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Single-phase transformerless inverters are widely installed in grid connected photovoltaic systems due to their outstanding advantages, namely, high efficiency, low cost and high power density. The lack of galvanic isolation leads to common-mode voltage (or current) issues, which are solved by means of modifications to topologies, control schemes and modulation strategies. This study proposes a novel multilevel inverter for single-phase transformerless photovoltaic systems. The topology is based on the neutral-point-clamped inverter, and is aimed to attenuate the leakage ground current. The latter is caused by the common-mode voltage fluctuations affecting the stray capacitances formed between the photovoltaic cells and the grounded frame. On the one hand, the proposed multilevel inverter can synthesise a seven levels output voltage, which reduces the total harmonic distortion. On the other hand, the magnitude of the output voltage can reach up to 1.5 times the DC input voltage, which eliminates the need of a voltage-boosting stage for grid interconnection. This study also presents three dedicated pulse-width modulation strategies, all of them based on the level-shifted multicarrier sinusoidal pulse-width modulation scheme. Numerical simulations and experimental tests in a 1 kW setup have been performed to evaluate the performance of the proposed topology

Currently, the combustion cars of a large number of electronic equipment: the electronic control unit, position sensors, flow sensors, automatic brake system, ABS system, among others. Currently and in broad strokes cars a set of mechanical parts controlled by an electronic system. In the future, cars are fully electronic, but prior to this step, hybrid cars will be developed which have their respective electric motors controlled by a power stage and their internal combustion engine (Cevallos 2016). This paper identifies the disturbances in the automotive systems that are introduced to the micro network of the automobile, its effects to analyze the effects that may have on the LED lighting system. Objetivos: Estudiar los transitorios y permanentes en automóviles para clasificar su comportamiento. Analizar las perturbaciones que pudieran ser perjudiciales para los sistemas electrónicos del automóvil. Cuantificar de perturbaciones a partir de la Transformada Rápida de Fourier (FFT). Estudio y análisis de los efectos a través de la simulación numérica de los transitorios en convertidos de CD-CD empleado para la iluminación.

In this paper, a comparative study of modulation techniques used in a transformerless H-bridge neutral point clamped (HB-NPC) multilevel inverters is presented. Transformerless inverters, usually found in photovoltaic (PV) applications, are more efficient and economically affordable than isolated systems. Nevertheless, they may cause leakage ground currents. The latter are produced by the stray capacitances formed between the PV panel frame and the ground path. There are different ways to overcome the leakage ground current issue in transformerless topologies, for instance using topologies that generate almost zero leakage currents, by using adequate modulation techniques, by inserting additional filters, and by using adequate control schemes, among others. The comparative study, considers five modulation strategies, namely, level-shifted pulse-width modulation (PWM), phase-shifted PWM, three-level PWM, two sectors hybrid PWM and six sectors hybrid PWM. As it will be demonstrated through the common-mode model analysis, the three last modulations strategies are aimed at alleviating the leakage ground current issue. In this study, the two sectors hybrid PWM and the six sectors hybrid PWM are proposed. These modulation techniques lead to obtaining five output voltage levels keeping the RMS value of the leakage currents bounded for the transformerless HB-NPC inverter.

Common mode voltage is an important issue in motor drive systems since its dynamics could produce leakage ground current reducing the machine lifetime. In order to contribute to reduce the effects of the leakage ground current, three-phase power inverters can be designed using dedicated pulse width modulation strategies. Space vector modulation technique is a commonly used continuous method due to its flexibility to implement different vector sequences. In this paper it is proposed a space vector based modulation technique to reduce common mode voltage in a three-phase ANPC inverter. An analysis and comparison regarding conventional space vector modulation techniques are performed. Numerical results are obtained to prove the feasibility of the proposed method.

Batteries performance is an important issue for those systems with an implicated energy storage system where it is important to known three fundamental internal parameters, state of charge (SoC), state of health (SoH) and state of operation (SoF). In order to know these internal states some techniques as adaptive observers are use together with a battery model. In this paper, the main characteristics of the most common and commercial batteries, as well as the most cited batteries models in the literature are studied. Then a comparative analysis making emphasis in its qualities and applications is performed. The main idea of the paper is to provide a wide and fast view of the main characteristics together with the advantages and drawbacks of the batteries and battery models. In future works, this information can be a good reference to design algorithms for parameter identification or internal states estimation.

This paper presents the control design for the regulation and trajectory tracking tasks of the non-minimum phase output voltage of a DC-DC Boost-type power converter. The proposed approach exploits the differential flatness property of the system leading to a control strategy whose benefits include a simple derivation based on the parameterization of the control input and a zero steady-state error in the system response due to the establishment of predefined stable error dynamics. The main contribution of this paper is that the proposed controller is robust against power supply variations that may arise from the use of renewable energy sources. Furthermore, it is also robust against load variations that are normally related to energy consumption demands. These aspects are disregarded in most of the existing control techniques. Successful validation of the effectiveness of the flatness-based control system is carried out through numerical simulations and experimental tests performed in a built prototype of the system.

This paper presents a transformerless single-phase inverter topology based on a modified H-bridge-based multilevel converter. The topology comprises two legs, namely, a usual two-level leg and a T-type leg. The latter is based on a usual two-level leg, which has been modified to gain access to the midpoint of the split dc-link by means of a bidirectional switch. The topology is referred as an asymmetrical T-type five-level (5L-T-AHB) inverter. An ad hoc modulation strategy based on sinusoidal pulsewidth modulation is also presented to control the 5L-T-AHB inverter, where the two-level leg is commuted at fundamental frequency. Numerical and experimental results show that the proposed 5L-T-AHB inverter achieves high efficiency, exhibits reduced leakage currents, and complies with the transformerless norms and regulations, which makes it suitable for the transformerless PV inverters market. 1 1 This updated version includes experimental evidence, considerations for practical implementation, efficiency studies, visualization of semiconductor losses distribution, a deeper and corrected common mode analysis, and an improved notation among other modifications.

Grid-connected low-power PV systems are becoming more and more popular inside the energy market. Such a systems, are commonly installed in residential and small commercial buildings, having as a main objective the reduction of the energy bill. Efficiency is a key word in the design of PV systems since this parameter contributes with economic benefits for the investors. Among low power systems, microinverters are designed to inject the generated energy from a single PV panel to the electrical grid. A single photovoltaic panel produces a voltage around 35 V, therefore microinverters are generally designed using two stages. First stage boost and regulate the output DC voltage while the second stage produces the injected AC current. Single-phase H-bridge inverter is the basic topology used in the second stage of the isolated microinverters. In this paper, a modified hybrid high-frequency H-bridge inverter is proposed using a combination between MOSFET’s and IGBT’s according with the low and high frequency pulse width modulated signals. The proposal is evaluated by means of numerical simulations and compared with transformerless topologies considering the total harmonic distortion and efficiency as the comparative parameters.

The behavior of non-linear systems around the equilibrium points can be classified into stable or unstable node, stable or unstable focus, saddle point and limit cycle. In most cases, these behaviors can be established from the poles of the linear approximation around a given equilibrium point. In this paper the analysis of focus and node qualitative behaviors of DC-DC power electronics converters around a given equilibrium point is studied. Open-loop and closed-loop dynamics are considered. Three different laboratory prototypes of the converters are used, namely, an interleaved buck, an interleaved boost and a double buck with an inductor-capacitor input filter. These prototypes and analysis were used as an aid to study typical equilibrium point behaviors as an introduction to a non-linear system graduate course.

In this paper, the controller for an extended step-down conversion ratio converter is designed and experimentally validated through a laboratory prototype. The converter that is considered is formed by a conventional buck converter to which an array of capacitors and diodes is added at the input that allows extending the step-down conversion ratio. The objective of the controller is to provide closed-loop stability and assure the regulation of the output voltage. Its design is based on the averaged converter model and consists of two control loops, one voltage and one current. Closed-loop experimental results are presented.

In this paper a new modulation strategy for the single-phase H-bridge neutral point clamped (HNPC) topology is presented. The proposed modulation scheme allows the conventional five levels multilevel inverter to generate a seven levels output voltage waveform, without any changes in the structure of the HNPC topology. For this purpose a modulation scheme based on the typical Level Shift Pulse Width Modulation (LS-PWM) is designed. In order to obtain the seven output voltage levels, the DC-link is split in asymmetric form, that is one of the DC-side capacitor voltage is the double of the other one. Numerical results were obtained for a grid-tied photovoltaic system in order to evaluate the performance of the proposed modulation technique. An efficiency analysis of the proposed modulation strategy is also shown to illustrate the advantage of this scheme.

This paper presents a combined method to detect islanding conditions. The method combines two approaches in a two stage process, and is based on the injection of reactive current as a disturbance to detect islanding. In the first stage, the method tests the voltage rate of change and the frequency rate of change. Once an islanding situation is presumed in the first stage, then in the second stage, a positive feedback scheme is enabled to confirm the islanding condition. This combined detection method is more effective and precise, avoids false tripping out by reducing the sensitivity to other perturbations, and avoids instabilities as the positive feedback is not connected all time. Simulations are presented to assess the performance of the proposed combined detection method.

This document presents the design and construction of a plasma generator for electrosurgical applications. The generator is comprised of four main parts: DC power supply, topology push-pull, controller unit and plasma probe. First results generating plasma by repetitively-pulsed electrical discharges in sodium chloride saline solution are reported.

There are two methods widely used by physiotherapists for pain treatment and rehabilitation purposes. These methods are: Thermal contrast therapy and Transcutaneous Electrical Nervous Stimulation (TENS). Thermal contrast therapy usually consists on the application of hot and cold pads over the site of interest during a determined period of time (usually less than 30 minutes). Sometimes, the hot and cold sessions are intercalated for better therapeutic results. The problem with the application of such therapy nowadays is that it is based on pads which must be heated or cooled by mean of external devices (ovens, hot bath and freezers) using energy during the whole day to keep the pads at the correct temperature ready for their use. Another problem is the loss of thermal energy of the pads during their use on the patient skin. Thus, if at the beginning of the therapy the cold (or hot) pad was at the right temperature, after few minutes the temperature will not be enough for the therapeutic result. Furthermore, usually these thermal therapies are applied simultaneously with TENS, thus the physiotherapist requires at least two devices, making their application cumbersome. This paper presents an electronic system for the application of heat or cold and TENS therapies simultaneously. Design and preliminary results on the characterization of the system are presented showing the viability of the proposal. Temperatures over the range of 8 °C – 50 °C were reached and maintained independently of the ambient temperature. TENS was generated with a voltage range of 10 – 50V and frequency from 1 – 300Hz and current output until 50 mA.

Summary In this paper, a controller for a shunt active power filter based on a 3-level neutral point clamped inverter is presented. The proposed controller guarantees compensation of harmonic and reactive powers caused by nonlinear loads connected at the point of common coupling. The controller comprises three control loops, namely, a current tracking loop, a voltage regulation loop, and a voltage balance loop. The current tracking loop is aimed to inject the appropriate current by means of the power inverter to compensate reactive power and harmonic distortion assuring a power factor close to unity. The voltage regulation loop is designed to assure that the DC-link reaches a desired constant voltage level, while the voltage balance loop is aimed to regulate each capacitor voltage on the DC-link towards the same voltage value. The performance of the proposed controller is experimentally validated on a 1 kW prototype.