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This article presents a method for generating a family of transformerless inverters with common ground, for the connection of photovoltaic or battery energy storage systems with the electrical grid. Using the proposed method, four common-ground buck type inverter topologies are derived from bidirectional dc–dc converters based on buck–boost, SEPIC, zeta and boost–buck converters, which have in common the static gain given by ${D \mathord{/ {\vphantom {D {(1 - D)}}} } {(1 - D)}}$. The operation of each generated topology is explained and confirmed by computer simulation results. A comparative analysis between the four generated topologies and other transformerless common-ground inverters are included, considering the number of components, voltage ratings, output power, switching frequency, reported efficiency at rated power, and the requirement for filter insertion. Experimental results obtained in the laboratory, with tests performed on a nonoptimized experimental prototype are presented, for the topology based on the bidirectional zeta converter. [ABSTRACT FROM AUTHOR]

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 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]

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 Vrms to 1600 Vdc 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. [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 the analysis and design of a three-phase high power factor rectifier, based on the dc–dc single-ended primary-inductance converter (SEPIC) operating in discontinuous conduction mode, with output voltage regulation and high frequency isolation. The input high power factor is naturally attained through the operational mode without the use of current sensors and a current control loop. To validate the theoretical analysis, a design example and experimental results for a 4-kW, 380-V line-to-line input voltage, 400-V output voltage, 0.998 power factor, 40-kHz switching frequency, and 4% input current total harmonic distortion laboratory prototype are presented, considering two distinct modulators. In addition, experimental results for the output voltage closed-loop control are presented. [ABSTRACT FROM AUTHOR]

In this paper a step-up/step-down isolated dc–dc converter referred to as a three-phase flyback push–pull dc–dc converter is presented. The power circuit is constituted by a pair of coupled inductors, a three-phase transformer, a capacitor, three switching transistors and three power diodes. The proposed converter offers the advantages of compact passive devices, low conduction power losses, full duty cycle range (0–100%), and inherent protection against transformer saturation. Furthermore, filter sizes are minimized to duty cycles of around 1/3 and 2/3. These characteristics makes this converter suitable for many applications, especially in low-voltage high-power applications such as telecommunications power supply, battery chargers, and renewable power systems. The operating principle and the idealized mathematical analysis in continuous conduction mode are presented. Experimental data were obtained from a laboratory prototype with an input voltage of 125 V, output voltage of 100 V, load power of 1000 W, and switching frequency of 42 kHz. The measured prototype efficiency was 94% for full load and 96% for 400 W. [ABSTRACT FROM AUTHOR]

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 proposes an isolated three-phase rectifier power-factor correction using two single-phase buck preregulators in continuous conduction mode. The use of the Scott transformer renders a simple and robust rectifier to operate with unity power factor. With only two active switches, the rectifier is able to generate symmetrical currents in the line and a regulated voltage output without any necessary synchronous switches. The proposed control technique with sinusoidal pulse width modulation uses a feedforward of the output inductor current and only one voltage control regulates the output. Complete simulation results under closed-loop operation are given and a 12-kW prototype has been implemented in the laboratory, which demonstrated to operate successfully with excellent performance, and thus can feasibly be implemented in higher power applications. [ABSTRACT FROM AUTHOR]

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]

A three-phase dc–dc converter based on the three-phase neutral point clamped (NPC) commutation cell is proposed, which is intended for use in applications where the energy from a medium dc bus voltage needs to be processed. In this paper, all six continuous conduction modes (CCMs) are described, presenting the main waveforms and equations. For the discontinuous conduction modes the main equations are also provided for a complete converter characterization. Experimental results for a 10 kW, 800 V input voltage, 200 V output voltage, 91% efficiency, 40 kHz laboratory prototype are also presented to verify the theoretical analysis carried out. [ABSTRACT FROM AUTHOR]

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]

This paper presents the concepts for application of space vector modulation to two-level unidirectional pulsewidth modulation (PWM) rectifiers, and a methodology for the use of this modulation is proposed and applied in three different groups of rectifiers. For each group of rectifiers, the converter switching stages are analyzed to determine switch control signals for space vector modulation. One switching sequence is proposed for all rectifiers in order to minimize the number of switch commutations and reduce the switching losses. Duty cycle functions are determined, and the desired switching sequences are performed by a simple PWM, without the need to determine the present sector of the vector. For this purpose, it is necessary to impose the desired current sectors from input voltage references only. In order to validate the proposed modulation techniques, simulation and experimental results are presented for a 20-kW prototype. [ABSTRACT FROM AUTHOR]

This paper describes the conception and analysis of a unidirectional hybrid three-phase rectifier suitable for medium- and high-power applications. The rectifier is composed of a single-switch diode bridge boost-type rectifier in parallel with a pulsewidth modulation (PWM) three-phase unidirectional boost rectifier. The objective is to obtain a structure capable of providing sinusoidal input currents with low harmonic distortion and dc output voltage regulation. The diode rectifier operates at low frequency and has a higher output power rating. Therefore, the PWM unidirectional rectifier is designed to operate with a small power rating and at a high switching frequency. The total harmonic distortion of the proposed structure varies between 0% and 32%, depending only on the amount of power processed by the PWM three-phase unidirectional rectifier. The rectifier topology conception, principle of operation, control scheme, and simulation and experimental results of a 20-kW laboratory prototype are also presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a new three-phase current-fed push-pull dc-dc converter is proposed. This converter uses a high-frequency three-phase transformer that provides galvanic isolation between the power source and the load. The three active switches are connected to the same reference, which simplifies the gate drive circuitry. Reduction of the input current ripple and the output voltage ripple is achieved by means of an inductor and a capacitor, whose volumes are smaller than in equivalent single-phase topologies. The three-phase dc-dc conversion also helps in loss distribution, allowing the use of lower cost switches. These characteristics make this converter suitable for applications where low-voltage power sources are used and the associated currents are high, such as in fuel cells, photovoltaic arrays, and batteries. The theoretical analysis, a simplified design example, and the experimental results for a 1-kW prototype will be presented for two operation regions. The prototype was designed for a switching frequency of 40 kHz, an input voltage of 120 V, and an output voltage of 400 V. [ABSTRACT FROM AUTHOR]

In this work, the three-phase rectifier with a new connection is presented. The use of the Scott transformer makes a split dc-bus voltage possible and the rectifier operates with unity power factor. Using only two active switches, the rectifier is able to generate symmetrical currents in the line and a balanced split dc-bus output voltage, which is necessary in several applications. Pulse width modulation and instantaneous average current control are used. There are two voltage controls that regulate the output voltage and the split dc-bus voltage. Complete simulation results under closed loop operation are given, as well as results of an experimental setup. [ABSTRACT FROM AUTHOR]

This work presents a methodology to apply space vector modulation to a three-phase three-switch two-level V-connected unidirectional pulsewidth modulation (PWM) rectifier. Converter switching stages are analyzed to determine switch control signals for space vector modulation. A switching sequence is proposed in order to minimize the number of switch commutations and to reduce the switching losses. Duty cycle functions are determined and the desired switching sequences are performed by a simple PWM modulator with no need of to determine the present sector of vector. For this propose is just necessary to impose the desired current sectors from input voltage references. The vector control structure used with the proposed modulation technique is also described. In order to validate the proposed modulation technique, experimental results are presented for a 20 kW prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a series active filter using a simple control technique. The series active filter is applied as a controlled voltage source contrary to its common usage as variable impedance. It reduces the terminal harmonic voltages, supplying linear or even nonlinear loads with a good quality voltage wave- form. The operation principle, control strategy, and theoretical analysis of the active filter are presented. These aspects were proven by the results of numerical simulations. Experimental results of the series active filter demonstrated its good performance under different load conditions. [ABSTRACT FROM AUTHOR]

This paper proposes the application of the asymmetrical duty cycle to the three-phase dc/dc pulse-width modulation isolated converter. Thus, soft commutation is achieved for a wide load range using the leakage inductance of the transformer and the intrinsic capacitance of the switches, as no additional semiconductor devices are needed. The resulting topology is characterized by an increase in the input current and output current frequency, by a factor of three compared to the full-bridge converter, which reduces the filters size. In addition, the rms current through the power components is lower, implying the improved thermal distribution of the losses. Besides, the three-phase transformer allows the reduction of the core size. In this paper, a mathematical analysis, the main waveforms, a design procedure, as well as simulation and experimental results obtained in a prototype of 6 kW are presented. [ABSTRACT FROM AUTHOR]

This paper proposes the use of a three-phase version of the hybridge rectifier in the three-phase zero-voltage switch (ZVS) dc/dc converter with asymmetrical duty cycle. The use of this new rectifier improves the efficiency of the converter because only three diodes are responsible for the conduction losses in the secondary side. The current in the secondary side of the transformer is half the output current. In addition to this, all the advantages of the three-phase dc/dc converter, i.e., the increased frequency of the output and input currents, the improved distribution of the losses, as well as the soft commutation for a wide load range, are preserved. Therefore, the resulting topology is capable of achieving high efficiency and high power density at high power levels. The theoretical analysis, simulation, and experimental results obtained from a 6-kW prototype, and also a comparison of the efficiency of this converter with the full-bridge rectifier are presented. [ABSTRACT FROM AUTHOR]

A new four-switch full-bridge dc-dc converter topology is especially well-suited for power converters operating from high input voltage: it imposes only half of the input voltage across each of the four switches. The two legs of a full-bridge converter are connected in series with each other, across the dc input source, instead of the usual topology in which each leg is connected across the dc source. The topology reduces turn-off switching losses by providing capacitive snubbing of the turn-off voltage transient, and eliminates capacitor-discharge turn-on losses by providing zero-voltage turn-on. (Switching losses are especially important in converters operating at high input voltage because turn-on losses are proportional to the square of the input voltage, and turn-off losses are proportional to the input voltage). The topology is suitable for resonant and nonresonant converters. It adds one bypass capacitor and one commutating inductor to the minimum-topology full-bridge converter (that inductor is already present in many present-day converters, to provide zero-voltage turn-on, or is associated with one or two capacitors to provide resonant operation), and contains a dc-blocking capacitor in series with the output transformer, primary winding, and some nonresonant converters (that capacitor is already present in resonant power converters). The paper gives a theoretical analysis, and experimental data on a 1.5-kW example that was built and tested: 600-Vdc input, 60-Vdc output at up to 25 A, and 50-kHz switching frequency. The measured performance agreed well with the theoretical predictions. The measured efficiency was 93.6% at full load, and was a maximum of 95.15% at 44.8% load. [ABSTRACT FROM AUTHOR]

A robust 12 kW rectifier with low THD in the line currents, based on an 18-pulse transformer arrangement with reduced kVA capacities followed by a high-frequency isolation stage is presented in this work. Three full-bridge (buck-based) converters are used to allow galvanic isolation and to balance the dc-link currents, without current sensing or current controller. The topology provides a regulated dc output with a very simple and well-known control strategy and natural three-phase power factor correction. The phase-shift PWM technique, with zero-voltage switching is used for the high-frequency dc-dc stage. Analytical results from Louder analysis of winding currents and the vector diagram of winding voltages are presented. Experimental results from a 12 kW prototype are shown in the paper to verify the efficiency, robustness and simplicity of the command circuitry to the proposed concept. [ABSTRACT FROM AUTHOR]

Focuses on a study that presented two alternatives for the implementation of an isolated direct current-direct current (dc/dc) converter operating with a high output voltage and supplied by an unregulated low input voltage. Background on high-voltage isolated dc-dc converters; Experimental results; Conclusion.

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.

Discusses a study that presented an improved family of direct current-to-direct (dc-to-dc) current converters in both active and passive switches. Objective of high frequency operation in dc-to-dc converters; Basic dc-to-dc converters; Topological stages of boost converter; Operation and analysis of the boost converter.

Presents a study which proposed an isolated direct current (DC)-DC converter based on two ZVS-PWM active-clamping forward converters connected in series and coupled by a single high-frequency transformer. Circuit description and principle of operation; Theoretical analysis and relevant design curves; Experimental results and conclusions.

Presents a study which examined a reversible step-up/step-down alternating current-direct current (ac-dc) converter controlled by sliding mode. Methodology; Results; Conclusions.

Deals with a study that introduced the Flying-Capacitor ZVS pulse width modulation 1.5 kilowatts direct current-to-direct current converter. Information on the circuit and principle operation of the converter; Relevant analysis results; Design procedure and example; Experimental results.

Presents information on a study which proposed a zero-voltage-switching scheme for the three-level capacitor clamping inverter. Disadvantages of the neutral-point-clamped inverter; Proposed circuit and its operation; Analysis and design; Experimental verification.

Presents a study which proposed a diode clamping inverter that works without the series association of the clamping diodes. Description of the diode clamping inverter and its operation; Clamping mechanism and auxiliary clamping of the diode clamping inverter; Experimental results; Conclusion.

Presents a study which proposed a transformer-assisted pulsewidth modulation (PWM) zero-voltage switching pole inverter. Commutation principle of the transformer-assisted PWM zero-voltage switching pole inverter; Mathematical analysis of the transformer-assisted PWM zero-voltage switching pole inverter; Conclusion of the study.

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 information on a study that introduced a flyback-current-fed push-pull direct current-direct current converter. Significant advantages of the proposed converter; Experimental results; Conclusion.

Presents information on a study which proposed a zero-voltage switching (ZVS) scheme for a three-level capacitor clamping inverter based on a true pulsewidth modulation pole. Main circuit modulation strategy and proposed ZVS topology; Theoretical analysis of the commutation process; Design methodology of the auxiliary circuit; Conclusions.

Presents information on a study which focused on a novel single-phase power-factor pulsewidth-modulated boost rectifier. Novel topology and principle of operation; Analysis of commutation; Conclusions.

Presents information on a study which examined a proposed unity power-factor rectifier based on a two-cell boost converter using parallel-connection technique. Theoretical analysis of the two-cell boost converter; Design considerations and digital simulation of the study; Experimental results.

Presents information on a study which proposed a voltage source inverter (SVI) referred to as a boost inverter or boost direct current (DC)-alternating current (AC) converter. Principle of operation; Description of a sliding mode controller for the boost inverter; Data analysis; Results.

Presents information on a study which analyzed a proposed high-power-factor three-phase alternating current (AC)-direct current (DC) converter composed of a line interphase transformer (LIT) and two three-phase rectifiers and pulsewidth modulation dc-dc boost converter. Description of the proposed circuit; Principle of operation; Data analysis; Results.

Introduces a method for the improvement of the power factor of three-phase rectifiers. Main features of the proposed circuits; Circuit description and analysis; Design and simulation using a ac-dc converter; Experimental results; Conclusions.

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.

Presents a technique to generate a complete family of two-switch pulsewidth-modulated (PWM) with active clamping dc/dc converters, featuring soft commutation of the semiconductors at zero-voltage. Main purpose of technique; Description of generation of cells; Principles of operation, theoretical analysis, simulation and experimental results of one particular converter.

Describes a novel direct current direct current (dc/dc) converter whose significant advantages includes the single power switch, single-input inductor, with focus on a flyback-current-fed push-pull topology. Features of the system; Conclusions reached.

Introduces a family of zero-voltage switching (ZVS) pulse-width modulation (PWM) active-clamping dc-to-dc boost converters. Objectives of the technique; Description of the experimental results of the clamped mode ZVS-PWM boost converter; Statistical information on the converters.

Introduces power converters, in relation to power recycling for use in burn-in test of synchronized uninterruptible power supplies (UPS's). Description on the operations; Details on the main feature of the circuits; Economical benefits; Important characteristic to follow.

Describes a technique for parallel connection of commutation cells. Use of small inductances to ensure dynamic and static share of the commutated current among the different switches; Principle of operation; Theoretical analysis and design procedure.