methods of generating electricity without CO2 emissions. One potential solution is the
deployment of space-based solar power (SBSP) platforms, which involves the use of large
solar array structures in orbit capable of generate electricity in the GW range and transmitting
it to a ground station connected to the electrical grid. In recent years, several nations
worldwide, including the United States of America, China, and Japan, have initiated
programmes to research and develop commercial SBSP systems. In Europe, the European
Space Agency (ESA) has promoted the SOLARIS initiative, which aims to establish the
feasibility, fundamental knowledge, and necessary technology for the development of an
orbital demonstrator.
To effectively and reliably distribute power from the solar array sections to the rest of
the platform, high voltage distribution buses of up to 20 kV are required. In conventional
direct energy transfer topologies, the solar array sections operate at the same voltage as the
distribution bus. However, such methods are not well suited to managing power in the GW
range. At present, the maximum solar arrays voltage is 120 V, due to the occurrence of
several effects in the space environment at high voltage, which significantly degrade the solar
cells. It is therefore necessary to have a power system capable of converting the low voltage
from the solar array section to the high voltage distribution bus.
Considering the context and the need for power management and distribution solutions
for high voltage platforms, the aim of this doctoral thesis is to propose and develop a novel
architecture for the voltage conversion and regulation of the solar array sections, based on
well established techniques in the space sector: the Sequential Switching Shunt Regulator
(S3R) and the Zero Voltage Zero Current Switching (ZVZC) Direct Current Transformer
(DCX) converter.
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.
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References:
[1] J. B. de Boissieu, et. al. “High voltage electrical power system architecture optimized for electrical propulsion and high power payload,” ESA European Space Power Conference, ESPC 2019, pp. 1-7.
[2] J. O. McSpadden, J. C. Mankins, “Space Solar Power Programs and Microwave Wireless Power Transmission Technology,” IEEE Microwave magazine, Dec. 2002, pp. 46-57
[3] Md. Rabiul Islam, A. M. Mahfuz-Ur-Rahman, K. M. Muttaqi, D. Sutanto, “State-of-the-Art of the Medium- Voltage Power Converter Technologies for grid Integration of Solar Photovoltaic Power Plants,” IEEE Transactions on Energy Conversion, Vol. 34, No. 1, March 2019, pp. 372-384.
[4] J. Millán, P. Godignon, X. Perpiña, A. Perez-Tomás, J. Rebollo, “ A survey of Wide Bandgap Power Devices,” IEEE Transactions on Power Electronics, Vol. 29, No. 5, May 2014, pp. 2155-2163
[5] D. O’Sullivan, A. Weinberg, “The sequential shunt switching regulator (S3R),” ESTEC Spacecraft Power Conditioning Seminar, pp. 123-131, 1977.
[6] A. H. Weinberg, L. Ghislanzoni, “A new zero voltage and zero current power switching technique,” IEEE Transactions on Power Electronics, vol. 7, No. 4, pp. 655-665, Oct. 1992
[7] A. H. Weinberg, S. H. Weinberg, “A new maximum power point tracker topology,” ESA European Space Power Conference, 2002, pp. 1-6.
[8] R. Ramasamy, D. van Paridon, L. Summerer,” Solar Power Satellites for Lunar Rover Exploration”, In Proc. 68th International Astronautical Congress, Bremen, Germany, 2018
[9] M. Zerta, V. Blandow, P. Collins, J. Guillet, T. Nordmann, P. Schmidt, W. Weindorf, and W. Zittel, “Earth & Space-Based Power Generation Systems-A Comparison Study”. In Solar Power from Space-SPS'04, Vol. 567, p. 29, 2004
[10] L. Summerer, F. Ongaro, “Solar Power from Space-Validation of Options for Europe”. In Solar Power from Space-SPS'04 , Vol. 567, p. 17, 2004
[11] L. Summerer, O. Purcell, “Concepts for wireless energy transmission via laser”, In Proc. 1st International Conference On Space Optical Systems and Applications, ICSOS, 2009
[12] S. Sasaki, K. Tanaka, “Wireless power transmission technologies for solar power satellite,” IEEE MTT-S International Microwave Workshop Series on Innovative Wireless Power Transmission: Technologies, Systems, and Applications, 2011
[13] S. Lu, K. Sun, G. Cao, Y. Li, J. I. Ha, G.H. Min, “A high step-up modular isolated DC-DC converter for large capacity photovoltaic generation system integrated into MVDC grids,” 10th International Conference on Power Electronics – ECCE Asia, 2019.
[14] Y. Zhuang, F. Liu, Y. Huang, Z. Liu, S. Pan, X. Zha, J. Jiang, “A multiport modular DC-DC converter with low series LC power balancing unit for MVDC interface of distributed photovoltaics,” IEEE Transactions on Power Electronics, Early Access Article, 2020
[15] G. Ning, W. Chen, L. Shu, J. Zhao, W. Cao, J. Mei, C. Liu, “Hybrid resonant ZVZCs PWM full bridge converter for large photovoltaic parks connecting to MVDC grids,” IEEE Journal of Emerging and Selected topics in power electronics, vol. 5, No. 3, pp. 1078-1090, Sept, 2017
