Thermal stress reduced maximum power point tracking for two stages photovoltaic converters

Several maximum power point tracking (MPPT) methods have been proposed to optimize the energy harvesting of photovoltaic systems. However, the optimization of the energy harvesting can produce extremely variable loading of the power semiconductors resulting in a decrease of the system lifetime. This work proposes a multi-objective MPPT for two-stage photovoltaic converters, where the semiconductor thermal stress is taken into account while searching for the maximum power point. A perturb and observe based algorithm which limits the positive temperature gradient and the maximum junction temperature of the power semiconductors of the boost converter is introduced and fully validated in the laboratory with a mission profile emulating variable irradiance conditions. The achievable lifetime improvement is evaluated against the reduction in the energy harvesting.