Microgrid Resource Management System using Fuzzy Logic Controller(FLC)

Transcription

1 Microgrid Resource Maagemet System usig Fuzzy Logic Cotroller(FLC) Agalaeswari.S, School of Electrical Egieerig, VIT Uiversity Cheai, Vadalur Kelambakkam Road, Cheai Abstract I this paper, a itelliget ad efficiet Fuzzy logic cotroller (FLC) based algorithm is developed for the isladed Micro grid comprisig of solar, wid, fuel cell ad battery. The itermittet ature of the reewable sources i the microgrid makes the system as depedet with the covetioal grid. The algorithm is developed for the optimum usage of the sources that ca satisfy the load demad i a efficiet maer ad reducig the usage of grid operatio. The fuzzy logic cotroller (FLC) is used to maitai the DC bus lik voltage at the required level. Keywords Microgrid, Power Maagemet, Fuzzy logic cotroller (FLC), optimum utilizatio. I. INTRODUCTION I coutries like Idia, the depedecy of the power from the covetioal sources is ot effective oe, sice the availability of the sources is o loger existed. The icrease i populatio leads to the shortage of the power ad icrease the usage of reewable sources. The combied sources of diesel geerator, solar, wid alog with the eergy storage devices such as the battery, super capacitor ad the loads is defied as the microgrid. These micro grids are havig the small trasmissio ad distributio lies where the power geerated is distributed withi the local loads. The micro grid may be self-sustaiable if the proper cotrol algorithm is beig developed for the system to distribute the reliable power to the loads [1]. The coordiatio betwee the fossil fuel sources ad the reewable sources are doe by drivig the priciples of system perspective ad busiess case model. The miistry of ew ad reewable eergy (MNRE) alog with private sector ad eergy developmet agecies has iitiated may projects for micro grid i Idia. I [1], the status of micro grids i Idia, mai ad emergig ecoomic issues i Idia view was discussed. The stadards to be followed for the grid coected distributed eergy resources; the eergy storage techologies ad the itegratio of these storage devices with the system were explaied. The authors [] has preseted a two stage optimizatio techique for schedulig the power geeratio i order to reduce the log ru average operatig cost satisfyig the coditios. I the first stage, the hourly uit commitmet of the covetioal geerators ad i the secod stage, ecoomic dispatch of the sources ad storage devices has bee doe. The modellig of the covetioal, reewable sources, battery ad load has bee developed ad the optimizatio Jamua.K, School of Electrical Egieerig, VIT Uiversity Cheai, Vadalur Kelambakkam Road, Cheai jamua.k@vit.ac.i problem has bee formulated for the eergy maagemet solutio i []. I the simulatio results, the optimum solutio for the micro grid setup subject to the costraits has proved the efficacy of the proposed algorithm. For the isolated microgrid setup cosistig of wid, solar, biogas ad battery, a efficiet eergy maagemet system with a cetral cotroller has bee implemeted that has the ability to take the decisio based o the source ad load status []. Each load ad source has bee treated as a aget i the system formig Multi aget cocept ad data acquisitio system for collectig the olie data s. The mai costrait assumed i the work was the SOC (Sate of Charge) of the battery with the miimum ad maximum as 0% ad 80%. The two operatig modes of the micro grid have bee efficietly maaged i order to reliable power supply to the cosumers by the double layer coordiated cotrol approach proposed i [4]. The schedule layer fids the ecoomic operatio from the forecasted data ad the dispatch layer affords the power to the uits from the real time data. The case studies proved that the cotrol algorithm accurately optimize the power flow ad reduces the error. A Particle swarm optimizatio (PSO) based eergy maagemet [5] usig two time scale via day ahead schedulig ad real time schedulig was proposed to carry out the optimal ad ecoomic schedulig there by maitaiig the stability of the system. From the results, it is clear that the time scale was useful for the miimizatio of the cost, maximizatio of PV ad wid efficiecy. For hybrid micro grids, a supervisory cotrol system has bee proposed i order to split the power betwee its differet sources usig robust optimal power maagemet systems [6].The optimizatio problem for maximum utilizatio of reewable sources, miimum utilizatio of fuel based sources herby icreasig the lifetime of the battery has bee formulated after takig the ucertaity coditios ito accout. Based o the simulatio results, the cost aalysis is effectively doe for differet cases ad it is proved that the maagemet system has bee successfully implemeted as two level cotrol schemes. A day ahead ad a hour ahead schedulig [] has bee employed for hadlig the ucertaities occurred i the load side ad gives a efficiet solutio for the limited resources i order to meet out the log term ad short term service meet outs. The simulatio carried with the real data showed the sigificace of the eergy maagemet systems i micro grid.

2 Figure 1. Block diagram of the Micro grid with Fuzzy Logic cotroller I this paper, the Fuzzy Logic Cotroller (FLC) based Eergy maagemet system is proposed for the Micro grid comprisig of solar, wid, fuel cell ad battery with the loads. Sectio II presets the modellig of the compoets, Sectio III discusses the differet modes of operatio of the micro grid, ad Sectio IV gives the simulatio results. Coclusio is preseted i Sectio V. II. MODELLING OF THE COMPONENTS The micro grid is havig various distributed eergy sources such as solar, wid turbie, fuel cell ad battery with the priority ad o-priority loads. Each compoet is modelled from its equivalet circuit ad it is developed i MATLAB/SIMULINK. This chapter describes the modellig of all the compoets. The figure 1 shows the block diagram of the micro grid. a) Modelig of Solar/PV cell The process of producig electricity directly from the su is called as photovoltaic process. The equivalet circuit of a solar cell is show i figure. Where is the curret geerated by the icidet su light, is the Shockley diode curret. is the umber of solar modules i series ad is the umber of solar modules i parallel. Id VT Npp Nss Isc, KIT Io () Voc, KvT exp 1 VT * I sc, KI V oc, =Short circuit curret, = ope circuit voltage, = Thermal voltage, =Temperature coefficiet of, V oc =T-T (T ad T beig the actual ad omial temperatures i K), = Diode ideality factor, usually the value lies betwee 1 ad for moo crystallie silico. Kv = Temperature coefficiet of, G I ) G T pv (, KIT () I pv, =light geerates curret at the omial coditio (for 5 C ad 1000W/m ), G=the irradiatio i W/m ad G= the irradiatio at stadard operatig coditios. Isc Rs*Nss/Npp Vpv Rsh*Nss/Npp Im Figure. Equivalet circuit of solar cell Im Id( Nss * Nppmod ules) (1) b) Modelig of wid turbie The wid turbie is desiged such that the electrical output power is 1.67kW.The base wid speed is take as 1m/s. The wid drive trai is modelled based o two mass aalogy ad the pitch agle cotroller is used for cotrollig the speed of the wid turbie. As per the Betz s limit, the maximum power that ca be extracted from the wid turbie is aroud 59% oly [7]. The power from the wid turbie ca be calculated as follows [7]:

3 1 Pm CpAV (4) Where A d is the area of the rotor (5) 4 CT RN v C p is the Tip speed ratio (6) is the torque coefficiet (7) d= diameter of the rotor, R=radius of the swept area i m, = rotatioal speed i revolutios per secod, speed without rotor iterruptio i m/sec, is take as N 0.5, = air desity pressure. 1.5 kg/ m at 15 C Cp v = wid ad at ormal c) Modelig of Fuel cell Proto Exchage Membrae (PEM) fuel cells are widely used i trasportatio ad cogeeratio applicatios. Based o the umber of stacks selected, the stack voltage is give as follows: [8] Vstack = Vcell x N (8) Vcell=E Vact Vohm Vcoc (9) Where Vcell is the cell potetial, E is the o load voltage which is foud from the Nerst equatio, Vact is the activatio voltage, Vohm is the ohmic voltage ad Vcoc is the cocetratio over voltages. Voltage(V) Power(kW) Stack voltage vs curret (,48) (6,46) Curret(A) Stack power vs curret (.85kW) 1 (.4kW) Curret(A) Figure. Characteristics of Fuel cell d) Modelig of battery Each battery is modelled as the omial output from battery is 48V.Iitial State of Charge (SoC) is assumed to be 70%. Totally five batteries are coected i series. The backup time is calculated as: Back up time = (Ah * V * o. of battery * efficiecy of battery) / load Voltage Voltage Nomial Curret Discharge Characteristic at 0.C (A) Discharge curve Nomial area Expoetial area Ampere-hour (Ah) E0 = , R = 0.048, K = , A =.8, B = A A Ampere-hour (Ah) Figure 4. Characteristics of Battery III. MODES OF OPERATION I micro grid, there are three types of mode of operatio is cosidered. I) Isladed mode of operatio II) Grid coected mode of operatio III) Trasitio mode of operatio. I the micro grid, whe more power is geerated from the sources, the excess power may be properly utilized by implemetig suitable algorithm usig cotroller. The algorithm may be cosidered as Step 1: Check the mode of operatio. If it is coected to covetioal grid, the load demad will be satisfied ad the battery is gettig charged. Step : If the micro grid is i isladed mode of operatio, the cotroller gives the commad to utilize the distributed eergy sources to its maximum, thereby reducig the usage of grid. At the poit of commo couplig (PCC), the breaker is opeed. Step : I isladed mode of operatio, if the power from the solar, wid ad fuel cell is more tha the demad, the excess power is used for chargig the battery. If the battery chargig is goig beyod its SoC, the power will be give to the grid. Step 4: If ay oe of the source is ot givig power, the cotroller checks the power available ad the load demad. If the power is less tha the demad, the battery discharges its stored eergy to the load. By the give algorithm, the cotroller is givig commad to the iverter to maitai the required power at DC bus where all the voltages are coected. IV. SIMULATION AND RESULTS The simulatio has bee doe for the isladed mode of operatio. Whe all the reewable eergy sources are coected ad workig with MMPT algorithm to extract maximum output, the battery is gettig charged. If ay of the sources is ot workig or the power from the sources is ot satisfyig the load demad, the battery comes ito operatio. The battery will discharge the power alog with the fuel cell to the load. The priority ad o-priority loads are cosidered as kw ad 4kW loads i the system.

4 Figure 7.Battery SoC level Figure 5.Voltage ad curret waveforms at the loads whe the battery gets dischargig. (No sources ad grid are coected to loads) Figure 8. Voltage ad Curret at Grid From the results, it is uderstood that the proposed Fuzzy Logic Cotroller for the isladed micro grid comprisig of solar, wid, fuel cell, battery ad loads gives the optimum results for two cases: sources are coected or producig the power output ad the if it is ot coected to the system. I both the cases, the voltage ad curret at load is maitaied at the required level. The battery is also charged to its maximum SoC. Hece the lifetime of the battery is icreased. The depedecy of the micro grid with the covetioal grid is completely reduced. V. CONCLUSION Figure 6.Voltage ad curret waveforms at the loads whe the battery gets chargig. (All sources are coected to load ad grid is ot coected to load) I this paper, the micro grid is assumed to be operated i isladed mode. I this mode of operatio, the micro grid should be self-sustaiable ad it has to give cotiuous ad reliable power supply to the load. The stable operatio of the micro grid ca be obtaied by properly desiged the cotroller. The Fuzzy logic cotroller proposed i this paper tries to maitai the costat DC level voltage at the DC bus lik before it is coected to the Grid. The voltage is sesed by the cotroller ad it is compared with the referece level. If ay deviatios are there, the cotroller gives commads to the iverter so as to maitai the voltage at costat. The future scope of this work is the grid coected operatio of the micro grid. A ew

5 algorithm may be implemeted i the same system to improve the performace ad efficiecy. REFERENCES [1] V. S. K. Murthy Balijepalli, S. A. Khaparde, C. V. Dobariy, "Deploymet of Microgrids i Idia", Proceedigs of IEEE Power ad Eergy Society Geeral Meetig, pp. 1-7, July 010. [] W. Hu, P. wag, H. Gooi, "Towards optimal eergy maagemet of microgrids via robust two-stage optimizatio", IEEE Trasactios o Smart Grid, vol. i, 016. [] Zaheeruddi 1, Muish Maas, Reewable eergy maagemet through microgrid cetral cotroller desig: A approach to itegrate solar, wid ad biomass with battery Eergy Reports 1 pp.o ,015. [4] Q. Jiag, M. Xue, G. Geg, "Eergy maagemet of microgrid i gridcoected ad stad-aloe modes", Power Systems IEEE Trasactios o, vol. 8, o., pp , Aug 01. [5] Yi Wag, Hahog Jiag, Pexiag Xig, Improved PSO-Based Eergy Maagemet of Stad-Aloe Micro-Grid Uder Two-time Scale IEEE Iteratioal Coferece o Mechatroics ad Automatio, pp.o.18-1,016. [6] H Mehdi, R S Farzad, "Robust optimal power maagemet system for a hybrid AC/DC micro-grid", IEEE Trasactios o Sustaiable Eergy, vol. 6, o., pp , 015. [7] S.Agalaeswari, K.Jamua, Costraied Power Loss Miimizatio of DC Micro grid Usig Particle Swarm Optimizatio Iteratioal Coferece o Data Egieerig ad Commuicatio Techology, Advaces i Itelliget Systems ad Computig 468, pp.o.79-89,015. [8] Zehra Ural, Muhsi Tuay Gecoglu ad Bilal Gumus, Dyamic Simulatio of a Pem Fuel Cell System Proceedigs d Iteratioal Hydroge Eergy Cogress ad Exhibitio IHEC, Istabul, Turkey, pp.o.1-1, 007.