Showing papers on "Flyback converter published in 2011"

A Distributed Control Strategy Based on DC Bus Signaling for Modular Photovoltaic Generation Systems With Battery Energy Storage

Abstract: Modular generation system, which consists of modular power conditioning converters, is an effective solution to integrate renewable energy sources with conventional utility grid to improve reliability and efficiency, especially for photovoltaic generation. A distributed control strategy based on improved dc bus signaling is proposed for a modular photovoltaic (PV) generation system with battery energy storage elements. In this paper, the modular PV generation system is composed of three modular dc/dc converters for PV arrays, two grid-connected dc/ac converters, and one dc/dc converter for battery charging/discharging and local loads, which is available of either grid-connected operation or islanding operation. By using the proposed control strategy, the operations of a modular PV generation system are categorized into four modes: islanding with battery discharging, grid-connected rectification, grid-connected inversion, and islanding with constant voltage (CV) generation. The power balance of the system under extreme conditions such as the islanding operation with a full-charged battery is taken into account in this control strategy. The dc bus voltage level is employed as an information carrier to distinguish different modes and determine mode switching. Control methods of modular dc/dc converters, battery converter, and grid-connected converter are addressed. An autonomous control method for modular dc/dc converters is proposed to realize smooth switching between CV operation and maximum power point tracking operation, which enables the dc bus voltage regulation capability of modular dc/dc converters. Seamless switching of a battery converter between charging and discharging and that of a grid-connected converter between rectification and inversion are ensured by the proposed control methods. Experiments verify the practical feasibility and the effectiveness of the proposed control strategies.

Review of Three-Phase PWM AC–AC Converter Topologies

Abstract: This paper presents first an overview of the well-known voltage and current dc-link converter topologies used to implement a three-phase PWM ac-ac converter system. Starting from the voltage source inverter and the current source rectifier, the basics of space vector modulation are summarized. Based on that, the topology of the indirect matrix converter (IMC) and its modulation are gradually developed from a voltage dc-link back-to-back converter by omitting the dc-link capacitor. In the next step, the topology of the conventional (direct) matrix converter (CMC) is introduced, and the relationship between the IMC and the CMCs is discussed in a figurative manner by investigating the switching states. Subsequently, three-phase ac-ac buck-type chopper circuits are considered as a special case of matrix converters (MCs), and a summary of extended MC topologies is provided, including three-level and hybrid MCs. Therewith, a common knowledge basis of the individual converter topologies is established.

Quasi-Z-Source-Based Isolated DC/DC Converters for Distributed Power Generation

Abstract: This paper presents new step-up dc/dc converter topologies intended for distributed power generation systems. The topologies contain a voltage-fed quasi-Z-source inverter with continuous input current on the primary side, a single-phase isolation transformer, and a voltage doubler rectifier (VDR). To increase the power density of the converter, a three-phase auxiliary ac link (a three-phase inverter and a three-phase isolation transformer) and a three-phase VDR are proposed to be implemented. This paper describes the operation principles of the proposed topologies and analyzes the theoretical and experimental results.

A Cascaded High Step-Up DC–DC Converter With Single Switch for Microsource Applications

Abstract: This paper proposes a new high step-up dc-dc converter designed especially for regulating the dc interface between various microsources and a dc-ac inverter to electricity grid. The figuration of the proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280-W prototype sample is implemented with an input voltage range of 20-40 V and an output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high-line input; on the other hand, the full-load efficiency remains at 89.3% during low-line input.

A High-Efficiency PV Module-Integrated DC/DC Converter for PV Energy Harvest in FREEDM Systems

Abstract: The future renewable electric energy delivery and management (FREEDM) system provides a dc interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a dc/dc converter to the FREEDM system's dc bus. The module-integrated converter (MIC) topology is a good candidate for a PV converter designed to work with the FREEDM system. This paper compares the parallel connected dc MIC structure with its counterpart, the series connected MIC architecture. From the presented analysis, the parallel connected architecture was shown to have more advantages. In this paper, a high-efficiency dual mode resonant converter topology is proposed for parallel connected dc MICs. This new resonant converter topology can change resonant modes adaptively depending on the panel operation conditions. The converter achieves zero-voltage switching for primary-side switches and zero-current switching for secondary-side diodes for both resonant modes. The circulation energy is minimized particularly for 5-50% of the rated power level. Thus, the converter can maintain a high efficiency for a wide input range at different output power levels. This study explains the operation principle of the proposed converter and presents a dc gain analysis based on the fundamental harmonic analysis method. A 240-W prototype with an embedded maximum power point tracking controller was built to evaluate the performance of the proposed converter. The prototype's maximum efficiency reaches 96.5% and an efficiency increase of more than 10% under light load conditions is shown when compared with a conventional LLC resonant converter.

A New Topology of Cascaded Multilevel Converters With Reduced Number of Components for High-Voltage Applications

Abstract: In this paper, a new topology of a cascaded multilevel converter is proposed. The proposed topology is based on a cascaded connection of single-phase submultilevel converter units and full-bridge converters. Compared to the conventional multilevel converter, the number of dc voltage sources, switches, installation area, and converter cost is significantly reduced as the number of voltage steps increases. In order to calculate the magnitudes of the required dc voltage sources, three methods are proposed. Then, the structure of the proposed topology is optimized in order to utilize a minimum number of switches and dc voltage sources, and produce a high number of output voltage steps. The operation and performance of the proposed multilevel converter is verified by simulation results and compared with experimental results of a single-phase 49-level converter, too.

An Efficient High-Step-Up Interleaved DC–DC Converter With a Common Active Clamp

Abstract: This paper presents a high-efficiency and high-step-up nonisolated interleaved dc-dc converter with a common active-clamp circuit. In the presented converter, the coupled-inductor boost converters are interleaved. A boost converter is used to clamp the voltage stresses of all the switches in the interleaved converters, caused by the leakage inductances present in the practical coupled inductors, to a low voltage level. The leakage energies of the interleaved converters are collected in a clamp capacitor and recycled to the output by the clamp boost converter. The proposed converter achieves high efficiency because of the recycling of the leakage energies, reduction of the switch voltage stress, mitigation of the output diode's reverse recovery problem, and interleaving of the converters. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.

Using LLC Resonant Converter for Designing Wide-Range Voltage Source

Abstract: LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source. Large resonant inductance increases output voltage adjustment range and conversion efficiency, particularly at light loads. Soft switching is achieved for all power devices under all operating conditions by choosing the dead time and maximum switching frequency properly and operating in the converter's inductive region. Using a power-factor-correction (PFC) converter reduces the resonant converter's output voltage dependence to the variations of the main ac input voltage. Thus, the compensation of the load variations and the wide-range adjustment of the regulated output voltage can be achieved by using small switching frequency variations. The proposed method has been used to implement an adjustable wide-range voltage source (35-165 V dc), as an ion implanter arc power supply. An almost flat efficiency curve with maximum value of 94% has been achieved for the converter. Its output current can change from no load to 3 A dc.

An Isolated DC/DC Converter Using High-Frequency Unregulated $LLC$ Resonant Converter for Fuel Cell Applications

Abstract: This paper suggests an isolated dc/dc converter using an unregulated LLC converter for fuel cell applications. The LLC converter operates as an isolated voltage amplifier with a constant voltage gain, and a nonisolated converter installed in the input stage regulates the output voltage under a wide variation of fuel cell stack voltage. By separating the functions, the unregulated LLC converter can be operated at an optimal switching condition, and the high-frequency operation of 300 kHz can be accomplished without introducing an excessive switching loss. The prototype converter with a 1-kW design (Vin = 24 ~ 48 V/Vo = 400 V) shows an efficiency of above 90.2% under a 24-V input and full load conditions.

Novel High Step-Up DC–DC Converter With Coupled-Inductor and Voltage-Doubler Circuits

Abstract: In this paper, a novel high step-up dc-dc converter with coupled-inductor and voltage-doubler circuits is proposed. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switches. Also, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output. The operating principles and the steady-state analyses of the proposed converter are discussed in detail. Finally, a prototype circuit of the proposed converter is implemented in the laboratory to verify the performance of the proposed converter.

Switched-coupled inductor cell for DC-DC converters with very large conversion ratio

Abstract: By replacing the inductor in basic converters by a coupled-inductor, and adding one diode, new converters with a small count of elements and a high conversion ratio are obtained. The additional diode helps to circulate the leakage inductance energy to the load in a non-oscillatory manner. This diode conducts for a short period of time. The transistor turns on/off with soft-switching. The diodes turn on with zero-voltage switching and turn off with zero-current-switching, their reverse-recovery problem is alleviated. A switching-coupled inductor boost converter is studied in detail, and a family of DC-DC converters (boost, buck-boost, C-uk, Sepic, Zeta) based on the new switching cell is then presented. The dependence of the voltage gain on the magnetic-coupling coefficient and turns ratio of the coupled inductor is studied. The influence of the load value on the voltage conversion ratio is discussed based on an exact analysis, which avoids assumptions of ideal elements. Computer simulation and experimental results confirmed the theoretical expectations.

A Universal-Input Single-Stag2e High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck–Flyback Converter

Abstract: Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck-flyback converter (IBFC) developed in previous works. In this application, the converter is used to provide power-factor correction from a universal ac source. A control loop using the LM3524 IC has been implemented for testing the feasibility of Enabling pulsewidth modulation dimming mode. First, the LED load has been linearized and modeled in order to calculate the IBFC topology properly. Second, the converter has been designed and tested at the laboratory. The converter has also been modeled in order to design a fixed-frequency constant-current control. The dynamics of all the stages involved in the closed loop have been taken into account in order to develop an adequate controller. Finally, the experimental results obtained from the laboratory tests are discussed.

Nonisolated High Step-Up Stacked Converter Based on Boost-Integrated Isolated Converter

Abstract: To obtain a high step-up gain with high efficiency in nonisolated applications, a high step-up technique based on isolated-type converters is introduced in this paper. By stacking the secondary side of an isolated converter in addition to its primary side, a high step-up conversion ratio and a distributed voltage stress can be achieved. Moreover, a careful choice of an isolated converter can provide zero-voltage switching, continuous input current, and reduced reverse recovery on diodes. Based on a conventional voltage-doubler-rectifier boost-integrated half-bridge converter, the derived converter satisfies all these features, which make it suitable for high step-up applications. The operational principle and characteristics of the proposed converter are presented, and verified experimentally with a 135-W, 24-V input, 250-V output prototype converter for a LED driver.

Analysis, design and experimental results of a floating-output interleaved-input boost-derived DC-DC high-gain transformer-less converter

Abstract: In transformer-less energy systems sourced from low and unregulated voltage generated by a fuel cell or photovoltaic source, the voltage gain of the power electronic conditioning stage is required to be as high as possible. Although component parasitic elements limit the practically realisable voltage gain of any converter topology, this becomes a critical issue in the case of the basic step-up converter. In this study, a high-gain interleaved boost-derived converter topology is discussed. The proposed converter topology offers modularity, lower ripple for both input current and output voltage, and lower voltage and current ratings of the various circuit elements when compared to the basic boost converter. Analysis, design and key converter waveforms operating in the continuous conduction mode are provided along with design guidelines. Experimental results taken from a 1 kW laboratory prototype operating at 60 kHz are presented to confirm the validity of the analysis and design considerations.

VSC MTDC systems with a distributed DC voltage control - A power flow approach

Abstract: In this paper, a power flow model is presented to include a DC voltage droop control or distributed DC slack bus in a Multi-terminal Voltage Source Converter High Voltage Direct Current (VSC MTDC) grid. The available VSC MTDC models are often based on the extension of existing point-to-point connections and use a single DC slack bus that adapts its active power injection to control the DC voltage. A distributed DC voltage control has significant advantages over its concentrated slack bus counterpart, since a numbers of converters can jointly control the DC system voltage. After a fault, a voltage droop controlled DC grid converges to a new working point, which impacts the power flows in both the DC grid and the underlying AC grids. Whereas current day research is focussing on the dynamic behaviour of such a system, this paper introduces a power flow model to study the steady-state change of the combined AC/DC system as a result of faults and transients in the DC grid. The model allows to incorporate DC grids in a N-1 contingency analysis, thereby including the effects of a distributed voltage control on the power flows in both the AC and DC systems.

Isolated Buck–Boost DC/DC Converters Suitable for Wide Input-Voltage Range

Abstract: A family of isolated buck-boost dc/dc converter for wide input-voltage range is proposed in this paper, and the full-bridge (FB) boost converter, being one of the typical topologies, is analyzed. Due to the existence of the resonant inductor (including the leakage inductor), the FB-boost converter can only adopt the two-edge-modulation (TEM) scheme with the FB cell being leading-edge modulated and the boost cell being trailing-edge modulated to minimize the inductor current ripple over the input-voltage range, and a phase-shift-control-scheme-based TEM with the use of the market available controller IC such as UC3895 is proposed, which realizes phase-shifted control for the FB cell to achieve zero-voltage switching. In order to improve the reliability and efficiency of the FB-boost converter, a three-mode dual-frequency control scheme is proposed, in which the FB-boost converter operates in boost, FB-boost and FB modes in low, medium and high input voltage regions, respectively, and for which the expression of the inductor current ripple is derived in this paper. As the input voltage in the FB-boost mode is close to the output voltage, the inductor current ripple in this mode is much smaller than that in the other modes, and the switching frequency of the boost cell in this mode can be lowered to one-(2N+1)th of the preset switching frequency to reduce the switching loss, and hence, to improve the efficiency. A 250-500 V input, 360 V output, and 6 kW rated power prototype is fabricated to verify the effectiveness of the design and control method. The average efficiency over the input-voltage range is 96.5%, and the highest efficiency attained is 97.2%.

A new modular multilevel converter with integrated energy storage

Abstract: This paper introduces a new modular converter with integrated energy storage based on the cascaded half-bridge modular multilevel converter with common DC bus. It represents a complete modular solution with power electronics and energy storage building blocks, for medium and high voltage applications. Furthermore, this solution can interconnect a DC and AC grid with bidirectional power flow, where both of them can receive or generate excess power to the third source integrated in each converter sub-module. This particularity enables the converter usage as a high voltage UPS system in the future HVDC meshed grids. Its functionality and flexibility makes the converter independent on the energy storage unit characteristic. The converter concept with its basic functions and control schemes are described and evaluated in this paper.

A Noninverting Buck–Boost DC–DC Switching Converter With High Efficiency and Wide Bandwidth

Abstract: A novel dc-dc switching converter consisting of a boost stage cascaded with a buck converter with their coils magnetically coupled is presented. The disclosed converter has the same step-up or step-down voltage conversion properties than the single inductor noninverting buck-boost converter but exhibits nonpulsating I/O currents. The converter control-to-output transfer function is continuous between operation modes if a particular magnetic coupling is selected. The addition of a damping network improves the dynamics and results in a control-to-output transfer function that has, even in boost mode, two dominant complex poles without right-half-plane zeros. An example shows that an output voltage controller can be designed with the same well-known techniques usually applied to the second-order buck regulator. Details of a prototype and experimental results including efficiency, frequency, and time domain responses are presented. The experimental results validate the theoretical expected advantages of the converter, namely, good efficiency, wide bandwidth, and simplicity of control design.

A Novel Single-Stage High-Power-Factor AC/DC Converter Featuring High Circuit Efficiency

Abstract: This paper proposes a novel single-stage high-power-factor ac/dc converter with symmetrical topology. The circuit topology is derived from the integration of two buck-boost power-factor-correction (PFC) converters and a full-bridge series resonant dc/dc converter. The switch-utilization factor is improved by using two active switches to serve in the PFC circuits. A high power factor at the input line is assured by operating the buck-boost converters at discontinuous conduction mode. With symmetrical operation and elaborately designed circuit parameters, zero-voltage switching on all the active power switches of the converter can be retained to achieve high circuit efficiency. The operation modes, design equations, and design steps for the circuit parameters are proposed. A prototype circuit designed for a 200-W dc output was built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results.

High efficiency high step-up DC/DC converters - a review

Abstract: The renewable energy sources such as PV modules, fuel cells or energy storage devices such as super capacitors or batteries deliver output voltage at the range of around 12 to 70 VDC. In order to connect them to the grid the voltage level should be adjusted according to the electrical network standards in the countries. First of all the voltage should be stepped up to sufficient level at which the DC/AC conversion can be performed to AC mains voltage requirements. Overall performance of the renewable energy system is then affected by the efficiency of step-up DC/DC converters, which are the key parts in the system power chain. This review is focused on high efficiency step-up DC/DC converters with high voltage gain. The differentiation is based on the presence or lack of galvanic isolation. A comparison and discussion of different DC/DC step-up topologies will be performed across number of parameters and presented in this paper.

Common-Duty-Ratio Control of Input-Series Output-Parallel Connected Phase-shift Full-Bridge DC–DC Converter Modules

Abstract: Input-series output-parallel (ISOP)-connected converters allow the use of low-voltage and low-power converter modules for high input-voltage and high-power applications. Further, the use of high-frequency, low-voltage MOSFETs, which are optimized for very low on-resistance, is enabled, resulting in lower conduction losses and higher power density. In this paper, a common-duty-ratio control scheme is proposed for an ISOP converter consisting of multiple phase-shift full-bridge (PS-FB) converter modules. The proposed control method achieves stable sharing of the input voltage and load current by applying a common duty ratio to all converter modules, without a dedicated input-voltage sharing controller. The control method is analyzed by using both a small-signal averaged model and a steady-state dc model of the ISOP converter, and it is concluded that the equal sharing of input voltage and load current among converter modules can be achieved through reducing the mismatches in various module parameters, which is practically achievable. The stability and performance of the control scheme are verified by Saber simulation and a 500 W experimental prototype consisting of two PS-FB converter modules.

High Step-Up Ratio Flyback Converter With Active Clamp and Voltage Multiplier

Abstract: In this paper, an isolated high step-up ratio dc-dc converter aimed to be used in interface systems between low-voltage renewable energy sources, such as photovoltaic panels and fuel cells and the utility grid, is presented. The converter is based on the active clamp flyback topology with a voltage multiplier at the transformer secondary side. Such configuration, while naturally clamping the rectifier diode voltages thus avoiding the use of dissipative snubber circuits, allows the reduction of the circulating current during the active clamp operation due to the resonance involving the transformer leakage inductances and the diode parasitic capacitances. Experimental results taken from a 300-W-rated prototype are reported, showing the absence of parasitic oscillations after diodes and switch transitions and high efficiency, in agreement with the theoretical expectations.

A New Current-Driven Synchronous Rectifier for Series–Parallel Resonant ( $LLC$ ) DC–DC Converter

Abstract: A new synchronous rectifier (SR) driving method is proposed using primary current sensing in this paper. Because the magnetizing current of transformer is included in the primary winding of transformer, it cannot be used to generate the driving signals of SRs directly. A current-compensating winding in current transformer (CT) is used to cancel out the magnetizing current and generate suitable driving signals for SR. Therefore, one CT is used to generate two driving signals for two SRs in LLC converter with a center-tapped rectifier. This current-driven method is simple and low cost for high-output-current dc-dc application. A 150-W dc-dc prototype using LLC half-bridge converter with the proposed SR circuit is built up to verify the theoretical analysis.

A fully-integrated 3-level DC/DC converter for nanosecond-scale DVS with fast shunt regulation

Abstract: In recent years, chip multiprocessor architectures have emerged to scale performance while staying within tight power constraints. This trend motivates per-core/block dynamic voltage and frequency scaling (DVFS) with fast voltage transition. Given the high cost and bulk of off-chip DC/DC converters to implement multiple on-chip power domains, there has been a surge of interest in on-chip converters. This paper presents the design and experimental results of a fully integrated 3-level DC/DC converter [1] that merges characteristics of both inductor-based buck [2–4] and switched-capacitor (SC) converters [5]. While off-chip buck converters show high conversion efficiency, their on-chip counterparts suffer from loss due to low quality inductors. With the help of flying capacitors, the 3-level converter requires smaller inductors than the buck converter, reducing loss and on-die area overhead. Compared to SC converters that need more complex structures to regulate higher than half the input voltage, 3-level converters can efficiently regulate the output voltage across a wide range of levels and load currents. Measured results from a 130nm CMOS test-chip prototype demonstrate nanosecond-scale voltage transition times and peak conversion efficiency of 77%.

A New Phase-Shifted Full-Bridge Converter With Maximum Duty Operation for Server Power System

Abstract: A new high-efficient phase-shifted full-bridge (PSFB) converter is proposed in this paper. The conventional PSFB converter with an external inductor and clamping diodes is widely used in server power systems due to limited voltage stress on switches and its zero-voltage switching (ZVS) characteristics. However, a hold-up time regulation rule in server systems limits its operating duty ratio in nominal state and it increases the conduction loss of the converter. With simple modification, the proposed converter can be operated in the optimal operating point, 50% duty ratio, both in nominal operating condition and hold-up time condition. The ZVS characteristic is still maintained in the proposed converter. Therefore, conduction loss at the primary side of the converter is reduced and higher efficiency can also be obtained in the proposed converter than the conventional converter. The operational principle and analysis of the proposed converter are presented and verified by the 1-kW prototype.

Optimum Injected Current Harmonics to Minimize Peak-to-Average Ratio of LED Current for Electrolytic Capacitor-Less AC–DC Drivers

Abstract: The lifetime of an ac-dc LED driver can be increased by eliminating the electrolytic capacitor. Unfortunately, it results in pulsation with twice the line frequency in the driving current. Injection of the third and fifth harmonics into the input current can reduce the peak-to-average ratio of the driving current, which is beneficial for reliable operation of the LEDs. This letter discusses the relationship between the peak-to-average ratio and the injected harmonics, and the optimum injected third and fifth harmonics to minimize the peak-to-average ratio are obtained, while ensuring that the input power factor is higher than 0.9 to meet the regulatory requirement such as the ENERGY STAR. This optimum injected current harmonics is verified by a flyback-based electrolytic capacitor-less LED driver with 25 V, 0.35 A output.

Voltage-lift-type switched-inductor cells for enhancing DC-DC boost ability: Principles and integrations in Luo converter

Abstract: The concepts of voltage-lift-type switched-inductor cells have been proposed. The proposed circuit cells can be used to improve the boost abilities of those traditional transformerless DC-DC converters. More importantly, they can be fabricated as integrated cells and inserted into all the basic converters easily. All newly developed converters are applicable to those situations where high voltage transfer gains are required. The four-order Luo converter is taken as an example and integrated with the proposed switched-inductor cells. Both continuous conduction mode and discontinuous conduction mode operations are analysed. All theoretical results are supported by the corresponding simulation and experimental results.

A Bridgeless Single-Stage Half-Bridge AC/DC Converter

Abstract: This paper proposes a new bridgeless single-stage half-bridge ac-dc converter for power factor correction. The proposed converter integrates the bridgeless boost rectifier with the asymmetrical pulse-width modulation half-bridge dc-dc converter. The proposed converter provides an isolated dc output voltage without using any full-bridge diode rectifier. Conduction losses are lowered by eliminating the full-bridge diode rectifier. Zero-voltage switching of the power switches reduces the switching power losses. The proposed converter gives a high efficiency, high power factor, and low cost. The effectiveness of the proposed converter is verified on a 250 W (48 V/5.2 A) experimental prototype. The proposed converter achieves a high efficiency of 93.0% and an almost unity power factor for 250 W output power at 90 Vrms line voltage.

A versatile DC-DC converter for energy collection and distribution using the Modular Multilevel Converter

Abstract: The drawbacks of conventional Modular Multilevel Converters (MMC) are described in terms of short-circuits The configuration of MMC-transformer-MMC proves to handle short-circuits at the input and output without the need for additional DC or AC circuit breakers for protection The transformer can be operated with a higher frequency, reducing therefore the size of the transformer and the capacitors considerably A multitude of input and output configurations are possible, AC/AC, AC/DC and DC/DC In particular a DC/DC structure is analysed, serving as DC circuit breaker and voltage elevation interface at the same time The control strategy of the DC/DC converter is described and an experimental prototype validates the proposed structure and control