SWITCHED CAPACITOR DC-DC CONVERTER BASED MAXIMUM POWER POINT TRACKING OF A PV SOURCE FOR NANO SATELLITE APPLICATION

The power yield of a PV array depends on solar radiation and temperature. Maximum power point (MPP) tracking techniques are employed to maximize the output power of a PV source. The solar panel is the primary power source of a nano satellite. To optimize the panel design, an electrical MPP tracking scheme is very vital to extract maximum power from the panel at all instances. MPP tracking schemes known thus far employ conventional DC-DC power converters using inductors which hinder miniaturization. This paper demonstrates the use of a buck type Switched Capacitor (SC) dc-dc converter for MPP tracking for an 8Kg remote sensing nano satellite. Since SC converters do not use inductors, they have a large power density and are amenable to miniaturization. A novel method of MPP tracking is presented which involves the measurement of the panel voltage, panel temperature and computing the sun incidence angle with the knowledge of the space craft position. The closed loop control of the fixed frequency SC converter is achieved by pulse-width modulating the gate drive of the MOSFET switches of the MPP tracking SC converter. The weight of the entire power system is approximately 750 grams.