SUCCESSFUL DYNAMIC PERFORMANCE TEST OF THREE SVCS IN SAUDI ARABIA

Transcription

1 SUCCESSFUL DYNAMIC PERFORMANCE TEST OF THREE SVCS IN SAUDI ARABIA ABSTRACT P. Thepparat, M. Sezer, R. Münchmeier, D. Retzmann Siemens AG, Guenther-Scharowsky-Str., 91058, Erlangen, Germany Saudi Arabia s power demand grew very fast during the last years, the overall performance of power systems therefore reduce with the size, the loading and the complexity of the network. For the improvement of this situation the rapid reactive power support by providing Static VAR Compensators (SVC) in the central region was brought up. A SVC provides fast voltage support and transient stability related to the interconnections and the large percentage of induction type air conditioner loads in the network. As air conditioners are the main load in Saudi Arabia the SVC should provide enough reactive power to avoid the voltage collapse or motor stalling when single phase to ground fault occurs. Siemens Energy was awarded the supply of three SVCs at different high-voltage levels in the beginning of the year 010. The SVCs will be installed at Hiteen, Qassim and Afif substation at 380 kv, 13 kv and 33 kv systems, respectively. They are scheduled to be ready for operation between mid 011 and mid 01. Before taking these three SVCs into operation at the respective substations in Saudi Arabia, the dynamic performance tests are performed at the testing laboratory in Erlangen, Germany to ensure the correct control performance of the SVCs. The control of the SVC is based on the state-of-the-art automation system SIMATIC TDC (Technology and Drive Control). The large network, implemented in Real-Time Digital Simulator (RTDS), including a number of equivalent induction motors in different locations together with the three SVCs is a challenge and the details of the implementation are clearly explained in paper. In this paper, the successful dynamic performance test of these three SVCs is presented. KEY WORDS: Dynamic performance test, motor stalling, Real-Time Digital Simulator, SIMATIC TDC, SVC 1. INTRODUCTION The demand for electricity in Saudi Arabia has continuously increased. During the past eleven years the available generation capacities, electrical power transmission network length and electrical power distribution length have been increased by 14% (from 4,083 MW to 51,148 MW), 70% (from 9,166 ckm to 49,675 ckm) and 86.8% (from 19,076 ckm to 409,89 ckm), respectively. Furthermore, when comparing the year 011 with 010 the growth of these indicators is about 4.1%, 7.6% and 7.3% [1]. In addition, the total peak loads is about 48,367 MW which increases 5.9% comparing with year 010 [1]. It can be obviously seen that the development of electrical power system in this region is necessary to achieve the demand. The fast growth of power system could cause the voltage stability problem if the generation and transmission system are not developed correspondingly, therefore the improvement of the rapid reactive power voltage support in the central region of Saudi Arabia by SVC was brought up. 1/11

2 Particularly, air conditioners are the major load in Saudi Arabia, the voltage collapse causing motor stalling when the fault occurs is therefore very risky []-[7]. The SVC should provide enough reactive power to avoid such problem. Siemens has received an order from Saudi Arabia to supply three turnkey SVC systems for different high voltage levels for stabilization of the country s 60 Hz power transmission network. The SVCs will be deployed at three sites in the Hiteen, Qassim and Afif in central region shown in Figure 1. The SVC Hiteen is located directly in Riyadh, the capital of Saudi Arabia. The SVC Qassim is placed in the province of Qassim, close to the city of Buraidah, 400 km northwest of Riyadh. The SVC Afif is located in the city of Afif, 450 km west of Riyadh, half-way between Riyadh and Mecca. Purposes of these SVCs system are to provide adequate reactive power support without subsequent over-voltages and prevent voltage collapse or motor stalling at least during single-phase to ground fault. Figure 1: Location of Hiteen, Qassim and Afif SVCs Before these SVCs are in operation, the Dynamic Performance Test (DPT) in Erlangen, Germany of SVCs together with a large network system implemented in Real Time Digital Simulator (RTDS) [8] becomes a challenge. The detail of implementation will be explained in below sections. In the paper the project details and the test procedures in Siemens will be explained. Then implementation of large network in RTDS will be discussed. Finally, the results of DPT will be depicted.. PROJECT DETAILS AND DESIGNS The SVC Hiteen, Qassim and Afif will be installed at different high voltage levels on 380 kv, 13 kv and 33 kv and with dynamic compensation capacities of 00 ind. to 800 cap. Mvar, 150 ind. to 450 cap. Mvar and 50 ind. to 100 cap. Mvar, respectively. The single lines of the SVCs are shown in Figure, 3 and 4. /11

3 The SVCs has a continuously adjustable reactive power output mentioned above. The component design, control tolerances and operation are considered at ambient temperatures of -5 to +50 C, +5.1 to +50 C and +5.1 to +50 C for Hiteen, Qassim and Afif. Each SVC mainly consists of anti-parallel Thyristor Controlled Reactor (TCR), anti parallel Thyristor Switched Capacitor (TSC) and filter. The filters are designed to eliminate the harmonic generated by TCR and to avoid the possible resonance to the AC system impedance. The secondary side bus voltage is selected by considering the most economic utilization of the SVC equipment, especially the thyristor valves. The design of the thyristor valves includes stresses from misfiring for the TSC valves and dc trapped current for the TCR valves following rated operating conditions of the valves. This covers most severe transient stresses to be expected under the system conditions as specified by customer. At Hiteen substation, a Mechanically Switched Capacitor Damping Network (MSCDN) having a nominal power rating of 00 Mvar is connected to the 380 kv bus. 3AC 60Hz 380kV C1MSCDN1 SN = 600 MVA, uk = % CMSCDN1 LMSCDN1 R1MSCDN1 Arr 3AC 60Hz 5kV MSCDN1 LTCR1 LTSC1 CDTF11 CDTF1 CDTF31 CDTF41 LTSC LTCR V1 VR1 LDTF11 LDTF1 LDTF31 LDTF41 V VR LDTF1 LDTF LDTF3 LDTF4 LTCR1 CTSC1 CDTF1 RHP1 CDTF RHP CDTF3 RHP3 CDTF4 RHP4 CTSC LTCR TCR 1 TSC 1 DTF 1 DTF DTF 3 DTF 4 TSC TCR Figure : Single Line Diagram of Hiteen SVC with MSCDN Figure 3: Single Line Diagram of Qassim SVC The SVC control system design is divided to open loop control (OLC) and close loop control (CLC) functions. Siemens has been used the state-of-the-art control and protection system named Win-TDC: SIMATIC Win CC and SIMATIC TDC (Technology and Drive Control) [9] for control and protection system. 3/11

4 3AC 60Hz 33kV 3AC 60Hz 33kV LTCR1 LTSC1 LF1 LF RHP LF3 RHP3 V1 VR1 VC1 CF1 CF CF3 LTCR1 CTSC1 STF 1 STF STF 3 TCR 1 TSC 1 Figure 4: Single Line Diagram of Afif SVC SIMATIC Win CC shown in Figure 5 is the process display and control system utilized in the HMI including plant operation, monitoring, operator guidance, sequence-of-events recorder, event analysis, trend plots and archiving of operational data. SIMATIC TDC shown in Figure 6 is a high performance, state-of-the-art automation system which allows the integration of both open loop and high-speed close loop controls within this single system. The engineering tool to graphically configure the control and protection functions in SIMATIC TDC is named Continuous Function Chart (CFC) shown in Figure 7. The outstanding advantages of Win-TDC are: Figure 5: HMI Main Page of Hiteen SVC Product life cycle of more than 5 years Very high availability due to complete redundancy at all level with hot standby All control and protection systems use the same well proven standard hardware/software Compact design 4/11

5 Human Machine Interface (HMI) using windows based, SIMATIC standard operating system Win CC (Window Control Centre) High speed digital signal processors Figure 6: SVC Control&Protection Cubicle and SIMATIC TDC Module Figure 7: Continuous Function Chart for Control and Protection Functions The control of TCR and TSC is shown in Figure 8. The output of close loop control is the ordered SVC susceptance which represents the reactive power from TCR and TSC, in Hiteen MSCDN included. The reactive power of TCR is controlled by varying the firing angle. If the capacitive power is required and at a certain point which TCR could not reduce its reactive power consumption, the TSC will be switched on. In addition, the DC component control of TCR is also required. DC component could appear in TCR current when unequal firing of thyristors in positive and negative cycles, ripple in control voltage or harmonics in power system voltage. These could cause the saturation of coupling transformer and the increase in harmonic 5/11

6 generation, which are then resulted in instability or even overheating of internal parts of the transformer. Figure 8: TCR and TSC Control When the control and protection functions are already programmed in SIMATIC TDC, the control and protection cubicles will be connected to RTDS which is used to perform all dynamic performance tests. In RTDS the AC equivalent system and electrical component of SVCs are modeled. The steady state and dynamic behavior of real control, protection and measuring system are studied in parallel with offline simulation e.g. PSCAD/EMTDC. The detailed set-up of RTDS will be discussed in next section. 3. REAL TIME DIGITAL SIMULATOR (RTDS) SET-UP As specified by customer to test three SVCs performance together the accurate AC network is implemented in RTDS. Because of the hardware limitation in RTDS, the whole network consisting a thousand of buses could not directly model in RTDS. The reduced AC network which still represents the accuracy in comparison to the original network from the customer is created. In this example the peak load case in summer which is a concerned condition due to 80% of load is the air conditioner, is described. The reduced network representing the network in Hiteen, Qassim and Afif areas consists of 97 nodes, 114 transmission lines, 14 generators, 69 loads and 19 lumped induction motors representing air conditioners. In this dynamic performance test, three cubicles shown in Figure 9 each having two racks are used to model reduced AC network and three SVCs. In each rack, it could roughly consist of electrical nodes with a limited number of machines, generators and transformers. The SVC component is modeled in the upper rack physically connecting via interface cards to the SIMATIC TDC in which the control function is already programmed. The AC network of each system will modeled in the lower rack. To couple the AC network together, the Bergeron transmission line model is required. For this reason the selected lines to decouple the system between the racks have to be carefully considered. Taking into account the travelling wave effect, the minimum length of these line models must be 18 km in corresponding to 60 µs simulation time step. The minimum length of line model could be simply calculated from (1). Light Velocity is 3x10 5 km/second 6/11

7 Min_Line_L ength(km) = Simulation_Time_Step( μ s ) Light_Velocity(km / s) (1) SVC Control Qassim RTDS Qassim SVC Control Hiteen RTDS Hiteen RTDS Afif SVC Control Afif AC Equivalent Qassim AC Equivalent Hiteen AC Equivalent Afif Figure 9: SIMATIC TDC Modules and RTDS Cubicles used for Dynamic Performance Test One important model in this study is the induction motor model. In RTDS the mechanical swing equation of induction motor is represented by (). In addition the mechanical torque can be calculated as an exponential function of the machine angular speed shown in (3). T where dω Te = J Bω () dt m + T m = Kω (3) T m : Mechanical Torque T e : Electrical Torque J: Polar Moment of Inertia B: Mechanical Damping Factor ω : Angular Frequency K: Constant Value, RESULTS OF DYNAMIC PERFORMANCE TEST In the standard test matrix a number of tests based on Siemens s experience and customer s specification is created. The motor stalling phenomena when a single-phase to ground fault occurs, is mainly focused. In addition the sub-sequence overvoltage after the fault is clear must be avoided. 7/11

8 During the fault the slip of induction machines increases and the machines tend to lose their speeds rapidly. This is similar to a starting condition which the high current of approximately five time nominal current. For this reason the high reactive power is required otherwise the voltage collapse and motor stalling phenomena will occur. It is also worth to mention that regardless of fault types, the longer the fault duration, the more motor prone to stall and voltage system will not recover. Due to a number of tests during DPT, some interesting dynamic performance tests i.e. case 1, and 3 near Hiteen SVC in peak load condition are selected and depicted for discussion. The fault duration is 7 cycles of 60 Hz system for all cases. The graphs depict the AC instantaneous voltages at Hiteen, RMS voltage at Hiteen, RMS voltage at Afif, RMS voltage at Qassim, susceptance reference from SVC Hiteen, Afif and Qassim, and active/reactive power of lumped induction machine near fault, in sequence. It can be seen that the SVCs supply the reactive power to system during the single-phase to ground fault. This avoids the voltage sag during system disturbance and helps for system recovery. All induction motors can be able to recover to the pre-fault operating point and no motors suffer from stalling phenomena. Case 1: Local Single-Phase to Ground at Hiteen SVC bus Figure 10: Peak Load Dynamic Performance Test - Local Single-Phase to Ground at Hiteen SVC bus 8/11

9 Case : Remote Single-Phase to Ground near Hiteen SVC bus Figure 11: Peak Load Dynamic Performance Test - Remote Single-Phase to Ground neart Hiteen SVC bus Case 3: Local Single-Phase to Ground at Hiteen SVC bus and unsuccessful auto-reclosure of line Figure 1: Peak Load Dynamic Performance Test - Local Single-Phase to Ground at Hiteen SVC bus and unsuccessful autoreclosure of line 5. CONCLUSIONS In this paper the details of turnkey SVC projects - Hiteen, Qassim and Afif located in central region of Saudi Arabia is explained. Before installation and commissioning, the SVCs are 9/11

10 needed to complete Dynamic Performance Test (DPT) in Erlangen, Germany to ensure the SVCs control performance. The process of design, control and protection software/hardware set-up connecting to RTDS cubicles, in which the large equivalent AC network and SVC components are modeled, is described. The results of DPT show that the SVCs can mitigate the voltage collapse causing motor stalling phenomena when the single-phase to ground fault occurs and no sub-sequence overvoltage after the fault is clear. After successful DPT of these SVCs, the control and protection cubicles are delivered to the sites and connected to the SVC systems for commissioning. 6. REFERENCES [1] SEC, Saudi Electricity Company Annual Report 011, 011 [] John W. Shaffer, Air Conditioner Response to Transmission Fault, IEEE Transactions on Power Systems, Vol. 1, No., May 1996, pp [3] G. K. Stefopoulos, A. P. Meliopoulos, Induction Motor Load Dynamics: Impact on Voltage Recovery Phenomena, Transmission and Distribution Conference and Exhibition, 005/006 IEEE PES, 1-4 May 006 [4] C. D. Vournas, G. A. Manos, Modelling of stalling motors during voltage stability studies, IEEE Transactions on Power Systems, Vol. 13, No. 3, August 1998, pp [5] J. V. Milanovic, M. T. Aung and S. C. Vegunta, The influence of induction motors on voltage sag propagation Part I: Accounting for the change in sag characteristics, IEEE Transactions on Power Delivery, Vol. 3, No., April 008, pp [6] J. V. Milanovic, M. T. Aung and S. C. Vegunta, The influence of induction motors on voltage sag propagation Part II: Accounting for the change in sag performance at LV buses, IEEE Transactions on Power Delivery, Vol. 3, No., April 008, pp [7] B. R. williams, W. R. Schmus and D. C. Dawson, Transmission Voltage Recovery Delayed by Stalled Air conditioner Compressors, IEEE Transactions on Power Systems, Vol. 7, No. 3, August 199, pp [8] Real Time Digital Simulator RTDS, [9] Win-TDC The State-of-the-Art Control and Protection System, [10] PSCAD/EMTDC Simulation, 7. BIOGRAPHIES Pakorn Thepparat was born in Thailand in He received the B.Eng. degree at Kasetsart University, Thailand in 001, the M.Sc. degree at RWTH Aachen, Germany in 006 and the Dr.-Ing. at Ilmenau University of Technology, Germany in 010. All degrees are in Electrical Engineering. He worked for EGAT Electricity Generating Authority of Thailand during in Transmission Control System Development Department, Transmission System Maintenance Division and was responsible for HVDC SCADA systems. Since 009 he is with Siemens AG, Erlangen, Germany. His working areas are system integration, control and protection study for HVDC and FACTS. He is active in CIGRE B4 and VDE. His research interests are power electronics, system integration and HVDC&FACTS control and protection. Murat Sezer was born in Söke, Turkey in He received the B.Sc. degree with honors in Electrical Engineering from Yildiz Technical University Istanbul in 00, the M.Sc. degree from Istanbul Technical University in Control and Automation Engineering in 005. Since 007 he works as a system engineer for the Simulation Control and Protection department by Siemens AG, Germany. His expertise area is the Real Time Digital Simulator (RTDS) for FACTS and modular multilevel converter (MMC) for SVC PLUS 10/11

11 Rudolf Münchmeier is Senior Project Manager at Siemens AG, E T PS PM1 (Energy Sector, Power Transmission Division, Power Transmission Solutions Business Unit) and since 011 Team Leader of FACTS Group Order Processing Middle East / Saudi Arabia. From 010 up to 011 he was responsible as project manager for the SEC Saudi Arabia turn key projects SVS Hiteen, 800 / 00 MVar, 380kV, SVC Qassim, 450 / 150 MVar, 13kV and SVC Afif, 100 / 50 MVar, 33kV. He studied electrical engineering at the University in Erlangen, Germany, Diploma in 1989, joining Siemens in 1990, working as commissioning engineer, sales engineer and project engineer. Since 00 he is a project manager at the FACTS department. Dietmar Retzmann was born in Pfalzfeld, Germany on November 4, He graduated in Electrical Engineering (Dipl.-Ing-) at the Technische Hochschule Darmstadt, Germany in 1974 and received the Dr.-Ing. Degree from the University of Erlangen-Nürnberg in Dr. Retzmann is with Siemens Erlangen in Germany since 198. He is director of Technical Marketing & Innovations HVDC/FACTS in the Energy Sector, Power Transmission Solutions. His area of expertise covers project development, simulation and testing of HVDC, FACTS, System Protection and Custom Power as well as system studies, innovations and R&D activities. Dr. Retzmann is active in IEEE, Cigré, ZVEI and VDE. He is author and co-author of over 0 technical publications in international journals and conferences. In 1998, he was appointed guest-professor at Tsinghua University, Beijing, and in 00 at Zhejiang University, Hangzhou, China. Since 004, he is lecturer on Power Electronics at the University of Karlsruhe, Germany and in 011, he becomes lecturer on Power Electronics and Electrical Energy Systems at the University of Erlangen-Nürnberg, Germany. In 006, he was nominated "Siemens TOP Innovator". 11/11