Pelton Turbine Needle Control Model Development, Validation, and Governor Designs

Underspeed needle control of two Pelton turbine hydro units operating in a small power system has caused many incidents of partial system blackouts. Among the causes are conservative governor designs with regard to small signal stability limits, non-minimum phase power characteristics, and long tunnel-penstock traveling wave effects. A needle control model is developed from “water to wires” and validated for hydro-turbine dynamics using turbine test data. Model parameters are tuned with trajectory sensitivity. Proposed governor designs decompose the needle regulation gains into the power and frequency governor loops with a multi-time-scale approach. Elements of speed loop gain scheduling and a new inner-loop pressure stabilization circuit are devised to improve the frequency regulation and to damp the traveling wave effects. Simulation studies show the improvements of the proposed control designs.