Large Signal Stability Analysis of the Solar Array Power System Using the Controlled Load Characteristic

Abstract

A large signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a Low-Earth-Orbit satellite power system. The effective load characteristics of every controllable method in the solar array regulator system, such as the constant power load, variable power load, constant voltage load, constant current load, and constant resistive load, are classified to analyze the large signal stability. Then, using the state plane analysis technique, the large signal behavior of the solar array system is portrayed and the stability of various equilibrium points is analyzed. Thus, this approach can be contributed to organize the optimal controller structure of the system by representing the relationship between the control method of the solar array regulator and the large signal stability. For the verification of the proposed large signal analysis, a solar array regulator system consisting of two 100W parallel module buck converters has been built and tested using a real 200W solar array. Nomenclature L Z = effective load characteristic L i = inductor current C v = capacitor voltage sa r = incremental resistance (tangential slope) of the solar array’s output curve sar r = incremental resistance (tangential slope) of the load line L = inductance C = capacitance n S = changing inductor current slope e S = external ramp slope sar L I = average inductor current of the solar array regulator D = duty ratio s T = sampling period i R = current sensing gain cv v = control voltage of the peak inductor current reference sar V = voltage regulated by the solar array regulator sar I = current regulated by the solar array regulator sar R = resistance regulated by the solar array regulator