Comparison of load flow analysis using PSAT and ETAP

Flexible alternatives to decoupled load flows at minimal computational costs

In the distribution system, proper placement of distributed generation (DG) is still a very challenging issue for getting their maximum potential benefits. Power system stability should be determined through load modeling, hybrid energy storage system (HESS), and photovoltaics (PV) modeling. This paper proposed the optimal sizing and location of photovoltaic using the Modified Harris Hawk Optimization (MHHO) algorithm. The energy generated from the photovoltaic (PV) is stored in the HESS, where the energy’s charging and discharging from the storage unit is framed with a reduced power loss (active and reactive power). The optimal sizing and placement of the PV system will provide better voltage stability. The Modified Harris Hawk Optimization Algorithm (MHHO) frames the system’s voltage stability. The Newton-Raphson load flow method is used to analyze the loading in the power system. The IEEE 33 and 69 bus systems are used to analyze the load flow to the consumers, thus analyzing the power system’s dynamic performance. The performance and voltage stability of the presented model are compared with the existing optimization techniques, which include the Firefly Algorithm (FA), Crow Search Optimization (CSO), Particle Swarm Optimization (PSO), Analytical PSO (APSO), Improved Cayote Optimization Algorithm (COA) and Whale optimization algorithm (WOA) through the MATLAB/Simulink platform.

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.

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 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.

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.

Generalized three phase robust load-flow for radial and meshed power systems with and without uncertainty in energy resources using dynamic radial basis functions neural networks

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.

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.

A modified form of Newton'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.

Load flow calculations are performed an any energy system to enable system engineers to satisfy the needs of the society from electric energy, and are necessary in making projects and research work connected with system planning and development. The most popular and widely used method for these calculations is the Newton-Raphson method which is advantageous to other methods by its quadratic convergence property. There are cases however, where the Newton-Raphson method is divergent . One of the main reasons for this divergence is its high sensitivity to the initial estimates of the unknowns. This paper presents two starting methods for the evaluation of the initial estimates for Newton-Rephson load flows. The initial estimates calculated by these methods are found to guarantee a relible convergence and increased speed of solution by the Newton-Raphson method. The reduction in computer times has amounted to as high as 50% of the time without starting methods.

Amicrogrid is a combination of clusters of distributed generators connected to fulfill the requirement of dedicated load. A microgrid can be operated with standalone or grid connected mode. A microgrid when operated in standalone mode with a limited voltage and power rating is more likely prone to a serious damage due to its unpredictable faults. Load flow, voltage stability & short circuit analysis of a micro-grid is essential for both design and performance monitoring and to ensure reliable microgrid operations. The faults with a continuously varying in nature affects the normal operation of buses and so to the peripherals associated to the micro-grid. The cause and severity of such faults plays a vital role while designing protection scheme in standalone micro-grid as standalone mode has confined generation. In this paper, electrical model of a 52.3 kW Photo-voltaic based micro-grid is developed on Electrical Transient Analysis Program (ETAP) and various transient conditions such as load flow, loss of DG & short circuit analyses are performed. A detailed short circuit analysis puts light on various short circuit conditions and provides useful analysis. ETAP is the most comprehensive analysis platform for the design, simulation, operation, and automation of generation, distribution, and industrial power systems. ETAP also provides the industry leading transient analysis of power system and micro-grid so chosen for this transient analysis study. A short circuit analysis is calculated based onIEC Std. 60909 using ETAP. This paper presents a simulated model of micro-grid with actual system oriented results and analyzes responses of system during fault conditions and various contingencies.

Steady state analysis techniques use linear phasor circuit models, but power flow calculations require the solution of nonlinear algebraic equations. Small-signal linear models form the basis of solution algorithms such as the Newton-Raphson method and decoupled load flows. Since linear models are attractive from the viewpoint of gaining significant insight into system behavior under different operating scenarios, large-signal models such as 'DC models' are commonly employed. Results obtained from linear models are approximate, but they provide easy comparison between different operating conditions. Contingency ranking using a DC model, and generation shift and line outage distribution factors is highly satisfactory in many instances. Studies requiring steady state analysis such as security analysis, optimal power flow and economic dispatch, and voltage stability can significantly reduce computational burdens by assuming linear models. The main objective of this paper is to study quantitatively the relative merits of commonly used linear models in steady state power system analysis. The 'DC model' assumes negligible resistances and flat voltage profiles, and relates the bus phase angles to real power injections. A new linear model which accounts for the voltage and reactive power flows is developed, and compared to the results from 'DC model' and 'small-signal' models. The figure of merit for comparison is taken as the root mean square difference of similar quantities such as bus voltages and line active and reactive flows. IEEE 14-bus is used for the testing. Results show significant potential for the new linear model.

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.