High-Power Modular Power Conditioning and Distribution Unit for an Integrated Microsatellite Avionics Stack

Brazil has participated, over the years, in the development of remote sensing satellites, for imaging purposes, known as CBERS (China-Brazil earth resource satellite). With a polar orbit of 778 km of altitude, it takes around one hundred minutes to complete a revolution around the Earth, with an eclipse of about half an hour, resulting from the passage of the satellite through the Earth's shadow. Designed for a 3 years mission period, its power conditioning and distribution unit shall be able to provide, with high reliability, 1820W of continuous power to the spacecraft in a harsh environment of radiation-induced damaged on electronic components, large temperature variations in orbit and extreme vibrations during launch phase.

In addition to the performance, power consumption has become a major concern in High Performance Computing (HPC) systems. Typically the cooling system and the IT loads are the major contributors to the power bills. Understanding the power consumption at different granular levels in the HPC system is a first step to quantify the problems in HPC system. By proper monitoring and effective utilization of the cooling system, the power requirements of the HPC facility can be effectively met. In this paper we present a system where node level power measurement and WSN based rack level temperature measurement are used to provide localized control of cold air supply. A Smart Power Monitoring and Distribution Unit (PMDU) is designed and developed, to replace the existing Power Distribution Unit (PDU) in HPC. This can measure and report the power consumption, to support power profiling of large scale HPC system. This measured data are communicated to a base station via Ethernet. This base station collects all such measurements which can be used for power profiling of IT load of the HPC system. This helps to provide better insight into the power utilization pattern. Wireless Sensor Network (WSN) is used to collect exhaust and inlet air temperature of the server nodes and this information is used for directing the cold air effectively. A vent control system is designed and fabricated for intelligently directing the air flow to the server node inlet. It takes the node power and the temperature data as its inputs. This enables supplying/ redirecting more cold air towards under-cooled nodes without creating an extra load on the cooling system, thereby bringing in effective cooling at reduced power consumption. As an added advantage this could help in hot-spots mitigation.

Satellite Power subsystem is one of the critical subsystems of satellite. The purpose of power subsystem is to generate, store and distribute the conditioned power to all subsystems. This paper focuses on modular design methodology of COTS based small Satellite Power System (SPS). SPS has five main parts Power generation Unit (PGU), Battery Unit (BTU), Power Control Unit (PCU), Power conditioning Unit (PCNU) and Power Distribution Unit (PDU). According to the mission requirements centralized, fully regulated bus architecture is developed using modular approach. The SPS is scalable starting from 200 watt to 1000 watt. It is aimed for experimental LEO mission. The duration of the mission is one year.

\nThe assessment of an in-flight battery health status is of great interest. However, it is very difficult to perform with sufficient accuracy because the battery is constantly operated and no full discharge during a space mission can be done. Currently, a method for performing a health assessment is via the correlation of battery capacity with internal resistance, which can be more easily measured. Another method is to fit the on board battery voltage using the telemetry of current and temperature as inputs by advanced modelling techniques and to derive the ageing parameters of the battery. This is done by optimising the parameters so that the fitted voltage curve is as close as possible to the actual measured voltage telemetry curve. Then an assessment of the battery capacity and energy can be done by simulating a battery discharge at the desired conditions with the required voltage limits. However, these two methods often require extensive battery life tests on ground to estimate the ageing behaviour for a particular mission.\nIn this paper a novel health assessment system is proposed by which a more straight forward and accurate assessment of the battery health in terms of capacity and energy can be performed. The proposed system consists to use one or some battery string(s), which can be safely disconnected via the PCDU (Power Conditioning and Distribution Unit) from the battery for a dedicated capacity measurement while the main part of the battery continues to operate normally. In this paper, the viability of the proposed system is demonstrated and the implications on the battery and the power system are discussed.\n

With the development of modern small satellite technology, short development cycles, low cost, and high reliability have become trends in the era of New Space. To achieve the above goals, an integrated centralized architecture of onboard avionics for an internet of things CubeSat was proposed, and CAN, I2C, and 1-wire buses were employed for telemetry collection and command sending. The implementation of onboard computers (OBCs) and the power conditioning and distribution unit (PCDU) was introduced based on the PC104 industrial standards. An arbitration switching strategy between the primary and backup OBCs was proposed so that the primary OBC had priority to be on duty. Over 98% of commercial off-the-shelf (COTS) parts were used to decrease costs, so a procedure for COTS part selection and a qualified method were presented for reliable application. The onboard avionics, including OBC and PCDU, were developed in six months, and the satellite has been in orbit for more than three years and still works well. The reliability of the onboard avionics developed using the philosophy of New Space is demonstrated by the three-year flight in orbit.

Electric two-wheelers have a Low voltage Power Distribution Unit (PDU) which caters to peripheral loads that operate on the lower voltage platform. PDU works at high efficiency at medium to high loads and low efficiency at low loads. In parked mode of the vehicle, the peripheral loads are very low during which the PDU operates inefficiently for long periods of time. At high load, the conduction loss is higher, at low load, the gate driving loss and switching loss dominate due to the relatively small conduction loss. This paper presents a synchronous buck converter based high power PDU which is used with ultracapacitor (as secondary power unit) to improve the overall power unit's efficiency at low load demands. In the proposed topology, buck converter charges the ultra-capacitor and caters to high power loads leading to high efficiency while low load demand is catered to by ultracapacitor and buck converter is turned off, thus the overall efficiency of the system increases at both high and low power loads. Various matlab/simulink simulations are analyzed/presented to observe the same.

One of the more intriguing applications of wireless power transfer is power delivery for low-power Internet of Things (IoT) devices. By utilizing RF near-field coupling (NFC), an improved combination of small receiver coil area and system efficiency can be achieved, as is ideal for wireless charging for low-power IoT platforms. However, utilizing high efficiency RF NFC comes with a cost—various electromagnetic effects can lead to detuning of the resonant frequency if not properly modeled. In addition, integrating power regulation with high frequency ac–dc conversion can create large ripple voltage supply to a power distribution unit (PDU). This paper investigates the system level issues that arise in efficient, regulated RF NFC systems for milliwatt-scale output power. A method for modeling the various electromagnetic, frequency detuning effects is presented, as well as a selection process for the circuit component values in the design. Furthermore, a reverse power distribution network is designed to integrate the rectifier with a PDU, introducing a target impedance and phase considerations for an RF rectifier. The modeling and integration solutions are experimentally verified through two different RF NFC systems. The systems have measured peak efficiency of 68.4% at 3.3 V output and 58.6% for 1 V output with less than 100 mm $^2$ receiver coil area, demonstrating a unique combination of small coil area and high efficiency compared to other NFC systems to better support low-power IoT devices.

Power Distribution Unit (PDU) is a power supply unit that supplies various DC voltage levels for electric equipment. Reliability of PDU is very important in electrical systems. Buck converter is frequently used in PDU to provide the lower voltage levels than the source voltage level. The output capacitor of the buck converter is the main factor of failure. In this paper, we present a method to design a buck converter with almost no inductor current ripple. If the inductor current ripple is eliminated, the output capacitor can be removed from the converter. By removing the capacitor, the reliability and transient response of the converter can be improved considerably. The proposed method is based on interleaved buck converters. One of the advantages of interleaved converters is the low inductor current ripple. Theoretical analysis and simulation results are presented to justify the proposed idea.

This paper presents a "Medium Power" compact, light and low cost PCDU (Power Control and Distribution Unit) which has been designed as a modular and configurable equipment for Low Earth Orbit (LEO) missions with a maximum power capability of 1500 W. The PCDU supports a maximum of 4 independent power inputs (up to 75 V), and provides a 28 V unregulated power bus. Maximum Power Point Tracking (MPPT) is independently performed on each input; MPPT relies on buck regulators with direct drive capability, operating in `N+1' cold redundancy. The latter feature, together with the full cold redundancy of the Control Unit inside the PCDU, makes the device fully compliant with the Single Point of Failure free requirement. Moreover, the passive balancing managed by the PCDU guarantees the correct distribution of the cells charge, and contributes in improving the battery reliability. The unregulated bus is protected and distributed through nominal plus redundant LCL/RLCL and fuse protected lines for heaters and HDRMs. A cross-strapped architecture allows to control both nominal and redundant protected outputs from the nominal or redundant section of the unit, at the same time maximizing the PCDU availability. The PCDU, which is fully monitored, controlled and configured through the N+R CAN bus, can be easily tailored for various missions since its functionalities are segregated in different and specific stackable electronic boards (no backplane is used), and FPGAs are programmable. Finally, to balance the equipment radiation hardness and reliability figure versus costs, the PCDU has been designed with a mixed approach: COTS based supported by Sitael heritage [1] [2] and scheduled radiation tests, and the usage of MIL/Space qualified components for critical functions.

<div class="htmlview paragraph">The High Voltage Power Distribution Unit (PDU) is constructed of magnesium in support of Fuel Cell Electric Vehicle (FCEV) weight reduction efforts. The PDU distributes and controls a nominal 75 kilowatts of power generated by the Fuel Cell, the primary source of High Voltage power, to all the vehicle loads and accessories. The constraints imposed on the design of the PDU resulted in a component highly susceptible to general and galvanic corrosion. Corrosion abatement was the focus of the PDU redesign. This paper describes the redesign efforts undertaken by Ford personnel to improve the part robustness and corrosion resistance.</div>

This paper presents the studies made on the definition and design of a decentralized and modular electrical architecture of Power Conditioning Unit (PCU).The modular PCU is able to cover a large range of mission demands by adapting the number of power modules (PM) while the electrical interfaces remain the same.A decentralized architecture is proposed where each module is able to control the solar arrays and to manage the batteries. It appears that this kind of architecture becomes feasible thanks to digital circuits and using a communication bus [1].Breadboards are being tested in order to validate the concept.Reliability and robustness aspects are studied and a redundant architecture is tested.

The topology of the power conditioning unit (PCU) that is used with energy storage system (ESS), has a vital role especially in braking energy recovery. In recent studies, conventional bidirectional half-bridge topology is widely used as a PCU for ESSs. Due to its structure, it does not have the capability of capturing braking energy when the voltage across the motor terminals is lower than ESS voltage. This study investigates the feasibility of utilising a PCU with stepping up capability in regenerative braking operation mode, focusing on the additional braking energy that can be captured in comparison with that of the conventional half-bridge buck/boost converter. In order to verify the advantageous of the proposed approach in braking energy recovery, two 1 kW prototypes, a conventional half-bridge buck-boost and cascaded buck-boost converters are designed and tested for three different drive cycles including normalised version of ECE-15.

This paper presents a summary of an experimental research project to evaluate a single sided linear induction motor (SLIM) as an integrated suspension/ propulsion system (ISPS) for guided ground transportation vehicles. Experimental results for rotating wheel tests of a full size section of a SLIM are presented. Emphasis is given to an application in the speed range of 200 to 500 km/hr; however, an extension of the results to lower speeds can be realized with further study of the data acquired. The results indicate that feasibility in such an application is limited to the extent that the adjudged benefits of ISPS outweigh the cost of the required onboard power conditioning unit (PCU). The size of the PCU increases with speed, nominal airgap, and the guidance/lift ratio desired. Results are presented to define the maximum practical speed for application as a function of the state of the art of PCU technology.

The most important PV experimental station in Italy is the DELPHOS (Demonstration Electric Photovoltaic System) plant, built in the frame of the Delphos project. The first section (300 kW) of the plant has been running since December 1986, while a second 300 kW section is under construction. Experimental activities have been focused on electricity production in connection with the 3-phase transmission line at standard voltage of 20 kV. Both system and component performance have been analyzed. In particular, specific measurements have been carried out in order to study the power conditioning unit (PCU) and to evaluate the relevant efficiency and the maximum power point tracking capability, as well as the power factor correction operation and the harmonic filtering. After a short description of the principal characteristics of the PCU, a detailed performance analysis of main PCU components is presented and possible future system improvements are discussed.

Synchronization of AC sources is a challenging task due to the variation in voltage, frequency and jump in phase angle at the instant of mode transfer. Conventional SRF-PLL (Synchronous Reference Frame-Phase Locked Loop) fails to extract the frequency and phase at unbalanced and distorted voltages conditions. Therefore, a frequency adaptive filter (FAF) is used to estimate the phase angles of the voltages of the grid and the hydro generator, which are harmonics-free. The microgrid is found capable of driving in both islanded mode and grid connected mode. Moreover, this work also utilizes a block sparse normalized proportionate least mean M estimate based (BS-NPLME) adaptive filter to extract the fundamental element of the load currents and the hydro generator currents in both the modes to generate the switching pulses. Besides, to improve the reliability of the system, a battery energy storage (BES) is integrated to the microgrid (MG) along with solar PV panel to harness the solar energy. An increment conductance (InC) maximum power point algorithm (MPPA) is used to extract the peak power. Furthermore, the ancillary functions delivered by the power conditioning unit, are achieved as suppression of harmonics and power factor correction of the grid. The reactive power is compensated by power conditioning unit (PCU). This system is simulated in MATLAB platform and obtained results are presented to demonstrate these functions of MG.