Dynamic Simulation of the Generalized Unified Power Flow Controller in Multi-Machine Power Systems

Transcription

1 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 75 Dynamic Simulation of the Generalized Unified Power Flow Controller in Multi-Machine Power Systems Rakhmad Syafutra Lubis, Sasongko Pramono Hadi and Tumiran Abstract The latest generation of flexible AC transmission system (FACTS) devices, the convertible static compensator (CSC), is the progress of several innovative operating concepts in the historic development and application of FACTS. One of the concepts modelling is the generalized unified power flow controller (GUPFC) have been done, which can control bus voltage and power flows of more than one line or according to even a sub-network. In this paper it derived to pile up a novel nonlinear dynamic simulation of the GUPFC consisting of one shunt converter and two series converters based on voltage source converter (VSCs) and DC link capacitor installed in a substation in a multi-machine power system. The linearised Phillips-Heffron model of the system is introduced with Hammons and Winning model is derived to study oscillation stability. The dynamic simulation of the GUPFC is arranged with a simulation program in Matlab programming language, where the two case study of the four machine twelve bus and three machines fifty seven bus power systems was simulated and presented to investigate the impact of the GUPFC control function on power system oscillation damping and to proof the simulation program reliability. It is found that the basic control function of the GUPFC, the voltage control of the DC link capacitor, interacts negatively with the power system, thus damaging system oscillation stability. In order to counteract the negative interaction measuring is done by either adjusting or equipping the GUPFC with a power oscillation damping (POD), without installing the power system stabilizer (PSS) on each machines are tested. The results demonstrate that a satisfactory damping of power system oscillations can be achieved. It is seen that the GUPFC dynamic simulation can be applied and better than the unified power flow controller (UPFC) for a large scale system as the multi-line control. Index Terms FACTS, GUPFC, non-linear dynamic simulation program, linearised Phillips-Heffron model, Hammons and Winning model. I. INTRODUCTION The FACTS devices have been done for many modelling in dynamic or static model, such as static var compensator (SVC), thyristor controlled series capacitor (TCSC), thyristor Manuscript received in May 9,, revised in June 4,. Rakhmad Syafutra Lubis is with the Department of Electrical Engineering, Faculty of Engineering, Universitas Syiah Kuala, Banda Aceh. Indonesia. (phone: ; rsyafutralubis@yahoo.com). Sasongko Pramono Hadi is with the Department of Electrical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta. Indonesia. (phone: ; sasongko@te.ugm.ac.id). Tumiran is with the Department of Electrical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta. Indonesia. (phone: ; Fax: ; tumiran@te.ugm.ac.id). controlled phase shifting transformer (TCPST), static synchronous series compensator (SSSC), Static synchronous compensator (STATCOM), interline power flow controller, (IPFC), UPFC and GUPFC. The UPFC and GUPFC is a multi-functional FACTS controller with the primary function of power flow control plus possible secondary duties of voltage support, transient stability improvement and oscillation damping etc. A good multifunctional power flow management devices, an innovative approach of FACTS controllers was proposed namely convertible static compensator or CSC applied in the New York transmission system. There are several possibilities or operating configurations by combining two or more converter block with flexibility such as shunt compensation alone (STATCOM), series compensation alone (SSSC), decoupled shunt and series compensation (STATCOM and SSSC), coupled shunt and series compensation (UPFC), coupled series compensation on two or more line (IPFC), coupled shunt and series compensation on more than one line (Multi-Line or Generalized UPFC) []. The first time innovation for each FACTS devices have been done such as UPFC [, 3, 4], SSSC [5] and there are two operating configurations namely the IPFC [6] and GUPFC [], which are significantly extended to control power flows of multilines or a sub-network, which the originality is the control power flows of single line or UPFC. The installation of the FACTS [7] especially the UPFC in power systems has been coming under intensive investigation into its modelling and various control functions, including damping control for single-machine infinite-bus power system and multi-machine in [4] and [8, 9]. Work has been done to model the UPFC [] and the GUPFC [] into multi-machine power systems in a steady-state mode of operation for studying power flow control. A fundamental frequency model of the GUPFC consisting of one shunt converter and two series converters for the EMTP study was proposed quite in []. While modelling the GUPFC in power flow and optimal power flow (OPF) analysis was proposed, among them [] is modelling the GUPFC in non-linear interior-point OPF, where the mathematic models of power injection based on [], while in [3] is only modelling the GUPFC to incorporate in load flow studies. Modelling the GUPFC in the nonlinear dynamic in a transmission line, consist of two parallel VSC and one series VSC in Figs. 6 [4]. In contrast to the practical applications of the GUPFC in power systems, very few publications such as the mathematical modelling in IJECS-IJENS June IJENS

2 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 76 dynamic or static analysis and nonlinear dynamic simulation in multi-machines power system Furthermore a mathematical model of the GUPFC in this paper uses the base that is formulated in [8, 9] and also considered with [4]. According to [5] by Ugalde Loo et. al., that owing to the physical insight afforded by the Phillips-Heffron representation of the synchronous generator (initially introduced by Phillips and Heffron, 95, and then explored further by DeMello and Concordia, 969, and Saidy and Hughes, 994), the model has been widely used and applied to Single Machine-Infinite Bus (SMIB) systems. Extensions have been made to include Power System Stabilizers (PSS) also in [7], sub-transient effects of damper windings and electronically controlled compensation (see, for instance, the work of Aree and Acha, 999). A major asset of the Phillips- Heffron block diagram model is that it lends itself to the use of classical and robust control techniques, as pointed out by Rogers (). However, a drawback of the block diagram representation is that the visual simplicity of this approach is lost when applied to cases of even two machines. On the other hand, eigen analysis remains as the industry s preferred approach for assessing small signal stability owing to its large-scale applicability as discussed by Kundur et al. (99); although it may be argued that the great physical insight afforded by the Phillips-Heffron model is not apparent in the eigen analysis-based solutions. Therefore in this paper the linearised Phillips-Heffron model of the GUPFC system is introduced with the modelling method in [5] where based on the work of Hammons and Winning (97). Based on that case, this paper propose a configuration, as the unified control for the whole controlling, that they are GUPFC and the POD with Hammons and Winning model. A non-linear dynamic simulation program is arranged to apply the non-linear dynamic model of the GUPFC installed in a multi-machine power system in programming language. The two case study of the four machine twelve bus [6] and IEEE three machines fifty seven bus power systems with a GUPFC installed in a substation was simulated and presented to investigate the impact of various GUPFC control function, as the main controller, and POD, as auxiliary controller, on power system oscillation damping and to proof the simulation program reliability. It is found that the basic control function within the GUPFC, the voltage control of the DC link capacitor, interacts negatively with the power system, thus damaging system oscillation stability. Measures to counteract the negative interaction by either adjusting or equipping the GUPFC with a damping controller (POD) are tested. The results demonstrate that a satisfactory damping of power system oscillations or dynamic stability can be achieved. The problem about computation of introducing a damping controller parameters into the GUPFC is not presented in this paper, where only use the phase compensation method, while use the three criteria to select the operating condition of the power system to ensure the robust design of the GUPFC damping controller and the input control signal to be superimposed by the GUPFC damping function to achieve the maximum efficiency of the damping controller, as presented in [8]. II. MODEL FOR POWER SYSTEM A. The Model of the Multi-Machine Power Systems The implementation for the power system is used the linearised model has been successfully used for the analysis of power system oscillation stability and design of power system damping controllers, such as PSS and FACTS-based stabilisers [7-9] and [7, 8]. The linearised model of the n- machine power system installed with the GUPFC has been done in the other paper around an operating point of the power system. It is a generic linearised model of the power system. However for the study of power system oscillation stability, a simplified model of generators is used by neglecting the internal resistance and sub-transient process of the generator [9]. The linearising equations of the GUPFC system are as follows = = = = ω = + () = = = ; = (3) where = Substituting equation () into (3) can be found = = = (4) By substituting equation (4) into equation () is found = () IJECS-IJENS June IJENS

3 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: electromec hanical K ( Ms+ D) Kp K oscillation ω loop Kq + f Kv s FACTS K 4 K 5 The equation of DC component is = Substituting equation (6) into equation (5) is found = (5) (6) ( K ) 3 + st D K ( ) A + st A + K 6 Fig.. Linearised Phillips-Heffron model of n-machine power system with the GUPFC installed. + Which equation (7) can be shown by Fig. where = = ; = (7) ; = Where could be,, and,,, the linearisation of the input signals of the GUPFC, which the GUPFC is the category of unified model. The GUPFC must be equipped with this basic control function. By use the active power input to the GUPFC from the whole VSCs can be obtained as follows = + = cos = + = cos sin sin IJECS-IJENS June IJENS

4 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 78 = + = cos sin (8) The GUPFC is treated as an external controller installed in the network and its effect is included in the network currentvoltage equation. From equation (7) the dynamic of the GUPFC, mainly the DC capacitor, is included by expressing line current explicitly. This is the final form of the linearised model. If equation (7) is added with POD controller to control the GUPFC and the system GUPFC controller in the Phillips- Heffron model is introduced with,, as the modelling method in [5] where based on the work of Hammons and Winning (97), where it is model (5th order, two-axes) in the s-domain characterize, with the first substitute into the equation (4), as follows = = = = (9) where The with permanent sign (positive), as a proposes in this paper. = + = + = + = + Assumed value of is = ), as a proposes in this paper. The following is the whole system matrix, where the equation (7) is modified into = + K + III. APPLICATIONS CASE STUDY FOR EXAMPLE OF THE SIMULATION PROGRAM () A. Data The parameters of four-machine twelve-bus power system of Fig., case, are obtained from [6], figs 83 example.6, which is modified, as follows: IJECS-IJENS June IJENS

5 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 79 L G T 3 T C 3 C L T 4 ω m, E mb mc δ, E δ, B δc, G G 4 Fig.. A GUPFC to be installed on four machine power system. The system consists of two similar areas connected by a weak tie. Each area consists of two coupled units, each having a rating of 9 MVA and kv. The generator parameters in pu on the rated MVA and kv base are as follows: =.8 =.7 =. =.3 =.55 =.5 =.5 =.5 = 8. =.4 =.3 =.5 =.5 = 9.6 =.9 = 6.5 (for G and G ) = 6.75 (for G 3 and G 4 ) = Each step up transformer has an impedance +j.5 pu on 9 MVA and /3 kv base, and has an off-nominal ratio of.. The parameters of the lines in pu on MVA, 3 kv base are: =. =. =.75 The system is operating with area exporting 4 MW to area, and the generating units a loaded as follows: ; = 7 = 85 =.3. ; = 7 = 35 =..5 ; = 79 = 76 = ; = 7 = =. 7. The Loads and reactive power supplied Q C by the shunt capacitor at buses and are as follows: Bus : = 967 = = Bus : = 767 = = 35 Thyristor exciter with a high transient gain: =. =. The parameters of IEEE three-machine fifty-seven-bus power system, case, are also obtained from [6], figs 83 example.6, modified, with modifying the data of generator and then incorporated into the data IEEE 3-machine 57-bus as follows: T G Each generator having a rating of 9 MVA and kv. The generator parameters in pu on the rated MVA and kv base are as follows: =.8 =.7 =. =.3 =.55 =.5 =.5 =.5 = 8. =.4 =.3 =.5 =.5 = 9.6 =.9 = 6.5 (for G and G ) = 6.75 (for G 3 ) = The system is operating with the generating units a loaded as follows: ; =,55 pu =,7 pu =,4. pu ; =,3 pu =,88 pu =,,797 pu ; =,4 pu =, pu =, pu Thyristor exciter with a high transient gain: =. =. B. Results The results of computing the oscillation modes of the power system is given in figures 3 until 7 and in table for conventional system and with GUPFC controller from the system linearised model in investigating the impact of the GUPFC control on system oscillation stability (a) (b) IJECS-IJENS June IJENS

6 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 8 Torque Angle Deviation, degree Torque Angle Deviation, degree Torque Angle Deviation, degree Fig. 3 The first system, (a) Conventional, (b) (c) With GUPFC (a) (b) (c) Fig. 4 The first system, (a) Conventional, (b) and (c) With GUPFC. 6 x (a) 6 x x (b) x (c) (d) Fig. 5 The first system, (a) (b) Conventional, (c) (d) With GUPFC IJECS-IJENS June IJENS

7 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 8 Torque Angle Deviation,degree x (a) (b) (c) Fig. 6 The Second system (IEEE 57-bus) without GUPFC (a) Torque Angle Deviation, degree x -3 (b) x -3 (c) (d) (e) IJECS-IJENS June IJENS

8 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 8 Voltage Deviation, Efd, pu Voltage Deviation, Efd, pu Torque Angle Deviation, degree Voltage Deviation, Vdc, pu (f) (g) (h) (i) Voltage Deviation, Vdc, pu (j) Fig. 7 The Second system (IEEE 57-bus) with GUPFC. TABLE I STATE MATRIX EIGENVALUE OF THE SYSTEM Power System Case 4-Machines -bus (Kundur Modified ) Case IEEE 3-machine 57-bus C. Discussion Without GUPFC With PSS ±6.98i -.8 ± 5.5i ±54.633i.4 ±3.83i With GUPFC Without POD and PSS -.93 ±6.94i -.84 ±5.39i ±5.5673i.8 ±3.858i With GUPFC and POD Without PSS ±.7i ±.377i ±84.699i -.49 ±.56i The location of the GUPFC in IEEE 57-bus system in the simulation programming found from the sensitivity of system loading factor technique and N contingency criterion which proposed in another paper (in press). The location is at a substation where the first line is between bus-9 and bus and the second line is between bus-9 and bus. Table, is state matrix eigenvalue describing the roots of the characteristic equation of the system, four-machine twelve-bus (case ) and three-machine fifty-seven-bus (case ) power systems test case. For the system without GUPFC with PSS indicate unstable condition where necessary adjust (tuning) parameters of PSS. For the system with GUPFC without POD and PSS indicate unstable condition that is IJECS-IJENS June IJENS

9 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 83 consequence of situation where the basic control function of the GUPFC, the voltage control of the DC link capacitor, interacts negatively with the power system, thus damaging system oscillation stability, therefore necessary equipping the GUPFC with POD. For the system with GUPFC and POD without PSS indicate stable condition that is results of control function of the GUPFC and POD with the selection of the input control signal to be superimposed by damping controller such as,,,,,. That explained in [8]. Fig. 3-7 presents the non-linear simulation based on the system dynamic model. The oscillation is triggered by a threephase short circuit occurring on the transmission line between nodes 8 and 9 (in case ), and between nodes and 5 (in case ) in the example power system test case at. second of the simulation and cleared after millisecond. It obviously confirms the results that indicate satisfactory of the unified control scheme between the GUPFC and POD damping controller in power system oscillation damping. Hence the PSS controller is chosen to be + + = where its parameters are set to be = 5, =,, =,, =,9, =, Another measure is to introduce a damping controller into the GUPFC, hence is obtained as follows (wash-out block): =, ,45 + 3,656 +, + 4,5 and the feedback signal of the damping controller,, is taken to be the active power delivered along the transmission line from node 8 to 9 for case and node and 5 for case. In Fig. 3, show the voltage deviation which figure (b) and (c), with GUPFC and POD, are going to a stable condition, steady-state, at before s, however figure (a), without GUPFC and POD, is going to unstable condition as we can be seen in Fig. 5, figure (b) also for -bus system, the rotor speed deviation is going to unstable condition before 4 s where the system run until 5 s. These indicate capability of the GUPFC control system. While the system only installed with the PSS could not stable. Fig. 4.a, the torque angle deviation, and Fig. 5.a, the rotor speed deviation, has distortion. Finally, whole characteristic of the -bus system completely showed in Fig. 3. Fig. 4 and Fig. 5 where the whole figures show the same characteristic as explained above. Fig. 6 show the characteristic of the IEEE 57-bus power system without GUPFC control system showed unstable condition before 5 s. Fig. 6.a, the rotor speed deviation, is the same as Fig. 5.a which has so mach distortion. According to some tested, which have been done, found that a system can stable or unstable if the system is only installed with PSS or a location of the FACTS is not fixed with an optimization algorithm. Fig. 7 show the characteristic of the IEEE 57-bus power system with GUPFC control system, where Fig. 7.a, Fig. 7.c, Fig. 7.e, Fig. 7.g, and Fig. 7.i show that the characteristic of the system are going to stable condition for the running only until 5 s. Furthermore Fig. 7.b, Fig. 7.d, Fig. 7.f, Fig. 7.h, and Fig. 7.j show that the system run until 5 s to show the power system oscillation can be damped, so good, with permanent steady-state condition which is the same as -bus case. In addition, the nonlinear model of the GUPFC in multimachine power systems has been modelled, in other paper which is in press, showed right capability to damp the power system oscillation. The GUPFC model is tested in a multimachine power systems with 3-machine 4-bus where the constants are found with MATLAB programming and then the nonlinear dynamic simulation is demonstrated in the MATLAB/Simulink environment using the Power System Block-set (PSB). For the sake of an application in large multi-machine power systems the model and a power system are arranged or simulated with programming language. IV. CONCLUSIONS The major contributions to this paper are Based on the Phillips-Heffron model case, this paper propose a configuration, as the unified control for the whole controlling, that they are GUPFC and POD, with introduce the Hammons and Winning, as the modelling method in [5], that,, for gaining the damper signal and is very influential to damp power system oscillation such as torque angle, rotor speed and voltage. The basic control function of the control scheme is satisfied and it is more preferred for large-scale applicability. The application with simulation program of the linearised model of the multi-machine power system installed with the GUPFC is demonstrated in two case studies of a four-machine twelve-bus of the Kundur modified and IEEE three-machine fifty-seven-bus power systems to investigate the impact of various GUPFC control functions on the system oscillation stability and to proof the simulation program reliability. It is found that the basic control function of the GUPFC, the voltage control of the DC link capacitor, interacts negatively with the power system, thus damaging system oscillation stability. Measures to counteract the negative interaction by either adjusting or equipping the GUPFC with the POD are tested, so that system oscillation stability can be maintained, where this character is the same as the UPFC case in [9]. The results demonstrate that a satisfactory damping of power system oscillations can be achieved. It is seen that the GUPFC application is better than the UPFC for a large scale system as the multi-line control. In addition, that the GUPFC generally is superior over the UPFC, as comparison to be [9], that the using of the GUPFC is related to flexibility in power system as the multi-line control. It is especially that a lot of factor decisive the problems of the changing of controller IJECS-IJENS June IJENS

10 International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: No: 3 84 ACKNOWLEDGMENT The authors would like to thank for the support and helpful comments of academicals member of Gadjah Mada University for this work. REFERENCES [] B. Fardanesh, M. Henderson, B. Shperling, S. Zelingher, L. Gyugyi, C. Schauder, B. Lam, J. Moundford, R. Adapa, and A. Edris, Covertible Static Compensator: Application to the New York Transmission System, in CIGRE 4-3, Paris, France. Sept [] L. Gyugyi "A Unified Power Flow Concept for Flexible AC Transmission systems," IEE Proc Gener. Transm. Distrib, 39, (4), pp , 99. [3] L. Gyugyi, C. D. Schauder, S. L. Williams, T. R. Rietman, D. R. Torgerson, and A. Edris, The Unified Power Flow Controller : A New Approach to Power Transmission Control, IEEE Trans. Power Delivery, vol., no., pp. 8593, Apr [4] A. Nabavi-Niaki and M. R. Iravani, "Steady-state and Dynamic Models of Unified Power Flow Controller (UPFC) for Power System Studies", IEEE Trans. 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Ugalde Loo, E. Liceaga-Castro, L. Vanfretti and E. Acha, Synchronous Generators Modeling and Control Using the Framework of Individual Channel Analysis and Design: Part I, International Journal of Emerging Electric Power Systems Vol. 8, Issue5, Article 4, The Berkeley Electronic Press, 7. [6] P. Kundur, Power System Stability and Control, McGraw-Hill, Inc, 994. [7] H. F. Wang and F. J. Swift, "An Unified Model for the Analysis of FACTS devices in Damping power System Oscillations Part II: Multi- Machine Infinite-Bus Power Systems," IEEE Trans. Power Deliv., (), pp , 99. [8] E. V. Larsen, J. J. Sancez-Gazce and J. H. Chow, "Concept for Design of FACTS Controller to Damp Power Swing," IEEE Trans. PWRS-, (), pp , 995. Authors Rakhmad Syafutra Lubis was born in Padang Sidempuan, North Sumatera, Indonesia, on January 5, 969. He received B.Sc. degree from Department of Electrical Engineering, Universitas Sumatera Utara Medan, Indonesia in 997 and M.Eng. degree from Department of Electrical Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia in 3. He is currently pursuing the Ph.D. degree in the Electrical Engineering Department at the Universitas Gadjah Mada, Yogyakarta, Indonesia, in the field of power system control and optimizaton. He is a Lecturer in the Department of Electrical Engineering, Faculty of Engineering, Universitas Syiah Kuala, Banda Aceh, Indonesia. His research interests are in Power System Restructuring /Deregulation, FACTS Technology, Optimal Power Dispatch and Security Analysis, Power System Dynamics Operation and Control, Power System Planning and Demand Side Management, Application of Genetic Algorithms and Interior Point Algorithm in Power Systems. Sasongko Pramono Hadi He is Doktor degree in Electrical Engineering. He is a Lecturer in the Department of Electrical Engineering and Information Technology, Gadjah Mada University Yogyakarta, Indonesia. His research interests are in power system operation, power system stability, power system control, electrical machine analysis, and power system analysis. Tumiran He is PhD degree in Electrical Engineering.. He is a Lecturer in the Department of Electrical Engineering and Information Technology, Gadjah Mada University Yogyakarta, Indonesia. His research interests are in power system operation, high voltage engineering, high voltage system insulation, and renewable energy IJECS-IJENS June IJENS