Maximum Power Tracking and Pulse-Width-Modulated Shunt for Satellite Power Systems

Abstract

The feasibility is evaluated of using the continuous maximum power operation to lower the operating temperature and to achieve the highest efficiency for solar cells deployed in space, which are subject to thermally induced efficiency degradations and partial failure of cells due to microextraterrestrial objects’ impinging or mechanical stress during deployment. The solar array is constantly operated at its maximum power point through a maximum power point tracker, delivering power to the load, the battery, and the shunt that is controlled by a pulse-width modulator to facilitate the tracker with variable impedance, so that the conditions for a maximum power transfer can always be satisfied regardless of the variation in the array internal resistance. It is shown that the proposed design can achieve the best efficiency and the lowest operating temperature compared to conventional regulation methods. The design also results in minimized bus voltage ripples and increased voltage regulation capabilities. Nomenclature A = solar array front surface area, m 2 An = normalized solar array area c p = solar array specific heat, J/kg · K D = percentage of sunshine time in one orbit HST = satellite altitude, m m = structured solar array mass, kg ma = solar array specific mass, kg/m 2 mn = normalized specific mass, kg/m 2