1.07 overcoming hydraulic issues using a hydro power

Electricity Supply to Africa and Developing Economies: Challenges and Opportunities

Jean-Louis DROMMIElectricite de France

Paper Number 1.07

Session 1

15 November 2017

Overcoming Hydraulic Issues Using

Variable Speed Drive

in a Hydro Power Scheme


Overlook

• SUMMARY

– EDF overseas

– Hydraulic waterway issues

– Overcoming the hydraulic timelag

– Example of simulated case


EDF world wide

• Electricité de France

– Major player in France and in Europe

– Also abroad (Renewable USA, Laos, …)

– And French overseas regions

• Reunion island in Indian Ocean with a large share of hydro

generation that


Hydro a century old renewable

• Hydraulic waterway issue

– Hydro usually seen as flexible and quick

• In comparison to thermal

– But managing water energy must consider hydrodynamicphenomena

• Water inertia T = L Q / A g H

• Cavitation

– The case study key numbers :

• Waterway length : 4800m pennstock

• Water head : 440m

• Power : 2 units 28MW each


Reunion Island Hydro electric project

• The Reunion Island Hydro Scheme– Long penstock

– No surge tank

• Very challenging hydraulic condition– Tw = 5,1s

• Water hammer mitigation– Slow niddle speed

• Avoid penstock material fatigue– Water head

oscillation must be limited below +/-15%


Island grid code requirement

• Specific dynamic requirement for primary reserve

• Twice faster than continental Europe

• Can’t be achieved naturally


Hydraulic issues

• Overcoming hydraulic time lag and head

oscillation

– Usual practice is to install a surge tank

– Or very seldom, to install pressure tanks

– Or to innovate… with power inverter interfacing


Fully fed variable speed

• Full inverter interface, voltage source type

• And its model : pseudo continuous type


SIMULATION TOOL

• SIMSEN– On the shelf tool

• Developped by– EPFL

– Since early 1990s

• Used by severalmanufacturers

• Can perform hydro electric transientsimulation– Interaction can be

detected


Inverter control

• In house control strategy : generator side

– Active load adjusts the torque

– Reactive load can be set to zero


Inverter control

• In house inverter control : grid side

• Follow up strategy for active load

• Reactive load supplied to grid


100% load ramp up

• Some results: unit loading 100%

Release of kinetic energy

Very fast electric response; power delivered to grid

Follows the set point ramp


Load Ramp down 20% 15 sec

• Load ramp down 20%



Load Ramp up 20% 15 sec



Waterway lag time

Storage of kinetic energy


Influence of rotor inertia : 1, 2 or 3 times

Speed deep reduction with higher inertia

But longer stabilization time


To conclude momentarily and probe further

• Implementing power converters allows

to increase unit dynamic behavour

– May be of interest to reduce hydro scheme

cost

– Or to develop hydro sites not suitable with

standard technology

• Making use of rotating kinetic energy

– Acts as a temporary energy storage

– Using batteries would probably offer similar

service

– The higher the inertia, not the better


To probe further

• Simulation must be undertakenwith other types of turbine

– Francis

– Pump Turbine

• Using power converter introducesfurther opportunities

– Permanent voltage support withSTATCOM function

– Fast speed ramp up using converter as booster

– And many others yet to come …


THANK YOUTHANK YOUTHANK YOUTHANK YOU

1.07 overcoming hydraulic issues using a hydro power

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