Convegni ATI - Accesso riservato soci CTI

Autore: P. Bauer, G. Spagnuolo, J. Bokor

Collana: CA - 62 - Fisciano 2007

Note:
In this paper, at first the existence and the number of MPPs for a single panel and for an n string of series connected panels are examined. In particular, it is demonstrated that an n string of PV panels can have n or less local MPPs, and it can not have more than n local MPPs. However, the goal of PV array control is to track the global MPP (get the maximum possible power from the field). So the effective selection and tracking of global MPP is essential. In the second part of the paper a fast and adaptive algorithm is introduced which tracks the global MPP of a photovoltaic array realized by series connected panels. The proposed solution is a supervised hill climbing method. The supervisor makes the system adaptive, with observation of sudden current changes and the use of a timer. Simulation tests (for a string of two panels) were
performed with and without noise, and temperature effects were also examined. The
efficiency of control was near and above 90%. Hopefully the efficiency will be the same
for more than two panels also (tests will be done only in the future). So, the solution
performs well, but the efficiency strongly depends on the timing of the supervisor. This
needs the measurement of ‘time periods’ in sun irradiation changes which can be solved
‘off line’ by the use of a pyranometer.