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Gerken adds that E-Technologies even develops its own software modules and tools and then uses MiMiC to import and export them as templates via XML. "We can extend the existing software with our tools and then just click to generate PLC code, HMI tags, historian tags and models," adds Gerken.
While simulators are famous for training operators, the story doesn't end there. Once trained, users naturally and almost reflexively want to use these virtual tools to help improve and maintain their applications. This is drawing simulation into a host of new applications and closer to operations too.
For example, RWE npower's (www.rwenpower.com) two-unit, 1,000-megawatt Fawley Power Station provides electricity to 1 million people in Hampshire, U.K., so this peaking plant must start up quickly and efficiently and synchronize to the grid to cost-effectively respond to seasonal spikes in demand. Consequently, the 40-year-old, oil-fired plant has used Emerson Process Management's (www.emersonprocess.com) Scenario simulator since January 2008 to mirror its actual Ovation expert control system, which monitors and controls the boiler, turbine and other critical plant processes and systems. The station's high-fidelity Scenario simulator has virtual controller technology, in which up to five virtual controllers reside in one PC, and this enables greater affordability and scalability with a reduced footprint. Fawley has 4100 simulated I/O points that exist in 12 Ovation virtual controllers (Figure 2).Fawley reports that Scenario's training abilities are especially valuable for peaking plant operators because their work is based on fluctuating demands. In this environment, the simulator can train new operators while keeping current operators sharp and familiarizing them with new control strategies, even when the plant is not running. As a result, when extra megawatts are needed, the plant can synchronize to the grid more quickly and within the necessary parameters to avoid equipment damage.
"With the simulator, new operators can come up to the standards of more experienced operators much sooner than would be possible if they were interacting with the control system only when the unit was operating," explains David Marmot, RWE npower's electrical and instrumentation leader. "By training operators how to start the unit faster to meet peak demand, we have the opportunity to not only enhance the plant's operational performance, but our financial performance, too."
Likewise, because well-trained operators who are prepared to handle abnormal operating situations can reduce costly plant trips, Fawley also had 20 malfunctions, including critical ones, pre-programmed into the simulator to further train its operators how to respond to emergency situations. Scenario uses tie-back logic, algorithmic models and first-principle models to provide training and engineering simulations that can be tailored to meet each facility's operational needs.
"Ongoing operator training is important to power generators preparing for the retirement of experienced operators. However, beyond training operators, our customers are achieving added benefits by using our simulation technology for engineering analyses and validating new control logic," adds Bob Yeager, president of Emerson's Power and Water Solutions division.
So what's at the root of all simulations and what's driving them and their software's increasingly sophisticated capabilities? You guessed it—a huge and growing pile of mathematical calculations.For instance, GenCorp's Aerojet (www.aerojet.com) division in Sacramento, Calif., is using the MathWorks' (www.mathworks.com) MATLAB and Simulink software to build a control system to deliver constant pressure in the fuel tanks of Kistler Aerospace's K-1 space launch vehicle. When finished, K-1 will be the first commercial, reusable launch vehicle with low-cost access to space for low-earth-orbiting satellites. K-1's modified Russian rocket engine from Aerojet burns liquid oxygen (LOX) and kerosene, but as LOX levels in the tank drop, more pressure is needed to force it to the combustion chamber. To restore pressure, LOX consumed during firing is replaced with helium from external storage tanks. However, helium creates a new control engineering problem, because LOX requires steady pressure, while the helium requires constantly increasing pressure.
As a result, Perry Stout, K-1's controls engineer, developed a solution in which flow between the high-pressure helium storage tanks and the low-pressure LOX tanks is controlled by a series of flow-regulating solenoid valves and an orifice that can vary in size with ambient conditions, and used MATLAB and Simulink to design a control system that regulates valve operations and orifice size. First, he derived and wrote out the physical equations, moved these core equations into Simulink, developed and tested a model and graphically added heat-transfer equations and closed-loop control laws without writing added code. Next, he used MATLAB to analyze the design and modified it in search of optimal conditions, a task that would have taken several months using a conventional engineering process.
"If this was a Fortran project, the control system design would have involved an entire team," says Stout. "A manager would have been required to divide the modeling, simulation and control tasks among several people, closely monitor and coordinate all activity and summarize the results."
Jason Ghidella, Simulink process marketing manager for MathWorks, adds that, "Simulators are becoming more dynamic and non-linear because high-end users want better performance and safety. They want to see if their control strategy is in the ballpark, but they also want to throw all kinds of unusual conditions at it too," says Ghidella "Non-linear simulations are based on partial differential equations (PDEs) and differential algebraic equations (DAEs), and these require a lot of calculating that can't be done in traditional ways. So simulator developers must find other ways to understand and solve these dynamic problems and then generate a response."