Power Flow Analysis on IEEE 57 bus System using MATLAB

Power Flow Analysis on IEEE 57 bus System using MATLAB

Satyajit Bhuyan Sanjib Hazarika

Associate Professor, EE Department Asst. Professor, EE Department

Assam Engineering College, Guwahati, Assam, India GIMT, Azara, Assam, India

Aroop Bardalai

Associate Professor, EE Department

Assam Engineering College, Guwahati, Assam, India

Abstract- For proper planning and operation of power system, economic scheduling of generating units and to achieve power through tie line as per agreement, power flow analysis is a must. It is performed to have clear knowledge regarding bus voltage magnitude and angle and line flows. A number of methods are being used all over the world for power flow analysis. Newton Raphson method, Gauss Seidal method, fast decoupled load flow methods are a few to name. Now days, various soft computing techniques are adopted by researchers as well as practising engineers for load flow analysis to cater various needs of the research institutes and the utilities. Every method has got advantages as well as disadvantages. The objective of this paper is to develop an user friendly software to perform load flow analysis for IEEE 57 bus system. The software will be helpful for researchers, practising engineers, students of power system of various levels to carry out power flow quickly and efficiently as per their requirement. The software is developed using MATLAB programming.

Keywords – Power flow, Newton Raphson method, line loss.

1. INTRODUCTION

   An ideal power system is composed of three main networks. These are generating network, transmission network and distribution network. The power system is complete with various kinds of loads along with the above networks. Power flow analysis aims at better operation of the power system under normal as well as abnormal conditions. For augmentation of power system, contingency analysis, expansion of power system, power flow analysis is a must. In this process, profiles of the bus voltages, flow of Active and Reactive power, effect of re- arranging circuit configurations and installation of regulating devices, etc. for different loading conditions are to be analysed efficiently. Modern power systems have become so large and

   complex that these investigations should be done with some sort of computer programs. This program and subsequent assessment of power flow is commonly known as load flow analysis. Load flow study thus aims at arriving at a steady state solution of complete power networks.

   Load flow analysis of a real time power system comprising a large number of buses is complex because many data relating to power, voltage, condition of circuit breaker, position of tap of transformer, condition of reactive power source and sink being necessary. Hence it is necessary to proceed systematically by first formulating the network model of the system. A power system comprises of several buses, which are interconnected by means of transmission lines. With the help of power flow analysis, the voltage magnitude and angles for all buses in steady state condition can be obtained. For efficient power flow through the transmission line, it is required to keep voltage level of the buses within specified limit. Once the bus voltages and angles are calculated, the real and reactive power flow through the lines can be computed with the help of MATLAB. [1]

   The steady state real and reactive power supplied by a bus in a power network is expressed in terms of nonlinear algebraic equations. Therefore it would require iterative methods for solving these equations.

   In this paper Newton Raphson method for power flow analysis is used because it is preferred to Gauss Sidle method considering several computational aspects. [2]

2. NECESSITY OF POWER FLOW ANALYSIS

   Load flow studies are undertaken to determine

   1. The bus voltage magnitude and system voltage profile.

   2. The line flows.

   3. The effect of change in circuit configurations and inclusion of new circuit elements on system loading.

   4. The effect of temporary loss of transmission capacity and generations on supplied load and accompanied effects.

   5. The effect of in-phase and quadrature boost voltages on system loading data obtained from load flow can be further useful for economic system operation and system transmission loss minimization.

3. POWER FLOW ANALYSIS

   A bus is a node at which one or many lines, one or many loads and generators are connected. In a power system each node or bus is associated with 4 quantities, such as magnitude of voltage, phage angle of voltage, active or true power and reactive power in load flow problem two out of these 4 quantities are specified and remaining 2 are required to be determined through the solution of equation. Depending on the quantities that have been specified, the buses are classified into 3 categories. Buses are classified according to which two out of the four variables are specified

   1. Load bus: No generator is connected to the bus. At this bus the real and reactive power are specified. it is desired to find out the voltage magnitude and phase angle through load flow solutions. It is required to specify only Pd and Qd at such bus as at a load bus voltage can be allowed to vary within the permissible values.

   2. Generator bus or voltage controlled bus: Here the voltage magnitude corresponding to the generator voltage and real power Pg corresponds to its rating are specified. It is required to find out the reactive power generation Qg and phase angle of the bus voltage.

   3. Slack (swing) bus: For the Slack Bus, it is assumed that the voltage magnitude |V| and

   voltage phase angle are known, whereas real and reactive powers Pg and Qg are obtained through the load flow solution. [2, 8]

   Newton – Raphson Technique:

   The Newton-Raphson method is widely used for solving non-linear equations. It transforms the original non-linear problem into a sequence of linear problems whose solutions approach the solutions of the original problem. The Newton-Raphson method is powerful method of solving non-linear algebraic equations. The fundamental Newton-Raphson expression allows for convergence to be assessed by comparing power mismatches (S) against a prespecified tolerance rather than voltage comparisons.

   Then

   From which

   This Equation is in a suitable form for partial differentiation to derive the elements of the Jacobian, J given by the following matrix.

   Real and reactive power mismatch can be expressed by the following matrix equation

   A simplified flowchart of Newton Raphson method is shown in Fig 1.

   Fig1: Flowchart of Newton Raphson method

   The Newton Raphson method is the most robust power flow algorithm used in practice. However, drawback of this method lies in the fact that the terms of the Jacobian matrix must be recalculated and then the entire set of linear equations must also be solved in each iteration. [3,7]

   Fig 2: Single line diagram of IEEE 57 bus system with area devided [4,6]

4. RESULTS AND DISCUSSIONS

   Load flow analysis is carried out in IEEE 57 bus test system. Output Voltage magnitude and Voltage Angle values from Newton Raphson method for IEEE 57 bus system is presented below. All values are in per unit and angle is given in radian.

   Table 1: Voltage magnitude and angles of IEEE57 bus system

   1. CONCLUSION

      In this paper Power Flow analysis is carried out for IEEE 57 bus system using MATLAB. The aim is todetermine voltage magnitude and corresponding angles for all the buses of the network. Line flows are also calculated. It is therefore easy to calculate the system losses from these flows. It is seen that number of iterations for convergence is less for

      IEEE 57 bus system using the software even under load deviation in load buses and change in R/X ratios for various lines. Future scope may be load flow analysis of such system with inclusion of FACTs devices in some lines.

   2. APPENDIX

      Bus data and Line data for IEEE 57 Bus test system is tabulated below

      Table 2: Bus data of 57 bus system

      Table 3 : Line Data of 57 bus system

   3. REFERENCES

1. M.A.Pai, Computer Techniques in Power System Analysis, second edition, ISBN: 0-07-059363-9, Tata McGraw Hill [2005].

2. A.E. Guile and W.D. Paterson, Electrical power systems, Vol. 2. (Pergamon Press, 2nd edition, 1977).

3. Dharamjit and D.K.Tanti, Load Flow study on IEEE 30 Bussystem, International Journal of Scientific and Research Publications, Volume 2, Issue 11, November 2012, ISSN 2250-3153

4. Muralikrishna Allem , J.O.Chandle, Prediction of Weakest Area and Line in IEEE 57 Bus System, IJIRSET, Vol. 3, Issue 6, June 2014, ISSN: 2319-8753

5. Glenn W. Stagg and Ahmed H. El-Abiad, Computer Methods in Power System Analysis, McGraw-Hill [1968].

6. S. Jamali. M.R.Javdan. H. Shateri and M. Ghorbani , Load Flow Method for Distribution Network Design by Considering Committed Loads,Universities Power Engineering Conference , vol.41, no.3, pp. 856 860, sept.2006

7. N. Usha, Simulation results of eight bus system using push- pull inverter base STATCOM, Journal of Theoretical and Applied Information Technology, 2005 – 2009 JATIT.

8. C. R. Feurte Esquivel and E. Acha 'A Newton-type algorithm for the control of power flow in electrical power networks," IEEE Transactions on Power Systems, Vol.12, Nov.1997.

9. Rohit Kapahi, Load flow analysis of 132 KV substation using ETAP software, International Journal of Scientific & Engineering Research Volume 4, Issue 2, February- 2013,ISSN 2229-5518

BIOGRAPHY

Satyajit Bhuyan received B.E Degree from Dibrugarh University, India in 1986 and M.E from Jadavpur University, Kolkata, India in 2002 and Ph.D from Jadavpur University, Kolkata, India, in 2006. Currently, he is an Associate Professor in Electrical Engineering Department of Assam Engineering College, Guwahati, Assam.

Sanjib Hazarika received B.E Degree from Guwahati University, Assam, in 2007, M.Tech from Tezpur University, Assam, India, in 2010 and pursuing Ph.D in Guwahati University, Assam, India. Currently, he is an Assistant Professor in Electrical Engineering Department of GIMT, Azara, Guwahati, Assam.

Aroop Bardalai received B.E Degree from Guwahati University, Assam, INDIA in 1983 and M.E from IISC Banglore in 1988 and Ph. D Degrees from Guwahati, INDIA in 2008 . Currently, he is an Associate Professor in Electrical Engineering Department of Assam Engineering College, Guwahati, Assam.