Compact simulators can improve fossil plant operation
By Roy Fray and S. Murthy Divakaruni, Electric Power Research Institute
New and affordable technology can simulate operations in real time and is finding application across a broad spectrum of power plant designs
A significant breakthrough for utilities, compact simulator technology, has reduced the cost of replica simulators by a factor of five to 10. This affordable technology, combined with innovative software developments, can realistically simulate the operation of fossil power plants in real time on low-cost PC or workstation platforms.
These compact simulators are finding applications across the spectrum of control system suppliers and over a wide range of plant designs, including pulverized coal, fluidized-bed and combined-cycle units.
Application to power plant operator training has improved plant availability, reduced fuel costs, lengthened component life and enabled operation closer to environmental limits.
Application to power plant control system engineering has reduced capital costs, shortened commissioning time and lessened the risk of equipment damage.
Compact simulators are even being used as research test-beds to develop, test and demonstrate new power plant technologies.
Compact simulator development
Representatives of electric utilities worldwide, suppliers and consultants met in 1988 at the Electric Power Research Institute (EPRI) Conference on Power Plant Simulators and Modeling to look at ways of improving fossil power plant simulators. At that time, few utilities used fossil plant simulators, because they were expensive and inflexible. Recommendations from meetings like the 1988 conference have resulted in a flurry of activity to enhance and expand the use of simulators in the fossil generation industry.
Beginning in 1988, a major effort was initiated at EPRI, the Palo Alto, Calif.-based research arm of the electric utility industry. Murthy Divakaruni, who oversees EPRI?s simulator research and other efforts related to fossil plant operations, explained why the Institute became involved in fossil plant simulators. OOur utility advisors told us they wanted more effective, flexible and affordable simulators for their fossil plants. The bottom line was that they wanted to reduce costs, and they saw simulators as a key way to do this.O
Efforts to improve fossil simulators have paid off. According to an estimate compiled from utility testimonials solicited by EPRI, utility users so far project $480 million in savings through simulator use. The benefits have fallen into two roughly equal categories: operator training and control system engineering.
Through the use of compact simulators fossil plant operators are learning how to avoid preventable trips and curtailments and are increasing plant availability. Thermal performance is being enhanced by performing faster startups, reducing auxiliary loads and decreasing heat rate. Operators are honing methods of extending component life, such as avoiding life-shortening thermal cycles, while balancing fuel and life-cycle costs. Techniques for confidently operating closer to environmental limits are being practiced.
EPRI has found that after conducting operator training using a compact simulator, operators typically avoid several plant trips per year and can reduce heat rate by 1/4 percent to 1/2 percent. Typical reductions in auxiliary load, as a result of simulator training, range from 1/4 MW to 1/2 MW, and units can be recovered from shutdowns more quickly, typically one hour faster.
Simulator-based controls engineering is reducing annual outages, adding typically one full day of full-load generation per year. Depending on the application, utilities estimate annual savings that range from $1,000/MW to $4,000/MW (1993 dollars) by implementing compact simulator-based operator training.
Utility engineers are also using compact simulators to design new control systems or modify existing ones. The capability to simulate complete control systems for low cost before they are commissioned provides a powerful engineering tool for verifying, testing, debugging and pretuning This allows utilities to substantially reduce capital costs, shorten commissioning time, and lessen the risk of equipment damage.
More effective simulators
Compact simulators in use today are more effective than past simulators due to their fidelity, unit specific modeling and wide scope. The realism and accuracy stems from the dynamic simulation?the transient thermal-hydraulics model that predicts the dynamic behavior of plant processes and control systems. Using first principle models formulated from mass, energy and momentum balances, compact simulators can simulate plant conditions from Ocold metalO to 100 percent load. Essentially, the behavior of the entire power plant is realistically captured on computer.
Compact simulators can represent processes and equipment at specific generating units. Parameterized with unit-specific design and operating data, the models can be revised if plant processes and controls are updated.
The high fidelity and unit-specific nature of these simulators facilitate their applicability to control system engineering. For example, Illinois Power Co. wanted to modernize the control system at its Hennepin Unit 2 without sacrificing initial performance. The utility initiated a project with EPRI to use compact simulator technology to train Hennepin operators and validate control-system software before the installation of the new control system was completed.
Illinois Power Co. estimates savings of $4.6 million through simulator-based operator training and controls engineering for the control system replacement. Savings will result from improved operator performance and reduced commissioning time for the new control system and subsequent control modifications.
Another reason for compact simulator effectiveness is its wide scope. The full-scope models represent all major and most auxiliary systems in the plant. This is done because compact simulators emulate an exact replica of the plant control system. The simulated controls must interface with the same process I/O as the actual controls. Hence, the entire portion of the plant regulated by the plant control system must be included.
Compact simulators offer more flexibility than conventional simulators in application, modeling capability, training location and the timing of the training. They can be applied to a variety of training needs, engineering analyses, equipment and control system projects, and product/system testing uses. On the same hardware platform, the simulators can model various types of control systems by loading the appropriate models and replacing the custom keyboard template. Commonly-used turbine, boiler and auxiliary equipment can be simulated with high accuracy and realism.
Compact simulator training can now be conducted at corporate offices, generating stations or other locations using a mobile simulator installed in a trailer. Duke Power Co. projects multimillion dollar savings through use of the mobile simulator as a test-bed for new control systems at its plants.
Simulator flexibility is enhanced by the use of increasingly sophisticated instructor functions?the functions that allow an instructor to set up and run simulator exercises. Becoming increasingly graphical, these functions are being expanded to include student tracking and evaluation.
Perhaps the most significant advance in simulator flexibility is EPRI?s intelligent tutoring system (ITS). Using the ITS, operators can receive directed training even when instructors are unavailable, enabling them to train during dead time. The ITS applies expert system techniques to capture instructor expertise and provides this expertise as an extension to the simulator. By supplementing a utility?s limited ability to schedule instructors, the ITS is expected to enhance the already substantial benefits of compact simulators by as much as 25 percent.
According to Jeff Pitts, South Carolina Electric and Gas Co. (SCE&G), an ITS user, OOur simulator will not sit idle if an instructor is unavailable. Operators can run simulator exercises themselves, logging many more hours of simulator training each year.O SCE&G estimates that ITS implementation will save $594,000 over and above the estimated $2 million (present worth) savings from the simulator alone.
A variety of technologies are driving down the cost of simulators. Computer platforms for simulators have evolved from expensive, specialized mainframe computers to groups of lower cost PCs or workstation-type computers that are networked together.
In addition to the reduced cost of raw computing power, use of the fully emulated configuration of a compact simulator decreases costs. In this configuration, process, controls and the operator interface are completely emulated, and no control system hardware is needed. This enables copies of the simulator models to be used simultaneously at different locations?convenient for engineering analysis.
Advances in modular modeling are also easing costs. Rather than handcrafting a model of each power plant component, simulation system designers are drawing from libraries of existing component models and tailoring them to the specific plant. In this way, any power plant configuration can be modeled. In fact, existing full plant models have been the starting point for simulation system development when models of similar plants are available, which is increasingly the case as more simulators are implemented. OUsing an existing model from the library reduced our costs without sacrificing the capabilities of the simulator,O said David Kenien, New York State Electric and Gas Co.
Emulation of controls and operator interfaces is becoming easier and less expensive. Computer programs have been developed that emulate the screens and control algorithms of several types of control systems. In addition to reducing simulators? initial cost, these translators save utilities money when changes to the simulator are necessary to reflect control system changes. Centerior Energy estimates that by using control and graphics translators, the utility will save $903,000 (present value) on its initial simulator purchase and on changes to the simulator over the next 15 years.
To be effective, compact simulators must be combined with carefully designed training programs. However, simulator-based programs developed using processes typical of industry practice usually require several person-years to prepare and three or more months for presentation?a costly task.
To reduce these costs, Duke Power Co. and EPRI have jointly developed guidelines for developing fossil plant simulator training programs. Using the document, an effective six-week simulator training program can be prepared with about nine person-months of effort. Using the guidelines, Duke Power was able to save two person-years of simulator training program development time and cut weeks off the actual training time.
Enhancements to the ITS will increase the effectiveness and widen the range of applications for this training aid. Voice interaction, sound and graphic elements such as photos, animation and video are planned. Soon ITSs will generate a post-session retrospective log for student review. As additional ITS implementations are brought on-line, a library of ITS-supported scenarios will increase in size.
Modules for beginning, intermediate and advanced simulator training are planned, including load change, drum level control, temperature control, trip recovery and startup. EPRI will also provide tools that enable instructors to develop new ITS-supported training scenarios.
Hard-panel emulation is a second area of EPRI?s focus on enhancing compact simulators. While many fossil power plants are being upgraded to soft control system interfaces, a large number of plants with hard-panel interfaces will continue to operate into the next century. Training operators on full-sized, hard-panel simulators is too costly at most fossil plants. To reduce these costs, EPRI is developing advanced hard-panel displays. To emulate the hard panels, full-scale, high-resolution hard control images are rear projected onto large touch-sensitive screens.
Boston Edison Co. is implementing this display technology at its Mystic Unit 6. Since the technology provides an easy mechanism for emulating hard panels of different BECO generating units, the resulting simulators with emulated hard panels will allow the utility to train its operators on Mystic Units 4, 5, 6 and 7, as well as other units.
But hard-panel emulation may go beyond simulators. Using large OsoftO panels, such as those using hard-panel emulation technology, ways of displaying instrumentation and actuation equipment will be limited only by our imagination. Since the images of controls in hard-panel emulation systems are computer-generated, programmers can change the look of the controls to enhance clarity and ease of use, thus improving operator productivity and plant safety.
For example, one large display could show an overview of the entire plant process in schematic form. When an alarm flag pops up on a portion of the screen, the operator could touch the flag and view a subsystem process or component schematic, which highlights off-normal parameter values. Recommended operating procedures to correct the problem, generated by an expert system, would be available at the touch of a button. These bright, clear, high resolution displays will be at arm?s length from the operator.
Compact simulator technology will see increasing use outside of the United States. Countries such as China, India and others will be installing much new generating capacity in the next 10 years. Providing training on the operation of all these new power plants will present many challenges to utilities. Affordable compact simulator technology enables these utilities to improve the use of their fossil generation assets through better training, improved control system engineering and test beds for new generation technologies. END
EPRI`s Proceedings: Simulators, Modeling and Training Conference, EPRI TR-103826, November 16-18, 1993, New Orleans.
Justification of Simulators for Fossil Fuel Power Plants, EPRI TR-102690, October 1993.
Preliminary Guidelines for Fossil Plant Simulator Training Programs, EPRI TR-101854, July 1993.
Intelligent Tutoring: Enhancing Simulator Training,O EPRI TB-103009, December 1993.
Proceedings: 1988 Conference on Power Plant Simulators and Modeling, EPRI GS/NP-6670, February 1990.
Simulator-Based Training and Technology Transfer for Fossil Plants, An R&D Plan and Technology Assessment, Final Report, EPRI GS-6672, February 1990.
Roy Fray is manager of simulators and training at the Electric Power Research Institute in Palo Alto, Calif. Before joining EPRI, he was employed for four years with Science Application International Corp. in reliability, simulation and support for fossil generation. For 17 years at Pacific Gas and Electric Co., he was responsible for reliability risk and simulation analyses support for fossil and nuclear power generation. He holds a master?s degree in mechanical engineering from the University of California.
S. Murthy Divakaruni is manager of EPRI?s fossil steam productivity improvement team and manages the fossil plant operations program. At EPRI since 1981, he spent the first five years in the nuclear power division. Prior to joining EPRI, he worked for five years in the advanced energy department at General Electric and for two years at the Indian Space Research organization. He holds an master?s degree from Xavier University, M.S.A.S.gif. from the University of Cincinnati, master of science in mechanical engineering from the Indian Institute of Technology and bachelor of science in mechanical engineering from the University of Madras, India.
Effective, flexible, affordable, compact fossil power plant simulators that run on PC or workstation platforms are now available to electric utilities. (Source: EPRI)
Many utilities have already realized a wide range of benefits from using compact simulator technology. (Source: EPRI).
Hard panel controls such as these can be emulated by advanced touch-screen displays, enabling utilities with hard-panel controlled plants to benefit from simulator-based operator training, and ultimately to upgrade their control room displays. (Source: EPRI and MITRE Corp.)