Showing papers by "Telles Brunelli Lazzarin published in 2018"

High Step-Up DC–DC Converter With Active Switched-Inductor and Passive Switched-Capacitor Networks

Abstract: High-gain voltage conversion is a feature required for several applications, especially for power processing of low-voltage renewable sources in grid-connected systems. In this scope, the presented paper proposes a novel transformerless high gain step-up dc–dc converter based on an active switched-inductor and a passive switched-capacitor networks. The main advantages of the proposed converter are the high voltage gain (>10), the reduced voltage stresses across the switches and the reduced number of components when compared to topologies that provide the same voltage gain using similar principles. The detailed analysis of the proposed converter and a comparison considering other topologies previously published in the literature are also presented in this manuscript. In order to verify the proposed converter performance, a prototype has been built for a power of 200 W, input and output voltages of 20 and 260 V, respectively, and switching frequency of 50 kHz. Experimental results validate the effectiveness of the theoretical analysis proving the satisfactory converter performance, which peak efficiency is around 95.5%.

Hybrid Nonisolated DC–DC Converters Derived From a Passive Switched-Capacitor Cell

Abstract: This paper presents a hybrid nonisolated dc–dc commutation cell, which is generated by the integration between conventional commutation cell and ladder-type passive switched capacitor (SC) cell. From the resulted hybrid cell are derived three different dc–dc converters: a buck-type, a boost-type, and a buck–boost-type. The three structures are analyzed in this paper and are presented the topological stages, static gain characteristics in continuous conduction mode and discontinuous conduction mode, steady-state analysis. The analyses are generalized in relation to the number of switched-capacitor cells employed, which allows the increase of the rated gain of the converters by adding more SC cells. In addition, the proposed hybrid nonisolated dc–dc commutation divides naturally the voltage stress among the semiconductors and capacitors of the power stage. A 1-kW prototype was developed to verify the operation of the three proposed converters and their theoretical analysis. For the buck-type topology, designed with an input voltage of 600 V and output voltage of 450 V, a peak efficiency of 99.2% and efficiency at rated power of 99% were obtained.

Single-Phase Hybrid Switched-Capacitor Voltage-Doubler SEPIC PFC Rectifiers

Abstract: In this paper, the switched-capacitor concept is extended to the voltage-doubler discontinuous conduction mode SEPIC rectifier. As a result, a set of single-phase hybrid SEPIC power factor correction rectifiers able to provide lower voltage stress on the semiconductors and/or higher static gain, which can be easily increased with additional switched-capacitor cells, is proposed. Hence, these rectifiers could be employed in applications that require higher output voltage. In addition, the converters provide a high power factor and a reduced total harmonic distortion in the input current. The topology employs a three-state switch, and three different implementations are described, two being bridgeless versions, which can provide gains in relation to efficiency. The structures and the topological states, a theoretical analysis in steady state, a dynamic model for control, and a design example are reported herein. Furthermore, a prototype with specifications of 1000-W output power, 220-V input voltage, 800-V output voltage, and 50-kHz switching frequency was designed in order to verify the theoretical analysis.

Reduced Switch Count Step-Up/Step-Down Switched-Capacitor Three-Phase AC–AC Converter

Abstract: A direct three-phase ac–ac converter based on the switched-capacitor principle and ladder structure is presented in this paper. Additionally, the boundary between partial charge and no charge modes of a switched-capacitor operation is defined. All switched-capacitor direct ac–ac converters described in the literature employ four-quadrant switches; however, the proposed structure works with two-quadrant switches. This characteristic is the main advantage of the proposed structure because it reduces the number of MOSFETs employed in the power circuit, increasing the converter reliability. Furthermore, the proposed converter can operate as a step-up or step-down circuit, i.e., it is a bidirectional topology. The converter offers high performance with regard to efficiency, power density, and power factor, and it can also be used as an electronic autotransformer. The analysis, design methodology, and experimental results obtained with a prototype with 220/110 V and 3.5 kW are described herein. At the rated power, an efficiency of 95.1% for step-up and step-down modes, capacitive power factor of 0.94, and output voltage regulation of 96% were obtained.

A Family of Voltage-Multiplier Unidirectional Single-Phase Hybrid Boost PFC Rectifiers

Abstract: This paper presents three unidirectional step-up ac–dc converter topologies with voltage multiplication on their outputs. The first topology is the hybrid boost rectifier and the other two are novel bridgeless structures, all based on the integration of boost rectifier and the ladder switched-capacitor (SC) cell. The new hybrid structures provide high voltage gain with low voltage stress across the switches, high-power factor, and output voltage regulation. This paper presents the principle of operation, steady-state and dynamic analysis, design methodology, and experimental verification. A different approach is also presented for the design methodology of the SC cell and for the analysis of its influence on the dynamic model. Three 1000-W prototypes with a 220-V input voltage, 800-V output voltage, and 100-kHz switching frequency were designed to corroborate the theoretical study. The best efficiency was 97.1 $\%$ in the proposed bridgeless versions and the voltage stress across the switches stands around 400 V. Furthermore, a comparison between the proposed structures and previous topologies is also presented.

High Voltage Power Supply Using a T-Type Parallel Resonant DC–DC Converter

Abstract: In this research, the study and implementation of the t-type parallel resonant dc–dc converter in high-voltage power supplies for travelling wave tube applications is presented. The proposed converter shares the benefits of the traditional full-bridge parallel resonant dc–dc converter, such as zero voltage switching on primary side switches over a wide load range, symmetric three-level voltage across the transformers primary winding, and integration of transformers leakage inductance and winding capacitance during its basic operation. However, only two switches are subjected to the input voltage, while the other two switches are subjected to half of the input voltage. Theoretical analysis, commutation analysis, and design guidelines are presented. The theoretical analysis validation and efficiency investigation are conducted through a t-type parallel resonant converter prototype, which operates with 1.5 kW and 97.12% efficiency. Hence, experimental results of a travelling wave tube power supply prototype operating with 1.5 kW of output power, 400 Vdc input, and four high output voltages, whose measurements results are $V_{o1}=1382\,\rm {V}$ , $V_{o2}=3505\,\rm {V}$ , $V_{o3}= 1504\,\rm {V}$ , and $ V_{o4}=3338\,\rm {V}$ , confirm the feasibility of the proposed implementation.

Direct 48V to 1V Step-Down DC-DC Converter

Abstract: A new solution based on switched-capacitor (SC) to convert 48 V to 1 V is presented herein for data center applications. The topology integrates four ladder SC cells and a Buck converter. All stages are connected in cascade and thus the topology provides a high gain ratio with good output voltage regulation. The work propos a modification of the ladder SC cell, which allows the cascade connection with a reduced number of components making simples integration among the cells. The SC stages convert from 48 V to 3 V and the Buck stage changes 3 V to 1 V, and thus the proposed structure uses switches, capacitors and just one inductor (from Buck stage). These features make the structure adequate to be built in an integrated circuit (IC). In addition, the power rating may be increased by adding more converters in parallel. The paper discusses the topology, static gain, voltage stresses, modeling, efficiency, and a comparison with the ladder association of SC (commonly used). The topology was verified by simulation results under 20 A in output current with Gallium Nitride (GaN).

New topology for a single-phase buck-boost inverter

Abstract: This paper presents a new single-phase voltage source inverter based on two Buck-Boost dc-dc. The Buck-Boost inverter is driven by two 180° phase-shifted dc-biased sinusoidal references. This new topology can generate an instantaneous output voltage higher or lower than the input dc voltage without an intermediate power stage or transformer. In this converter both Buck-Boost outputs voltages are used to feed the load in one differential connection. As a drawback, this topology presents an inherent nonlinear behavior due to its variable operating point. To overpass it a linearization scheme is proposed in this paper. Operation analysis and experimental results are included in this paper.

Study of High Step-Up Gain DC-DC Converters based on Stacking of Non-Isolated Topologies

Abstract: This paper approaches the study of stacked DC-DC converters with high step-up gain, using lowvoltage devices. The proposed topologies are generated from the stacking of conventional buck-boost structures and they are suitable in applications that a high conversion ratio is req ired. The stacked converters can also be employed as DC bus to provide one or several output voltage levels with self-balancing, and thus different loads can be connected to one or more capacitors of the stack. A generalized theoretical analysis of the proposed topologies approaching static gain, voltage and current stresses on the main components and power flow analysis is described in this paper. A 1-kW prototype with 100 V input voltage and 400 V output voltage was designed, built and tested. The experimental results corroborate the generalized theoretical analysis and they demonstrate the feasibility of the proposed converters. 

High-Gain Modular Three-Phase Hybrid Boost Rectifier for Small Wind Energy Harvesting System

Abstract: The use of small wind turbines for distributed generation has increased due to the pursuit of renewable and clean energy systems. Small wind turbines usually have low output voltage, therefore a conversion system is necessary to increase the voltage value in order to deliver the harvested energy to the commercial grid. This paper proposes a modular three-phase hybrid boost rectifier topology as the input stage for a wind energy conversion system (WECS). The proposed rectifier is a three-phase variation of the hybrid boost rectifier, which uses a ladder switched-capacitor cell to multiply its output voltage gain by an integer conversion ratio. The system is supplied by a small wind turbine with an open-end winding permanent magnet synchronous generator (PMSG), thus the use of a modular topology is possible and the converter can control the phase currents individually. The system is controlled by a maximum power point tracker (MPPT) that generates a peak current reference for the rectifier, which controls the input current of each phase to obtain a unity power factor. The output dc-link voltage is controlled by an inverter that delivers the extracted energy to the grid. An averaged equivalent circuit is proposed to improve simulation time and to obtain reduced order transfer functions. Theoretical analysis and simulations of a system with three-phase 84 V input, 220 V output phase voltages and 6.5 kVA rated power are presented.

Control System for Multi-Inverter Parallel Operation in Uninterruptible Power Systems

Abstract: This paper proposes a network communication system applied in a control strategy for parallel-connected multi-inverters, which is based on a distributed control system and a redundant communication system. The control system is produced by a Phased-Locked Loop (PLL) synchronism algorithm, a voltage controller and a parallelism controller. All control systems are based on instantaneous values and in the parallelism control the inverters share a single voltage reference signal. The communication system, which is the main focus of the paper, is based on two buses: one analog, which is a measurement taken from the electrical grid; and one digital, comprised of a Controller Area Network (CAN). The former allows the reference voltage of all inverters to be in synchronism and the latter keeps the reference voltage in synchronism even during a grid power outage. There is a PLL algorithm in each Voltage Source Inverter (VSI), which ensures the synchronism between the internal reference and external signal received from the grid or from the CAN. The proposed networked control system was verified in three 5 kVA three-phase VSIs operating in parallel. Experimental results with static and dynamic tests and with electrical grid interruption and return, were obtained. The networked control system is redundant and it provides increased reliability, thus it can be applied in the parallel operation of an on-line Uninterruptible Power Supply (UPS).

Quadratic Boost-Flyback DC-DC Converter With Coupled Inductors

Abstract: A high-gain dc-dc converter, which integrates a quadratic boost flyback converter through coupled inductors is proposed in this paper. The integration generates a converter with high-gain using only one switch. The structure allows using the energy stored in the leakage inductance of the first coupled inductor on the load. Enabling this converter can be used in renewable energy systems, small wind turbines, compressed air systems, among others. The works contributes with a detailed analysis of the topology considering the leakage and the magnetizing of the coupled inductors. To validate the study, the numerical simulations were performed, as well as the tests in an experimental platform. The results, both theoretical and experimental, are in agreement which corroborates the proposed topology and the developed analysis. Thus, the converter shows up with great potential for the industrial sector.

Analysis of Self-sharing of Currents in Steady-state of IPOP Connected Modular SEPIC Converter in DCM

Abstract: This paper covers the analysis of a modular association of dc-dc SEPIC converter with parallel-parallel configuration, operating in discontinuous conduction mode The main attribute of the proposed system is its ability to provide self-sharing of the currents on both sides of each individual converter, without current control loop, and then keeping the system in stable operation This does not occur when SEPIC converter operates in continuous conduction mode considering parametric differences among modules; in CCM, one module can take the current of other modules and process the whole power of system The proposed association of DCM SEPIC converters makes possible the use of the converter for higher power levels without increase the current and voltage stress in the components, and without the use of a current control loop, which simplifies the control system to these converters The theoretical study of self-sharing of current mechanism to SEPIC converters in DCM is included in the paper Furthermore, the association is verified by numerical simulation and experimental results, which are obtained from a converter with three modules, with 100 V input voltage, 200 V output voltage, 600 W rated power and switching frequency of 25 kHz

Analysis of Single-Phase High Power Factor SEPIC Rectifiers with Split-Capacitor Output

Abstract: The analysis of single-phase rectifier topologies with split-capacitor output suppling balanced and unbalanced loads is approached in this paper. The split-capacitor output configuration can feed loads either with full voltage or with half-value of full voltage. It also allows the use of dc-dc or dc-ac half-bridge topologies as second stage. Furthermore, rectifiers with a split-capacitor output configuration can be employed to connect ac grids (or renewable ac sources) to bipolar dc-dc grids, which are commonly used in modern microgrids. Some rectifiers, as Boost, SEPIC and Buck-Boost topologies, can supply split-capacitor output and thus they can be employed in these applications. The analysis shows that the rectifier integrated with a switched capacitor cell can equalize both output voltages even under unbalanced load condition when compared with the rectifier with voltage-doubler concept (as Vienna rectifier). This paper analyses the voltage-doubler SEPIC rectifier and SEPIC integrated to a switched capacitor cell, both operating in discontinuous conduction mode. In order to verify the performance of the converters, two prototypes were built for the following specifications: 500 W of rated power, 220 V in input voltage, 400 V in output voltage and 50 kHz at switching frequency.