Fast Cut Back Function Of Thermal Power Unit And Its Application For Power Gird Black-Start

Fast cut back (FCB) function of coal-fired thermal power unit can play an important role in restoring power grid and reducing the loss after great grid blackout, while the achievement of FCB function is the prerequisite to its application in the black-start and restoration of power grid. The study of this thesis is aimed at the requirements of developing the application of FCB units in black-start of the domestic power grid. Systematical analysis and investigation were performed on main factors of FCB function and their influences, the system and method for evaluating the capability of FCB function, the technical features of applying FCB units as black-start power supply and the technical and policy measures for enhancing and improving the competence of FCB units as black-start power source. The purpose is to provide theoretical basis and technical support for promoting the application of FCB units in power grid black-start.Based on summarizing the experiences of tests and investigations on existing thermal power units to implement FCB function in China, the main factors (including unit system configuration, control system settings, unit operational control, operation, auxiliary equipment performance and steam switching of steam feed-water pump) of the unit achieving FCB function and their influences were systematically analyzed and studied. As a consequence, preliminary system and method for evaluating the capability or potential of thermal power unit achiving FCB function was established. With the system and method, the evaluated issues-related characteristics and their evaluation results of the common issues among domestic units were presented. The established system and method consider the generality of existing thermal power units in China so as to be used as fundamental reference and basis for testing FCB function of the unit and assessing the capability of FCB function.Based on technical requirements of practical grid black-start for black-start power supply, Chinese policies related to FCB units used as black-start power source were assessed and the technical features of FCB units used as black-start power source were systematically analyzed, studed and expounded. It is indicated that FCB unit is high quality black-start power source. While it has many obvious advantages, it also has the issues related to economy, reliablibility and safety and, in particular, the lack of practical application and investigation. Through the analysis and comparison of current grid balck-start service systems in domestic and overseas, the requirements for improving Chinese grid balck-start service systems to adapt to the application of FCB unit as balck-start power were explored and the measures for elevating the competence of FCB unit providing black-start service.The simulation systems were employed to do the testing of fast load reduction for three typical coal-fired thermal power units. Based on the evaluation system and method of FCB function and the results of simulation tests, the capability of the three units to achieve FCB function were analyaed and evaluated, and accordingly the improvements and optimizations required for the units were put forward. A method was proposed to evaluate the capability or potential of thermal power unit achieving FCB function based on the evaluation system of FCB function and simulation testing, which can be used as the technical tool for unit FCB test, study before FCB retrofit and assessment of the capability of FCB function.