Review of Power Flow Study in Distribution Network

Review of Power Flow study in Distribution Network 1Aiswarya Rajalaxmi, 2Mr.Karanveer Dhingra Department of Electrical Engineering, Lovely Professional University, Punjab, India [email protected]

Abstract: In this paper, we discuss about the various Generally power flow equations are non- methods are used for power flow study calculation, linear and they can be solved by iterative method. which are used in the power system. With the help of The iteration procedure involves an initial value for power flow study, we are made to plan the best operation and plan for future expansion to keep with each of the unknown values. There are many the load growth as well as control of the existing system. different type of iterative method for calculation of While studying the power flow study in the power power flow such as: system we will go through several research papers i. Gauss Seidel method which use different technique for power flow ii. Newton-Rephson method calculation in their papers. The power flow study is to planning, designing and guide lines to control room of iii. Decoupled method distribution network have been discussed. iv. Forward/Backward method Keywords: Power flow, Distribution Network. Nowadays, solution of power flow problem I. INTRODUCTION can calculated by digital based computers because of Power flow is also known as load flow study. economy accuracy, quicker operation, and greater With the help of load flow study, we can calculate the flexibility and takes less time to reach the current, voltage, active or reactive power and their convergence. phase angle at the different type of buses on the The feature of power flow method is as power system under steady state condition. Power bellows: flow study provides instruction to generating i. Storage is minimal substation and station control room for reactive ii. For ill-condition system reliability is more power compensation, tap setting loadings and relay iii. Ease of programming settings etc. Load flow study is very essential and important for electrical power system for planning, iv. Fast convergence because of high speed. designing and giving guide lines to control room for II.LITERATURE SURVEY operating engineers. A set of algebraic non-linear equation is occurred due to mathematical approach of [1] L. F. Ochoa and A. Padilha-Feltrin (2004) power flow problem. Analysis of rearranging the published a paper in which, they presented that in circuit on power factor, bus voltages and also order to consider the inherently unsymmetrical line calculation of line losses for different condition. The segments and typically unbalanced loads, power flow power flow study is also required for the analysis of algorithm had to be expanded in order to consider contingency and transient stability study. three phase three wire systems. Even three-phase four wire systems are used with explicit neutral wire. In power system for power flow studies, we are Three phase three-wire power flow algorithm is a generally identified three different types of buses, tool for power system analysis. This Three-phase such buses are as follows: three wire system requires reliable impendences and a. Slack Bus or Reference Bus model to get accurate result. Kron’s reduction b. Load Bus or P-Q Bus procedure is used for embeds neutral wire influence c. Generator bus or PV Bus into phase wire. This reduction procedure has shown Here in each bus there are four variables available good result when three phase three-wire power flow in which two are known and other two are to be algorithms based on current summation method. But unknown. Bus 1 is generally recognized as slack bus. this Kron’s reduction can harm reliabilities of some Generally large generating station connected to bus algorithms. In this work Three-phase Three-wire i.e selected as slack bus. power flow algorithms based on power flow summation method will be compared with Three- phase four wire approach based on forward backward switches allowing three phase supply of the technique and current summation. transformer. Here some examples of this proposed In the above comparison between three phase method is given using real data’s. The above section four wire algorithm and capsids Baran-Wu and Luo gives an idea about phase balancing which is used to semylen’s extended algorithm, it was shown that the reduce distribution feeder loss and helps to secure the best manner to compute power flow while using system from any kind of disturbances. Above project these three-phase three-wire approach is to consider purely based on MATLAB. This project is tested the 3*3 original matrix impedances neglecting using many real data’s and it is concluded that, this ground resistivity and neutral wire influences. Both method is very effective. the algorithm obtains the same result. [4] N. Rugthaicharoencheep and S. Sirisumrannukul [2] Flávio Vanderson Gomes, Sandoval Carneiro, (2010) published a paper in which, they presented Jose Luiz R. Pereira, Paulo Augusto Nepomuceno Feeder Reconfiguration is an important and useful Garcia and Leandro Ramos de Araujo (2006) technique to reduce feeder loss and improve system published a paper in which, they presented that, a security and reliability. The configuration may vary purely based on distribution system according to the switching operation. By changing reconfiguration(DSR) in which a new reconfiguration the open/close status of the feeder switches load algorithm technology is described. This algorithm current can be transferred from feeder to feeder. uses a mesh distribution system considering all Mainly Feeder Reconfiguration refers to a process switches closed then switches are opened to eliminate consisting of the closing and opening operation of loop. Here another technique is also used i.e optimal switches in power distribution system in order to power flow formulation (OPF) to reduce no of power change network topology. Here this paper represents flows and to incorporate the network constraints implementation of feeder reconfiguration in embedded into the OPF problem. In the proposed unbalanced distribution system and objective is to approach all branches are initially considered closed reduce power loss. The performance is demonstrated and from OPF results a heuristic technique is used by a radial distribution system with 69buses, 7 determine the next loop to be broken by opening one laterals and 5 tie lines. This technique is based on switch. The above process is repeated until all loops Tabu search. The main objective of feeder are broken making distribution system radial. Here reconfiguration is reducing the system loss. The several tests are performed and the incorporation of objective function is subjected to three phase power straight line equation as continuous switch function flow equations, bus voltage limits, current transfer in OPF algorithm in association with proposed capability of feeders and radial configuration format. algorithm has provided very effective result. The A 69-bus distribution system is used to demonstrate result obtained shows that OPF algorithm helps to effectiveness of proposed technique. reduce number of power flows. The performance of [5] Charles Daniel L., Hafeezulla Khan I. and OPF algorithm has been enhanced and applicable for Ravichandran S. (2005) published a paper in which, real distribution system. they presented It has been studied that about 13% of [3] Willy M. Siti, Dan V. Nicolae and Adisa A. total power generation is wasted in the form of line Jimoh (2006) published a paper in which, they losses in distribution system. So network demonstrated generally there are two types of reconfiguration is required to reduce losses and to switches in primary distribution systems. One is open improve the reliability of power supply by changing switch and other is closed switch. Normally closed the On/OFF status of switches and tie lines. Network switch connects the line section and the open switch Reconfiguration for loss reduction based is also connects two primary feeders. And this network another technique to save energy. This technique is reconfiguration or feeder reconfiguration is the proposed by Merlin et al. He applied many process of alternating the topological structures of techniques to determine minimal loss operating distribution feeder by changing the open/close status configuration. But due its nature it became more of sectionalizing and tie switch. This new difficult. So after that distribution network reconfiguration technology helps to improve the reconfiguration for loss reduction is being applied performance of the network and the efficiency of using ant colony system algorithm. In ant colony electricity supply. In case of loss reduction process algorithm ant of the artificial colony are able to this network reconfiguration is also used. This search successively shorter efficient route by using technology requires appropriate switching strategy. the information accumulated in the form of This reconfiguration of the phase balancing is pheromone trail deposited on the edge of their considered to be more long lasting than neural traveling path. network method to turn ON and OFF different The above ACS technology having characteristics the search and power flow estimation methods like positive feedback, distribution computation, developed for power loss reduction can also be used greedy heuristic which makes this ant technology as for load balancing since the two problems are similar. the best and suitable technology for network Our contributions in this work is the global encoding reconfiguration. Here this technique has tested using for network configurations that allows for general a transmission system from tamilnadu electricity reachability and security property-based verification board. using feeder configuration model checking. In this [6] E. Romero Ramos, J.L. Martinez-Ramos, A. study, a priority list is developed using VSI to Gdmez Expdsito & A. J. Urbano Salado (2001) accommodate DG units. The appropriate allocation of published a paper in which, they presented several the DG unit has been done easily using the priority researches are done to solve network reconfiguration list. Proposed methodology for the determination of problem in distribution system. Among all the appropriate size of DG units for desired voltage techniques service restoration and loss reduction are profile using ANN technique has emerged as a very the best and most extended. In loss reduction fast and efficient tool. The appropriate size of the DG concerns with resistive loss reduction in distribution units varies from bus to bus, depending on connected system. Main goal of this power reduction technique loads. The results reveal that the integration of DG is to minimize the active power losses without units is highly effective in reducing power losses in solving any optimization process. The solution the distribution network. It is shown that with proposed in this paper takes in to account of all the appropriate sizing and allocation of DG units, voltage branches and also takes some approximation in order magnitudes of the poor voltage buses can be raised to reduce the computational time. No load flow above 0.90 p.u. Results also indicate that there is a solution is also required throughout the process since significant improvement of voltage stability for most branch losses are taken in to account. This solution is of the buses. The study may be further facilitated taken as the best solution in many cases. A linearized considering economical and geographical location model is adopted here and new concept associated factors of DG units. with network is also introduced vary clearly. In this case results obtained by very process shows that [8] G.S. Wang (M) P.Y. Wang (F), Y.H.Song(SM) & optimal reduction process is one the best approach to A.T. Johns(SM), (1996) published a paper in which, solve network reconfiguration problem in distribution they presented the co-ordinated system for fuzzy system. logic and evolutionary programming has been [7] Mew E. Baran, Felix F. Wu (1989) published a introduced for loss reduction in distribution system. paper in which, they said that recent studies show The network loss in distribution system can be that configurations of network access control is one reduced with proper configuration of networks with of the most complex and error prone network increasing in size of the distribution system. By using management tasks. For this reason, network Fuzzy logic and evolutionary programming we can misconfiguration becomes the main source for get an optimal solution. In this chapter a more network unreachability and vulnerability problems. powerful optimization technique especially for 0 and A general formulation of the feeder reconfiguration 1 integer programming problem, the co-ordinated problem for loss reduction and load balancing is system of fuzzy logic and evolutionary programming given, and a novel solution method is presented. The (FCEP) is presented. In this (FCEP) system a Fuzzy solution uses a search over different radial controller is used to record the mutation during configurations created by considering switching’s of evolutionary process. This loss reduction process is the branch exchange type. To guide the search, two preferable in most of the cases because it can quickly different power flow approximation methods with find out worldwide optimal solution. The operational varying degrees of accuracy have been developed and constraints such as powerful balance, node voltage tested. The methods are used to calculate the new limit and feeder limits are considered in this FCEP power flow in the system after a branch exchange and system. From this paper it is concluded that the larger they make use of the power flow equations developed the distribution system more nearer optimal solution for radial distribution systems. Both accuracy will be given by this fuzzy logic and evolutionary analysis and the test results show that estimation programming. So FCEP process is more applicable in methods can be used in searches to reconfigure a large distribution system. given system even if the system is not well compensated and reconfiguring involves load transfer [9] Hoyong Kim, Yunseok KO & Kyung-Hee Jung between different substations. For load balancing, a (1993) published a paper in which, they presented load balance index is defined and it is shown that that civanlaretal has suggested the simplified feeder reconfiguration algorithm to reduce power loss with respect to computational system. This paper will problem. In this paper capacitor switching and present the strategy of feeder reconfiguration to network reconfiguration are two methods for reduce power loss by using artificial neural network. optimizing the operating condition of distribution Neural network is the network which has the ability system. From the above method it is also concluded to point out the nonlinear relationship between the that by taking the advantages of both capacitor systems and load zone. Neural network determine the switching and network reconfiguration computation appropriate techniques that reduces the power loss efficiency as well as quality of reconfiguration according to variation of load patterns. The artificial improved greatly. neural network is having two groups.one group is present to determine the proper load level from the [11] Jiansheng Lei, You Deng, Ying He & Boming load and second one is to determine proper system Bang (2000), published a paper in which, they topology at the input level. It is not possible to presented a new efficient network reconfiguration show the complicated mapping between the input and strategy in distribution system. It is a very effective output since a single neuron in the network has only operation to reduce line losses and secure the system. output ability. Based on advantages of artificial The secure and the economic objective are consistent neural network the feeder reconfiguration developed goal. Therefore network reconfiguration is a problem here can solve the mapping problem of complicated of multiple decision criteria making (MCDM).This and nonlinear relationship between load zone and proposed method is applicable in balanced and system. The feeder reconfiguration through switch unbalanced condition. This process is also very control and capacitor regulator control can reduce the economical and other objective of this process is to power loss in distribution system. Artificial neural keep the system secure. This network Reconfiguration is an efficient technique to get more network developed here is based on FORTRAN practical solution. A computer based programmer has language and trained on COMPAQ 386. In the above been developed according to this technology to get it has been studied that, study power loss can reduce solution. This paper is based on hybrid flow in which using another technique i.e. feeder reconfiguration by network reconfiguration solves different problem to using artificial neural network. When this feeder get the optimal solution. Network reconfiguration is a reconfiguration strategy using artificial neural problem of multiple decisions making. So it can give network is applied in the distribution system, it has not only accurate solution but also keeps the system the capability of the high speed control strategy. It secure. This process is also an economic process. has also the capability of giving optimal solution for This proposed algorithm is also effective in both constant and sudden load variation in unbalanced condition. distribution system. III. CONCLUSION [10] Zhang Dong, Fu Zhengcai, Du Y & Zhang After going through this above survey, we come to Liuchun (2006), published a paper in which, they know that there are different techniques which are presented that both capacitor switching and network used to solve power flow study in a system and give reconfiguration are complicated combinatorial better result after optimization to control the various optimization problem. It is very difficult to combine parameters of the distribution system. In the power the both for better and effective use. In distribution system to solve power flow study in different method system capacitor switching and network has different way to solve power flow study to solve reconfiguration have mutual relationship. And in this loss reduction and voltage controlled of power method a joint optimization algorithm based on system as well as reactive power and active power combination of capacitor switching and network compensation. reconfiguration is used for loss reduction in IV. FUTURE ASPECTS distribution system. An improved adaptive genetic algorithm (IAGA) is used for capacitor switching and It must be pointed that power flow analysis is the simplified problem formulation of network very important in power system for planning, configuration are proposed to do better optimization designing and giving guide lines to control room in distribution system. He network reconfiguration is Here many authors are use different type of method simplified according to the parameter switching of to solve power flow analysis in power system. So the capacitor switching. In this method capacitors are Newton-Raphson method is very suitable technique encoded into binary strings in each location then to solve power flow in power system, it can take less network reconfiguration for each encoding string is time to reach the convergence. carried out. After that Comprehensive result is evaluated as fitness value of encoding string. The REFERENCES proposed method is able to solve the computing [1] L. F. Ochoa & A. Padilha-Feltrin, “Distribution [7] Mew E.Baran & Felix F. Wu (1989), “Network Line Models Analysis for Loss Calculation within reconfiguration in distribution systems for loss Three-phase Three-wire Power Flow Algorithms”. reduction and load balancing”, IEEE Transactions on 2004 IEEE lPES Transmission & Distribution Power Delivery, Vol. 4, No. 2, April 1989, Conference & Exposition: Latin America. University of California, Berkeley. [2] Flávio Vanderson Gomes, Sandoval Carneiro, [8] G.S. Wang(M) P.Y. Wang(F) Y.H.Song(SM) Jose Luiz R. 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[6] E. Romero Ramos J.L. Martinez-Ramos A. Gdmez Expdsito A. J. Urbano Salado (2001), “Optimal Reconfiguration of Distribution Networks for Power Loss Reduction”. Paper accepted for presentation at PPT 2001 IEEE Porto Power Tech Conference 10th -13Ih September, Porto, Portugal.