PC-based Real-Time Simulation of Large Power Systems Comes of Age at IEEE PES General Meeting
This week in Calgary, hundreds of electrical engineers from industry and academia will meet at IEEE PES General Meeting. During the show, Opal-RT will demonstrate their ability to conduct Real-Time Simulation of large power systems comprised of over 300 buses …on a PC-based Real-Time Simulator.
PC-based Real-Time Simulators Come of Age for use with Large, Complex Power Grids
Simulators have been extensively used in the planning and design of power transmission systems for decades. The state of the art has evolved from physical/analogue simulators, such as Transient Network Analyzers (TNAs) for electromagnetic transients and protection and control studies, to hybrid TNA/Analogue/Digital simulators with the capability of studying electro-mechanical transient behavior, to fully digital real-time simulators.
With each evolutionary leap in simulator technology, electrical engineers have been able to conduct a greater number of tests of networks under study, thereby increasing the efficiency and safety of the overall power grid.
Although technology has continued to evolve, up until now digital Real-Time Simulators have remained affordable only for a very few large manufacturers and national utilities. This has occurred in stark contrast to the evolution of the power grid, which over the last two decades has transformed from a unidirectional network that was only capability of delivering power generated from a few sources, to a bi-directional grid that has become increasingly reliant on Distributed Generation power sources, such as wind farms, photovoltaic cells, and other micro-grid applications.
Such a massive transformation has placed an increasing amount of pressure on Real-Time Simulator developers to evolve the state-of-the-art in simulation technology to accommodate the needs of electrical engineers to conduct high-fidelity simulation of power electronic devices inherent in the new power grid, and to make simulation technology affordable for smaller utilities and power electronic manufacturers.
Until now, digital Real-Time Simulators have been built using custom hardware or very costly supercomputer technology. Such customization has been a requirement due to the lack of availability of commercially available processor technology and high-speed communication links that were up to the task of simulation transient phenomena with a high degree of performance and accuracy.
This has forced simulator developers to invest significant resources into the development of customized hardware to meet engineering demands, in turn keeping the cost of digital real-time simulators out of reach of all but the largest utilities and manufacturers. As a result, many electrical engineers have had to rely on off-line simulation platforms to conduct transient studies; platforms that can take hundreds of times longer to produce results than digital real-Time Simulators. This has resulted in dramatic lengthening of the design process or studies that do not involve a sufficient number of tests to ensure safe and efficient power system operation.
However, with the advent of multi-core processing technology from manufacturers like INTEL and the availability of high-speed, low-latency communication links from developers like Dolphin, it is now possible to develop digital Real-Time Simulators using commercial-off-the-shelf hardware and software that are capable of conducting efficient, high-performance simulation of even the largest power grids.
Opal-RT Technologies, based in Montreal, Quebec, Canada, was founded in 1997 based on the vision that commercial PC technologies would eventually evolve to the point that large power grid simulation could be conducted on commercial hardware platforms.
The company was founded by Jean Belanger, who had spent the previous 25 years at Hydro-Quebec developing that utility’s first commercially available digital Real-Time Simulators.
“At Hydro-Quebec, we developed fully digital simulators designed to replace hybrid simulators by less costly solutions. Since commercially available PC processors were not fast enough for simulation applications, the first digital simulators were built using custom computer boards equipped with DSP (Digital Signal Processors) technology and specialized embedded processor chips, since normal PC chips were not fast enough for this application,” said Mr. Belanger. “These were experimental and very expensive systems, but represented the only way to achieve a typical time step of 50 microseconds required to simulate electromagnetic transients and to interface with real control and protection systems.”
Since it would take years for processor and communication technology to catch up with the Opal-RT vision, the company honed its expertise in the simulation of electric drive and fast-switching power electronic devices; technology that had already been embraced by the automotive and aerospace industry designers and engineers.
This led Opal-RT to develop engineering simulators and Hardware-in-the-Loop (HIL) testing equipment used by major automotive manufacturers such as Toyota, GM, Renault, Ford, Delphi, and Ford in the design and test of the rapidly growing number of power electronics found in vehicles, as well as the development of electric drives found in today’s increasingly ubiquitous hybrid electric vehicles.
PC-based Real-Time Simulators Come of Age
The automotive and aerospace industry experience has served Opal-RT well. As the nature of the power grid has changed in recent years, so has the pace of proliferation of complex electric drives and fast-switching power electronics found in today’s power grid. At the same time, commercially available multi-core processor technology and low-latency communication links now make it possible to conduct distributed real-time simulation of the largest and most complex power systems on PC-based real-time simulators.
As a result, Opal-RT launched the eMEGAsim Power Grid Real-Time Simulator in 2007. Built using Intel CORE2 Quad-core processors, FPGA-based Input/output modules, and high-performance, low-latency Dolphin communication links, eMEGAsim is capable of conducting simulations of large power grids incorporating Distributed generation devices like wind farms and associated fast-switching power electronics at the lowest simulation time-step possible today.
eMEGAsim is based on RT-LAB, Opal-RT’s real-time simulation software environment provides tools for conducting simulations of highly complex models on a network of distributed targets, in order to achieve the required performance.
RT-LAB analyses SIMULINK block diagrams and generates code that can be distributed and executed across multiple PC processor cores and, as required, on FPGA processors. RT-LAB controls all data communication between processors, IO systems and the host through a Dolphin PCIexpress Real-Time communication link. On-line modification of model parameters, as well as real-time data logging, is also managed by RT-LAB.
eMEGAsim is fully integrated with MATLAB/Simulink and SimPowerSystems toolbox for power-system simulation; the de facto standard modeling environment in the automotive industry and in wide use by universities and research centres worldwide. However, in order to achieve hard real-time simulation with adequate accuracy, Opal-RT provides additional toolboxes.
ARTEMiS is a suite of fixed-step solvers and algorithms that optimize Simulink models of electro-mechanical systems that incorporate SimPowerSystems blocks, for real-time execution. ARTEMiS also facilitates the distribution of large, complex power systems model over multiple processor cores.
RTeDrive and RT-Events are toolboxes developed by Opal-RT and available as a blockset library under Simulink, which allow detection and compensation of switching events that occur between time steps.
Large Power System Simulation Benchmarks
As proof of the capabilities of eMEGAsim to simulate such large networks, the company is demonstrating at the 2009 IEEE Power & Energy Society general meeting new benchmarks for the simulation of very large grids and networks that incorporate a large number of fast-switching IGBT power electronic devices.
The above example illustrates the capability of the eMEGAsim simulator to simulate very large power grids at a 50 us time step.
In this specific case, only three (3) 8-CPU eMEGAsim modules are interconnected to simulate a power grid with more than 330 three-phase busses and 500 transmission lines, connected to 130 generators and loads. This performance is achieved using only 20 of the 24 available 2.3 GHz processors and a DOLPHIN communication system.
Larger and more complex systems can be simulated by using faster 3.2-GHz processors and more computers. Such simulators are useful for testing the complete performance of complex AC/DC power grids with several HVDC systems and FACTS that will interact together and with fast digital protection and global control systems.
To learn more about Real-Time Simulation of this model with eMEGAsim, click here.
Opal-RT is also demonstrating the simulation of a power system that incorporates a large number of power electronic devices.
The above model is simulated on an eMEGAsim target computer equipped with dual Intel® Core TM 2 Quad Processors, 2.3GHz, 2 GB RAM, achieving a minimum time-step of 45 microseconds.. The power system has two different voltage ratings: the EHV (Extremely High Voltage) portion is rated 500 kV, 50 Hz with a nominal generation power of about 8000 MVA and the HV (high voltage) section is rated 220 kV, 50 Hz with a total generation of 4500 MVA.
Both sub networks are connected to Wye windings of a three winding step-down transformer (500kV/220kV), while a reactive power compensation substation is connected to the 35 kV delta winding. A 55% portion of the total compensation is a capacitor bank of 120 MVArs. A multi-level, 192-pulse STATCOM, rated at 100 MVArs is also connected to the 35 kV bus.
Complete alternator models including governor and excitation system dynamic are used. All six synchronous generators are standard d-q reference frame models.
The governing system consists of a hydraulic turbine with a PID controlled-servomotor for the water gate opening. The field voltage of the synchronous generators is controlled using an IEEE type 1 synchronous machine voltage regulator combined with a DC exciter. The field voltage regulation system also includes a multi-band power system stabilizer (PSS). This standard PSS model (IEEE std. 421.5, PSS4B type) uses the rotor speed deviation of the synchronous machine to output an auxiliary stabilizing signal, which modulates the field voltage reference, in order to damp power system oscillations.
Twelve transmission lines are simulated by the ARTEMIS Distributed Parameters Line model (or DPL), which is based on the Bergeron’s travelling wave method.
Eight groups of hybrid loads comprise 70% induction motor and 30% constant impedance loads with a power factor of 0.9.
To learn more about Real-Time Simulation of this model with eMEGAsim, click here.
Opal-RT was founded on the strength of many years experience in large power simulation and a vision as to how the state of simulation art would evolve. This experience, combined with extensive expertise in fast-switching power electronic simulation and a commitment to developing simulation platforms that leverage open, easily available hardware and software technologies now has poised the company to lead the industry in its next evolutionary leap.
