Plant Management
In a design process it is important to define the different operating conditions and events thoroughly in order to get the right design criteria.
condition, analysis could then be made on the whole system, the boilers, steam system, turbine frequency/power control and generator voltage control. Hence, the controls were designed and tuned even for the most complex cases. It was checked that the plant could handle all the
operational conditions set up in the requirements. This was an important stage of verification. Commissioning could then be carried out smoothly without any major changes of settings.
Importance of practical validation
The commissioning is important for the final Validation and Verification of the performance requirements. In order to verify the requirements, real tests were conducted as far as possible. One of the most difficult cases to verify, Island operation, was tested using Solvinas unique HardWare In the Loop (HWIL) simulator based test device, SolvSim Power Station. The test equipment is connected to the governor and
Fig. 3. Overview of the cogeneration plant in a pulp and paper mill.
Some of the operating conditions and events that were important for the control design were: 1. Batch steam consumption. 2. Boiler trip. 3. Trip of steam consumer. 4. Loss of main grid and transfer to island operation. 5. Load changes in island operation.
We can observe two different aspects of these requirements. The requirements on the steam system control include events and behavior in the electric grid, which means that analysis must be performed in several technical disciplines. A holistic approach is required. The other aspect is that these requirements are defined on plant level and have to be transferred into detail requirements for control systems, turbine, boiler, generator, etc. One example of dynamic requirement is island operation (Isolated grid). In this case it is not enough to just require island operation capability, but the quantitative aspects must be defined, such as frequency drop after a load change, time constants etc. (Fig. 4).
simulates an island network, so that the governor acts as in real island mode while the machine still runs synchronized to the main grid. The plant and the simulator are running together in real-time in closed loop operation. (Fig. 5).
Fig. 5. The unique test equipment using HardWare In the Loop real-time simulation.
Results
The results of these efforts were stable and reliable operation with very few outages and large amounts of energy savings. In addition, the plant start-up became very short since the control was already optimised in the simulator. Furthermore the simulator was used for operator training so that the plant staff knew what to expect when the plant was started. These successful results were reached very much thanks
Fig. 4. Broken down requirements for island operation. Engineering
A simulator model was developed of the whole steam system and parts of the power system. For a given operating
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to careful requirement management, and multi discipline engineering using dynamic simulators. l
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Niclas Krantz is Managing Director is with Solvina International, Västra Frölunda, Sweden.
www.solvina.se
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