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Phase-Shifted Full Bridge (PSFB) topology in its four-diode variant is the choice with the lowest part count in applications that demand high power, high voltage, and galvanic isolation, such as in Electric Vehicle (EV) chargers. Even though the topology is prevalent in power electronics applications, no single, unified analytical model has been proposed for the design process of four-diode PSFB converters. As a result, engineers must rely on simulations and empirical results obtained from previously built converters when selecting components to properly match the DC source voltage level with the DC load voltage requirements. In this work, the authors provide a design-oriented analysis approach for obtaining the output voltage and semiconductor current values, ready for implementation in a spreadsheet- or MATLAB-type software to automate design optimization. The proposed formulas account for all the first-order nonlinear dependencies by considering the impact of each of the following eight design parameters: DC-link voltage, load resistance, phase-shift ratio, switching frequency, transformer turns ratio, magnetizing inductance, series inductance, and output inductance. The results are verified through experiments at the power level of 10 kW and the DC-link voltage level of 800 V by using a grid simulator and a SiC-based two-level Active Front End (AFE) with a DC–DC stage based on the PSFB topology. The accuracy of the output voltage formula is determined to be around 99.6% in experiments and 100.0% in simulations. Based on this exact model, an automated design procedure for high-power high-voltage SiC-based PSFB converters is developed. By providing the desired DC-link voltage, output voltage, output power, output current ripple factor, maximum temperatures, and semiconductor and heatsink databases, the algorithm calculates a set of feasible designs and points to the one with the lowest semiconductor losses, dimensions, or cost.

This paper proposes a model of a coupled inductor which takes into account the influence of frequency, temperature, and a constant component, IDC, of currents in the windings on the parameters of the considered element. A description of the model and methods of measuring parameters of the inductor using an impedance analyzer and a chamber for thermal measurements is given. The obtained results of measurements are compared with the results of calculations proving a satisfactory match.

DC microgrids are definitely one of the global trends shaping the future of the energy sector. The prospective spread of distributed power generation systems raises the need for an optimized multilayer power management control structure in DC microgrids. The main topic of the article is modular control strategy for a centralized controller in a direct-current microgrid. The paper presents four power flow management algorithms allowing microgrid to operate in autonomous mode. Control algorithms ensure DC-bus voltage ripple compensation, maximum PV power point tracking, reduction of energy storage degradation and constraints for power exchange with the electrical grid. The topology structure of the microgrid with AC/DC and DC/DC modular converters is proposed for the distributed power technology. Furthermore, a simulation model consisting of PV power generation, hybrid energy storage, low voltage grid connection and EV fast-charging station submodels are presented. Simulation results are described to validate the effectiveness of the proposed hierarchical power management control structure.

This paper presents an extended estimation of power loss in synchronous buck-boost DC/DC converter based on low voltage GaN E-HEMT power transistors. The converter is designed as a cascaded connection of buck and boost. In contrast to basic two-switch topology, it provides non-inverting voltage characteristic preserving limited usage of passive components. Due to the increased number of switches, the focus is on transistor losses. The difference between GaN E-HEMT and Si transistors is also included. Analytical calculations and simulation results are shown and compared with experimental research.

The paper describes design and construction of a high-efficiency three-phase, three-level NPC grid-tied converter made entirely in wide-bandgap semiconductor technology (HEMTs made of gallium nitride - GaN, clamping diodes made of silicon carbide - SiC). Project assumptions and results of simulation tests used for proper selection of active and passive elements are presented. Challenges of designing PCB circuits are discussed, including cooling of power semiconductors made in surface mount technology (SMT), which additionally forces a non-standard approach to construction of an effective cooling system. Preliminary experimental results, including energy efficiency tests and thermal measurements of the converter, are presented. The prototype achieves energy efficiency over 98%.

This paper presents the implementation of a thermal camera for the quantitative estimation of power losses in a high frequency planar transformer (100 kHz/ 5600 VA). The methodology is based on the observation of the transient temperature rise and determination of the power losses by means of curves representing the derivative of temperature as a function of power losses dissipated in the transformer. First, the thermal calibration characteristics had to be obtained from a simple experiment, where power losses are generated by DC current in the ferrite core and windings. Next, experimental investigations focused on the determination of the transformer power losses for a short circuit and no load, with a resistive load and with the rectifier as a load were carried out. Finally, to verify the obtained results, analytical calculations based on Dowell’s and modified Steinmetz’s equations were additionally made, which showed a good convergence. The proposed method is easy to implement and can be used as an alternative to the calorimetric method which is time-consuming and requires a complicated measurement setup.

The paper presents an analytical approach to the determination of power losses in a high-frequency transformer operating in the dual active bridge (DAB). This transformer, having two single-phase transistor bridge inverters, couples two DC circuits that significantly differ in voltages (280 V and 51 V ±20%). Power losses in the core and windings of the planar transformer 5600 VA /100 kHz were calculated taking into account changes in the value and direction of the energy flow between the coupled DC circuits. These circuits represent storage or renewable energy sources and intermediate circuits of the converters used in distributed generation systems. Calculations were performed using the Steinmetz’s and Dowell’s equations. The analytical results have been verified experimentally.

This paper contain a detailed study of high voltage Power MOSFET turn off process which occur in high frequencies applications. Presented description is based on simulation with very precious simulation model of Infineon's CoolMOS transistor (IPW60R070C6). Experimental results of MOSFET turn off power losses measurement in H-bridge inverter works with 100kHz were also presented. This results confirmed correctness of analytical description presented by the author. (Study of high voltage MOSFET turn off process in high frequency converters).

In the article the possibility of using modern methods of computer modelling in the design process of power electronic converters with control circuits was presented. As part of research a representative power electronic converter with an additional system enabling registration of selected parameters was tested. Next, identification of the laboratory model and verification of the estimated dynamic models was carried out, using the System Identification Toolbox from Matlab. These models can be used for simple and fast optimization of the PI controllers, which is very important in the designing of power electronics systems. The research shows a significant impact of switching frequency on identification process accuracy with delays of digital controller taken into account.

The main topic of the article is control strategies for high-frequency modular DC/DC converters, which are increasingly applied in electrical power systems, e.g. in DC microgrids and energy storage systems. The paper presents dual active bridge (DAB) modulation methods and an evaluation of their properties and implementation possibilities in high-frequency modular solutions. Furthermore, an analysis of their impact on important parameters of modular systems (such as DC-bias current in dynamic states) is discussed. Technical aspects of choosing a digital controller for these systems as well as an algorithm implementation in FPGA, that provides very good dynamic properties with minimization of DC current ripple and support for a large number of DAB modules are also presented.

This work presents concept and implementation of a bidirectional coupling between direct-current circuits of significantly different voltage levels using galvanic isolation in the form of a high-frequency transformer. Standard 5-kW/100-kHz compact dual active bridge modules were used for construction of the coupling. Possibilities of modular construction of the system were presented, in which both parallel and series-parallel connections of developed modules were analyzed. The work takes into account simulation studies of the presented solution as well as studies of an experimental model equipped with an advanced control and measurement system based on DSP-type processors. Modular construction of the converter ensures simple configuring depending on the application, increased reliability and reduced design and maintenance costs.

This paper presents an analysis of the power transfer between two DC circuit by use a single phase galvanically isolated dual active bridge - DAB. The analytical description of instantaneous values of the currents in both DC and in AC circuits of the DAB is done. The influence of the dead time as well as voltage drops across the transistors and diodes of the bridges is examined. The different relations between voltages of the DC circuits coupled through DAB and various phase shift ratios are considered. The analytical relations describing the average values of the currents in DC circuits are derived. These currents can be used to predict the power in both DC circuits and power losses generated in semiconductor devices of the converter. It is assumed that the voltage drops across these devices in conduction states are constant. The calculation of the transferred power as well as power losses and energy efficiency for the DAB converter power rated 5600 VA which is used to energy transfer between DC circuits 280 V and 51 V±20% is presented. The proposed relations and calculation results can be useful for preliminary evaluation of power losses generated in semiconductor devices and for design of the cooling system. Due to the high switching frequency of 100 kHz, the phase shift modulation for the control of DAB is used. To validate the theoretical investigations a few experimental results are presented.

Aside from providing voltage and current of sufficient values, a gate driver of a SiC MOSFET must also be durable enough to keep operating properly in given place of a main circuit of a converter. A high-side SiC MOSFET constitutes a challenge to being driven properly, since a high-voltage potential becomes repetitively applied at an output of the gate driver. In order to limit a resulting flow of parasitic current Cdv/dt to ground of the driver, a low-capacitance isolation must be implemented. Presented in this paper is a flyback-based gate driver, which is dedicated for driving a high-side 10-kV SiC MOSFET. Required properties of the gate driver such as high dielectric strength and low input-to-output stray capacitance were evaluated through a series of measurements. Switching voltage values and switching speeds of the driver were examined in an 800-V double pulse test with a 1.2 kV SiC MOSFET and compared with two other devices potentially capable of operating with the 10-kV SiC MOSFET.

The paper presents a description of switching energy losses in high-voltage MOSFET operating in a bridge topology. Energy losses in both hard and soft switching, as well as during switching on at light load current and in unloaded operation have been analyzed. The description has accounted for the effect of parasitic junction capacitances and the external capacitances of semiconductor elements, as well as the parasitic capacitance of the receiver. For deriving the relationships defining the MOSTET energy losses, the electric charge and energy conservation principle was used. The second part of the paper describes the results of simulation and experimental studies performed on the model of a dual active bridge with high-voltage MOSFETs. The obtained results are coincident with the theoretical calculation results, thereby confirming the correctness of the performed analysis.

This article presented the high power and high frequency isolated DC/DC converter with all Silicon Carbide semiconductor devices. Design steps and experimental results for a 20-kW 800-V 50-kHz Phase-Shifted Full Bridge DC/DC converter were discussed. Simulation study and experimental tests of the converter were provided. Particular attention was paid to the thermal issues of the converter and power losses in semiconductor and magnetic elements. The presented results of experimental measurements show the high efficiency of this system (up to 97%) in a wide output voltage range (100V-550V). This system can be used as an electric vehicle charger or a DC power supply for technological processes like welding or electroplating.