[Boopathi, 3(1): January, 2014] ISSN: Impact Factor: 1.852

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1 IJERT INTERNATIONAL JOURNAL OF ENGINEERING CIENCE & REEARCH TECHNOLOGY A tatcom-control cheme for Grid Connected Hybrid Wind-olar Energy ystem to Improve Power Qality Boopathi.R 1, ijayakmar.g 1 PG scholar, Dept.of EEE, K..R College of Engineering, Tirchengode, India Assistant professor, Dept.of EEE, K..R College of Engineering, Tirchengode, India eeeboopathi@gmail.com Abstract Hybrid wind-solar renewable energy sorces are alternative energy sorces. It is connected to the power grid. The electric power Generated from wind and solar energy system is always flctating de to the natre of flctation in the wind and solar. The performance of the wind trbine and thereby power qality are determined on the basis of measrements and the norms followed According to the gidelines specified in International Electrotechnical Commission standard, IEC The power qality measrements are: active power, reactive power, filicker, harmonics, variation of voltage, and electrical behavior of switching operation. This paper clearly shows the existence of power qality problem de to installation of wind trbines with the grid. In this proposed scheme of a TATCOM is connected at a point of common copling with a battery energy storage system to redce the power qality problems. It energy storage system is integrated to spport the real power sorce nder flctating wind and solar power. A TATCOM control scheme to compente the reactive power demand of the load and the indction generator. To improve power qality at the main spply sorce. In this paper THD is redced to 1.3% from 13.8%. Keyword: Wind Generating ystem (WG), olar Power generating system, TATCOM, BE, Power Qality, IEC standard. I. Introdction With increase in the demand for Electricity de to increase in poplation and indstrialization, the power Generation was really a challenge now a day. If we want to the power generation increase in the of way conventional i.e., by means of non-renewable energy sorces like coal, diesel, natral gases and fossil fels, become to increases the polltion which degrades the Environment and hman life style. The need to integrate the renewable energy like wind and solar energy into power system is to minimize the environmental impact on conventional plant [1]. The integration of wind and solar energy into existing power system presents reqires the consideration of voltage reglation, stability, power qality problems. This power qality is an essential cstomer-focsed measre and is greatly affected by the operation of a distribtion and transmission network. In this proposed scheme tatic ynchronos Compentor (TATCOM) is connected at a point of common copling with a battery energy storage system (BE) to mitigate the power qality isses. Therefore TATCOM provides Reactive Power spport to wind generator and load []. The battery energy storage is integrated to sstain the real power sorce nder flctating wind power and solar. The proposed TATCOM control scheme for grid connected hybrid energy generation for power qality improvement has following objectives. Maintains Unity power factor at sorce side. TATCOM to pports Reactive power variation only from wind Generator and Load. To achieve fast dynamic response sing imple bang-bang Controller for TATCOM. II. Power Qality Improvement Power Qality tandards, Isses 1) International electro technical commission gidelines: ome gidelines of measrements and norms are specified nder IEC standard which determines the power qality of wind trbines[3,8]. The standard norms are specified. a) IEC : Measring the power qality characteristic of grid connected wind trbine. b) IEC : Measring procedre in determining the power behavior of Wind Trbine.

2 c) IEC : Measres the emission limits for flctating load and IEC : Wind Trbine performance. ) Harmonics: It is de to the operation of power electronic converters. The exactly switching gives a large redction in lower order harmonic crrent and higher order harmonics are filtered ot by sing filters. Harmonic voltage and crrent shold be in limited as per the IEC gideline. 3) oltage ariation: This is de to the flctations in the wind trbine de to wind. The voltage variation is directly related to real and reactive power variations. The variation of voltage is commonly classified as nder: oltage ag/oltage Dips. oltage wells. hort Interrptions. Long dration voltage variation. The voltage flicker isse describes dynamic variations in the network cased by wind trbine or by varying loads. Amplitde of voltage flctations depends on grid strength, network impedance, power factor and phase angle of wind trbine. Dring voltage variations freqency is in the range Hz. The IEC specifies a flicker meter that can be sed to measre flicker directly 4) Wind Trbine Location In Power ystem: It is located where the power qality is highly inflenced. Its operation and its inflence on the power system depend on the strctre of the network. 5) elf Excitation of Wind Trbine Generating ystem: The self-excitation of wind trbine generating system (WTG arises a risk eqipped with commtating capacitor. It provides the reactive power compention to the indction generator. The didvantages of selfexcitation indction machines are the fety aspect and balance between real and reactive power [4]. Grid Coordination Rle The United tate wind energy indstry took a stand in developing its own grid code for contribting to a stable grid operation. The wind generating system operate in grid the rles are realization at the distribtion network are defined as-per IEC According to these, operator of transmission grid is responsible for the organization and operation of interconnected system. 1) oltage rise () The voltage rise at the point of common copling can be approximated as a fnction of maximm apparent power max of the trbine, the grid impedances R and X at the point of common copling and the phase angle θ, given in Eq. 1. max ( R cos φ X sin φ ) = (1) Where voltage rise, max max. apparent power, Φ phase difference, U nominal voltage of grid. The Limiting voltage rise vale is < % ) oltage dips (d) The voltage dips is de to start p of wind trbine and it cases a sdden redction of voltage. It is the relative % voltage change de to switching operation of wind trbine. The decrease of nominal voltage is given in Eq.. d = K () n K Where d is relative voltage change, n is rated apparent power, k is short circit apparent power, and K is sdden voltage redction factor. The voltage dips limiting vale is acceptable <3%. 3) Flicker The measrements are made for maximm nmber of specified switching operation of wind trbine with 10- min period and -h period are specified, as given in Eq. 3. P ) n = C (ψ (3) k K Where P Long term flicker. C (ψ k ) Flicker coefficient The Limiting ale for flicker coefficient is abot 0.4, for average time of h [7]. 4) Harmonics The harmonic distortion is assessed for variable speed trbine with a electronic power converter at the common connection point. The total harmonic voltage distortion of voltage is given as in Eq n THD = 100 (4) n= 1 Where n is the nth harmonic voltage and 1 is the fndamental freqency (50) Hz. The THD limit for 13 K is < 3%. THD of crrent ITHD is given as in Eq n I THD = 100 (5) n= I 1 I where I n is the nth harmonic crrent and I 1 is the fndamental freqency (50) Hz. The THD of crrent and limit for 13 K is <.5%. 5) Grid Freqency The range of grid freqency is specified in India is Hz, for wind farm connection. III. Topology For Power Qality Improvement The TATCOM based crrent control voltage sorce inverter injects the crrent into the grid will

3 cancel ot the reactive part and harmonic part of the load and indction generator crrent, accordingly it improves the power factor and the power qality. To achieve these goals, the grid voltages are sensed and are synchronized in generating the crrent. The proposed grid connected system is implemented for power qality improvement at point of common copling (PCC), for grid connected system in Figre: 1 Fig.1. Grid connected system for power qality improvement. Wind Energy Generating ystem In the proposed scheme, the indction machine is sed becase of its simplicity, it does not reqire a separate field circit, it can accept constant and variable loads, and has natral protection against short circit. The available power of wind energy system is presented as nder in Eq.6. P 1 ρ = (6) 3 wind A wind Where ρ (kg/m) is the air density and A (m) is the area swept ot by wind trbine blade, wind is the wind speed in mtr/s. It is not possible to extract all kinetic energy of wind, therefore it extract a fraction of power in wind, called the wind trbine power coefficient C p, and is given in Eq.7 P = C P (7) mech p wind Where C p is the power coefficient, it is depends on type and operating condition of wind trbine. This coefficient C p can be express as a fnction of tip speed ratio γ and θ pitch angle. The mechanical power prodce by wind trbine is given in Eq. 8. P mech 1 = ρπ 3 R wind C p (8) Where R is the radis of the blade (m). of P systems is accomplished throgh the inverter, which is convert DC power generated from P modles to AC power sed for ordinary power spply for electrical eqipments. Inverter technology is very important to have reliable and fety grid interconnection operation of P system. The proposed strctre of P grid connected system cannot only realize photovoltaic generation, bt also sppress crrent harmonics, compente reactive power, eliminate voltage gs or swells and other power qality problems [1]. TATCOM tatic ynchronos Compentor The shnt-connected reactive-power compention device (TATCOM) that is capable of generating and/ or absorbing reactive power and in which the otpt can be varied to control the specific parameters of an electric power system. In general it is capable of generating or absorbing independently controllable real and reactive power at its otpt terminals when it is fed from an energy sorce at its inpt terminals. it is a solid state switching converter. The TATCOM considered in this is a voltagesorce converter from a given inpt of dc voltage prodces a set of 3-phase ac-otpt voltages, each in phase with and copled to the corresponding ac system voltage throgh leakage reactance[5]. The dc voltage is provided by a battery energy-storage. A TATCOM can be improve power-system performance in sch areas as the following: 1. The dynamic voltage control in Transmission and distribtion systems;. The power-oscillation damping in power transmission systems; 3. The transient stability; 4. The voltage flicker control; and 5. It also controls real power in line when it is needed. Advantages 1) It occpies small areas. ) Redces site work and time. 3) Its reponse is very fast. 4) It replaces the large passive banks and circit elements by compact converters. Grid Connected P ystems In this type of system, battery is not sed, so capital cost redces and therefore we se grid connected topology. If generated solar energy is integrated to the conventional grid, it can spply the load demand from morning to afternoon that is the particlar time range when the solar photovoltaic system (P) can fed to grid. Grid interconnection of photovoltaic power generation system has the advantage of more effective tilization of generated power. The grid interconnection Bess-tatcom The battery energy storage system (BE) is sed as an energy storage element for the prpose of voltage reglation.the BE will natrally maintain the dc capacitor voltage constant and is best sited in TATCOM since it rapidly injects or absorbed reactive power to stabilize the grid system. It also control the transmission and distribtion system in a very fast rate. When the system power flctation occrs, the BE can be sed to level the power flctation by charging

4 and discharging operation in system. The battery is connected in parallel to the dc capacitor of TATCOM[6]. The TATCOM is a three phase voltage sorce inverter having the capacitance on its DC link and connected at the point of common copling and then The TATCOM injects a compenting crrent of variable magnitde and freqency component at the bs of common copling. ystem Operation The shnt connected TATCOM with battery energy storage is connected with the interface of the indction generator and solar system and non-linear load at the PCC [13,15]. The TATCOM compentor otpt is varied according to the controlled strategy, so that to maintain the power qality norms in the grid system. The strategy of crrent control is inclded in the control scheme that defines the fnctional operation of the TATCOM compentor in the power system. The TATCOM is sing inslated gate bipolar transistor is proposed to have a reactive power spport, to the indction generator and nonlinear load in the grid system. The main block diagram of the system operational diagram is shown in Fig.. Fig.. ystem operational scheme in grid system. I. Control cheme The control scheme approach is based on injecting the crrents into the grid sing simple bangbang controller. This controller ses a hysteresis crrent controlled techniqe. Using sch techniqe, to keeps the control system variable between bondaries of hysteresis area and gives correct switching signals for TATCOM operation [,9,11,14]. The Bang-Bang crrent controller is implemented in crrent control system scheme for generating the switching signals to the TATCOM is shown in Fig. 3. The control algorithm needs the measrements of several variables sch as three-phase sorce crrent i abc, DC voltage dc, inverter crrent i iabc with the help of sensor. The actal crrent i abc and receives an inpt of reference crrent i abc are sbtracted so as to activate the operation of TATCOM in crrent control mode. Fig. 3. Control ystem cheme A. Grid ynchronization In three-phase balance system, the amplitde of RM sorce voltage is calclated at the mpling freqency from the sorce phase voltage (, b, c ) and is expressed, as mple template sm, mpled peak voltage, as in (9). sm = ( + sb + sc ) (9) 3 The in-phase nit vectors template are obtained from AC sorce of phase voltage and the RM vale of nit vector U,U sb,u c as shown in (10). 1 a b a, b =, c = c = (10) m m The generated in-phase of reference crrents are derived sing in-phase nit voltage template as, in (11) i = I., i = I., i = I. a a b b c (11) Where I is proportional to magnitde of sorce voltage for respective phases [10]. B. Bang-Bang Crrent Controller Bang-Bang crrent controller is implemented the reference crrent is generated as in (10) and actal crrent are detected by crrent sensors and are sbtracted for obtaining a crrent error for a hysteresis based bangbang controller. Ths the switching signals ON/OFF for IGBT of TATCOM are derived from hysteresis controller. The switching fnction A for phase a is expressed as (1). i i < ( i > ( i HB) HB) A A = 0 = 1 m c, (1) where HB is a hysteresis crrent-band, the switching fnction B, c can be derived from phases b and c.

5 . ystem Performance The proposed control scheme is simlated sing IMULINK in power system block set. The system performance parameter for given system is given Table I. The system performance of proposed system nder dynamic condition is also presented. oltage orce Crrent Control Inverter Operation The three phase injected crrent into the grid from TATCOM will cancel ot the distortion cased by the nonlinear load and wind generator. The three-phase inverter is connected to grid throgh the transformer. The switching signals generated from within hysteresis band. The choice of narrow hysteresis band switching in the system improves the crrent qality The choice of the crrent band depends on the operating voltage and the interfacing transformer impedance. The demanded reactive power and compented crrent for the nonlinear load is provided by the inverter. The battery is transfer real power to spported by the controller of this inverter. The three phase inverter injected voltage and crrent are shown in Fig. 4. TATCOM Performance Under Load ariations The hybrid wind solar energy generating system is connected with grid having the nonlinear load. The system performance is measred by switching the TATCOM at time t = 0.1 s in the system Fig. 4. TATCOM injected inverter oltage and Crrent. The average power flow for the proposed system can be monitored on PCC for active and reactive power flow (P,Q) of the sorce, inverter power (Pi,Qi),wind power (Pw,Qw),solar (Ppv,Qpv) and the load (PL,QL) is shown in Fig. 5. Fig. 5. Active and reactive power flow at PCC. The average power flow is measred at the point of common copling, operation of controller with and withot in the grid is shown in Fig. 6. The controller is operated for power qality mode to inject the power at t = 0.1 s, dring this operation sorce reactive power is redced to zero. Fig. 6. orce Active and reactive power At the point of common copling The average power flow is measred, with and withot controller operation in the grid. The power qality mode the controller is operated to inject the reactive power at t = 0.1 s, dring this operation sorce reactive power is redced to zero is shown in Fig. 7. Fig. 7. TATCOM Active and reactive power Table I: ystem parameters.n Parameters Ratings. 1 Grid oltage 3-phase,415,50Hz Indction Motor/Generato r 3.35KA,415,50Hz,P=4, peed=1440rpm,r =0.01Ω, R r =0.015Ω,L s =0.06H,L r =0.06 H 3 Line eries 0.05mH Indctance 4 Inverter Parameters DC Link oltage =800, DC link Capacitance =100µF, witching freqency = khz 5 IGBT Rating Collector oltage =100,Forward =50A,Gate voltage =0, Power dissipation =310W 6 Load Parameter Non-linear Load 5kW. Crrent Power Qality Improvement It is observed that the sorce crrent on the grid is affected de to the effects of nonlinear load and wind generator. The inverter otpt voltage nder TATCOM operation with load variation is shown in Fig. 8. The inverter otpt voltage does affect de to the dynamic

6 load. The sorce crrent with and withot TATCOM operation at time dration 0.1 s to 0.35 s is shown in Fig. 9. This shows that the nity power factor is maintained for the sorce power when the TATCOM is in operation. The TATCOM operation is analyzed before and after crrent waveform. The Forier analysis of this waveform is expressed and the THD of this sorce crrent at PCC withot TATCOM is 13.8%, as shown in Figre: 9. The power qality improvement is observed at point of common copling, when the controller is in ON condition. The TATCOM is placed in the operation at 0.1 s and sorce crrent with its FFT. The THD has been improved considerably and within the norms of the standard waveform is shown in Fig. 10. The above tests with proposed scheme has not only power qality improvement featre bt it also has sstain capability to spport the load with the energy storage throgh the batteries. Fig. 8. pply voltage and crrent at PCC Fig. 9. orce Crrent of withot TATCOM and FFT of orce Crrent withot TATCOM Fig. 10. orce Crrent of with TATCOM and FFT of orce Crrent with TATCOM I. Conclsion This paper analyses the factor which are power qality problems in hybrid energy conversion and non linear load to improvement power qality. The power qality isses and its conseqences on the consmer and electric tility are presented. The control system operation is developed for the TATCOM-BE in MATLAB/IMULINK for maintaining the power qality is simlated. It maintains the sorce voltage and crrent in-phase and spport the reactive power demand for the wind generator and load at PCC in the grid system, which gives an opportnity to enhance the tilization factor of transmission line. The integrated wind and solar generation and TATCOM with BE have shown the otstanding performance of system. Ths the proposed scheme in the grid connected system flfills the power qality norms as per the IEC standard References [1] A. annino, Global power systems for sstainable development, in IEEE General Meeting, Denver, CO, Jn [] harad W. Mohod,, and Mohan. Aware (010) A TATCOM-Control cheme for Grid Connected Wind Energy ystem for Power Qality Improvement IEEE YTEM JOURNAL, OL. 4, NO. 3, pp [3] Wind Trbine Generating ystem Part 1, International standard-iec , 001. [4] J. Manel, Power electronic system for grid integration of renewable energy sorce: A srvey, IEEE Trans. Ind. Electron., vol. 53, no. 4, pp , 006, Carrasco. [5] Francisco Diaz Gonzalez1, Marcela Martnez- Rojas (011) trategies for Reactive Power Control in Wind Farms with TATCOM IREC Catalonia Institte for Energy Research. [6] B.. Borowy and Z. M. alameh, (1997) Dynamic response of a stand-alone wind energy conversion system with battery energy storage to a wind gst, IEEE Trans. Energy Conversion, vol. 1, no. 1, pp [7] J.J.Gtierrez,J.Riz, L. A. Letriondo, and A. Lazkano, (009) Flicker Measrement ystem for Wind Trbine Certification IEEE TRANACTION ON INTRUMENTATION AND MEAUREMENT, OL. 58, NO., pp [8] Kyng soo kook and yil li (006) Mitigation of the Wind Generation Integration Related Power Qality Isses by Energy torage Electrical Power Qality and Utilition, Jornal ol.xii, No., pp [9] Maria Ibel Milanes Montero, Enriqe Romero Cadaval and Fermín Barrero González, (007) Comparison of Control trategies for hnt Active Power Filters in Three-Phase For-Wire ystems IEEE TRANACTION

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