Alternating multi-stage maximum power point tracking controlled parallelled photovoltaic systems for 'solar cooker'

摘要

In this paper we propose the control of a parallel multi-stage photovoltaic (PV) system using a reliable and precise Maximum Power Point Tracking (MPPT) control strategy. This technique is based on the acquisition of the electrical output quantities (voltage, current, and power), common to DC/DC converters, and the control of the power switches, in alternation. In the case of two stages, during the time t(i), converter 1 is regulated in real time by the MPPT control, and the second converter keeps the previous MPPT optimization parameters (t(i - 1)). During the following time t(i + 1), converter 1 retains the previous MPPT optimization parameters (t(i)) and converter 2 is regulated in real time by the MPPT controller. The proposed technique is experimented on a photovoltaic system that feeds a solar cooker. This system is formed by a thermal resistance, two types of PV panels (200 and 230 W) and two DC/DC converters. Compared to the classical technique (instantaneous control), the results obtained show a significant performance and improvements: Convergence speed towards the maximum power point PPM of 48%, variations the electrical quantities gaps (current, voltage, power) at the input and output of the DC/DC converters by a factor of 2.46, electrical energy production of 4%, plate heating temperature of 27.3%, and an efficiency of 5%. The temperatures of the thermal resistances are validated by the thermal models established during this work. The improvements in DC/DC converter performance and solar cooker heating temperature are attributed, on the one hand, to the nature of the proposed MPPT control, which reduces the dispersion of electrical quantities at the input and output of the DC/DC converters, and, on the other hand, to the rapid heating of the solar cooker by the electrical energy produced by the photovoltaic panels.