ECPE 6304 - ENGR 315 ADVANCED COMPUTER ANALYSIS OF

POWER SYSTEM CONTROL AND POWER ELECTRONICS TRANSIENTS

Paulo F. Ribeiro, PhD, PE

EMTDC/PSCAD (INTRODUCTION)

EMTDC (ElectroMagnetic Transients for HVDC).

• Developed in 1975 by Manitoba Hydro to study the Nelson River HVDC power system• Used extensively for many types of power simulation studies,• Used in both Unix and PC systems • A more user friendly version of EMTP program

PSCAD (Power Systems Computer Aided Design) • A graphical User Interface to EMTDC• PSCAD V1 in 1988 on Apollo workstations, • PSCAD V2 in 1995 on Unix systems • PSCAD V3 in 1999 for PC Windows platforms. (not available in Unix).

EMTDC/PSCAD (UNIX VERSION)

Version 2, Unix• 6 Workstation computers which has license of EMTDC/PSCAD at VT

Coconut, Yew, Ash, Sycamore, Pear, Peach• Your login file “.cshrc” should be modified to include the path lines.• These computers can be accessed by other workstation

computers by telneting, or by PCs using Xwindows software.TELNETAssume you are using X machine which does not have the EMTDC license and want to telnet to Y machine

X:/home/ loginname > xhost “Y” X:/home/ loginname > telnet “Y” X:/home/ loginname > setenv DISPLAY “X”:0.0 Y:/home/ loginname > PSCAD &

XWINDOWSA trial version of Xwindows can be downloaded from http://www.starnet.com.There is a two hour usage limit.

EMTDC/PSCAD INTERFACE

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EMTDC STRUCTURE

Multiple Run Loop

Initialization

DSDYN

Network Solution

Interpolation

DSOUT

Runtime Communication

Write Output Files

Is run finished?

Main Time Loop

Solve for History Terms

Control of Multiple Run Optimization

Start EMTDC form DATA field or SNAPSHOT

TIME = TIME + DELT

Calculate history terms current injections for inductors, capacitors, transformers, lines and cables

User defined master dynamics files

Solution for Node Voltages and currents using sparsity algorithm

Interpolation algorithm, switching procedures, and chatter removal

User defined output definition file

Bi-directional socket communication to GUI

Generation of output files for future plotting

Control of Multiple Run Optimization

PSCAD/DRAFT MODULE

• Collection of components or circuits can be dragged from library palette into drawing canvas to assembly a circuit.

Network Components:RLC components, Transformers with saturation, Frequency dependenttransmission lines cables, synchronous machines, induction motors with excitergovernor and turbine models, faults, breakers, surge arresters, current voltage sources, multiple harmonic injectors

Power Electronics Components:Thyristors, diodes, GTOs, HVDC valve group, SVS and FACTS devices

Control Blocks:Derivative, delay, differential lag, integrator, limit, complex pole, real pole, leadlag, filter, amplifier, switch and Boolen functions

Meters:Voltmeters, ammetters, real reactive power meters, peak detectors, phase angle and frequency meters

PSCAD/DRAFT MODULE

• The components can be rotated mirrored, selected, deselected, grouped, movedcopied, cut or pasted. The wires can be resized.• User components can be created• Subsystems • Meters to measure electrical quantities• Output Channels to plot measured quantities• Operator controlled inputs (slider, push button, etc.) to provide interactive control during a simulation• Miniature Pallets for navigation• Circuit can be loaded, saved from batch pull down menu, and can be either printed to a file in postscript format or to a printer• Circuit compilation conducts a “sanitary check” and creates files for RUNTIME module.

If there is any warning or errors, diagnostic message pops up after compilation

PSCAD/RUNTIME MODULE

•Console setting is performed from “create” pull down menu• plots and meters to display the monitored outputs• slider, push buttons to interactively control the inputs during the simulation run

• Plots can be zoomed, scaled or resized.• Three curves into one graph and 5 graphs into one plot• Plot and output time output step can be reentered• Pressing a single menu button, simulation is started. The simulation then can be paused,single stepped, resumed or stopped.• After initialization process (reaching to a steady state, a snapshot file can be created.• “Filename.out” is created to document, print or analyze the results using MULTIPLOT.• Repeated simulations are created using “Multiple runs” feature• Double precision to avoid numerical instability

PSCAD/MULTIPLOT MODULE

• This module is used for documentation and analysis of the results.• Fourier Analysis• Waveform Calculator• Graph formatting and labeling

• Flexible layout• Files of “Filename.out” and “Filename.inf” are needed to plot the monitored outputs• Can be printed to a file in .ps format or a printer.

• Output file can be processed using any other software once the correspondence of each column is known.

EMTDC/TYPICAL STUDIES • Find overvoltages in a power system due to a fault or breaker operation. Transformer non-linearities (ie saturation) are a critical factor and are represented. Multiple run facilities are often used to run hundreds of simulations to find the worst case when varying the point on wave of the fault, type of fault, or location of the fault. • Find overvoltages in a power system due to a lightning strike. This simulation would be performed with a very small time step (nano-seconds). • Find the harmonics generated by a SVC, HVDC link, STATCOM, machine drive (virtually any power electronic device). Detailed models for thyristors, GTO, IGBT, diodes.. are required, as are detailed models of the associated control systems (both analogue and digital). • Find maximum energy in a surge arrester for a given disturbance.

• Tune and design control systems for maximum performance. Multiple run facilities are often used here as well to automatically adjust gains and time constants.

EMTDC/ TYPICAL STUDIES (cont)

• Investigate the Sub-Synchronous Resonance (SSR) effect when a machine and multi-mass turbine system interacts with series compensated lines or power electronic equipment. Controls systems can also be modified to investigate possible SSR mitigating methods. Modeling of STATCOM or Voltage Source Converters (and detailed models of their associated controls)

• Study interactions between SVC, HVDC and other non-linear devices.

• Investigate instabilities due to harmonic resonances, controls, interactions...

• Investigate the pulsing effects of diesel engines and wind turbines on the electric network. Insulation coordination.

• Variable speed drives of various types including cycloconverters and transportation and ship drives.

• Industrial systems including compensation controllers, drives, electric furnaces, filters, etc. Feeds to isolated loads.

EMTDC/PSCAD compared to EMTP

• Graphical data input (Draft).• Graphical execution (Runtime).• Printing plots during simulation run.• Less set up time.• Less solution time.• Interaction with users.• Initialization, snapshot files.• Switching interpolation, exact switching instant.• Chatter removal from inductive node voltage and capacitive current by employing half step interpolation• Fortran interface for modeling network dynamic and control.• No computer expertise is required with the PSCAD interface.

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