Effect of solar cell capacitance and interface cable inductance on the shunt switch current transients in spacecraft power conditioning unit

Spacecraft Bus is regulated with switching shunt voltage regulator having photovoltaic cells as the primary source of power. This source switches between the bus loads and the shunt switch for fine control of spacecraft bus voltage. The solar cell capacitance along with inductance and resistance of the interface cable between solar cells and power conditioning unit, generates damped sinusoidal currents superimposed on the short circuit current of solar cell when shunted through switch. The peak currents of sinusoidal transients have to be considered in the selection of shunt switch in power conditioning unit. Solar Panel is a combination of series and parallel solar cells forming many strings. Hardware simulation by illuminating solar panel interfaced to a power condition unit with actual spacecraft cable length is a difficult approach. In view of this a scaled down version of solar panel (having single parallel) is illuminated with known interface cable length. This hardware simulation provides sufficient information to generate solar cell model to carry out software simulation and analyze current transients of shunt switch for the actual solar string rating.