ADVANCED TECHNIQUE FOR SOFT SYNCHRONIZER IN CHP COGENERATION

Transcription

1 ADVANCED TECHNIQUE FOR SOFT SYNCHRONIZER IN CHP COGENERATION Abhijit S. Pane 1 an Nishij G. Kulkarni 2 1 PG Stuent, M.B.E. Society s College of, Engineering, Ambajogai (M.S), Inia 2 PG Department, M.B.E. Society s College of Engineering, Ambajogai (M.S), Inia ABSTRACT In this work, a controller has been use to synchronize between two parallel operations. Two AC systems, an electric power system an synchronous generator have been use in parallel operation. Due to many rawbacks in traitional control, a proper synchronization is not achieve. Here in a new iea an technology of soft synchronizer which is evise an lea to proper synchronization. To see the effectiveness of the propose controller along with implementing new iea, a simulation stuy on MATLAB has been shown for effectiveness. The stuy showe perfect phase angle match for two parallel AC systems. KEYWORDS: Combine heat an power (CHP), cogeneration, signal conitioning, micro gris, simulation, synchronization, synchronizer, MATLAB. I. INTRODUCTION The avance features of the future power system that will be mae up electrical an thermal loas as well as of large numbers of on-site istribute energy resources (DER) is shown by consortium for electrical reliability technology solutions (CERTS) micro gri concept [1]. As micro gri provies number of benefit is ivie into two major groups as given one is the power quality an reliability factor an the other one is an economical an environmental factor [2]. Now ays the fact is that the inverter-base generation is the general tenency for the renewable an new DER, an alternator base combine heat an power (CHP) cogeneration provies high energy efficiency as well as reliable performance compare to the other intermittent renewable energy resources. Hence, combine heat an power (CHP) cogeneration is concern as a core an the key requirement of the micro gri if it is applicable [3], [4]. As CHP provie high energy efficiency an for given input fuel it prouce 80% output by utilizing both electricity an waste heat it s getting lot of attention. One of the avantages in using a high efficient system is that it become less the total amount of carbon ioxie (CO 2) emission. It may increase the payment rate of the electricity by ecrease the facility s peak emans. As a result of this we ha evelope a new, small CHP cogeneration system. The figure 1 below shows a block iagram of the CHP cogeneration system which inclues the major controllers. The system consists of a synchronous generator an a gas engine that is controlle by an engine control unit (ECU) an a igital automatic voltage regulator (DAVR), respectively. An for the collection of waste heat, a heat recovery unit was installe. The integrate control unit (ICU) is one of main controller of the CHP cogeneration system. The soft synchronizer plays an important role in the inauguration of the electric power system (EPS) parallel operation as one of the ICU s auxiliary functions Vol. 7, Issue 6, pp

2 EPS CB Heat Recovery Engine Generator CB Loa ICM Exciter ECU DAVR Generator control Measurement Soft Synchronize Protective Logic Loa Sharing Alarm Event Log Heat Exch. Supervisory Sequence Communication Remote H.M.I Integrate unit Figure 1: Block iagram of Combine Heat an Power (CHP) cogeneration system Three conitions are referre to as the synchronizing criteria. Those are phase-angle, slip frequency, an the voltage ifference has to be match as close as possible for paralleling ac generators. When those parameters are matche, two iniviual systems may begin a parallel operation by closing the breaker contact. In case of large scale generator that has less number of synchronization events per year [5], but in case of small CHP generator has frequent start/ stop/ synchronization events. Accoring to a survey report, there are major four evices which mainly use for synchronization presently. These evices liste as voltage relays, Sync-check relays, automatic synchronizer an the synchronizing relays [5]. The belief hane own to posterity for measuring the synchronizing conition is use the zero crossing signals of two voltages. Due to high accuracy an simple structure Zero crossing metho is wiely use. The major isavantage is that, particularly on long measurement perio an is weak against harmonics an noises [6]. For getting better performance, strenuous exertions have been mae such as Smart iscrete Fourier transforms (DFT) or the moifie zero-crossing. DFT-base frequency measurement has an avantage against harmonics. Despite this the calculation has a elay of N DFT samples. The phasorbase metho use some microprocessor-base synchronizers an sync-check relays, [7]. So as to get the protection of slip frequency, most of the evices simply use a metho of elaying a breaker. In this paper, a synchronizing technique is introuce. It contains novel approaches regaring the calculation of signals for the synchronizing criteria, signal conitioner, an zero phase-angle ifference estimation. In this paper, a new synchronizing technique is introuce. It contains novel approaches regaring the calculation of signals for the synchronizing criteria, signal conitioner, an zero phase-angle ifference estimation. In Section II, basic theory an avance synchronizing 1761 Vol. 7, Issue 6, pp

3 technique are explaine. In Sections III an IV, Simulation an result of a comparison between traitional an propose technique is evaluate by simulation. II. ADVANCED SYNCHRONIZING TECHNIQUE As we nee to measure three major signals to begin parallel operation. In this part, we propose a simple but efficient solution to check the synchronizing criteria. 1. Ientifying Signals for Synchronizing Using frame transformation in symmetric three-phase variables (f a, f b, f c ) can be transforme into a stationary irect axis f α, an a quaratic axis is f β as 1 1 [ f α f a 1 f β]= T 1. [ f b ], T 1 = 2 [ f c 0 3 ] (1) The relation in between stationary an rotating axis can be given as [ f f q]= T 2(θ r ).[ f α f β], T 2(θ r ) = [ cosθ r sinθ r ] (2) sinθ r cosθ r Despite of this, if it is transforme into the rotating axis at a spee of ω r an if we assume ω r = ω then they look like being stan still on the rotating axis. This transformation can be expresse by the following equation: [ f f q] = T(θ r).[ f b ] (3) f c The transformation matrix is T (θ r ) =T 2 (θ r ) T(θ r ) = 2 [ cosθ r cos (θ r + 2π ) cos (θ 3 r 2π ) 3 3 sinθ r sin (θ r + 2π ) sin (θ 3 r 2π (4) )] 3 The angle between rotating f an stationary f α is efine as the following equation: t θ r = ω r (T)t + θ r (0) (5) 0 Relating to the vector control, it is orinary to synchronize ω r to ω in orer to ecouple the variables as the torque an the magnetization component. An we synchronize them to the phase voltages by using the phase-locke loop (PLL). The transformation above is known as Park s transformation an it commonly use in a three-phase electric machine. The magnitue an the angle of the original signal can be mark out by using the following equations. f a Mag = f q 2 + f 2 (6) Angle = tan 1 f q f. (7) The three-phase voltages of the Electrical Power System are given as V u, V v, V w an for the synchronous generator is V r, V s, V t by taking the reference frame transformation we, q V (UVW) q (V (UVW) ) an (V (RST), V (RST) ) can be obtaine. The voltage ifference is given by following equation. V iff = V UVW 2 q + VUVW 2 V 2 RST + V RST q 2 (8) The phase-angle ifference of θ s is measure as θ s = ( π 4 θ 1) ( π 4 θ 2) = tan 1 V RST q V RST An the frequency between two voltages can be calculate as follows: F slip = ω s = 1 θ s 2π 2π t tan 1 V q UVW V (9) UVW (10) 1762 Vol. 7, Issue 6, pp

4 2. Signal Conitioner Signal Conition is an easy algorithm in this angle is calculate at each sampling Perio. Disavantage of this feature is oscillation occurs in original signal. The excessive unbalance in signal is protecte by a phase unbalance protector that prevents the generator breaker operation. Due to small amount of unbalance in source signal occurre, synchronizer regulate properly. By aing signal conitioner in the signal conitioning block we can calculate the phase of a positive-sequence phasor an the magnitue an we mae virtual three phase symmetric signals with the same magnitue of the original phasor. As a result, we will get a better phase-angle measurement from the original signals. The positive-sequence voltage calculate by using following equation V 1 = 1 3 (V a + av b + a 2 V c ) (11) We can create virtual three-phase signals by using the positive-sequence voltage an the phase operator that are symmetrical. [V a V b V c ] T = [1 a 2 a] T. V 1 (12) Those virtual signals were mae by a positive-sequence voltage that has averaging effects on the original signals in magnitue an phase aspects. 3. Calculating Phase-Angle Difference Now a ay many of the current auto synchronizers make a ecision of circuit breaker (CB) closing by the place of time of a phase-angle ifference with preetermine limits closing outsie of the limit that will bring collision between two voltages [8]. The usual well time for the sync check relay is ecie by the calculation from the esire slip frequency an the phase-angle ifference limit. Therefore, the actual break closing may occur within the limit, but not exactly on the zero point of the phase-angle ifference. We can calculate an estimate phase-angle ifference right on the moment when the breaker will close as θ θ = θ k + T k θ k 1 b (13) Δt Where, θ Estimate phase-angle ifference θ k, θ k 1 Phase-angle ifference of k th an (k-1) th step T b Breaker closing time elay Δt Sampling time By performing frequent estimation an by using the very narrow phase-angle ifference limits(±1 0 ), we ha obtaine a zero phase-angle ifference for the actual breaker closing. The traitional measurement using the zero-crossing metho can measure once or twice in a voltage cycle, but the new metho base on reference frame transformation has better an faster performance because of its immeiate measurement feature. III. SIMULATION The effectiveness of the new synchronization can be verifie as shown in the block representation of MATLAB Simulink of Diesel engine generator connecte to electrical power system by the synchronizer. For the simulation of electrical power systems which contains equipments such as three-phase machines, trans-formers, R-L-C loas, transmission lines, three-phase breakers, in MATLAB, SimPower Systems is one of the esigning tool that allows users to buil moels rapily an easily [9] Vol. 7, Issue 6, pp

5 Figure 2. Simulation moel of the iesel engine generator connecte to the electric power system by the synchronizer The above figure shows representation of Diesel engine generator connecte to electrical power system by the synchronizer. The synchronization is an essential process while an iniviual ac generator has to be operate with another ac power system, for the parallel operation. The figure above shows an entire block iagram. At start uring initially a loa is connecte to the Electrical Power System through a transformer (3-ϕ Source) an a three-phase breaker. At the same time, when a iesel engine generator is start to operates in an isolate moe. Synchronizer logic is tack place to controls the spee an the voltage of the iesel engine to match the synchronizing criteria. Once all the synchronizing criteria satisfie, the synchronizer generates a breaker closing signal an the breaker is close an system is operate in synchronous moe, in this way the synchronization is one. IV. RESULTS The result shown in below figure 3 an figure 4 gives the clear ifference between the traitional synchronizer an the propose soft synchronizer. We neee to calculate the well time setting in case of emonstration. By Enabling the slip frequency of 0.1 Hz an phase-angle ifference limit of the synchronizer an the well time was calculate. We may assume that the relay operation time as 1/2 cycle (0.058 sec) an a breaker closing time an as three cycles. In case of max slip frequency, the breaker will actually close at a phase-angle + ifference of [10]. A traitional synchronizer with a well time setting shows in below simulation result the anglesθ 1, θ 2 are phase angles of the electrical power system an the iesel generator. In case of making the slip frequency as 0.1 Hz, we ha been set the frequency of the electrical power system an the iesel generator. As expecte that the above the actual breaker closing was complete when the phase-angle ifference is about(θ s ). Due to a consequence of this phaseangle mismatch large oscillations in voltages, spee, power an the phase currents were generate. As result shown in below figure 4 for the propose soft synchronizer the breaker was exactly close at the zero point θ s ue to this an entire signals showe no oscillation. While comparing these two result figures, the oscillation of spee an mechanical power are cause only by the electrical phaseangle ifference. Because the voltage magnitue an the frequency slip are ientical for both simulation cases Vol. 7, Issue 6, pp

6 Figure 3. Case of the traitional synchronize Figure 4. Case of the soft synchronize V. CONCLUSION AND FUTURE WORK This paper provies the synchronization in soft way technique. By using this propose technique we get a simple an clear measurement of the results. The results enable the smooth an soft connection between the electric power system an the synchronous generator. By using a reference frame transformation-base synchronizing criteria measurement, the signal conitioner an the phase-angle ifference estimation, the perfect match between the electrical power system an the synchronous generator through the simulation an the valiation of the propose technique was performe. This technique (soft Synchronization) gives the noticeable comparative results with the traitional techniques. As mention in entire paper with the help of soft synchronization technique we can perform parallel operations in automation an other electrical systems. But this technique is limite to a single pair of AC systems. In future it might be possible to use this soft synchronization technique for two or more than two pair of AC system, which will be helpful in high level an large scale synchronizers. REFERENCES [1] R. H. Lasseter, MicroGris, Proc. IEEE Power Eng. Soc. Winter Meeting. 1 (2002), [2] C. Marnay an G. Venkataramanan, Optimal technology selection an operation of commercialbuiling microgris, IEEE Trans. Power Syst., 23(3) (2008), [3] C. Xiarnay, H. Asano, S. Papathanassiou, an G. Strbac, Policy- making for microgris, IEEE Power an Energy Mag., 6(3) (2008), [4] K. Yeager, Striving for power perfection, IEEE Power Energy Mag., 6(6) (2008), [5] W. M. Strang, C. J. Mozina, B. Beckwith, T. R. Beckwith, S. Chhak, E. C. Fennell, E. W. Kalkstein, K. C. Kozminski, A. C. Pierce, P. W. Powell, D. W. Smaha, J. T. Uchiyama, S. M. Usman, an W. P. Wauby, Generator synchronizing, inustry survey results, IEEE Trans. Power Del., 11(1) (1996), Vol. 7, Issue 6, pp

7 [6] T. Sezi, A new metho for measuring power system frequency, Proc. IEEE Transmission an Distribution Conf., 1(1999), [7] K. Koellner, C. Anerson, an R. Moxley, Generator black start vali- ation using synchronize phasor measurement, Proc. IEEE Power En. Soc. Power System Conf. Expo., (2006), [8] Woowar, Installation & Operation Manual for SPM-A Synchro- nizer. [Online]. Available: loa.cfm?link=/pdf/ic/82384.pdf. [9] MATLAB, SimPowerSystems reference. ver. 4.5 (R2007b). [Online]. Available: [10] N. T. Stringer, Voltage consierations uring generator synchronizing, IEEE Trans. In. Appl., 35(3)(1999), [11] Antonio D. Reis, Jose F. Rocha, Atilio S. Gameiro an Jose P. Carvalho,Carrier Phase Lock Loop an Bit Phase Lock Loop, Proc. IX Symposium on Enabling Optical Network an Sensors (SEONs) pp. CD - Eite, Aveiro-PT 1-1 (2011). AUTHORS BIOGRAPHY Abhijit Sanjay Pane Receive his B.E. in Electrical (Electronics & Power) in 2011 from P.E.S College of Engineering, Aurangaba affiliate to Dr.B.A.M. University, Aurangaba. Currently he is pursuing his M.E Electrical ( Systems) from M.B.E.S College of Engineering, Ambajogai. Nishij Ganpatrao Kulkarni He is currently pursuing his Ph.D. in Electrical Engineering from Government College of Engineering, Amravati affiliate Sant Gagebaba University, Amravati. He has worke in inustry for 03 years an has a teaching experience of 18 years. e Receive his B.E. in Electrical (Electronics & Power) in 1993 from Government College of Engineering, Aurangaba afflilate to Marathwaa University, Auranagaba an he receive his M.E in Electrical (Power Systems) in 2007 from PVG s College of Engineering, Pune (Pune University). His areas of interest are Electrical Machines, Power Systems, Renewable Energy Sources Vol. 7, Issue 6, pp