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This paper proposes a modular isolated dc–dc converter, based on the input-series and output-series association of the full-bridge PWM dc–dc converter with capacitive filter. The main attribute of the proposed architecture is its ability to provide self-balance of the input and output voltages across the individual converters, without voltage loop control scheme, both in the steady-state and transient operations. Circuit operation, theoretical analysis, and modeling are included in this paper, along with experimental results taken from a laboratory prototype with four modules, 1600-Vdc total input voltage, 1600-Vdc total output voltage, 4-kW output power, and 40-kHz switching frequency. Possible applications include high-voltage power supplies, solid-state transformers, dc current distribution systems, and renewable electric energy systems. [ABSTRACT FROM PUBLISHER]

In this paper, a ZVS-PWM three-phase current-fed push–pull dc–dc converter is proposed. When compared to single-phase topologies, the three-phase dc–dc conversion increases the power density, uses the magnetic core of the transformer more efficiently, reduces the stress on switches, and requires smaller filters since the frequency for its design is higher. The proposed converter employs an active clamping technique by connecting the primary side of the transformer to a three-phase full bridge of switches and a clamping capacitor. This circuit allows the energy from the leakage inductances to be reused, increasing the efficiency of the converter. If appropriate parameters are chosen, soft-commutation of the switches (ZVS) can also be achieved. The soft-commutation improves the efficiency even further, allows higher switching frequencies to be used, and reduces the electromagnetic interference significantly. Applications such as fuel cell systems, transportation, and uninterruptable power supplies are some examples that can benefit from the advantages presented by this converter. The theoretical analysis, a design example, and the experimental results for a prototype implementing this topology are presented. The prototype was designed to process 4 kW at full load with an input voltage of 120 V, an output voltage of 400 V, and a switching frequency of 40 kHz. [ABSTRACT FROM PUBLISHER]

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 the three-phase version of the isolated dc–dc Weinberg converter. The main characteristics of the proposed converter are as follows: small volume, low weight, reduced number of components, buck operation for a duty cycle of less than 1/3, and input and output current ripple cancellation for a duty cycle of 1/3 or 2/3. Typical applications include telecommunication, electric vehicles, renewable energy conversion systems, and batteries. This paper gives theoretical analysis, design example, and experimental data on a 735-W 120-Vdc-input 75-Vdc-output 42-kHz switching frequency laboratory prototype. The prototype performance shows good agreement with the theoretical predictions. [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]

In this paper, a modular three-phase multilevel inverter specially suited for electrical drive applications is proposed. Unlike the cascaded H-bridge inverter, this topology is based on power cells connected in cascade using two inverter legs in series. A detailed analysis of the structure and the development of design equations for the load voltage with n levels are carried out using pulsewidth-modulation phase-shifted multicarrier modulation. Simulations and experimental results for a 15-kW three-phase system, with nine voltage levels, validate the study presented. [ABSTRACT FROM AUTHOR]

Examines the structure and mechanisms of a transformer-assisted pulsewidth-modulation zero-voltage-switching neutral-point-clamped inverter. Inverter circuit configuration; Power transmission processes in the main switches; Analysis of the operation principles of the device.

Presents a single-phase unity power factor rectifier with reduced conduction losses. Principle of operation and commutation analysis; Definition of the switching frequency as a function of the duty cycle and the conduction time of metal oxide semiconductor field-effect transistor; Reduction of conduction losses by employing a single converter.

Presents a paper which discusses pulsewidth modulated (PWM) converters which feature soft commutation of semiconductors at zero current in transistors and zero voltage in rectifiers. Similar characteristics of converters and hard-switching PWM; Suitability of converters for high power applications using insulated gate bipolar transitors; Other advantages of a zero-current switching-PWM boost converter.

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 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 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]

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]

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]