A dc-ac converter for voltage-source converter (VSC)-HVdc technology has a significant influence on the performance of the entire power transmission system. This paper introduces a new dc-ac ...converter composed of submodules and series insulated-gate bipolar transistor (IGBT) switches. The basic idea of this hybrid solution is to shape the ac voltage by submodules but, per half cycle, reconnect them to different electrical points by IGBT switches. This concept can help to reduce the quantities of submodules, thereby reducing the energy storage requirement significantly. Another advantage is that the IGBT switches can be soft switched by utilizing the high controllability of the submodules. This brings extra benefit of power losses reduction. In this paper, the operating principle of this hybrid converter is explained. Its performances are also presented in detail and compared with those popular VSC dc-ac converters. The feasibility of the new concept is also verified by simulation and experimental results.
EPoPA (Extended-Power Pinch Analysis) is a technique to integrate Hybrid Renewable Energy Systems with Battery/Hydrogen storage. Power losses of the storage components due to their inefficiency have ...not been considered in EPoPA as of yet. This study proposes the MEPoPA (Modified Extended-Power Pinch Analysis) to modify EPoPA to consider the power losses in Hydrogen Storage System components. The MEPoCC (Modified Extended-Power Composite Curve) and MEPoSCT (Modified Extended-Power Storage Cascade Table) are introduced as the MEPoPA graphical and numerical tools to determine the minimum targets of Required External AC (Alternating-Current) and DC (Direct-Current) Electricity Sources as well as the Hydrogen Storage System component sizes. The sensitivity analysis is conducted to investigate the effect of various Hydrogen Storage System components, such as the inverter, converters, Fuel Cell, Electrolyzer and rectifier efficiencies, on the Hydrogen Tank Electricity Capacity and the Required External AC and DC Electricity Sources. The graphical and numerical results of the MEPoPA obtained from a case study showed that the system designed by MEPoPA requires 62.19% more outsourced electricity than the system designed by EPoPA. This means that the integration potential of the Renewable Energy System with Battery/Hydrogen storage is decreased with an increase in the power losses of the storage system.
•Construction of Modified Extended-Power Composite Curve.•Construction of Modified Extended-Power Storage Cascade Table.•Investigation of the various component efficiencies on the hydrogen tank capacity.•Optimal systems comparison with and without power losses.•Power losses decrease the integration potential of the battery/hydrogen system.
•Method builds on power flow solutions to compute power flows components.•Designed for meshed networks, adept at managing shunt elements.•Illustrated with 4 examples showcasing results obtained with ...the method.•Load can't rely solely on nearest power source, even if local generator meets demand.•Implementation in Python, code accessible on github.com.
To thoroughly analyze the conditions in power lines, transformers or loads, it is essential to have knowledge of their active and reactive power flow contributions from each power source. Understanding these contributions allows for a detailed analysis of the impact of active and reactive power flow contribution from each power source on active and reactive power losses in each network element, as well as the determination of power participation of each source to every load. This paper provides the necessary equations and an adequate procedure for calculating power flow contributions. The method is suitable for meshed network and considers shunt elements, avoiding problematic simplifications. Furthermore, it ensures impartiality towards any network user, making it well-suited for application in deregulated environments. By offering valuable information useful, this method supports the creation of transparent and non-discriminatory agreements between network operator and users.
•Examination of PV array configuration under partial shading conditions.•PV array configurations: Series (S), Series–Parallel (SP), Total-Cross-Tied (TCT), Bridge-Link (BL) and Honey-Comb (HC).•The ...shading loss, mismatch loss, and fill factor have been evaluated.•The best electrical configuration is investigated for different shading cases.
In the world, energy needs of people are met by fossil fuels. However, fossil fuels are getting depleted day by day and using of them causes negative effect on the environment. Moreover, energy demand of the world has increased in recent years. Hence, in order to meet the energy demand, especially solar or photovoltaic energy is widely used among the renewable energy sources. Photovoltaic cell directly convert solar energy into electricity. However, efficiency of photovoltaic cell is negatively affected by partial shading. Partial shading generally occurs on photovoltaic systems due to passing cloud, neighboring building, tree, etc. As a result of partial shading, produced power from photovoltaic system is less than the expected power value. One of the solutions of this problem is photovoltaic array configurations scheme. In this study, five different photovoltaic array configuration schemes: Series, Series-Parallel, Total-Cross-Tied, Bridged-Linked, and Honey-Comb, are carried out using 6 × 6 photovoltaic array under six different shading cases. Simulations of all shading cases are implemented using MATLAB/Simulink. In general, the obtained maximum power results under all partial shading cases show that Total-Cross-Tied configuration has the best performance according to other configurations. Furthermore, the obtained results have been compared in terms of shading loss, mismatch loss, and fill factor.
Improving the efficiency and sustainability of distribution networks (DNs) is nowadays a challenging objective both for large networks and microgrids connected to the main grid. In this context, a ...crucial role is played by the so-called network reconfiguration problem, which aims at determining the optimal DN topology. This process is enabled by properly changing the close/open status of all available branch switches to form an admissible graph connecting network buses. The reconfiguration problem is typically modeled as an NP-hard combinatorial problem with a complex search space due to current and voltage constraints. Even though several metaheuristic algorithms have been used to obtain-without guarantees-the global optimal solution, searching for near-optimal solutions in reasonable time is still a research challenge for the DN reconfiguration problem. Facing this issue, this article proposes a novel effective optimization framework for the reconfiguration problem of modern DNs. The objective of reconfiguration is minimizing the overall power losses while ensuring an enhanced DN voltage profile. A multiple-step resolution procedure is then presented, where the recent Harris hawks optimization (HHO) algorithm constitutes the core part. This optimizer is here intelligently accompanied by appropriate preprocessing (i.e., search space preparation and initial feasible population generation) and postprocessing (i.e., solution refinement) phases aimed at improving the search for near-optimal configurations. The effectiveness of the method is validated through numerical experiments on the IEEE 33-bus, the IEEE 85-bus systems, and an artificial 295-bus system under distributed generation and load variation. Finally, the performance of the proposed HHO-based approach is compared with two related metaheuristic techniques, namely the particle swarm optimization algorithm and the Cuckoo search algorithm. The results show that HHO outperforms the other two optimizers in terms of minimized power losses, enhanced voltage profile, and running time. Note to Practitioners -This article is motivated by the emerging need for effective network reconfiguration approaches in modern power distribution systems, including microgrids. The proposed metaheuristic optimization strategy allows the decision maker (i.e., the distribution system operator) to determine in reasonable time the optimal network topology, minimizing the overall power losses and considering the system operational requirements. The proposed optimization framework is generic and flexible, as it can be applied to different architectures both of large distribution networks (DNs) and microgrids, considering various types of system objectives and technical constraints. The presented strategy can be implemented in any decision support system or engineering software for power grids, providing decision makers with an effective information and communication technology tool for the optimal planning of the energy efficiency and environmental sustainability of DNs.
•As a practical solution, coordination between load restoration and repair tasks on damaged lines is modelled in the optimal switch placement problem for fast and optimal DSR after a hurricane. ...During the planning phase for optimal switch placement, repair times at each stage of network repair in the operational phase have been examined and modelled linearly to enhance network resilience in hurricane conditions.•Due to the fact that optimal switch placement enhances the performance of the distribution network in both emergency and normal conditions, new objective function has been introduced. Network resilience enhancement by incorporating cost models has been added to the objective function. This approach allows a comparison between the costs of losses and ENS under normal conditions with cost of ENS under hurricane conditions, and avoids the use of methods such as weighting and Pareto optimization.•In this article, instead of considering repair time as a random variable as commonly done in conventional optimal switch placement, a model has been developed to determine repair times more realistically. This model considers practical constraints such as depot location, access roads, amount of damage to the network, number of repair crews, prioritization of lines for repair, etc., in a linear fashion.•To implement proposed method simultaneously for normal and hurricane conditions to achieve optimal results, and due to the complexity of the problem arising from the consideration of various conditions and factors, we present a new MILP formulation for this large-scale problem.
Severe hurricanes can inflict significant damages in the order of several times the common network failures on both the distribution companies and consumers. Network reconfiguration and condition-based switching are the common actions for enhancing distribution network performance in both normal and emergency conditions. In this paper, a novel approach is presented for simultaneous improvement in resiliency, reliability, and power losses. A practical strategy is proposed by considering the coordination between load restoration and repair of damaged lines in optimal switch placement problems. The use of both remote-controlled switches (RCS) and manual switches (MS) as well as considering practical constraints related to line repair and load restoration leads to the increased number of decision variables and consequently the degraded performance of meta-heuristic methods to obtain the global optimum solutions, especially for larger scale networks. Therefore, the proposed approach uses the exact method of MILP to solve the optimization problem. In this context, the uncertainty related to damage status and repair time of lines during High-Impact Low-Probability (HILP) events is the main challenge in linear modeling of the problem for which new methods are provided in the study. The programming is coded in MATLAB and tested on a modified IEEE 33-bus network.
This paper presents the use of a recent developed algorithm inspired by the hunting mechanism of antlions in nature, called ant lion optimizer (ALO) algorithm for solving optimal reactive power ...dispatch (ORPD) problem considering a large-scale power system. The ORPD is formulated as a complex combinatorial optimization problem with nonlinear characteristic. The ALO algorithm is inspired from the hunting mechanism of antlions. One of the most interesting things in antlions is that they have a unique hunting behaviour and exhibit high capability of escaping the local optima stagnation. The ALO is used to find the set of optimal control variables of ORPD problem, such as generators terminal voltage, position of tap changers of transformers, and number of switchable capacitor banks. The performance and feasibility of the proposed algorithm are demonstrated through several simulation cases on IEEE 30-bus, IEEE 118-bus power systems and large-scale power system IEEE 300-bus power system. Comparison of obtained results with those reported in the literature shows clearly the superiority of ALO algorithm over other recently published algorithms in regards to real power losses and computational time, and hence confirmation of the efficiency of ALO algorithm in providing near-optimal solution.
•Decide the optimum location and size of DSTATCOM and DG.•Diagnosis the dynamic issues in power system under various environments.•DSTATCOM and DG are detected using loss sensitivity factor ...(LSF).•Optimum location is determined by using Dwarf Mongoose Optimization.•DMO decide the optimum size of DSTATCOM and DG.
This manuscript proposes a novel method to decide the optimum location and size of Distribution static compensator (DSTATCOM) and Distribution Generation (DG) are examined. For lessening the loss of power, voltage profile improvement and operation costs of system, the objective function is used under the constraints of equality and inequality. The aim of proposed method is diagnosis the dynamic issues present in the power system under various environments, like healthy conditions and unhealthy conditions. The primary location of both Distribution Generation and Distribution static compensator are detected by using the loss sensitivity factor (LSF). The final optimum location is determined by using Dwarf Mongoose Optimization (DMO) method. The DMO is used to decide the optimum size of Distribution Generation and Distribution static compensator. The aim of the proposed method is an integrated approach of loss sensitivity factor and Dwarf Mongoose Optimization to decide the optimum location and size of Distribution Generation and DSTATCOM for diminishing the loss of power, voltage profile improvement and operation cost. The Distribution Generation and DSTATCOM are simultaneously placed in radial DG. The LSF is used earlier to detect the optimum location of Distribution Generation and Distribution static compensator. The proposed system is performed in MATLAB or Simulink site and the performance of dynamic stability is tested with IEEE standard bench mark systems.
•Problems related to integration of EVs into the power system grid•Management strategies and policies to solve the problems•Comparison between the possible Management strategies and ...policies•Centralized coordination with interaction of renewables
Electric Vehicles (EVs) portray the important role in reduction of greenhouse gases and fuel utilization. The spike in number of EVs put large burden of power on grid system. This enormous power demand causes serious issues on the performance of power system and can leads to power failure. Optimal management strategies are required to alleviate such issues and to maintain the continuous supply of power. Due to integration of EVs various issues related to grid system are reviewed briefly in this paper. This paper reviews different management strategies to minimize the impacts of integration of EVs into grid system. Decentralized coordination helps to reduce load variability and stability issue of grid due to EVs but it needs accurate forecast of EVs travelling pattern. Central coordination reduces load variance, voltage variations, power losses, computational complexity and helps in determining the EVs charging location but it has less customer stratification. Integration of renewables reduces the burden on local grid, optimizes the production cost and enhances the charging capacity but it has intermittent power supply. EVs charging functioning reduce the power losses and waiting time but require huge investments. Public policies maximize the overall profit but it requires proper load managements. Among these methods it is found that centralized coordination can be more effective in solving EVs integration issues. The optimal power, energy capacity and location of EVs in centralized coordination can accurately found by optimizing the objective functions. Centralized coordination becomes more effective to resolve the EVs issues when addition of smooth power from renewables is included in the system.
PDF
