Search

In this article, a hybrid boost switched-capacitor converter operating as an ac–ac solid-state autotransformer is presented. The topology integrates a basic inductive switching cell and a switched-capacitor ladder cell, performing a direct energy conversion with a high-gain output voltage. The theoretical analysis presents the main operational characteristics of the hybrid converter, including the voltage stresses across the devices, the equivalent average electric circuit model, and the calculation of current stresses considering the partial charging of the capacitors. A design methodology is described, focusing on the modulation technique and criteria for determining capacitors, semiconductor devices, inductor, and switching frequency. Validation was carried out based on simulation and experimental results obtained with a single-phase prototype with 55/220-V voltage conversion and 1-kVA rated power at 60 Hz. Additional tests verified the operation at different grid frequencies, loads (inductive and nonlinear), and with 14 different input–output connections. [ABSTRACT FROM AUTHOR]

A novel isolated dc–dc converter is proposed, using the T-Type topology with zero voltage switching and pulse width modulated with a capacitive output filter. It uses four switches, two of which are subjected to the input voltage, and the other two to half the input voltage. All switches commutate under zero voltage over a wide load range. The proposed converter has the following features: (a) symmetrical operation of the isolation transformer, (b) modulation by pulse width with constant frequency, (c) zero voltage switching, and (d) three-level voltage applied to the primary winding of the transformer. Theoretical analysis, design example, and experimental data for a 2 kW, 400 VDC input, 400 VDC output, and 50 kHz switching frequency laboratory prototype, working in two operating points are included in this paper. The measured efficiency was 95% at 950 W. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase multilevel power factor correction rectifier using the hybrid switched-capacitor concept is proposed. The converter is suitable for high-voltage-gain applications from conventional three-phase low-voltage sources. The three-level voltage operation reduces the weight and bulk of the magnetic devices. The main advantages of the proposed converter are low number of active switches, high voltage gain, sinusoidal currents, low voltage stress across all components, and simple control. Both steady-state and dynamic analyses are investigated. Experimental results for a 7500-W/220-V-to-1600-V laboratory prototype with maximum efficiency of 97.78% are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper introduces a new dc-ac converter with the feature that it produces an instantaneous output voltage higher or lower than the input dc voltage without an intermediate power stage or transformers. This feature is provided by using one switching cell including two switches, two diodes, one inductor, and one capacitor on each inverter leg. Validating the theoretical analysis, a prototype was designed, built, and tested for an output rated power of 1 kW, a dc input voltage of 96Vdc, and output voltage of 110 Vrms. Furthermore, the fundamental output frequency was established at 60 Hz and the switching frequency at 20 kHz. [ABSTRACT FROM AUTHOR]

This paper presents a voltage-fed three-phase push–pull dc–dc converter. The main characteristics of the proposed converter are: small volume, low weight, reduced number of components, low voltage across the power semiconductors for duty cycles less than 1/3, and input current ripple cancellation when the duty cycle is equal to 1/3. Typical applications include battery chargers, electric vehicles, and renewable energy systems. The paper presents a theoretical analysis, design example, and experimental data for a 650 W, 150-125 VDC input, 75 VDC output, and 42 kHz switching frequency laboratory prototype. The measured performance agreed well with the theoretical predictions. The measured efficiency for 125 VDC input at full load is 95%. [ABSTRACT FROM PUBLISHER]

This paper presents a new three-phase step-up dc–dc converter with a three-phase high-frequency (HF) isolation transformer in an average current-mode controlled closed loop. This converter was developed for industrial applications where the dc input voltage is lower than the output voltage, for instance, in installations fed by battery units, photovoltaic arrays, or fuel cell systems. The converter's main characteristics are reduced input ripple current, step-up voltage, HF transformer, reduced output-voltage ripple due to three-pulse output current, and the presence of only three active switches connected to the same reference, this being a main advantage of this converter. By means of a specific switch modulation, the converter allows two operational regions, each one depending upon the number of switches in overlapping conditions—if there are two switches, it is called R2 region, and if there are three switches, it is called R3 region. An average current-mode control strategy is applied to input-current and output-voltage regulation. Theoretical expressions and experimental results are presented for a 6.8-kW prototype, operating in the R2 region, and for a 3.4-kW prototype, operating in the R3 region, both in continuous conduction mode. [ABSTRACT FROM PUBLISHER]

A new three-phase multilevel dc–ac converter with four-state switching cell is presented in this paper. Initially, the power stage diagram is presented and discussed. Its main characteristics are described and the more relevant waveforms, generated by simulation, are shown. After that, the converter operation is presented and all topological states are shown. The vectorial interpretation of the load voltage is shown to all available vectors of load voltage in the new topology. Next, the operation of the converter with sinusoidal pulse width modulation is discussed and some relevant figures are presented. In the sequence, the four-state switching cell is presented and the presence of the three-phase coupled inductor to provide significant reduction in harmonic distortion is discussed. A prototype with 15-kW output power was build with switching frequency equal to 9 kHz and dc link voltage was 300 V. Finally, the related results obtained from the implemented prototype are presented and briefly discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

This paper presents a new nonisolated buck/boost-type multilevel dc–dc converter suitable for high-power and medium/high-voltage application. The main features of the proposed topology are as follows: low voltage across the semiconductors, low switching losses, and reduced volume of the output filter. The theoretical analysis is carried out for a five-level bidirectional structure of the proposed converter, operating in Buck mode. The proposed topology presents some capacitors, and their voltage must be balanced for proper operation of the converter. Thus, a capacitor voltage balancing active control using a feedforward technique is proposed and analyzed in detail. In order to validate the theoretical analysis, a prototype with 10 kW output power capability, 1.3 kV to 800 V input-to-output voltage, and 20 kHz of switching frequency was built and experimented. The results attest the advantages of the new dc–dc topology, as well as the new capacitor voltage control technique. [ABSTRACT FROM AUTHOR]

This paper proposes a new ac–ac static power converter based on the switched-capacitor (SC) principle, intended to replace the conventional autotransformer in commercial and residential applications. The principle of operation, a qualitative and quantitative analysis, the design methodology, and an example are described in this paper. The main advantages of the proposed ac–ac converter are the absence of magnetic elements, the stress voltages in all components being equal to half of the high-side voltage, the common reference between input and output voltages, the employment of a single SC leg, the ability to be bidirectional, the high efficiency, and the high power density. In order to demonstrate the performance of this converter in the laboratory, a prototype of 1-kW, 220-V rms high-side voltage, 110-Vrms low-side voltage, and switching frequency of 100 kHz was designed and fabricated. The relevant experimental results are reported herein. The maximum and rated power efficiencies obtained in the laboratory were 98% and 96%, respectively. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

Automotive embedded electronic systems have been increasing in power and complexity and, therefore, more advanced power electronic converters are necessary in these vehicles. Several dual-voltage (42 V/14 V) bidirectional converter architectures have been proposed for automotive systems in recent years. However, most of them have low efficiency or are based in series and parallel configurations with large number of semiconductors and magnetics devices. Therefore, in this paper, we propose a bidirectional high-efficiency converter with lower number of components. This converter was created by merging a switched-capacitor converter and a conventional bidirectional converter, resulting in a hybrid topology. The voltage across the semiconductors of the proposed converter is equal to half of the highest voltage source value. Furthermore, the topology is composed of only one inductor to control the power flow between the two voltage sources. To verify all the mentioned features, a prototype was implemented experimentally, reaching a maximum efficiency of 97.5%. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

The focus of this paper is the study of direct alternating-current (ac)–ac converters, beginning by buck, half-bridge, full-bridge, and push–pull converters. From the basic converters, we apply a simple methodology to make the use of switches in commercial configurations possible. Following that, eight voltage restorers supplied either on the line side or on the load side are proposed. A comparative evaluation of these topologies concerning implementation, complexity, and component effort is presented. It is notable that some of the studied topologies are known in the literature and others are new. For one of the presented topologies, the design of a 3-kVA voltage restorer is developed, and experimental results are shown, certifying the correct operation of the drive strategy used. [ABSTRACT FROM AUTHOR]