Tapping on HVDC lines using DC transformers

This paper presents a new topology for a high-efficiency dc/dc resonant power converter that utilizes a resistance compression network (RCN) to provide simultaneous zero-voltage switching and near-zero-current switching across a wide range of input voltage, output voltage, and power levels. The RCN maintains desired current waveforms over a wide range of voltage operating conditions. The use of ON/OFF control in conjunction with narrowband frequency control enables high efficiency to be maintained across a wide range of power levels. The converter implementation provides galvanic isolation and enables large (greater than 1:10) voltage conversion ratios, making the system suitable for large step-up conversion in applications such as distributed photovoltaic converters. Experimental results from a 200-W prototype operating at 500 kHz show that over 95% efficiency is maintained across an input voltage range of 25-40 V with an output voltage of 400 V. It is also shown that the converter operates very efficiently over a wide output voltage range of 250-400 V, and a wide output power range of 20-200 W. These experimental results demonstrate the effectiveness of the proposed design.

Order-disorder phase transitions in thin films of glassy chalcogenide semiconductors of the system Ge-As-Te, which take place during times on the order of microseconds in micron-sized volumes, have been studied and analyzed. The relationship between the reversible structural transitions induced by laser light pulses and the reversible semiconductor-metal transition taking place in a strong electric field is discussed. It is shown that the film can be taken repeatedly through a reversible phase transition in the conductivity at ∼500–600 K, as previously established. It has been shown that repeated transition from the crystalline to the glassy state is possible without destruction of the material for a wide range of power levels for durations of the laser light pulse less than a few microseconds, and that this fact plays a decisive role in the reversible structural transformations. It is shown that the existence of such a range of power levels is attributable to overheating.

The prosperity of IEEE 802.11-based Wi-Fi networks aggravates cross-technology interference to IEEE 802.15.4-enabled ZigBee networks widely deployed to enable various Internet-of-Things applications. To make ZigBee communication reliable and robust even in a dense Wi-Fi environment, taming Wi-Fi interference in ZigBee networks especially from the perspective of physical layer is of paramount importance. In this context, this work takes aim to design a novel Wi-Fi interference-resilient ZigBee decoder called PolarScout, which separates collided ZigBee signal samples out of Wi-Fi interference to bootstrap ZigBee data decoding. Unlike several existing solutions which need clear signal preamble, tremendous signal strength difference between ZigBee and Wi-Fi, and Wi-Fi interference recognition in prior to ZigBee decoding, PolarScout aims at direct ZigBee decoding in a more generic and challenging case where Wi-Fi interference features a wide range of power levels and arises within a ZigBee packet at an arbitrary position. At the heart of PolarScout lies a subtle shell-shaping technique which harnesses a customized sample sequence to smooth the shell of corrupted signal samples. PolarScout then refers to the resulting shell to recover each contaminated ZigBee sample. Experimental results validate the superiority of PolarScout and its resilience to a wide range of Wi-Fi interference types.

Over the past decade, the telecommunication industry has witnessed excessive growth in the number of mobile users. Market forecasts envision that there will be nearly 8.6 billion mobile devices worldwide by 2017. This tremendous increase in the number of cellular users demands an expansion in the wireless Base Stations (BSs) for improved coverage and capacity. However, this hike in the deployment of base stations will lead to immense energy consumption, because in mobile networks 70–80 % of the power is consumed by BSs. This upsurge in the energy consumption of telecommunication networks implies an increase in CO\(_{2}\) emissions in the environment. In addition, energy bills also represent a major chunk of wireless network operators’ expenditures. These ecological and economical challenges have provoked the curiosity of telecommunication standardization bodies and researchers in an emerging research area termed ‘energy-aware Heterogeneous Networks (HetNets)’. HetNets are a mix of various cell shapes and sizes, including high power macro cells and low power nodes such as micro cells, pico cells and relays. The large macro cells are responsible for the basic coverage of the cell users, and the small cells are effective in providing higher data rates to their nearby users in dense areas with reduced power consumption. The combination of various BSs with different cell sizes and a wide range of power levels can lead to substantial gains in network energy consumption by creating hotspots and enabling dense spatial reuse. It is envisioned that a dense deployment of low power BSs will take place in the near future. HetNets in particular are considered as a promising solution for Fifth Generation (5G) in order to meet the exponentially growing demand for multimedia traffic. The main focus of this chapter is to investigate optimal energy efficient deployment strategies for low power nodes such as relays and small cells in 5G HetNets. In this chapter, a comprehensive overview of remarkable small cell deployment schemes is presented in order to facilitate the debate on technical challenges in deploying HetNets. It goes on to discuss some useful techniques to mitigate the severe interference in 5G dense HetNets. Finally, a novel Long Term Evolution (LTE)-Advanced relay deployment scheme is introduced using graph theory, not only to address some of the identified deficiencies of existing solutions, but also to optimize the energy efficiency of 5G cellular networks.

The continued growth of electric vehicle (EV) deployment has placed increasing emphasis on the development of charging infrastructure that is efficient, reliable, and compliant with safety requirements over a wide range of power levels. In EV charging systems, DC–DC converters work as a key interface for voltage adaptation, power regulation, and battery protection, making the choice of converter topology a crucial design consideration. This study provides a comparative and application-focused review of commonly employed isolated and non-isolated DC–DC converter topologies used in EV charging architectures. The comparison is carried out by examining voltage gain behavior, efficiency tendencies, switching and thermal stress, soft-switching capability, component utilization, control complexity, cost-related aspects, and practical deployment constraints. Fundamental operating principles and representative time-domain simulations are used to highlight relative performance trends of PWM-based and resonant isolated converters under typical charging conditions. Rather than introducing new converter structures or control methods, the objective of this work is to offer practical, design-oriented insights that support informed topology selection. Based on the comparative analysis, non-isolated converters are found to be well suited for low- to medium-power onboard charging applications, whereas isolated resonant converters are more appropriate for high-power and fast-charging systems when safety, scalability, efficiency trends, and system-level implementation factors are considered together.

This paper presents the design of a wide dynamic range rectifier array using a novel adaptive power distribution method. In such a rectifier array, the RF input power is distributed among multiple rectifier devices adaptively, according to their impedances as a function of input power level. Such a rectifier array can achieve high rectification efficiency and low reflection coefficient over a wide range of power levels. The method is experimentally verified with a 900 MHz two-device rectifier array, and demonstrated an efficiency higher than 50% over 17 dB dynamic range (10 dB wider than a conventional rectifier design using the same devices) with a peak efficiency of 66%.

Advanced RTG concepts utilizing improved thermoelectric materials and converter concepts are under study at Fairchild for DOE. The design described here is based on DOE's newly developed radioisotope heat source, and on an improved silicon-germanium material and a multicouple converter module under development at Syncal. Fairchild's assignment was to combine the above into an attractive power system for use in space, and to assess the specific power and other attributes of that design. The resultant design is highly modular, consisting of standard RTG slices, each producing ~24 watts at the desired output voltage of 28 volt. Thus, the design could be adapted to various space missions over a wide range of power levels, with little or no redesign. Each RTG slice consists of a 250-watt heat source module, eight multicouple thermoelectric modules, and standard sections of insulator, housing, radiator fins, and electrical circuit. The design makes it possible to check each thermoelectric module for electrical performance, thermal contact, leaktightness, and performance stability, after the generator is fully assembled; and to replace any deficient modules without disassembling the generator or perturbing the others. The RTG end sections provide the spring-loaded supports required to hold the free-standing heat source stack together during launch vibration. Details analysis indicates that the design offers a substantial improvement in specific power over the present generator of RTGs, using the same heat source modules. There are three copies in the file.

This study presents a systematic and data-driven methodology for proportional-integral (PI) controllers tuning in a gain scheduling approach in a 5 MW th air-cooled recuperated supercritical carbon dioxide (sCO 2 ) Brayton cycle. Off-design operations of sCO 2 systems pose substantial control challenges due to strong nonlinearities in fluid properties near the critical point and pronounced interactions among multiple control loops. Most existing studies rely on manually tuned controllers or simple case-specific gain adjustments, limiting their applicability across wide operating conditions. Although gain scheduling has shown clear benefits, a generalized and fully systematic approach has not yet been developed. To address this gap, this work proposes a fully automatable framework that systematically determines optimal controller parameters as a function of boundary conditions. The methodology comprises: (1) steady-state analysis across a discretized grid of ambient temperatures (5–45 °C) and power levels (25–100%); (2) transfer function identification at each operating point via step-response testing; (3) controller parameter derivation using both MATLAB built-in tools and Internal Model Control (IMC) approach; and (4) systematic testing via transient simulation across the operating conditions. Application to Compressor Inlet Temperature (CIT) control of the cooler demonstrates that the IMC approach with a closed-loop time constant equal to 1/10 of the open-loop one achieves stable and efficient controller performance across the majority of operating conditions. Performance degrades only at extreme conditions of load and air temperature, where air mass flow rates becomes very low (10-30 % of nominal). This regime that should be avoided operationally or mitigated through cooler modularization. • Systematic, automated gain-scheduling methodology for PI controller tuning across wide operating conditions (5–45 °C, 25–100% load) • The developed methodology enables reproducible controller gains calculation independent of manual tuning • For Compressor Inlet Temperature control, Internal Model Control (IMC) with = 1/10 achieves stable, efficient performance except at extreme conditions, where air mass flow becomes very low (<10%) • Critical cooler design-control trade-offs identified: modularization recommended for extreme low-load and low temperature operation

This paper shows information presented to the sub‐group on sources at the Workship on Laboratory EXAFS Facilities April 29, 1980. Rigaku manufactures x‐ray generators in a wide range of power levels. The 1.5kW, 2kW and 3kW units are used with sealed x‐ray diffraction tubes. Rotating anode x‐ray generators are offered in 12kW, 30kW, 60kW and 90kW capacities. This paper will present information on only the 12kW Rotating Anode X‐Ray Generator, Model RU‐200.

be adapted to various space missions over a wide range of power levels, with little or no redesign. Each RTG slice consists of a 250-watt heat source module, eight multicouple thermoelectric modules, and standard sections of insulator, housing, radiator fins, and electrical circuit. The design makes it possible to check each thermoelectric module for electrical performance, thermal contact, leaktightness, and performance stability, after the generator is fully assembled; and to replace any deficient modules without disassembling the generator or perturbing the others. The RTG end sections provide the spring-loaded supports required to hold the free-standing heat source stack together during launch vibration. Detailed analysis indicates that the present generation of RTGs, using the same heat source modules. There is a duplicate copy of this document. OSTI has a copy of this paper.

A scheme is presented for entangling two separated nanomechanical oscillators by injecting broad band squeezed vacuum light and laser light into the ring cavity. We work in the resolved sideband regime. We find that in order to obtain the maximum entanglement of the two oscillators, the squeezing parameter of the input light should be about 1. We report significant entanglement over a very wide range of power levels of the pump and temperatures of the environment.

Aninvestigationaimedatevaluating theperformanceand operationalcharacteristicsoftheSPT-200 wascarried out by Fakel in collaboration with CENTROSPAZIO. The experimental characterization of the thruster was performed bymeasuring itselectrical,propulsive,andoperationalparametersduringa parametrictest.Temperatures of the main thruster components were also measured in order to investigate the thruster thermal behavior. Tests were conducted at Fakel in a vacuum chamber of 17 m 3 volume. The indicated background pressure, measured with ionization gauges calibrated forair, neverexceeded 2.8 £ 10 i 4 torr (uncorrected ). Thethruster was operated overa wide range of power levels, from 2 up to 12 kW. At the nominal operating point of 6 kW, the average specie c impulse and efe ciency, inclusive of all power losses and the cathode e ow, were 1928 s and 0.59, respectively. The maximum efe ciency of 0.63 was obtained at the 11 kW power level and 2950 s specie c impulse.

With the HVDC transmission projects developing rapidly, the relevent electromagnetic environment problems are widely concerned, of which the transient electric caused by the conductor electrification in ionized field may seriously influences the feelings of people. To invesigate the tansient electric shock procedure, the transient current is measured in the experiment. The simulation results agrees well with the measured values and the validity of the simulation model is verified. The simulation results show that the resistance in the discharging circuit can reduce the current evidently. It is also found that the metal objects under the HVDC lines should be grouded to avoid discharging when touched by the people.

this paper explains internal capacitor energy balancing and circulating current control of Modular Multi-level Converters (MMCs). MMCs are considered as one of the promising multilevel converter topologies especially in high voltage applications such as HVDC transmission system. Circulating current is a unique feature in MMC, it arises from capacitor voltage differences between the three phases. The idea behind MMC is to use floating capacitors as a voltage sources, they are inserted or bypassed using a switching circuitry to generate the required output voltage level. To ensure a stable operation, capacitor voltages should be kept in the same level and the total converter energy should be uniformly distributed between the three phases. This can be achieved by controlling the current that circulates between the three phases. In this paper a three phase grid connected MMC is considered. An analytical study has been done, operating principles, mathematical model and control system have been described. Also, the system performance has been verified using simulation with Matlab-Simulink, simulation results were satisfactory and in conformity with the analytical study.

HVDC transmission has become a cost-effective option for transferring high voltage over greater distances. Protecting an HVDC transmission line is more challenging than protecting an AC transmission line due to its low impedance and absence of zero crossing DC current. Power electronic devices have finite overload capability, and standard relays are ineffective for HVDC line protection. Heavy current is generated by DC faults in HVDC (T/L), hence it is necessary to treat DC line faults in short, medium, and long HVDC (T/L) systems with different fault resistance. It is crucial to research fault detection methods based on time-frequency analysis by choosing appropriate algorithms using various (MW) methodologies for short, medium, and long HVDC transmissions at various fault resistances in order to protect the HVDC system. In this work, we examine how the length of an HVDC transmission line and fault resistance at both sides (inverter and rectifier) affects the selection of suitable mother wavelets for DC fault, using mean parameter and time-frequency transformation. SimPower System of Matlab is used to evaluate the impact of HVDC transmission line length and fault resistance on the selection of suitable mother wavelets. Simulation results show that Coif3 is an ideal wavelet for fault detection in medium transmission lines at different fault resistances. On the other hand, Rbio3.1 is more suitable for fault detection in long transmission lines at various fault resistances. For short and medium HVDC transmission lines, different mother wavelets were found to be suitable at different fault resistances. Therefore, it is essential to carefully consider the specific characteristics of the transmission line and the fault scenario when selecting a mother wavelet for accurate fault location.