Showing papers on "Power-flow study published in 2020"

Grasshopper optimization algorithm based two stage fuzzy multiobjective approach for optimum sizing and placement of distributed generations, shunt capacitors and electric vehicle charging stations

Abstract: In this paper a two stage Grasshopper Optimization Algorithm (GOA) based Fuzzy multiobjective approach is proposed for optimum sizing and placement of Distributed Generations (DGs), Shunt Capacitors (SCs) and Electric Vehicle (EV) charging stations for distribution systems. In the first stage Fuzzy GOA approach is used for optimum sizing and allocation of DGs and SCs for improving the substation power factor, real power loss reduction and voltage profile improvement of the distribution system. In the second stage distribution system integrated with DGs and SCs is considered and fuzzy GOA approach is used for identifying optimum locations for EV charging stations and number of vehicles at the charging stations. EV battery charging load models are developed from the Lithium ion battery charging characteristic curves for load flow analysis. Simulation results are shown to show the advantages of fast converging properties of GOA over GA and PSO techniques. Simulation results are demonstrated on 51 bus and 69 bus distribution networks to show the advantages of proposed methodology compared to conventional objective based simultaneous optimization approach. The effect of EV load growth and the effect of uncertainties in DGs and distribution system load are shown on the distribution system performance.

SimBench—A Benchmark Dataset of Electric Power Systems to Compare Innovative Solutions Based on Power Flow Analysis

Abstract: Publicly accessible, elaborated grid datasets, ie, benchmark grids, are well suited to publish and compare methods or study results Similarly, developing innovative tools and algorithms in the fields of grid planning and grid operation is based on grid datasets Therefore, a general methodology to generate benchmark datasets and its voltage level dependent implementation is described in this paper As a result, SimBench, a comprehensive dataset for the low, medium, high and extra-high voltage level, is presented Besides grids that can be combined across several voltage levels, the dataset offers an added value by providing time series for a whole year as well as future scenarios In this way, SimBench is applicable for many use cases and simplifies reproducing study results As proof, different automated algorithms for grid planning are compared to show how to apply SimBench and make use of it as a simulation benchmark

On the Efficiency in Electrical Networks with AC and DC Operation Technologies: A Comparative Study at the Distribution Stage

Abstract: This research deals with the efficiency comparison between AC and DC distribution networks that can provide electricity to rural and urban areas from the point of view of grid energy losses and greenhouse gas emissions impact Configurations for medium- and low-voltage networks are analyzed via optimal power flow analysis by adding voltage regulation and devices capabilities sources in the mathematical formulation Renewable energy resources such as wind and photovoltaic are considered using typical daily generation curves Batteries are formulated with a linear representation taking into account operative bounds suggested by manufacturers Numerical results in two electrical networks with 024 kV and 1266 kV (with radial and meshed configurations) are performed with constant power loads at all the nodes These simulations confirm that power distribution with DC technology is more efficient regarding energy losses, voltage profiles and greenhouse emissions than its AC counterpart All the numerical results are tested in the General Algebraic Modeling System widely known as GAMS

An Improved Backward/Forward Sweep Power Flow Method Based on a New Network Information Organization for Radial Distribution Systems

Abstract: This paper presents a load flow algorithm based on the backward/forward sweep principle, flexible with network topology changes, with an improvement in ensuring a minimum number of searching for connections between nodes in the calculation sequence in the forward and the backward sweep, by organizing the radial distribution system information into a main line and its derivations. The proposed load flow analysis is easy to implement and does not require the use of any complex renumbering of branches and nodes, or any matrix calculation, with the only use of linear equations based on Kirchhoff’s formulation.

Analysis of Optimal Deployment of Several DGs in Distribution Networks Using Plant Propagation Algorithm

Abstract: In recent years, the substantial upsurge of electricity demand has directly impacted the performance of the distribution networks concerning the active power losses and voltage drops. In such circumstances, the distributed generators (DGs) could uphold these concerns if they are optimally deployed in terms of sizing and placement. For this reason, in current research, the optimal deployment of DGs has been proposed with the plant propagation algorithm (PPA) to simultaneously maximize the total active power loss reduction and to upgrade the magnitude of the minimum bus voltage. Alongside, the authors have examined four rounds of DGs. In that context, the optimal deployment of one DG is investigated in the first round. In each succeeding round, the number of DGs is increased: in the second round, this investigation is carried out for two DGs, for three DGs in the third round, and finally, for four DGs in the fourth round of the investigation. The effectiveness of the proposed PPA has been tested on IEEE 33 and 69-bus test networks in the load flow analysis, and results are compared with the standard optimization algorithms. Thereafter, a post deployment economic assessment based on loss calculation has been undertaken out as well. The ANOVA test has also been performed for statistical evaluation of standard algorithms. The simulation results exhibit that the proposed algorithm outdo other algorithms both technically and economically. It has been seen that as the deployment of DGs is increased, the total active power losses and voltage drops are also reduced. In terms of economic assessments, the total cost decreases with the increased deployment of DGs in IEEE 33-bus test network, whereas, the total cost increases with the increased deployment of DGs in IEEE 69-bus test network.

Comparison of Classical and Smart Transformers Impact on MV Distribution Grid

Abstract: In last years, the electrical systems are changed from centralized to distributed energy generation. Nowadays, the distributed generation systems consist of many renewable energy sources (RESs) and active loads, connected to the grid by the power electronics converters (PECs). As a result, more often the PECs with novel functionalities like harmonic elimination, voltage sags compensation, grid stability improvement etc. are required. One of the promising solutions for distributed generation system, which allows improve the delivered power is a smart transformer (ST). It is able to replace the classical MV/LV transformer, where additional functionalities are necessary to provide the higher energy quality. Additionally, the ST is characterized by lower weight/volume and provides easy integration of AC and DC sub-grids. Therefore, in this paper, the modelling problem of a modern MV grid with classical and smart transformers have been described. Moreover, the comprehensive simulation analysis of the MV grid was performed, in which different functionalities of ST were considered. The advantages of ST over classical transformer are compared and the impact of ST functionalities on the MV grid is presented, taking into account the currents/voltages distortions in LV side, symmetrization process and voltage support in MV distribution grid as well as the transmission power losses.

Vortex Search Algorithm for Optimal Power Flow Analysis in DC Resistive Networks With CPLs

Abstract: This express brief addresses the optimal power flow (OPF) analysis in direct-current (DC) resistive networks with constant power loads (CPLs). The OPF employs the vortex search algorithm (VSA) in conjunction with a power flow method based on successive approximations by proposing a master-slave optimization methodology. The VSA is a powerful numerical optimization method that works with Gaussian distributions and variable radius for intensive exploration and exploitation in the solution space of the OPF problem. The power flow based on successive approximations allows evaluating the objective function by solving the non-convex equality constraints related to the power balance equations. Numerical implementations in two distribution DC feeders with 10 and 21 nodes show that the proposed approach attains the optimal solution reported by convex approximations, sequential quadratic models and nonlinear optimization methods. All the simulations have been conducted in MATLAB software.

Combined Electric and Heat System Testbeds for Power Flow Analysis and Economic Dispatch

Abstract: In combined electric and heat systems, selecting a suitable testbed for power flow analysis or economic dispatch is not easy: a large number of existing testbeds are not open-source, while others are difficult to be reused by other researchers due to the particularity of system scale, topology, and data. In this paper, we present three open-source testbeds with different scales based on practical combined electric and heat systems. To satisfy researchers' specific demands on the system topology and data, we also discuss how to modify testbeds based on existing topologies and data. Researchers can use the testbeds presented in this paper to test their innovative methods for power flow analysis and economic dispatch, and can also design their own testbeds based on the methodology in this paper, using published topologies and data.

Triangular Matrix Formulation for Power Flow Analysis in Radial DC Resistive Grids With CPLs

Abstract: This brief briefly addresses the problem of power flow solution for direct-current (dc) networks with radial configuration and constant power loads (CPLs). It proposes a novel iterative method based on the upper triangular relationship between nodal and branch currents, it also uses a primitive impedance matrix. The main advantage of this method lies in the possibility of avoiding inversions of non-diagonal matrices, which allows its convergence to be improved in terms of the number of iterations and processing times required in comparison to classical admittance-based methods. Three different radial dc resistive networks composed by 21, 33, and 69 nodes are employed to validate the effectiveness of the proposed power flow solution method. For comparison purposes, the Newton–Raphson method, and also successive approximations and Taylor-based approaches are implemented. All simulations have performed in MATLAB software.

Assessing the criticality of interdependent power and gas systems using complex networks and load flow techniques

Abstract: Gas and electricity transmission systems are increasingly interconnected, and an attack on certain assets can cause serious energy supply disruptions, as stated in recommendation (EU) 2019/553 on cybersecurity in the energy sector, recently approved by the European Commission. This study aims to assess the vulnerability of coupled natural gas and electricity infrastructures and proposes a method based on graph theory that incorporates the effects of interdependencies between networks. This study is built in a joint framework, where two different attack strategies are applied to the integrated systems: (1) disruptions to facilities with most links and (2) disruptions to the most important facilities in terms of flow. The vulnerability is measured after each network attack by quantifying the unmet load (UL) through a power flow analysis and calculating the topological damage of the systems with the geodesic vulnerability ( v ¯ ) index. The proposed simulation framework is applied to a case study that consists of the IEEE 118-bus test system and a 25-node high-pressure natural gas network, where both are coupled through seven gas-fired power plants (GFPPs) and three electric compressors (ECs). The methodology is useful for estimating vulnerability in both systems in a coupled manner, studying the propagation of interdependencies in the two networks and showing the applicability of the v ¯ index as a substitute for the UL index.

Metaheuristic Optimization Methods for Optimal Power Flow Analysis in DC Distribution Networks

Abstract: In this paper is addressed the optimal power flow problem in direct current grids, by using solution methods based on metaheuristics techniques and numerical methods. For which was proposed a mixed integer nonlinear programming problem, that describes the optimal power flow problem in direct current grids. As solution methodology was proposed a master–slave strategy, which used in master stage three continuous solution methods for solving the optimal power flow problem: a particle swarm optimization algorithm, a continuous version of the genetic algorithm and the black hole optimization method. In the slave stages was used a methods based on successive approximations for solving the power flow problem, entrusted for calculates the objective function associated to each solution proposed by the master stage. As objective function was used the reduction of power loss on the electrical grid, associated to the energy transport. To validate the solution methodologies proposed were used the test systems of 21 and 69 buses, by implementing three levels of maximum distributed power penetration: 20%, 40% and 60% of the power supplied by the slack bus, without considering distributed generators installed on the electrical grid. The simulations were carried out in the software Matlab, by demonstrating that the methods with the best performance was the BH/SA, due to that show the best trade-off between the reduction of the power loss and processing time, for solving the optimal power flow problem in direct current networks.

A Comparative Study on Power Flow Methods for Direct-Current Networks Considering Processing Time and Numerical Convergence Errors

Abstract: This study analyzes the numerical convergence and processing time required by several classical and new solution methods proposed in the literature to solve the power-flow problem (PF) in direct-current (DC) networks considering radial and mesh topologies. Three classical numerical methods were studied: Gauss–Jacobi, Gauss–Seidel, and Newton–Raphson. In addition, two unconventional methods were selected. They are iterative and allow solving the DC PF in radial and mesh configurations. The first method uses a Taylor series expansion and a set of decoupling equations to linearize around the desired operating point. The second method manipulates the set of non-linear equations of the DC PF to transform it into a conventional fixed-point form. Moreover, this method is used to develop a successive approximation methodology. For the particular case of radial topology, three methods based on triangular matrix formulation, graph theory, and scanning algorithms were analyzed. The main objective of this study was to identify the methods with the best performance in terms of quality of solution (i.e., numerical convergence) and processing time to solve the DC power flow in mesh and radial distribution networks. We aimed at offering to the reader a set of PF methodologies to analyze electrical DC grids. The PF performance of the analyzed solution methods was evaluated through six test feeders; all of them were employed in prior studies for the same application. The simulation results show the adequate performance of the power-flow methods reviewed in this study, and they permit the selection of the best solution method for radial and mesh structures.

Steady-State Scenario Development for Synthetic Transmission Systems

Abstract: The development of synthetic transmission networks has equipped the power system research community with public test cases that can be used and shared freely. As the synthetic electric grid power flow model only represents a one-time snapshot of the system, this paper proposes a methodology of developing scenarios that can reflect a wide spectrum of system operating conditions. The general process of determining load and generation levels, planning scheduled outages, and dispatching generators is discussed. Techniques that are commonly used to aid the convergence of power flow of scenario case are also provided.

Improvement of Power Flow Capability By Using An Alternative Power Flow Controller

Abstract: An improved version of power flow-controller (PFC) which is based on multi-winding transformer (MWT) is presented in this paper. The objective of this article is to control the power flow in a power-line to alleviate overload in a heavily loaded system and increase power flow of an under loaded line. The novelty of multi-winding transformer based power-flow controller is the use of unequal voltage ratio in the tap-changer windings of MWT with bi-directional switches to provide a compensating voltage required to achieve the desired power flow. This new model drastically increases the number of compensating points to make it more compact with higher flexibility. It aims to utilize the full potential of a line (bound by its thermal limits) to contribute in power flow by providing several times higher resolution with limited number of switches and reduced amount of copper and iron volume compared to existing state-of-the-art technology. The proposed MWT model has been included in Newton Raphson Load Flow (NRLF) method for power flow analysis. The feasibility of the model has been realized using a standard 5 bus test system and a modified IEEE 57 bus system. Operation of the PFC has been demonstrated using a hardware laboratory prototype for generating nearest compensating points (voltage vectors) corresponding to the obtained compensating voltages after load flow solution. The results obtained are verified by simulating the controller in MATLAB/Simulink.

On the Existence of the Power Flow Solution in DC Grids With CPLs Through a Graph-Based Method

Abstract: This brief explores the formulation of the power flow problem in DC grids with a classical incidence matrix through a graph-based formulation. This corresponds to a compact representation of the conventional backward/forward sweep methods, which is applicable to radial and mesh networks with a unique voltage controlled source. To guarantee the existence and uniqueness of the power flow solution in the DC network under well-defined operative conditions, the Banach fixed-point theorem is employed. Simulation results confirm that the solution of the proposed method is numerically comparable with classical approaches, such as Gauss-Seidel, Newton-Raphson, successive approximations and Taylor-based methods. All the simulations are conducted in MATLAB software.

An Iterative Scheme for the Power-Flow Analysis of Distribution Networks based on Decoupled Circuit Equivalents in the Phasor Domain

Abstract: This paper presents an alternative solution for the power-flow analysis of power systems with distributed generation provided by heterogeneous sources. The proposed simulation approach relies on a suitable interpretation of the power network in terms of a nonlinear circuit in the phasor domain. The above circuit interpretation can be solved directly in the frequency-domain via the combination of a standard tool for circuit analysis with an iterative numerical scheme, providing directly the steady-state solution of the power-flow of a generic distribution network. At each iteration, the resulting circuit turns out to be composed by two decoupled subnetworks, a large linear part and a set of smaller nonlinear pieces accounting for the load characteristics, with evident benefits in terms of the computational time. The feasibility and strength of the proposed simulation scheme have been verified on a large benchmark consisting of the IEEE 8500-node test feeder. Then it is applied to the statistical simulation of a power network accounting for the variability effects of renewable generators. According to the results, the proposed tool provides an effective alternative to the state-of-the-art approaches for power-flow analysis further highlighting the benefits of the application of well-established tools for circuit analysis to power-flow problems.

Modelling and analysis of radial distribution network with high penetration of renewable energy considering the time series characteristics

Abstract: Power distribution networks are in a transformation active distribution networks with distributed energy resources. However, the widely adopted distribution test networks were established many years ago, which are untimely and cannot reflect the characteristics of high penetration renewable energy. Therefore, in this study, a distribution network with high penetration renewable energy is established based on the real data of a renewable-energy-rich radial rural distribution network in China. The proposed radial distribution network includes three types of loads and two types of renewable energy distributed generations. The evaluation indexes are designed to assess the proposed system and compare with the existing distribution networks. In addition, the topical high/low voltage problem of distribution network caused by high penetration of renewables is discussed. Furthermore, based on the measured time series characteristics of load and renewable resources, the effectiveness of the proposed system is validated by power flow analysis and dynamic characteristic criterion.

Parallel Power Flow Computation Trends and Applications: A Review Focusing on GPU

Abstract: A power flow study aims to analyze a power system by obtaining the voltage and phase angle of buses inside the power system. Power flow computation basically uses a numerical method to solve a nonlinear system, which takes a certain amount of time because it may take many iterations to find the final solution. In addition, as the size and complexity of power systems increase, further computational power is required for power system study. Therefore, there have been many attempts to conduct power flow computation with large amounts of data using parallel computing to reduce the computation time. Furthermore, with recent system developments, attempts have been made to increase the speed of parallel computing using graphics processing units (GPU). In this review paper, we summarize issues related to parallel processing in power flow studies and analyze research into the performance of fast power flow computations using parallel computing methods with GPU.

Fundamentals of Electrical Power Systems Analysis

Abstract: Chapter 1 - Analysis of Electrical Power -- Chapter 2 - Transformer: Principles and Practices -- Chapter 3 - Power Generation -- Chapter 4 - Transmission Line Parameters and Analysis -- Chapter 5 - Modelling and Performance of Transmission Lines -- Chapter 6 - Symmetrical and Unsymmetrical Faults -- Chapter 7 - Load Flow Analysis -- Chapter 8 - Underground Cables -- Chapter 9 - Power System Stability Analysis -- Chapter 10 - Power System Harmonics -- Chapter 11 - Overhead Line Insulators and Sags.

A Robust Augmented Nodal Analysis Approach to Distribution Network Solution

Abstract: The ambition to decarbonize the source of energy for heat and transport sector through electricity from renewable energy has led to significant challenge in the way power distribution networks (DNs) are planned, designed and operated. Traditionally, DN was put in place to support the demand passively. Now with renewable generation, storage and demand side management through automation, provision of network support services have transformed the character of the DNs. Active management of the DN requires fast power flow analysis, state estimation, reactive power support etc. This paper proposes a method of power flow analysis which incorporates the challenges of distributed generator (DG) characteristics, demand side management and voltage support. The proposed approach reformulated the Jacobian matrix of the well-known modified augmented nodal analysis (MANA) method; thus, improving the robustness and solvability of the formulation. Reactive powers of the DGs, node voltages and currents of ‘non-constitutive’ elements were the chosen state variables. The performance of this method is compared with the MANA. Results are discussed and the effectiveness of the proposed approach is demonstrated with two example case studies.

Optimal placement of FACTS devices in power transmission network using power stability index and fast voltage stability index

Abstract: In this paper two techniques have been introduced to locate suitable position of FACTS devices in 14 bus IEEE interconnected transmission network to improve voltage profile, enhance power transfer capability and increase the efficiency of the overall power transmission The techniques introduced here are power stability index (PSI) and fast voltage stability index (FVSI) These indices are calculated from the data obtained after performing load flow analysis in 14 bus IEEE interconnected transmission networks by using Newton Rapson's method in MIPOWER software The FVSI technique shows better results in terms of reduction of reactive power losses, minimization of active and reactive power flow and The PSI technique shows better result in the reduction of active power losses

OATS: Optimisation and Analysis Toolbox for Power Systems

Abstract: Optimisation and Analysis Toolbox for power Systems analysis (OATS) is an open-source simulation tool for steady-state analyses of power systems problems distributed under the GNU General Public License (GPLv3). It contains implementations of classical steady-state problems, e.g. load flow, optimal power flow (OPF) and unit commitment, as well as enhancements to these classical models relative to the features available in widely used open-source tools. Enhancements implemented in the current release of OATS include: a model of voltage regulating on-load tap-changing transformers; load shedding in OPF; allowing a user to build a contingency list in the security constrained OPF analysis; implementation of a distributed slack bus; and the ability to model zonal transfer limits in unit commitment. The mathematical optimisation models are written in an open-source algebraic modelling language, which offers high-level symbolic syntax for describing optimisation problems. The flexibility offered by OATS makes it an ideal tool for teaching and academic research. This paper presents novel aspects of OATS and discusses, through demonstrative examples, how OATS can be extended to new problem classes in the area of steady-state power systems analysis.

Simulation of Incidental Distributed Generation Curtailment to Maximize the Integration of Renewable Energy Generation in Power Systems

Abstract: Power system security is increasingly endangered due to novel power flow situations caused by the growing integration of distributed generation. Consequently, grid operators are forced to request the curtailment of distributed generators to ensure the compliance with operational limits more often. This research proposes a framework to simulate the incidental amount of renewable energy curtailment based on load flow analysis of the network. Real data from a 110 kV distribution network located in Germany are used to validate the proposed framework by implementing best practice curtailment approaches. Furthermore, novel operational concepts are investigated to improve the practical implementation of distributed generation curtailment. Specifically, smaller curtailment level increments, coordinated selection methods, and an extension of the n-1 security criterion are analyzed. Moreover, combinations of these concepts are considered to depict interdependencies between several operational aspects. The results quantify the potential of the proposed concepts to improve established grid operation practices by minimizing distributed generation curtailment and, thus, maximizing power system integration of renewable energies. In particular, the extension of the n-1 criterion offers significant potential to reduce curtailment by up to 94.8% through a more efficient utilization of grid capacities.

Electrical Loads and Power Systems for the DEMO Nuclear Fusion Project

Abstract: EU-DEMO is a European project, having the ambitious goal to be the first demonstrative power plant based on nuclear fusion. The electrical power that is expected to be produced is in the order of 700–800 MW, to be delivered via a connection to the European High Voltage electrical grid. The initiation and control of fusion processes, besides the problems related to the nuclear physics, need very complex electrical systems. Moreover, also the conversion of the output power is not trivial, especially because of the inherent discontinuity in the EU-DEMO operations. The present article concerns preliminary studies for the feasibility and realization of the nuclear fusion power plant EU-DEMO, with a special focus on the power electrical systems. In particular, the first stage of the study deals with the survey and analysis of the electrical loads, starting from the steady-state loads. Their impact is so relevant that could jeopardy the efficiency and the convenience of the plant itself. Afterwards, the loads are inserted into a preliminary internal distribution grid, sizing the main electrical components to carry out the power flow analysis, which is based on simulation models implemented in the DIgSILENT PowerFactory software.