Interfacing Power System and ICT Simulators: Challenges, State-of-the-Art and Study Cases

Transcription

1 IEEE Power & Energy Society eneral Meeting 2014 National Harbor, MD, USA, July 31th, 2014 IEEE Task Force on Interfacing Techniques for Simulation Tools Interfacing Power System and ICT Simulators: Contributors: S. C. Müller, H. eorg, J. J. Nutaro, E. Widl, Y. Deng, P. Palensky, M. U. Awais, M. Chenine, M. Küch, H. Lin, S. Shukla, C. Wietfeld, C. Rehtanz and M. Stifter

2 Motivation Transition towards smart grids and cyber physical energy systems Rise of wide-area monitoring, protection and control (WAMPAC) systems Interaction of power system and ICT becomes more and more important, but is often simplified in simulations Involvement of many entities for reliable execution of applications Communication (PMUs to PDC, inter/intra substation, controls, ) IT data processing (decision making algorithms, ) Latencies all along the ICT chain could be influential / critical Impact on sequence of events, overlapping communication traffic Impact on real-time performance of time-critical applications (e.g. wide-area protection systems) Threat of cyber attacks

3 ICT-based WAMPAC systems Need for integrated analysis of power and ICT system for WAMPAC applications Failures in power and ICT systems can lead to critical situations in power system operation mutual effects in both networks (e.g. overlapping network flows) real-time capability of WAMPAC applications depends on whole system behavior Detailed modeling of both networks is necessary for performance evaluation in order to guarantee overall real-time requirements.

4 Focus of paper Providing a first reference for power system engineers outlining the challenges of a combined simulation of power and ICT systems presenting the State of the Art of available solutions and research approaches exemplifying the value and possibilities of an integrated simulation at the example of test cases Topic cannot be covered extensively on 8 pages Bringing together a team of experienced research groups for focusing on the most critical aspects from their perspective

5 Team TU Dortmund University Developers of INSPIRE co-simulator S. C. Müller, H. eorg, M. Küch, C. Rehtanz, C. Wietfeld, Austrian Institute of Technology (AIT) Dedicated research group on complex energy systems and interfacing techniques P. Palensky, E. Widl, U. Awais, M. Stifter Virginia Tech Developers of ECO co-simulator Y. Deng, S. Shukla, H. Lin Oak Ridge National Laboratory Developer of ADEVS simulator J. J. Nutaro KTH Stockholm Research group on real-time and hardware-in-the-loop simulation M. Chenine

6 Structure I. Introduction II. Modeling and Simulation Principles Power Systems Communication networks III. Challenges of an integrated analysis of both domains State of the Art: Interfacing power and ICT systems simulators Simulation frameworks Co-simulation approaches IV. Real-time and hardware-in-the-loop approaches Exemplary case studies Impact of cyber-attacks on PMU-based state estimation (using ECO simulator) Impact of ICT scenarios on power flow control application (using INSPIRE simulator) V. Outlook and conclusion VI. References

7 Outline Motivation and focus Team Modeling and simulation principles of power system and ICT simulators Challenges of an integrated analysis of both domains State-of-the-art of interfacing power and ICT systems simulators Simulation frameworks, co-simulation, real-time and hardware-in-the-loop simulation Exemplary case studies Impact of cyber-attacks on PMU-based state estimation (using ECO simulator) Impact of ICT scenarios on power flow control application (using INSPIRE simulator)

8 Modeling and simulation principles Excellent tools for distinct domains available Fundamental mathematics and numerical methods are available for simulating smart power systems Difficulty lies in the cost of creating new models within new simulation frameworks for hybrid systems Strong incentive to reuse existing simulation tools and models within tools Tradeoff as choice of picking two out of three options: a. Reuse of communication and power system models within well-established simulation packages b. Accurate simulations of interactions between the two domains c. Rapid execution of combined simulation

9 Modeling and simulation principles Power System Simulation Continous time calculations: System of different algebraic equations (DAEs) governed by fundamental physical laws Physical coupling & dynamic interaction of many individual components and large number of interdependent states (e.g. all synchronous machines are coupled via network frequency and influence each other) DAEs solved by numerical integration methods physical continous time processes simulated using discrete time steps Communication network simulation Functional modeling of hardware and software processes as sequential processing and transmission of messages and signales Simulations with help of discrete sequence of events in time Events are localized at nodes and only affect other nodes indirectly, e.g. by delay Often complex processes happening at software and hardware layers modeled by statistical models with random distributions

10 Modeling and simulation principles Challenges of integrated analysis Time synchronous and deterministic execution of discrete event based (Communication Network) discrete time based (Power System) Object management Detect, link and handle related events in both domains Approaches for a combined analysis eneral purpose tools Simulation of hybrid models combining power system and communication network domains Tools often lack modeling libraries, solvers and validated models Co-simulation Use specialized tools for both domains, reuse validated models Challenges: synchronization at runtime, lack of adequate APIs Hardware-in-the-loop (HIL): Coupling real-world hardware with a simulation tool Similar challenges as co-simulation, plus real time constraints

11 State of the Art: Interfacing power and ICT system simulations Simulation frameworks for interfacing simulators of both domains i. High Level Architecture (HLA, IEEE 1516) ii. Functional Mock-up Interface (FMI) iii. Mosaik iv. Ad-hoc Review of advanced co-simulation approaches i. A Discrete EVent System simulator (ADEVS) ii. Electrical Power and Communication Synchronizing Simulator (EPOCHS) iii. lobal Event-Driven Co-Simulation Framework (ECO) iv. Integrated co-simulation of Power and ICT systems for Real-time Evaluation (INSPIRE) v. Other solutions and discussion Real-time and Hardware-in-the-Loop approaches

12 State of the Art: Interfacing power and ICT system simulations Interfacing Power System and ICT Simulators:

13 Interfacing Power System and ICT Simulators: Exemplary case studies Case I Scenario Description Analysis of cyber-attacks on PMU-based state estimation using ECO Scenario: 9 37 IEEE 39-bus 10-machine system (New England Test System) Each bus 1 PMU (reporting at 30 Hz) 4 PDCs (50 ms timer) and 1 Super PDC calculating final state estimation Communication links in parallel with transmission lines PDC1 Control Center PDC PDC SPDC PDC

14 Exemplary case studies Case I Simulation Results i. Normal operation (only small random PMU measurement error) ii. Link failure attack: communication link from bus 16 to 17 blocked at t = 0.2s Due to new routing measurements arrive after Super PDC timer expires System becomes unobservable

15 Exemplary case studies Case I Simulation Results iii. Link saturation attack: malicious traffic injected at t = 0.2s No immediate effect, but gradual saturation of link, from t = 0.42s on essential measurements have to compete with malicious traffic State estimation still possible due to other redundant measurements

16 Exemplary case studies Case I Simulation Results iv. Denial of Service (DoS) attack: depletion of the resources of a router by large amount of redundant data or inquiries System state switches between observable and unobservable

17 Exemplary case studies Case II Analysis of real-time performance of wide-area 25 power 29 flow control using 23 INSPIRE Scenario: Line TL0506 disconnect after t = 10s, causing overload of line TL0405 Load redispatch at Substations 4 and 5 Control Center at Substation 39 polling measurements every 100ms switching loads on demand 4 scenarios for the communication network PFC Control Center 6 PFC 4 PFC Loss 11 of transmission line PFC Communication Protocol: IEC Type 16of Messages: Lastverschiebung Flexible loads MMS Type 2 Monitoring ACSI Service: etdatavalues Switching ACSI 14 Service: 20 SetDataValue Logical Device: 13 Bay Controller (BBxx_BC_B1)

18 Exemplary case studies Case II Scenario 1 Reference scenario, no counteraction

19 Exemplary case studies Case II Scenario 2 Idle communication network Message flow: Measurements are transmitted to Control Center Control Center detects overload Control Center schedules load redispatch at Substation 4 and 5 Effect Synchronous adjustments Overload drops within less than 0.5s Clearance: 0,5s

20 Exemplary case studies Case II Scenario 3 Simultaneous line disconnect in the communication network Message Flow as before PFC PFC PFC PFC

21 Exemplary case studies Case II Scenario 3 Simultaneous line disconnect in the communication network Message Flow as before Effects: Routes needs to be updated Traffic flow changes Routing protocol causes additional delay Asynchronous adjustments Overload drops in 1.39 s resp s (both average)

22 Exemplary case studies Case II Scenario 4 Unprioritized network traffic Additional traffic load in the communication network Additional background traffic as before Message flow as before Effects: Additional delay due to non exclusive usage of the network Asynchronous adjustments Overload drops in 1.69 s resp s (both average)

23 Exemplary case studies Case II Scenario 5 Modeling of distributed redispatch in distribution grid Transmission system control needs realized by large number of decentralized entities Wireless control commands (WiMAX, TDMA (SM))

24 Exemplary case studies Case II Scenario 5 Modeling of distributed redispatch in distribution grid Transmission system control needs realized by large number of decentralized entities Wireless control commands (WiMAX, TDMA (SM)) Effects: Packet losses -> realized control effect is smaller than command Timely distribution of control realizations instead of simultaneous action Delay dependent on wireless technology

25 Conclusion Evolution of smart grids requires appropriate tools for simulating power and ICT systems together Key challenges for interfacing discrete event based ICT simulators and continuous time resp. discrete time based power system simulators Time synchronization Event handling Data exchange Various approaches available: general purpose tools, co-simulation, HIL Tradeoff between accuracy, execution time and ease of implementation Review and comparison of various state-of-the-art solutions Different time advance strategies, use of standardized frameworks,... Two case studies demonstrate capabilities of two state-of-the-art approaches as well as necessity and value of combined simulation environments

26 Thank you for your Attention!

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28 Layers of ICT-based power system operation Centralized and decentralized monitoring and control, interconnected by WAN Centralized Monitoring and Control Layer Centralized components within the Power Systems (e.g. centralized protection, control center, power plants, etc.) Components at this layer cannot communicate directly Within the simulator architecture, these components will be mapped to specialized simulators

29 Layers of ICT-based power system operation Centralized and decentralized monitoring and control, interconnected by WAN Local Process Layer Traffic arising within substation and field level (e.g. local monitoring, measurements, process control, etc.) Components at this layer can communicate directly (e.g. using optical fibres) Communication to other layers has to be transmitted using the Wide-Area Communication Layer

30 Layers of ICT-based power system operation Centralized and decentralized monitoring and control, interconnected by WAN Wide-Area Communication Layer Interconnecting the other layers Providing heterogeneous communication infrastructure (wired or wireless) Necessity of fallback solutions (e.g. dedicated wireless broadband, cellular networks, etc.)

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