Today's solar arrays (SA) are limited to a few hundred volts, with 100 V being the standard bus voltage for high power (up to a few tens of kW) telecom satellites. Obviously, this voltage is not practical for solar power satellites (SPS), which are planned for MW or GW, but it is also questioned for actual electric propulsion (EP) systems and other electrical loads. Increasing the voltage of the solar array and employing voltage step-up power converters seems mandatory to obtain a higher bus voltage. Nowadays, SA voltages up to 300V-400V are reported for EP direct drive applications [1], but these voltages seem even too low for SPS, which probably requires a bus voltage from 5x to 25x times higher [2]. Focusing on power conversion techniques, recent trends in terrestrial high voltage photovoltaic power conversion [3] are a good starting point for considering options for SPS. This is also motivated by the use of modern wide-bandgap power devices that greatly increase their blocking voltage capabilities [4]. As a baseline proposal, a Sequential Zero-Voltage Zero-Current Current-Fed Isolated Converter is proposed. This proposal comes from two well-known techniques a) Sequential Switching Shunt Regulator (S3R) [5] and b) ZVZC resonant converter [6]. An unregulated resonant converter (push-pull, half-bridge, full-bridge…) is used as DC transformer to step-up the voltage of each solar array section with very high efficiency. At the secondary side of the converter, each individual converter (or several converters connected in series to further increase the voltage) are connected in parallel to the main bus, which requires a high voltage capacitance as the main filter. A main error amplifier (MEA) sequentially connects the number of SA sections needed to maintain bus voltage regulation. An adjustable bus voltage reference also allows the SA power modulation [7] to control the amount of power to be injected into the bus.
