In this paper, improved single- and multi-objective Harris Hawks Optimization algorithms, called IHHO and MOIHHO, respectively are proposed and applied for determining the optimal placement of ...distribution generation (DG) in the radial distribution systems. Harris hawks optimizer (HHO) is a anew inspired meta-heuristic optimization technique that is mainly based on the intelligence behavior of the Harris hawks in chasing prey. The IHHO and MOIHHO are applied for determining the optimal size and location of DG with the aim of minimizing the total active power loss, reducing the voltage deviation (VD), and increasing the voltage stability index (VSI) with considering operational constraints of distribution system. In IHHO, the performance of conventional HHO algorithm is improved using the rabbit location instead of the random location. In MOIHHO, a developed grey relation analysis is applied for identifying the best compromise solution among the non-dominance Pareto solutions. To verify the effectiveness of the proposed algorithms, IEEE 33-bus and IEEE 69-bus radial distribution systems are used, and the obtained results are compared with the other optimization techniques which utilized for the same problem. The results prove the efficiency of the proposed algorithms in terms of best solutions obtained so far for the single- and multi-objective scenarios.
This paper provides an application of the hybrid Grey Wolf Optimization and Particle Swarm Optimization (GWO-PSO) method to reach a solution to the optimal reactive power dispatch (ORPD) problem in ...the scope of electric power networks. PSO is a swarm based meta-heuristic optimization algorithm whose target is to seek the best solution to a problem by moving particles in a specific exploration field. On the other hand, GWO is a meta-heuristic optimization technique which is inspired by grey wolves. In this article, GWO is hybridized with a PSO method to improve the progress of the GWO. There are two objectives minimized in this research study to improve the electric power network performance. They are: 1) power losses in the transmission systems, and 2) the deviation of voltages at the load buses. The problem of ORPD has many restrictions on the networks which must be considered during the solution. The hybrid GWO-PSO is proven as an effective optimization technique when seeking the global best solution to an optimization problem. The success of the introduced hybrid technique is verified utilizing more than one standard IEEE test system. A valuation to the introduced technique is performed by comparing it with other optimization techniques stated through the literature. The simulation results confirm that the usage of the hybrid GWO-PSO techniques causes an observable improvement in a wide scale of the electric power networks behavior.
It is imperative to distribution system operators to provide quantitative as well as qualitative power demand and satisfy consumers’ satisfaction. So, it is important to address one of the most ...promising combinatorial optimization problems for the optimal integration of power distribution network reconfiguration (PDNR) with distributed generations (DGs). In this regard, this paper proposes an improved equilibrium optimization algorithm (IEOA) combined with a proposed recycling strategy for configuring the power distribution networks with optimal allocation of multiple distributed generators. The recycling strategy is augmented to explore the solution space more effectively during iterations. The effectiveness of the proposed algorithm is checked on 23 standard benchmark functions. Simultaneous integration of PDNR and DG are carried out considering the 33 and 69-bus distribution test systems at three different load levels and its superiority is established. Verification of the proposed technique on large scale distribution system with a variety of control variables is introduced on a 137-bus large scale distribution system. These simulations lead to enhanced distribution system performance, quality and reliability. While, the integration represents a challenge for complexity and disability to achieve optimal solutions of the considered problem especially for multi-objective framework. To solve this challenge, a multi-objective function is developed considering total active power loss and overall voltage enhancement with respecting the system limitations. The proposed algorithm is contrasted with harmony search, genetic, refined genetic, fireworks, and firefly optimization algorithms. The obtained results confirm the effectiveness and robustness of the proposed technique compared with the competitive algorithms.
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•A newly proposed meta-heuristic IEOA is introduced in this work.•The proposed IEOA is applied on 23 standard benchmark functions.•The proposed technique verification is compared with other previous techniques.•The suggested IEOA is validated on three distribution systems.•The findings of simultaneous PDNR/DG allocation show the IFOA effectiveness.
The nonresonant single-phase dual-active-bridge (NSDAB) dc-dc converter has been increasingly adopted for isolated dc-dc power conversion systems. Over the past few years, significant research has ...been carried out to address the technical challenges associated with modulations and controls of the NSDAB dc-dc converter. The aim of this paper is to review and compare these recent state-of-the-art modulation and control strategies. First, the modulation strategies for the NSDAB dc-dc converter are analyzed. All possible phase-shift patterns are demonstrated, and the correlation analysis of the typical phases-shift modulation methods for the NSDAB dc-dc converter is presented. Then, an overview of steady-state efficiency-optimization strategies is discussed for the NSDAB dc-dc converter. Moreover, a review of optimized techniques for dynamic responses is also provided. For both the efficiency and dynamic optimizations, thorough comparisons and recommendations are provided in this paper. Finally, to improve both steady-state and transient performances, a combination approach to optimize both the efficiency and dynamics for an NSDAB dc-dc converter based on the reviewed methods is presented in this paper.
The tilt angle and row spacing are crucial parameters in the planning and design of Photovoltaic (PV) power plants. This study, aiming to minimize the Levelized Cost of Energy (LCOE) per unit land ...area, optimized the tilt angle and row spacing for fixed monofacial and bifacial PV arrays. To accurately reflect the effect of tilt angle and row spacing on the objective, algebraic expressions for calculating the front and rear sides irradiance of PV arrays considering tilt angle, row spacing, and shading effect in multi-row scenarios have been established. Based on the voltage-power (UP) characteristics of the PV array under local shading, a simple calculation method for the output power of the PV array was established under Inter-Row Shading (IRS) considering electrical characteristic. Multiple scenarios were established based on practical application conditions, and the Nelder-Mead optimization algorithm was employed to find solutions. The results demonstrate that the optimized LCOE is not only 0.75%–3.06% lower than that of the winter solstice rule (Standard rule) but the electricity generation per unit land area is also increased by 22.16% ∼ 50.79%. Additionally, this study provides a detailed analysis of various factors influencing the selection of tilt angle and row spacing for PV arrays. And comparing the differences and similarities in the impact of these factors on monofacial and bifacial PV modules. These contributions aim to provide a more comprehensive understanding and practical approach to optimizing the spatial arrangement of PV arrays, addressing key challenges in the field.
•Algebraic expression of PV arrays irradiance calculation under IRS at any tilt angle, row spacing.•PV arrays power calculation under IRS is simpler by analyzing the UP curve under local shading.•Optimization model for the spatial arrangement of PV arrays considering IRS's impact on power.•Improvement more than 22.16% in lifecycle electricity by optimal spatial arrangement in a real case.
•The distribution network reconfiguration is a crucial method for improving network performance.•Reducing power loss is an essential method to improve the performance of distribution ...network.•Increasing the voltage value is an essential method to improve the performance of distribution network.•The Selective Particle Swarm Optimization is an effective method for decreasing power loss and improving the voltage value in distribution network.
The electricity provider incurs a high costs and investments to transfer the electrical power to customers in the distribution network. Hence, the reliability of the distribution network (DN) is particularly important in the lives of customers. A distribution system faces many issues due to its direct impact of the voltage profile (VP) and power losses (PL) problems. The aim of this study is to provide an effective scheme to address the of VP and PL problems. In this research, a Selective Particle Swarm Optimization (SPSO) algorithm was used to find combination of switches to enhance VP and reduce PL. The proposed method has been tested in the distribution network system, 125-buses Sigeri-Makassar Indonesia. There are three kinds of considered load scenarios, namely: nominal load; active power load increase; active and reactive power load increase. The research results indicated that the VP of the system can increased from 0.918 pu to be 0.922 pu and decreased PL from 0.6482 MW to be 0.6052 MW; the VP can increased from 0.895 pu to be 0.901 pu and reduced PL from 1.0469 MW to be 0.97532 MW, the VP can increased from 0.895 pu to be 0.900 pu and reduced PL from 1.1929 MW to be 1.0758 MW, for scenarios 1, 2 and 3, respectively. The simulation results showed that the proposed method provides optimal solution, which can enhance the VP and reduce PL. This is indicated that the proposed method is an effective strategy for enhancing voltage stability and solve PL problem.
Centralized inverter technology is one of the most common architectures of the PV installation, which interfaces a large number of PV panels that configured in series-parallel (SP) combination to the ...grid. However, the power generated from centralized inverter architecture based on SP array topology is significantly reduced under the non-uniform aging condition. Non-uniform aging of PV panels is a common problem in the PV generation plants, as they often operate under harsh outdoor environmental conditions for a long service period. Due to the elevated price of replacing aged PV panels with new ones, it is preferable to improve the power extracted from aged PV systems. This paper proposes a circuit-based topology known as current collector optimizer (CCO) topology to enhance the performance of centralized inverter technology under the uneven aging condition of PV modules. According to the results, the maximum power extracted from the non-uniform aging PV array is substantially increased by using the CCO topology compared to the conventional SP array topology with bypass diodes. With CCOs, the PV array characteristics have a unique maximum power point (MPP) which can be easily followed by a simple MPP tracking algorithm, subsequently, the CCO topology does not suffer from misleading power losses. The proposed topology requires offline rearrangement of aged modules to obtain the optimum power if only the degradation rate of short-circuit current is used to assess the aging process. Furthermore, the CCO topology operates close to optimum power if the degradation rate of open-circuit voltage is taken into account.
•CCO topology is used to enhance energy harvest from non-uniform aging PV modules.•CCO topology does not suffer from misleading power losses.•Optimum power is obtained if SC current is used to assess the aging process.•Close to optimum power is achieved when SC current and OC voltage are used to evaluate the aging process.
The purpose of this work was to investigate a new nano-additive for improved internal combustion engine oils designed for increased fuel economy and a cleaner environment. The friction and wear ...characteristics of nano-lubricants containing hybrid nano-materials of Al2O3 and TiO2 were been evaluated under reciprocating test conditions to simulate a piston ring/cylinder liner contact. Al2O3/TiO2 nanoparticles were suspended in a commercially available lubricant in various concentrations. The Al2O3 and TiO2 nanoparticles had sizes of 8–12nm and 10nm, respectively. The morphology and microstructure of the tribofilms produced during frictional contact were investigated via FE-SEM, EDS and a 3-D surface profiler. In the best case, there was a reduction of frictional power losses for the simulated piston ring assembly by 40–51% compared to a commercially available lubricant. The nano-additive composition in that case was 0.05wt% Al2O3+0.05wt% TiO2. Moreover, the wear rate of piston ring decreased by 17% after a sliding of 50km due to the delamination of Al2O3 and TiO2 nanoparticles on worn surfaces. In that case, they acted as a solid lubricant to reduce both wear and scuffing. These results present a promising and straightforward approach to automotive fuel economy and an increased life span for engine parts.
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•The frictional power losses were reduced by 40–51% using hybrid nano-lubricants.•The wear rate of the ring decreased by 17% due to the delamination mechanism.•The results showed that hybrid nano-lubricants improve the scuffing resistance.•These results present a promising approach to automotive fuel economy.
•Analytical efficiency model considering power losses in meshing and bearings.•Convergence of the results obtained by calculations and by testing the prototype.•High efficiency of the transmission at ...nominal load (90–96%).•Power loses in rolling bearings are several times greater than in meshing.
The aim of the article is to investigate the efficiency of the novel eccentric rolling transmission, which is a simplification of the cycloidal reducer, with parallel but not overlapping shaft axes. In this paper, a kinematic and load distribution analysis are presented with a view to determining the forces and rotational speeds necessary for efficiency calculation. The developed efficiency model involved power losses in rolling bearings, at meshing, as well as churning and windage power losses. For the verification, a transmission prototype with a 10:1 gear ratio and a dedicated test stand were designed and built. The results of the research showed that most substantial power losses occurred in the bearings and were several times greater than the losses associated with friction between the active surfaces of its main components. The transmission efficiency improved with increasing load and decreased with increasing rotational speed, reaching a maximum of 96% at nominal torque. The proposed model allows predicting the efficiency of the transmission at the stage of its design, which can further facilitate the optimization of the transmission parameters considering expected operational conditions.
In 2021, the world's total installed capacity of generation units based on renewable energy sources (not including hydropower) amounted to about 1674 GW: over 825 GW and 849 GW of wind and solar ...power plants were installed respectively. The growing of the installed capacity of these distributed generators is a response to the increasing the power consumption, global environmental issues and has also become possible due to the development of technology in field of power semiconductor devices. However, on the way of large-scale implementation of distributed generators based on renewable energy sources, traditional electric power system meets new challenges to ensure the reliability and sustainability of new electric power systems with renewable energy sources. In particular, distributed generators change processes in the electric power system, impact to the parameters and power balance, change the magnitude and direction of power flow and short-circuit current, which determines the need to update the settings of the relay protection and automation systems of traditional electric power system and to coordinate their operation with automatic control systems of installed distributed generators. The above-mentioned tasks form a number of scientific research directions, one of which is a task of determining optimal size and location of distributed generators. The main purpose of this optimization task is to reduce power losses, operating and total electricity cost, improve the voltage profile, etc. In addition, the correct and reasonable placement of distributed generators defines an effective planning of the operating modes of electric power system and power plants (especially based on renewable energy sources, the operating modes of which depend on weather conditions and can be sharply variable).
The paper highlighted the impacts of distributed generators on power losses, the voltage level, maintaining the power balance and the possibility of participating in the frequency regulation, and short-circuit current in power system. The optimization criteria, the main limiting conditions, as well as methods for solving this optimization problem are considered. This review will help the System operators and investing companies, especially in Russia, to form the main aim, objective function and constraints that will aid to meet their load demand at minimum cost and to choose from the options available for optimization of location and capacity of distributed generators.
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