Single-Phase AC–DC–AC Multilevel Converter for Grid Overvoltage Based on an H-Bridge Connected in Series to the Five-Leg Converter

2023

Circuit Theory & Apps

SummaryConventional AC–AC converters have some critical disadvantages, such as inappropriate input and output power quality features, employing snubber circuits to suppress the voltage stress on high‐frequency switches without a safe commutation method that increases the converter size and cost, confined voltage gain, and using huge passive components. This paper proposes an isolated high‐gain single‐phase AC–AC converter with variable output frequency, extended voltage gain, and a safe commutation strategy. Ten semiconductors are only employed for the proposed topology that only two switches and two diodes are operated with high‐frequency PWM signals. This new topology has noteworthy specifications like continuous input and output current, voltage isolation, extended inverting and non‐inverting buck‐boost modes, and frequency regulation. The high voltage gain has been achieved with small values for passive components in the impedance source section, reducing the volume and cost of the converter. The impedance source‐based section of the converter comprises one input inductor, two coupled inductors, and two capacitors in each converter leg. A safe commutation strategy has been designed and applied to the converter to mitigate the voltage and current stresses without extra snubber circuits. The number of semiconductors that simultaneously conduct in each state of the converter has been reduced. So, the conduction loss of the converter diminished. The achieved efficiency equals 95.5% and 93.5% in step‐down and step‐up modes, respectively, validated by an accurate power loss model and experimental analysis. An experimental prototype has been designed to confirm the performance of the suggested converter. Results confirm the theory and operation of the proposed converter.

Section: Classifications Of Ac-ac Convertersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An isolated high‐gain impedance source‐based single‐phase AC–AC converter with safe commutation and variable output frequency

2023

Circuit Theory & Apps

“…According to the equivalent circuit of Figure 6f, the voltage of inductor L 4 and magnetizing inductor L 2m are calculated by (7):…”

Section: -2) Modementioning

confidence: 99%

“…There are three popular methods for designing ac-ac power converters, as shown in Figure 1. Indirect ac-dc-ac converters are two-stage structures that involve a dc-link capacitor or impedance-source-based circuit, introduced as the first method [5][6][7][8][9][10]. The first stage is generally a front-end bidirectional current source rectifier (CSR), and the second stage is a voltage source inverter (VSI).…”

Section: Introductionmentioning

confidence: 99%

A highly efficient isolated single‐phase variable frequency AC–AC converter with flexible buck‐boost factor, inherent safe commutation, and continuous current

2022

IET Power Electronics

This paper proposes an isolated single‐phase flexible buck‐boost ac–ac converter with an adjustable output frequency and optimized semiconductors count. One power switch only operates with a high switching frequency in each half‐cycle of the input voltage, and others operate with a low switching frequency equal to the output frequency. Thanks to this feature, the converter provides high efficiency, 95.5% in step‐down mode and 91.5% in step‐up mode. The galvanic isolation between the input and output sides is also regarded for the proposed topology by employing two coupled inductors. The converter has an inherent safe commutation by utilizing a simple modulation strategy. Thus, additional snubber circuits and complex commutation strategies are no longer required. The proposed converter does not require any input filter as it operates with the continuous input current. This paper presents the operating principle of the proposed topology in detail. For this purpose, a 200‐W experimental prototype has been designed to examine the performance of the suggested converter for different operating modes and output frequencies. Results confirm the theory and operation of the proposed topology.

A single‐phase q‐source AC‐AC converter with continuous input current, safe commutation feature, and reduced bidirectional switch counts

2022

Circuit Theory & Apps

This paper proposes a single‐phase q‐source AC‐AC converter with a wide and flexible voltage gain. The converter only incorporates two bidirectional power switches. This new topology has many bold features like continuous input current, non‐inverting boost, and inverting buck modes. The high voltage gain is achieved by utilizing a coupled inductor in the converter. The converter gain is increased by the turns ratio of the coupled inductor proportionately. The proposed q‐source comprises one input inductor, one coupled inductor, and one capacitor, which are less than other competitors. In order to reduce the voltage and current stresses on power semiconductors, a safe commutation strategy for the converter is also introduced that eliminates snubber circuits. The input and output filters are no longer required due to the proposed converter specifications. So the volume and cost of the converter are decreased significantly. The achieved efficiency equals 94.5% due to utilizing the proposed optimized topology and switching strategy. In this paper, the operating principle of the converter is presented in detail. An experimental prototype has been designed to examine the performance of the suggested converter. Results confirm the theory and operation of the proposed topology.