This work presents the analysis of a two-quadrant regulator connected to the DC-link of a 4-quadrant magnet supply. The key objective is to present some regulation strategies for controlling the peak power required from the power network as well as to recover the magnet energy into capacitor banks. A comparative study that highlights the trade off between the size of reactive elements, and the peak current drawn from the electrical network is presented.

This work presents a control system suitable for high-precision pulsed current sources. The proposed control system is based on the detection of events so as to define changes in the power converter state to produce the required current waveform with a good dynamic response. Additionally, this control system is designed to regulate the flat-top current with a well-defined precision. In order to mitigate the effect of the measurement noise, an estimation algorithm for the controlled current is incorporated. This algorithm generates a filtered version of the controlled variable without affecting the control dynamics. The use of the estimated current allows to improve the detection of the events and to avoid an increase in the number of commutations due to possible erratic comparisons. Then, the estimator gains are tuned by using genetic algorithm techniques to optimize the root-mean-square value for a typical pulse. Furthermore, in order to independently perform the required set of tasks, the proposed control system is implemented by using a digital platform based on a field-programmable gate array. Additionally, due to the demanding precision in these applications, different considerations regarding its implementation, such as the digital wordlength, binary point position, rounding method, and overflow behavior, have been taken into account. Experimental results obtained from the application of the proposed control system to a laboratory prototype are presented.

This work presents a topology for a pulsed current power supply suitable for particle accelerator applications. The current pulse is generated from the energy provided by a structure tied to the electrical network and by one connected to a capacitor bank; which is used as local energy storage. By using both structures, disturbances on the electrical network are minimized, since the power obtained from the grid is limited to the average active power of the load; while the management of the reactive power lies on the energy storage structure. A control scheme for the power management of both structures is presented, and simulations are carried out taking into account the parameters of a particle accelerator transfer line.

This study presents a novel multistructure power converter capable of generating high current pulses with short rise and fall times, and high precision in the flat-top. The proposed topology is based on the use of three conversion structures operated with current, voltage and switching frequency ratings in line with the different requirements of each pulse stage. In order to achieve the required precision, a switched-mode compensation structure in series with the load is used. Though this structure must handle a high load current, it is designed to deviate most of the load current to an auxiliary inductor; thus reducing the semiconductor devices requirements. Moreover, the use of this compensation strategy results in a first-order model of the circuit, which leads to an oscillation-free response during structures interconnection. This feature minimizes the required flat-top time, which in turn decreases the power losses on the load. Experimental results based on a scaled-down laboratory prototype validate the capability of the proposed topology to produce current pulses according to the specifications of high-precision applications.

This work presents the implementation of a control system for a high-precision pulsed current source. The proposed control scheme employs a digital hysteresis to achieve a well-defined precision and a high dynamic response. The existence of measurement noise, comparable with the amplitude of the hysteresis bands, generates unwanted commutations that tend to increase the power losses in the semiconductors and to reduce overall system efficiency. As a solution, a current estimation algorithm is proposed. This estimator incorporates the semiconductors state information to improve the filtering capability without affecting the measurement dynamics. Experimental results validate the proposed control scheme.

Closed-loop stability analysis of line-commutated converters (LCCs) has been mainly based on linear, small-signal plant transfer modeling for the power stage. The inaccuracies derived from the use of these simple models in the frequency domain have led to conservative compensation strategies with reduced loop bandwidths. This paper presents a nonlinear time-domain approach for modeling LCCs under integrating control. The proposed technique was found useful to assess the onset of loop instability under different operating conditions. Bifurcations and possible routes to chaos in the parameter domain are also explored. The method is validated by simulation and stability boundary conditions leading to period-doubling behavior are demonstrated by means of experimental results.

Accurate harmonics estimation has become a key issue in power quality assessment.This paper deals with a discrete Fourier transform (DFT)-based measurement technique, which can be easily employed to accurately determine the harmonic components of a distorted signal, i.e., voltage or current.The proposed method is based on a modulated sliding DFT algorithm, which is unconditionally stable and does not accumulate errors due to finite precision representation, and a variable sampling period technique (VSPT) to achieve a frequency adaptive mechanism.It is worth noting that the VSPT changes the sampling period for a variable grid frequency condition, leading to a constant sampling frequency under steadystate conditions.The proposed method provides: 1) high degree of accuracy; 2) structural/performance robustness; and 3) frequency adaptability.Given the modular nature of the method, it is implemented on a field programmable gate array.Simulations and experimental tests are shown to verify the performance of the proposed method.

This paper provides the general description, design guidelines and implementation issues of a digital Thyristor Gate Control (TGC) system developed for particle accelerator facilities. The present proposal improves the TGC performance by replacing the conventional synchronization method based on a single phase zero crossing Phase Lock Loop (PLL) with a novel three-phase synchronous method known as Variable Sampling Period Filter PLL (VSPF-PLL). The proposal is implemented in a custom board and it is tested in a 6-phase power converter under a very distorted mains.

This paper presents a comparison between topologies suitable for capacitor charging systems. The topologies under evaluation are a flyback converter, a half-bridge series resonant converter and a full-bridge phase-shifted converter. The main features of these topologies are highlighted, which allows the proper topology selection according to the application requirements. Moreover, the performed analysis permits to characterize the operational range of the main components thus allowing their appropriate sizing and selection. Simulation results are provided.

Interleaved power converters are used in high-current applications due to their inherent reduction of semiconductors stress and total ripple. Ripple reduction is accomplished by a correct phase shifting, and the filtering improvement explained by the increase in the ripple frequency. However, these benefits are wasted, among other reasons, by the mismatch of the phase inductor value. As a consequence, differences in the ripple amplitude among phases are produced, leading to a total current ripple significantly greater than the ideal case, the loss of the cancellation points and the generation of the switching frequency component and its harmonics. The works dealing with this subject matter have focused on particular cases, such as a given number of phases, a specific converter topology, or a particular case of inductance mismatch, disregarding a general analytical approach. This paper proposes an analytical method to characterize the total ripple in steady state as a function of the duty cycle and the number of phases under any condition on inductance mismatch. Experimental results validate the proposed method.

This paper presents a current sensing method to estimate the load current in pulsed current applications using a current transformer. The droop effect generated by this kind of sensor when measuring dc currents is compensated by means of signal processing techniques. The method is based on the inclusion of a sensor model in the system model so as to obtain an extended state-space model enabling to estimate the load current. A Kalman observer is employed in order to obtain an estimation with high noise rejection. The implementation of the observer in an FPGA platform allows the incorporation of this block as a stage independent of the converter control. Experimental results validate the implementation of the proposed system

When it comes to high-power current sources, multiphase buck converters become an attractive alternative to deliver high currents. However, large variations in current reference or load voltage lead to disturbances that require high dynamics in the transitory response of current control. This letter presents a current control for high-dynamic, high-power multiphase buck converters. The control proposed is based on the synchronization of zero-crossing current ripples with a time reference pattern. This control forces a correct interleaving and is capable of responding, with a reduced transitory time, to major changes in current reference and load voltage. Experimental results validate the proposal.

Este documento presenta los resultados del estudio realizado de la descomposición wavelet multinivel 1D de las señales perturbadas del par electromagnético y de la velocidad del eje del motor trifásico de inducción, cuando este es sometido a diferentes tipologías de huecos de tensión según la caracterización ABC, Bollen (2000). Los huecos de tensión trifásicos (3 variables) son analizados indirectamente en el efecto producido en una variable perturbada (el par electromagnético o la velocidad del eje) que contiene indirectamente información del tipo de hueco de tensión trifásico producido en el estator. El estudio analiza el efecto de los siete diferentes tipos de huecos de tensión, considerando también la influencia de la duración y tensión retenida. Para cada caso se obtiene un vector cuyos elementos son los niveles de energía wavelet en los distintos niveles de descomposición de la variable analizada, mostrando que la forma en que se distribuye la energía de la señal 1D en los distintos niveles de descomposición establece una firma única para cada caso. Esta forma de descripción de los huecos de tensión producidos en el estator, basada en la descomposición multinivel de una variable perturbada, reduce la cantidad de variables a analizar y permite posteriormente la clasificación de las perturbaciones empleando técnicas de inteligencia artificial; es ventajosa pues el almacenamiento de los vectores de niveles de energía de aproximación en las bases de datos emplea menor cantidad de espacio que la necesaria para una señal temporal, y empleando una DWT reversible es posible, además, reconstruir la variable de estado temporal.This document presents the study results of the wavelet 1D multi-level decomposition of perturbed electromagnetic torque and shaft speed signals, of the three-phase induction motor, when it is subjected to different types of voltage sags, as characterization ABC, Bollen (2000). The three-phase voltage sags (3 variables) are analyzed in the effect on a perturbed variable (the electromagnetic torque and mechanical speed) that contains indirect information from the voltage sag occurred in the stator. The study examines seven different types of voltage sags, also considering the influence of duration and retained voltage. For each case, a vector whose elements are the energy levels at different wavelet decomposition levels of the analyzed variable is obtained, showing that the way 1D signal energy is distributed at different levels of decomposition set a unique signature for each case. Thisform of description of the voltage sags, produced in the stator, based on the multi-level decomposition, reduces the amount of variables to be analyzed and subsequently allows the classification of the disturbances using artificial intelligence techniques; storage is advantageous because the vectors of energy levels of approximation in databases used less amount of space required for a temporary signal, and employing a reversible DWT, it's also possible to reconstruct the state variable.

Complementary sets of sequences are currently being applied to signal coding, radar, and multi-user systems, among others. Their particular mathematical properties make them adequate for multi-emission and noisy environments. Nowadays sustained efforts are being devoted to reduce the calculations involved in the generation and/or correlation of these signals by means of recursive algorithms. Some authors have proposed efficient algorithms that are based on modular architectures made up of adders, multipliers and delays. This work introduces a new approach to correlation algorithms of complementary sets of sequences, which is based on a transposition of the generation process. This approach allows to notoriously reduce calculations, and enables the simultaneous correlation of M sequences, without adopting time multiplexing schemes or complex parallel implementations. The correlation algorithm is theoretically demonstrated and its calculation performance is evaluated in a hardware reconfigurable platform. A comparison with other algorithms is included, considering the amount of calculations as a function of the length of the sequences.

Multiple-stage converters are composed of a set of structures with different voltage, current and switching frequency capabilities. In particular, in applications like particle accelerator beam deflection and focusing, the requirement is high-current high-precision current pulses generation. In order to satisfy the specifications of this application, a novel multiple-stage converter topology was proposed and presented in a previous work. However, said proposal should be complemented with a control system to perform the control of each structure, manage its global interconnection and execute the regulation loops. This work describes the implementation of the digital control developed for the proposed converter. Experimental results are presented by applying the proposed control to a prototype.

This paper proposes a novel variable sampling period filter phase-locked loop (VSPF-PLL) for use in the general area of three-phase systems. It is based on the concept of variable sampling period, which allows to automatically adjust the sampling frequency to be NPLL times the line frequency. Conventional three-phase PLL are based on synchronous reference frames (SRFs) to estimate the phase error between the PLL and the input signals. However, SRF transform fail when the voltage waveforms are distorted. In this paper, a sliding-Goertzel-transform- based filter is used in the loop to reject disturbances, such as unbalanced voltage and harmonics. It allows to detect the positive sequence present in the systems without errors. Characteristics of VSPF-PLL, including its mathematical model as well as steady state and dynamic responses, are discussed in this paper. The method is implemented in a DSP and tested using typical disturbances, such as frequency steps, unbalances, harmonics, saturation, and line-to-ground fault. Comparative simulations are performed between the proposed VSPF-PLL and some of the most common three-phase PLL described in the literature. Advantages of the proposed system over the methods analyzed are also discussed. Structural simplicity, robustness, and harmonics rejection are other attractive features offered by the proposed system.

Este documento presenta los resultados del estudio realizado de la descomposición wavelet multinivel 1D de las señales perturbadas del par electromagnético y de la velocidad del eje del motor trifásico de inducción, cuando este es sometido a diferentes tipologías de huecos de tensión según la caracterización ABC, Bollen (2000).Los huecos de tensión trifásicos (3 variables) son analizados indirectamente en el efecto producido en una variable perturbada (el par electromagnético o la velocidad del eje) que contiene indirectamente información del tipo de hueco de tensión trifásico producido en el estator.El estudio analiza el efecto de los siete diferentes tipos de huecos de tensión, considerando también la influencia de la duración y tensión retenida.Para cada caso se obtiene un vector cuyos elementos son los niveles de energía wavelet en los distintos niveles de descomposición de la variable analizada, mostrando que la forma en que se distribuye la energía de la señal 1D en los distintos niveles de descomposición establece una firma única para cada caso.Esta forma de descripción de los huecos de tensión producidos en el estator, basada en la descomposición multinivel de una variable perturbada, reduce la cantidad de variables a analizar y permite posteriormente la clasificación de las perturbaciones empleando técnicas de inteligencia artificial; es ventajosa pues el almacenamiento de los vectores de niveles de energía de aproximación en las bases de datos emplea menor cantidad de espacio que la necesaria para una señal temporal, y empleando una DWT reversible es posible, además, reconstruir la variable de estado temporal.