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2 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 85 9 X Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation Dattataya N. Gaonka National Institute of Technology Kanataka Suathkal Inia. Intouction The istibute geneation system base on micotubine technology is becoming moe potential an viable istibute enegy souce in the ecent yeas. This is ue to thei salient featues such as high opeating efficiency, ulta low emission levels, low initial cost an small size (Scott, 998 an Gaonka, 6). The micotubine geneation system (MTG) pouce powe in the ange of 5-5 kw an can be opeate in stationay o mobile, emote o inteconnecte with the utility gi. Once connecte to powe istibution system, these geneatos will affects the ynamics of the system. Hence ynamic moels ae necessay to eal with issues in system planning, inteconnecte opeation an management. Thee is lack of aeuate infomation on the pefomance of MTG system when connecte to istibution netwok, even though micotubine is base on gas tubine technology, which is well establishe (Scott, 998 an Al-Hinai, ). In paticula, little evelopment has been mae on the effective moeling of these DG systems. The esign of powe electonic convete inteface, neee fo single shaft MTG system pesents a significant challenge (Nikkhajoei, 5 an Illana, ). The ynamic moels of MTG system fo isolate opeations ae epote in (Al-Hinai,, Gaonka, 6 an Gua, 4). But in these woks only isolate opeation of MTG system is consiee. The gi connecte moel of MTG system with vaious powe electonic topologies ae epote in (Azmy, 3, Fethi, 4 an Nikkhajoei 5). These topologies have thee own isavantages which ove come by the back to back convete topologies. One of the impotant technical issues ceate by DG inteconnection to the utility is the islaning of DG units (Villeneuve, 4). This moe of DG opeation is encouage by the ongoing api evelopment of new geneation technologies such as mico-tubines, win geneatos, fuel cells, photovoltaic plants an thei incease penetation in the utility netwok. Futhemoe, the emakable impovements in the powe electonic technology make it possible to esign seamless scheme fo tansfeing DG opeation between gi connecte an islaning moes without inteuption in the powe supply [Basali, ]. The intentional islaning moe opeation is utmost impotant in the case of sensitive an mission-citical inustial loas as thee is a nee to maintain a continuous an uninteupte AC powe uing planne o unplanne gi outage conitions (Tiumala,

3 86 Distibute Geneation an Illana, ). The IEEE St states the nee fo implementing intentional islaning opeation of DG systems (IEEE, 3). As a conseuence, eseach in the last few yeas has been motivate to stuy the possibility of intentional islaning of vaious DG systems. In the above context this chapte pesents the technology, application an pefomance stuy of the mico tubine geneation system. The etaile moeling of a single-shaft MTG system suitable fo gi connection in Simulink of the Matlab is given in this chapte. The algoithm fo seamless tansfe of micotubne geneation system opeation between gi connecte an islaning moe is pesente in this chapte.. Types of Micotubine Design The basic components of a micotubine ae the compesso, combusto, tubine geneato an ecupeato. It opeates on the same pinciples as taitional gas tubines. Ai is awn into the compesso, whee it is pessuize an foce into the col sie of the ecupeato. Hee, exhaust heat is use to peheat the ai befoe it entes the combustion chambe. The combustion chambe then mixes the heate ai with fuel an buns it. This mixtue expans though the tubine, which ives the compesso an geneato. Thee ae two types of mico tubine esigns available, base on position of compesso tubine an geneato. Figue (a) shows a high spee single shaft esign with the compesso an tubine mounte on the same shaft along with the pemanent magnet synchonous geneato. The geneato geneates powe at vey high feuency anging fom 5 to 4 Hz. The high feuency voltage is fist ectifie an then invete to a nomal AC powe at 5 o 6 Hz. Anothe esign is shown in Fig. (b) in which the tubine on the fist shaft iectly ives the compesso while a powe tubine on the secon shaft ives the geabox an conventional electical geneato (usually inuction geneato) poucing 6 Hz powe. The two-shaft esign featues moe moving pats but oes not euie complicate powe electonics to convet high feuency AC powe output to 6 Hz. Recupeato Exhaust gas Combusto Fuel Recupeato Exhaust gas Ai Geneato Compesso Tubine Combusto Fuel 3 phase supply High feuency Ac supply Rectifie Dc link Invete Electic powe at 5/6 Hz Compesso Inlet ai Tubine powe tubine Gea box (a) (b) Fig.. Schematic iagam of (a) single shaft MTG system (b) split shaft MTG system Geneato Micotubine tubo-machiney is base on single-stage aial flow compessos an tubines. This offes highest efficiency in vaious size anges; whee as moeate to lage

4 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 87 size gas tubines use multi-stage axial flow tubines an compessos. In a micotubine, the tubo-compesso shaft geneally tuns at high otational spee as high as,, pm base on the powe ating. The micotubine utilizes gas foil beaings (ai beaings) fo high eliability, low maintenance an safe opeation. This nees minimum components an no liui lubication is necessay to suppot the otating goup. Recupeatos ae heat exchanges that use the hot exhaust gas of the tubine (typically aoun,ºf) to peheat the compesse ai (typically aoun 3ºF) going into the combusto. This euces the fuel neee to heat the compesse ai to tubine inlet tempeatue. With ecupeato micotubine efficiency can go above 8%. 3. Powe Electonic Inteface Topologies The single shaft MTG system is wiely use fo powe geneation applications athe than split shaft ue its avantages. As iscusse, single shaft micotubine esign euies powe electonic convete inteface to convet the high feuency AC powe pouce by the geneato into usable electicity. This is a citical component in the single shaft micotubine esign. It epesents significant esign challenges, specifically in matching tubine output to the euie loa. Geneally, powe electonic inteface cicuits ae esigne to with stan tansients an voltage spikes up to seven times the nominal voltage. Micotubine High spee PM geneato Rectifie DC link Invete Filte Utility netwok Loa Battey Statup invete (a) fi fo s MTG Unit Utility system MTG Unit L Utility system c (b) (c) Fig.. (a) Passive ectifie an invete combination (b) Cycloconvete inteface moel (c) Matix convete inteface moel.

5 88 Distibute Geneation Thee ae iffeent inteface topologies available fo connecting single shaft MTG systems to gi. Figue (a) shows the passive ectifie an invete combination with DC link. This esign nees sepaate statup invete fo motoing opeation of geneato to launch the micotubine an also uing cool-own pocess, to emove heat stoe in the ecupeato an micotubine engine, in oe to potect the system components. A cycloconvete an matix convete shown in Fig. (b) an Fig. (c) can be use to inteface the micotubine geneato to the gi (Azmy, 3 an Nikkhajoei 5). These convetes iectly convet AC voltages at one feuency to AC voltages at anothe feuency with vaiable magnitue. Fo this eason, they ae also calle feuency changes. The isavantages of these convetes ae that they have ouble the numbe of switches compae to the DC link appoach an enegy stoage is not possible. If thee is no DC link, any fluctuation on eithe sie of the convete will iectly influence the othe sie. The matix convete shown in Fig. (c) can be use at lowe feuency compae to PWM base convetes. Some avantages of the matix convetes ae less themal stess on the semiconuctos uing low output feuency an absence of the DC link capacitos which inceases the efficiency an life time. The awbacks of this topology ae the intinsic limitation of the output voltage, the unavailability of a tue bi-iectional switch; absence of ecoupling between the input an the output of the convete. This may lea to some instability issues (Teooescu, 4). The back to back voltage souce convetes (VSC) inteface topology is shown in Fig. 3. This topology allows bi-iectional powe flow between the convete an the gi an hence no sepaate stating aangement is euie. At the time of stating, pemanent magnet synchonous machine acts as moto an aws powe fom the gi to bing the tubine to cetain spee. Duing the geneating moe PMSM acts as geneato an powe flows fom MTG system to gi (Fethi, 4 an Gaonka, 8). Machine sie High spee PM Micotubine geneato convete Line sie convete Dc Link Filte Utility netwok Inteface signals Contol cicuit Fig. 3. MTG system with back to back convete inteface Loa 4. Applications of MTG System Micotubine geneation system can be use fo a wie ange of applications. Some of the applications ae iscusse in this section (Scott, 998). 4. Base loa, peak shaving an stan-alone powe Micotubine base DG system can opeate in paallel with gi o with any othe geneation souce. The micotubine can augment utility supply uing peak loa peios, thus inceasing powe eliability an eucing o eliminating peak eman chages. Shaving peaks will incease oveall system efficiency which will euce investments in

6 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 89 taitional geneation, bulk tansmission, an istibution facilities. Shaving peaks will also enable the utility to seve incemental loa gowth in aeas whee thee is a shotage of substation an/o istibution feee capacity. The Micotubine can povie pime powe geneation whee the electic utility gi is not eaily available o whee sevice is uneliable. 4. Combine Heat an Powe Cogeneation, o combine heat an powe (CHP) geneation efes to the pocess of utilizing the heat pouce by a combustion engine as enegy output. Duing nomal opeation, micotubine pouces significant uantities of high-tempeatue exhaust that can be easily integate with a heat exchange an a hot wate loop to pouce valuable enegy output. Fom a cost-benefit pespective, this yiels a significant saving compae to heating fuel an puchasing powe. When the heat enegy is utilize, oveall system fuel efficiency can ange between 7 an 9+%. 4.3 Resouce Recovey Flae gases often have low-enegy yiel o high contents of coosive sou (hyogen sulphie, o H S) gas, making them an infeasible fuel souce fo conventional geneatos. Micotubine, on the othe han has no poblem opeating exclusively on low-enegy gases. Micotubine can also be use in oil an gas ecovey applications. With the ability to convet unpocesse casing gas that contains up to 7% coosive H S gas, micotubine can eliminate the nee fo flaing. At the same time, thei powe output euces o eliminates the nee fo aitional electicity souces. 4.4 UPS an Stan by Sevices The micotubine technology can be integate into a wie vaiety of poucts an systems. Uninteuptible powe supplies, all-in-one combine heat an powe systems, an weling machines ae just a few examples fo oiginal euipment manufactuing applications. 5. Moeling of MTG System Components The integate moel of MTG system consists of micotubine, pemanent magnet synchonous machine, machine an gi sie convetes with contol an filte. The moeling of iniviual components is escibe in this section (Rowen, 983). Spee efeence Spee + - Spee contolle Acceleation contol Low value selecto Tempeatue contol Fuel contol Fig. 4. Block iagam of micotubine system with contols Compesso, gas tubine ynamics & Combusto Toue output

7 9 Distibute Geneation 5. Micotubine The block iagam of micotubine along with its contol is shown in Fig. 4. This consists of fuel, spee, acceleation an tempeatue contol along with the combusto an tubine ynamics. The implementation of micotubine moel using Simulink of the Matlab is shown in Fig 5. Spee govene X.s+ Y.s+Z Ref. spee -K- Temp. Ref. 3.3s+.5s. s Temp. contol min Themocouple Vce limits Accel. contol u/t.5s+ No loa fuel flow Fig. 5. Simulink moel of the micotubine T.3 Tubine Toue output Raiation shiel. -K- 5s+.8 P.U. system spee input Value positione.5s+ Fuel eman.3*(u-.3) Tubine.5*(-u) F=7*(-u) F F Exhaust elay Tubine F F=55*(-u) F Fuel system.4s+ Combusto.s+ Gas tubine ynamics Spee an acceleation contol: The spee contol opeates on the spee eo fome between a efeence (one pe-unit) spee an the oto spee of the MTG system. It is the pimay means of contol fo the micotubine une iffeent loa conitions. Spee contol is usually moele by using a lea-lag tansfe function o by a PID contolle (Hajagos, ).Acceleation contol is use pimaily uing gas tubine statup to limit the ate of oto acceleation pio to eaching goveno spee. This amelioates the themal stess encountee uing statup. Acceleation contolle is an integato as shown in Fig. 5 an acts on the eo between the eivative of p. u. spee of geneato an constant efeence signal. Tempeatue contol: The tempeatue contol is the common metho of limiting gas tubine output at a peetemine fiing tempeatue, inepenent of vaiation in ambient tempeatue o fuel chaacteistics. The fuel bune in the combusto esults in tubine toue an in exhaust gas tempeatue. The exhaust gas tempeatue is measue using a seies of themocouples incopoating aiation shiels. The themocouples an aiation shiels ae epesente by tansfe functions as shown in Fig. 5.The output fom the themocouple is compae with a tempeatue efeence value. Nomally the efeence value is highe than the themocouple output. This foces the output fom the tempeatue contol to stay on the maximum limit pemitting uninhibite goveno/spee contol. When the themocouple output excees the efeence tempeatue, the iffeence becomes

8 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 9 negative an it stats loweing the tempeatue contol output. When the tempeatue contol output becomes lowe than the spee goveno output, the fome value will pass though the low value selecto to limit the output an the unit will opeate on tempeatue contol (Rowen, 983). Fuel contol: The outputs of the spee goveno, acceleation contolle an tempeatue contol system go as input to a minimum value selecto, which selects the lowest value among thee inputs. The output of low value selecto epesents the least amount of fuel euie fo that paticula opeating point an is enote as Vce. The pe unit value fo Vce, coespons iectly to the pe unit value of mechanical powe on tubine base in steay state. The output of the low value selecto is compae with maximum an minimum limits. The maximum limit acts as back up to tempeatue contol an is not encountee in nomal opeation an minimum limit is moe impotant ynamically. The out put of the Vce limite is multiplie by.77 an offset by no loa fuel flow value to ensue the continuous combustion pocess. The fuel flow contols ae epesente by seies of blocks incluing the valve position an flow ynamics. Compesso, combusto an tubine: Tubine is a linea, non ynamic evice with the exception of the oto time constant. Thee is a small tanspot elay, which is the time lag associate with the compesso ischage volume. Anothe tanspot elay is ue to the tanspot of gas fom the combustion system though the tubine. The values of these elays ae given in (Rowen, 983 an Hajagos, ]. Both the toue an exhaust tempeatue chaacteistics of the single shaft gas tubines ae essentially linea with espect to fuel flow an tubine spee. They ae given by following euations. Tubine toue = T.3 ( w f.3).5 ( N) () Exhaust gas tempeatue = T T 7 ( w ) 55 ( N ) () ex Whee T R is the efeence tempeatue, N is pe unit spee an W f is pe unit fuel eman signal. The constant value.3 in the tubine toue expession epens on the enthalpy o highe heating value of the gas steam in the combustion chambe. In this chapte micotubine is assume to opeate une nomal opeating conitions. Tempeatue contol an acceleation contol ae of no significance une nomal system conitions. They can be omitte in the tubine moel. In this chapte electo-mechanical behavio of micotubine is ou main inteest. The ecupeato is not inclue in the moel as it is only a heat exchange to aise the enegy efficiency. Also ue to the vey slow esponse time of the ecupeato, it has little influence on the timescale of ynamic simulations pesente in this chapte. Thus micotubine moel shown in Fig. 5 is simplifie by using the above assumptions an esulte moel is use in this investigation. R f 5. Pemanent Magnet Synchonous Machine (PMSM) The evelopment of avance magnetic mateials, powe electonics an igital contol systems ae making pemanent magnet (PM) machine as an inteesting solution fo a wie ange of applications. The avantages of PMSM compae to othe AC machines ae its simple stuctue, high-enegy efficiency, eliable opeation, high powe ensity an possibility of supe high spee opeation. Recent impotant applications of pemanent magnet synchonous machine ae in the aea of istibute geneation, mainly in win an

9 9 Distibute Geneation micotubine geneation systems. An avantage of a high spee geneato is that the size of the machine eceases almost in iectly in popotion to the incease in spee, leaing to a vey small unit. Supe high spee PMSM is an impotant component of single shaft MTG system. The mathematical moel of a PMSM is simila to that of the woun oto synchonous machine. + Rs Ls L i Rs Ls L + i - v v - - (a) (b) Fig. 6. -axis euivalent cicuit moel of the PMSM a) -axis b) -axis m + - The -axis euivalent cicuit moel of PMSM is shown in Fig. 6 The PMSM ive moeling is one with the assumption of sinusoial istibute winings, satuation is neglecte, ey cuents an hysteesis losses ae negligible (Pillai, 989). With these assumptions the stato euations of the PMSM in the oto efeence fame ae: v v R s i R i s L L i t i t p L i p L i Whee, the stato esistance is enote by R s,, the -axis an -axis inuctances ae L an L espectively, Φ m is the flux linkage ue to the pemanent magnets, v an v ae axis voltages. In the -fame, the expession fo electo-ynamic toue becomes: pw m (3) (4) T e.5 p ( mi ( L L ) ii ) The euation fo moto ynamics can be given as: ( Te F T t J t v v v 3 cos sin cos( ) sin( ) M ) cos( ) v sin( ) v v a b c (5) (6) (7) (8) v v v a b c cos cos ( ) cos( ) sin sin( ) sin( ) v v v (9)

10 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 93 Whee p is the numbe of pole pais, T e is the electomagnetic toue, F is combine viscous fiction of oto an loa, ω is the oto spee, an J is the moment of inetia, θ is oto angula position an T m is shaft mechanical toue. The, vaiables ae obtaine fom a, b, c vaiables though the Pak tansfom given in (8) an a, b, c vaiables ae obtaine fom the, vaiables though the invese of the Pak tansfom given in (9). 5.3 Machine Sie Convete Contol Theta ouput signals of iabc PMSM 3 Spee(w) wef theta abc ew PI ief i i ief Theta e PI De coupling i V i w v e PI v v theta abc To PWM Gen. Fig. 7. Machine sie convete contolle implemente in Simulink Figue 7 shows the Machine sie convete contolle implemente in Simulink of the Matlab. The commane spee ω ef is pe-calculate accoing to the tubine output powe an set to the optimum spee ( Moimoto, 994 an Fethi, 4). Base on the spee eo the commane axis efeence cuent i ef is etemine though the spee contolle. In this system the following PI contolle is employe as the spee contolle. i ef K e p K () Whee, K an P K I ae the popotional an integal gains of the spee contolle espectively while, e is the eo between the efeence spee an measue spee. The commane optimal -axis cuent i ef i e t is obtaine fom the maximum allowe phase voltage an phase cuent constaints of the ive, which ae given in () an (). These constaints epen upon the machine ating an DC link voltage. v v V () i max i I () Using the above constaints an neglecting the voltage op ue to the stato esistance, the optimal -axis cuent fo a non salient PMSM (L =L ) can be obtaine as: Vmax L I max m I (3) L Consieing the elationship max function of the -axis cuent i, as : I i i max m the optimal -axis cuent can be given as a

11 94 Distibute Geneation m V L max i ( i ) L L (4) L Base on the cuent eos the - axis efeence voltages ae etemine by PI contolles, as given in (5) an (6). v v Pi i Ii K e K e t L i (5) i K e K e t ( L i m ) (6) Pi i Ii i Whee, K an Pi K Ii ae the popotional an integal gains of the contolle espectively. ei ief i is the -axis cuent eo an ei ief i is the -axis cuent eo. The ecoupling tems ( L i ) an ( L i ) ) ae use in (5) an (6) espectively fo ( m the inepenent contol of an -axis cuents. The commane -axis voltages (v, v ) ae tansfome into a, b, c vaiables (v a, v b, v c ) an given to the PWM geneato to geneate the gate pulse fo machine sie convete. 5.4 Line Sie Convete Contol The objective of the supply-sie convete is to keep the DC-link voltage constant, egaless of the magnitue an iection of the oto powe. A vecto contol appoach is use hee, with the efeence fame oiente along the stato (o supply) voltage vecto position (Pena, ). Vcef 3 vc iabc PI theta abc ief i i wl -wl PI v v abc theta to PWM gen. vabc ief vabc Theta PLL v Fig. 8. Gi sie convete contolle. v PI Gi connecte moe: The PQ contol stategy with DC link voltage contol is employe fo gi connecte opeation of MTG system. In this scheme the powe injecte to the gi is egulate by contolling the injecte cuent. The contol stuctue fo gi-connecte moe opeation of MTG system is shown in Figue 8. The stana PI-contolles ae use to egulate the cuents in the synchonous fame in the inne contol loops as they have satisfactoy behavio in egulating DC vaiables, as well as filteing an contolling can be easily achieve. Anothe PI contolle is use in the oute loop to egulate the capacito voltage in accoance with the cuent injecte in to the gi. Its output is the efeence fo the active cuent PI contolle. In oe to obtain only a tansfe of active powe, the i cuent efeence is set to zeo. An also to have inepenent contol of the cuent

12 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 95 components i an i the ecoupling voltage components ae ae to the output of cuent PI contolles. Convete voltages can be given as: v a ( t) V cos ( t) 4 v ( t) V cos ( t ) 3 b v c ( t) V cos ( t ), 3 3, 3 3 (7) component in synchonous efeence fame with ecoupling tems can be epesente as: i u Ri L v L i t (8) i u R i L Li v t (9) Whee, the cuents ae contolle by means of the ight choice of the convete sie voltages. Two PI egulatos ae comman a PWM moulato to geneate the voltage that shoul contol the cuent. Islaning moe: The islaning moe opeation of single shaft MTG system euies a contol iffeent fom that of gi connecte moe. In this moe, the system has aleay been isconnecte fom the utility. Theefoe the voltage an feuency is no longe egulate by it. Thus the output voltages ae to be contolle in tems of amplitue an feuency which leas to contol of the eactive an active powe flow. vcef PI vc vef PI v vabc w s abc theta Theta vef v v PI v vv abc theta to PWM gen. vabc Fig. 9. Contol stuctue fo islaning moe opeation This is one by contolling the amplitue an feuency of the moulating input-signal to the PWM invete. The contol stuctue fo islaning moe is epicte in Fig. 9. It consists of output voltage an DC link voltage PI contolles. The output voltage contolles contol the output voltage with a minimal influence fom natue of the loa cuents o loa tansients. A stana PI contolle opeating in the synchonously otating cooinate system whee, v is kept to zeo is use. The DC voltage PI contolle contols the DC voltage level base on the efeence. Fo fast esponse the output of the DC voltage contolle is fee fowae to the voltage contolle output. The DC link voltage contolle acts only when the DC link voltage is below the efeence an it lowes the voltage efeence of the main voltage contolle in oe to avoi invete satuation. The feuency contol is one by integating the constant efeence feuency ω an using it fo cooinate tansfe of the voltage components fom abc to an vice vesa. In islaning moe, when thee is

13 96 Distibute Geneation moe geneation than the loa eman the DC link voltage becomes highe than the efeence..fo this case amping choppe contol is implemente. By activating this contol excess enegy stoe in the Dc link is issipate in the amping esisto an hence maintain the Dc link voltage constant (Teooescu, 4). A popotional contolle is use to contol the uty cycle of the choppe. In pactice, batteies ae use to soe the excess enegy. One of the impotant euiements in the inteconnection esign of the powe electonic convete inteface DG system is that of synchonization to the utility system. (Chung, ) Synchonism of convete contol with the gi is achieve by using a PLL. The Simulink block iagam of the PLL use in this wok is shown in Fig., whee is the gi phase angle, v an x v ae the gi voltage components in the stationay efeence y fame. The philosophy of the PLL is that the sine of the iffeence between gi phase angle an invete phase angle can be euce to zeo using a PI-contolle, thus locking the invete phase to the gi with small aguments ( sin( ) ( ) ). The output of the PI contolle is the invete output feuency that is integate to obtain the invete phase angle. In oe to impove the ynamic esponse at statup, the nominal feuency of the gi, is fee fowae to the output of the PI contolle. The majo isavantage of the o thee phase PLL is its sensitivity to gi voltage unbalance. Some attempts ae mae to exten this metho fo unbalance voltages base on Symmetical components (Ghatemani, 4). v Positive seuence computation a v b vc abc to xy cos( ) v x v x y v v x y v v sin( ) Input voltages Fig.. PLL implemente in the Simulink y o sin u PI /s + cos 6. Simulation an Results Figue shows the simulation moel implemente in the SimPoweSystems of the MATLAB to stuy the pefomance of the MTG system opeation in gi connecte moe (Gaonka, 8). The utility netwok, to which the MTG system is connecte, is epesente by a 3 phase sinusoial souce with its impeance. The seies RL filte is use at the gi sie of the MTG system. The simulation paametes of the moel ae given in Table. The mico tubine geneation system takes pe unit spee of the PMSM as input. The toue output of the micotubine is given as an input mechanical toue (T m ) to the PMSM. The iection of the toue T m, is positive uing motoing moe an mae negative uing geneating moe of the PMSM. The machine sie convete contolle takes the oto angle

14 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 97 spee an 3 phase stato cuent signals of the PMSM as inputs. In all the pesente cases the voltage acoss the capacito is zeo, at the stating of simulation. Duing the stat up, the PMSM opeates as a moto to bing the tubine to a spee of 3, pm. In this case powe flows fom the gi to MTG system. MIcotubine Moel Toue output Spee input Utility netwok A B C B aa bb cc B aa bb cc Filte A A B B C C Line Sie convete g A B C + - DC link Machine Sie convete + - g A B C PMSM Tm A B C Measuement is_abc m m wm thetam Loa A B C PWM Gen. [Vabc_B] In Pulses Out In In3 [Iabc_B] Vc v + - Gi sie convete contol PWM Gen. Pulses In Out In In3 Machine sie convete contol Theta Spee Thee phase cuent Fig.. Matlab/ SimPoweSystems implementation of MTG system connecte to gi. Gi paametes 48V, 6Hz, R s =.4Ωan L s =mh Filte Paametes L=.97mH, R=.Ω Switching Feuency Gi sie convete = 8 Khz Machine sie Convete = KHz DC link capacitance 5 μf PI contolles sampling time μsec PMSM paametes 48 V, 3 kw,.6 KHz, 96 pm R s =.5 Ω, L =L =.6875 H Micotubine paametes Gain(K)=5,X=.4,Y=.5 an Z= Table.Simulation paametes fo the moel shown in Fig. Figue shows that the micotubine eaches the set value of spee in.4 sec. At this spee, the MTG system absobs powe of 5.4 kw as shown in Fig. (b). The PMSM teminal voltage eaches 9 V at a feuency of 5 Hz at this spee. To ensue this opeating conition at an unity isplacement facto, the pe-calculate efeence spee an iect cuent component i ae set to 34 a/s an A espectively (Moimoto, 994). The spee egulato povies the efeence fo the i cuent component. At t=.4 sec, the sign of the PMSM input toue is change to opeate it in geneating moe. The powe stats flowing fom the MTG system to gi as shown in Fig. (b).

15 98 Distibute Geneation Spee (a/sec) (a) Active powe (Watts) 4 x (b) Reactive powe (VA) (c) Fig.. Motoing an geneating opeation of PMSM (a) spee vaiation of PMSM (b) active powe vaiation at the gi sie of the MTG system (c) eactive powe vaiations at the gi sie of the MTG system. At t=.4 sec, the efeence spee an i cuent ae set to the pe-calculate values of 5849 a/sec an amps in oe to geneate powe of 4 kw. In oe to stuy the pefomance of the MTG system moel fo the change in powe, the efeence values of spee an i cuent component ae again change at t=.3 sec to geneate the ate powe of 8 kw. When PMSM geneates 8 kw, its line to line voltage an funamental RMS output cuent each the value of 48 V an A espectively. Fig. (c) shows that the eactive powe injecte to the gi uing the simulation peio is zeo. Input toue to PMSM (Nm) (a) Cuent of PMSM (A) (b)

16 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 99 DC-link votage (V) (c) i component (A) () Loa voltage (V) THD (%) (e) (f) Fig. 3. (a) Electomagnetic toue vaiations of the PMSM (b) Detaile vaiations of the stato cuent of PMSM (c) DC link voltage vaiation () i component of the injecte gi cuent (e) Line to line voltage at the loa teminals (f) %THD vaiation at the loa teminals. Figue 3 (a) shows the vaiation of electomagnetic toue of the PMSM. In this it can be obseve that, the change in the opeation moe of PMSM in simulation is instantaneous. But this may not be the same in pactical because of the inetia of the machine. Figue 3 (b) shows the natue of the stato cuent wavefom of the PMSM. It can be obseve fom Fig. 3 (c) that the DC link voltage is egulate to 76 V by the gi sie convete. Figues 3 () an (e) show the vaiation of i component of the injecte gi cuent an the voltage acoss the teminals of the loa. Thee is a small ecease in the voltage fo t<.4 sec, as shown in Fig. 3 (e). This is ue to the inceasing powe awn by the MTG system uing motoing moe opeation as shown in Fig. (b). In motoing moe both MTG system an loa aw powe fom the gi. The total hamonic istotion (THD) of the voltage is about.3% uing the entie simulation time as shown in Fig. 3 (f). 6. Response of the MTG moel fo vaious istubances in the gi Simulations ae caie out to stuy the pefomance of evelope the moel of the MTG system une vaious istubances oiginating fom the gi. Thee gi istubance conitions ae consiee fo stuy. They ae balance voltage ip, unbalance voltage an hamonic istotion in the gi voltage. In all these conitions the MTG system is opeate to elive 8 kw. Balance voltage ips: The simulation esults in Fig. 4 show the pefomance of the MTG system une balance gi voltage ip. At t =.4 to.5 sec ( cycle), % balance voltage

17 Distibute Geneation ip is intouce in the gi as seen fom Fig. 4 (a). The vaiation of the injecte eactive powe ue to the balance ip is egulate to zeo, by the gi sie convete contolle as shown in Fig. 4 (b). Figue(s) 4 (c), () an (e) show the vaiation in the active powe output of the MTG system an i, i component of the injecte cuent to the gi espectively. Voltage unbalance: At t=.4 sec the voltage unbalance in the gi is intouce by ceating shot cicuit fault between phase A an goun. Thus the phase A voltage is euce by % of its nominal value. In this case it is assume that unbalance exist till the en of the simulation time. The simulate phase voltage of the gi is shown in Fig. 5 (a). Gi voltage (V) Reactive powe (VA) x 4 (a) (b) Active powe (Watts) 3 i component (A) (c) () i component (A) (e) Fig. 4. Response of MTG system fo balance voltage ip in the gi. (a) balance voltage ip in line to line gi voltage. (b) eactive powe exchange with gi (c) the injecte active powe to the gi. () i component of the injecte cuent (e) i component of the injecte cuent to the gi.

18 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation At the point of voltage unbalance, eactive powe injecte to the gi suenly inceases an then is egulate to zeo as seen in Fig. 5 (b). The active powe injecte to the gi is not affecte by the unbalance in the gi voltage as obseve in Fig. 5 (c). Thee is no vaiation in the i an i components of the injecte gi cuent uing unbalance in the gi voltage as shown in Fig. 5 () an (e).duing this unbalance phase A cuent inceases to keep the active powe output of the MTG system to constant. 6 Gi voltage (V) Reactive powe (VA) x 4 (a) (b) Active powe (Watts) 3 i component (A) (c) () Cuent (amps) (e) Fig. 5. Response of MTG system fo voltage unbalances in the gi. (a)unbalance phase voltage of the gi (b) vaiation of injecte eactive powe to the gi (c) vaiations of injecte active powe to the gi () i component of the injecte cuent to the gi (e) i component of the injecte cuent to the gi. Pollute gi voltage: The simulation esults in Fig. 6 show the pefomance of the MTG system une hamonic pollute gi voltages. The vaious non linea loas connecte to the gi ae the main cause fo the hamonic pollution in the gi voltage. In oe to stuy

19 Distibute Geneation the pefomance of the moel une pollute gi voltage, along with the funamental component % of 5 th an 6% of 7 th hamonics ae injecte to the gi. The pollute gi voltages une this conition ae shown in Fig. 6 (a). As pe IEEE Stana (IEEE, 3), the THD at the point of common coupling to the gi shoul be kept below 5% but in this case it vaies fom % to 8% as shown in Fig. 6 (b) Fig. (s) 6 (c) an () show the vaiation of eactive powe exchange with the gi an injecte active powe espectively. The vaiation of the component of the injecte line cuents is shown in Fig. 6 (e) an (f) espectively. Gi voltage (V) (a) THD (%) (b) 4 x 4 Reactive powe (VA) 5-5 Active powe (Watts) (c) () i component (A) - Cuent (amps) (e) (f) Fig. 6. Response of MTG system fo pollute gi voltage (a) pollute phase voltage of the gi (b) vaiation of the THD in pecentage (c) vaiation of injecte eactive powe to the

20 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 3 gi () vaiations in injecte active powe to the gi (e) i component of the injecte cuent to the gi (f) i component of the injecte cuent to the gi. 6. Seamless Tansfe Scheme The scheme consists of passive islaning etection an e-closue metho. The pesente islaning etection metho uses the phase angle estimate by PLL to etect the islaning conition (Gaonka, 9). The e-closue scheme continuously monitos the phase angle an teminal voltage magnitue to etemine whethe istubance in the gi is ove o not. This is necessay in oe to synchonize the MTG system an to connect back to gi, without any own time. The PLL block use in invete contol is employe fo this scheme, hence no aitional hawae neee. The stuctue of the PLL use to etemine the phase angle eo euie by the popose scheme has been escibe in the section 5.4. Measuements Measuements is v<. pu an v >.88 pu yes is v g v gi min yes no Islaning exist no is min no is min yes Tansfe contol to islaning moe No islaning yes Tansfe contol to gi moe (a) (b) Fig. 7. (a) Islaning etection scheme (b) Re-closue scheme Once the voltages ae appoximately eual then algoithm compaes the value obtaine fom PLL with the set theshol limit. As long as these minimum euiements ae met (voltage an phase), thee ae no majo issues hineing the econnection of islane systems to the utility without e-enegizing an causing owntimes. Islaning Detection an Re-closue Metho: The algoithm evise fo the etection scheme is shown in Fig. 7 (Gaonka 9). The algoithm compaes the phase angle eo ( ) obtaine fom the PLL, with that of the theshol value. If excees the set theshol limit, then islaning is confime. At the same time contol of the invete is tansfee fom the cuent contol moe (gi connecte) to voltage contol moe (islaning moe). Duing the gi connecte moe is appoximately zeo. Once the gi fails, phase angle eo stats to incease. The value is obtaine by PLL as explaine in

21 4 Distibute Geneation section 5.4. This algoithm gives accuate esults even une matching loa conitions. The e-closue algoithm fo connecting MTG system to gi, when utility ecoves fom the istubance is shown in Fig. 7. The two main obstacles in implementing this type of eclosue ae matching voltage magnitue an phase angle between convete an the gi. If this is not one, lage tansient will take place which will amage the MTG system. The eclosue algoithm continuously monitos teminal voltage of the gi an MTG system. Both voltage magnitues ae compae. As pe IEEE st DG teminal voltage shoul be in between. an.88 pe unit of the nominal voltage. Both the voltage shoul be appoximately eual, to avoi lage tansients uing e-connection to gi. Eo in theta (a) (a) Active powe (Watts) 4 x (b) Reactive powe (VA) x (c) DC-link voltage (V) () Fig. 8. (a) Phase angle eo ( ) vaiation (b) active powe injecte to the gi by MTG system (c) eactive powe exchange with the gi () DC link voltage Utility Inteactive to Islaning Moe: The MTG system acts as a moto uing stating to launch the micotubine. Once micotubine eaches the spee of 34 a/sec at t=.4 sec, the PMSM is opeate as geneato by changing the iection of its input toue to negative. Duing geneating moe powe flows fom MTG system to gi. The phase angle eo between the gi voltage an convete voltage is appoximately zeo as shown in Fig. 8 (a). In gi connecte moe MTG system is opeate to inject 8 kw as shown in Fig. 8 (b). The othe paametes vaiations uing this moe of opeation ae given in Fig(s). 8 (c) an (). At t=.4 sec, utility connection to the DG is isconnecte by opening the cicuit beake.

22 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 5 This esults in fomation of a planne islaning situation compising local loa an MTG system. Opening of the cicuit beake can occu ue to the faults an othe gi istubances. When the cicuit beake is opene, the phase angle iffeence ( ) between gi voltage an the invete voltage obtaine fom PLL stats to incease. The islaning etection algoithm given in Fig. 7 continuously monitos the vaiation. Once cosses the theshol limit of.8 a then islaning is etecte an convete contol switches to islaning moe. The algoithms etect the islaning conition an tansfe the contol almost instantaneously. The vaiation of, active powe, eactive powe an i component of the injecte gi cuent ae shown espectively in Fig (s). 8 (a), (b), (c) an (). Duing this tansition ip in DC link voltage can be obseve fom Fig. 8 ().This is ue to the vaiation in active powe output of the MTG system. Duing the islaning moe MTG system supplies the powe euiement of the loa. Hence cuent supplie by the utility is zeo as obseve fom Fig. 9 (a) Gi cuent (A) (a) Gi voltage (V) (b) Loa voltage (V) MTG cuent (A) (c ) () Fig. 9. (a) Line cuent of the gi (b)phase voltage of the gi (c)etaile vaiation of loa phase voltage ()line cuent at the gi sie of MTG system Islaning To Utility Inteactive Moe: At t=.7 sec, the synchonization pocess stats to econnect the DG to utility. The e-closue algoithm compaes the gi voltage magnitue an phase angle with the MTG systems teminal voltage an phase angle. When the utility voltage magnitue appoximately matches with that of MTG system an is less than the theshol then DG is connecte to the utility. Duing this tansition vaiation of, active

23 6 Distibute Geneation powe, eactive powe, i component of the injecte gi cuent an DC link voltage ae shown espectively in Fig(s). 4.8 (a), (b), (c), () an (e). The vaiation of the line cuent of the gi, phase voltage an cuent vaiation of the MTG System teminals ae shown in Fig Conclusion The Distibute geneation base on micotubine technology is new an a fast gowing business. These DG systems ae uickly becoming an enegy management solution that saves money, esouces, an envionment in one compact an scalable package- be it stationay o mobile, emote o inteconnecte with the utility gi. In this thesis the MTG system moel suitable fo gi connecte an islaning opeation has been pesente.the etaile moeling of a single-shaft MTG system suitable fo gi connection an islaning opeation has been evelope in Simulink of the Matlab an is escibe in this chapte. The evelope moel allows the biiectional powe flow between gi an MTG system, hence nee of exta convete fo stating an shut own opeation of MTG system can be avoie. The multi-loop contol stuctue with ecoupling tems use fo gi an machine sie convetes has bette pefomance. The thee phase PLL stuctue escibe in this chapte uses only positive seuence component of the voltage. Hence gives accuate estimation of the phase angle even une gi istubance conitions. A seamless tansfe scheme fo MTG system opeation between gi connecte an intentional islaning moe has been popose in this chapte. The pesente automatic moe switching scheme helps in poviing continuous powe supply to the custome even uing outages of the utility an. is simple to implement without any aitional hawae. The moel shows goo pefomance in both gi connecte an islaning moe of opeations. Thus the evelope moel of MTG system can be use as a tool suitable fo stuying an fo pefoming accuate analysis of most electical phenomena that occu when a micotubine is connecte to the gi. As the issues ae new an ae the key fo sustainable futue powe supply, lot of eseach is euie to stuy thei impacts an exploit them to the full extent. 8. Refeences Al-Hinai, A., an Feliachi, A., (), Dynamic moel of micotubine use as a istibute geneato, Poceeings of the 34th South Easten Symposium on System Theoy,,pp. 9 3, 8 9 Mach, Huntsville, AL. Azmy, A. M., an Elich, I., (3), Dynamic simulation of fuel cells an micotubines integate with a multi-machine netwok, Poceeings of the IEEE Bologna Powe Tech Confeence, Vol., pp. 9, Bologna, Italy. Basali, S., Ceaolo, M., Pelacchi, P., an Poli, D., (), Contol techniues of ispese geneatos to impove the continuity of electicity supply, Poceeings of the IEEE PES Winte Meeting,Vol., pp. 7 3,. Capstone Micotubine Documentation, Available at : Chung, S.-K., (), Phase-locke loop fo gi-connecte thee-phase powe convesion systems, Poc. Inst. Elect. Eng., Vol. 47, No. 3, pp. 3 9,.

24 Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation 7 Fethi, O., Dessaint, L. A., an Al-Haa, K., (4), Moeling an simulation of the electic pat of a gi connecte mico tubine, Poceeings of the IEEE PES Geneal Meeting, Vol., pp. 9, 4. Gaonka, D. N., an Patel, R. N., (6), Moeling an simulation of micotubine base istibute geneation system, Poceeings of the IEEE Powe Inia Confeence, pp. 56 6, Apil 6. New Delhi, Inia, Gaonka, D. N., Pillai, G. N., an Patel, R. N., (8), Dynamic pefomance of micotubine geneation system connecte to gi, Jounal of Elect. Powe Compon. Syst., Vol. 36, No., pp. 3 47, 8. Gaonka, D. N., Pillai, G. N., an Patel, R. N., (9), Seamless tansfe of micotubine geneation system opeation between gi connecte an islaning moes, Jounal of Elect. Powe Compon. Syst., Vol. 37, No., pp , 9. Ghatemani, M. K., an Iavani, M. R., (4), A metho fo synchonization of powe electonic convetes in pollute an vaiable feuency envionment, IEEE Tans. Powe Syst., Vol. 9,No. 3, pp. 63 7, 4. Gua S. R., Wang C. an Nehi M. H., (4), Moeling of micotubine powe geneation systems, Electical Powe System an Components, vol. 34, no. 9, pp Hajagos, L. M., an Beube, G. R., (), Utility expeience with gas tubine testing an moelling, Poc. IEEE PES Winte Mtg., Vol., pp ,. IEEE, (3), IEEE stana fo inteconnecting istibute esouces with electic powe systems, IEEE St , 3. Illina, M., an Venkatamanan, G. (), Contol of istibute geneation systems to mitigate loa an line imbalances, Poceeings of the IEEE Electonics an Specialists Confeence, Vol. 4, pp. 3,. Moimoto, S., Sanaa,M., an Takea,Y., (994), Wie spee opeation of inteio pemanent magnet synchonousmotos with high pefomance cuent egulato, IEEE Tans. Inl. Appl., Vol. 3, pp. 9 96, 994. Nikkhajoei, H., an Iavani, R., (5), A matix convete base micotubine istibute geneation system, IEEE Tans. Powe Delivey, Vol., No. 3, pp. 8 9, 5. Pillai, P., an Kishnan, R., ( 989), Moeling, simulation, an analysis of pemanent-magnet moto ives, Pat I: The pemanent-magnet synchonous moto ive, IEEE Tans. Inl. Appl.,Vol. 5, No., pp , 989. Pena, R. Caenas, R. Blasco R., G. Ashe G. an J. Clae J., (), A cage inuction geneato using back-to-back PWM convetes fo vaiable spee gi connecte win enegy system, in Poc. IECON Conf., vol.,, pp ,. Rowen, W. I., (983), Simplifie mathematical epesentations of heavy uty gas tubines, ASME Tans. J. Eng. Powe, Vol. 5, No. 4, pp , 983. Scott, W. G., (998), Micotubine geneatos fo istibution systems, IEEE Inusty Appl. Mag.,Vol. 4, No. 3, pp. 57 6,998. Teooescu, R., an Blaabjeg, F., (4), Flexible contol of small win tubines with gi failue etection opeating in stan-alone an gi-connecte moe, IEEE Tans. Powe Electonics.,Vol. 9, No. 5, pp , 4. Tiumala, R., Mohan, N., an Henze, C.,, Seamless tansfe of gi-connecte PWM invetes between utility-inteactive an stan-alone moes, Poc. 7th Ann. IEEE Appl. Powe Electon. Conf. Exposit., Vol., pp. 8 86,.

25 8 Distibute Geneation Villeneuve, P. L., 4, Concen geneate by islaning, IEEE Powe Enegy Mag., Vol., No. 3, pp , 4.

26 Distibute Geneation Eite by D N Gaonka ISBN Ha cove, 46 pages Publishe InTech Publishe online, Febuay, Publishe in pint eition Febuay, In the ecent yeas the electical powe utilities have unegone api estuctuing pocess wolwie. Inee, with eegulation, avancement in technologies an concen about the envionmental impacts, competition is paticulaly fostee in the geneation sie, thus allowing incease inteconnection of geneating units to the utility netwoks. These geneating souces ae calle istibute geneatos (DG) an efine as the plant which is iectly connecte to istibution netwok an is not centally planne an ispatche. These ae also calle embee o ispese geneation units. The ating of the DG systems can vay between few kw to as high as MW. Vaious new types of istibute geneato systems, such as micotubines an fuel cells in aition to the moe taitional sola an win powe ae ceating significant new oppotunities fo the integation of ivese DG systems to the utility. Inteconnection of these geneatos will offe a numbe of benefits such as impove eliability, powe uality, efficiency, alleviation of system constaints along with the envionmental benefits. Unlike centalize powe plants, the DG units ae iectly connecte to the istibution system; most often at the custome en. The existing istibution netwoks ae esigne an opeate in aial configuation with uniiectional powe flow fom centalize geneating station to customes. The incease in inteconnection of DG to utility netwoks can lea to evese powe flow violating funamental assumption in thei esign. This ceates complexity in opeation an contol of existing istibution netwoks an offes many technical challenges fo successful intouction of DG systems. Some of the technical issues ae islaning of DG, voltage egulation, potection an stability of the netwok. Some of the solutions to these poblems inclue esigning stana inteface contol fo iniviual DG systems by taking cae of thei ivese chaacteistics, fining new ways to/o install an contol these DG systems an fining new esign fo istibution system. DG has much potential to impove istibution system pefomance. The use of DG stongly contibutes to a clean, eliable an cost effective enegy fo futue. This book eals with seveal aspects of the DG systems such as benefits, issues, technology inteconnecte opeation, pefomance stuies, planning an esign. Seveal authos have contibute to this book aiming to benefit stuents, eseaches, acaemics, policy makes an pofessionals. We ae inebte to all the people who eithe iectly o iniectly contibute towas the publication of this book. How to efeence In oe to coectly efeence this scholaly wok, feel fee to copy an paste the following: Dattataya N. Gaonka (). Pefomance Of Micotubine Geneation System in Gi Connecte an Islaning Moes of Opeation, Distibute Geneation, D N Gaonka (E.), ISBN: , InTech, Available fom:

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