Skip to main content

Variospeed hydropower plants


JOU2-CT93-0433 Objectives and Deliverables Until now hydropower machines (turbines and pumps) had to be designed for a fixed rotation speed. For that reason they achieve their best characteristics only at one specific operation point (defined by head and flow rate). However, in practice, hydropower machines are usually operated in wide ranges. This leads to the following disadvantages:
- significant efficiency loss in the operating range and
- narrow limits of the operating range.

Within this project, the possibilities and advantages of operating hydropower machines at varying rotating speeds will be investigated in three different fields:
1. Control of small hydropower plants by inverters
2. Small hydropower plants with two fixed speeds
3. Variospeed hydropower machines in pumped storage hydropower plants The project will answer the following main questions:
- Technical design
- Efficiency
- Operating limits of the hydropower machines
- Advantages in comparison with conventional concepts.

JOU2-CT93-0433 Description of the Research Project The major concern of the project is the application of variable speed controlled hydropower machines in two types of plants: small hydropower plants and pumped storage hydropower plants (PSHP).

A) Small hydropower plants : The results of the project will provide a contribution to the control of various types of hydro-turbines by solid state inverters. This solution is very promising, cost saving and reliable, as it has been experimentally tested in one case in a small hydraulic plant in Germany. In the specific case of a reservoir serving as flood pool with widely varying heads between summer and winter the control by two fixed speeds could be more efficient.

The main objectives are:
- to model the operating characteristics of hydraulic turbines at varying rotation speeds.
- to investigate the application range of inverter driven control to various types of hydraulic turbines using standardised electromechanical equipment.
- to compare the two-speed-design and the design with inverters.
B) Pumped Storage Hydropower Plant : The replacement of worn machines by variable-speed machines solves the problem of compliance with the fundamental new requirements made by the electricity grid which are nowadays placed on PSHP, i.e. power frequency control and operation of the machines in the partial load range. It also increases the storage efficiency level. The possibilities and limits of this solution are to be investigated in the project based on a specific example in the power range of 70 MW or more. Until now, variable-speed pumps and turbines have only been installed in the case of new plants where, in particular, the height of installation was freely selectable.

Funding Scheme

CSC - Cost-sharing contracts


Kruppstrasse 5
45128 Essen

Participants (6)

United Kingdom
11,Elvaston Place 11
SW7 5QG London
De Pretto Escher Wyss
Via Daniele Manin 16-18
36015 Schio Vicenza
Institut National Polytechnique de Grenoble
Domaine Universitaire
38402 Saint-martin-d'hères
National Technical University of Athens

15710 Athens
Société Electrique de l'Our SA

2010 Luxembourg
Technische Hochschule Darmstadt
Magdalenenstraße 4
64289 Darmstadt