Journal of Electrical Engineering : Volume 18 / 2018 - Edition : 3

A Single-Phase T-Type Transformerless NPC- MLI for Grid-Connected PV Power System

Authors:
chokkalingam B
Domain:
power electronics in power grids (from mobile phones to smart power grids)
Abstract:
Transformerless (TL) inverter topologies have elicited extra special treatment in photovoltaic (PV) based power generation system as they provide high efficiency and low cost. Conversely, for the successful TL grid-tied PV inverters implementation, the shoot-through problem of bridge legs and leakage current should be considered prudent. Neutral point multilevel inverter (NP-MLI) topologies based transformerless (TL) are being immensely used in high-power medium voltage grid connected applications due to their better performance as compared to two-level voltage source inverter (VSI). Unfortunately, these topologies such as neutral point clamped-MLI (NPC-MLI), full-bridge inverter with dc bypass (FB-DCBP) suffer from the shoot-through problem on the bridge legs, which affect the reliability of the implementation. Literature confirms that the T-type Neutral point Multilevel inverter (TNP-MLI) rallies better performance compared to NPC-MLI, with its own clamping diode free circuit structure. Based on the aforesaid credits, a novel Transformerless TNP-MLI (TL-TNP-MLI) is offered to be an alternative which can be applied in the medium power low-voltage grid-tied PV systems. The proposed TL-TNP-MLI topology ensures no switching frequency common-mode voltage, leakage current, and shoot-through burden. This paper initially analyzes the switching states, commutations, and common-mode characteristic of TL-TNP-MLI and compares with other reported NP-MLI based on its PV tied grid conn
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