Research Of The Steam Turbine's Sub-synchronous Oscillation When Large-Scale Wind Farms Connected To Grid

New renewable energy sources such as wind power, photovoltaic power generation technology of rapid development, wind and fire after transmission way has become commonplace.The transmission line is long distance, high voltage, high filling degree of the trend of development. Large-scale wind farm grid may be on the system of the original power plant steam turbine generator shafting subsynchronous oscillation characteristics of the impact.It leads to shafting torsional vibration phenomenon aggravate, increase the risk of aeration-cooling, so as to endanger the safe and stable operation of power grid. In July 2015, China's xinjiang region of a certain power plant steam turbine generating sets for the infusion of large direct drive wind within the same system and cause subsynchronous oscillation occurs.Shafting torsional vibration protection one after another trip and cause downtime. In the face of turbo-generator set, as a result of large-scale wind power grid synchronization phenomenon, in this paper, we consider the permanent magnet direct-drive wind power of the fan and the system of steam turbine generator.Research direct-drive wind power into the system of power plant steam turbine unit subsynchronous oscillation characteristics. The main contents include:Subsynchronous oscillation in power system is summarized and expounded current classification, mechanism, the main analysis method and existing suppression measures.Determine the characteristic root analysis method for analysis of subsynchronous oscillation method in this paper, research methods. Laid the foundation for later study.Establish a direct-drive wind farm wind machine, the pitch Angle control system, wind turbine shaft system, the mathematical model of permanent magnet synchronous generator,transformer and power plant steam turbine generator shaft system, the mathematical model of synchronous generator. By IEEE first, for example, the standard model built on PSCAD software containing a direct-drive wind farm and power system model and control strategy of turbine generator set. By running the simulation verify the correctness of the model. For exploring next subsynchronous oscillation characteristics of the simulation.According to the mathematical model of the structures, the research object system small signal stability analysis of the main parts of the model. Characteristic root analysis method is used to calculate a direct-drive wind farm grid power plant after the eigenvalues of the steam turbine generator shaft system, and find out its regularity. Using domain simulation fault reproduce the vibration response to support the analysis conclusion. Using the theory of sensitivity to the parameters and the main components of wind farms system time synchronization oscillation damping to sensitivity analysis. Find out the biggest parameters to subsynchronous oscillation damping associated degree.Finally put forward to increase reactive power output of wind farm to suppress subsynchronous oscillation of the system. Using domain simulation, verify the validity of this method, and comparing with no inhibition effect of the simulation.In this paper, the direct drive wind farm into power grid caused after study of subsynchronous oscillation characteristics of the steam turbine unit in thermal power plants has certain reference significance. It laid a foundation for subsequent take comprehensive, effective and economical suppress subsynchronous oscillation strategy research.