Electric hydraulic interaction
The hydraulic models representing hydro turbines and conduit system found in
standard model libraries of power system analysis tools are often simplied mod-
els. Subsequently, important information about the dynamics of the hydraulic
system may not be properly represented by such models, putatively resulting
in insucient representation of the interaction between the electric system and
In this master thesis three dierent hydraulic models for hydro power plants
equipped with Francis turbines for use in power system simulation software has
been studied: 1) a simplied model often found in power system simulation tools;
2) a model including a surge tank and elastic water column and 3) a model that
includes a surge tank, elastic water column and turbine parameters accounting
for the characteristics of the hydraulic turbine.
The hydraulic models were implemented in Simpow, a power system simulation
tool. A frequency scan in the range from 10􀀀3-5 Hz was performed. The re-
sults were compared with a frequency scan from LVtrans, a program specically
designed for accurate simulation of the dynamics of the hydraulic side in hydro
power plants. The comparison showed that the simplied model failed to prop-
erly represent the dynamics of the conduit system. The the model with surge
tank and elastic water column was able to represent the dynamics of the con-
duit system with satisfactory accuracy. Best representation was achieved for the
model including turbine parameters.
The three hydraulic models were implemented in three dierent power system
congurations: a single machine innite bus system; a system consisting of two
interconnected areas; and a system that has sustained power oscillations. The
resulting active power delivered from the generator were the hydraulic models
was implemented, the speed of the turbine, the pressure at turbine and the
through the turbine were investigated.
The simulation results revealed that the active power variation from the gener-
ators is in the same range for all three models, except for the simulation with
sustained power oscillations. The speed variations of the turbine as a result of
incidents in the electrical network are in the same range for all three models.
The model including turbine parameters is the only model able to represent
the pressure variation as a result of a variation of speed of the turbine. For
power oscillations with frequencies equal to the half period frequency of the water
hammer eect,1.38Hz, both the model with surge tank and elastic water column
and the turbine parameter model show very little response. For frequencies equal
to the water hammer eect, 0.69Hz the variation in
ow is also small for the two
models. In general, the model with turbine parameters are better damped than
the two other models.
Further work should include development of an automated routine for determin-
ing parameters to use in the model with turbine parameters as well as investiga-
tions of how the model behaves in dierent network congurations.
Place, publisher, year, edition, pages
Institutt for elkraftteknikk , 2011. , 69 p.
ntnudaim:6268, MTENERG energi og miljø, Energibruk og energiplanlegging
IdentifiersURN: urn:nbn:no:ntnu:diva-14045Local ID: ntnudaim:6268OAI: oai:DiVA.org:ntnu-14045DiVA: diva2:445816
Uhlen, Kjetil, ProfessorToftevåg, Trond