Switched-capacitor Principle Research Articles

A novel switched capacitor-based multilevel inverter structure for renewable energy conversion system

Switched capacitor multilevel inverters (SCMLIs) are one of the popular solutions to mitigate the different limitations of conventional multilevel inverters (MLIs). A large number of innovative SCMLIs have been reported in literature in recent years. However, the large requirement of power switches, capacitors and large voltage stress across the switching devices are the major limitations of SCMLIs. In this paper, a novel MLI structure using switched capacitor principle has been proposed. It does not require any H-bridge circuit which reduces the switch voltage stress of the structure. It has the ability to produce 13-level output voltage with a boosting factor of 2. Further, the cascaded arrangement of the proposed structure has been realised. The structure requires a lower number of components as compared to the other SCMLIs. The operating principle, capacitor selection procedure and power losses analysis of the proposed 13-level structure have been presented. Extensive simulation and experimental studies have been conducted to validate the effectiveness of the proposed structure.

A Family of DC–DC Converters With High Step-Down Voltage Capability Based on the Valley-Fill Switched Capacitor Principle

In this article, a family of interleaved high-step-down dc-dc converters is proposed integrating the valley-fill switched capacitor structure and a double-series capacitor Buck converter. This integration generates three converters, which will be extensively explored herein via theoretical and experimental analysis. A complete theoretical analysis of the structures is presented in order to mathematically explain the physical operation of the proposed topologies. A design procedure is presented for the following specifications: 300 V/12 V input to output voltage, 100 W of power and a switching frequency of 100 kHz, and the results obtained are compared to state-of-the-art dc-dc converters that enable similar high-step-down operation.

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

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 Three-Phase AC–AC Converter in Open-Delta Connection Based on Switched Capacitor Principle

This paper proposes a new topology for a three-phase open-delta connection ac–ac converter based on the switched capacitor principle. The topology employs only capacitors and switches in the power stage, which can provide high efficiency and power density. It operates in open loop with constant values for the gain, duty cycle, and frequency. The converter is bidirectional and thus it can step-down or step-up the output voltages. A 3.5-kW prototype was built, tested and used to verify the theoretical analysis for resistive, inductive, and nonlinear loads. The efficiency of the topology is around 93% in nominal load and the power density is 1.178 kW/kg.

A Family of High-Voltage Gain Single-Phase Hybrid Switched-Capacitor PFC Rectifiers

This paper presents the derivation, the analysis, and the experimentation of a family of unidirectional three-level PFC rectifiers, based on pulse-width-modulated hybrid switched capacitor principle. The topologies feature reduced voltage stress across the switches, low number of switches, control of the output voltage, and high-voltage gain without the utilization of transformers. Experimental results for a laboratory prototype of 220 ${\bf V}_{{\bf rms}}$ to 1600 ${\bf V}_{{\bf dc}}$ voltages and nominal power of 2500 W are included in the paper, to validate the theoretical analysis, where the measured maximum efficiency reached 97.91%. The proposed converters are suitable for applications that require rectification with unity power factor and high-voltage gain.

A Switched-Capacitor Three-Phase AC–AC Converter

This paper proposes a bidirectional three-phase direct ac–ac converter, with only capacitors and switches in its power circuit and with its operation based on the switched-capacitor principle. The converter presents fixed gain, it keeps the frequencies of the output and input voltages equal, and it operates in open loop with constant switching frequency and duty cycle. The main advantages of the proposed converter are the absence of magnetic elements in the power circuit, the higher efficiency, the higher power density, the higher specific power, the lower cost, and the fact that it can convert ac–ac voltages within a wide frequency range, including dc voltage. Therefore, it is suitable to replace the conventional three-phase autotransformer in industrial, commercial, and residential applications, and it can be designated as a magnetic-less three-phase solid-state autotransformer. The principle of operation, a qualitative and quantitative analysis, the design methodology, and a fabricated example are described in this paper. In order to verify the converter in the laboratory, a prototype with the following characteristics was designed and fabricated: 6 kW, 1.35 kW/kg, 380/110 V, and switching frequency of 100 kHz. The measured efficiency at rated power was 96.3%, and other relevant experimental results are reported herein.

A Switched-Capacitor AC-AC Converter for 220V/55V and 55V/220V Applications

A novel type AC-AC converter based on the switched-capacitor principle is presented. The circuit topology of the switched-capacitor converter, the principle of operation, the equivalent circuit model and an example are described in this paper. In order to demonstrate the performance of this converter in the laboratory, this paper designs a prototype of 600W, 220V high-side voltage, 55V low-side voltage and switching frequency of 50 kHz. The experimental results verify the validity of the theoretical analysis.

A 600-W Switched-Capacitor AC–AC Converter for 220 V/110 V and 110 V/220 V Applications

This letter proposes an ac-ac converter based on the switched-capacitor principle. The new topology is described, analyzed, designed, and tested in the laboratory. The converter characteristics at the frequency of the input voltage and at the switching frequency are described herein. The absence of magnetic elements and the stress voltages in all components equal to half the input voltage are the main advantages of the proposed ac-ac converter. In order to demonstrate the performance of this converter a design example and experimental results for a prototype of 600 W, 220 Vrms high-side voltage, 110 Vrms low-side voltage, and switching frequency of 50 kHz are reported herein. The maximum and nominal efficiencies obtained were 95.6% and 90.6%, respectively.