A Transformerless Power Conversion Unit for Grid Connected Solar PV System

For low voltage solar PV array, the conventional solar photovoltaic (PV) generation systems (GSs) employ low or high frequency transformers to match the voltage gain between AC mains and solar PV array. However, the utilization of transformers, causes significant increment in weight, size and losses in the system. Considering this, a transformerless solar PV power conversion unit (PCU), is presented in this work for residential roof-top applications. The presented PCU employs a two-stage power architecture with active bridge rectifier stage at front end and high gain DC-DC stage at back end. At back end, an extended gain boost (EGB) DC-DC converter is considered between low voltage solar PV array and high DC link voltage. The EGB DC-DC stage ensures desired voltage gain characteristics between solar PV array and inverters DC link, without the use of transformers. The voltage gain characteristic of presented EGB DC-DC converter is improved through switched capacitors to keep the overall weight of the PCU in check. Moreover, the input and output currents being continuous in nature, such feature is incorporated at the back-end stage of the presented PCU, to ensure effective maximum power point tracking at solar PV array, and reduced current ripples at DC link side. The low current ripples at DC link further reduce the size of DC link capacitor, and thus improve the reliability of overall system. Performance of presented transformerless solar PV PCU is analyzed through MATLAB Simulink modelling and relevant results are presented for performance justification.