Volume 4, Issue 3, March 2014 ISSN: 2277 128X Internatonal Journal of Adanced Research n Computer Scence and Software Engneerng Research Paper Aalable onlne at: www.jarcsse.com Power Qualty Improement n Three Phases four Wre System Usng P and Fuzzy Logc Controller A. Benazr Hajra, M.Ramya, R.Anju, M.Sathyaprya P.Kumar Dept of PG-ES AP-Dept of EEE PACET, Inda PACET, Inda ABSTRACT: Ths paper present Power qualty problem whch s the most senste problem n the power system. The objecte of the project s to reduce one of the power qualty ssue called harmoncs usng compensaton technque. Shunt Acte Power Flter (SAPF) s used to elmnate harmonc current and also t compensates reacte power. In ths project, both PI controller and Fuzzy Logc Controller based three-phase shunt acte flter s employed for a three-phase four wre systems. The adantage of fuzzy control s that t prodes lngustc alues such as low, medum, hgh that are useful n case where the probablty of the eent to occur s needed. It does not requre an accurate mathematcal model of the system. A MATLAB/SIMULINK has been used to perform the smulaton. Smulnk model s deeloped for three phase four wre system under balanced source condton and three phase three wre system for balanced load condton. The performance of Fuzzy Logc Controller and PI controller and ther Smulnk results s compared. Smulaton results obtaned shows that the performance of fuzzy controller s found to be better than PI controller. Keywords: Fuzzy logc controller, PI controller, Shunt Acte power flter, SRF method 1. Introducton Modern semconductor swtchng deces fnd a wde range of applcatons n dstrbuton networks, partcularly n domestc and ndustral loads whch are beng utlzed qute often. technque whch s based on sensng the load current. A Scheme whch s smple and easy to mplement s proposed by modfyng the aboe scheme and t works by sensng lne Currents only. In the recent years, Fuzzy Logc Controllers (FLCs) hae generated a good deal of nterest n certan applcatons. The adantages of FLCs oer conentonal controllers are that they do not need an accurate mathematcal model, they can handle non-lnearty, they can work wth mprecse nputs, and they are more robust than conentonal nonlnear Controllers. Examples of such applcatons that are wdely used are adjustable speed motor dres, unnterruptble power supples (UPSs), computers and ther perpherals, consumer electroncs applances (TV sets for example), to name a few. Those power electronc deces offer economcal and relable solutons to control and manage the use of electrc energy effectely. Howeer, most of the power electronc crcuts, exhbt nonlnear operatonal characterstcs, whch ntroduce Contamnaton to oltage and current waeforms at the pont of common couplng n case of ndustral loads. An ncrease n such nonlnearty results n arous undesrable features such as: ncreased harmoncs n current from AC mans, low system effcency and a poor power factor, cause dsturbance to other consumers, nterference n nearby communcaton networks, unexplaned computer network falures, premature motor burnouts, etc. Therefore thermal trp deces (crcut breakers and fuses) could actate to remoe the loads on that path from the lnes. These are only a few of the damages that power qualty problems may Brng nto home and ndustral nstallatons. Ths may seem lke mnor qualty problems but may brng whole factores to a standstll. Fg 1: Structure of three phase four wre APF 2014, IJARCSSE All Rghts Resered Page 1335
The proposed work contans the three phase source connected to the dode brdge rectfer. The acte flter s connected n parallel to load. The SAPF contans VSI connected n seres wth an nductor whch acts as flter connected to the PCC. The nerter uses IGBT because of ts hgh swtchng frequency. So nerter tself produces hgh frequency current wth low state loss. The structure of SAPF for three phase four wre system s shown n Fg.1.The nerter crcut trggerng depends on the control crcut output. The proposed system use PWM control to produce the pulse to trgger gate of IGBT. Instantaneous Synchronous reference frame (SRF) method s used n the proposed system to dere the compensatng sgnal. 2. PROPOSED CONTROL STRATEGIES 2.1 (a) Phase Locked Loop (PLL) The basc functon of the PLL s a feedback system wth a PI-regulator trackng the phase angle. Input s the three phases of the grd oltage and output from the PLL s the phase angle of one of the three phases. In the power supply substaton there wll be one nerter leg for each of the three phases. There are two alternates, ether assumng the grd oltages are n balance and track only one of the phases and then shft wth 120 degrees for each of the other two phases or hang three PLL system one for each phase. The man adantage of ths method s best sutable for harmonc compensaton wth snusodal and non snusodal source oltage. Fg.2. Block dagram of SF-PLL 2.1 (b) Synchronous Reference Theory In ths method only the currents magntudes are transformed and the p-q formulaton s only performed on the nstantaneous acte d and nstantaneous reacte q components. If the d-axs has the same drecton as the oltage space ector, then the zero-sequence component of the current remans narant. Therefore, the d- q method can be expressed as follows gen below d 0 L 1 q 0 L 0 0 o L0 (1) In ths strategy, the source must deler the constant term of the drect-axs component of the load (for harmonc compensaton and power factor correcton). The reference source Current can be calculated as follows: sd sq Ld so ; 0 (2) Ld p L L L 2 2 (3) 2014, IJARCSSE All Rghts Resered Page 1336
The dc component of the aboe equaton wll be: P P ( ) ( ) L L Ld dc 2 2 dc (4) Where the subscrpt dc means the aerage alue of the expresson wthn the parentheses. Snce the reference source current must to be n phase wth the oltage at the PCC t s calculated (n the α-β-0 coordnates) by multplyng the aboe equaton by a unt ector n the drecton of the PCC oltage space ector (excludng the zero-sequence component). 1 sref Ld 0 (5) s ref pl 1 sref ( ) dc s0ref 0 (6) s ref pl 1 sref ( ) 2 2 dc 2 2 s0ref 0 (7) 2.2. PI CONTROLLER The control scheme conssts of a PI controller, a lmter, and a three phase sne wae generator for reference current and swtchng sgnal generaton. The peak alue of the reference currents s estmated by regulatng the DC lnk oltage. The actual capactor oltage s compared wth a set reference alue. The error sgnal s then processed through a PI controller, whch contrbutes to the zero steady error n trackng the reference current sgnal. The output of the PI controller s consdered as the peak alue of the supply current (Imax), whch s composed of two components: (a) the fundamental acte power component of the load current, and (b) the loss component of the APF; to mantan the aerage capactor oltage at a constant alue. The peak alue of the current (I max ) so obtaned, s multpled by the unt sne ectors n phase wth the respecte source oltages to obtan the reference compensatng currents. These estmated reference currents (I sa *, I sb *, and I sc *) and the sensed actual currents ( I sa, I sb, and I sc ) are compared to a pwm, whch ges the error sgnal for the modulaton technque. Ths error sgnal decdes the operaton of the conerter swtches. Fg.3 PI Controller 2014, IJARCSSE All Rghts Resered Page 1337
2.3 FUZZY LOGIC CONTROLLER Fuzzy Logc Tools ntroduced n 1965 s a mathematcal tool for predctng uncertantes. The FLC can prode lngustc components lke low, hgh and medum. Fuzzy control system s ery useful when the processes to be controlled are complex usng the conentonal controller. The conentonal method of controllng noles more mathematcal calculaton and the tradtonal method best suts for crsp eents that ether occur or not occur. But for the eent whch ncludes uncertantes can be elmnated usng FLC as t does not need accurate modelng. Fuzzy Logc Tool s based on relate graded membershp functon. These membershp functons possess the degree of membershp between the real alues [0, 1]. The FLC system comprses manly of four components the fuzzfer, the rule base, the nference engne and the defuzzfer. 2.3 (a) Fuzzfcaton The process of conertng numercal arable to lngustc arable s done n fuzzfcaton. Here seen trangular shaped membershp functons are used and ther lngustc arables are Negate Bg (NB), Negate Medum (NM), Negate Small (NS), Zero Error (Z), Poste Small (PS), Poste Medum (PM) and Poste Bg (PB). Each membershp functon s defned usng three ertces {a,b,c} whch represents the alues correspondng to the left mnmum, peak and rght mnmum of a trangle representng the membershp functon. 2.3 (b) Fuzzy Rule Base The rule base store the lngustc control rule base need by rule ealuator. Large errors n transent state need coarse control and n small errors need fne control n steady state. Based on these elements, 49 rules of the rule table used n the paper are shown n Table I as n [1]. Table-1 Fuzzy Rules Fg.4 Membershp functon of fuzzfer nput arables 2.3 (c) Inference Engne and Defuzzfcaton: To determne a specfc or crsp alue, the rule base has to be used wth an nference method or engne followed by defuzzfcaton. Mamdan s fuzzy mplcaton and max-mn composton rule are used for nference. Centrod method s used for defuzzfcaton. Ths fuzzy rule can be desgn based on experence. Here the error (e) and change n error ( e) are consdered as nput to FLC and the output of FLC s the control current Imax. Ths s the requred acte current needed to mantan the dc lnk oltage. Ths current s used as the part of the reference current (Isa*,Isb*,Isc*) to the current controller whch controls the nerter to prode the requred compensaton current. Ths estmated reference current (Isa*,Isb*,Isc*) and the actual sensed current (Isa,Isb,Isc) are compared n the hysteress current controller and the error sgnal controls the operaton of the conerter swtches as n [10]. Each swtch of the conerter s controlled ndependently. 3. SIMULATION AND RESULTS The Fg.5 and Fg.6 shows the smulaton crcut of PI controller based shunt acte power flter for harmonc reducton. In PI controller the alue of error can be mnmzed by comparng t wth the reference alue. The reference alue for the current s extracted by usng the synchronous reference frame theory. The resultant waeforms of source oltage and current and the load oltage and current n the Fgures 7 to 10. The THD alue of load current usng PI 2014, IJARCSSE All Rghts Resered Page 1338
controller s shown n the Fg.13. The smulaton of fuzzy logc controller s shown n Fg.11 wth ts reference current extracton n Fg.12. THD alue s gen n Fg.14. From the THD analyss t s proed that FLC s better than the PI controller. Fg.5 Smulaton wth PI controller Fg.6 Smulaton for reference current extracton wth SRF method usng PI controller 2014, IJARCSSE All Rghts Resered Page 1339
Fg.7 Source Voltage Fg.8 Source Current Fg.9 Load Voltage wth PI controller Fg.10 Load Current wth PI controller 2014, IJARCSSE All Rghts Resered Page 1340
Fg.11 Smulaton wth Fuzzy Logc Controller Fg.12 Reference current extractons wth SRF Method usng fuzzy logc controller 2014, IJARCSSE All Rghts Resered Page 1341
Fg.13 THD usng PI controller Fg.14 THD usng Fuzzy Logc Controller 4. CONCLUSION In the present paper two controllers are deeloped and erfed for three phase four wre systems. Een though both of the presented controllers are capable of compensatng current harmoncs n 3 phase 4-wre systems, t can be seen that the Fuzzy Logc controller has a better dynamc performance than the conentonal PI controller. PWM pattern generaton based on carrer-less hysteress current control s used for quck response. Addtonally, n contrast to the dfferent control strateges; the d-q method s used for obtanng the reference currents n the system. Ths s due to the fact that the angle θ s calculated drectly from the man oltage whch enables an operaton whch s frequency ndependent. As a result, ths technque aods large number of synchronzaton problems. It can also be seen that the DC oltage regulaton system s a stable and steady-state error free system. Thus wth fuzzy logc and the (d-q) approach, a noel shunt acte flter can be deeloped. Smulaton results are presented to aldate the performance of the shunt acte flter. REFERENCES [1] Suresh Mkkl and Anup Kumar panda(2011), PI and Fuzzy logc controller based 3-phase four wre shunt acte flters for the mtgaton of current harmoncs wth the I d- I q control strategy, journal of power electroncs,ol.11,no.6. [2] B.Suresh Kumar,K.Ramesh reddy and V.Laltha(2011), PI,fuzzy logc controlled shunt acte power flter for three- phase four-wre systems wth balanced, unbalanced and arable loads, journal of theoretcal and appled nformaton technology. [3] Mrdul jha, S.P.Dubey(2011), Neuro-fuzzy based controller for three-phase four-wre shunt acte power flter, nternatonal journal of power electroncs and dre system,ol. 1, no.2. [4] M.Bhanu sa,m.r.p Reddy,Ch.Rambabu(2011), Power qualty mproement of three-phase four wre DSTATCOM wth fuzzy logc controller, ol.2,no.5. [5] E.Babu, R.Subramanan(2013), Neuro-fuzzy based power qualty mproement n a three phase four wre dstrbuton system usng DSTATCOM, nternatonal electrcal engneerng journal,ol.4,no.1. 2014, IJARCSSE All Rghts Resered Page 1342
[6] Brahm bebaou and chellal benachaba(2011), Power qualty enchancement usng shunt acte power flter based on partcle swarm optmzaton, journal of appled scence. [7] P.Suresh, Parthmar kalagnan Analyss of reference current generaton for apf usng pso and aco based on THD, Internatonal Journal of Adanced Technology & Engneerng Research. [8] SakshBanga,P.R.Sharmaand,ManeeshaGarg(2012) Desgn of optmal p controller usng partcle swarm optmzaton for power qualty, YMCA Unersty of Scence and Technology. [9] Wael M. Elmamlouk, Hossam E. Mostafa and Metwally A. El-Sharkawy(2013), PSO-Based PI Controller for Shunt APF n Dstrbuton Network of Mult Harmonc Sources, I.J. Intellgent Systems and Applcatons. [10] A.Ananda Kumar, J.SrnasaRao(2012), Power qualty mproement of grd nterconnected three phase four wre dstrbuton system usng fuzzy logc control, nternatonal journal of engneerng research and technology, ol.1, ssue 4. 2014, IJARCSSE All Rghts Resered Page 1343