Design of Solar Photovoltaic System for Domestic Applications

This paper deals with design and benefits of twointerleaved bidirectional phase-shift (TI-BPS) based buck-boost dc to dc converter in terms of fast load transient response, half output overall ripple current and half current stress on switches is to maintain dc bus voltage for an inverter during unavailability of grid. While grid is available, it charges battery energy storage (BES). With addition of a 5 kVA off-grid solar home inverter system, this architecture eliminates line-frequency transformer, and improves overall system performance like, light weight, efficient, comparatively higher power density. During absence of grid, a H-bridge dc-ac inverter directly feeds ac power to domestic loads. While grid is available, it also works as pulse width modulated (PWM) bridge-less ac-dc front end converter, which maintains dc-bus voltage at nominal as input for battery side TIBPS dc-dc converter. Another, two-interleaved phase-shift (TIPS) buck dc-dc converter is also incorporated to extract maximum power from PV array, which inherently makes PV array nominal maximum power point voltage (Vmpp) two times more than BES voltage level and current lower than half to reduce PV array wiring losses and cost. TI-PS dc-dc converter doubles ripple frequency than switching frequency and each inductor runs at maximum of half rated output current, which helps to use smaller and lighter LC and EMI/EMC noise filter, reduced by half current stress in both switching devices per switching cycle, and faster load transient regulation. Performance of proposed system is evaluated at reduced number of batteries from conventional 20 to 15 numbers of 12V batteries in series as BES, connected with 5 kW solar panel with open circuit voltage of 450Voc each, for maximum ripple suppression factor upto -80db at 50% duty cycle.