PV array voltage range extension for photovoltaic inverters using a mini-boost

Abstract

Photovoltaic (PV) plants are designed at higher voltage and lower current operation in order to reduce the overall system installation cost. Multiple PV modules connected in series are prone to shading problems which leads to loss of energy harvested. PV inverters without a boost stage are more efficient, by removing the additional power stage, but are prone to energy harvesting loss when the array is partially shaded and the voltage drops below the minimum operating voltage. Instead, PV inverters equipped with a boost stage improve the range of conditions where energy can be harvested but add additional losses to the system reducing the efficiency. In this paper, a new converter power stage topology design and methodology optimization is proposed in the form of a mini-boost, a cost-effective and attractive solution to the traditional approach. The mini-boost extends the DC voltage range for energy harvesting under shading conditions and low irradiance conditions and only needs to process a fraction of the power leading to a cost effective and attractive solution. A comparative analysis under different irradiance levels is presented to illustrate the advantages in energy harvesting obtained with the mini-boost solution. Simulations and experimental results using a dual mini-boost dc-dc stage and 3-phase 3-level neutral point clamped inverter level are presented to validate the proposed dc-bus extension range for energy harvesting.

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