Hardware in loop solar panel simulator for two axis stabilized pico-satellite

Swayam cube satellite hosts a passive magnetic attitude control system (PMACS), achieving two axis stabilization and allowing the satellite to rotate about its antenna axis. As a result, power generated by the body mounted solar panels is variable and unregulated. Estimating the power budget and solar panel output for cube satellites which are passively stabilized is challenging. The solar panel output depends on its voltage current characteristics as well as orbit dependent parameters like incident solar flux and angle made by each satellite face with the solar rays. This paper describes the hardware in loop system and algorithm to emulate the solar panel behaviour for a two axis passively stabilized satellite. The satellite motion in the sun synchronous polar orbit has been modelled using the two line elements and SGP4 model, which were used to calculate satellite to sun vector and consequently the angles made by every face with this vector. Using the values of the derived angles, a voltage mode controlled DC-DC converter and a current limiting switch were used to obtain the required operating point on the characteristics of the panels. A real time control was implemented using an 8-bit microcontroller. Microcontroller has been interfaced with PC where calculations are being performed. A graphical user interface has been developed for data entry and real time display of operating point on V-I curve.