Three-phase Bidirectional AC-DC Research Articles

A SWISS-Rectifier-Based Single-Stage Three-Phase Bidirectional AC–DC Inductive-Power-Transfer Converter for Vehicle-to-Grid Applications

Three-phase bidirectional ac–dc inductive power transfer (IPT) systems for vehicle-to-grid applications are conventionally based on a two-stage architecture. However, poor conversion efficiency, high component counts, and high control complexity are distinct disadvantages. Even though a few single-stage ac–dc IPT systems based on matrix-type converters were proposed, it remains a challenge for achieving sinusoidal input current, zero-voltage switching, and high efficiency simultaneously. In this article, a new single-stage three-phase bidirectional ac–dc IPT converter is proposed. The proposed converter is based on a newly proposed multi-active-bridge converter coupled to a SWISS front end. As a result, the proposed converter inherits not only the merits of low distortion of input current, high efficiency, and output short-circuit protection, but also achieves soft-switching operation resulting from the proposed modulation strategy and the property of the double-sided <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> compensation network. The operating principle and mathematical analysis of the proposed converter are discussed. Experimental results are presented to verify the performance of the converter.

Critical-Conduction-Mode-Based Soft-Switching Modulation for Three-Phase PV Inverters With Reactive Power Transfer Capability

In this article, an improved critical-conduction-mode-based soft-switching modulation technique is proposed for three-phase photovoltaic (PV) inverter applications under not only the unity power factor operating condition, but also nonunity power factor operating condition in order to reduce switching loss. With the proposed improvements, for the typical power factor range from the 0.8 lagging condition to the 0.8 leading condition in PV applications, zero-voltage-switch turn- on or valley drain–source voltage turn- on is achieved, which is especially beneficial for silicon carbide (SiC)-based systems at a high switching frequency operation to achieve not only high power density but also high efficiency. The proposed modulation technique is digitally implemented with one low-cost microcontroller. The capability of reactive power transfer and benefits of the improved modulation for achieving soft switching under nonunity power factor conditions are experimentally verified on a SiC-based three-phase bidirectional ac–dc converter prototype. The tested peak efficiency is 98.9% under the unity power factor operation, and above 98.0% within the aforementioned typical power factor range in PV applications, at above 300 kHz switching frequency operation.

Critical-Mode-Based Soft-Switching Modulation for High-Frequency Three-Phase Bidirectional AC–DC Converters

In this paper, a novel critical-conduction-mode-based modulation is proposed for three-phase bidirectional ac–dc converters. With this modulation, the switching frequency variation range shrinks, zero-voltage-switch soft switching is achieved, and the switching-related loss is reduced, which is especially beneficial for systems operating above hundreds of kHz high switching frequency with wide-band-gap power semiconductor devices to achieve both high power density and high efficiency. A 25 kW silicon carbide based high-frequency three-phase bidirectional ac–dc converter prototype is designed to achieve a power density of 127 ${\text{W/in}}^{3}$ , which is at least five times higher than commercial products. All the control functions are digitally implemented with one low-cost microcontroller, and the aforementioned benefits are experimentally verified on this prototype under both inverter mode and rectifier mode operations. With the proposed soft-switching modulation, the tested peak efficiency is close to 99.0% for this prototype even at above 300 kHz high switching frequency operation.

Modelling of a Two-Stage Bidirectional AC-DC Converter using Wavelet Modulation

&lt;span lang="EN-US"&gt;In this paper, a Wavelet modulated isolated two-stage three-phase bidirectional AC-DC converter is proposed for electric vehicle (EV) charging systems. Half-bridge resonant CLLC converter is proposed due to its high efficiency, wide gain range, galvanic isolation and bidirectional power flow. Wavelet modulation technique is used for three-phase six leg AC-DC converter due to its benefits of high DC component and lower harmonic contents. The proposed two-stage converter is developed and simulated in MATLAB Simulink environment. The contribution of this paper is on the implementation and performance analysis of Wavelet modulation in bidirectional AC-DC converters. The results show that Wavelet modulation is suitable to be implemented for the proposed bidirectional converter. The performance of the proposed converter delivers very low output voltage ripple and total harmonic distortion output current of less than 10% which is within the expected results.&lt;/span&gt;

Fuzzy logic in decision support system as a simple Human/Internet of Things interface for shunt active power filter

Abstract This paper introduces a fuzzy logic (FL) based decision support system (DSS) for a three-phase bidirectional AC-DC grid converter, working in a modern grid-like smart grid or smart industry. It is assumed that the appliances connected to that grid interact as in the Internet of Things (IoT) or like in the Internet of Everything (IoE) i.e. with a human being located in the chain of data flow. A power electronics AC-DC converter, operating as a shunt active power filter (SAPF) is selected for the case study. A harmonics reduction algorithm is presented as an implementation sample of the DSS. The operation of the SAPF is described and analysed. Experimental results showing the tuning process and operation of the laboratory model are also presented and discussed. Finally, it is shown that the DSS is an elegant and intuitive interface, which can simplify a human’s or machine’s decision-making process. Thanks to the DSS, the meaning of transferred data is translated into linguistic variables that can be understood by non-experts. Hence, it is expected that the amount of transferred data in the smart grid and in the IoE would be reduced. But in the same time, the high quality of the controlled process is retained, as shown by the example of a conventional SAPF.

A Three-Phase Bidirectional ACDC Converter with Y-Δ Connected Transformers

This paper proposes a three-phase bidirectional ac/dc converter with Y–Δ connected transformers. The converter achieves both buck-boost ac/dc bidirectional conversion and electrical isolation with the single-stage structure. By introducing three dc–dc transformers, the total power is distributed and the current stress of the rectifier stage decreases. The Y–Δ connected transformers provide extra step-down conversion ratio and facilitate the converters’ application in buck conversion. The circuit derivation, operation principles, and control strategy with the SVPWM algorithm are presented. A 3-kW prototype with 380-V dc and a 1.6-kW prototype with 48-V dc were built in the lab and experimental results verify the theoretical analysis well.

PWM ASIC design for the three-phase bi-directional buck converter

The design of hardware and software generation of the synchronous pulse-width modulation (PWM) suitable for the three-phase bi-directional AC-DC power converter is presented. The switching of the power devices is modulated by synchronous PWM implemented in an XC-3042 field programmable gate array (FPGA). There are no mains capture and synchronization problems. The utilization of the switches is based on the voltage space vector control of an inverter. Displacement factor control is achieved in the design by decrement and increment of the phase-shift counter to give leading or lagging phase angle respectively. Results are provided to demonstrate the effectiveness of the design.