Flexible alternatives to decoupled load flows at minimal computational costs

This paper presents an improved second order load flow method in rectangular coordinates which is distinctly superior to the existing second order methods from the point of view of both speed and storage. Further, the proposed method's memory requirement is comparable to that of the Fast Decoupled Load Flow (FULF) method. The new method would be considerably faster than the FOLF method for a number of systems for which the FDLF method requires a large number of iterations to converge. The proposed method is highly reliable and it gives solutions for a number of systems for which the FDLF method fails. In addition a novel procedure for handling generator bus Q limit violations is also presented.

Line outage simulation is a necessary part of contingency analysis. The Newton-based full AC load flow method is commonly used for this purpose despite its time consuming computational process. A compensation scheme and a partial refactorisation method is proposed for the efficient solution of the first iteration of the post-contingency full AC load flow. Two Newton-like load-flow methods, the Fixed Newton method and the modification of the right-hand-side vector method, are also described to continue the calculation until convergence is obtained. These methods eliminate the need for complete refactorisation of the jacobian matrix. The two methods are compared with the Newton-based full AC load flow method and the fast decoupled load flow in three test systems to demonstrate their convergence characteristics.

Fast Decoupled Load Flow (FDLF) is a very popular and widely used power flow analysis method because of its simplicity and efficiency. Even though the basic FDLF algorithm is well investigated, the same is not true in the case of additional schemes/modifications required to obtain adjusted load flow solutions using the FDLF method. Handling generator Q limits is one such important feature needed in any practical load flow method. This paper presents a comprehensive investigation of two classes of schemes intended to handle this aspect i.e. the bus type switching scheme and the sensitivity scheme. We propose two new sensitivity based schemes and assess their performance in comparison with the existing schemes. In addition, a new scheme to avoid the possibility of anomalous solutions encountered while using the conventional schemes is also proposed and evaluated. Results from extensive simulation studies are provided to highlight the strengths and weaknesses of these existing and proposed schemes, especially from the point of view of reliability.

Until now, little attention has been paid to load-flow methods with variables expressed in rectangular form. These methods could have some advantages over existing methods in polar form, bearing in mind the large amount of computation required for load-flow calculations in large networks where evaluation of polar trigonometric functions is necessary. This paper presents several decoupled load-flow methods, some of them having very good convergence and time characteristics, based on the application of Newton's method to equations of nodal power or current mismatches with the variables, i.e. the nodal voltages, expressed in rectangular form. All the methods presented are compared with several variants of the decoupled load-flow method with variables in polar form. The methods given are applied in studies of electrical networks with different voltage levels from distribution to EHV and various elements, including transformers, cables, short lines, long lines, as well as conditioned and ill-conditioned systems. Comparison is made between all methods by noting the number of iterations for converged solutions from a common start to the end of the iteration process.

Traditional Load Flow methods are considered as one of the most important tools for analyzing the operation of power system and to perform the planning studies. Since distribution systems exhibit characteristics like higher R/X ratio and loading of the feeders is higher, traditional load flow methods fail to analyze these networks and hence separate methods are developed to handle the situation. However, these distribution load flow methods restrict to calculating power flow at feeder level (> 11 kV) by representing load as a suitable model. The load segments i.e. 3-phase 4-wire LV network downstream to the 11kV/400V distribution transformer, is represented as time deterministic static loads while calculating distribution load flow. Due to the increase in demand for more situational awareness until the edge of the network and with large scale deployment of Advanced Metering Infrastructure (AMI) & Geographical Information System (GIS) technologies, it is possible to do load flow analysis on 400V 3-phase, 4-wire LV distribution network in phase-wise manner using smart meters, geographical & communication technologies. In this paper, we propose algorithm for such a load flow method and discuss its applications.

This paper develops a model to show the effects of soft errors on power flow calculations. We create artificial bit-flips and apply them to solve linear equations obtained in Fast Decoupled Load Flow (FDLF) method. With this, we aim to represent the sensitivity of FDLF iteration against soft errors with a statistical view by using different numerical fault injection scenarios. The study focuses on the soft-error sensitivity of the FDLF method with exact (LU) linear solvers. We performed approximately 60000 experiments on IEEE 14, 30, 57, 118 test systems to examine the soft-error resiliency of FDLF method. Statistical study shows that even for small systems, soft-errors may have large impacts on the convergence of the FDLF. Hence, an improvement should be provided against soft errors in power flow studies to obtain more efficient and reliable simulations in near future exascale computational environments.

Voltage stability enhancement is obtained by adjusting the control variables to nearer optimal solutions for the selected objective function. This paper presents the biological swarm behaviour of a bird flocking or fish schooling for solving the optimal reactive power dispatch (ORPD) problem using PSO algorithm. The main idea of this paper is to minimize the sum of the square of voltage deviations at load buses using fast decoupled load flow (FDLF) method and sensitivity parameters relating control and dependent variables. The on-load tap changing transformers (OLTC), Generator exciters, Static VAR Compensators (SVC) are used as control variables for improvement of system parameters like voltage deviation (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</inf> ), L-index and real power loss. The effectiveness of the proposed method is demonstrated on IEEE New England 39-bus power system for near optimal solutions. The performance of the proposed method is compared with conventional optimization technique and presented for illustration purpose.

Renewable energy sources must be scheduled to manage power flow and load demand. Photovoltaic power generation is usually connected to power distribution networks and is not designed to add significant amounts of production in the event of increased electricity demand. Therefore, it is necessary to increase the generated capacity (i.e., hosting capacity) to meet the expansion in demand. This paper discussed two topics; the first is how to create an energy management strategy (EMS) for a hybrid micro-grid containing photovoltaic (PV) and battery energy storage system (BESS). A model was created within the MATLAB program through which the charging and discharging process of the BESS was managed, and the energy source was through PV. The model is connected to the leading network, where the m.file is linked to the model to control variable settings. This was carried out by using a logical–numerical modeling method. The second topic discussed how to evaluate hosting capacity (HC) without causing the network to collapse. This was achieved by choosing the best location and size for the PV. This study relied on the use of two algorithms, particle swarm optimization (PSO) and Harris hawks optimization (HHO). The fast decoupled load Flow (FDPF) method was adopted in the network analysis and finally the results of the two algorithms were compared.

A modified form of Newton&apos;s method for load flow is introduced in this paper. The results tabulated, for eight different power systems, indicate a consistent advantage in using this modification over the standard Newton method. The comparisons are made on systems that include several for which load-flow results were previously published by other authors.

SUMMARY A significant section of the future electrical power systems, that is, smart grids, will be dc microgrids and distribution systems. Obviously, the voltage control is one of the important issues of these dc power systems. DC-bus signaling (DBS) control methods, as distributed, autonomous, simple, highly reliable, inexpensive, modular and practical control methods, are one of the most important categories of the voltage control methods in dc microgrids and distribution systems. In the dc power systems with DBS control methods, the determination of the generated power shares of the distributed power sources, as vital entries for the conventional load flow methods, before the execution of a load flow method, is not possible. Also, in these dc power systems, none of the power sources can be considered as a constant voltage source, that is, the slack source. Consequently, the conventional load flow methods are not applicable to dc microgrids and distribution systems with DBS control methods. In this paper, a novel, practical, robust, fast, precise load flow method is presented to overcome the mentioned serious complexities in the dc power systems. The proposed load flow method necessitates the least input data. It determines the generated power shares of all the sources during its execution. Besides, the load flow method necessitates no constant voltage source or slack source. Furthermore, the proposed load flow method benefits from low computational time and the storage requirements and the removal of the ill-conditioned problem. The algorithm validation and the numerical results derived in this paper confirm the accuracy and the remarkable performance of the load flow method. Copyright © 2015 John Wiley & Sons, Ltd.

This paper describes a critical evaluation of Non-Divergent Load flow methods in well, ill and unsolvable conditioned systems. The comparison studies deals Multiple Load Flow Solution (MLFS) based Second-Order Load-Flow (SOLF) in polar coordinate and Continuation Load Flow (CLF). The analytical bases, ability consideration of theses methods to return operation of power system from unsolvable to solvable region solution. Attention is given to the problems and techniques of to provide optimal recommendations of the parameters, that using in these Non-Divergent Load flow methods to lead to solvable region, based on inequality constraints of power system. A part of the survey, this paper also presents the comparison of numerical result using different type of aforesaid load flow methods for well and ill- conditioned systems. Accordingly, load flow simulation has been solved using the C++ programming.

Convergence of the fast decoupled load flow for systems with heavy reactive power compensation

In power system studies, load flow (LF) analysis is one of the most crucial tools. It is the most important and required method of looking at issues with power system design and operation. A series of nonlinear algebraic equations make up the LF issue, which needs to be mathematically solved by iterative numerical methods. In the current modern distribution systems (DSs) field, the most significant criterion that is heavily influenced by the DS’s size—which keeps growing—is the convergence of the solution. This paper gives readers an overview of recent research that has used both classical and artificial intelligence-based methods to handle LF-related issues with particular attention to DSs. The impacts of high R/X ratio of DSs along with various load models are discussed. Various standard and non-standard test feeders used for investigating LF algorithms are addressed. It also offers suggestions for future paths for this field of study. The types of examined LF problems are used to categorize the surveyed literature.

The level of electrical quality has become a necessity in supporting human activities, especially in voltage stability. To support the calculation of voltage stability, various load flow methods have been developed. Load Flow Analysis is very important in planning and implementation in designing future power system expansion and in determining the best operation of the existing system. The tools for calculating simulation based power flow are the Power Tool Analysis Toolbox (PSAT) and the Transient and Electrical Analysis Program (ETAP). This paper discusses the comparison of the performance of the two load flow simulation tools, PSAT and ETAP. The Gandul Substation network data in Indonesia in April 2019 with a load of 15.37 MW is used for simulations. Load flow analysis is performed using Newton Raphson method with a network of 11 buses (150 kV, 20kV). The simulation results show that PSAT has a deviation of about 0.663% to the Bus Voltage from GIG and ETAP simulation has a deviation of about 0.562% to the Bus Voltage from GIG.

In this paper a new and efficient method for solving the load flow problem of a distribution system is discussed. It is based on network topology, basic circuit laws and power summation technique. The main contribution of this paper is: (i) It proposes a new, efficient load flow method for radial and weakly meshed distribution systems, (ii) It evaluates the impact of load models, different values of X/R ratios, load growth for future expansion and tolerance levels, (iii) It analyses the impact of number of loops on weakly meshed distribution systems, (iv) and also gives comparison of radial and weakly meshed distribution system. The results are obtained for voltage values, total real and reactive power losses, time of computation, and number of iterations required. Computer program coded to implement this power flow solution scheme in MATLAB and successfully applied to several practical distribution networks with radial and weakly meshed structure. Effectiveness of the proposed load flow method has been presented on IEEE 33bus radial and meshed distribution networks.