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The voltage-balance mechanism is a required ability to simplify the control scheme for modular input-series and output-series ($\text{ISOS}$) connection, in spite of the fairly large number of studies, such mechanism has not been addressed clearly and satisfactory. This paper proposes a methodology, based on the converter output characteristics, to standardize the analysis of voltage-balance mechanism in steady state, which allows understanding the behavior of voltage sharing among the modules in steady state, in the presence of mismatched parameters for $\text{ISOS}$ connection of modular converters. In addition, the $\text{ISOS}$ connected modular two-switch flyback converter is presented. The intrinsic voltage-balance mechanism, even operating in continuous conduction mode, make this converter feasible, as an alternative to the predecessors modular converters. The operation and analysis of the proposed connection were corroborated, based on the experiment carried out on a laboratory prototype with three modules: ${\text{1}}, {\text{200 V}}_{\text{dc}}$ total input voltage, ${\text{1.5 kW}}$ rated power, and $\text{50 kHz}$ switching frequency. This paper is accompanied by a video demonstrating the operation, in steady state, of the laboratory prototype. [ABSTRACT FROM AUTHOR]

In this research, the study and implementation of the t-type parallel resonant dc–dc converter in high-voltage power supplies for travelling wave tube applications is presented. The proposed converter shares the benefits of the traditional full-bridge parallel resonant dc–dc converter, such as zero voltage switching on primary side switches over a wide load range, symmetric three-level voltage across the transformers primary winding, and integration of transformers leakage inductance and winding capacitance during its basic operation. However, only two switches are subjected to the input voltage, while the other two switches are subjected to half of the input voltage. Theoretical analysis, commutation analysis, and design guidelines are presented. The theoretical analysis validation and efficiency investigation are conducted through a t-type parallel resonant converter prototype, which operates with 1.5 kW and 97.12% efficiency. Hence, experimental results of a travelling wave tube power supply prototype operating with 1.5 kW of output power, 400 Vdc input, and four high output voltages, whose measurements results are Vo1=1382\,\rm {V}, Vo2=3505\,\rm {V}, Vo3= 1504\,\rm {V}, and Vo4=3338\,\rm {V}, confirm the feasibility of the proposed implementation. [ABSTRACT FROM PUBLISHER]

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]

This paper describes a theoretical and experimental study on a control strategy for the parallel operation of single-phase voltage source inverters (VSI), to be applied to uninterruptible power supply. The control system for each inverter consists of two main loops, which both use instantaneous values. The first (parallelism control) employs the feedback of the inductor current from the output filter to modify the input voltage of the same filter and, therefore, to control the power flow of each inverter to the load. Additionally, the second loop (voltage control) is responsible for controlling the output voltage of the LC filter, which coincides with the output voltage of the VSI. Due to the fact that there is no exchange of information among the VSIs regarding their operation points, it is easier to obtain redundant systems. Furthermore, the connection (or disconnection) of inverters in a parallel arrangement is carried out directly, without connection impedance, and can occur at any operation point of the system. The proposed control strategy ensures the proper sharing of the load current and avoids current circulation among the inverters during transient and steady-state operation. Moreover, its design and implementation are very simple. The control technique was verified through experimental results with a maximum load of 10 kVA supplied by three parallel-connected inverters. [ABSTRACT FROM PUBLISHER]

This paper presents a new three-phase rectifier that allows the operation as rectifier or as inverter, with the use of three conventional switching cells. This reversion of power flow can be obtained simply by the inverting two reference currents. The system is analyzed as a connection of three independent lower order subsystems, controlled by sliding regime with decentralized switching scheme. The output voltage can be lower, equal, or greater than the peak of the input voltage. The operation stages, equations, control strategy, and design of the converter are presented. Finally, experimental results are shown for operation as inverter and as rectifier. [ABSTRACT FROM AUTHOR]

This paper presents a zero-voltage (pulsewidth modulation) half-bridge inverter with active voltage clamping using only a single auxiliary switch. The structure is particularly simple and robust. It is very attractive for single-phase high-power applications. Switching losses are reduced due to implementation of the simple active snubber circuit that provides zero-voltage-switching conditions for all switches, which includes the auxiliary one. Its main features are simple modulation strategy, robustness, low weight and volume, low harmonic distortion of the output current, and high efficiency. The principle of operation for steady-state conditions, mathematical analysis, and experimental results from a laboratory prototype are presented. [ABSTRACT FROM AUTHOR]

In this paper, a modified asymmetric half-bridge (AHB) isolated converter is proposed, which does not have dc current offset in the transformer. The topology operates in the same way as the conventional half-bridge (HB), using asymmetric pulsewidth modulation with constant frequency. A voltage doubler rectifier is used in the output stage, which avoids the flow of the dc component current in the primary side of the transformer. In order to investigate the application of the proposed topology, a parallel-resonant (PR) version of the modified AHB was tested, which uses the parasitic elements of the transformer, such as the leakage inductance and the winding capacitance, to achieve zero voltage switching in the primary side switches over a wide load range. Theoretical and commutation analysis results are reported and design guidelines are presented herein. Experimental data were obtained from a parallel resonant 1-kW prototype, operating with a 50 kHz switching frequency, 400 V input voltage, and 400 V output voltage, to verify the theoretical study, and 97% efficiency was achieved. The proposed solution was also tested at high voltage, operating with a rated power of 1.8 kW, switching frequency of 50 kHz, input voltage of 400 V and series-connected output voltages, the maximum voltage being 8620 V. [ABSTRACT FROM AUTHOR]

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]

Presents a simplified sinusoidal uninterruptible power supply (UPS) system with active power factor correction. Features of the proposed UPS system; Advantage of the system; Circuit operation of the proposed UPS system.