Ke. Bollinger et al., REDUCING THE EFFECT OF PENSTOCK PRESSURE PULSATIONS ON HYDRO ELECTRICPLANT POWER-SYSTEM STABILIZER SIGNALS, IEEE transactions on energy conversion, 8(4), 1993, pp. 628-631
A characteristic trait of Francis turbines operating at low-head is pr
essure pulsations that occur during certain load levels of the generat
or. These stem from pressure variations across the turbine due to puls
ating flow in the draft-tube. This surging action of the water column
is related to draft-tube geometry and flow-rate of water in the pensto
ck. The pressure pulsations cause torque variations on the turbine and
corresponding electric power pulsations. If electric power is used as
a feedback signal to the Power System Stabilizer(PSS), then Mvar and
terminal voltage pulsations will occur when the generator is operating
in the ''rough zone''. This paper describes field test results for in
vestigating feedforward control from the penstock, draft tube and spir
al case pressure to reduce the effects of Mw pulsations on PSS output
signals. This investigation involved a PSS with generator power as the
feedback signal and the PSS tuned for local and inter-area damping.