Demercil S. Oliveira

A three-phase ZVS PWM DC/DC converter with asymmetrical duty cycle for high power applications

This paper proposes the application of the asymmetrical duty cycle to the three-phase dc/dc pulse-width modulation isolated converter. Thus, soft commutation is achieved for a wide load range using the leakage inductance of the transformer and the intrinsic capacitance of the switches, as no additional semiconductor devices are needed. The resulting topology is characterized by an increase in the input current and output current frequency, by a factor of three compared to the full-bridge converter, which reduces the filters size. In addition, the rms current through the power components is lower, implying the improved thermal distribution of the losses. Besides, the three-phase transformer allows the reduction of the core size. In this paper, a mathematical analysis, the main waveforms, a design procedure, as well as simulation and experimental results obtained in a prototype of 6 kW are presented.

Interleaved-Boost Converter With High Voltage Gain

This paper presents an interleaved-boost converter, magnetically coupled to a voltage-doubler circuit, which provides a voltage gain far higher than that of the conventional boost topology. Besides, this converter has low-voltage stress across the switches, natural-voltage balancing between output capacitors, low-input current ripple, and magnetic components operating with the double of switching frequency. These features make this converter suitable to applications where a large voltage step-up is demanded, such as grid-connected systems based on battery storage, renewable energies, and uninterruptible power system applications. Operation principle, main equations, theoretical waveforms, control strategy, dynamic modeling, and digital implementation are provided. Experimental results are also presented validating the proposed topology.

Novel Nonisolated High-Voltage Gain DC–DC Converters Based on 3SSC and VMC

This paper introduces a new family of dc-dc converters based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. In order to verify the operation principle of this family, the boost converter is chosen and investigated in detail. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype and relevant issues are discussed. The analyzed converter can be applied in uninterruptible power supplies, fuel cell systems, and is also adequate to operate as a high-gain boost stage with cascaded inverters in renewable energy systems. Furthermore, it is suitable in cases where dc voltage step-up is demanded, such as electrical fork-lift, audio amplifiers, and many other applications.

DC–DC Nonisolated Boost Converter Based on the Three-State Switching Cell and Voltage Multiplier Cells

This work introduces a dc-dc boost converter based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype, as relevant issues are discussed. The converter can be applied to uninterruptible power supplies and is also adequate to operate as a high gain boost stage cascaded with inverters in renewable energy systems. Furthermore, it can be applied to systems that demand dc voltage step up such as electrical fork-lift, renewable energy conversion systems, and many other applications.

High-Voltage Gain Boost Converter Based on Three-State Commutation Cell for Battery Charging Using PV Panels in a Single Conversion Stage

This paper presents a novel high-voltage gain boost converter topology based on the three-state commutation cell for battery charging using PV panels and a reduced number of conversion stages. The presented converter operates in zero-voltage switching (ZVS) mode for all switches. By using the new concept of single-stage approaches, the converter can generate a dc bus with a battery bank or a photovoltaic panel array, allowing the simultaneous charge of the batteries according to the radiation level. The operation principle, design specifications, and experimental results from a 500-W prototype are presented in order to validate the proposed structure.

A three-phase ZVS PWM DC/DC converter with asymmetrical duty cycle associated with a three-phase version of the hybridge rectifier

This paper proposes the use of a three-phase version of the hybridge rectifier in the three-phase zero-voltage switch (ZVS) DC/DC converter with asymmetrical duty cycle. The use of this new rectifier improves the efficiency of the converter because only three diodes are responsible for the conduction losses in the secondary side. The current in the secondary side of the transformer is half the output current. In addition to this, all the advantages of the three-phase DC/DC converter, i.e., the increased frequency of the output and input currents, the improved distribution of the losses, as well as the soft commutation for a wide load range, are preserved. Therefore, the resulting topology is capable of achieving high efficiency and high power density at high power levels. The theoretical analysis, simulation, and experimental results obtained from a 6-kW prototype, and also a comparison of the efficiency of this converter with the full-bridge rectifier are presented.

Analysis, Design, and Experimentation of a Double Forward Converter With Soft Switching Characteristics for All Switches

The study of a topology resulting from the combination of two forward structures attached to a single transformer core is presented in this paper, as a dual active bridge converter is obtained. In order to reduce the switching losses and the electromagnetic interference, a soft commutation cell, which provides zero-voltage commutation of the main switches for the entire load range, is implemented. Besides, the auxiliary switches are zero-current turned on and zero-current, zero-voltage turned off. This converter reduces the voltage over the main switches to half of the input voltage, employing only four switches and an additional transformer winding when compared to the full-bridge converter. The analysis of the circuit is carried out, and experimental results obtained from a prototype are also presented to support the theoretical assumptions.

A two-stage AC/DC SST based on modular multilevel converterfeasible to AC railway systems

This paper proposes the use of the modular multilevel converter (MMC) for ac-dc conversion using medium frequency transformers in a two-stage topology with unidirectional switches. The losses analysis of the propose converter are presented with a comparative study among others two topology well know in the literature for traction applications. The basic description of the topology and some simulation results are presented, followed by a comparative losses result.

High voltage gain single stage DC-DC converter based on three-state commutation cell

This paper presents a high voltage gain single stage DC-DC converter based on the three-state commutation cell. The presented converter operates with soft-switching ZVS mode for all switches. The operation principle, project specifications, and experimental results from a 500W prototype are presented in order to validate the proposed structure. The results show de soft switch commutation, reduced stress and high efficiency (over 94%).

A bidirectional single stage DC-DC converter with high frequency isolation

This paper proposes a single-phase bidirectional dc-dc converter feasible to dc distributed power systems and electrical vehicles. The topology provides high frequency galvanic isolation and is able to protect the system during eventual short-circuit in the output side. The current control in the primary side is performed by the duty cycle variation of the primary bridge. It is possible to regulate the dc bus voltage even during voltage dips and short-circuits. The secondary side bridge is driven with constant duty cycle and the power flow is controlled by the variation of the phase shift angle between the two bridges. The basic equations are shown and experimental results are presented and discussed.