Abstract:
This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic
energy systems where the solar irradiation changes during the day
time causing current and voltage changes. Varying the solar irradiation causes
output chopper voltage changes in order to keep working at maximum extracted
solar power. The chopper voltage changes leading to variable duty
cycle operation of chopper switch and causes a significant change in switch
losses in terms of the dissipated power. In addition to that the chopper behaviors
are studied when the chopper voltage is boosting up to a predetermined
reference value leading to a significant change in chopper current, voltage,
duty cycle and occurred losses. A mathematical model for chopper performances
and switch losses is derived, and a simulation model using Matlab/
Simulink platforms is conducted to follow the chopper behaviors. Simulation
results for concreteSUNPOWER panel type SPR-315E-WHT-D with 315
Watts peak indicates that during the daylight time transistors are exposed to
complicated changes in their current, voltage and dissipated power. Furthermore
changing the output voltage according to load requirements causes
heavy stress on the transistor in terms of current, oscillations and losses as
well. Simulation results show that there are optimized values of irradiation,
chopper voltage and duty cycle where the transistor losses are minimized. In
addition to that, projecting the transistor losses over the daylight time at a
given irradiation rate shows how these losses vary among the year, and the
amount of energy dissipated across the main chopper switch which is around
2970 Whr/yr for the present case. Furthermore, the conducted simulation also
shows the occurred in the transistor behaviors when solar irradiation
changes, and can be serving for further studies.
