Search

The Single Input quasi‐Z‐Source Cascade Multilevel Inverter (SIqZS‐CMI) has the ability to make use of a single DC input source and to share active power among all cascaded qZS modules. This unique feature, do not present in any other quasi‐Z‐Source (qZS) multilevel inverter in the literature, is accomplished by replacing one of its Z‐impedance inductances by a coupled inductor. With this topology, it is possible to make use of a single low voltage PV string, favoring the use of small size residential rooftop systems. In addition, it simplifies the system grounding and the compliance with many Installation, Maintenance, and Safety Codes and Standards. The proposed control strategy enables high quality current injection into the grid, keeping the DC bus voltage regulation, ensuring precise power balancing with symmetric multilevel waveforms. Experimental results from a 5‐level SIqZS‐CMI prototype demonstrate the system's performance and its advantages. [ABSTRACT FROM AUTHOR]

In this study, a family of isolated boost DC-DC converters is proposed and evaluated. This family is built by the combination of an isolated current fed converter with high-voltage gain techniques. The evaluated cells are switched inductor, switched capacitors, reduced redundant power processing and a mixed of switched inductor and switched. So, the proposed family has four different isolated high step-up DC-DC converters. To evaluate this family, a comparative study of the significant features was performed. This study comprises features such as principle of operation, derivation of static voltage gain, current and voltage stress on the components, component stress factor, number of components, power losses, power density and cost. By these evaluations, the key features, limitations and restrictions of each converter were acknowledged. In this way, one can gather all the theoretical knowledge of each of the analysed converters and estimate which one will have better performance in the laboratory. To validate the theoretical analysis, four prototypes were built according to PV AC-module specifications 200 W. [ABSTRACT FROM AUTHOR]

This paper proposes the concept and the synthesis methodology of simplified zero-voltage-transition (ZVT) circuits applied to bidirectional pulsewidth modulation poles. The main goal of simplified ZVT circuits is to make possible the use of conventional modulation schemes to accomplish better converter performance and to eliminate the synchronous-switching requirements imposed by ZVT integrated multipole topologies. To derive the simplified ZVT circuits, a synthesis methodology is proposed based on the generalization of the ZVT technique, where the restrictions to achieve the zero-voltage switching for the main converter switches are identified. Thereafter, a set of simplified semiconductor switches composed by only one high-frequency switch is defined to be used in the simplified ZVT auxiliary circuits. Thus, using the proposed synthesis methodology, any simplified ZVT topology can be derived, whether or not they have appeared in a previous publication. In order to validate the proposed approach, experimental results for a three-phase ZVT inverter, employing the minimum-loss space vector modulation and operating at 1.5 kW and 20 kHz are presented. The prototype presented an efficiency of 98% at full load representing an improvement of 0.5% when compared to its hard-switched counterpart and 1.8% when compared to an integrated ZVT topology. [ABSTRACT FROM AUTHOR]

This paper proposes a design criterion for calculating the resonant auxiliary elements of zero-voltage transition dc-dc pulsewidth-modulated (PWM) converters that use a dc auxiliary voltage source. The proposed criterion is based on stored energy in resonant auxiliary elements and takes into account the influence of the auxiliary voltage source value. Using this criterion, the reactive energy can be kept at a minimum level and a reduction of the auxiliary elements current ratings is achieved, which leads to lower conduction losses and improved converter efficiency. In addition, a reduction in size of auxiliary magnetic elements can be accomplished. To illustrate the usefulness of the proposed design criterion, the paper compares results obtained from the True-PWM Zero-Voltage Switching pole boost converter designed according to the proposed criterion, and from the original design guidelines. Experimental results show an efficiency gain of about 1 % for a wide load range and 1.5% at full load. In addition, a reduction of about 52% in the auxiliary transformer volume for the implemented prototype was achieved, ensuring a reduction in overall converter size. Experimental results were obtained using a 1-kW 100-kHz laboratory prototype. [ABSTRACT FROM AUTHOR]