Load Flow Analysis

The paper describes the software system which supports the planning and operations functions in the electricity market environment. The system automates the management of the power system and electricity market data used in the decision support process. Various power system and electricity market quantities can be monitored through time providing trends and statistics on longterm basis. An extensive set of power system snapshots are available to enable load flow, short circuit, transient stability and oscillatory stability analysis to be performed for a selected time.

This work presents a general and simple method to obtain a single multiphase equivalent pi-circuit, suitable for power flow studies that takes the coupling effects into account for any line transposition scheme. The resulting circuit, suitable for use in connection with multiphase power flow programs is obtained from node reduction of all cascaded multiphase pi-circuits, each one representing the section in between transposition towers. For conventional power flow programs, symmetrical component coupled circuit parameters are obtained as well. A study carry out for a Brazilian electrical utility, in which two 230 kV transmission lines run at the same tower between Paulo Afonso and Fortaleza substations (678.90 km long), is presented. Power flow results have shown that the reactive power is strongly affected by the coupling between the two transmission lines.

This paper proposes parallel algorithm of a general three-phase load flow calculation based on symmetrical components. The proposed algorithm comprises of two part i.e. sequence admittance matrix construction and sequence decoupled algorithm for sequence networks solver which have three independent sub-problems corresponding to positive, negative, and zero-sequence networks. These two parts are solved concurrently using multi-core parallel processing. The IEEE 8500-node test feeder is used to test the robustness of the algorithm for large system problem. The large unbalanced load connected to the center-tapped transformer solved using an iterative forward and backward sweep analysis method based on voltage drop analysis. The result showed that parallel three-phase load flow produced execution speedup and proved the ability to handle large scale problems.

Due to the important role that distribution systems play in quality of power delivered to the customers, there has always been a great deal of interest in investigating different methods of efficiency enhancement for these networks. Two of these methods are Feeder Reconfiguration (FR) and Capacitor Allocation (CA); both have been widely employed to reduce losses and improve several other operational characteristics in electrical power distribution systems. As in FR process the topology of the network changes, it is necessary to change some previous settings; for instance: the capacity of capacitor banks in service in each bus, after each reconfiguration process. This is due to the fact that the new topology may require another arrangement of capacitors in service to address an optimized operation of the system. In this paper, a method is proposed in order to perform both FR and CA simultaneously. Among the advantages of this method, we should mention less computational time and more accuracy in finding the optimal solution. To verify the proposed method, simulations are performed on the IEEE 33bus distribution test system. Furthermore, to investigate the efficiency of the proposed method, four scenarios are defined. And, two operational indices are introduced. The resultant system power losses and the computed indices clearly demonstrate the superiority of the proposed method.

The power flow is the fundamental tool for the study of power systems. The data for this problem are subject to uncertainty. This paper uses interval withmetic to solve the power flow problem. Interval arithmetic takes into consideration the uncertainty of the nodal information, and is able to provide strict bounds for the solutions to the problem: all possible solutions are included within the bounds given by interval arithmetic. Results are compared with those obtainable by Monte Carlo simulations and by the use of stochastic power flows. Object oriented programming techniques make it possible to use interval arithmetic with minimal modifications to existing software. However, to reduce the conservatism inherent in all interval arithmetic computations, the paper describes an iterative method used to obtain the "hull" of the solution set.

This paper provides a new approach for modelling of distribution transformer in the forward/backward sweep-based algorithms for unbalanced distribution systems. For the transformer modelling symmetrical components theory is used and zero sequence-voltage and -current updating for the sweep-based methods is shown. The validity and effectiveness of the proposed method is demonstrated by a simple two-bus balanced and unbalanced system for grounded wye-delta and delta grounded wye transformer connections. Results are in agreements with the literature and show that the proposed model is valid and reliable.

In developing country there is a perpetual growing demand for electricity with an efficient and reliable system of power supply. Power system is the most complex network with power generation, transmission and distribution system to consumer loads. The distribution network is an integral part of the power system and acts as an interface to consumer load points. The network incurs significant losses and voltage drop in the electrical system. Loss minimization and voltage stability are the main objectives of the distribution network design. This paper introduces optimal branch conductor selection for the microgrid using unified central load concept for radial distribution systems of microgrid. The conductor size defined by this approach will meet the maximum current carrying capacity and uphold the acceptable voltage levels of the radial distribution system for rural areas. The effectiveness of the proposed method in single line diagram is demonstrated through the design of microgrid as an example for a developing country. The comparison shows that the results by proposed central load method is in close similar normal representation of uniform consumer load and both are following similar trends. The voltage drops and total loss by proposed method is compared and verified with three phase and single phase network system along with unified end load representation by using ETAP simulation software.

Incorporation of HVDC transmission subsystems in AC transmission networks has been a major change in power transmission during the last few years. This change required modifications in the performance evaluation procedures notably for load flow and stability analysis. The methodologies used for AC/DC system's load flow calculation and transient stability analysis are presented in this chapter. In this thesis, the investigations are carried out on the improvement of power system stability by utilizing auxiliary controls for controlling HVDC power flow. AC/DC load flow using eliminated variable method is utilized in the transient stability analysis. Transient stability analysis is done on single machine system and multi-machine system, using different control signals derived from the AC system.

This study presents a forward/backward sweep (FBS) load flow method for AC autotransformer (AT)-fed electrical railway networks considering dynamic movement of trains. Field measurements of Tehran -Golshahr suburban railway are compared with simulation results. Moreover, effects of the time headway reduction on this suburban railway and its transmission power supply system are investigated. Then, to minimise power losses, two methods of the reactive power compensation are studied; the pulse-width-modulated (PWM) trains and a static var compensator (SVC). For the aforementioned cases, fluctuations of the displacement factors (DISF), defined in p -q -r theory are simulated at the point of common coupling (PCC). MATLAB software is used for programming and simulations.

In recent days, due to advancement in technology, the end users are facing severe power quality issues. Load flow analysis is one of the fundamental methodologies in solving power network problems. The key importance of load flow analysis is to improve the performance of distribution network. The main intention of this reserach is to carry out the load flow and voltage stability analysis of 10 bus loop distribution network energized by a generator. Load flow analysis is carried out by using Newton Raphson method. The per unit voltage and angle of the proposed network is determined in all 10 buses by load flow analysis. The voltage stability analysis is implemented by introducing a fault in the network. Here, a power fault is injected at bus 4 between the time interval of 2 to 3 sec to analyse the stability of the system. The voltage stability of the system is analysed for the network with and without automatic voltage regulator (AVR). The AVR unit is tuned by using power system stabilizer (PSS). The results are examined by simulating the network using openmodelica connection editor. From the simulation results the per unit voltages and angles at all 10 buses are determined for the network with and without AVR. By comparing both the results it is proved that the network with AVR has better voltage stability than the other. Thus, the voltage stability of the system is improved by connecting the generator with AVR and PSS.

This paper describes frequency-dependent characterization of multi-terminal decoupling capacitors 8, 14, and any arbitrary number of terminals) by using a full-wave tool developed at Intel. This tool can capture high frequency effects with fast CPU run time, which enables accurate modeling of the power delivery system. The full-wave Sparameters have been validated with the measurements and the modeled data obtained from a commercial tool (HFSS). Based on its fast and accurate solution, different design confijyrations of capacitors have been studied to identify the optimal configuration which will maximize the performance of the decoupling capacitor. To capture the frequencydependent behavior of capacitor impedance, a higher order representation made up with 7 or 9 elements of RLGC was developed. This circuit representation was used to assess the accuritcy of conventional series lumped RLC capacitor model. Finally, the responses were incorporated into a high performance microprocessor's power delivery network to invesiigate system performance. 0-7803-8365-6/04/$20.00 02004 IEEE Your accompanying CD-ROM contains a version of this paper with color images.

An outline is presented of the development process of the intelligent load flow engine. Building the engine proceeds from simple to hard tasks by incrementally improving the organization and the representation of the knowledge base. Interface programs are designed to provide the communication from the engine to a load flow and contingency analysis program

... Reconfiguration: A Soft Computing Approach Sandeep Chakravorty Jaydeep Chakravorty Shweta Sarkar ... Goswami and Basu [2] have shown that it is inappropriate to represent initially the distribution network as a meshed network and open the ...

Electric vehicles are the demand of the current scenario to fight with the increasing levels of pollution. Electric vehicles operate by getting power from the battery which needs to be charged after a particular duration. Battery swapping stations are used for providing the optimal power for charging these batteries. An algorithm known as Particle swarm optimization can be used to find the optimal cost of these battery swapping stations. The project presents an expository study about Particle Swarm Optimization and thus various factors related to it.

This work presents an approach aiming at inferring the operative configuration (OC) of distribution networks. In order to attain this objective, the OC problem is decomposed in two parts. In the first part, the available real-time data and expert knowledge are integrated by means of rule-based Type-2 Fuzzy Logic Systems. As a result, an approximate initial solution is obtained. In the second part, the initial solution is dynamically tuned using customer trouble calls. This is done by means of an approach based on fuzzy relational equations and fuzzy abductive inference. At every stage, all plausible solutions are calculated in order to obtain a complete outlook of possible options. The performance of the methodology is evaluated on a real distribution feeder and the results are presented.

Este trabalho consiste na modelagem e simulação de um aerogerador de pequeno porte interligado à rede elétrica de distribuição secundária, ou seja, conectado à rede de baixa tensão. O sistema implementado computacionalmente é constituído pelos seguintes componentes: turbina eólica de 8 kW de potência mecânica nominal quando submetida a uma velocidade de vento de 12 m/s, gerador síncrono de ímã permanente trifásico, sistema de rastreamento do ponto de máxima potência, conversor CC-CC do tipo boost, inversor de frequência monofásico em ponte completa e filtro mitigador de distorção harmônica. Inicialmente, todos os elementos constituintes do aparato eólico-elétrico são descritos separadamente em detalhes. De posse de todos componentes do aerogerador, é feita a implementação na plataforma computacional PSIM para que se proceda a avaliação de desempenho. Nesta análise de performance, são avaliadas diversas grandezas elétricas, tais como: a potência ativa gerada e entregue à rede, os perfis das formas de ondas das tensões e correntes em alguns pontos do sistema de geração distribuída, além da análise do conteúdo harmônico da corrente elétrica antes e após o inversor de frequência.

In this paper, an improved power flow analysis algorithm for distributed generation (DG) units controlled with P/Q droop functions and virtual impedances in a low voltage (LV) microgrid is proposed. The proposed analysis provides in contrast to conventional power flow calculation techniques: (i) consideration of virtual impedance parameters and (ii) higher accuracy in reactive power flow calculation. The improved power flow analysis algorithm proposed in this paper is validated by comparing the calculation results with detailed time domain simulation results. Case studies have been carried out by analyzing the effects of control parameter variation in the power flow results obtained by the proposed algorithm.

This paper describes predictive load balancing schemes designed for use with parallel adaptive finite element methods. We provide an overview of data structures suitable for distributed storage of finite element mesh data as well as software designed for mesh adaptation and load balancing. During the course of a parallel computation, processor load imbalances are introduced at adaptive enrichment steps. The predictive load balancing methods described here use a priori estimates of work load for adaptive refinement and subsequent computation to improve enrichment efficiency and reduce total balancing time. An analysis code developed with these components for solving compressible flow problems is used to obtain predictive load balancing results on an IBM SP2 computer. Our test problem involves the transient solution of the threedimensional Euler equations of compressible flow inside a perforated shock tube. We also present a message passing library extension in development which allows for automated packing of messages to improve communication efficiency.

... formulate the network reconfiguration problem for both loss reduction and load balancing as a multi-objective, non-differentiable optimization prol~- lem with both equality and inequality constraints. 'Ihv formulation is summarized as follows: Given a ra~1i;iI distribution system of ...

The paper describes an algorithm for determining the line outage contingency of a line taking into account of line over load effect in remaining lines and subsequent tripping of over loaded line(s) leading to possible system split or islanding of a power system. The optimally ordered sparse [B′], [B″] matrices for the integrated system are used for load flow analysis

Network reconfiguration is a combinatorial optimization problem that can be used to reduce power losses in distribution systems while satisfying all operating constraints. Distribution systems are greatly impacted by the increasing integration of distributed generation (DG) resources and thus it is necessary to develop methods that can quantify the effects of DG on network reconfiguration. This paper first introduces an efficient methodology to reconfigure distribution systems to minimize power losses, and analyzes the effects of DG on the reconfiguration problems, then discusses how to take advantage of distributed generation to improve distribution system reconfiguration.

This study presents a forward/backward sweep (FBS) load flow method for AC autotransformer (AT)-fed electrical railway networks considering dynamic movement of trains. Field measurements of Tehran-Golshahr suburban railway are compared with simulation results. Moreover, effects of the time headway reduction on this suburban railway and its transmission power supply system are investigated. Then, to minimise power losses, two methods of the reactive power compensation are studied; the pulse-width-modulated (PWM) trains and a static var compensator (SVC). For the aforementioned cases, fluctuations of the displacement factors (DISF), defined in p-q-r theory are simulated at the point of common coupling (PCC). MATLAB software is used for programming and simulations.

Abstract—Energy power from renewable sources, especially wind turbine generators, are being considered as an important generation alternative in the electrical power systems around the world due to their non contaminant nature and low environmental effects. In ...

A study was conducted to improve the Iraqi National Control center by adapting the facilities of the agent technology and to obtain an automated control system for controlling and monitoring the electrical network. This study presents simulation results of practical agent in power flow control scenario applied to the Iraqi super grid network (400 kV).

Access to electric power is critical to societal welfare. In this paper, we analyze the interaction between a defender and a terrorist who threatens the operation of an electric power system. The defender wants to find a strategic defense to minimize the consequences of an attack. Both parties have limited budgets and behave in their own self-interest. The problem is formulated as a multi-level mixed-integer programming problem. A Tabu Search with an embedded greedy algorithm for the attack problem is implemented to find the optimum defense strategy. We apply the algorithm to a 24 bus network for a combination of four different defense budgets, three attack budgets, and three assumptions as to how the terrorist crafts their attack.

The International Electrotechnical Commission (IEC) has recently released the Technical Report IEC/TR 61000-3-13 for the assessment of voltage unbalance emission limits to individual customer installations connected to medium-voltage (MV), high-voltage, and extra-high-voltage power systems. As in the counterpart IEC technical reports for harmonics (IEC 61000-3-6) and flicker (IEC 61000-3-7) allocation, IEC/TR 61000-3-13 also apportions the global emission allowance to customers in proportion to their agreed apparent power. However, noting that voltage unbalance at a busbar can arise due to load and system (essentially lines) asymmetries, IEC/TR 61000-3-13 applies a scaling factor to the apportioned allowance. Tis factor represents the fraction of the global emission allowance that can be allocated to installations. Conversely, the factor = 1 accounts for the emission arising as a result of system inherent asymmetries. This paper addresses the global voltage unbalance emission in MV power systems arising as a result of line asymmetries on which a systematic evaluation method is not given in IEC/TR 61000-3-13. First, a detailed study with the view to investigate the influence of line asymmetries on the global emission and its dependency on various load types is carried out by employing a simple radial network. Second, a matrix-based methodology, covering radial and interconnected networks, for the assessment of this emission at the nodal level taking line, system and load characteristics, system operating conditions, and downstream load composition into account are proposed. The methodology is verified by using unbalance load-flow analysis.

for transformers and circuits, respectively, to zero). Although the masking is not completely eliminated, its effects are reduced. In summary, the new ranking algorithms does remarkably well and is superior to the old algorithm. The ranking agrees almost perfectly with the ranking produced by calculating PI from de load flows; the correla¬ tion between overloads and high rank is also quite good, the only difficulty being masking. The effects of masking can be greatly reduced through partitioning followed by multiple rankings.

AC/DC is one of the most common power conversions in power electronics. DC loads should be fed with a stable and a tight regulated voltage. At the same time, the ac/dc converter should comply with low-frequency harmonic regulation. The classical two-stage ac/dc converters achieve these two objectives, although the overall efficiency is low because the power is processed twice. An alternative solution is presented in this paper. It is based on the division of the input power in two parts, being one of them processed only once and keeping a unity power factor. This strategy improves the efficiency and reduces the size of the converter without any complex control scheme. This proposal can be implemented with a great variety of well-known topologies. The experimental results show that this solution is a good tradeoff between efficiency and size.

Power systems are continually experiencing fluctuations of small magnitudes. However, for assessing stability when subjected to a specified disturbance, it is usually valid to assume that the system is initially in a true steady-state operating condition. Power system is subjected with the verity of fluctuation in their parameters. So their performance is not stable at all. This fluctuation must be mitigate as possible as under prescribe limit. In HVDC transmission system, power is generated and distributed in AC, only the transmission is done in the DC. During the ac to dc conversion power system observe the inability problems. In this way, it is essential to analysis the power system performance to enhance it. To ensure satisfactory operation and equipment safety, several limits are recognized in establishing the current order: maximum current limit, minimum current limit, and voltage-dependent current limit. Higher-level controls may be used, in addition to the above basic controls, to improve AC/DC system interaction and enhance AC system performance. Here we have adopted the PID (Proportional integral deferential) controller. Keywords-AC/DC Power System, DC Line, Maximum Current Limit, Minimum Current Limit, And Voltage-Dependent Current Limit , Load Flow Analysis , Multi Machine System Analysis, ID Controller