Facts Placement for Maximum Power Transfer Capability And Stability in a Transmission Line

Transcription

1 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 Facts Placeent for Maxiu Power Transfer Capability And tability in a Transission Line C.Vasavi 1, Dr. T.Gowri Manohar 2 1 Departent of EEE, VU College of Engineering, Tirupati, Andhra Pradesh, India. 2 Associate Professor, Departent of EEE, VU College of Engineering, Tirupati, Andhra Pradesh, India Abstract: Maxiu power transfer capability in the transission line is the utost iportant consideration in power systes. Facts devices are very effective and capable of increasing power transfer capability of a line, as theral liit perits, while aintaining the sae degree of stability. o, as to transfer axiu power to the consuer through a transission line. hunt FACT devices are placed at the idpoint of the transission line and degree of series copensation is provided to get the axiu possible benefit. It is observed that the optial location of facts devices deviates fro the centre of the line towards the generator side with the increase in the degree of series copensation.this paper presents a two stage approach a conventional ethod is used to deterine the optial location of shunt facts device in a series copensated line and then Fuzzy logic is used to deterine the optial placeent. The proposed ethod is considered for 13.8KV Base, 6*350 MVA, 360 k long transission line. Keywords: Fuzzy logic, Maxiu power transfer, optial placeent, shunt FACT devices, series copensation, stability. 1. Introduction During the past two decades, the increase in electrical energy deand has presented higher requireents fro the power industry, including deregulation in any countries; nuerous changes are continuously being introduced to a once predictable business. Although electricity is a highly engineered product, it is necessarily being considered and handles as a coodity, is necessary to study the stability and security of the transission syste. Thus transission systes are being pushed closer to their stability and theral liits while the focus on the quality of power delivered is greater than ever. In the odern days, the financial and arket forces are, and will continue to deand a ore optial and profitable operation of a power syste with respect to generation, transission and distribution. Now, ore than ever the deands of the power syste are lower power losses, faster response to paraeter change, higher stability and reliability.to achieve both operational and financial profitability Flexible AC Transission systes(fact)[1]based on the success of research in power electronics switching devices and advanced control technology of choice in voltage control, reactive/active power flow control, transient and steady state stabilization and iproves the functionality of existing transission syste[2] FACT technologies is allowed for iproved transission syste operation with iniu infrastructure investent. Environental constraints and econoical ipact are the two iportant constraints forced the power utilities to eet the future deand by utilizing the existing transission syste without building the new lines. FACT are effective and capable of increasing power transfer capability of line, as theral liits perits, while aintaining the sae degree of stability. Benefits of utilizing FACT devices in electrical transission systes can be suarized as follows. 1. Better utilization of existing transission syste assets. 2. Increases transission syste reliability and availability. 3. Increases dynaic and transient grid stability. 4. Increases quality of supply for sensitive industries. 5.Environental Benefits. FACT devices can be connected to a transission line in various ways.the series FACT devices (C, TCC) which are connected in series with transission line is known as series copensation. The shunt FACT devices such as (VC, TATCOM)connected in shunt with the transission line is known as shunt copensation. Issn (online) Noveber 2012 Page 152

2 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 eries copensation ais to directly control the overall series line ipedance of the transission line. The AC power transission is priarily liited by the series reactive ipedance of the transission line. A series connected can add a voltage in opposition to the transission line voltage drop, therefore reducing the series line ipedance. The voltage agnitudes of sending end and receiving end are assued are equal V =V =V. And the phase angle between the is δ the transission line odel is assued lossless and represented by the reactance X L. Figure.1 series copensation shunt copensation,especially shunt reactive copesation is used in transission syste to iprove voltage quality and to enhance the syste stability[4]shunt reactors used to reduce the over-all voltages while shunt capacitors are used to aintain voltage levels of the transission line. Figure.2 shunt copensation Optial location of facts Devices In power systes, optial location[5] of these devices is iportant, properly placed FACT devices enhances the stability of the syste,where as iproperly placed FACT ay becoe counterproductive. Many researchers found that the optial location is at K=0.5 at the idpoint of the transission line.in this paper a series copensation is provided to a transission line. One of the objectives of this paper is to find the axiu power flow corresponding optial location of shunt FACT device, when a series copensation level changes (%C). The rating of shunt FACT device is selected in such a way so as to control the voltage equal to sending end voltage at the bus of shunt FACT device. It is observed that Issn (online) Noveber 2012 Page 153

3 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 the optial location of shunt FACT device deviates fro the centre of the line towards the generator side with the change in degree of series copensation (%C) Transission line odel In this study, it is considered that the transission line paraeters are uniforly distributed and the line can be odeled by 2 port-4 terinal network. I s P s +jq s P +jq j V Transission line ABCD V Figure 3: Two port four terinal odel of a transission line The relationship between the sending end(e)and receiving end(e)quantities of the line can be written as V AV BI (1) I CV DI (2) The ABCD constants of a line length l, having a series ipedance of Z Ω/k and shunt adittance of Y /k are given by cosh sinh A D l B Z l Where y = zy and Z c = z / y C C sin l / Z (3) The active and reactive power flows at the E and E of the line cab be written as [11] cos sin cos sin P C cos C (4) 1 2 Q C sin C (5) 1 2 P C cos C (6) 2 3 Q C sin C (7) 2 3 Where 2 2 C AV / B, C V V / B, C AV / B A A, B B, V V 0 V V It is clear fro eqn 6 that the E power P reaches the axiu value when the angle δ becoes β. However the E power P of eqn 4 becoes axiu at δ=(π-β).for the siplified odel of the line, the resistance and capacitance are neglected. For such odel, the ABCD constants of the line becoe A D 10 0 B 0 xl 90 C=0 (8) Here X is the series reactance of the line in Ω/k. In this case, the line is represented by only a luped series reactance X= X L and both P and P becoe axiu at δ =90 0.such odel ay provide reasonably a good results for short transission line.when a shunt fact device is connected in a long transission line to increase the power transfer capability the following odel is designed. In this paper, it is considered that the line is transferring power fro a generation station to a load and is equipped with a series capacitor C at the centre and shunt FACT device at a point as shown in figure 4.paraeter K is used to show the fraction of line length. In this study we considered 13.8 KV Base,6*350 MVA and it is supplying a load of 30,000MVA,735 KV is considered, the series ipedance of the line is found to be Z = ( j0.9337) Ω/K at 60 Hz Issn (online) Noveber 2012 Page 154

4 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 respectively. Here the transission line is divided in to two sections (section1 and 2) and section 2 is further divided in to two sections. Each section is represented by a separate 2 port, 4-terinal network. G Vs K V (0.5-k) 0.5L V Load ection 1 ection 2 hunt FACT device Figure.4: eries copensated transission line with a shunt FACT device Maxiu power transfer capability First consider that the line is represented by its siplified odel and there is no facts device connected to the line, for such case, the axiu power transfer through the line for given values of E and E voltage agnitudes, cab be written as P =P sinδ (9) Here the axiu power p is V V / x and it occurs at an angle δ =90 0.when a shunt facts device is connected s to the line, both P and δ are increased and their values depends upon the k factor. For k=0.5 and V = V = V M both P M and δ becoe double or increases to 2 V V / x and 180 0, respectively [8].when k exceeds 0.5 both P M and decreases s after reaching the axiu value. In this paper (%c) degree of series copensation is provided for a long transission line. As the (%c)increases, the value of k changes the axiu power and corresponding angle are first deterined for various values of k. A sophisticated coputer progra has been carried out to deterine the various characteristics of the syste of fig.3 using the siplified and actual odels of the line sections. The constraints of the sae E power of section1 and E power section2 (P 1 = P 2 ) is incorporated in to the proble, in all cases,v = V = V M =1.0 p. Unless specified the axiu power P and corresponding angle δ M are deterined for various values of location K. The figure (5) to (9) shows the variation in axiu E power P, axiu E power P and transission angle with respect to degree of series copensation (%c). Fro fig (5) it can be noted that when %C = 0, the value of P increases as the value of k is increased fro zero and reaches axiu value at 13.5 p.u. when % C = 15, the value of %C=45 the value P increases and reaches axiu value 35 p.u. at k = 0.3. P increases, and reaches to 19.5 p.u. when Figure 5: Variation in axiu sending end power for the different values of %c Issn (online) Noveber 2012 Page 155

5 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 iilarly for E power P can be observed in fig (6) when the series copensation in the line is taken into account. We observe that the optial location of the shunt facts device will change and shift towards the generator side. It can observed that when %C = 45 we obtain the optial location of shunt fact device at k = and P increases to value of 22.5 p.u Figure 6: Variation in axiu receiving end power for the different values of %C In figure (7), It can be observed by using both VC and TATCOM, the angle at E power increases when % C = 0 at k = 0 the value of increases fro to its axiu value when % C=45 the value of increases at k = As the degree of series copensation increases, the stability, of the syste increases and the optial location of the shunt fact device changes. Figure 7: Variation in transission angle at the axiu E power for the different values of %c Optial location of shunt facts device Fig (8) shows the variation of axiu E power of section (1) P 1 and axiu E power of section (2) P 2 against the value of K for different series copensation levels (%c). When %C =0 the value of k = 0.45 for uncopensated line siilarly when %C = 45 the value of k = 0.25 Issn (online) Noveber 2012 Page 156

6 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 Figure 8: Variation in axiu E power of section I and E power of section II against k for different values of %c. Figure (9) shows the variation in optial off centre location of the shunt facts device against the degree of copensation level (%C) for the given /X ratio of the line. It can be observed that the optial off centre location increases linearly and reaches its highest value 55% for %c=45. Figure 9: Variation in optiu off centre location of shunt facts device against %c Optial location using fuzzy control The efficiency of ethods prior to fuzzy logic, even though good, depends ainly on the goodness of data. Fuzzy logic provides a reedy for any lack of uncertainty in the data. Fuzzy logic has the advantage of including heuristics and representing engineering judgents into the optial placeent of shunt facts device. Further ore, the solutions obtained fro a fuzzy controller can be quickly assessed to deterine their feasibility in being ipleent in the transission systes. Benefits of Fuzzy control Ipleenting expert knowledge for a higher degree of autoation obust non-linear control. elates Input to Output in Linguistic ters, which are easily understood by lay persons. These are capable of handing coplex Non-Linear, Dynaic systes using siple solutions. eduction of developent and aintenance tie. In daily hoe appliances like washing achines self focusing caeras etc. Issn (online) Noveber 2012 Page 157

7 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 Developent of Fuzzy logic syste Developing a fuzzy logic syste desires the following steps to be carried out. Creating linguistic variables of the syste. The linguistic variables are the vocabulary of the in which the rule work. Designating the structure of the syste. The structure represents the inforation flow within the syste; that is what input variables are cobined with which other variables black and so on. Forulation the control strategy a fuzzy logic rules. electing the appropriate defuzzification ethod for the application. The two ain objectives are considered ainly 1. To iprove power transfer capability 2. To iprove stability Power angle and value of k (value of fraction of line length) are odelled using fuzzy ebership functions. A Fuzzy Inference (FI) containing a set of rules is then used to deterine where the axiu power transfer capability is obtained by placing shunt facts device in various series copensation levels. Now, a Fuzzy Inference yste (FI) is developed using MAT LAB 7.12 with two input and one output variables. The inputs and outputs of FI are odeled by fuzzy ebership functions. Two inputs power angle and degree of copensation (%c) and one output for value of k are designed. The ebership functions for are triangular and are denoted by L, LM, M, HM, H. The values of per unit ranges fro [ ]. The ebership functions for (%c) are triangular and are denoted by, LM, M, HM, H, The values of per unit ranges fro [0-0.45]. The ebership functions for value of k are triangular and are denoted by L, LM, H, HM and H. The ebership functions of the variables as shown in figures given below. The values of eebership functions are given below. Figure 10: Mebership functions for L LM M HM H Figure 11: Mebership functions for %c. Issn (online) Noveber 2012 Page 158

8 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 The values of ebership function are given below L LM M HM H The values of ebership function are given below Figure 12: Mebership functions for value of k L LM M HM H ules are fraed in the for IF preise (or antecedent) THEN conclusion (or consequent). Are used to deterine the suitability of a particulars location of shunt facts device. ules are fraed we using decision atrix 1. If (input 1 is L) and (input 2 is L) then (output 1) is H (1). 2. If (input 1 is LM) and (input 2 is H) then output is (M). Like this the 25 rules are fraed by using decision atrix. AND Transission angle(δ) Degree of copensation(%) L LM M HM H L H H HM HM HM LM H HM HM HM M M H HM HM M M HM M M M LM LM H LM LM LM L L After receiving the inputs the FI, based on the rules fraed in the decision atrix, calculates the suitability ebership function of each value. This is then deffuzified in order to deterine the optial placeent of shunt facts device. Optial location (Value of k) Conventional Fuzzy ethod Method Issn (online) Noveber 2012 Page 159

9 International Journal Of Coputational Engineering esearch (ijceronline.co) Vol. 2 Issue. 7 Conclusion : This paper has presented a novel ethod to deterine the optial placeent of shunt facts device in a long transission line by using conventional ethod and fuzzy ethod. It has been found by conventional ethod the shunt fact devices has to be placed slightly off centre to get the highest possible benefit when the power flows in a particular direction the optial location fro the centre depends upon the line resistance, and it increases alost linearly as the /X ratio of the line is increased. Both the power transfer capability and stability of the syste can be further iproved if the shunt fact device is placed at the new optial location instead of at the idpoint of a line having non zero resistance. This paper also verifies the optial location of the shunt facts device by using fuzzy control ethod and found that the optial placeent is at K =0.205 shifted towards the generator side and also iproves the axiu power transfer capability of the transission line eferences [1] Zhang, B.M., Ding, Q.F The developent of Facts and its control, Advances in power syste control, operation and anageent, APCOM-97, Fourth International Conference, Vol.1, Nov. 1997, pp: [2] Paserba, J.J.; How facts controllers benefit AC transission systes, power engineering society general eeting, IEEE, Vol.2; June 2004, pp: [3] A.Edris,. Adapa, M.H.Baker, L.Bohann, K. Clark, K. Habashi, L. Gyugyi, J. Leay, A. Mehraban, A.K. Myers, J. eeve, F. ener, D.. Torgerson,.. Wood, Proposed ters and definitions for flexible AC transission syste [FACT], IEEE Transactions on power delivery, vol.12, No. 4, October 1997 [ DOI ] [4] N.G. Hingorani, L. Gyugyi, understanding facts, Concepts and Technology of Flexible AC Transission systes, IEEE press [5] M..H. Haque, 2000; Optial location of shunt facts device in long transission line IEE Proceedings on generation transission & distribution, Vol. 147, No.4, pp , 2000 [Do /ip gtd: ] [6] AADA T, H: Power syste Analysi (Mc Graw Hill, 1999) [7] Xiao-Ping Zhang, Christian ehtanz, Bikash Pal, 2006, Flexible AC Transission ystes: Modelling and Control,pringer, March 2006.IBN [8] Giuseppe, Fusco / Mario, usso, 2006, Adaptive Voltage Control in Power ystes: Modelling, Design and Applications (Advances in Industrial Control)? pringer IBN X Noveber 13, 2006 [9] P. Kundur, 1994, Power syste stability and control, EPI Power yste Engineering eries, New York, McGraw- Hill Inc., [10] Tate J.E and Thoas J.Overbye, 2005, A Coparison of the Optial Multiplier in Polar and ectangular Coordinates IEEE Transactions on Power systes, Vol.20,No 4, [DOI / TPW ] [11] M. aravanan,. M.. lochanal, P. Venkatesh, J. P.. Abraha, 2007, Application of particle swar optiization technique for optial location of FACT devices considering cost of installation and syste loadability, Electric Power yst. esearch, vol. 77, pp Issn (online) Noveber 2012 Page 160