Reliability of power inverters is of dominant importance in various applications including industrial, military, aerospace, and commercial applications. Therefore, developing fault tolerant (FT) power inverters is extremely needed from the viewpoint of system availability and avoiding harmful consequences. Tolerating various types of faults, preserving full output ratings after the fault, and being cost effective represent the main challenges for most of existing FT solutions. In this paper, a new FT single phase five-level inverter topology is proposed. The proposed topology can effectively tolerate both of single or multiple switches faults, whether they are of open or short circuit fault types. Moreover, the proposed topology does not deteriorate system efficiency in post fault operation compared to the previously developed FT solutions. Evaluation of the effectiveness and robustness of the proposed topology is verified in both of simulation and experimental environments. Different case studies are investigated in order to cover various types and locations of switch faults. Moreover, comprehensive comparisons are provided to validate the superiority of the proposed topology over the previously addressed techniques.

Among all renewable energy sources, solar cells are considered the most popular solution for a clean source of energy and have a wide range of applications from few watts to Megawatt industrial and domestic loads. Building a precise mathematical model based on nonlinear equations for solar cells as well as photovoltaic (PV) modules is an essential issue for reasonable performance assessment, control and optimal operation of PV energy systems. In the current study, a novel optimization algorithm, Tree Growth Algorithm (TGA), is applied for accurate and efficient extraction of the unknown solar cell and PV module parameters. TGA is applied for estimating the unidentified parameters of PV models. Single diode model (SDM), double diode model (DDM) and three diode model (TDM) are investigated in the mathematical models of both solar cells and PV modules. The obtained results from the application of TGA to achieve this objective are compared with different algorithms reported in the literature. Moreover, the results demonstrated that the proposed algorithm of TGA superior to other reported methods. The good matching of the I-V characteristic curve of the computed parameters with those of the measured data from the manufacturer’s PV modules/cells datasheet proved that the proposed TGA may function as a competitor to the methods provided in literature for parameters’ identification of PV of solar cells.

Powder cores have been gaining much attention as one of the attractive magnetic cores used in power converters due to their superior features such as high saturation flux density and their capability to suppress fringing flux due to the distributed airgaps. However, powder cores have a unique feature that the relative permeability of the magnetic core varies depending on the magnetic field intensity. The comprehensive modeling of variable relative permeability, design method of powder cores, and computer simulation methods are not well discussed in the relevant literature. This paper proposes a novel modeling, magnetic design method, and simulation technique considering dc superimposition characteristics of powder cores. The modeling method relies on a simple novel model equation representing the behavior of the variable relative permeability under the dc current superimposition condition, which is helpful to evaluate the performance of powder cores and to properly design various magnetic components. In this evaluation, five different magnetic powder cores are used to show the accuracy and properness of the proposed method. Theoretical analysis has been presented and the effectiveness of the proposed methods has been evaluated through simulation and experimental tests.

Changes are being implemented in the electrical power grid to accommodate the increased penetration of renewable energy sources interfaced with grid-connected inverters. The grid-forming (GFM) control paradigm of inverters in active power grids has emerged as a technique through which to tackle the effects of the diminishing dominance of synchronous generators (SGs) and is preferred to the grid-following (GFL) control for providing system control and stability in converter-dominated grids. Therefore, the development of the GFM control is important as the grid advances towards 100% inverter-based grids. In this paper, therefore, we aim to review the changing grid scenario; the behaviour of grid-connected inverter control paradigms and major GFM inverter controls, including their modifications to tackle low inertia, reduced power quality, fault-ride through capability, and reduced stability; and the state-of-the-art GFM models that are pushing the universality of GFM inverter control.

Multilevel inverter (MLIs) have proven superior performance in several applications, especially in photovoltaic (PV) applications. However, power switches in MLIs possess high failure rates due to unequal power losses distributions that shorten lifetime of the whole PV inverter. Therefore, a new pulse width modulation (PWM) methodology for loss balance in grid connected photovoltaic (PV) single-phase five-level inverters is presented in this paper. The proposed loss balance PWM (LBPWM) method is based on swapping the utilization of power switches through half or quarter of the fundamental line period based on the redundancies between the switching states in MLIs. Additionally, the proposed LBPWM method achieves natural balance among voltages over the DC-link capacitors. The effectiveness and feasibility of the proposed LBPWM method are verified using the simulation environment and experimental prototype. Different operating conditions and points of PV inverters are investigated in addition to reliability evaluation of the PV inverter are provided. Moreover, the superior performance criterion of the proposed LBPWM methods are verified through comprehensive comparisons with the most prominent previously developed PWM methods in the literature. The generalization and implementation steps of the proposed LBPWM method are also provided.