Single phase grid connected multilevel inverter for isolated and unbalanced PV sources

Abdi, S.M. and Ghedamsi, K. and Mekhilef, Saad (2016) Single phase grid connected multilevel inverter for isolated and unbalanced PV sources. EEA - Electrotehnica, Electronica, Automatica, 64 (3). pp. 20-27. ISSN 1582-5175,

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Large scale photovoltaic fields are favoured for their low cost-per-watt, but exposed to partial shading and other mismatches where the decentralized Maximum Power Point Tracking (MPPT) is recommended. For a grid connection, an inverter is required, but the decentralized inverter solution is expensive and produces poor current Total Harmonic Distortion (THD). Central three level inverter is lower cost but power limited and has also a poor current THD. We propose a decentralized MPPT boost converter based, followed by a central non-uniform multilevel inverter. The PV-generators are the separated DC sources; however they are unbalanced due to unexpectedly variations of lighting, temperature and system faults. The idea here is to limit the power in each level when dimensioning, respecting the Safety Operation Area of the used semiconductors. So, the voltage amplitude of each level depends on the corresponding PV-group and the entire power where a non-uniform multilevel wave can be obtained. The grid current is controlled by a hysteresis relay for power transfer, where an external current and internal voltage control loops are used based on a simple PI regulator. In many Grid-PV systems, the transferred power reference is generated by PV power measurement requiring numerous long wires to the control-unit. Here, the voltage and current references (transferred power) are generated via DC-link voltages feedback. Simulation results show an active power transfer to the grid with a very low current THD even under a hard-unbalanced PV conditions.

Item Type: Article
Uncontrolled Keywords: Grid connected PV; Multilevel inverter; Unbalanced PV-generators; Large scale PV fields; Renewable energy
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Faculty of Engineering
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 11 Oct 2017 06:50
Last Modified: 25 Oct 2019 05:35

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