Integration of PV based DG Source in AC Microgrid with Interconnection to Grid

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1 Indian Journal of Siene and Tehnology, ol 8(3, DOI: /ijst/015/v8i3/703, November 015 ISSN (Print : ISSN (Online : Integration of P based DG Soure in AC Mirogrid with Interonnetion to Grid A. Prudhvi Nadh and D. Ravi Kiore Department of EEE, K University, addeswaram, Guntur - 550, Andhra Prade, India; alapatihows@gmail.om, dravikiore@kluniversity.in Abstrat Objetives: This aim of the paper is to ahieve most edges from the grid-interfaing inverters, implementing in threephase four-wire distribution systems. Statistial Analysis: The work is arried out using MATAB/SIMUINK software. This work overomes the power quality problems by inluding grid interfae inverter ontrol. Findings: The grid for three phase four wire distribution is integrated with photo voltai system whih is a renewable energy supplier. Eletrial onverter is made to perform as multifuntion devie by introduing ative power filter. So this is a novel approah in whih inverter an be utilized as: Power onverter to injeting power to the grid, and it ompensates urrent unbalane, harmoni urrent, and load neutral urrent through unt Ative Power Filter. To improve the performane of the system when highly nonlinear loads are present all of these funtions an be aomplied at the same time or individually. Appliation/Improvements: This work is used in power system appliations. Keywords: Distributed Generation (DG, Photo oltai (P, Power Quality (PQ, Renewable Energy Supply (RES, Shunt Ative Power Filter (SAPF 1. Introdution Photo oltai erter along with Ative power filter 1 is used to eliminate the harmonis urrent and overheating of equipment. The grid interfae inverter is used for Injeting power to the grid by using power onverter and the non-linear, unbalaned and load urrent harmonis are ompensated. P inverter will at as a Shunt Ative Power Filter 3. between the urrent ontrolled voltage soure inverter (or Grid interfae inverter and RES. The grid interfae inverter is interonneted between the grid 4 and Renewable energy soures. The RES may be DC soure or AC soure with retifier oupled to the -link. Usually -link plays a major role is to transferring the variable power from RES to grid. A unidiretional DC/ DC onverter is used to supply high voltage DC to grid interfae inverter so power onditioned is needed to RES. Power onditioned is nothing but / or a/, before onneting on link. erter and filter onfigurations are used to onverters the DC voltage to AC voltage..1 Modeling of P System.1.1 Working of P Cell Figure 1. Proposed iruit with Renewable Energy System.. System Desription As in the Figure 1 the DC link apaitor is interfae P ells are unit of P module whih produes the urrent arries when it is enounters the sunlight. Number of suh P ells is onneted in series (or parallel faion suh that the output power will be inreased. A boost onverter is used to boost up the output voltage of P ells, if it is required. Author for orrespondene

Integration of P based DG Soure in AC Mirogrid with Interonnetion to Grid If the P Module is represented by a harateristis equation as follows aording to Figure.

2 Integration of P based DG Soure in AC Mirogrid with Interonnetion to Grid If the P Module is represented by a harateristis equation as follows aording to Figure. éexp( q( v + IRs ù v + IRs I Ipv -I0-1 - êë akt úû R. DC-ink oltage and Power Control Operation The generated power by RES is of variable nature. The link 5 plays an important role in transferring the variable power from RES to grid. And -link is interonneted between the RES and grid-interfaing inverter 3. I 1 (a In above equation urrent injeted by renewable energy soure into -link - Power generated from RES. Pinv PG + Poss I I -The urrent flow on the other side of -link. P inv - Grid-interfaing inverter power, P G - Ative power supplied to the grid, P OSS - erter losses. Assuming inverter losses are negligible P G (b Figure. Equivalent iruit of P. (a P Graph of Solar ell. (b I Graph of Solar ell. The boost onverter of solar model is used inmatlab simulation. Graph (a results of P obtained by the Matlab model (b results of I urves obtained by the Matlab.With this module we an observe harateristis of varying temperature and varying irradiation in Solar P module. Figure 3. Blok diagram representation of grid-interfaing inverter ontrol..3 Control of Grid Interfaing erter Control unit of grid interfae inverter is own in Figure 3. Neutral urrent is ompensated by four leg grid interfae inverter. If unbalaned load is onneted to point of ommon oupling in the ontrol approah ompensates the harmoni urrents, unbalaned and neutral urrents. By varying the duty ratios of inverters swithes balaned power appears at resistive load 6 of grid. The ative power flows from between renewable energy soure and grid an be obtained from regulation of the -link voltage. Therefore -link voltage output results in ative urrent (I m whih when multiplied with unity grid voltages (U a, ol 8 (3 November Indian Journal of Siene and Tehnology

3 A. Prudhvi Nadh and D. Ravi Kiore U b and U generate referene grid urrents (I a,i b, and I. Phase ok oop (P is used to obtain grid synhronous angle (θ U a sin θ U sinq U U a b æ pö sin ç q - çè 3 ø æ pö sin ç q + çè 3 ø U a, U b, U - Unity grid vetor voltages First order ow Pass Filter (PF is used to eliminates the swithing ripples on -link voltage ( in generated referene urrent signals (. Under varying generations and load onditions, PI disrete regulation 7 is used to maintained onstant link voltage. The error in the -link voltage when ompared to referene -link voltage ( is given to PI regulator to obtain a onstant -link voltage. The n th sample of PI regulator is given as I loss(n I loss(n-1 + Kp d(de(n - de(n-1 + K Id de(n Where, Kp d -Proportional gain of the PI ontroller. K Id - Integral gain of the PI ontroller. Thus instantaneous values of 3-phase referene grid urrents is omputed as I I.U a m a I I.U b m b I I.U m I, a I, b I. - Generating referene grid urrents As the fourth leg of the grid interfae inverter ompensates the neutral urrent, the grid neutral referene urrent is onsidered as a zero i.e., I 0 n The urrent errors are omputed by omparing atual grid urrents (I, a I, b I and referene grid urrents ( I a, I b, I,I n are given as I I -I aerr a a I I -I berr b b I I -I err Swithing pulses for grid interfaing inverters are produed by urrent errors by giving them to hysteresis urrent ontroller. By the following state spae equations, the model of four-leg inverter an be obtained as, d ( - ( - ( -, ( - a b n ( I + I + I + I ad, inv bd, inv d, inv nd, inv C These voltages an be modelled in terms of instantaneous bus voltage and swithing pulses of the inverter as, ( P1- P4 ( P3- P6 ( P5- P ( P7- P8 inva, invb, inv,- Three-phase a swithing voltages produed at the output terminal of inverter. et I ad,,i bd,,i d, be the harging urrents on bus due to the eah leg of inverter an be given as I ad, I (P 1 -P 4 I bd, I (P 3 -P 6 I nd, I (P 7 -P 8 Error between atual and referene urrent of inverter gives the swithing pattern of eah IGBT inside inverter will be: If, I ad, < ( I - hb then upper swith will be OFF (p 1 0 and lower swith will be ON (p 4 1 in the phase a leg of inverter. If, I < (I -h then upper swith S will be ON b 1 (p 1 0 and lower swith S 4 will be OFF (p 4 0 in the phase a leg of inverter. ol 8 (3 November Indian Journal of Siene and Tehnology 3

Integration of P based DG Soure in AC Mirogrid with Interonnetion to Grid h b - Wih of hysteresis band. Thus, the swithing pulses for the other remaining three legs an be derived. 3.

This system ontains three phase non linear load, single phase non linear load and linear load at eah phase. The non linear load is bridge retifier feeding a R load.

Finally the urrent harmonis are suppressed by injeting the ompensating urrent by using SAPF. Grid voltage will be onstant at before and after ompensation in system will be own in Figure 4.

75s the grid interfae inverter is onneted to the system as own in Figure 7. At this moment the inverter starts injeting urrent to grid from the RES.

4 Integration of P based DG Soure in AC Mirogrid with Interonnetion to Grid h b - Wih of hysteresis band. Thus, the swithing pulses for the other remaining three legs an be derived. 3. Simulation Results Simulation results for 3 phase 4 wire system are owed below by using MATAB/SIMUINK tool. This system ontains three phase non linear load, single phase non linear load and linear load at eah phase. The non linear load is bridge retifier feeding a R load. The non linear loads onneted to soure that injet urrent harmonis, whih distorts the soure urrent. And it may deteriorate the quality of power. Finally the urrent harmonis are suppressed by injeting the ompensating urrent by using SAPF. Grid voltage will be onstant at before and after ompensation in system will be own in Figure 4. And grid urrent for the three phase A, B, C as own in Figure 5. The unbalaned load urrent will be represented in Figure 6. That whih indiates loads urrent harmonis in the system. At time t 0.75s the grid interfae inverter is onneted to the system as own in Figure 7. At this moment the inverter starts injeting urrent to grid from the RES. In suh a way the grid urrent starts hanging unbalaned non linear to balaned sinusoidal urrent. Grid neutral urrent will be zero that inverter supplies load neutral urrent. And ative power will goes down to negative this means RES supply power to grid. Reative power will supplied to grid normally by grid interfae inverter. At time t 0.85s the exess flow ative power from RES to grid that indiates inreased in magnitude of grid urrent. And time t 0.95s the power will redued and the hanges in grid urrent, inverter urrent will observed learly. The inreasing and dereasing of ative power in this will be notied in Figure 8. The DC-link voltage will be remains onstant at eah and every instant of time in the system. THD value of soure urrent before ompensation will be 8.36%. After ompensation THD value of soure urrent will be 3.18%. By this simulation results the grid interfae inverter will ompensate unbalaned urrent, harmoni urrent and load reative power support respetively. Figure 4. Figure 5. Figure 6. Figure 7. Grid voltage. Grid Current. Unbalaned load urrent. erter Currents. Figure 8. (a PQ-Grid, (b PQ-oad, ( PQ-erter, (d link voltage. 4 ol 8 (3 November Indian Journal of Siene and Tehnology

5 A. Prudhvi Nadh and D. Ravi Kiore 4. Conlusion This paper suggests the use of unt ative filter as interfae between RES and to eletrial grid. Simulation results are owed by the proposed ontrol strategy. SAPF apability to injet the sinusoidal urrent with low THD and ompensated harmoni and unbalaned problems. In this paper the authors are use P system used as RES and different swithing tehniques of inverters for to redued the power quality problems. And the future work we an use hybrid soures instead P system and different logi tehniques of inverter for to improve power quality in the system. 5. Referenes 1. Jintakosonwit P, Fujita F, Akagi H, Ogasawara S. Implementation and performane of ooperative ontrol of unt ative filters for harmoni damping throughout a power distribution system. IEEE Trans Ind Appl. 003 Apr; 39(: Enslin JHR, Heskes PJM. Harmoni interation between a large number of distributed power inverters and the distribution network. IEEE Trans Power Eletron. 004 Nov; 19(6: Green TC, Marks JH. Control tehniques for ative power filters. IEE Proeedings of Eletri Power Appliations. 005 Mar; 15: Ezhilarasan S, Palanivel P, Sambath S. design and development of energy management system for dg soure alloation in a miro grid with energy storage system. Indian Journal of Siene and Tehnology. 015 Jul; 13(8. 5. Karuppanan P, Mahapatrab KK. P Synhronization with PID ontroller based on unt ative power line onditioner. International Journal of Computer and Eletrial Engineering. 011 Feb; 3(1. 6. Khadkikar, Chandra A, Barry AO, Nguyen TD. Appliation of UPQC to protet a sensitive load on a polluted distribution network. Proeedings of Annu Conf IEEE Power Eng So Gen Meeting. Montreal, Que p Blaabjerg F, Teodoresu R, iserre M, Timbus A. Overview of ontrol and grid synhronization for distributed power generation systems. IEEE Trans Ind Eletron. 005 Ot; 53(5: ol 8 (3 November Indian Journal of Siene and Tehnology 5

Capacitor Voltage Control in a Cascaded Multilevel Inverter as a Static Var Generator

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