Optimal Guide Vane Closing Schemes for Pumped Storage Power Plants

The total load rejection is one of the most critical operation cases for pumped storage power plants. In order to allow for a safe plant operation, the plant unit needs to be brought to a controlled stop. In the state of the art, this is usually done with simple (piecewise) linear guide vane (GV) closing laws. This article proposes a closing law optimization approach where all system constraints, in particular the pressure and GV servomotor limits, are systematically considered, which yields curved closing laws. This approach is applied to an emergency shutdown (ESD), partial shutdown (PSD), and quick shutdown (QSD) with a doubly fed induction machine, a synchronous generator (SG), and an SG with a full rated back-to-back converter. The results demonstrate that a curved closing law with fast closing, followed by reopening and final closing of the GV, is the optimal solution for the ESD. The optimal PSD closing law is very similar to the ESD law, and the main difference is the final partial opening of the GV in order to operate the turbine at the speed-no-load point. The QSD shows that fast and monotone closing for all generator types is possible.