Coreless axial flux permanent magnet (PM) machines (AFPM) have attracted significant interest over the last decades as an ideal candidate for a wide range of applications. This is generally due to their advantages, such as the high torque density, high power density, and the light weight. This paper investigates the performance of a coreless axial flux-switching generator (AFSMG) with improved torque characteristics. The inherent feature of the axial flux-switching machines is the high cogging torque. Hence the main advantage and the novelty of this research is addressing a suitable key for its torque characteristics challenges. In this regard, a comprehensive study is done on rotor tooth shape. First, the geometry and the shape of the rotor tooth are optimized, and then the skewing technique is applied to minimize the cogging torque and improve the total harmonic distortion. Finally, the cogging torque and the THD are calculated in the primary design and the optimal design. The Taguchi method is utilized to improve the primary model. A comparative analysis of the primary and optimized model is carried out, which indicates the better performance of the optimized design. Furthermore, the 3D finite element method is applied to verify the results of the presented model.

This paper proposes a novel approach for coherent Generators online clustering in a large power system following a wide area disturbance. An interconnected power system may become unstable due to severe contingency when it is operated close to the stability boundaries. Hence, the bulk power system controlled islanding is the last resort to prevent catastrophic cascading outages and wide area blackout. Meanwhile, the aggregation of the coherent Generators is the most important step in large power grids intentional defensive splitting to guarantee the dynamic stability of the created islands and reduce the computational burden of the huge initial search space. The proposed method of this paper determines the coherent machines based on the electrical parameters of the synchronous Generators instead of the dynamical parameters such as rotor angle or speed curves, speed participation factors, etc. The stator and excitation windings flux, excitation voltage and current have been proposed as coherency indices. The proposed coherency based aggregation has been carried out on New England 39-bus test system. The time-domain simulation results demonstrate the effectiveness and capability of the proposed method to identify the coherent machines following a severe contingency.

First, the impedance source idea is used to alleviate the problems of Voltage Source Inverters (VSI), and Current Source Inverters (CSI), which leads to the introduction of the Z-Source Inverter (ZSI). Afterwards, not only did the Z-source cells were used in the inverter topologies, but they were also added to other power electronic converters, such as dc-dc choppers, ac-dc rectifiers, and ac-ac converters. Moreover, these power electronic converters, which have Z-source cells, are widely used in different applications. In particular, the existing single-phase ac-ac Z-source converters are reviewed in this paper, and their different features are studied in detail. In the past decades, the single-phase Z-source ac-ac converters have attracted significant attention due to their unique features, such as single-stage power conversion, boost in-phase, and buck out-of-phase features. Therefore, several modified or improved structures along with different control methods have been introduced to solve their problems and limitations. Based on the four features, these structures can be categorized into four groups: without magnetic coupling, with magnetic coupling, able to change the frequency, and inherent commutation. In this review, a general diagram is depicted, which many of the existing topologies can be obtained from it. Additionally, new topologies can be obtained by having this general diagram. After studying these structures, a comparative study is made to obtain the advantages and disadvantages of each. In the end, some advice and recommendations are given to develop and obtain new structures.