A New Magnetic Linked Active Neutral Point Clamp Converter for Transformer-less Direct Grid Integration of Solar Photovoltaic Systems

The multilevel inverters are becoming increasingly popular for use in the grid integration of wind and photovoltaic (PV) power plants due to their higher voltage handling capability and the better output power quality. There are several types of multilevel inverters that have been proposed in the literature; among them the active neutral point clamp (ANPC) multilevel inverters have been drawing significant attention specially for reducing unequal loss distribution. However, with the increase of number of levels, the ANPC requires more electronic switches and flying capacitors, by which the complexity and the cost increases. In this paper, a reduced number of switch and flying capacitor ANPC inverter is presented for the grid integration of the solar PV systems. Moreover, the proposed power converter effectively utilizes the dc bus voltage compared with the traditional ANPC converter. In the proposed inverter, a high frequency transformer is used to eliminate the voltage balancing problems faced by the traditional ANPC inverters. The proposed magnetic linked power converter provides the galvanic isolation, which is one of the most critical issues for traditional transformer-less grid connected PV systems. The proposed topology makes the control strategy simple and makes the power conversion system reliable for the photovoltaic power plants.