Mário Martins

Simplified Zero-Voltage-Transition Circuits Applied to Bidirectional Poles: Concept and Synthesis Methodology

This paper proposes the concept and the synthesis methodology of simplified zero-voltage-transition (ZVT) circuits applied to bidirectional pulsewidth modulation poles. The main goal of simplified ZVT circuits is to make possible the use of conventional modulation schemes to accomplish better converter performance and to eliminate the synchronous-switching requirements imposed by ZVT integrated multipole topologies. To derive the simplified ZVT circuits, a synthesis methodology is proposed based on the generalization of the ZVT technique, where the restrictions to achieve the zero-voltage switching for the main converter switches are identified. Thereafter, a set of simplified semiconductor switches composed by only one high-frequency switch is defined to be used in the simplified ZVT auxiliary circuits. Thus, using the proposed synthesis methodology, any simplified ZVT topology can be derived, whether or not they have appeared in a previous publication. In order to validate the proposed approach, experimental results for a three-phase ZVT inverter, employing the minimum-loss space vector modulation and operating at 1.5 kW and 20 kHz are presented. The prototype presented an efficiency of 98% at full load representing an improvement of 0.5% when compared to its hard-switched counterpart and 1.8% when compared to an integrated ZVT topology.

Comparison of H-bridge single-phase transformerless PV string inverters

This paper presents a detailed comparison among single-phase transformerless string inverters for grid-connected PV systems. The characteristics of the PV modules and their non-idealities are taking into the account for the design and the performance of the inverter with respect to the IEEE 1547 Standard. Simulated and experimental results for the inverter topologies are carried out.

High step-up integrated DC-DC converters: Methodology of synthesis and analysis

This paper proposes demonstrate an alternative method of DC-DC converter integration to generate high step-up DC/DC converters. The methodology is based on integration of the common circuits of the standard DC/DC converters and association of the converters output sections. It is presented that for the integration of two non-isolated converters, the output sections can only be series connected, meanwhile parallel and cascaded connection are also possible configurations for the integration of one isolated converter with a non-isolated one. Further simulation and experimental analyses are carried out for the Integrated boost-Zeta and Integrated boost-flyback converters confirming the theoretical analyses.

Extended methodology to synthesize high step-up integrated DC-DC converters

This paper proposes an extended methodology to generate high step-up DC/DC converters. The methodology is based on integration of the common circuits of the standard non-isolated DC/DC converters and association of the converters output sections. For the integration of two non-isolated converters, the output sections are series connected, meanwhile parallel and cascaded connection are only possible for the integration of one isolated converter with a non-isolated one. Further simulation and experimental analyses are carried out for the Integrated boost-Zeta and Integrated boost-flyback converters.

Hybrid power amplifiers - a review

With the aim of synthesizing high-fidelity voltage waveforms without penalizing the system efficiency, several works have proposed hybrid power amplifiers (HPAs) composed of linear and switching amplifiers, combining the features of each approach. The HPAs can be classified as envelope, parallel and series configurations, depending on how the connection between the linear and switching amplifiers is implemented. This way, through a fair review of literature, this work identifies the features of each configuration and presents the main topologies and control techniques proposed hitherto. Therefore, this paper can be useful for selecting an adequate hybrid arrangement for a given application. Finally, future trends in research in hybrid power amplifiers are also addressed.

High step-up voltage gain integrated DC/DC converters

This paper presents a systematic methodology to generate high step-up voltage gain converters based on the combination of two standard DC/DC converters. The converters are combined so that their input sections are integrated reducing the converter component count. Their output sections are associated to derive three basic configurations, the series, the parallel and the cascade outputs. The paper presents as an example, the integration of the boost and flyback converters for which the voltage gain and efficiency in steady state are analyzed. Comparative experimental results among the three integrated boost-flyback laboratory prototypes are carried out. It shows that the Series-IBF and the Cascade-IBF present better and similar performance when compared to the Parallel-IBF converter.

A power electronics and digital control experiment applied to teaching interdisciplinary in electrical engineering

This paper presents a interdisciplinary teaching experience applied to power electronics and digital control. The boost converter with a discrete-time PI controller implemented in a microcontroller is used in this experiment. It is presented a boost converter model and the controller design, beyond the description of instrumentation circuit used. Finally are presented experimental and simulated results. This experiment is applied to UTFPR electrical engineering students.

Performance evaluation of an IGBT module by thermal analysis using fiber Bragg grating

This paper proposes a new method to estimate the energy losses in insulated gate bipolar transistors (IGBT) modules. The technique is based on measuring the temperature of the semiconductor junction through optical sensors based on fiber Bragg gratings. The IGBT module is monitored through software, enabling a real-time evaluation of performance, which facilitates the analysis of the device in different operating conditions. The results are compared with conventional techniques to validate the method.

Comparative analysis between integrated and simplified ZVT topologies for three-phase inverters

This paper presents a comparison between the integration and simplification principles of zero-voltage-transition (ZVT) circuits applied to three-phase inverters. Initially, both approaches are defined, and their advantages and limitations are identified. Thereafter, a comparison is made between two selected topologies, taking into account their modulation strategies, the resulting losses in the main circuit, and the harmonic content of the voltage synthesized by the converter. Finally, experimental results for the selected topologies operating at 1.5 kW and 20 kHz are presented in order to validate the proposed methodology.

Input Stage With Double Functionality Applied To A High Performance Three-phase Ups

This work presents a topological configuration that allows the input stage of a double conversion UPS to be used as a three-phase rectifier and a DC/DC voltage boost converter in normal and backup operating mode, respectively. Thus, the use of a specific circuit for the discharge of the battery bank, which would be rated for UPS nominal power, is avoided. The operation analysis of the proposed input stage is presented, as well as the mathematical modeling and the control system that guarantee the applicability in the input power factor correction, DC bus voltage control and for the DC bus capacitors voltage balance. Hardware-in-the-loop results are acquired for a 20 kVA three-phase UPS to validate the developed analysis besides to demonstrate the good performance of the system.