol. 35; no. 1; pp. 106 - 118
• Main Authors: Vosoughi, Naser, Hosseini, Seyed Hossein, Sabahi, Mehran
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Active control; Capacitors; Energy sources; Grid connected multilevel inverter; Inductors; Inverters; Leakage current; leakage current elimination; Leakage currents; Multilevel; Phase transformers; Phase transitions; switched-capacitor based structure; Switches; Topology; transformer-less inverter; Transformers; Waveforms
• ISSN: 0885-8969; 1558-0059
• DOI: 10.1109/TEC.2019.2940539

A new fundamental structure of a single-phase transformer-less grid connected multilevel inverter based on a switched-capacitor structure is presented in this study. By employing the series-parallel switching conversion of the integrated switched-capacitor module in a packed unit, attractive features for the proposed inverter can be obtained such as high efficiency and boosting ability within a single stage operation. Also, using a common grounding technique provides an additional advantage of reducing the leakage current. Moreover, the presented structure generates a multilevel waveform at the output voltage terminals which reduces the harmonics in the system. A peak current controller is utilized for triggering the gate of the power switches and controlling both the active and reactive powers. This results in a tightly controlled current with an appropriate quality that can be injected to the grid using a single source renewable energy resource. Operating procedures, design considerations, comparison studies and test results of a 620 W prototype are also presented to validate the accuracy and feasibility of the proposed multilevel inverter.