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Hybrid DC microgrid clusters contain various types of converters such as BOOST, BUCK, and bidirectional DC/DC converters, making the control strategy complex and difficult to achieve plug-and-play. The common master–slave hierarchical control strategy makes it difficult to achieve accurate and stable system control. This paper proposes an accurate peer-to-peer hierarchical control method for the hybrid DC microgrid cluster, and the working principle of this hierarchical control method is analyzed in detail. The microgrid cluster consists of three sub-microgrids, where sub-microgrid A consists of three BUCK converters, sub-microgrid B consists of three BOOST converters, and sub-microgrid C consists of two bidirectional DC/DC converters. According to all possible operations of various sub-microgrids in the microgrid cluster, the top-, mid-, and bottom-level controls are designed to solve the coordination control problem among different types of sub-microgrids. In this paper, a hybrid microgrid cluster simulation model is built in the PLECS simulation environment, and an experimental hardware platform is designed. The simulation and experiment results verified the accuracy of the proposed control strategy and its fast plug-and-play regulation ability for the system. [ABSTRACT FROM AUTHOR]

Power electronics is a core subject in electrical and electronics engineering at the undergraduate level. The rapid growth in the field of power electronics requires necessary changes in the curricula and practica for power electronics. The proposed next-generation power electronics teaching laboratory changes the learning paradigm for this subject and is for the first time used for teaching purposes in Pakistan. The proposed controller hardware-in-the-loop (CHIL) laboratory enabled students to design, control, and test power converters without the fear of component failure. CHIL setup allowed students to directly validate the physical controller without the need for any real power converter. This allowed students to obtain more repeatable results and perform extreme digital controller testing of power converters that are otherwise not possible on real hardware. Furthermore, students could start learning power electronics concepts with hardware from the beginning on a safe, versatile, fully interactive, and reconfigurable platform. The proposed laboratory meets the accreditation board for engineering and technology (ABET) student outcome criterion K such that students can continue with the same hardware and software toolset for graduate and research purposes. The knowledge and skills acquired during undergraduate years can help students create new solutions for power electronics systems and develop their expertise in the field of power electronics. The results obtained from the survey indicated that the majority of the students were satisfied with the laboratory setup. They also expressed appreciation over the provision of a high-level graphical language "LabVIEW" for the digital controllers compared to conventional low-level text-based languages such as VHDL, Verilog, C, or C++. [ABSTRACT FROM AUTHOR]

High-voltage direct-current (HVDC) transmission systems are considered an outstanding solution due to high electrical losses emerging from long-distance transmission. However, HVDC transmission lines (TLs) are vulnerable to lightning strikes. In this work, the Yunnan-Guizhou 500 kV HVDC transmission system is used as a case study to evaluate the impact of lightning strikes on DC-TL overvoltages, as no research studies have been conducted to assess the lightning transient behavior of DC-TLs. A comprehensive investigation of the 500 kV DC-TL transient performance during lightning strikes is performed, taking into account different technical aspects that have not been studied in detail by previous researchers. Additionally, analysis of the back-flashover phenomenon has not been conducted well in previous work, and results on the effect of changing the lightning strike current peak and tower grounding resistance on shielding-failure flashover are quite limited. The distributed-parameter model is used to represent the DC-TL using the electromagnetic transients program (EMTP), considering real parameters of shielding wires and DC towers to study the lightning impact in the case of back-flashover and shielding-failure phenomena. Lightning strike is applied to the shielding wire, and the impact of increasing the peak value of lightning current is investigated on the back-flashover occurrence. Moreover, the influence of tower grounding resistance variation on the transient overvoltages across the tower body and back-flashover phenomenon is evaluated. From the simulation results, increasing the lightning current peak and grounding resistance results in higher overvoltages across the tower body, which increases the probability of back-flashover. Additionally, the shielding failure of the TL is assumed, and the variation impact of the lightning current peak and grounding resistance on shielding-failure flashover is investigated. The results show that the impact of the lightning current peak has a more significant impact than the grounding resistance in the case of shielding-failure flashover. [ABSTRACT FROM AUTHOR]

Wind energy is one of the most attractive sustainable energy resources since it has low operation, maintenance, and production costs and a relatively low impact on the environment. Identifying the optimal sites for installing wind power plants (WPPs) is considered an important challenge of wind energy development which requires careful and combined analyses of numerous criteria. This study introduces a high-resolution wind farms suitability mapping based on Fuzzy Analytical Hierarchy Process (FAHP) and Geographic Information System (GIS) approaches considering technical, environmental, social, and spatial aspects, representing eight different criteria. First, a multi-criteria decision-making analysis based on the FAHP method is employed to assign appropriate weights for the addressed criteria with respect to their relative importance. Since the traditional AHP method, which was found employed in the majority of the relative case-studies, is not efficient in dealing with uncertainty when experts use a basic scale (0 to 1) for their assessments, the FAHP provides more flexible scales through the utilized fuzzy membership functions and the natural linguistic variables. Consequently, this helps to facilitate the assessments made by experts and increases the precision of the obtained results (weights). Next, the high-resolution GIS is used to carry out a spatial analysis and integrate various factors/criteria throughout the proposed index to produce the final suitability map and identify the unsuitable areas. The presented study emphasizes investigating the lightning strike flash rate due to its significant influences on the wind turbine's safety and operation, yet this crucial factor has been seldomly investigated in previous studies. The obtained findings revealed that the wind speed, the land slope, and the elevation had the highest weighted criteria with 33.1%, 24.8%, and 12.2%, respectively. Besides, the final-developed suitability map revealed that 23.22% and 8.31% of the Sudanese territory are of high and very high suitability, respectively, for wind farms installation which are considered sufficient to cover the electricity needs. The difficulty of acquiring real data and resources for the addressed location was the main challenge of the presented work. The work outlook addresses the suitability mapping of hybrid photovoltaic-wind turbine energy systems, which will require addressing new and significant criteria in the applied methodology. [ABSTRACT FROM AUTHOR]

Wind energy integration in power grids is increasing day by day to reduce the use of fossil fuels, and consequently greenhouse gas emissions. Using the pulse-width modulated (PWM) power converters in wind turbine generators, specifically in doubly-fed induction generators, results in generating a common-mode voltage (CMV). This common-mode voltage causes a flow of common-mode current (CMC) that leaks through the stray capacitances in the generator structure. These currents impose a voltage on the generator bearing which may deteriorate them. In the current work, an active common-mode voltage canceler (ACMVC) is developed to eliminate the CMV produced by a PWM converter. The ACMVC generates a compensating voltage at the converter terminals to eliminate the CMV with a subsequent reduction of the voltage stress on the generator bearing. This compensating voltage has the same amplitude as CMV, but opposite polarity. A simulation of the ACMVC model is performed using the PSCAD/EMTDC (Electromagnetic Transient Design and Control) software package. Results confirm the effectiveness of ACMVC in canceling not only the CMV but the CMC and bearing voltage as well. In addition, the relationship between the rise time of CMV and the peak value of CMC is investigated. [ABSTRACT FROM AUTHOR]