A new Type of Electrohydraulic Speed Governor for Large Hydropower Units

The paper presents a new concept of electrohydraulic speed governor suited for large hydropower plant, patented by the authors, and successfully applied in Romanian hydropower plants. The main idea of the new concept is the use of a compact multistage electrohydraulic servovalve with digital controller, replacing a distributed electrohydraulic system. From a design point of view, the main problem raised by such a servovalve is the proper choose of the steady-state behavior, in close connection with the shape of the spool lands. The high-speed synchronization of a unit needs a small flow gain, and the emergency shutdown demands a very big flow. The main tool for the optimization of such a nonlinear control system is the numerical simulation with a specific software like Simcenter Amesim. The theoretical results obtained by simulation for two practical implementations in a Romanian hydropower plant correspond with the performance test performed by an independent laboratory.