In order to ensure that small wind turbine in the security and stability in the process of operation, the unit need not only has the capability of low voltage across, and when small wind generator in wind power field and node voltage, namely wind farm or busbar voltage step-up transformer high voltage side of the node fell to only 20% of the rated voltage, the need to be able to have the ability to keep continue to run and not to take off the net.
At the same time, on the basis of small wind turbine to the and node voltage 2 s time immediately after the voltage decline to rise to 90% of the rated voltage, and it will not be able to take off phenomenon, so it the whole operation process can be more stable.
It's about the low voltage protection of small wind turbine, the second also frequency limit of protection, the protection is mainly used to frequency fluctuation, quickly removing fan. The fluctuation of frequency in the power grid will harm the normal operation of small wind turbines. When the frequency in the power grid is higher than the fan limit value, the over-limit protection will immediately remove the fan. The typical overlimit protection value of frequency is that the frequency is greater than or equal to 50.5Hz or less than 49.5Hz of class, and the delay is less than or equal to 100ms.
The current protection is also one aspect of the protection of small wind turbines. In general, the wind turbine is equipped with the current breaking protection and overcurrent protection to protect the current. In addition, the wind power unit is equipped with three-phase current, unbalanced voltage protection, fan temperature rise, rotating speed rise, vibration beyond the limit and cable twist protection.
For variable speed constant frequency fan, the converter is widely used for vector decoupling control. At present, almost all wind farms are using a dual - fed induction generator. Type doubly-fed wind power generator in the implementation of parallel operation, the stator voltage is 690 v alternating current (ac), in order to ensure the stator chain does not change, will take relevant measures to the overvoltage and overcurrent protection.
Now doubly-fed type small unit in aspects of protection of the converter is usually adopted crowbar protection, parameters for access by the crowbar protection system: dc link overvoltage, the grid side converter by electric current, the rotor over current, etc. http://www.titanwindturbine.com/