Analysis For Fast Valving Technology Of Supercritical And Ultra-supercritical Power Unit In Theory And Simulation

The application of supercritical and ultra-supercritical power unit make thermal power generation more clean,environmental and efficient.However,its damage is larger than the average unit in the power grid failure.So,fast valving technology should be used to protect the security of the unit and reduce the economic losses.The technology can rapidly decrease turbine power to reach a new equilibrium in the power grid failure.In this paper,the 660MW unit and 600MW unit produced by Shanghai Steam Turbine and Harbin Steam Turbine are analyzed and evaluated based on the machine and power network coupled model by using PSCAD software.First,the basic concept and application background of fast valving control are introduced.The research status of ultra-supercritical power unit and digital electro-hydraulic control system are summarized.The research results of fast valving logic and modeling-simulation are explained.In addition,the importance of fast valving technology of supercritical and ultra-supercritical power unit is analyzed.Then,different types and effects of fast valving control are clarified on the basis of the basic principle of digital electro-hydraulic control system.Global decision logic of fast valving control is analyzed from the schematic diagram.A strategic assessment system which guides primary frequency parameter adjustment is proposed and the causes of fast valving accidents are verified.In addition,synchronous motor and generator excitation system mathematical model are analyzed and electrical power system transition process is elaborated.A monolithic line adjustment system is proposed to optimize plant operation after analyzing the bending and torsion vibration of turbo set during the malfunction of ultra-high voltage transmission under three malfunction evaluation index.Furthermore,machine and power network coupled model are established based on simulation software.The reasonability and the accuracy of the model are verified from the manufacturer test data.The operation condition of fast valving control when fault of power grid occurs is analyzed through the simulation to analyze the effects.At last,the effects of fast valving control in different grid faults are simulated from five parts,which are the types of failure,grounding faults,fault distance,fault duration and transmission line inductance.The conclusion can be drew that different fast valving schemes are able to keep the stable operation of unit in different grid failures by comparing 660MW unit and 600MW unit.The simulation results show that the length of the closing hold time has no influence on the effect of the operation.The optimal fast valving control time method is proposed.Based on the results of simulation,the existing protection logic is refined and the reliability of fast valving control is improved.The optimized parameters standard of fast valving control is proposed,which can be used to obtain a good result of directions for optimization.