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Experiences with Real-Time Hardware-in-the-Loop Simulation
This document presents work from the 7th International Conference on Real-Time Simulation Technologies, focusing on the development and implementation of an excitation control system and wide-area control systems using real-time hardware-in-the-loop (RT-HIL) simulation. It highlights collaborations between KTH and Statnett SF, detailing experiments conducted to assess excitation control systems, including testing of power oscillation damping and custom embedded controllers. Additionally, the document discusses the integration of open-source SCADA systems and PMU measurements for enhanced power system monitoring and control.
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Experiences with Real-Time Hardware-in-the-Loop Simulation
- 1. The 7th InternationalConference on Real-Time Simulation Technologies Montreal | 9-12 June, 2014 Experiences with RT-HIL: Implementation of Excitation Control System, Development of Wide Area Control Systems, and Open Source SCADA Setup M. Shoaib Almas1, Eldrich Rebello1, Prof. Luigi Vanfretti1,2 msalmas@kth.se, luigiv@kth.se , rebello@kth.se Electric Power Systems Dept. KTH Stockholm, Sweden Luigi.Vanfretti@statnett.no Research and Development Division Statnett SF Oslo, Norway
- 2. The 7th InternationalConference on Real-Time Simulation Technologies Montreal | 9-12 June, 2014 • The work presented here is a result of the collaboration between KTH SmarTS Lab (Sweden), Statnett SF (Norway) • This work has been financed by: • Statnett SF, the Norwegian transmission system operator, through its Smart Operation R&D program. • The Nordic Energy Research through the STRONgrid project. • The following people have contributed to this work: • KTH SmarTS Lab: Dr. Luigi Vanfretti, M. Shoaib Almas, Maxime Baudette, Viktor K. Appelgren, Eldrich Rebello • Statnett SF: Stig Løvlund, Jan O. Gjerde, Dr. Luigi Vanfretti. • ABB Switzerland: Valerijs Knazkins, Ralf-Bachmann Schiavo
- 3. Outline • SmarTS Lab,previous experience • Integration of commercial controls (Unitrol 1020, ABB) • Development and testing of custom embedded controller (NI cRIO) • Future development of combined test with commercial and custom controls • SCADA deployment in the lab • PMU Integration into SCADA
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- 6. Previous Experience: PMU Appsfor Monitoring What about control ?
- 7. Mechanical Power (Pm) Pm Vfield Generator Excitation System Generator Terminal Voltage Metering Transformer Rotor FieldCurrent Transmission Line Load TURBINE Step Up Transformer Application - Testing/Verification: RT-HIL Assessment of Excitation Control System 1. Provides direct current to the synchronous machine field winding and controls the terminal voltage. 2. Provides protection functions to ensure that the capability limit of synchronous generators is never exceeded. 3. Important features: Terminal voltage control, over and under excitation limiters, field current limiters and protections, etc. Interaction between synchronous generator and excitation control system
- 8. TURBINE Mechanical Power (Pm) Pm Vfield Generator Dynamic Load 230kV, 50 Hz Bus 1 Bus 2 Transmission Line Length = 20 Km Voltage = 230 kV Bus 3 20kV : 230 kV Step Up Transformer 100 MVA 50 MW Turbo Generator 2-Pole, 20 kV Voltage Transformer 20kV:100 Field Voltage Generator Terminal Voltage VAC Current Transformer IB 1500:1 Generator Stator Current UPWR,UAUX Auxiliary Power Supply (UAUX) for powering up excitation unit and Power Electronics Supply (UPWR) for IGBT circuit Supplied from same source PWM scaled from 0 to 100 % and represents actual field voltage output of 0.5 to 99% Ifield Rotor Field Current Excitation current of generator is scaled between 9 to 10 V representing 0 to 150 % of excitation current. This analog signal is fed to the Ie External of ABB Excitation System. Real-Time Hardware-in-the-Loop (RT-HIL) simulation of an Excitation Control System (ECS) for both terminal voltage regulation and power oscillation damping Test Case System includes detailed model of Synchronous Generator whose field excitation is provided by ABB’s Unitrol 1020 Application - Testing/Verification: RT-HIL Assessment of Excitation Control System
- 9. Real-Time Simulator Ethernet Switch 0-10 Vinput to amplifier gives output of 0-100V 0-10 V input to current amplifiers give current output of 0-6 A V and I Amplifiers 1 Test Case model being executed in real-time using Opal-RTs eMEGAsim Real- Time Simulator 2 UAC : Generator Terminal Voltage IB: Generator Stator Current 3 Amplified Generator Voltage (ML1, ML3) Amplified Generator current (MC2+, MC2-) Rotor Field Current sent to analog input of Unitrol as Ie External (AI1, BI1) PWM scaled (0-10V) representing actual field voltage 0.5-99% Computer with CMT 1000 to tune parameters of Unitrol 1020 Low level voltages and currents from RTS are sent to amplifier Interfacing Unitrol-1020 Excitation Control System with Opal-RT Real-Time Simulator
- 10. Event Instance (sec) Disturbance Changein Load 1 t = 0 Simulation starts (no load) 0 2 t = 47.1 ABB Excitation System takes over 0 3 t = 108.9 Load increase 10 MW and 10 MVAR +10MW,-10MVAR 4 t = 171.3 Load increase to 20MW & 10 MVAR +10MW 5 t = 222.0 Load increase to 30 MW & 10 MVAR +10MW 6 t = 272.4 Load increase to 35 MW & 10 MVAR +5MW 7 t = 319.5 Load increase to 35 MW & 15 MVAR +5MVAR 8 t = 407.1 Load increase to 37 MW & 15 MVAR +2MW 9 t = 482.1 Load cut off -37MW, -15MVAR 0 50 100 150 200 250 300 350 400 450 500 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 Time (sec) FieldcurrentandFieldVoltage(pu) Field Voltage From ABB Exciter and Field Current Input to Exciter Field Voltage Input from Unitrol 1020 Rotor Current Input to Unitrol as External Excitation Current 0 50 100 150 200 250 300 350 400 450 500 0 0.2 0.4 0.6 0.8 1 Time (sec) ActivePower(pu) Mechanical Power Input to Generator vs Generator Active Power Output Mechanical Power Input by Turbine Active Power Output by Generator 0 50 100 150 200 250 300 350 400 450 500 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 Time (sec) Reactivepower(pu) Reactive Power Output by Generator 0 50 100 150 200 250 300 350 400 450 500 0.9 0.95 1 1.05 1.1 1.15 Time (sec) Voltage(pu) Generator Terminal Voltage Generator Terminal Voltage Vmeasure Vsetpoint Error PID Controller Field Voltage (PWM) To Real-Time Simulator RT-HIL Assessment of Excitation Control System Auto Mode of Unitrol 1020 ECS (Voltage Regulation) RT-HIL results with Auto Mode (Voltage Regulation Mode) Disturbances Incorporated in the Test Case
- 11. PID Controller Field Voltage (PWM) To Real-Time Simulator Ifieldsetpoint Error Ifieldmeasure EventInstance (sec) Disturbance Change in Load 1 t = 0 Simulation starts (no load) 0 2 t = 44 ABB Excitation System takes over 0 3 t = 193 Load increase 1 MW +1MW 4 t = 254.4 Load increase to 5MW +4MW 0 50 100 150 200 250 300 0 0.5 1 1.5 2 2.5 Time (sec) FieldCurrentandFieldVoltage(pu) Field Voltage from ABB Exciter and Field Current Input to Exciter 0 50 100 150 200 250 300 0 0.05 0.1 0.15 0.2 Time (sec) ActivePower(pu) Mechanical Power Input to Generator vs Generator Active Power Output 0 50 100 150 200 250 300 -0.25 -0.2 -0.15 -0.1 -0.05 0 Time (sec) ReactivePower(pu) Reactive Power Output by Generator 0 50 100 150 200 250 300 0.8 1 1.2 1.4 1.6 Time (sec) Voltage(pu) Generator Terminal Voltage Field voltage input from Unitrol 1020 Field current input to Unitrol as External Excitation Current Mechanical Power Input by Turbine Active Power Output by Generator Generator Terminal Voltage RT-HIL Assessment of Excitation Control System Manual Mode of Unitrol 1020 ECS (Field Current Regulation) RT-HIL results with Manual Mode (Field Current Regulation Mode) Disturbances Incorporated in the Test Case
- 12. RT-HIL Assessment ofExcitation Control System Power System Stabilization Using Unitrol 1020 ECS (PSS) Low Pass Filter K PSS Gain Washout Filter 1+T1s 1+T2s Phase Compensation Lead-Lag Filter Limiter dw Vmeasured Vreference ΔVPSS Excitation Control System VField Model of a conventional Δω PSS Frequency Calculation Power Calculation Generator Terminal Voltage Generator Stator Current UM IM Washout Filter Lead-Lag Compensator PSS Gain Washout Filter Power System Stabilizer (PSS) f V2 V1 Pe ΔVPSS To ECS Simplified model of PSS incorporated in Unitrol 1020 ECS
- 13. RT-HIL Assessment ofExcitation Control System Power System Stabilization Using Unitrol 1020 ECS (PSS) G1 G2 Area 1 Local Loads900 MVA 900 MVA 900 MVA 20 kV / 230 kV 25 Km 10 Km 900 MVA 20 kV / 230 kV 967 MW 100 MVAR (Inductive) -387 MVAR (Capacitive) 220 Km Parallel Transmission Lines Power Transfer Area 1 to Area 2 10 Km 25 Km G3 900 MVA 900 MVA 20 kV / 230 kV G4 900 MVA 20 kV / 230 kV 900 MVALocal Loads 1767 MW 100 MVAR (Inductive) -537 MVAR (Capacitive) Area 2 Bus1 Bus2 Klein-Rogers-Kundur two area, 4-machine test system for PSS performance evaluation of Unitrol 1020 ECS
- 14. 0 10 2030 40 50 60 70 0.9 0.92 0.94 0.96 0.98 1 1.02 1.04 1.06 Time (sec) RotorSpeed(pu) Case 1: No PSS Rotor Speed of All Generators (wm) Machine 1 Machine 2 Machine 3 Machine 4 0 10 20 30 40 50 -200 -100 0 100 200 300 400 500 600 700 800 Time (sec) ActivePower(MW) Case 1: No PSS Active Power Transfer Between Area 1 and Area 2 Active Power Transfer from Area 1 and Area 2 0 10 20 30 40 50 60 -10 -5 0 5 10 15 20 Time (sec) RotorAngle(rad) Case 1: No PSS Rotor Angle Deviation of All Generators (d-theta) Machine 1 Machine 2 Machine 3 Machine 4 Response of Klein-Rogers-Kundur test system without PSS Response of Klein-Rogers-Kundur test system with Unitrol-1020 ECS’s PSS
- 15. 0 5 1015 20 25 30 35 40 45 50 0.996 0.997 0.998 0.999 1 1.001 1.002 1.003 1.004 Time (sec) RotorSpeed(pu) Comparison of Generator 1 Rotor Speed for all Cases No PSS Multi-Band Pass PSS Delta Speed PSS Delta Power PSS SVC based POD 0 5 10 15 20 25 30 35 40 300 350 400 450 500 550 Time (sec) ActivePower(MW) Comparison of Power Transfer from Area 1 to Area 2 No PSS Multi-Band Pass PSS Delta Speed PSS Delta Power PSS SVC Based POD 5 % magnitude step is applied at the reference voltage of Generator 1 at t=20 sec for all the cases (left). Control Application (2): Development and testing of Custom Controls • Development of algorithms for Power oscillation damping (Simulink implementation for pre-study): • 3 different PSS controllers and 1 POD controller for SVC • Testing on Klein-Rogers-Kundur test case with RT simulation • Controller tuned for damping 0.64 Hz inter-area oscillation
- 16. Control Application (3): Developmentand testing of custom embedded controller • Implementation of a control with PMU-based phasor POD algorithm on NI cRIO embedded platform: • PMU measurements received on remote PC with S3DK and forwarded to the controller through NI shared variables • Remote PC for tuning parameters of the controller • Controller Hard wired to the simulator for RT-HIL
- 17. Control Application (3): Developmentand testing of custom embedded controller OPAL-RT 2 Real-Time Digital simulation is converted to Analog / Digital Signals through I/O s 1 RealTime simulations are accessed from the console generated by OPAL-RT Lab software Ethernet Switch SEL-421 (PMU) SEL-5073 (PDC) Concenterates all the PMU streams, time-alligns them and creates a single PDC stream BabelFish Unwraps the PDC stream and provides Raw Data in Labview to develop visualization and control applications based on PMU measurements TCP UDP Shared Variables Analog Outputs of the RTS are wired to the CT/VT inputs of the PMUs 3 4 The PMU streams are fed to the Network switch and these streams are made accessible to the Phasor Data Concentrator 56 7 NI-cRIO executes control algorithms based on PMU measurements and sends the control actions to the RTS SEL-487E (PMU) SVC Controller for Power Oscillation Damping G1 G2 Area 1 Local Loads900 MVA 900 MVA 900 MVA 20 kV / 230 kV 25 Km 10 Km 900 MVA 20 kV / 230 kV 967 MW 100 MVAR (Inductive) -387 MVAR (Capacitive) 220 Km Parallel Transmission Lines Power Transfer Area 1 to Area 2 10 Km 25 Km G3 900 MVA 900 MVA 20 kV / 230 kV G4 900 MVA 20 kV / 230 kV 900 MVALocal Loads 1767 MW 100 MVAR (Inductive) -537 MVAR (Capacitive) Area 2 Bus1 Bus2 Model-to-data workflow for RT- HIL validation of custom embedded POD Controller POD Controller Response to different Input Signals Available input signals : Voltage magnitude, voltage phase angle, current magnitude, current phase angle, active power, reactive power
- 18. Future Control Application: WAPODcontrol signal to local PSS • Future development and testing will be oriented to the combination of custom and standard/commercial controls WAPOD Controller AVR PSS PMU PMU PMU UPOD UTERM Feedback to Simulation Field Voltage UPWM
- 19. Implementation of anOpen Source SCADA system in a laboratory • Using SEL Relays as DNP 3.0 / Modbus Sources • Evaluating performance using RT-HIL simulation • Test case: 3-phase to ground fault at Bus 2 SEL-487 E Slave 1 SEL-421 Slave 2 ABB RED 670 Slave 3 Arbiter Sentinal 1133A Slave 4 DNP3 Master Open Source SCADA Poll(request) Response Poll(request) Response G1 G2 G3 G4 Bus1 Bus2 Model Simulated in Real-Time using Opal- RT eMEGAsim Real-Time Simulator Three phase Voltage and currents measurements of Bus1 and 2 are sent from Opal-RT to the amplifiers to rise low level inputs to the 100V and 1 Amp range Amplified voltages and currents are hardwired to the CT and VT inputs of SEL-421 DNP3 Outstation 1 (Slave 1) DNP3 Outstation 2 (Slave 2) DNP3 Master Poll(request) Poll(request) Response Response DNP3 Master is an open source web browser based SCADA (SCADA BR) which polls all the outstations to get update of respective data points 1 2 3 5DNP Master Master Address: 1 IP Address: xxx.xxx.xxx.210 Polling Rate: Update every 1 sec DNP Slave 2 Slave Address: 102 DNP Port: 20000 IP Address: 192.168.53.129 DNP Slave 1 Slave Address: 101 DNP Port: 20000 IP Address: 192.168.53.130 Data workflow for the test case simulation Supervision Application: Open Source SCADA Implementation
- 20. SCADA BR GUI:analog quantities and protection function status Plots showing the two minute window captured by SCADA BR during the RT-HIL simulation. • Trend of the three phase real power (MW) and voltage (kV) • Status of digital signals representing operation of protection functions i.e. overcurrent protection for all the three phases at 17:47:10 Supervision Application: Open Source SCADA Implementation
- 21. Supervision Application: Open SourceSCADA Implementation • Watch-list showing the alarms that rose for all digital status at 17:47:10: • Orange flags show that these are critical events. • The user can either acknowledge these alarms or silence them
- 22. Supervision Application: PMU Integrationfor Power System Monitoring and Control • Integration of PMU measurements into SCADA BR with S3DK No standard protocol support from SCADA BR • Publishing SCADA to remote HMI/SCADA Client and iPhone using Pachube
- 23. PMU measurements PMU measurements retrievedfrom SCADA Database Supervision Application: PMU Integration for Power System Monitoring and Control Applications • Integration of PMU measurement in the SCADA system successful • The data is intact in the database • Limitations in the update rate and plot resolution in this SCADA system • Successful activation of overcurrent alarms ! (prior to receiving trip report)
- 24. Conclusion • Power SystemMonitoring Applications • Integration of commercial controls (Unitrol 1020, ABB) • Development and testing of custom embedded controller (NI-cRIO) • SCADA deployment in the lab • PMU Integration into SCADA
- 25. Thank you! • Questions? •http://www.kth.se/en/ees/ omskolan/organisation/avd elningar/eps/research/smar ttslab • http://www.vanfretti.com • msalmas@kth.se • luigiv@kth.se • baudette@kth.se
- 26. References 1. M.S. Almas,L. Vanfretti, Stig Løvlund, and J.O. Gjerde, “Open Source SCADA Implementation and PMU Integration for Power System Monitoring and Control Applications”, IEEE PES GM 2014, Washington DC, USA 2. M.S. Almas, M. Baudette, L. Vanfretti, S. Løvlund and J.O. Gjerde, “Synchrophasor Network, Laboratory and Software Applications Developed in the STRONg2rid Project”, IEEE PES GM 2014, Washington DC, USA 3. M. Klein , G. Rogers and P. Kundur "A fundamental study of inter-area oscillations in power systems", IEEE Trans. Power Syst., vol. 6, no. 3, pp.914 -921 1991 4. ABB-Unitrol 1020 Automatic Voltage Regulator, available online: http://tinyurl.com/Unitrol
Editor's Notes
- #2 Hello Everyone. My name is Almas and i am a PhD candidate at the Royal Institute of Technology, Sweden. Today i will be presenting some of the results from our recent experiences with Real-Time Hardware in the Loop implementation of a commercial Excitation Control System. In addition there will be some slides on external controllers developed on National Instrument based cRIOs and some results from integration of PMU measurements into open source SCADA.
- #3 Before i start i would like to acknowledge the financial support from Nordic Energy Research within the Sustainable Energy systems 2050 initiative and technical support from Statnett (which is Norwegian TSO). Last but not the least i would like to acknowledge the technical support and donation of Excitation Control System by ABB Switzerland.
- #4 I follow the following scheme of presentation. I will briefly present the architecture of Smart Transmission System Laboratory at KTH where all these experiments were performed. Then i will highlight some of the applications which were developed last year at KTH and are related to power system monitoring. Then i will present the main topic which is RT-HIL implementation of ABB’s Excitation control system which will be followed by some slides on Open Source Scada and integration of PMU measurements in the Open Source Scada.
- #5 The figure shows the architecture of Smart Transmission System Laboratory at KTH. We have two real-time simulators from Opal-RT each equipped with 12 cores 64 Analog Outputs, 32Analog inputs and 128 D I/Os. The voltages and current signals are fed to the PMUs and relays either by using conventional hard-wired technique or by using IEC 61850-9-2 sampled values. In conventional technique, the low level analog signals are fed to the linear amplifiers to step up the voltages and currents to a level acceptable by the PMUs and the protection relays. In case of IEC 61850-9-2, the protection relays receive the sampled values from Opal-RT at 80 samples per cycle.
- #6 This is how the lab physically look like.
- #7 I will briefly go through some of the applications related to WAMS that we have developed in the recent past. Starting from top rite, this is a software development toolkit which we have named babel fish. It provides effortless connection to any PMU /PDC stream which is IEEE C37.118 compliant. So only things the researcher or the WAMS developer needs to know is the IP address, the port number and the device ID of the synchrophasor stream. The toolkit parses the data i.e. unwraps the PMU/PDC stream and provides real-time access of raw measurements i.e. phasors, digitals and analogs. The middle figure on the top shows a WAM application of Nordic Grid where the LEDs show the location of some of the PMUs deployed in universities in the Nordic region. This monitoring application provides instant overview of the voltages, currents, phase angles, frequency at different locations. On the bottom left is the application for mode estimation where spectral estimation algorithms have been incorporated to estimate the frequency of the dominant electromechanical oscillatory mode. On the bottom middle is the application for sub-synchronous resonance detection which is a major issue in a power system with high penetration of DG based enery. Finally an interface was developed for smart phones and tablets to get a hollistic overview of the power system in the real time. However all these applications are related to power system monitoring. But what about power system controls.
- #8 As an initiative for developing real-time power system control applications, the first application which was considered was performance assessment of an excitation control system with real-time hardware in the loop approach. The figure shows a single line diagram of the interaction between a synchronous generator and an excitation control system. The generator is receiving mechanical power input from a turbine and its field excitation is provided by an excitation control system. Terminal voltage of the generator is fed to the excitation system which compares this value to the set-point (reference voltage) and computes required field current to bring the terminal voltage to the reference value.
- #9 It is the same figure as shown in the previous slide but the excitation control system is replaced by the ABB’s Unitrol 1020 Excitation control system. It takes the generator terminal voltage as an input and computes the required field voltage which is needed in order to maintain the terminal voltage of the generator. In addition it also takes generator stator current as an input to make sure that the stator current limits are not exceeded.
- #10 This figure shows the coupling of RTS with the Excitation Control System. So the mathematical model of Synchronous Generator, Transmission Lines, loads, transformers is modeled in MATLAB and executed in Real Time using Opal-RT simulator. The generator terminal voltage and stator current are accessed from Analog outputs of the RTS and are fed to the amplifiers to amplify them to a range which is acceptable by the ECS. Real-Time Simulator (RTS) can only provide voltages upto ±10 V and currents upto ±20 mA. These low-level signals (generator terminal voltage and stator current) are amplified using linear amplifiers to scale voltage upto 100 V and currents to 1 Ampere at rated power [6]. The field current measurement is supplied to Unitrol 1020 using low-level ±10 Volts. For this purpose one of the inputs of Unitrol 1020 is configured for receiving an external excitation current. The complete connection diagram is shown in Figure 3.
- #11 Unitrol 1020 ECS has 4 control modes. AVR (AUTO), FCR (Manual), Power Factor Control Mode and VAR Control Mode. This slide shows the RT-HIL results of Automatic Voltage Control mode of ECS. In AVR mode, Unitrol 1020 is a PID controller regulating the generator terminal voltage by computing the required field voltage to maintain the reference voltage. In the test system, the load was increased as shown in the table. Top left plot shows the generator terminal voltage vs the field voltage input from the ECS. As the load is increased, the terminal voltage decreases and ECS comes into play which increases its field voltage to keep the terminal voltage equal to 1 pu.
- #12 Similarly for verifying the Manual control mode of the ECS, In the test system, the load was increased as shown in the table. Top left plot shows the generator terminal voltage vs the field voltage input from the ECS. As the load is increased, the terminal voltage falls below 1 pu and then manually you need to increase the field voltage output of the ECS to maintain the terminal voltage of the generator. However as you can see, we cannot apply huge load changes in this case, as it will result in loss of synchronism of the generator and the simulation will crash. So the manual control mode or field current regulation mode is much harder to validate.
- #13 The PSS is a feedback controller and is part of the control system of a synchronous generator, which acts through the excitation system to provide an additional signal to modulate the field voltage. The main function of PSS is to damp generator rotor oscillations in the range from 0.1 to 2.5 Hz, which are called electromechanical oscillations The simplest method to provide a damping torque in the synchronous machine is to measure the rotor speed and use it directly as an input signal in the stabilizer structure. The simplest one is known as IEEE PSS1A model [11] and is documented in the IEEE Standard 421.5-2005 [5]. It is illustrated in Figure 12. It consists of a low-pass filter, a general gain, a washout filter which is effectively a high-pass filter, a phase-compensation system in the form of lead-lag compensator, and an output limiter. The general gain “K” is proportional to the amount of damping produced by the stabilizer. The washout high-pass filter allows the PSS to respond only to transient variations in the speed input signal “d𝞈”. The phase-compensation system is represented by lead-lag transfer functions used to compensate the phase lag between the excitation voltage and the electrical torque of the synchronous machine. The output limiter ensures to bound the amount of control action of a PSS during a major system disturbance and thus avoids the PSS to adversely affect the generator’s synchronism.