Low Voltage Ride-Through Capability of a Novel Grid Connected Inverter Suitable for Transformer-Less Solar PV–Grid Interface

Abstract

In order to face the challenges due to the large-scale integration of photovoltaic (PV) inverters on the distribution side, the grid-connected PV inverters are expected to provide certain ancillary services. These ancillary services include reactive power support, low voltage ride through (LVRT), and harmonic compensation, just to name a few. In this article, the LVRT capability of a Cuk-derived novel inverter, 6sw-Cuk derived transformerless inverter (6sw-CDTI), suitable for transformer-less grid-PV interface, is explored. The transformer-less inverter, 6sw-CDTI, considered in this work can provide the desired ancillary services more efficiently and at a lesser cost as compared to the conventional inverters. Reactive power support to the grid can be provided without distorting the injected current by 6sw-CDTI with no dc injection due to symmetrical operation in both half cycles. Besides this, the leakage current elimination is not affected because the topological structure is not altered. Experimental results obtained from a 200-W laboratory prototype illustrate how additional control features can be integrated in the inverter control scheme for LVRT. Single-phase instantaneous p-q theory is used for inverter control, and a feed-forward component is added in the control scheme for improved dynamic response.