As satellite missions become increasingly diverse, the power capacity of satellites continues to increase. Accordingly, the weight and loss of the electrical power system of the satellite must be reduced. Thus, a high bus voltage is required for the electrical power system of the satellite. However, most high-power dc/dc converter topologies, such as half-bridge and full-bridge dc/dc converters have leg-structures, which violate the heritage design characteristics of the dc/dc converters for satellites. To solve these problems, a two-switch forward converter with an integrated buck converter is proposed in this article. By integrating the buck converter into the two-switch forward converter, one switch and one diode are eliminated in the proposed converter, and consequently, its cost, weight, and volume can be greatly reduced. Moreover, the zero-voltage switching of the low-side switch can be achieved. Therefore, the proposed converter achieves a high efficiency under the entire load condition compared with conventional converters. The effectiveness and feasibility of the proposed converter were verified with a prototype of 300–330 V input and 600 W (150 V/100 V) output.

With rapid developments in the satellite data services market, the demand for low Earth orbit (LEO) satellites is increasing. Advancements in designing lightweight satellites are essential to maximize profits from the mass production of LEO satellites in private companies. This paper proposes a new direct charging control suitable for electrical power systems for lightweight and highly reliable LEO satellites. Moreover, an analysis of the proposed solar array regulator (SAR) in terms of weight, efficiency, and reliability is presented. Additionally, the advantages of the proposed SAR in terms of lifespan and state of health (SOH) of Li-ion batteries are presented because the peak value of the battery charging current and the temperature changes during the battery charging operation are relatively small.

A fault-tolerant converter is widely used in high-reliability applications. To satisfy the high-reliability requirements, fault tolerance is an essential feature and can be achieved by redundant converters. However, a large number of redundant converters degrade the overall power density and cost. This paper proposes a novel fault-tolerant LLC converter, which can reduce the number of redundant converters. Its structure is based on the input-parallel, output-series two half-bridge LLC converters and a midpoint connection on the secondary side. The proposed converter can withstand double short-circuit faults (SCFs) by utilizing only two converters instead of three converters. The redundant converter is used to achieve a single fault-tolerant capability against an SCF. When a second SCF occurs in the switch, the proposed converter is reconfigured to regulate the output voltage without additional semiconductor components. By analyzing the proposed converter, it is demonstrated that the proposed converter achieves high power density and low cost without degradation of efficiency. In addition, it can be easily extended to have multiple fault-tolerant capabilities. Finally, the performance and feasibility of the proposed converter were confirmed with a 100 V/12 A 1200 W prototype.

Recently, as the satellite data service market has grown significantly, satellite demand has been rapidly increasing. Demand for geostationary satellites with weather observation, communication broadcasting, and GPS missions is also increasing. Completing the charging process of the Li-ion battery during the sun period is one of the main tasks of the electrical power system in geostationary satellites. In the case of the electrical power system of low Earth orbit satellites, the Li-ion battery is connected to the DC/DC converter output, and the charging process is completed through CV control. However, in the case of the regulated bus of the DET type, which is mainly used in the electrical power system of geostationary satellites, a Li-ion battery is connected to the input of the DC/DC converter. Therefore, a method other than the CV control of the DC/DC converter is required. This paper proposes a control algorithm for tapering charging of the Li-ion battery in the regulated bus of the DET type for Li-ion battery charge completion operation required by space-level design standards. In addition, the proposed control algorithm is verified through an experiment on a geostationary satellite’s ground electrical test platform. The experiment verified that it has a power conversion efficiency of 99.5% from the solar array to the battery. It has 21 tapering steps at the equinox and 17 tapering steps at the solstice.

The conventional Weinberg converter, owing to its high efficiency; continuous input and output current; and the soft switching of its switches and diodes, is essentially utilized in battery discharge regulators (BDR) – components that make up the overall electrical power system for geostationary satellites. However, this converter faces a crucial drawback in that the output current ripple is considerably high during the commutating operation of its output diodes. Consequently, the output root mean square (RMS) current and output voltage ripple are high. This may directly influence the lifetime and overall capacitance of the bus capacitors, ultimately affecting the longevity and size of the geostationary satellite. Therefore, reducing the BDR’s output current ripple is essential in designing a geostationary satellite’s electrical power system. As a result, this paper proposes an improved Weinberg converter to reduce the output current ripple and output voltage ripple. Specifically, the proposed converter not only has a lower output current and voltage ripples compared to the conventional converter but also reduces the magnetizing current offset of the coupled inductor. Furthermore, similar to the conventional converter, it is capable of soft switching operation of all switches and achieving high efficiency without the reverse recovery problem of diodes. Overall, the proposed converter is verified with experimental results from a 750 W-rated prototype.

With the growing complexity of satellite missions, research on electric propulsion (EP) systems is becoming more important due to their high energy efficiency and longer operational lifespans. In addition, as satellite bus voltages rise from 50 to 300–400 V to support high-power EP systems, the development of high-power and high-efficiency power systems has become essential. Among the various power processing units in EP systems, heater power converters play a crucial role in regulating temperature for propellant vaporization and plasma ignition processes. The half-bridge type topologies are generally considered to handle the high input bus voltage of the heater power system. However, the half-bridge LLC converter has drawbacks related to performance degradation under large temperature fluctuations and reduced efficiency under wide input voltage variations in space environments, and the asymmetrical half-bridge (AHB) converter suffers from insufficient zero-voltage switching (ZVS) energy under light load conditions, resulting in low efficiency. Therefore, this article proposes a frequency control scheme for the AHB converter to enhance efficiency under light load conditions in EP heater power applications. By decreasing the switching frequency under light load conditions, the proposed control scheme secures sufficient ZVS energy, resulting in high efficiency without requiring additional components or redesign of magnetic components. A prototype with the proposed control scheme is implemented to validate its effectiveness and feasibility under 250–400 V input and 12 V/20 A output specifications.