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In this study, a novel topology for the single-phase transformerless grid-connected inverters family is proposed. By using the series-parallel switching conversion of the integrated switched-capacitor module in a packed unit, several merits can be added to the proposed inverter, such as higher efficiency, boosting ability within a single-stage operation, and removing the leakage current problem by using the common grounding technique. In this study, a peak current controller strategy is implemented in order to generate the gate pulses of semiconductor switches. Moreover, this strategy is used to control both the active and reactive powers. Therefore, a thoroughly controlled current with a proper quality can be supplied to the grid from a single source renewable energy resource. The operating procedure, design consideration, comparison study, and the experimental results for a 510 W prototype are presented in order to validate the correctness and feasibility of the proposed topology. [ABSTRACT FROM AUTHOR]

Summary: This article proposes a new Zeta‐based switched‐capacitor (SC) dc‐dc converter, which has many advantages such as increased voltage gain, decreased duty‐cycle, lower voltage stress on components such as its capacitors and input switch, and increased output power over traditional dc‐dc converter structures. In traditional converters such as Zeta converter, there is only one coupling capacitor, which works as a medium for transferring the power between input and the output. However, in the proposed Zeta‐based converter, there are multiple coupling capacitors, which are used based on dc‐dc SC converter principles. By using these switched coupling capacitors, the mentioned advantages are obtained for the proposed structure, which in turn make this converter more applicable for industrial applications. The analysis has been validated by comprehensive and precise comparisons and experimental results. [ABSTRACT FROM AUTHOR]

In this study, a new non-isolated high step-up dc-dc converter using one switch and low-voltage stress on semiconductors is presented for photovoltaic applications. The proposed converter consists of one switch in the input side (S), voltage multiplier units (D-C-L), one diode in the output side (Do) and one capacitor (Co). To achieve high-voltage gain and power level, the proposed converter can be extended to n stages of voltage multiplier units. Hence, the output voltage level will be reasonably increased and the nominal value of power devices will be decreased. Therefore, the voltage stress across the power switch is decreasing for different duty cycles at high power levels. As a result, the efficiency of the proposed converter can be increased by using one switch with lower resistance rDS(on). To verify the carried mathematical analysis of the proposed converter and circuit implementation are validated through both the simulation and experimental results that accordance each other well. The experimental results of two prototypes (with n = 2, 3) in about 290 W operating at 33 kHz are provided. [ABSTRACT FROM AUTHOR]

This study proposes an improved non-isolated single-inductor multiple-input buck DC–DC converter, with reduced number of components. Less component count can reduce the size, mass and cost of converter. Simultaneous or independent power transfer capability has been provided for input sources. The bidirectional power flow capability has also been provided through usage of a battery without any additional switches. This makes the topology very suitable for hybrid energy systems or hybrid electric vehicle/electric vehicle applications. Different operational modes of proposed topology have been presented. Then, a generalised relationship has been proposed for calculation of critical inductance (as an important design parameter) of proposed n-input buck topology. To make a better judgement, the proposed topology has been compared with recently presented novel topologies. Also, a simple proportional–integral based controller has been applied to regulate output voltage and assign the portion of power that each input source should provide. To confirm the validity of proposed topology and theoretical concepts, the three-input version has been modelled and simulated in PSCAD/EMTDC software and implemented experimentally. Simulation and experimental results validate proper performance of proposed topology. [ABSTRACT FROM AUTHOR]

Purpose Presence of photon attenuation severely challenges quantitative accuracy in single-photon emission computed tomography ( SPECT) imaging. Subsequently, various attenuation correction methods have been developed to compensate for this degradation. The present study aims to implement an attenuation correction method and then to evaluate quantification accuracy of attenuation correction in small-animal SPECT imaging. Methods Images were reconstructed using an iterative reconstruction method based on the maximum-likelihood expectation maximization ( MLEM) algorithm including resolution recovery. This was implemented in our designed dedicated small-animal SPECT (HiRe SPECT) system. For accurate quantification, the voxel values were converted to activity concentration via a calculated calibration factor. An attenuation correction algorithm was developed based on the first-order Chang's method. Both phantom study and experimental measurements with four rats were used in order to validate the proposed method. Results The phantom experiments showed that the error of −15.5% in the estimation of activity concentration in a uniform region was reduced to +5.1% when attenuation correction was applied. For in vivo studies, the average quantitative error of −22.8 ± 6.3% (ranging from −31.2% to −14.8%) in the uncorrected images was reduced to +3.5 ± 6.7% (ranging from −6.7 to +9.8%) after applying attenuation correction. Conclusion The results indicate that the proposed attenuation correction algorithm based on the first-order Chang's method, as implemented in our dedicated small-animal SPECT system, significantly improves accuracy of the quantitative analysis as well as the absolute quantification. [ABSTRACT FROM AUTHOR]

This study investigates a multiple input buck dc-dc converter. Different operational modes of the converter for two-, three- and four-input sources are studied then, for each item the relation of critical inductance between continuous conduction mode and discontinuous conduction mode is calculated. Finally, a generalised relationship is proposed for calculation of critical inductance of n-input topology, which is true for any number of input sources. Experimental and simulation results in power systems computer-aided design/EMTDC are presented to validate the theoretical concepts and proposed generalised relation of converter critical inductance. [ABSTRACT FROM AUTHOR]

This paper presents a new family of cascaded multilevel inverters (CMLIs) which can generate a considerable number of output voltage levels with minimum number of required accompanying switching devices. Conceptually, each stage of proposed CMLI is composed of using a novel capacitor-based unit including two floating capacitors, one embedded dc voltage source and three power switches. In this case, the balanced voltage of integrated capacitors can be precisely provided as self-voltage balancing without using any auxiliary circuits, close loop systems and intricate modulation techniques. In addition, to reach different number of output voltage levels, four different algorithms pertaining to the symmetrical, binary asymmetrical, trinary asymmetrical and also hybrid patterns for determining the magnitude of isolated dc voltage sources are presented. Hereby, proposed hybrid structure is capable of working under mixed switching frequency without aiming the conventional full H-Bridge cell. Therefore, a high quality of output waveforms with reduced switching devices as well as power loss dissipation can be alternatively achieved. To confirm the validity of proposed CMLI, a complete comparison with several recently presented topologies besides several simulation and experimental results based on trinary asymmetrical and hybrid evolved structures will be also given. [ABSTRACT FROM AUTHOR]