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Several applications need a high power, high output voltage ac/dc converter. The structure includes a dc/dc resonant stage, which is fed from a three-phase line. Due to standards, rectified dc input voltage varies largely from 400 to 750 V affecting the adversely overall design and current levels. In fact, losses in the inverter become unbearable if both switching frequency and transferred power are desired beyond a certain level. In those cases, it is necessary to connect several switches in parallel. As an alternative, the new switches can configure a new modular structure instead, adding more flexibility in the control to compensate input voltage variations. As a result, the required circulating current is reduced to a half, with benefits in total power losses. Moreover, the nature of the topology allows a reconfiguration of the resonant net (LCC) for low power, reducing even further the minimum circulating current under those conditions (fluoroscopy, for instance). In this paper, the new multilevel resonant topology is mathematically modeled and proposed for radiography and fluoroscopy. An example illustrates the design procedure for a given application at 100 kW, 50–150 kV.

CAPMIX (Capacitive Mixing) technologies are promising electrical generation processes under development which are used for obtaining renewable energy from mixing fluids with different salinities (such as seawater and fresh water). This mixture originates from places like the mouths of rivers naturally. Such technology is inherited from the deionization processes such as CDI (Capacitive Deionization). In this paper, both processes (CAPMIX and CDI) will be described, which can be understood as complementary, because a CDI cell, can be used for both applications. Furthermore, several tests to a commercial CDI cell will be carried out, working in both working modes, validating the previously commented.

Electric mobility will be just as meaningful and effective as the origin of the electricity these vehicles run on. Their effect on pollution and greenhouse gases reduction will not be such unless power plants are mostly based on renewable resources. Thermal power plants are a good solution to produce clean electric energy and contribute to the overall solution. In order for this to be so, it is necessary to guarantee that this type of plants operates smoothly and that the possible problems they may have can be solved. This paper deals with one of these problems: finding the plugs that may form in the pipes carrying the molten salt of the thermal energy storage system. Designing a sensor that can easily estimate the location of these plugs will contribute to reducing the number of hours a thermal power plant must be idle due to reparations.

In solar thermal plants, the use of molten salt as a heat transfer fluid is an advantageous alternative, although it has some disadvantages such as the formation of salt plugs in the pipes due to possible stratification of the salt or its solidification. The aim of this study was to implement an electromagnetic acoustic transducer (EMAT) not only capable of identifying the position of the plug, but also of determining whether the plug blocks the entire conductive surface or, on the contrary, is partial, allowing the fluid to pass through a smaller section. The proposed transducer is intended to be minimally invasive, allowing it to be used in the same way as a temperature probe. To do so, it creates torsional waves in the pipe, which are then used for a combination of measurements: pulse-echo and attenuation of the acoustic waves. Two materials with different densities (silicone and cement) were used in the tests carried out, which made it possible to check that for a given size of blockage, it is possible to identify the type of material from which it is formed.

This paper presents a high-voltage power source to produce glow-discharge plasma in the frame of a specific application. The load has two well-differentiated types of behavior. To start the system, it is necessary to apply a high voltage, up to 15 kV, to produce air-dielectric breakdown. Before that, the output current is zero. Contrarily, under steady state, the output voltage is smaller (a few hundred volts) while the load requires current-source behavior to maintain a constant glow in the plasma. The amount of current must be selectable by the operator in the range 50–180 mA. Therefore, very different voltage gains are required, and they cannot be easily attained by a single power stage. This work describes why the LC-parallel resonant topology is a good single stage alternative to solve the problem, and shows how to make the design. The step-up transformer is the key component of the converter. It provides galvanic isolation and adapts the voltage gain to the most favorable region of the LC topology, but it also introduces non-avoidable reactive components for the resonant net, determining their shape and, to some extent, their magnitude. In the paper, the transformer’s constructive details receive special attention, with discussion of its model. The experimental dynamic tests, carried out to design the control, show load behavior that resembles negative resistance. This fact makes any control loop prone to instability. To compensate this effect, a resistive ballast is proposed, eliminating its impact on efficiency with a novel filter design, based on an inductor, connected in series with the load beyond the voltage-clamping capacitor. The analysis includes a mathematical model of the filtering capacitor discharge through the inductor during the breakdown transient. The model provides insight into the dimensions of the inductor, to limit the discharge current peak and to analyze the overall performance on steady state. Another detail addressed is the balance among total weight, efficiency and autonomy, which appears if the filter inductor is substituted for a larger battery in autonomous operation. Finally, a comprehensive set of experimental results on the real load illustrate the performance of the power source, showing waveforms at breakdown and at steady state (for different output currents). Additionally, the detector’s constructive principles are described and its experimental performance is explored, showing results with two different types of metallic pollutants in water.

Nowadays, the emission of pollutant particles is a global problem in terms of limiting pollution in industries, as well as greenhouse gases emissions. There are different ways to filter undesired particles, such as carbon air filters, chemical washing, and so on. One of the most popular techniques is the use of electrostatic precipitators: The operation mode is based in attracting particles using electrostatic forces. In order to do that, it is necessary to use a high-voltage converter, with a relative complex control. This article deals with the design of a complete platform to control not only these kind of converters, but also those converters based on the full-bridge power topology.

In this article, the modeling of inhibitory grown activity against Tetrahymena pyriformis is described. The 0-2D Dragon descriptors based on structural aspects to gain some knowledge of factors influencing aquatic toxicity are mainly used. Besides, it is done by some enlarged data of phenol derivatives described for the first time and composed of 358 chemicals. It overcomes the previous datasets with about one hundred compounds. Moreover, the results of the model evaluation by the parameters in the training, prediction and validation give adequate results comparable with those of the previous works. The more influential descriptors included in the model are: X3A, MWC02, MWC10 and piPC03 with positive contributions to the dependent variable; and MWC09, piPC02 and TPC with negative contributions. In a next step, a median-size database of nearly 8000 phenolic compounds extracted from ChEMBL was evaluated with the quantitative-structure toxicity relationship (QSTR) model developed providing some clues (SARs) for identification of ecotoxicological compounds. The outcome of this report is very useful to screen chemical databases for finding the compounds responsible of aquatic contamination in the biomarker used in the current work.

This paper describes the theoretical and practical aspects of an LCLC resonant topology, operating at constant frequency (PWM control). This topology combines the behavior ofLLC and LCC converters, introducing the advantage of reducing the value of the series resonant inductor to get high power factor for the resonant tank. The inclusion of a new resonant element, the parallel capacitor, allows reducing the resonant current through the magnetizing inductance, thus reducing the power losses in the transformer. Although part of the transformer losses are transferred to the parallel resonant capacitor, they can be minimized with a correct selection of this resonant component.

The paper studies a parallel resonant converter with a capacitor as output filter to generate and maintain a glow discharge in air. The application requires a high output voltage for air breakdown and much lower values to maintain discharge operation. Attention is payed to converter steady state and dynamic aspects.

A very interesting and useful complement to classical cash-registers is presented in this paper, coming up with a real-time auto-counting solution for the money inside a cash drawer. The system allows knowing not only the total amount of money but also how many coins and banknotes there are of each value. The embedded solution developed has been intended to become a low-cost solution, allowing better control over the money and helping both owners and workers in the establishments. By using this system, new utilities including automatic final balancing, instant error handling when making operations, and the lack of certain types of banknotes or coins inside the drawer or the excess of some in a certain compartment, could be implemented. Coins-counting solution is based on their weight, and small individual scales made by load cells have been integrated in each coin compartment. With respect to the banknotes, an innovative alternative based on the electrical properties of capacitors is presented. Additionally, considering the relevance of interoperability in today&rsquo, s systems, a Bluetooth module has been integrated into the system, allowing for data to be accessed remotely from any smartphone, tablet or computer within the range of the module. In this work, an Android application to both control and interact with the system has also been designed.

In solar thermal power plants molten salt is often used to store and transport the energy that is collected during the day. The external pipe temperature is measured to activate an electric heating system if the temperature approaches the melting point. However, salt solidification cannot be completely excluded from the plant management. Once occurred, the location of a salt blockage is very complex due to the high temperature of the pipe. Therefore, when this problem arises, power plants have to stop production with the consequences in time and cost that this entails. Electro-magnetic acoustic transducers can be used as non-destructive testing systems for this application. A method for salt blockage detection is proposed that is applicable in straight sections of pipes by employing torsional guided waves that are generated with magnetostrictive transducers. The present paper deals with the transducer conception and the design of the power supply to activate it. Two alternatives are proposed and compared to determine the improvement in the amplitude/noise ratio. Finally, the experimental results show the performance of the equipment in a small prototype, thus validating the technique presented.

Electrostatic precipitators (ESPs) are devices used in industry to eliminate polluting particles in gases. In order to supply them, an interface must be included between the three-phase main line and the required high DC voltage of tens of kilovolts. This paper describes an 80-kW power supply for such an application. Its structure is based on the series parallel resonant converter with a capacitor as output filter (PRC-LCC), which can adequately cope with the parasitic elements of the step-up transformer involved. The physical implementation of the prototype includes the use of silicon carbide—SiC—semiconductors, which provide better switching capabilities than their traditional silicon—Si—counterparts. As a result, a new control strategy results as a better alternative in which the resonant current is maintained in phase with the first harmonic of the inverter voltage. Although this operation mode imposes hard switching in one of the inverter legs, it minimizes the reactive energy that circulates through the resonant tank, the resonant current amplitude itself and the switching losses. Overall efficiency of the converter benefits from this. These ideas are supported mathematically using the steady state and dynamic models of the topology. They are confirmed with experimental measurements that include waveforms, Bode plots and thermal behavior. The experimental setup delivers 80 kW with an estimated efficiency of 98%.

The behavior of the series–parallel resonant converter with a capacitor as output filter is analyzed when operating under optimum switching conditions. A polynomial is deduced to quickly compute what switching frequency and duty cycle are necessary at the control to obtain the desired output voltage and power in the converter. This polynomial is so simple that it is suitable for being implemented in low-cost digital processors. It could provide, for instance, a start-up strategy guiding the power supply to a known set point, or it could generate alarms if the currents or voltages measured are larger than expected. In this paper, the steps to obtain such a model are described in detail. As an example, the coefficients of the polynomials are deduced when the series and the parallel capacitor are the same. The grade of accuracy of the model has been demonstrated through experimentation on a prototype.

This paper describes the design of a 255-W (17 $\hbox{V}_{\rm rms}$ , 15 $\hbox{A}_{\rm rms} $ ) filament power supply for a 15-kW electron beam welding (EBW) machine. Simulations and results are also included. The filament of the EBW machine consists of a wire, which is heated by the current flowing through it. Although the filament power supply voltage is low (around 17 V) , it is not grounded. In fact, it is displaced $-$ 60 kV dc with respect to ground. Hence, the filament power supply has to be properly isolated. On the other hand, a well-regulated filament power supply is essential for maintaining the stability of the cathode temperature and, consequentially, the lifetime of the filament. In this way, a control method based on the primary voltage is presented, avoiding any feedback loop from the secondary side. The design process and the simulation and experimental results are included in order to verify the control strategy proposed.

Medical X-ray appliances use high-voltage power supplies that must be able to work with very different energy requirements. Two techniques can be distinguished in X-ray medical imaging: fluoroscopy and radioscopy. The former involves low power radiation with a long exposure time, while radioscopy requires large power during short radiographic exposure times. Since the converter has to be designed by taking into account the maximum power specification, it will exhibit a poor efficiency when operating at low power levels. Such a problem can be solved by using a new multilevel LCC topology. This topology is based on a classical series-parallel resonant topology, but includes an additional low-voltage auxiliary transformer whose function depends on the X-ray technique considered. When radioscopy operation is selected, the transformer will allow the power to be shared between two full-bridges. If fluoroscopy mode is activated, the auxiliary full bridge is disconnected and the magnetizing inductance of the auxiliary transformer is used to increase the resonant inductor in order to reduce the resonant currents, thus improving the efficiency of the converter, This work has been co-funded by the Plan of Science, Technology and Innovation of the Principality of Asturias through Project FC-15-GRUPIN14-122, and by the Spanish Government with the action TEC2014-53324-R.

In this paper, the authors describe the design of an 80kW power converter for an electrostatic precipitator using SiC MOSFETs. The structure of the converter is based on the series parallel resonant topology, PRC-LCC, with a capacitor as output filter. This topology can cope adequately with the parasitic elements of the step-up transformer involved in the application. The SiC switches present lower switching, EON and EOFF, and conduction, RDS against VCE, losses than Si based IGBTs. Therefore, it is possible to operate the converter at higher switching frequencies, and/or support hard switching techniques. The control has been set to maintain the resonant current in phase with the inverter voltage, as a strategy to minimize the resonant current itself and the reactive energy circulating in the resonant tank. This operation mode imposes hard switching in one of the inverter legs, but minimizes switching current maintaining losses under control. The experimental setup delivers 80 kW with an estimated efficiency of 98%. The paper also analyzes theoretically the large and small signal models of the converter. The analysis is supported with a complete set of experimental waveforms and Bode diagrams.

Capacitive deionization (CDI) is becoming a suitable alternative for desalination. The low cost of the material required for it and the lower energy consumption can be two critical factors for the development of this technology. CDI technology does not require a high-pressure system or specific membranes to operate. The energy storage capability of CDI cells allows most of the stored energy to be recovered and used in other CDI cells. The aim of the power stage in charge of the energy recovery is to transfer the stored energy from one cell to another with the maximum possible efficiency to continue with the desalination process. With this goal this paper shows a new control strategy, in which the evolution of the current follows the efficiency of the converter. This new control improves the efficiency behavior of the converter as well as the energy recovery. The CDI modules have been electrically modeled and their electrical parameters have been defined according to the geometrical characteristics of the module. This allows the optimum geometrical parameters to be specified in order to optimize the energy storing process. A mathematical algorithm developed allows an easy simulation of the converter behavior with large input and output capacitors.

Optimized design of high-power braking resistors for traction applications is a complex task. The value of the power dissipated can be very high (up to the order of megawatts) and normally pulsating. In addition, these resistors should stay in predefined, usually small areas on the train, which makes them have to meet some tough specifications: minimum weight, high resistance to vibration, and high reliability and durability. Since it is necessary to anticipate and establish the distribution and evolution of the temperatures reached in different internal areas, it would be necessary to develop a complete numerical simulation using a software tool based on computational fluid dynamics (CFD) for each design, which implies a very high-computational cost. In this paper, a new equivalent electrical circuit is proposed to model the thermal behavior of this kind of resistors. The electrical equivalent circuit parameters are obtained by a newly developed software tool that collects results and trends obtained from a large number of previous CFD simulations. After that, SPICE can be employed to obtain thermal simulations and predict temperature evolutions.

With photovoltaic (PV) systems proliferating in the last few years due to the high prices of fossil fuels and pollution issues, among others, it is extremely important to monitor the efficiency of these plants and optimize the energy production process. This will also result in improvements related to the maintenance and security of the installation. In order to do so, the main parameters in the plant must be continuously monitored so that the appropriate actions can be carried out. This monitoring should not only be carried out at a global level, but also at panel-level, so that a better understanding of what is actually happening in the PV plant can be obtained. This paper presents a system based on a wireless sensor network (WSN) that includes all the components required for such monitoring as well as a power supply obtaining the energy required by the sensors from the photovoltaic panels. The system proposed succeeds in identifying all the nodes in the network and provides real-time monitoring while tracking efficiency, features, failures and weaknesses from a single cell up to the whole infrastructure. Thus, the decision-making process is simplified, which contributes to reducing failures, wastes and, consequently, costs.

The use of solar thermal power plants is considered a cost-effective alternative to produce renewable energy. Unlike other energy installations, in this type of plants the transfer and storage of energy has been solved by using molten salts. These salts run between two tanks through the steam generation system that feeds the turbine. Although the use of salts as a heat transfer fluid is considered an adequate solution, they are not without problems. One of them is the formation of blockages in the pipes due to a partial solidification of the salt, which leads to the shutdown of the installation, with the consequent economic losses. Fast location of these blockages in a minimally intrusive way is the objective pursued in this work. The method to achieve this is based on the use of a new magnetostrictive sensor that simplifies previous designs.

X-ray power supplies must operate under a wide variety of conditions. In fluoroscopy mode, they must transfer from 20 W to 1.2 kW, while in radiography mode they reach up to 100 kW. Input voltage range is also wide: from 400 to 750 V. Designers must achieve full power with lower input voltage, accepting important drops in efficiency under other circumstances. A two-inverter multilevel resonant topology is proposed to address these problems. Adapting the resonant elements, the resulting power stage is versatile enough to minimise the resonant current for both radiography and fluoroscopy. Input voltage fluctuations are compensated by the inverter operations.

Many thermal solar power plants use thermal oil as heat transfer fluid, and molten salts as thermal energy storage. Since the engineering of these plants is relatively new, regulation of the thermal energy storage system is currently achieved in manual or semiautomatic ways, controlling its variables with proportional-integral-derivative (PID) regulators. This paper explores into the results obtained with different control strategies implemented on a complete model of energy storage systems based on molten salt. By doing so, the optimal control method can be identified.

Power supplies for medical X-ray applications must be designed to operate under very different conditions. The converter must be designed to deliver the maximum required power, which usually results in poor efficiency at low power levels. A new multilevel structure is proposed to minimize this problem. It is based on the series-parallel resonant topology (LCC) where a new auxiliary transformer has been added.

In higher education courses, students must face the design of system feedback loops. Power electronics and particularly continuous power supplies provide an ideal environment to introduce classical control theory. This paper shows a simple way to experimentally obtain the dynamic behavior of DC/DC converters. The required material is quite common in any electronic laboratory: a function generator, a data acquisition card and a PC with some software. A computer application has been developed for the management of the equipment and the signal processing. The system is capable to plot converter gain in magnitude and phase for a configurable range of frequencies between 10Hz and 100 kHz. The resulting instrument is portable, low cost and shows excellent performance. The obtained measurement provides high reliability and it is done in a reasonable time. The system is, therefore, an excellent tool for designing feedback loops for DC/DC converters with switching frequencies up to 1 MHz.

Measuring the flatness of a cold-rolled steel strip or aluminum foil is a vital aspect of production quality control. Cold lamination control based on the results of this measurement crucially affects production efficiency, but further processes can modify flatness, which can be lost when the strip becomes cold. We describe a low-cost flatness measurement system to monitor this property at several production line points. The system is composed of a capacitive sensor array, some microcontrollers, and a PC for computing and visualization. Measurements on a production line are provided and analyzed.

Power-factor correction has been one of the hottest topics during the last few years and, hence, many new circuits have appeared. In general, it is assumed that preregulators based on multiplier circuits have poor dynamics and, then, a second stage is needed to improve the output voltage dynamic behavior. The other option is the use of single-stage topologies which have fast output voltage regulation although the input current waveform is not sinusoidal. This work presents an analysis of the dynamic behavior of a conventional power-factor preregulator. The objective is to find the limits of the dynamic characteristics of these circuits when the priority is to improve the output voltage regulation and not the total harmonic distortion or the power factor. A large-signal model is presented and the theoretical results are validated with a prototype.

This work presents a review of power-factor-correction (PFC) circuits for low- and medium-power single-phase power supplies. The main idea is not just to show the state of the art of this topic but to select the most interesting topologies for each application depending on the power level, the input voltage range, and the output voltage. Since IEC 61000-3-2 regulations came into force, many new topologies have been presented trying to obtain a cost-effective solution to reduce the input current harmonic content. Each one of them has its application range due to the inherent characteristics of the topology. Obviously, not every converter is useful for the same application. This is especially perceptible in PFC circuits due to the large amount of different solutions. Hence, this paper tries to show the most appropriate topologies for each application, being the input power and the IEC 61000-3-2 Class some of the main parameters to select it. The scope of the paper is focused on single-phase power supplies belonging to IEC 61000-3-2 Class A and Class D with an input power level below 4 kW.

Four new topologies of active input current shapers (AICSs) for converters with symmetrically driven transformers (such as half-bridge, full-bridge and push-pull) have been proposed. This paper analyzes the extension of the use of these new AICSs topologies to converters with asymmetrically driven transformers. Using some of these topologies, the size of AICS inductors can be reduced and even integrated in a single magnetic core. As in the case of other converters with AICS circuit, the new topologies allow line current harmonics to be reduced and thereby to comply with the IEC 1000-3-2 specifications, whilst maintaining all the features of standard DC-to-DC converters (e.g., fast transient response). Finally, the proposed topologies have been experimentally tested.

This paper deals with the analysis of new implementations of the recently proposed active input current shaper (AICS). Using these implementations, the size of the AICS inductors used in AC-to-DC converters based on "symmetrically driven" DC-to-DC topologies (e.g., half bridge, push-pull, or full bridge) can be reduced and even integrated in only one magnetic core. As in the case of other converters with the AICS, the new implementations allow us to reduce the line current harmonics in order to comply with the IEC 1000-3-2 specifications, maintaining all the features of the standard DC-to-DC converters (e.g., fast transient response). Finally, the four proposed implementations of the AICS have been experimentally tested.

The application of the average current mode control (ACMC) to a new type of very efficient post-regulator is studied in this paper. This post-regulator, called series-switching post-regulator (SSR), has been proposed to improve the dynamic response series-switching of power factor correctors (PFC), The post-regulator exhibits very high efficiency due to the fact that only a part of the total power undergoes a power conversion process. Using ACMC, the bandwidth of the post-regulator increases in relation to the one obtained when a conventional voltage-mode control (with or without feedforward) is used. As a result, the attenuation of the input voltage ripple (100-120 Hz) increases and, a lower bulk capacitor can be used to obtain a low voltage ripple at the output, which is extremely important when a battery is connected at the output. This is rather common in distributed power supply systems.