Microgrids. Microgrid

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1 Journal of Advances n Computer Research Quarterly pissn: x eissn: Sar Branch, Islamc Azad Unversty, Sar, I.R.Iran (Vol. 8, No. 4, November 017), Pages: New Applcaton of Actve Power Mcrogrd Flters n a Mohamm mad Froozan 1, Seyed Hossen Hossenan, Mehrdad Abed 1) Faculty of Electrcal and Computer Engneerng, Scence and Research Branch, Islamc Azad Unversty y, Tehran, Iran ) AmrKabr Unversty of Technology (Tehran Polytechnc), Tehran, Iran hossenan@aut.ac.r; abed@aut.ac.r Receved: 016/10/0; Accepted: 016/11/0 Abstract Mcrogrds are appled not only generate power, but also producng a snusodal output voltage and supplyng nonlnear loads. In ths paper, usng A current control scheme for selectve harmonc compensatonn s proposed for shunt actve power flters. In the actve power flters usng voltage source converters that are capable of dual-use technology to mprove the qualty of the selected compensaton can be pad. Usng ths system, an mproved ndvdual harmonc and THD wth these requrements wll be modfed. Smulaton results show the effectveness of the proposed method for compensatng current harmoncs to an acceptable level. Keywords: Actve Power Flters, THD, Mcrogrd, Harmonc 1. Introducton Mcrogrd [1] may be defned as an agglomeraton of dstrbuted generaton (DG) unts usually lned through power electron c based devces (voltage source nverter) to the utlty grd. In today's envronm ment, electronc loads are very senstve to harmoncs, sags, swells and other dsturbances. So, power qualty has become as mportantt as the contnu ty of the electrcty. These nonlnear loads appearr to be prme sources of harmonc dstorton n a power dstrbuton system. Mcrogrd s suppler often use of an nterface converter (e.g. An nverter n case of DC-to-AC converson) connected to the AC power grd system (mcrogrd or utlty grd). The man role of ths nverter s to control voltage ampltude and phase angle n order to nject the desred actve and reactve power. In addton, compensaton of power qualty problems, such as voltage harmoncs, can be acheved through proper control strateges. A sngle-phase DG capable of mprovng the voltage waveform s presented n []. For voltage harmonc compensaton, DG s controlled to operate as a shunt actve power flter. In the other words, DG njects harmonc current to mprove voltage waveform m. In [3, 4] ], detecton of fundamental and harmonc voltages and computaton of the harmonc compensaton current are performe ed by two neural adaptve flters. 3

2 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed The approach of [] s based on mang the output voltage of the DG no snusodal n a way that after voltage drop on the dstrbuton lne, voltage waveform at pont of commonalty. An nterestng approach for compensaton of voltage harmoncs n an sland MG s presented n [5]. In ths approach, DGs are controlled to absorb harmonc current of the load le a shunt actve flter. Also, the method of harmonc compensaton effort sharng among DGs s presented. In [6], an approach for selectve compensaton of voltage harmoncs n a mcrogrd through proper control of The DG nterface converter s presented. The results n [7,8] show that by usng the proposed control approach fundamental and dstorton powers are properly shared between DGs and also the selected harmoncs (5th and 7th) are well compensated. Furthermore, the THD values of DGs output voltage s decreased. Invertar s can play an mportant role n the mcro-grd. The nverter s whch are placed n seres wth a source of dstrbuted generaton on the grd can be njected actve power nto the grd. In the mcrogrd some of resources connected to the grd wth a converter s. Therefore, the proposed system has the followng advantages: 1- Feedng the energy to the utlty - Harmonc elmnaton Functon and mproved power qualty Among these resources Fuel Cells offer lower emsson and hgher effcency than anther recourses such as Desel Engnes but are lely to be too expensve for many applcatons. Ths paper nvestgates the effects of selectve harmonc compensaton wll be pad when they are connected to the networ. Of course, a dfferent thng than the other papers n ths research s: Selectve APF control n harmoncs reference frames, where each harmonc s detected and controlled n ts own reference Frame, seems to be the most performance methods. The method s computaton-tme expensve, but results n better control performance [9]. Controllers may be realzed n harmoncs reference frames, n a statonary frame usng statonary frame generalzed ntegrator's [9] or repettve-based control [10], or n fundamental frame usng equvalent PI controllers [11], [1]. In ths context, ths paper proposes the applcaton of the new strategy control approach used n the b-drectonal the shunt actve power flter and power flow n the grd for current harmonc compensaton. The smulaton results of the proposed control approach are shown. The Selectve Harmonc Compensaton approach has two major advantages compared wth an unselected offer. Frst, the greater the harmonc currents of the actve power flter (APF), whch s the control system's ablty to select the most harmful harmoncs compensaton, n order to protect the load actve power flter (APF). A second advantage of the robust control aganst parameter uncertanty. Inductor parameters may change wth Frequency and such changes could easly ndvdually when adjustng controllers for each specfc frequency to be consdered. In ths paper presents a new desgn flow control for selectve harmonc compensaton of shunt actve power flter has been presented. The controller usng Remove the pole - zero, tang the load transfer functon s desgned for each harmonc frequency. 4

3 Journal of Advances n Computer Research (Vol. 8, No. 4, November 017) 3-35 Then, ths flter tested n the mcrogrd wth 1 buses n the presence of selectve harmonc compensaton for nonlnear loads were studed once. The smulaton s nvestgated n two cases. Connected to the networ and the sland state. Smulaton n the Matlab/Smuln and desred results have been acheved.. Flow Control Strategy for Actve Power Flter Control of Actve Power Flter (APF) Shunt actve power flter for three-phase PWM converter connected to the lne wth a power flter nductor s approxmately 5%. The storage component, a capactor, usually greater than the amount of power nverter s standard. Actve power flters act as a Harmonc current source Harmonc currents of equal ampltude and opposte phase harmonc load current s njected nto the lne. The proposed APF controller bloc dagram n Fgure 1 s shown. In the scheme, lne current to detect the harmonc current to flow equalzaton flter to control the flow of the flter s measured. The control system ncludes a voltage control loop, dc, array controllers n ACU manstream and the man frame of reference, along wth the lne voltage. Flow control s dvded nto two dstnct pathways: Control of the man current of reference output dc voltage controller s receved. The harmonc current control lne current harmoncs wll receve. Reference voltage, actve power flter s the sum of all output controllers. Fgure 1.Bloc dagram of the APF control [6] Dc voltage proportonal controller unt Integrator (PI) as the nput voltage and the * reference voltage V and the measured dc voltage dc V and get actve current reference dc output, the frame sync s as follows. * 1 * F1 d = K pdc + Kdc ( Vdc Vdc ) s (1) The controller gan K and pdc K are constant. current control of actve power flter s dc determned wth separate control of each harmonc. Vector model of lne nductor, n the synchronous fundamental frame, s v d F e = R F + L + jω L dt F dq e F () 5

4 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed Where R and L are the resstance and nductance of the lne nductor, v F s the flter j e voltage, F edq = ee θ s the flter current, and s the lne voltage vector. The fundamental current controller s a feedbac controller, whch provdes pole-zero cancellaton for the - planet. Ths s a complex-coeffcent PI controller, wth crosscouplng, decouplng and wth lne voltage feed forward compensaton [13] 1 ( + ) e P ( F F ) * * v F1 = K p + K jω K + edq S (3) * s the reference for the current controller. The PI gans F K and p K are selected so as Kp/K = L/R, to eep small, so that the controller has relatvely slow response, whch does not nterfere wth the harmonc current controllers. The current controller loop should be faster than Voltage loop. The smallest component of the system s desgned. Ths smplfes the desgn and maes t easer to adjust the PI controller. Fgure. Bloc dagram of the man control loop, ncludng the controllers and models, RL Fgure 3. Bloc dagram of selectve harmonc compensaton The transfer functons of the current control loop shown as: K s + K + jω K p e p H = F = 1 * F1 Ls + ( K + R + jω Ls ) + K + jω K p e e p (4) Assumng Kp/K = L/R, remove the controller zero and frst-order low-pass flter transfer functon wth a tme constant T = L/Kp s as follows: K p H 1 = = Ls + K F * F 1 p (5) 6

5 Journal of Advances n Computer Research (Vol. 8, No. 4, November 017) 3-35 Snce the purpose of control, snusodal current has been acheved, t s mportant that the bandwdth( ω bw = Kp / L) s relatvely low. The reactve current reference s non-zero when the controller s able to compensate the reactve power. Also, when the unbalanced load compensaton s desred, a negatve sequence controller must be added wth the same topology. 3. Harmonc Current Control for Selectve Harmonc Compensaton Selectve harmonc compensaton s a feature whch offers two mportant advantages n terms of flexblty, compared to a nonselectve approach. Frst, n the case of harmonc currents larger than the APF capablty, the control system has the ablty to selectvely compensate only the most harmful harmoncs, mantanng the overload protecton of the APF [6]. The other advantage s related to control of parameter uncertanty s resstant. Ths parameters may change the frequency wth the predecessor and these changes can easly be set n the controller when you ndvdually for any partcular frequency to be consdered. Ths method maes t possble to set up a controller wth a compensatve nterest s not to be used unless the control s unselected. The man problem s the selected control, the computatonal load placed on dgtal control systems. Harmonc flow control n fact produces an dentcal doman harmonc flow the opposte phase of the harmonc flow of tme. They are based on ndvdual controller desgned for each = 6n± 1 of the postve and negatve sequence harmonc pars s used. For the selectve compensaton, each unt s ndvdually possble. Rotatng reference ω frame n all the man controller on frequency e are mplemented. Snce the rotaton of the coordnate frame n a changng frequency, creates the fundamental harmonc = 6n± 1 s changed n order = 6n, where n s the rated values are correct. As a result, n ths frame, the harmonc sequence of postve and negatve a par of one ran are the same and both can be used smultaneously wth a controller wth real coeffcents for certan set frequency. Rotatng reference frame wth respect to the angular speed of s as follows: F F F e F v e = R + Ld ( )/ dt + j L ωe the model R-L lne Where denotes the ran of the frame of reference. It should be noted that, ths system has a sngle-pole R/ L+ jω e whch s mxed = 6n and n s an nteger. Conventonal PI controller wth real coeffcents wth zero-pole controller removal, though, that s of nterest for compensaton s not enough. A flow controller for the system, remove the pole and zero for the ωe does have the followng transfer functon s complex: 1 H PI = K p + ( K + jωek p ) s Where represents the harmonc order. (6) (7) 7

6 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed Harmonc flow control loop bloc dagram n the frame of reference n the fgure 5 has been shown, that the relatonshp (6) and RL model (7) the controller ndcates the harmonc values. Snce the sequence of postve and negatve drecton of rotaton s the opposte of each other, Fgure 5 only control loop for a sequence, accordng to the sgn ω e show. Due to ths, both of whch have been smultaneously compensaton sequence, ω automatc connecton (7) wth consderaton of changng the frequency e of postve and ωe negatve sequence n a frame of reference for resdent has become. Due to a change of frequency, the harmonc transfer functon H PI sequence harmonc + K s+ K Kp s+ K H =, H = s jω s+ jω p PI+ PI e and negatve sequence harmonc e H PI H PIas below: for postve In order to control the harmonc postve and negatve sequence at the same tme wth H just one controller requres that the transfer functon PI of the complance H PI + and H PIfollowng comes: H PI = H PI + + H PI = s + Kps + K s ( ω ) e Ths s the orgnal reference frame controller for each harmonc up to order = 36 runs. Assumng an deal nverter and to consder the relatonshp between () and (9) and lne voltage as flow control loop transfer functon dsorder, harmoncs, Harmonc, resde n the frame for s as follows,(10) ( F Kps + K s) H = = * Ls 3 K Rs K L s R F + p ωe + ωe ( ) ( ) ( ) ( ) Kp / K = L / R Assumng the current loop transfer functon, a second-order band-pass flter settng for the frequency ω e, becomes: H K s = = Ls K s L F p * ( ) F + p + ωe Frequency response H at the frequences fxed frame for postve, lnear scale n shape (6) has been shown. The answer for = 6 and two values for the Kp=1 and Kp=5 K = KpR / L s obtaned. Other parameters are R = 1, L = 10mH, all rghts reserved. (8) (9) (10) (11) 8

7 Journal of Advances n Computer Research (Vol. 8, No. 4, November 017) 3-35 Fgure. 4. Frequency response of harmonc current control loop n statonary Frame the functon pont The desred frequency for a sngle nterest crcle (300 Hz n fgure (6) for any two sequences regardless of the value Kp t provdes.the gan Kp tae advantage of automatc choce for lower amounts, the more selectve the controller as well as the transent reacton slower, but snce the performance lastng mode s more mportant so K p 1 small s selected for all controllers. Fnally, automatc flow of all of the separate controller conformty harmonc relatonshp (9) can be acheved. The controller full harmoncs are as follows: 7 K ps + K s H PI =, = 6n s + ( ω ) n = 1 e Bloc dagram of harmonc controller wth harmonc detector n the form (7) has been shown. (1) Fgure. 5. Harmonc current controller Because the parameters are not precsely nown predecessor s possble wth the frequency change, the relatonshp between transfer functon (1) vrtually run by 9

8 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed Kp,Kthe nterest separately for each harmonc order s set to. Ths method easly selects harmonc wll be compensated. 3.1 Harmonc Detecton Method Hgh-pass flter based on harmonc on the left sde of the fgure (7) have been shown to be dentfed. Hgh-pass flter a detector (HPF) s a fourth-order that the manstream and ts output wll be compensated by the APF harmonc current. ω H 1 ( ) * FH 0 HPF = = L s + βω0s + ω0 Where the cutoff frequency s ω 0 = 300 rad / s β = 0.8 and. HPF runs n the man frame n whch the manstream DC and can be removed wthout a phase change. (13) 4. Smulaton Fgure (8) shows a Mcrogerd wth 1 buses ncludes non-lnear load and dstrbuton generator connected to the man networ. Source dstrbuton generaton DG1 source, n fact some sort of battery wth the ablty to recharge s where the electrolyte (consstng of one or more electrolyte soluble substance) wthn a cell of electrochemcal energy that chemcal energy drectly nto electrcal current can be converted to. Electrolyte and battery out manly n addtonal tans for storage and njecton reactor pump nto the cell by the system, although there are also fed by gravty. f supples can be qucly replaced wth lqud electrolyte, they recharge. Whle at the same tme the energy consumpton for the artcle wll be restored agan. Snce the dssoluton of the rechargeable n the actve ngredents n the battery electrolyte, outer materal save reactants gves the energy densty profle and as a result, t s ndependently notable. DG scattered producton source fuel cell (Fuel Cell) whch s common to other DG, wll tae advantage of the hgher technology. Ths source s also covered by a system of nverter power supply can be connected to ts dstrbuton. Snce electrc power generaton fuel cell wth low-speed, low-voltage dc s done, so s the fuel processor unt accessores (for hydrogen producton), common dc-dc converter to ncrease the rsng level of dc ln voltage, set n a fuel cell s requred to set ths system, called a fuel cell. Three-phase full-wave rectfer dode as a nonlnear load s consdered. Nomnal voltage and frequency mcrogrd to arrange 30 V (rms phase voltage) and s 50Hz. Power and control on the part of the parameters of the tables are provded. Smulaton n the Smuln envronment/matlab use the Toolbox has been dong SmPowerSystems. Gven that the mcrogrd can connect mode and the functon of the fgure (5-8) once connected mode. 30

9 Journal of Advances n Computer Research (Vol. 8, No. 4, November 017) The Mcrogrd Connected to the Grd Fgure 6. Schematc dagram of the mcrogrd Compensaton for harmonc selectve actve flters are desgned to be placed on the bus wth the hghest THD. It s obvous that buses No 4 and 11 due to the presence of non-lnear loads are more THD than other buses. Thus, two actve flters put on buses No 4 and 11. The order harmonc spectrum contans harmoncs = 6n ± 1 harmoncs components that + = 6n +1 and -= 6n-1 postve and negatve components are harmonc. In the prevous converson functon Bnhvh flow controller was desgned at a tme when for every par of postve and negatve components of compensaton are done so = 6n ± 1 s converted to = 6n. The results of the smulatons for selectve harmonc compensaton durng the frst and second case, = 1 and = 6 s shown n Table I n mcrogrd Fgure 8. Table 1. The Results of Harmonc Compensaton Buses Current THD wthout compensaton Current THD wth selectve compensaton K=6 Current THD wth selectve compensaton K=1 BUS BUS BUS BUS BUS BUS BUS BUS BUS BUS BUS BUS As can be seen n Table 1, the THD after selectve compensaton at bus 4, or K = 6 s reduced from to

10 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed Also, reducton of 5th and 7th current harmoncs of the Bus No.4 output current s clearly shown n Fgs 7and 8. Respectvely In these Fgs., the T HD rms values of harmonc current they are shown. Ia harmonc 5th for bus Ia, harmonc 7th for bus Fgure 7. 5th and 7th harmoncs of networ current for bus 4 before compensaton Ia, harmonc 5th for bus Ia harmonc 7th for bus Fgure 8. 5th and 7th harmoncs of networ current for bus 4 after selectve compensaton wth K=6 Fnally, the results of harmonc compensaton are summarzed n Table I. The values n the table show the decrease of Total Harmonc Dstorton THD. Compensaton s acheved through njectons of harmonc current and compensaton effect of DG1 s hgh. Also, the reducton of ndvdual harmonc dstorton as a result of compensaton s Obvous. 3

11 Journal of Advances n Computer Research (Vol. 8, No. 4, November 017) Ia, harmonc 11th for bus Ia, harmonc 13th for bus Fgure 9. 11th and 13th harmoncs of networ current for bus 4 before compensaton 8 Ia, harmonc 11th for bus Ia, harmonc 13th for bus Fgure th and 13th harmoncs of networ current for bus 4 after selectve compensaton wth K=1 As t can be seen n Table I, the THD after selectve compensaton at bus 4, or K = 1 s reduced from to 1.7. Also, reducton of 11th and 13th current harmoncs of the Bus No.4 output current s clearly shown n Fgs 9and 10. As t can be observed n Table 1 when compensaton s done wth = 6, harmoncs orders 5 and 7 are also reduced. Ths results n reducng the amount of THD. For = 1 harmonc order 11 and 13 are reduced. 33

12 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed 6. Concluson A cooperatve harmonc flterng strategy for mcrogrd nterface converters n a connected networ are proposed. A current control scheme for a Selectve harmonc compensaton method for an MG wth parallel APF has been presented n ths paper. Wth the actve power flter that uses voltage source converter wth capablty of dualuse technology, the qualty of the selected harmonc can be mproved. The order of harmoncs to be compensated has effects on the qualty of compensaton. The number of controllers s reduced compared to the case when each harmonc s compensated by one separate controller. Ths method was used n a mcrogrd wth the ablty of reducng the THD and selectve harmoncs. Reference [1] S. Km, Gwonjong Yoo, Jnsoo Song, A Bfunctonal Utlty Connected Photovoltac System Wth Power Factor Correcton and U.P.S. Faclty. In Proceedngs of IEEE Photovoltac Specalsts Conference, May 1996, [] M.El-Habrou, M.K.Darwsh and PMehta. Actve power flters: A revew. IEE Proceedngs [3] W. E. Kazbwe and M. H. Sendaula. Electrc Power Qualty Control Technques. Van Nostrand Renhold, 1993, New Yor, USA. [4] R. C. Dugan, M. F. McGranaghan, S. Santoso and H. W. Beaty. Electrcal Power Systems Qualty nd. ed. McGraw-Hll, 00, USA. [5] D. A. Gonzalez and J. C. McCall, Desgn of Flters to Reduce Harmonc Dstorton n Industral Power Systems, IEEE Trans. on Industry Applcatons, vol. IA-3,pp , [6] Ludbroo, Harmonc Flters for Notch Reducton, IEEE Trans. on Industry Applcatons, vol. 4, pp , [7] J. K. Phpps, A Transfer Functon Approach to Harmonc Flter Desgn, IEEE Industry Applcatons Magazne, vol. 3, no., pp. 68-8, [8] J. C. Das, Passve Flters Potentaltes and Lmtatons, IEEE Trans. on Industry Applcatons, vol. 40, no. 1, pp. 3-41, 004. [9] M. El-Habrou, M. K. Darwsh and P. Mehta, Actve Power Flters: A Revew, Proc. IEE Electrc Power Applcatons, vol. 147, no. 5, pp , [10] B. Sngh, K. Al-Haddad and A. Chandra, A Revew of Actve Flters for Power Qualty Improvement, IEEE Trans. on Industral Electroncs, vol. 46, no. 5, pp , [11] O. Tremblay, L.-A. Dessant, A.-I. Deche,?A Generc Battery Model for the Dynamc Smulaton of Hybrd Electrc Vehcles?, 007 IEEE Vehcle Power and Propulson Conference, September 9-13, 007? Arlngton/Texas, USA [1] R Sahare, A. Davar, and A. Felach. Control of standalone sold oxde fuel cell usng fuzzy logc. In Proc. of the 35th Southeastern Symposum on System Theory, 003, volume 35, pages , March 003. [13] M.El-Habrou, M.K.Darwsh and PMehta. Actve power flters: A revew. IEE Proceedngs onlne no. oooo5 [14] Mehd Savagheb, Alreza Jallan, Juan C. Vasquez, Josep M. Guerrero, Selectve Compensaton of Voltage Harmoncs n an Islanded Mcrogrd, 011 nd Power Electroncs, Drve Systems and Technologes Conference 34

13 Journal of Advances n Computer Research (Vol. 8, No. 4, November 017) 3-35 [15] M. Crrncone, M. Pucc, and G. Vtale, A sngle-phase DG generaton unt wth shunt actve power flter capablty by Adaptve Neural Flterng, IEEE Trans. Ind. Elec., vol. 55, no. 5, pp , May 008. [16] H. Patel, and V. Aggarwal, Control of a stand-alone nverter-based dstrbuted generaton source for voltage regulaton and harmonc compensaton, IEEE Trans. Pow. Del., vol. 3, no., pp , Apr [17] T. L. Lee, and P. T. Cheng, Desgn of a new cooperatve harmonc flterng strategy for dstrbuted generaton nterface converters n an slandng networ, IEEE Trans. Pow. Elec., vol., no. 5, pp , Sept [18] Crstan Lascu, Lucan Asmnoae, Ion Boldea, and Frede Blaabjerg,Hgh Performance Current Controller for Selectve Harmonc Compensaton n Actve Power Flters. IEEE Transactons On Power Electroncs, vol., no. 5, september 007 [19] X. Yuan, W. Mer, H. Stemmler, and J. Allmelng, Statonary-frame generalzed ntegrators for current control of actve power flters wth zero steady-state error for current harmoncs of concern under unbalanced and dstorted operatng condtons, IEEE Trans. Ind. Appl., vol. 38, no., pp , Mar./Apr. 00. [0] P. Mattavell and F. P. Marafao, Repettve-based control for selectve harmonc compensaton n actve power flters, IEEE Trans. Ind. Electron., vol. 51, no. 5, pp , Oct

14 New Applcaton of Actve Power Flters M. Froozan, S. H. Hossenan, M. Abed 36