Ferroresonance Study Of Gas Turbine Generator During SFC Startup

Gas turbine generator gets started by static frequency converter (SFC) to achieve smoothness and quickness. During the starting, the potential transformer (PT) connected at the generator outlet and capacitance to ground can match at certain frequency, which may cause ferroresonance. Ferroresonance may result in the PT getting burned or the generator failing to start, which will bring serious damage to the power plant.Taking the gas-steam combined cycle generating set as the research object, this paper studied the SFC start process of gas turbine generator and the ferroresonance during the process, the specific work as follows:Firstly, the structure and working principles as well as the relevant excitation and relay protection of SFC start system are researched according to main wiring of startup system. The commutation process of thyristors in SFC、the principles of SFC control unit and the rotor position detector are anslyzed especially.Secondly, the actual startup process of gas turbine generator by SFC was studied, the SFC output voltage and current data were collected and harmonic analysis was carried out. On this basis, from the perspective of the field, the startup processes of gas turbine generator were simulated by ANSYS Maxwell, the magnetic field inside generator was analyzed simply.Finally, from the point of view of the circuit, the simulation model including the gas turbine generator SFC startup system and PT connected at the generator outlet by MATLAB Simulink, the simulation analysis were carried out with existing data which found that ferroresonance does not occur during the startup; then simulation and comparison of the capacitance to ground、PT excitation characteristics and its iron loss influence on ferroresonance were carried out; Finally, primary side and the secondary side hrmonic elimination measures are simulated and verified.