This paper investigates the strategic placement of capacitor banks in the distribution network of Gračanica, with a specific focus on the medium-voltage feeder Grades. The primary objective is to ...optimize voltage profiles, minimize power losses, and enhance the overall performance of the distribution network. The significance of this research lies in its thorough examination of optimal capacitor placement within the medium-voltage (MV) branch of distribution networks, specifically considering the intricate interplay between capacitor banks and MV branch components, underlining the necessity for informed decisions in the context of distributed generators (DG) integration to enhance overall network performance. The study further investigates the impact of integrating DGs on these objectives on capacitor placement in the MV feeder. Employing the DIgSILENT PowerFactory software tool for modelling the MV feeder and utilizing a genetic algorithm for capacitor placement optimization, the study underscores the robustness of this approach in handling various conditions and seeking optimal solutions. Simulation results demonstrate that strategically placing capacitor banks and integrating DGs can significantly improve the voltage profile and reduce power losses within the distribution system. The findings of this research support 2MVA of concentrated DGs at the middle of the line as the most efficient and most economically beneficial situation on the medium-voltage feeder Grades study case and contribute valuable insights, serving as a reference for future studies on optimal capacitor placement.
The load sharing impact on the efficiency of spur gears with modified profile was assessed in this work. The aim was to analyse the influence of the profile modifications on the load sharing, which ...also considers the effect of the torque level on the system deflections, and how these load sharing variations affected the system efficiency. Due to the frictional effect importance on power losses, in the operating conditions considered, sliding friction between teeth in presence of lubricant was studied in this proposal. The results established that tip relief improves the efficiency of the system due to the reduction of effective contact ratio. Moreover, there is a tip relief which makes optimal the efficiency in specific operating conditions, corresponding to the unit value of the effective contact ratio. Thus, the main conclusion of this work is that the tip relief which makes optimal the efficiency coincides with the theoretical dynamic optimum of the transmission.
The usage of too many sizeable capacitors significantly increases the volume and cost of the modular multilevel converter (MMC), and limits its spread in medium- and high-voltage applications. By ...adding a buck-type active power filter (APF) circuit into a particular MMC topology of which each phase multiplexes one submodule (SM), a modified MMC (APF-M3C) topology, which inherently has the ability to suppress capacitor voltage fluctuations and decrease the power losses compared with conventional MMC topology, is proposed in this article. Both the SM capacitor voltage ripples, which can be reduced up to 50% of original value and are related to the SM capacitance, and the arm currents, which are related to SM power losses, are calculated in detail. Its topology, and operating principle is presented in detail, and a novel modulation method for the APF-M3C topology are proposed. In addition, an improved control method for the voltage balancing is also recommended to further reduce system cost and power losses. Finally, the APF-M3C topology and traditional MMC simulation and experimental platforms were built. Simulations and experimental results verify the feasibility and effectiveness of the APF-M3C topology and control strategy by comparing with the conventional MMC.
The grasshopper heuristic optimisation algorithm (GOA) is one of the newest heuristic techniques. It attempts to imitate locust's behaviour in solving different problems. In this paper, first, ...optimal location and size of fixed capacitor banks on distribution systems have been obtained using the GOA. Determination of the optimal number of capacitor banks and their optimal locations and sizes represent one of the major challenges facing distribution system operators. Therefore, second, a combined power loss sensitivity and GOA technique has been introduced to obtain the optimal number, location and size of the capacitor banks on distribution systems. Third, a proposed technique for optimal placement of fixed and switched capacitor banks considering daily load variations is introduced. Finally, a new technique of combined rough set theory and GOA is proposed to minimise daily switching of the capacitor banks and minimise daily power losses. Four test systems with different sizes and complexities are considered to evaluate the proposed techniques which are the 33, 69, 85 and 141-bus systems. To clarify the validation and effectiveness of the proposed solution techniques, the obtained results have been compared with other previously used solving techniques. The obtained results demonstrate the accuracy and effectiveness of the introduced techniques.
•TCT, hybrid SP-TCT, BL-TCT, BL-HC and NS PV array configurations are investigated.•Investigation using P-V curve, power losses, FF, PR and shade dispersion is done.•Performance of NS configuration ...is compared with the existing and hybrid configurations.•Prosed NS configuration of PV array is found better for most of shading cases.
In this paper, a comprehensive study is carried out on the solar photovoltaic (PV) array topologies under diagonally shading scenario. The aim of extensive analysis is to investigate the power mismatch losses in PV array under non-uniform irradiations. The partial shading affects not only power but also exhibits extreme non-linearity along with multiple maximum power points on P-V and I-V characteristics. The investigation is based on designing of the optimal layout of PV modules in a array to extract maximum power under partial shading conditions (PSCs). In this context, a novel structure (NS) of PV array is designed and compared with the classical configurations such as total cross-tied (TCT), hybrid series-parallel-total cross-tied (SP-TCT), bridge link-total cross tied (BL-TCT) and bridge link-honey comb (BL-HC) under considered shadowing scenario. The modeling of all the considered PV array configurations has been done in MATLAB/Simulink environment. The performance of proposed NS configuration is found superior for some cases of shading effect. NS configuration of PV array has minimum power losses and improved fill factor (FF) as compared to others under PSCs.
Transactive energy management (TEM) in smart grids is a promising approach for enhancing the participation of consumers in managing their energies and developing decentralized energy market models ...using peer-to-peer (P2P) transactions. The present paper designs and models a fully decentralized P2P energy market considering the technical constraints of the physical electricity network to redesign electricity markets as consumer-centric markets. As the sellers and buyers trade energy via the electricity grid, allocating power losses and transaction fees to players in P2P transactions is of utmost significance. The proposed market allows prosumers to engage directly in bilateral energy trading without requiring intermediaries. In addition to local P2P markets, the buyer prosumers can purchase energy from the upstream market and participate in the demand response (DR) program during hours of local generation shortage. A fairness index is applied to evaluate the players’ satisfaction with fairness and participation in the proposed market. Finally, an alternating direction method of multipliers (ADMM) is utilized to clear the proposed decentralized market. Numerical studies are performed on a standard IEEE 13-bus distribution network with multiple prosumers. The simulation results verify the effectiveness and feasibility of the proposed decentralized market and its clearing approach.
•Fully decentralized P2P energy market with loss and transaction fee consideration.•Models for power loss and transaction fee allocation, assessing performance.•Penalty to minimize network losses and encourage local transactions.•Prosumers’ ability to access the upstream market and participate in DR programs.
•The paper aims to find the optimal location and size of DG in distribution system.•Quasi-Oppositional SIMBO-Q (QOSIMBO-Q) is applied for solution.•Results show improved power loss, voltage stability ...and voltage profile.•Performance of QOSIMBO-Q has been compared with other soft computing techniques.•Performance of QOSIMBO-Q revealed to be more encouraging to solve the problem.
Optimal allocation of Distributed Generations (DGs) is one of the major problems of distribution utilities. Optimum locations and sizes of DG sources have profoundly created impact on system losses, voltage profile, and voltage stability of a distribution network. In this paper Quasi-Oppositional Swine Influenza Model Based Optimization with Quarantine (QOSIMBO-Q) has been applied to solve a multi-objective function for optimal allocation and sizing of DGs in distribution systems. The objective is to minimize network power losses, achieve better voltage regulation and improve the voltage stability within the frame-work of the system operation and security constraints in radial distribution systems. The limitation of SIMBO-Q algorithm is that it takes large number of iterations to obtain optimum solution in large scale real systems. To overcome this limitation and to improve computational efficiency, quasi-opposition based learning (QOBL) concept is introduced in basic SIMBO-Q algorithm. The proposed QOSIMBO-Q algorithm has been applied to 33-bus and 69-bus radial distribution systems and results are compared with other evolutionary techniques like Genetic Algorithm (GA), Particle Swarm Optimization (PSO), combined GA/PSO, Teaching Learning Based Optimization (TLBO) and Quasi-Oppositional Teaching Learning Based Optimization (QOTLBO). Numerical studies represent the effectiveness and out-performance of the proposed QOSIMBO-Q algorithm.
This study focuses on mitigating power losses within unbalanced radial distribution networks by employing transformer modeling and network reconfiguration. The process commences with load flow ...analysis, utilizing a simplified three-phase load flow method tailored for unbalanced radial distribution networks (URDNs) featuring voltage-dependent loads. Using vector data and fundamental electric circuit analysis, the algorithm efficiently resolves voltage magnitude equations, conserving memory resources, and accurately identifies buses and branches downstream from a designated bus. This method circumvents the repetitive identification issues inherent in conventional forward-backward sweep approaches. The proposed methodology demonstrates robust convergence when applied to URDNs with realistic resistance/reactance ratios and has been rigorously tested on 19-bus and 25-bus unbalanced radial distribution networks. Evaluation criteria encompass CPU execution time and iteration benchmarks. Leveraging empirical formulas, this study achieves optimal designs characterized by improved voltage profiles and reduced power losses. An asymmetric power flow program is employed to compare bus voltages and system power losses, facilitating informed switch operation decisions and allowing for the elimination of feeder sectionalizing switch actions. This approach streamlines CPU processing time by eliminating switching procedures and has been successfully validated using 19-bus and 25-bus URDN samples. This work distinguishes itself through its efficiency, necessitating fewer switching operations when compared to existing methodologies.
•Efficient resolution of voltage magnitude equations with minimized memory usage.•Satisfactory convergence in realistic network conditions, resulting in tangible power loss reductions.•Simplification of network operation, making the practical approach for real-world implementation.
•Ni3Fe-5wt.%Cr soft magnetic composites was obtained by mechanical alloying and spark plasma sintering.•By milling Cr became more homogeneously distributed in the Ni3Fe matrix.•The electrical ...resistivity is increasing as the Cr is added and the mixture is milled.•The losses of Ni3Fe-5wt.%Cr are reduced after 60 min of milling.•Cr clusters size and distribution are responsible of the frequency behaviour of Ni-Fe-Cr nanocrystalline materials.
Soft magnetic composite powders were obtained by mechanical alloying using as the main component nanocrystalline Ni3Fe powder, produced by mechanosynthesis, and 5 wt% of Cr powder. For the composite powder synthesis short milling times up to 60 min were used. The SMC were compacted by spark plasma sintering (SPS) method at a temperature of 700 °C. By X-ray diffraction and energy dispersive X-ray spectroscopy the incorporation and the distribution of Cr in Ni3Fe particles was studied. It was found that adding 5 wt% Cr to Ni3Fe particles increases the electrical resistivity of the samples. DC and AC magnetic characteristics have been tested and the properties of the compacts in alternative magnetic fields indicates the reduction of power losses as the milling time increases. For the composite powder obtained by 40 and 60 min milling times, a better stability of the permeability was recorded, up to a frequency of 500 Hz at an induction field of 0.05 T.
In this work a design methodology and key considerations for high-voltage and highly-integrated switched-capacitor power converters is presented. The design methodology describes the power losses in ...high-voltage applications, where switching losses and gate-driver losses start becoming dominant compared to fully integrated, low voltage and low power applications. The design methodology is applicable for any highly-integrated switched-capacitor topology. To verify the design methodology a 48 V-12 V ladder switched-capacitor power converter in a 180 nm SOI BCD process, with external capacitors is implemented. The floating gate-drivers and a clock controller responsible for the power switch control are also presented. The peak efficiency of the proposed power converter is measured to be 93.5 %, and 24.5 W maximum output power, resulting in a power density of 23 W/cm<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula>.
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