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____________________.. ____________________ Computational Challenges in the Simulation of Modern Electrical Power Systems Roy Crosbie California State.

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Presentation on theme: "____________________.. ____________________ Computational Challenges in the Simulation of Modern Electrical Power Systems Roy Crosbie California State."— Presentation transcript:

1 ____________________.. ____________________ Computational Challenges in the Simulation of Modern Electrical Power Systems Roy Crosbie California State University, Chico CICSyN 2010 Liverpool 28 July 2010

2 ____________________.. ____________________ Acknowledgements The research described in this presentation is based on the work of a research team at the McLeod Institute of Simulation Sciences at California State University, Chico, USA. Team Members Richard Bednar, Professor Emeritus Roy Crosbie, Professor Emeritus and Institute Director Nari Hingorani, Visiting Research Professor Dale Word, Associate Professor, Electrical & Computer Engineering John Zenor, Professor Emeritus Financial support by the US Office of Naval Research is gratefully acknowledged 2 CICSyN, Liverpool, 28 July 2010

3 ____________________.. ____________________ Conference Themes Computational Intelligence > System Modeling & Simulation Communication Systems> Real-time Simulation & Control Networks> Distributed Power System Control CICSyN, Liverpool, 28 July

4 ____________________.. ____________________ Traditional Approach to Simulation of Power Systems A.Steady State Load Flow Studies B.Dynamic Simulation of Transient Behavior –Seminal Analysis by Dommel –Nodal Circuit Analysis + Implicit Trapezoidal Integration –Non-linearities require iterative procedures –Electromagnetic Transients Program (EMTP) –50 microsecond maximum integration steps 4 CICSyN, Liverpool, 28 July 2010

5 ____________________.. ____________________ Modern Power Systems Much greater use of power converters (ac to dc & dc to ac) High-voltage d.c. transmission Renewable energy generation (solar, wind etc.) Independent power systems for ships etc. 5 CICSyN, Liverpool, 28 July 2010

6 ____________________.. ____________________ 23 ODEs, 12 switches, 2 PWM controllers with sine/triangle comparison PI control plus power calculations 6-pulse Back-to-Back Converter System 6-pulse Back-to-Back Converter System 6 CICSyN, Liverpool, 28 July 2010

7 ____________________.. ____________________ Distributed Energy System (Adel Ghandakly) Booster Rectifier Unit Booster Rectifier Unit Inverter Rectifier Unit Inverter Rectifier Unit Battery Storage Unit PowerGrid Load Photo Voltaic Unit Wind Turbine Unit DSPEC Integration System Monitoring & Control WTPEC PVPEC BSPEC

8 ____________________.. ____________________ Power System for Electric Ship Questions? 8 CICSyN, Liverpool, 28 July 2010

9 ____________________.. ____________________ Real-Time Simulation High-Speed Real-Time Simulation Why Real-Time? Simulation running at true speed allows connection to real hardware Hardware can be tested in absence of real system Plant operators, pilots etc. can be trained under realistic conditions Why High-Speed? For many systems frame times can be tens of milliseconds or longer Systems with fast dynamics or rapid switching need shorter frames Power electronic systems often need microsecond frame times 9 CICSyN, Liverpool, 28 July 2010

10 ____________________.. ____________________ Choice of Technology Many real-time simulations use a real-time version of Linux running on a high-performance PC Operating system jitter (of the order of 10 μS) limits minimum frame time Higher-performance is possible from systems with Pentium or PowerPC based processors but only with custom designs Initial solution: arrays of digital signal processors inserted in PCI bus of conventional PC with Windows OS running on host – off-the-shelf components; no problems with OS jitter 10 CICSyN, Liverpool, 28 July 2010

11 ____________________.. ____________________ TS201 Board Architecture 11 CICSyN, Liverpool, 28 July 2010

12 ____________________.. ____________________ DSP Issues Scheduling Processor Tasks –Equalizing processor execution times –Minimise inter-processor data transfers Internal Data Transfer –Common memory vs. link ports External Data Transfer –Digital and analog outputs and inputs Code efficiency –Hand-coding vs compiler efficiency –Identify efficient HLL code sequences 12 CICSyN, Liverpool, 28 July 2010

13 ____________________.. ____________________ Software Issues Choice of numerical integration algorithm –Euler vs Runge-Kutta vs implicit trapezoidal vs state-transition methods –Analyse and monitor accuracy and stability of numerical integration –Combine differential equations with integration algorithm before coding –Minimize total mathematical operations Hand coding vs optimizing compiler –Hand coding may be needed if compiler cant exploit processor architecture –Use HLL constructs that produce more efficient code 13 CICSyN, Liverpool, 28 July 2010

14 ____________________.. ____________________ Real-Time Simulation with FPGA FPGA offers competitive alternative to DSP; shorter frame times Can be programmed using Simulink blockset, VHDL, M-code Full 6-pulse model ported to larger FPGA Soft processor used for slow Ethernet interface Direct programmed high-speed Ethernet interface 14 CICSyN, Liverpool, 28 July 2010

15 ____________________.. ____________________ ML506 Board 15 CICSyN, Liverpool, 28 July 2010

16 ____________________.. ____________________ FPGA Performance vs DSP Model/PlatformMinimum Frame Time ProcessorClock Rate 6 Pulse BTB - Hammerhead Board, 23 ODEs 16 µsAD DSP80Mhz 6 Pulse BTB - TigerSharc Board, 23 ODEs 3.85µsAD TS101 DSP250Mhz 6 Pulse BTB - TigerSharc Board, 23 ODEs 2.02µsAD TS201 DSP500Mhz 12 Pulse BTB - TigerSharc Board, 39 ODEs 4.5µsAD TS201 DSP500Mhz 6 Pulse BTB - Xilinx ML506 Board, Virtex 5, 23 ODEs 450nSVirtex 5 FPGA100Mhz 16CICSyN, Liverpool, 28 July 2010

17 ____________________.. ____________________ FPGA Based Performance vs DSP 17 CICSyN, Liverpool, 28 July 2010

18 ____________________.. ____________________ The Need for Multi-Rate Real-Time Simulation CSU, Chico developed HSRT simulations with frame rates up to 2 MHz (500 nS frame times) These frame rates are needed for power electronic components but not for slower system components such as motors, mechanical components, thermal effects etc. Multi-rate real-time simulations simulate different subsystems at different frame-rates on different simulation platforms. The slower components are simulated in real-time using a commercial RTOS, often with Simulink support, for faster, cheaper model development. Multi-rate also improves performance of non real-time simulations. Multi-rate raises questions of stability and accuracy. 18 CICSyN, Liverpool, 28 July 2010

19 ____________________.. ____________________ Multi-Rate Example: Unmanned Underwater Vehicle 19 CICSyN, Liverpool, 28 July 2010

20 ____________________.. ____________________ Multi-Rate Results Multi-Rate Configuration –Converter, Switch Controller2 µsec –Feedback Controller800 µsec –Motor/Propeller µsec –Battery, Ship.1 sec –Graphics.1 sec Multi-Rate Performance on 2.16 GHz Mac Running Windows XP –All components at 2 µsec:.001x real time –Multi-rate, Motor/Propeller 50 µsec1.2x real-time –Multi-rate, Motor/Propeller 100µsec2.0x real-time 20 CICSyN, Liverpool, 28 July 2010

21 ____________________.. ____________________ UUV Effects of Multirate Ship at.1sec vs.001 sec (Identical Plots) 21 CICSyN, Liverpool, 28 July 2010

22 ____________________.. ____________________ UUV VTB 3D Model Output 22 CICSyN, Liverpool, 28 July 2010

23 ____________________.. ____________________ Power System Control Hierarchical control combines local controllers at stations and system wide control at control centers As more and more raw data is being sent from stations to control centers communication channels are overloaded On-line real-time simulators at stations can reduce data volume through processing of raw data This can facilitate more rapid detection of critical behavior and more rapid action to minimize its effect 23CICSyN, Liverpool, 28 July 2010

24 ____________________.. ____________________ Power System Communication Regional Control Center Local Station CICSyN, Liverpool, 28 July

25 ____________________.. ____________________ Power System ControlNetwork 25 CICSyN, Liverpool, 28 July 2010

26 ____________________.. ____________________ Acknowledgement The following material is based on: Power System Stability: New Opportunities for Control By Anjan Bose Chapter in Stability and Control of Dynamical Systems and Applications, Derong Liu and Panos J. Antsaklis eds Overview-Chapter.pdf CICSyN, Liverpool, 28 July

27 ____________________.. ____________________ Power system networks in North America & Europe are the worlds largest man-made interconnected networks All the rotating generators in one network rotate synchronously Any large disturbance (e.g. equipment short circuit) can make the power system unstable. CICSyN, Liverpool, 28 July Power System Networks: Stability

28 ____________________.. ____________________ Power System Networks: Control Control uses a combination of isolating switches, continuous control of voltage and power, and power- electronic switch-based control. These controls are all local (equipment/control in same substation) Regional and system-wide control is mainly limited to adjusting generation levels to adjust to slowly changing power loads CICSyN, Liverpool, 28 July

29 ____________________.. ____________________ Power System Networks: Communication System-wide control needs communication between contol centre and substations (microwave, telephone lines, increasing use of optical fibre) Lower costs, increasing bandwidth, GPS time synchronization, improved power electronics offer opportunities for fast distributed controls Increasing amount of data gathered at substations at mS rates is too voluminous for real-time transmission and control. OK for later study. CICSyN, Liverpool, 28 July

30 ____________________.. ____________________ Power System Networks: New Technologies Faster, cheaper computers –Embedded in equipment –Provide intelligence in the control loops Low-cost broadband communications –Greater volume of real-time data –Possibilities for decentralizing control Better power electronic controls –FACTS – Flexible AC Transmission Systems CICSyN, Liverpool, 28 July

31 ____________________.. ____________________ Future Research The Goal Automatic global control for system-wide transient stability. The Need Computation to analyze the situation and compute necessary control actions, has to match the time-frame of current protection schemes (milliseconds). Whether this is possible with todays technology is unknown. However, the goal is to determine what kind of communication-computation structure is needed to make this feasible. (Bose) CICSyN, Liverpool, 28 July

32 ____________________.. ____________________ Conclusion Modern electric power systems provide research opportunities that synthesize the conference themes: computational intelligence, communication systems and networks CICSyN, Liverpool, 28 July

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