A new fundamental structure of a single-phase transformer-less grid connected multilevel inverter based on a switched-capacitor structure is presented in this study. By employing the series-parallel switching conversion of the integrated switched-capacitor module in a packed unit, attractive features for the proposed inverter can be obtained such as high efficiency and boosting ability within a single stage operation. Also, using a common grounding technique provides an additional advantage of reducing the leakage current. Moreover, the presented structure generates a multilevel waveform at the output voltage terminals which reduces the harmonics in the system. A peak current controller is utilized for triggering the gate of the power switches and controlling both the active and reactive powers. This results in a tightly controlled current with an appropriate quality that can be injected to the grid using a single source renewable energy resource. Operating procedures, design considerations, comparison studies and test results of a 620 W prototype are also presented to validate the accuracy and feasibility of the proposed multilevel inverter.

Photovoltaic (PV) string inverters with transformerless grid-connected architecture is the commonly used solar converters owing to its appliance-friendly and cost-effective benefits. A novel circuit configuration of such converters is presented in this study, which relatively addresses the shortcoming of most of the conventional topologies such as the problem of leakage current, voltage ratio transformations, and power quality. The proposed structure is on the basis of series-parallel switching conversion of the switched-capacitor (SC) cell and is comprised of only six unidirectional power switches with a common-grounded (CG) feature. Through the use of SC cell and CG connection of active and passive used elements, not only is the number of output voltage level enhanced up to five but also a two times voltage boosting feature with a single stage operation as well as elimination of the leakage current is acquired. Herein, to inject a tightly controlled current into the grid, a peak current controller approach has been used which can handle both the active and reactive power supports modes. Theoretical analysis, comparative study, design guidelines and some experimental results are also given to corroborate the feasibility and accurate performance of the proposed topology.

In this paper, a developed structure is proposed for High Step-up Non-Isolated Non-Coupled Inductor based Multi-Port dc-dc converters. The voltage gain per number of devices of proposed topology is higher than that of similar topologies. This means that, by using the same number of devices, the proposed topology can generate higher gains than other structures. In other words, the proposed topology utilizes less number of devices for producing the same voltage gain, which leads to less total cost, size, weight and complexity. Despite high voltage gain, the Normalized Peak Inverse Voltage on switches/diodes is low. Higher number of input ports leads to higher gains and lower NPIVs on devices. The load energy can be absorbed and stored in first input unit. Modularity, simple structure, continuous input currents and low input current ripple are the other profits of proposed topology. Low/medium power applications are suggested for proposed structure. Proposed topology has been explained and operational modes along with steady state analysis have been discussed. For better verification, proposed topology has been compared with several multi-port high gain converters. Comparison results confirm the advantages of proposed topology. Finally, the proper performance of proposed topology has been validated by experimental results.

This paper presents an interleaved converter which benefits the coupled inductor and built-in transformer voltage multiplier cell (VMC). Compared with the other converters with only built-in transformer or only coupled inductor, the combination of these techniques gives an extra degree of freedom to increase the voltage gain. The VMC is composed of the windings of built-in transformer and coupled inductors, capacitors and diodes. The voltage stress of MOSFETs are clamped at low values and can be controlled via the turns ratio of the built-in transformer and coupled inductor that increases the design flexibility. Moreover, the energy of the leakage inductances is recycled to the clamp capacitors which avoids high voltage spikes across MOSFETs. In addition, the current falling rate of the diodes is controlled by the leakage inductances and the reverse current recovery problem is alleviated. Meanwhile, due to interleaved structure of the proposed converter, the input current ripple is minimized and the current stress of the power devices are decreased. The principle operation and steady-state analysis is given to explore the advantages of the proposed converter. Finally, a 1.3 KW prototype with 50-600V voltage conversion is built to demonstrate the effectiveness of the proposed converter

An expected lifetime of converters is of great importance for optimal decision-making in the planning of modern Power Electronic (PE) systems. Hence, the lifetime management of power electronic systems has attracted a lot of attention in academia and industry. This paper is a guideline for managing the lifetime of power converters. Analyzing the different kinds of failures, failure modes and their corresponding mechanisms are investigated in the first section along with the failure data needed as input parameters of the assessment. In the second section, lifetime prediction in two aspects of component-level and system level is discussed and all the possible techniques to achieve them are investigated and compared. All the steps required to predict the lifetime in the component-level including electrothermal modeling, cycle counting, lifetime model, damage accumulation, parameter estimation, and lifetime distribution are described and then system level methods consisting of reliability block diagrams, fault-tree analysis, and Markov chains are examined and compared. The last section contains the roadmap of the lifetime extension including the reliable design and condition monitoring.

A new scheme of single phase transformerless grid connected inverter is presented in this study. By employing the series-parallel switching conversion of the integrated switched-capacitor module in a packed unit, some attractive features for the proposed inverter can be obtained. Such promising features can be quantified as more than 97% overall efficiency for a wide range of output power, two-time boosting ability within a single stage operation and almost totally suppression of the leakage current through using the common grounding technique. In this case, a peak current controller strategy is used in order to trigger the gate of power switches and control both the active and reactive powers. Therefore, a tightly controlled current with an appropriate quality can be injected to the grid from a single source renewable energy resource. Operating procedure, design consideration, comparison study and a 513 W built prototype results are also given to prove the correctness and feasibility of the proposed circuit.