Journal of Electrical Engineering & Technology最新文献

This paper investigates the structural-electromagnetic coupled problem of a permanent magnet assisted-synchronous reluctance motor (PMa-SynRM) for railway vehicles considering the barrier filling. The PMa-SynRM is suitable as a traction motor for railway vehicles but is vulnerable to the structural stability of the rotor under centrifugal force. Therefore, the structural characteristics of the PMa-SynRM should be considered, and the structural influences on the electromagnetic performance are also important based on the stress-dependent properties of the electrical steel core. To improve the structural stability, the concept of barrier filling is proposed, which involves inserting a substance into the magnetic flux barrier region of the PMa-SynRM and balancing the loads in the rotor core. The structural analysis results with the barrier fillings are compared for a wide range of their physical properties. We input stress and strain data by element into the rotor electrical steel core of the electromagnetic model, which consists of the identical mesh as the rotor structural analysis results and set conditions to reflect the stress-dependent B-H and iron loss data to analyze the electromagnetic performance including coupled effects. Finally, the best filling substance is derived and applied based on the previous structural analysis results, clarifying the improvement in the structural and electromagnetic characteristics.

As the adoption of IoT technology in power systems accelerates and the need for improved methods to handle large volumes of data emerges, real-time big data smart platforms must address the growing data processing demands in IoT integrated power systems. Therefore, in this study, we assess the performance of Hadoop and Spark for iterative computing and real-time data processing applications. Our evaluation is based on metrics such as execution time, resource utilization, and scalability, particularly with increasing data volume. The comparison aims to provide guidance to researchers, practitioners and entrepreneurs on platform selection depending on their specific requirements. The study identified the strengths and weaknesses of both platforms and provided valuable insights into optimizing the performance of big data applications. Text documents and charts for Word Count and PageRank tasks were used for comparison, and performance testing was performed on datasets of different sizes. The results showed that Spark outperforms Hadoop in most applications, especially in iterative computation and real-time data processing, due to its use of in-memory computation. However, Hadoop is best suited for batch processing operations that require multiple steps. It can perform these operations in parallel across multiple cluster nodes, enabling fast processing of large amounts of data. This comprehensive performance comparison of Hadoop and Spark in iterative computing and real-time data processing applications provides valuable information for researchers, practitioners, and enterprises on the trade-offs and benefits of using these big data platforms.

Aiming at the problem that the existing vulnerability assessment models ignore the state transformation of information nodes and delay effect of information network, an improved cascade failure model is proposed to assess the vulnerability of cyber physical power system. Firstly, the cyber physical power system model is established according to the topological structure and correlation of the network. Secondly, considering the overload state and recovery process of cyber nodes, as well as the physical layer power flow optimization and information flow redistribution in the process of fault propagation, an improved cascading failures model is established. Finally, the vulnerability index is established from the topological structure and the running state of the system to assess the vulnerability of the cyber physical power system. The simulation results show that the deliberate attack is more destructive to the system than the random attack, as well as that the fault propagation is faster. Moreover, the vulnerability of CPPS can be decreased by increasing the overload and recovery parameters within a certain limit.

With the growing integration of renewable energy (RE), there is an increasing emphasis on system flexibility, underscoring the need for a high-voltage direct current (HVDC) infrastructure. In Korea, multi-infeed HVDC (MIDC) systems asynchronously interconnect the mainland and Jeju Island to enhance the stable power supply of Jeju power system. However, as the penetration of RE expands, the risk of transmission line (TL) overload increases, affecting both the mainland and Jeju, potentially leading to regional conflicts based on the operation point of MIDC. To mitigate this issue, this study proposes a methodology for determining the optimal operating point of MIDC to alleviate TL overloads and mitigate the possible curtailment of RE. The impact of the operating point of MIDC and the output of RE on TL overloads is determined through a sensitivity analysis using the power transfer distribution factor. We then propose a method to determine the steady-state optimal operating point of MIDC through linear programming-based optimization for the three optimization objectives. The proposed strategy is validated through case studies of a real Korean power system using PSS/E and MATLAB.

Todays, Micro-Grids (MGs) include various types of distributed energy resources such as Wind Turbines (WT), PhotoVoltaics (PVs), Energy Storage Systems (ESSs), Combined Heat and Power units (CHPs), and demand-responsive loads. The variable nature of WT and PV resources and single contingencies of CHP units jeopardize the reliability of MG's customers during operation periods. Demand-side response program manages the time-consumption pattern of responsive loads (RLs) to overcome these uncertainties. As a distribution network is often divided into multiple MGs therefore this paper proposes a bi-level reliability-based model for the planning and partitioning of them in presence of RLs. At the first level, Tie Switches (TSs) and energy resources placement are determined to meet the annual peak demand to minimize the total costs. Output results of first level feed to next level as input data until the power exchange between MGs and the upstream distribution system and also RLs participation considering the desirable risk for all MGs customers are optimally calculated to maximize multiple MGs benefit. Since the second-level outputs can affect on first-level results, a bi-level model is applied. A genetic algorithm is used to solve each level's problem. For validation, numerical studies are applied to a 25-Bus test distribution network with three MGs and five TSs. The simulation results show that MG planning in islanded mode causes more investment costs depending on the installation of DERs with higher capacities. In addition, the participation of RLs in planning islanded or grid-connected MGs leads to a significant decrease in the system investment and operation, loss, and reliability costs.

In academia, it is essential to verify the integrity and completeness of knowledge, for which an open peer review process is now being conducted by experts in the field. Recently, various open peer review systems have been designed to realize effective open peer review. However, (1) their design principles are not consistent; (2) use cases are rather static and limited; and (3) their implementations have been rarely introduced. To address these issues and realize practical deployment of open peer review systems, in this paper, we present a template for creating a configurable open peer review system. In particular, using the proposed template, an open peer review system operating on Hyperledger Fabric, which allows flexible and dynamic application of various open peer review policies, can be easily instantiated. In addition, by introducing a broker module, all pieces of information in the review process could effectively be handled in both the existing review system currently in operation and the created blockchain-based open peer review system, allowing a gradual transition to the new system. Since the proposed template is embodied based on full implementation and disclosed to the public in the form of an open source, we believe that this work can contribute substantially to the popularization of blockchain-based open peer review systems.

The sensorless control of permanent magnet synchronous motor (PMSM) has issues of complex signal process, cumbersome system structure and parameter setting, etc. To eliminate these defects and reduce costs of computation, a sensorless control method based on specific voltage feed-forward decoupling (VFD) is proposed for the medium and high-speed regions. On the one hand, the proposed method utilizes a specific feed-forward voltage to decouple the d-q axis current, so that the output of current regulator directly contains the position error signal and rotor magnetic flux information, which simplifies the signal processing. On the other hand, the normalization of position error signal eliminates the influence of rotor speed and magnetic flux on the loop feed-forward gain of position estimation. With the proposed method, the rotor position and the rotor magnetic flux can be observed simultaneously and the process of parameter setting can be simplified. Moreover, to meet the engineering requirements, a full-speed sensorless control scheme combines IF control starting strategy with VFD is designed in this paper. The experimental results show that the sensorless method for the medium and high speed proposed in this paper has good dynamic and static performance, the observed result of rotor magnetic flux is accurate, and the designed sensorless control scheme for the full-speed region is simple and practical.

MVDC(Medium Voltage DC) distribution system has been on the rise for large transmission capacity with low energy loss, undersea power transmission, and so forth. Recently it has been a key factor of renewable energy transmission in the smartgrid. However, in the process of the design and the implementation of the protection devices for the grid, engineers face the difficulties to find out MVDC equipments, especially commercialized protection coordination devices, such as hybrid CB, VCB, ACB, MCCB, fuse, power contactors(CTR), etc. And those equipments have generally provided the narrow range of the DC rated voltage and the rated current and the power capacity, and given few types of the protective relay with narrow range. It gives a big restriction to design the protection elements and apply the equipments into the grid. This paper presents the protection coordination methods to design and operate the actual application for 5 kV MVDC grid with distributed generators(DG). And also, this paper performs the modeling of 5 kV MVDC grid including protection devices such as fuse, MCCB, CTR based on the PSCAD/EMTDC. From the simulation results of the operation characteristics of protection device according to the potential scenarios, it is confirmed that appropriate protection devices have been selected for the MVDC off-grid MG system, and protection cooperation is properly performed for all possible fault locations.

The creation of practical renewable energy sources has taken precedence in light of the world’s rising energy demand and environmental concerns. Renewable energy hybrid plants, which combine various renewable energy sources, present a viable approach to tackle both the issue of energy production and the environmental one. In this study, we offer the Intelligent Whale Algorithm (IWA), a unique optimization technique for designing and optimizing Renewable Energy Hybrid Plants (REHP) inspired by whale pods’ collective intelligence. We examine the method using a case study involving a Renewable Energy Hybrid plants system that includes a wind turbine, ( {H}_{2}) tank, fuel cell (FC), batteries, diesel generator, electrolyzer and PV panels. This study highlights the value of the IWA in removing grid integration barriers for renewable energy sources and enhancing the energy industry. A helpful tool for constructing multi-utility hybrid renewable energy facilities has surfaced: the IWA.

In this study, the electrical characteristics of a non-isolated basic quasi-Z-source converter (qZSC) with an inductor output filter and a non-isolated basic qZSC with a diode output filter are compared. The electrical characteristics of the non-isolated qZSC are the input current and voltage ripple of the qZ-network, the current stress of the output filter, and the efficiency of the converter. The circuit equation of each converter was obtained, and the voltage gain, maximum current, minimum current, and required element ratings were calculated. Under the conditions of input voltage 80 V and output voltage 120 V, the shoot-through duty ratio for the same voltage boost gain was much lower for the diode filter qZSC, and the input current, qZ-network capacitor voltage, and the required minimum element ratings were also more advantageous than the inductor filter qZSC. However, in terms of the output filter, the inductor filter qZSC has a current stress advantage over the diode filter qZSC. A DSP-based experiment was performed to verify the validity of this study. The capacitor voltage and inductor current of the qZ-network and the voltage of each converter and the current of the output filter were compared under the condition of an input voltage of 80 V and an output voltage of 120 V. Finally, as a result of comparing the efficiency of voltage gain change or input voltage change for the same load and the efficiency according to load change at a constant duty ratio, it was found that the diode filter qZSC is advantageous by about 1%.