Hasil untuk "Distribution or transmission of electric power"

J. Sumaya-Martinez, J. Mulia-Rodriguez

Extraordinary acoustic transmission is commonly associated with periodic or multi-aperture structures. In this work, we show that a single subwavelength slit can support strongly enhanced transmission when its boundary response is described by an effective impedance. Using a reduced analytical model together with numerical calculations, we demonstrate that appropriate impedance tuning leads to efficient coupling between the incident field and the slit mode, resulting in transmission levels approaching unity. The observed enhancement is governed by impedance matching rather than geometric periodicity, highlighting a minimal mechanism for extraordinary transmission. This study establishes boundary impedance control as a versatile route for manipulating acoustic wave transport through deeply subwavelength apertures.

Jeonghoo Park, Beomju Kim, Byongjun Lee et al.

Active power from renewable energy sources (RESs) is not suitable for long-distance transmission, and surplus generation can introduce stability concerns in high-voltage distribution networks. To address this problem, this study introduces the Local Renewable Management System (LRMS), a fully operational real-time framework deployed within the regional power system of the Korea Electric Power Corporation. The objective of the LRMS is to maximize the hosting capacity of RESs in high-voltage distribution grids while ensuring system stability. Unlike traditional centralized management systems, which regulate renewable generation primarily at the transmission level, the LRMS emphasizes localized control, enabling precise and adaptive responses to regional stability challenges arising from rapid RES penetration. Key processes include integration of real-time weather forecasts, RES output predictions, and stability assessment. Based on the calculated system non-synchronous penetration margin, the LRMS determines whether RES output can be increased or must be curtailed. Operational results from the Honam power system demonstrate the effectiveness and practical applicability of the LRMS in managing voltage profiles and system stability. An additional operational case study of the Jeju power system verifies the generalizability of the proposed system. Overall, this work presents a decentralized, data-driven solution for distribution-level RES integration, offering a scalable approach to meet carbon neutrality goals and increase RES penetration.

Hossein Zamani, Vahid Johari Majd, Khosro Khandani

This paper addresses sliding mode control (SMC) design for disturbed fractional-order multi-vehicle networks in order to achieve containment tracking within a certain settling time. The multi-leader case is investigated where the aim of the containment protocol design is that the states of the fractional-order followers eventually are placed inside a convex hull made by the states of the leaders. The convergence rate is designed such that achieving the containment tracking occurs in a fixed-time manner. Unlike the previous works on finite-time containment control protocols of multi-agent systems, here, we offer a tractable design as the upper limit of the settling time of the convergence is achieved independent of the preliminary conditions of the vehicles' states. A novel SMC approach is proposed which enables the multi-vehicle network to reach the containment tracking at presence of the external disturbances. The numerical simulations reveal the correctness and effectiveness of the proposed theoretical approaches.

Robert A. Mostoghiu Paun, Darren Croton, Chris Power et al.

Traditional N-body methods introduce localised perturbations in the gravitational forces governing their evolution. These perturbations lead to an artificial fragmentation in the filamentary network of the Large Scale Structure, often referred to as "beads-on-a-string." This issue is particularly apparent in cosmologies with a suppression of the matter power spectrum at small spatial scales, such as warm dark matter models, where the perturbations induced by the N-body discretisation dominate the cosmological power at the suppressed scales. Initial conditions based on third-order Lagrangian perturbation theory, which allow for a late-starting redshift, have been shown to minimise numerical errors contributing to such artefacts. In this work, we investigate whether the additional use of a spatially adaptive softening for dark matter particles, based on the gravitational tidal field, can reduce the severity of artificial fragmentation. Tidal adaptive softening significantly improves force accuracy in idealised filamentary collapse simulations over a fixed softening approach. However, it does not substantially reduce spurious haloes in cosmological simulations when paired with such optimised initial conditions. Nevertheless, tidal adaptive softening induces a shift in halo formation times in warm dark matter simulations compared to a fixed softening counterpart, an effect not seen in cold dark matter simulations. Furthermore, initialising the initial conditions at an earlier redshift generally results in z=0 haloes forming from Lagrangian volumes with lower average sphericity. This sphericity difference could impact post-processing algorithms identifying spurious objects based on Lagrangian volume morphology. We propose potential strategies for reducing spurious haloes without abandoning current N-body methods.

Larissa Jerrim, Stas Shabala, Ross Turner et al.

We investigate the effect of turbulent magnetic fields on the observed spectral properties of synchrotron radio emission in large-scale radio galaxy lobes. We use three-dimensional relativistic magnetohydrodynamic simulations of fast, high-powered jets to study the structure of the lobe magnetic fields and how this structure affects the radio spectrum of the lobes. It has previously been argued that lobe ages inferred from radio spectra underestimate the true ages of radio galaxies due to re-acceleration of electrons in the lobe, mixing of electron populations, or the presence of turbulent magnetic fields in the lobes. We find that the spectral ages with and without accounting for the lobe magnetic field structure are consistent with each other, suggesting that mixing of radiating populations of different ages is the primary cause of the underestimation of radio lobe ages. By accounting for the structure of lobe magnetic fields, we find greater spectral steepening in the equatorial regions of the lobe. We demonstrate that the assumptions of the continuous injection, Jaffe-Perola, and Tribble models for radio lobe spectra do not hold in our simulations, and we show that young particles with high magnetic field strengths are the dominant contributors to the overall radio lobe spectrum.

Faisal Mohammad, Dong-Ki Kang, Mohamed A. Ahmed et al.

The electrification of transport has proved to be a breakthrough to uplift the sustainable and eco-friendly platform in the global sector in which electric vehicles (EVs) are considered indispensable. In particular, creating intelligent energy management in the power distribution system integrated with electric vehicle charging stations (EVCS) as a new entity is one of the most important challenging tasks. The implementation of the EVCS network infrastructure should facilitate the adoption of the spatiotemporal electricity demand for EVs. The intelligent decision for the transmission, distribution, energy allocation and charging station placement by the control center or central aggregator is only possible by correctly forecasting its usage, occupancy, and energy or charging demand. Techniques like data analytics have enabled to extract data from the EVCS on a daily basis to store and process all the recorded data. To overcome the above-mentioned challenges related to energy demand forecasting for EVCS network, this work proposes two encoder-decoder models based on convolutional long short-term memory networks (ConvLSTM) and bidirectional ConvLSTM (BiConvLSTM) in combination with the standard long short-term memory (LSTM) network. Data on energy demand from EVCS located in four different cities is used in the proposed models. All datasets are preprocessed to make them suitable for the multi-step time-series learning models in order to make the framework data-centric. The suggested architectures are built on the ConvLSTM and BiConvLSTM to extract the key features from the spatiotemporal data of the energy demand data of the EVCS distributed over the time and space. The predicted outcomes generated by the suggested strategy are compared with conventional deep learning models and traditional machine learning techniques.

Yijie Wang, Yiliang Li, Yueshi Guan et al.

With the rapid development of intelligent electric vehicles, the number of electrical equipment increases, and the interconnection and energy transmission between onboard dc buses has become urgent. This article proposes a partial isolated bidirectional converter based on dual active bridge (DAB) converter. By partial switch sharing, the converter has a simplified structure and can supply energy to dc loads of different voltage levels. The system adopts a hybrid control strategy of pulsewidth modulation and triple phase shift modulation and introduces a fundamental phase shift to reduce coupling between variables. The operation process is analyzed, and the models of transmitted power, current stress, and soft-switching range under two typical operation modes, corresponding to the full load and light load, are established. Under wide gain and different power distribution conditions, multiobjective optimization is realized. Finally, the correctness of theoretical analysis is verified by experiments.

F. M. Kgoete, U. Uyor, A. Popoola et al.

Transmission conductor forms the essential pathway where electric power traverses from the generating centre station to the distribution sub-station. Some glitches in power delivery have been attributed to that occasioned by defective transmission conductors. Challenges accruing from transmission conductors can be handled proactively by designing and developing robust conductors. This review was aimed at studying the challenges witnessed in power transmission, ways of ameliorating them, and prospective conductors for future power transmission. In the study, it was observed that lightning, bush fire, short-circuiting, and grid overload are some of the challenges in the transmission grid. It was also observed that aluminium conductor composite core (ACCC) and aluminium conductor composite reinforced (ACCR) are the two best transmission conductors existing presently based on ampacity and efficiency. It was concluded that Al-based composites of CNTs, graphene, BN, Si3N4, and TiC could perform more favourably than the existing transmission conductors. It was recommended that these new materials should be studied further to verify their applicability in transmitting electric power.

Linlin Yu, Xiaojun Tang, Ruihua Si et al.

Abstract In order to meet the current needs of power transmission, people have turned their attention to direct current (DC) transmission. When the alternating current(AC) power grid (PG) fails, it is easy to cause commutation failure in the DC system, thereby increasing the fault scope of the system. Therefore, this article adopts a flexible DC transmission system. Flexible DC converters have many control parameters, and there are mutual influences and conflicts between these parameters. By applying intelligent algorithms to multi‐objective optimization (MOP), these complex MOP problems can be effectively solved and an optimal set of control parameter combinations can be found. This method has an important contribution and novelty for optimizing the converter control parameters of flexible DC transmission systems. This article achieves fast and accurate MOP of the control parameters of flexible DC transmission converters by continuously detecting the similarities between antibodies and maintaining the diversity of the population. The research results show that the average DC side current is about 405A in the first 20 seconds, and the DC side current fluctuates regularly after 20 seconds. This article lays the foundation for establishing a real‐time simulation model of flexible DC transmission systems suitable for real‐time simulation systems.

Yuying Zhang, Chen Liang, Han Wang et al.

Abstract With the development of the digital economy, the power demand for data centers (DCs) is rising rapidly, which presents a challenge to the economic and low‐carbon operation of the future distribution system. To this end, this paper fully considers the multiple flexibility of DC and its impact on the active distribution network, and establishes a collaborative planning model of DC and active distribution network. Differing from most existing studies that apply robust optimization or stochastic optimization for uncertainty characterization, this study employs a novel interval optimization approach to capture the inherent uncertainties within the system (including the renewable energy source (RES) generation, electricity price, electrical loads, emissions factor and workloads). Subsequently, the planning model is reformulated as the interval multi‐objective optimization problem (IMOP) to minimize economic cost and carbon emission. On this basis, instead of using a conventional deterministic‐conversion approach, an interval multi‐objective optimization evolutionary algorithm based on decomposition (IMOEA/D) is proposed to solve the proposed IMOP, which is able to fully preserve the uncertainty inherent in interval‐typed information and allow to obtain an interval‐formed Pareto front for risk‐averse decision‐making. Finally, an IEEE 33‐node active distribution network is utilized for simulation and analysis to confirm the efficacy of the proposed approach.

Reza Mirzahosseini, Elham Rahimi Namaghi

Abstract Fractional slot concentrated winding (FSCW) permanent magnet (PM) machines are gaining more attention for low‐speed applications because of their great advantages. This paper proposes a new structure for an FSCW double rotor axial flux PM synchronous machine (DRAFPMSM) with counter‐rotating rotors. In addition, an analytical formula for the Back EMF waveform of the proposed structure is presented. The accuracy of the formula is investigated by designing a 40 W sample machine. The rotors of this machine rotate with speeds of 600 and 428 rpm in opposite directions. The Back EMF of the sample machine is calculated using the suggested formula. In addition, the finite element method (FEM) is used to determine the Back EMF waveform. Comparison of the obtained results confirms that the new formula yields the Back EMF precisely such that the results well match to those of FEM. The effect of the relative position of two rotors on the Back EMF waveform is investigated using the proposed formula. In addition, the optimum relative position of two rotors for minimizing the Back EMF THD of the case study machine is determined.

Peyman Mousavi, Mohammad Sadegh Ghazizadeh, Vahid Vahidinasab

Abstract In addition to providing mobility, plug‐in hybrid electric vehicles (PHEVs) provide a two‐sided energy exchange opportunity which makes them highly flexible distributed energy storage systems for the future of energy systems. This paper analyzes PHEVs' performance from the perspective of urban traffic and energy using a decentralized multichannel blockchain network based on the hyperledger model. This network using a layered design and local management of energy sources can significantly contribute to urban management and optimal use of its infrastructures. Then, dynamic modelling of PHEVs in this network is performed, and their data is added to the network to evaluate the network performance compared with the current centralized networks. The results indicated that the proposed blockchain network could simultaneously optimize PHEVs' performance, urban traffic management, and energy systems. Furthermore, by utilizing smart contracts, it can consider and optimize multiple challenges, such as congestion in the electricity network, urban traffic, and limited fuel, simultaneously. Therefore, it gives a strong tool to study the impact of mass deployment of PHEVs and their value and role in the sustainable cities and communities of the future while helping to support the global efforts toward affordable and clean energy for all.

Arash Rohani, Ali Nahavandi, Mahyar Abasi et al.

Pathomthat Chiradeja, Praikanok Lertwanitrot, Atthapol Ngaopitakkul et al.

Abstract The protection of traditional high‐voltage capacitor banks relies on an unbalance relay which operates when an internal fuse is blown. However, the unbalance relay cannot indicate the cause of the fault. Thus, an operator wastes time and human resources investigating the fault issues. In this paper, a fault which occurred in a 230‐kV power system of Electricity Generating Authority of Thailand was observed by performing simulations using the Power Systems Computer Aided Design (PSCAD) program. The study system based on the double bus station and 72 MVAR capacitor banks was installed in the form of a back‐to‐back topology. Three scenarios were considered: normal condition, fault occurrence in one capacitor bank and fault occurrence in both capacitor banks. Current characteristics such as the current phase and difference in unbalance current were considered. In addition, discrete wavelet transform was applied to solve the ambiguity of current generated from the PSCAD. The authors’ results suggest that identifying fault events using a coefficient of wavelet is more efficient than relying on the current amplitude. The findings mentioned in this paper can be applied in a traditional power system protection scheme to enhance a system's reliability.

Arman Amini Badr, Amin Safari, Sajad Najafi Ravadanegh

Abstract This paper proposes an approach for segmentation of power systems to prevent uncontrolled islanding. With the development of microgrids (MGs) and increased penetration of renewable energy sources (RESs) in the power system, it is necessary to consider the effect of MGs and the stochastic behaviour of RESs in the controlled islanding process. First, the enormous search space for finding the boundary points is reduced by the clustering of the coherent generators and the buses which are placed in sections that cannot be separated from the coherent groups. Then, linear AC power flow is defined as a sub‐problem and solved by linear programming to satisfy the power system and MG constraints. In this step, an optimization model is defined, and a mixed‐integer linear programming (MILP)‐based model is suggested to find cut‐sets and islands arrangement with reduced load shedding. In view of the fact that the fluctuation of RESs may have the significant effects on the power imbalance, to cover the uncertainties a scenario based stochastic simulation is considered. Finally, the effect of uncertainties on cut‐sets and load curtailment is evaluated. The effectiveness of the proposed methodology is demonstrated by the simulation on the test system.

Yize Li, Yinfeng Wang, Hongbo Ye et al.

Abstract The distribution networks have more frequent and fast voltage fluctuations with the large‐scale access of distributed energy resources and electric vehicles. Based on remote terminal unit (RTU) and distribution terminal unit (DTU), traditional hierarchical control methods are difficult to achieve rapid global coordinated voltage regulation due to static modeling. For this purpose, this paper proposes an integrated dynamic voltage control strategy which integrates the objectives of local voltage control and secondary voltage control. First, simplified dynamic models of controllable equipment in active distribution network are established instead of the static models. On this basis, the state‐space prediction model of the control system is established. Then, based on the improved model predictive control (IMPC), the integrated dynamic voltage control strategy realizes rapid and global coordinated control through state prediction, rolling optimization and real‐time feedback correction. Numerical results show that the proposed strategy can achieve fast global coordinated voltage control in the time scale of seconds.

Hongsen Zou, Zheng Xiang, Weiping Shang

Abstract Flexible DC technology is widely used in long‐distance and large‐capacity transmission and plays a very important role in realizing the optimal allocation of cross‐regional power resources. However, the protection technology of flexible DC systems is not yet mature. The current differential protection is susceptible to the influence of distributed capacitance, which reduces the reliability of the backup protection of the voltage source converter‐based multi‐terminal DC (VSC‐MTDC) system. To enhance the reliability of DC protection, a new scheme based on virtual traveling active wave power is proposed. First, the concept of virtual traveling wave power is innovatively proposed. Subsequently, the fault characteristics and calculation method of the virtual traveling wave power are provided. Accordingly, a protection scheme based on virtual traveling wave power is proposed and the overall process is given. Finally, a typical VSC‐MTDC system is used to verify the reliability of the scheme.

Subarto Kumar Ghosh, Tushar Kanti Roy, Md Abu Hanif Pramanik et al.

Abstract In this paper, a nonlinear decentralized double‐integral sliding mode controller (DI‐SMC) is designed along with an energy management system (EMS) for the DC microgrid (DCMG). This DCMG includes having a hybrid energy storage system (HESS) that incorporates a battery energy storage system (BESS) and supercapacitor energy storage system (SCESS) while the load demand is met through the power generated from solar photovoltaic (SPV) units. First, dynamical models of each subsystem of DCMGs such as the SPV system, BESS, and SCESS are developed to capture highly nonlinear behaviors of DCMGs under various operating conditions. The proposed nonlinear DI‐SMC is then designed for each power unit in DCMGs to ensure the desired voltage level at the common DC‐bus and appropriate power dispatch of different components to fulfill the load requirement of the DCMG. On the other hand, an energy management system (EMS) is designed to determine the set point for the controller with an aim of ensuring the power balance within DCMGs under various operating conditions where the overall stability is assessed using the Lyapunov theory. Simulation studies along with the processor‐in‐loop validation, including a comparative study with a proportional‐integral (PI) controller, verify the applicability and effectiveness of the EMS‐based DI‐SMC under different operating conditions of the DCMG.

Jéssica Pederneiras Moraes Rocha, Fabiano Salvadori, Lucas Vinícius Hartmann et al.

Abstract The constant growth of distributed energy resource (DER) in the electric power system (EPS) is a reality on account of some aspects, for example, technical, financial, environmental. The insertion of DERs can be positive, providing ancillary services, for example, harmonic mitigation, or negative, causing overvoltage, depending on the proper control and the characteristics of the grid. This paper proposes a pq‐based control strategy for distributed generation, wherein the studied system is composed by a photovoltaic DER and a three‐phase converter for processing the generated power and providing ancillary services (ASs) to a three‐wire EPS. The power control is based on the power balance between the grid and the converter. Besides supplying active and reactive power, the proposed strategy can provide ASs by controlling the grid currents from a pq transformation. Some advantages over other solution can be mentioned, such as reduced sensor number and instantaneous control response. In addition, neither additional harmonic‐extraction method nor a phase‐locked loop is required. To validate this study and theoretical considerations, simulation results are presented and evaluated. From tests in a downscaled laboratory setup, experimental results are also presented to verify the effectiveness of the proposed control strategy.

Jing Ma, Jiaming Zhang, Xucheng Wang et al.

Abstract A new transient stability control strategy for the Line‐Commutated‐Converter based High‐Voltage‐Direct‐Current (LCC‐HVDC) receiving‐end system based on the gradient of dynamic energy is proposed to deal with this problem. Firstly, in the whole process from fault occurrence to fault removal, a dynamic energy function representing the stability of the system is constructed. On this basis, considering the influence of Direct Current (DC) inverter side controller, the dynamic energy gradient expression under three‐phase and single‐phase short‐circuit fault scenarios is deduced in detail. The influence of control parameters on dynamic energy accumulation or consumption is analytically described. Then, the function term related to the inverter side controller is extracted from the dynamic energy gradient expression, the trigger pulse on the inverter side is controlled to keep the dynamic energy gradient of the DC port at the minimum. Finally, the hardware in the loop test is carried out on RT‐LAB. The test results show that in the process of receiving end fault, the DC port will inject dynamic energy to the receiving end system, making the system tend to be unstable. This method is able to reduce the dynamic energy accumulation rate of system and increase the critical clearing time of system.