A Battery-Less Photovoltaic Water-Pumping System With Low Decoupling Capacitance

A two-stage photovoltaic water-pumping system architecture is presented in this paper. In contrast with other alternatives available in the literature, the electronic drive does not exploit batteries to accomplish energy decoupling, neither large electrolytic capacitors in between stages. Although these two design decisions, respectively, minimize environmental impacts and increase the converter's expected lifetime, they also bring about considerable control difficulties. More specifically, the dc-link stiffness is reduced, and thus, large voltage oscillations may occur. In order to overcome this problem, a nonlinear controller interconnection between the individual compensator of each stage is created to account for the low capacitance. Simulations and experimental results demonstrate the effectiveness of the method in stabilizing the dc-link voltage under sudden solar irradiation changes. The final converter was deployed in a remote rural community in Guinea-Bissau for crop irrigation purposes. Despite the harsh conditions such as high temperatures and sea breeze, in situ results were satisfactory and validated the system robustness.