ABSTRACT This paper proposes an efficient LED lamp converter circuit incorporating dimming feature and multiple lamp independent control. The converter consists of a half-bridge resonant converter in series with a DC source. This converter operates at 200 kHz. Soft switching is employed with resonant power conversion. With modulation of the low frequency pulse width, the dimming feature is incorporated. The proposed configuration provides lower voltage stress for switching devices as well as lower switching losses resulting in increased efficiency. It is possible to independently control the current of each lamp. For two lamps operating in parallel with a total power of 25 W, a laboratory prototype has been designed. It can be used in residential applications. The proposed circuit is presented with detailed operation of the circuit, simulation and experimental results.

ABSTRACTThis paper proposes a novel Space Vector Pulse Width Modulation strategy extending conventional 2-D SVPWM strategies for its use in three-phase four-leg inverters. The methodology is based on the segregation of the zero sequence from any initial desired unbalance voltage set-points. In this way, the operation of the fourth leg is reserved to manage the desired homopolar component and to compensate for the inherent homopolar component provided by any 2-D SVPWM technique. This choice not only minimizes the complexity and effort to determine the location of the reference voltage space vector from a 3-D to a 2-D space but also enables to use 75% of the affordable space to synthesize voltages under a 3-D SVPWM technique. Furthermore, the proposal is compared with other four 3-D SVPWM techniques analysing the advantages in terms of execution time, memory program, simplicity and neutral to mid-point voltage quality, resulting into a really good implementing alternative compared with the major 3-D SPVWM techniques analysed. The new modulation strategy is presented in detail, and a complete set of simulations using this particular modulation strategy has been done, and the results of these simulations have been validated on a laboratory set-up using a four-leg inverter.

ABSTRACTThis paper quantifies the soft switching loss of a 1.2 kV SiC MOSFET module via a calorimetric method in a 78 kW full-bridge resonant inverter switched at approximately 200 kHz. By switching the SiC MOSFET just before the zero crossing of the current during turn-off and at perfect zero voltage during turn-on, this converter yielded an efficiency of roughly 99 %. Then, a simplified laboratory setup, including only a half-bridge series resonant inverter topology with split DC-link capacitors and an LC load, was built such that a real inverter operation was emulated, and thereby, turn-off loss was measured via an electrical method. A discrepancy of approximately 10 % is found between the two loss measurement methods, and the possible source for this difference is discussed. Furthermore, a standard double pulse test was also performed in an inductive clamped buck converter for measuring the hard switching loss. Finally, a comparison of losses obtained from the hard versus resonant topologies at the same load current was accomplished, which verifies the substantial benefits of the latter over the former. Thus, the merits of SiC MOSFETs for high frequency soft switched converters are demonstrated, which is the main contribution of this paper.

ABSTRACTThis paper presents an implementation of the voltage regulator module (VRM) DC-DC converter operating at 2 MHz using three interleaved switching cells whose outputs are magnetically coupled by monolithic intercell transformers (ICT). The innovation comes from the manufacturing of the ICTs. Spinel ferrite is sintered around two copper windings by pulsed electric current sintering (PECS), also called spark plasma sintering (SPS). The manufacturing processes are detailed in this paper, and the ICTs magnetic properties are measured. The high-frequency operation of the converter has been possible thanks to the implementation of GaN components. The power density of the converter is 15 kW/dm3.

ABSTRACTIn low power applications with isolation requirements (e.g. notebook adapters), the flyback converter is a commonly used converter topology. A key element of the flyback converter is its transformer. This paper introduces a flyback converter with a stepped air-gap transformer designed for a typical 65 W notebook adapter. Conventional flyback converters employ a transformer with a current independent (linear) magnetizing inductance. A stepped air-gap transformer, however, possesses a current dependent (nonlinear) magnetizing inductance. This current dependency can be influenced by the air-gap geometry. Thus, a stepped air-gap transformer offers the advantage of a greater design freedom. The use of a suitable designed stepped air-gap transformer enables an increase of the flyback converter efficiency. Measurements confirm a total loss reduction of up to 6.4%.Abbreviation DCM: Discontinuous conduction mode; BCM: Boundary conduction mode; FEM: Finite Element Method; rms: Root mean square; AC: Alternating current; DC: Direct current; EMC: Electromagnetic compatibility

ABSTRACTIn stand-alone power supply including a fuel cell (FC) and photovoltaic panels, DC/DC converters must meet several requirements from compactness, high voltage ratio, input current ripples reduction, high energy efficiency and reliability regarding keeping its function in case of power switch failures point of view. In this paper, a floating interleaved DC/DC boost converter has been chosen in order to meet the requirements for FC and photovoltaic applications. Despite the presence of a natural redundancy, a power switch failure may drastically reduce the reliability of the converter due to the additional stress on the electrical components. The purpose of this paper is to propose a power switch fault detection method based on Park’s vector and a management of operating degraded mode. Obtained simulation and experimental results allow demonstrating the performance of the developed fault detection method to enhance the overall reliability of the converter.

ABSTRACTThis paper proposes quadratic-like single-ended primary inductance converter (SEPIC) converter, a DC/DC converter suitable for wide-input voltage range. This circuit can be gated at higher duty ratio compared with conventional SEPIC converter, while the voltage conversion ratio is low. This feature is beneficial for high-input voltage because it prevents the controller from falling into extremely low duty ratio limitation. A prototype circuit is implemented with Pulse-Width-Modulation (PWM) control to drive the Light emitting diode (LED) strings for demonstration of the circuit application. Recent studies have advocated LEDs as efficient and durable technology for lighting applications. A stabilized output converter is required to regulate the current flowing through the LED lamp. The dimming control of the LED light output is implemented by the controller. This converter can be powered from either a 24-Vdc battery or from the universal AC input voltage (up to 360 Vdc). Such a wide-input voltage application can be found in emergency lighting in which the light is possibly powered either from battery or AC input voltages. Experimental results prove the feasibility of the circuit topology and theoretical analysis.

ABSTRACTThe Low Voltage Ride Through (LVRT) is an important requirement in fault conditions for any power system specially microgrids. When the fault occurs, the overcurrent and unbalanced voltage are yielded and these result in serious damages in inverter-based Distributed Generators (DGs) in the microgrid. To prevent this phenomenon, many types of research have been guided to limit the current in faulty conditions and to improve and balance the PCC voltage to be without any distortions. In this paper in islanded mode with reactive power injection during the fault occurrence, the LVRT method is proposed. This reactive power is injected to compensate the voltage dip and simultaneously limit the overcurrents in faulty phases. Also using this method, the faultless phases are not degraded and have no overvoltages. It is noticeable that two inverters in this paper assumed with varying droop gains and so the current and power of them must be divided relative to their droop gains both in faulty and faultless conditions. The simulation results are based on MATLAB Simulink which shows the system improvement in faulty conditions using this method.

The Modular Multilevel Converter (MMC) is a power electronic structure used for high voltage adjustable speed drives applications as well as power transmission applications and high-voltage direct current. MMC structure presents many advantages such as modularity, the absence of a high voltage DC bus and very low switching frequency. It presents also some disadvantages such as modeling complexity and control due to the large number of semiconductors to control. The objectives of this paper are to present the methodology to design a laboratory MMC converter and its control system. This methodology is based on an intensive used of real-time simulation, to develop and test the control algorithm is proposed. This MMC prototype must be as realistic as possible to a full scale MMC, with a large number of sub-modules (i.e. 640 kV on the DC side, a rated power of 1 GW and 400 sub-modules). A control hardware integrating distributed processors (one for each arm) and a master control is presented. The protocols to validate sub-modules, arms and the converter are explained.

In this paper, we present current-voltage characteristics of vertical and pseudo-vertical Diamond Schottky diodes operating up to 473 K. The functionality rate is greater than 75% for each samples. For vertical diodes, current density at 473 K reaches 488 A/cm², while it is greater than 1000 A/cm² for pseudo-vertical diodes. Under reverse bias, the leakage current is less than 10−7 A/cm² at 50 V for all functional diodes. However, the high barrier height and high non-ideality factor observed are probably caused by high charges at the Diamond/Schottky contact interface. This article emphasizes the high reproducibility of the characteristics and the functionality rate at 473 K.