Performance Evaluation of the Universal Photovoltaic String Converter During the Operation in DC Microgrid Environment

Photovoltaic (PV) string converter for residential dc microgrids is presented. The concept of the converter is based on the interleaved buck-boost dc-dc converter with a wide input voltage range operation capability. The main control unit is a continuous control set model predictive control. The control system uses a simple droop control unit based on a proportional-integral regulator to ensure stability of the grid voltage. An experimental prototype based on a universal solar dc-dc/ac converter with the unfolding circuit was designed, featuring the MPPT voltage window from 150 V to 490 V and the nominal power of 3.6 kW. The efficiency benchmarking of a universal solar dc-dc/ac with connection to the dc microgrid is considered. Three real-world PV string profiles were considered during the experimental verification of the proposed approach. Based on the California Energy Commission (CEC) standard, the efficiency of the approach was well over 97 % in all selected case study scenarios.