Gabriel Tibola

Isolated Three-Phase High Power Factor Rectifier Based on the SEPIC Converter Operating in Discontinuous Conduction Mode

This paper presents the analysis and design of a three-phase high power factor rectifier, based on the dc-dc single-ended primary-inductance converter (SEPIC) operating in discontinuous conduction mode, with output voltage regulation and high frequency isolation. The input high power factor is naturally attained through the operational mode without the use of current sensors and a current control loop. To validate the theoretical analysis, a design example and experimental results for a 4-kW, 380-V line-to-line input voltage, 400-V output voltage, 0.998 power factor, 40-kHz switching frequency, and 4% input current total harmonic distortion laboratory prototype are presented, considering two distinct modulators. In addition, experimental results for the output voltage closed-loop control are presented.

A single-stage three-phase high power factor rectifier with high-frequency isolation and regulated DC-bus based on the DCM SEPIC converter

In this paper, the main concepts related to the development of a single-stage three-phase high power factor rectifier, with high-frequency isolation and regulated DC bus are described. The structure operation is presented, being based on the DC-DC SEPIC converter operating in the discontinuous conduction mode. This operational mode provides to the rectifier a high power factor feature, with sinusoidal input current, without the use of any current sensors and current loop control. A design example and simulation results are presented in order to validate the theoretical analysis.

Passive regenerative snubber cell applied to isolated DCM SEPIC converter

Isolated converter such as SEPIC has a high voltage stress in the main switch due to transformer leakage inductance. To solve this issue an active or passive clamp action is necessary. The common passive solution based on a RCD snubber is simple but impractical when the value of the leakage inductance is significant. In other hands, passive regenerative solutions generally compromise the isolation, making the search for a suitable snubber a challenge. In this paper, an effective passive regenerative snubber cell for isolated DCM SEPIC converters is presented. It is intended to improve the converter efficiency by transferring the energy stored in the transformer leakage inductance to the output. Analysis is presented in detail together with a practical design procedure. To validate the proposal, simulated and experimental results are performed for a 100 W, 100 V input and 50 V output voltage converter.

Multi-cell DC-DC converter with high step-down voltage ratio

The use of high voltage allows a power processing system to operate with low currents, improving efficiency. Nevertheless, final applications usually require low voltage inlet, which can be provided using modular multilevel converters submodules, for instance. However, every submodules gate-unit requires energy from an isolated low power auxiliary supply. Generally, this is done by using an external converter since it is not practical to directly step-down the high voltage to required levels. In this context, this paper proposes a multi-cell solution based on stacking of buck-boost converters intended to be the first non-isolated stage of an isolated high step-down voltage ratio converter. Analysis and design are presented together with experimental verification of a 200 W rated power converter with 1.5 kV to 3.0 kV input voltage range and a nominal output voltage of 350 V.

Comparison between dissipative snubber and passive regenerative snubber cells as applied to isolated DCM SEPIC converters

This paper presents the comparison between dissipative RCD and passive regenerative snubber cells for isolated SEPIC converters. The passive cell is intended to improve the converters efficiency by transferring the energy stored in the transformer leakage inductance to the converter output. The analysis for both snubbers are detailed including design guidelines. In order to validate the regenerative proposal and compare its feasibility, experimental verification is performed for both snubbers on a 100 W, 100 V input and 50 V output voltage SEPIC converter operating in DCM.

Analysis and design of a three-phase high power factor rectifier based on the SEPIC converter operating in discontinuous conduction mode

The analysis and design of a single-stage three-phase high power factor rectifier, with high-frequency isolation and regulated load voltage are detailed in this paper. The circuit operation is presented, being based on the DC-DC SEPIC converter operating in the discontinuous conduction mode. This operational mode provides to the rectifier a high input power factor feature, with sinusoidal input current, without the use of any current sensors and current control loop. The paper presents the theoretical analysis, design example and experimental results for a 4 kW, 380 V line-to-line input voltage, 400 V output voltage, 0.998 power factor, 40 kHz switching frequency and 4% input current THD laboratory prototype. The rectifier can operate in the step-up or in the step-down modes.

Passive Regenerative and Dissipative Snubber Cells for Isolated SEPIC Converters: Analysis, Design, and Comparison

An isolated converter such as SEPIC has high voltage stress on the main switch due to transformer leakage inductance. To solve this issue, active or passive clamp action is necessary. The common passive solution based on an RCD snubber is simple but impractical when the value of the leakage inductance is significant. On the other hand, passive regenerative solutions generally compromise the isolation, making the search for a suitable snubber a challenge. In this paper, an effective passive regenerative snubber cell for isolated SEPIC converters operating in DCM or CCM is presented. It is intended to improve the converter efficiency by transferring the energy stored in the transformer leakage inductance to the output. The analysis is presented in detail for DCM and extended to CCM together with a practical design procedure. In order to compare with the RCD, the analysis and design of a conventional cell are presented as well. To validate the proposal and quantify its feasibility, experimental results are performed for both dissipative and regenerative snubbers on a 100 W, 100 V, input and 50 V output voltage converter operating first in DCM and later in CCM.

Direct waveform synthesis with continuous variable level multilevel converter using extended commutation cells

The extended commutation cell is a four-port, four-switch cell that allows for bidirectional energy transport in two orthogonal directions throughout the cell. The voltage across each cell capacitor can be adjusted independently of the load, resulting in high flexibility in output levels. By placing the capacitors in (anti-) series while adjusting their voltage level a continuous waveform can be constructed. The analysis is given for a single and two-cell converter including load current correction. Additionally the waveform synthesis is simulated and experimentally verified on a 3.7 kW two-cell prototype.

Operation of single-chip MOSFET and IGBT devices after failure due to repetitive avalanche: University in collaboration with industry

This paper presents analysis of post-failure behaviour of MOSFETs and IGBTs operating in a series connected string. The aim of this experimental study is to analyse the operation of devices in case of sudden loss of controllability, leading to repetitive avalanche conditions at relatively low current and subsequent failure due to overheat. For redundant designs it is important that the devices are locked in stable conducting state after the failure and the string continue its operation.

Floating high step-down stacked dc-dc converter based on buck-boost cells

In some high power dc-dc applications, where high voltage is present, a converter with high step-down ratio is required in order to provide an isolated low power auxiliary supply. This requirement represents a challenge and many topologies are currently being researched. The analysis of a non-isolated, unidirectional, high step-down voltage-ratio converter based on a stack of buck-boost converters is demonstrated. The converter is intended to be applied as a floating non-isolated power supply, which can be connected to one or more isolated converters. A design example is detailed and validated with simulations, and experimental results for a 200 W, 2.8 kV input voltage and 350 V output voltage converter.