| Abstrakt: |
This is the final article in a series of articles covering multi-loop control systems. The previous articles discussed the main function of the instrumentation and control systems (I&C systems) of power plant units-namely, controlling the network frequency in accordance with current requirements [2 – 4]. In this article, solutions to facilitate the implementation of algorithms developed by Intermatic AG specialists for controlling the frequency and power of large power plant units are considered. These solutions pertain to the main closed-loop control systems of a power plant unit comprising a high-power once-through boiler and the power plant unit as a whole. The key methods for ensuring the compliance of power plant unit characteristics with norms of participation in the primary frequency control (PFC) and load control (LC) are discussed in this article. These methods use the following: the "primary frequency control (PFC) and load control (LC)" instead of the existing load and power control systems known as LCS1 ("the turbine follows the boiler") and LCS2 ("the boiler follows the turbine"); various types of "forcing"; a differentiator for steam pressure upstream of the turbine, being added to the LCS control deviation. Typical problems encountered by Intermatic AG specialists at 300 and 800 MW power plant units during the commissioning and final test (considering the tests at coal-fired power plant units of Reftinskaya thermal power plant (TPP), Berezovskaya TPP, and gas-fired power plant units of Perm TPP) as well as methods for solving these problems are described in this article. Specifically, this article considers a comprehensive approach to the frequency and power closed-loop control (FPC) system engineering and commissioning. Such an approach assumes that, in addition to the main coordinated control system (CS) of power and steam pressure upstream of the turbine, the I&C systems of a power plant unit should also include up-to-date CSs for supplying the boiler with feed water and fuel; additionally, this I&C systems should also include temperature controllers for ensuring efficient boiler operation; thus, this approach unites the unit power control with the unit participation in grid frequency control, thus solving the problem of power and frequency control of power plant units. An important condition to ensure the successful resolution of grid frequency control problems in power plants is ensuring temperature control during boiler operation. The presentation of methods is accompanied by examples of temperature CS during the final test for compliance with norms of the power plant unit participation in the PFC that was successfully performed at the Berezovskaya TPP 800 MW coal-fired power plant units for the first time in the Russian power grid. [ABSTRACT FROM AUTHOR] |
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