文档介绍：Modelling and transient stability of large wind farms
1 .Introduction
Denmark has currently about 2300 MW wind power cesign of windmills for large offshore applications and their control that shall be taken into account with respect to improving the short-term voltage stability.
system stability requirements
In terms of short-term voltage stability,the major goal is the voltage re-establishing after failure events in the power system with large amount of wind power. The transmission system operator is responsible for maintaining power system stability and reliable power supply.
As the situation is today, the majority of the Danish windmills on-land are stall wind turbines equipped with conventional induction generators and ac-connected to the power system. In case of a short circuit fault in the power system, those windmills are easily overspeeded and, then, automatically disconnected from the power system and stopped. Such automatic disconnections will be very fast and ordered by the windmill protection system relay settings. When the on-land windmills are automatically disconnected, there is no dynamic reactive compensation demands related to them, despite their large power capacity. When the voltage is re-established, the on-land windmills will be automatically re-connected to the power system in 10-15 min afterwards and continue their operation,
The on-land windmill relay settings are decided by the windmill manufacturers or the windmill owners and these, as usual, cannot be changed by the transmission system operator.
In case of the large offshore wind farms, the power system operator has formulated the Specifications for Connecting Wind Farm to Transmission Network. In accordance with the Specifications, the voltage stability at failure events in the external power system shall be maintained without any sub-sequential disconnection of the large offshore wind farms. Establishing dynamic reactive compensation of the large offshore wind farms can be, there