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A new feeding concept for electrical transportation systems is presented, based on supercapacitive energy storage. Supercapacitors are new and powerful components for energy storage. Compared with batteries, the amount of energy supercapacitors can store is low and does not allow large vehicle autonomy. Because supercapacitors have the property to be re-loadable in a few seconds, a sequential supply system has been developed, considering repetitive feeding at the stops. To solve the problem of the high power amount needed to reach short refill times, a solution is proposed, which consists of using an intermediary supercapacitive tank placed at fixed stations, which is refilled between the bus arrivals with a much lower power. In addition to the description of the needed power electronic converters, theoretical and experimental results are presented, defining the controlled profile of the instantaneous power level, in order to achieve a fast energy transfer between two supercapacitive tanks.

This paper proposes a switched-capacitor (SC)-based step-down AC–DC power converter with high-frequency feed without rectifier or transformer. The operational principle of the circuits and the design considerations are described. The main advantage of the circuit is that step-down voltage can be achieved in the circuit by simply configuring with cascaded stages, which will be much more convenient to be modular development and easy for replacement and maintenance; the voltage and current stresses of most components are smaller than the conventional converter. Using buffer capacitor to reserve energy, there are no magnetic energy storage elements in the circuits. Weight and size can be further reduced due to high-frequency-power line operation. Zero current switching (ZCS) is achieved by introducing small resonant inductors. Therefore, higher efficiency and power density can be achieved. The performance of the converter has been demonstrated by an experiment with 50 kHz 50 V power feed which is emulated by a signal generator and high-frequency amplifier to prove the concept.

Three-phase voltage source converters (VSC) are commonly used to convert ac power from a three-phase grid to a regulated dc voltage with unity input power factor. The control of the VSC is normally achieved by an outer voltage feedback loop and a sinusoidal pulse-width-modulated (SPWM) inner current loop. However, the nonideal power grid and the presence of other interacting loads give rise to nonlinear operation and drive the VSC to enter an irreversible instability region. In this paper, an irreversible bifurcation phenomenon in a three-phase voltage-source converter connected to a power grid with an interacting load is reported. The converter can also be regarded as exhibiting a catastrophic bifurcation in which the input current expands to cause undesirable component stress. A large-signal analysis is adopted to identify the physical origin of the phenomenon and to locate the boundary of the instability.

This paper presents a study of the existence conditions of limit cycles and mechanisms when losing their stability in an open-loop DC–DC boost converter loaded with a constant power load and operating in discontinuous conduction mode. First, the existence conditions are determined. Then, boundaries associated with different kinds of instabilities such as the classical smooth fold and period-doubling bifurcations and nonsmooth border-collision bifurcations such as fold border-collision bifurcations are elucidated. To perform the stability analysis, an implicit 1D map for the system is derived. From this model, it is obtained that smooth period-doubling and fold bifurcations may occur at certain values of the circuit parameters. Some results from numerical simulations performed on the circuit-based switched model are provided showing consistency with the theoretical analysis from the derived model.

This paper provides a comprehensive study on reliability issues related to DC-DC converter design. First of all, some common reliability issues and DC-DC converter design topologies are discussed. Then, a reliability sensitivity study results on an industry standard VRM is presented using a prediction-based design-for-reliability and sensitivity analysis tool created by the author and colleagues at HP. The thermal design issues and component derating in the converter design are discussed. Since electronic component reliability has been a bottleneck in DC-DC converter reliability, the component reliability issues are discussed and some reliability application guidelines are also provided for the DC-DC converters reliability design. In the last part of the paper, an integrated reliability testing, qualification, and quality control procedure is presented using highly accelerated testing methodology. The use of this procedure by HP on DC-DC converter reliability and quality control has shown promising results.

Analysis of field failure data collected from various wind farm databases indicates that the power converters are among the most critical components in offshore wind turbines, since they suffer from a high failure rate. One efficient approach to enhance the reliability and availability of the wind power systems is through using a redundant converter design, in which a set of power converters is placed together in parallel. The main advantage of a multiple parallel converter system is that the failure of one converter will not necessarily lead to the failure of the entire system. It may however increase the wind turbine's acquisition cost, volume, and weight. In this paper, we propose an approach of joint redundancy and maintenance strategy optimization for offshore wind power converters, aiming to simultaneously determine the "optimal allocation of redundant converters" and the "optimal threshold number of converters that are allowed to fail before sending a maintenance crew to the offshore platform". The optimal solution under various system-level constraints (such as reliability, weight, and the available space in nacelle) is derived and the conditions required to make using a redundant system beneficial are discussed. The proposed design is applied to an offshore wind turbine system and its performance is evaluated using a Monte-Carlo simulation technique. Finally, the results are compared with the conventional power converter system and a sensitivity analysis is conducted in order to make the proposed approach applicable for the next generation of wind turbines.

One topology widely known for use in high-voltage high-power converter in medical equipment is the Series Loaded Resonant (SLR) converter. As the power level required by medical equipment increases, there is a need to parallel the SLR converter for improved efficiency and performance. This paper presents the development of a circuit model for paralleled SLR converter to aid circuit designers evaluate circuit performance before the actual hardware is implemented. Each section of the circuit is modeled individually using sinusoidal approximation and circuit network methods. The derived model is then extended to include the parallel connection of the converter. The validity of the model is then tested by using computer simulation and hardware setup to demonstrate the converter's switching waveforms, output voltage and efficiency. Results from both simulation and hardware show good agreement, which demonstrate the validity of the derived model and its usefulness in the initial design of the converter.

The planned upgrade of instrumentation sensitivity in the ATLAS experiment of the Large Hadron Collider (LHC), at CERN, calls for a new type of power distribution architecture. Moreover, power supplies require DC-DC power converters able to work in very hostile environment and maintaining high level of Reliability, Availability, Maintainability and Safety (denoted as RAMS requirements) during the experimental activity. Two main issues need to be discussed: first, electronic devices and equipment must operate in very high background of both charged and neutral particles and high static magnetic field and, second, the increase of the radiation background and the requirements of new front-end electronics are indeed incompatible with the current capability of the actual distribution system. The APOLLO R&D collaboration, funded by the Italian Istituto Nazionale di Fisica Nucleare (INFN), aims to study dedicated topologies of both distribution system and DC-DC power converters and to design, build and test demonstrators, developing the needed technology for the industrialization phase. The collaboration has designed a 3kW, 280V-12V converter (MC) based on the Switch in Line architecture (SIL), a DC to DC phase-shifted converter characterized by a disposition in line of the MOSFETs with good soft switching performances, and in the last year many steps have been taken to enhance the power dissipation and the reliability and to improve the general features of the designed converter. In particular a new water heat sink was designed on the basis of TFD simulation accounting for the layout of the specific converter. Experimental activities in order to characterize both thermal and electrical features of the MC confirm the correctness of the adopted design criteria.