An Improved Current Control Scheme for Reduced Switching Frequency in a Rooftop Grid-Interfaced PV System

This paper presents a novel modified unipolar-toggle hysteresis current control (UTHCC) strategy for a single-phase grid-connected photovoltaic (GCPV) rooftop system. The proposed UTHCC is designed to minimise the switching frequency and hence the switching losses in the GCPV rooftop system, thus improving its efficiency, without compromising the THD. In this work, the performance of the proposed scheme is compared with conventional HCC and unipolar-toggle (UT) modulation schemes. The comparison study is done through simulation and using a real-time platform, along with experimental validation of the same. The proposed UTHCC scheme was found to be capable of reducing the switching frequency by nearly 46% (theoretically) and by up to 32% through real-time and experimental validation, along with a reduction in switching losses, which is about 35% of that with conventional HCC. The proposed UTHCC scheme was also found to have 3.4% lower THD as compared to the UT modulation scheme. The proposed work is modelled in the MATLAB/Simulink platform and validated using the OPAL-RT 4510 real-time platform as well as an experimental setup.