Impact of Auxiliaries Response on the Voltage Ride Through Capability of Synchronous Generator Power Plants

摘要

Voltage Ride Through Capability (VRTC) refers to the ability of generators not to trip in case of a fault in the external network. VRTC requirements were firstly imposed to wind generators to cope with massive wind farm tripping following a fault in the external network. They have been subsequently extended to synchronous generators. VRTC has been incorporated to many grid codes worldwide as a voltage-time curve that generators must withstand without tripping. VRTC has been required either at the power plant high voltage bus or at the generator low voltage terminal bus. A synchronous generator might disconnect from the grid due to either generator loss of synchronism or power plant auxiliaries tripping as a result of severe transmission system voltage transient variations. Power plant auxiliaries can be tripped either by minimum voltage protections to prevent that auxiliaries induction motors block or merely because of low voltage AC contactors drop out. Assuming that the synchronous generator remains in synchronism after a fault, the paper addresses the problem of power plant tripping due to auxiliaries tripping. The relationship between the VRTC curve and the response of both the auxiliaries and the synchronous generator is studied. Sensitivity analysis with respect to relevant parameters of the auxiliaries is provided. A fundamental simulation model of the power plant has been developed and is reported. The model includes a detailed representation of the synchronous generator and its controls. In addition, aggregated model of induction motor loads at the medium voltage bus bar of the power plant auxiliaries is considered.