Community Research and Development Information Service - CORDIS

Periodic Report Summary 2 - HYPERBOLE (HYdropower plants PERformance and flexiBle Operation towards Lean integration of new renewable Energies)

Project Context and Objectives:
Project context.
The 20-20-20 strategic energy policy decided by the European Union and its accompanying Renewable Energy Directive is leading toward a dramatic electric energy system transition. The two major pillars of this transition are:
i) a massive penetration of alternative renewable energies and
ii) a broad deployment of energy efficiency initiatives and technologies.
In this context, hydropower already plays a crucial role and will increasingly do so. On one hand by contributing to renewable energy production and, on the other, by fulfilling the highly dynamic energy storage requirements to enable a widely distributed injection of PV and wind energy into the transmission and distribution systems, while preserving their stability through the provision of advanced system services.
To achieve a lean integration of new renewable energy sources, NRE, within the power network, the TSO, Transmission System Operator, needs to be able to perform a fast energy balance between generation and consumption. Therefore, in order to enable this energy balancing process, it is necessary to ensure that power stations have enough storage capacity as well as primary and secondary grid control capability. Hydropower stations feature such a capacity of flexible generation for peak power and regulation ancillary services at a large scale, while offering the advantage of exploiting a renewable primary source of energy with almost no emission of greenhouse gas.
Additionally, pumped storage power stations provide a system to store large amounts of electricity with a full cycle of pumping and generation, which can achieve unrivalled efficiencies of at least 80%.
Main objectives
To take up the challenge of enhancing the capability of hydropower stations to be operated over a larger operating range and with a faster time demand response, the HYPERBOLE Research Consortium partners have defined the 3 following scientific and technological objectives to be achieved.
The first objective is to bring new knowledge of the root causes of the operating range limitations for both hydraulic turbines and pump-turbines to be operated over a wide operating range. When operated at these off-design conditions, corresponding to deep part load, below 30 % of rated power and up to overload operation, about 110 % of rated power, hydraulic turbines and pump-turbines may experience critical instabilities with high levels of vibration and large pressure and power fluctuations.
The second objective is to develop comprehensive multi-component models of the hydropower station dynamics based on and validated by reduced-scale physical model measurements as well as extensive field tests. These models are then implemented for every operating condition case in SIMSEN, the tool for advanced numerical simulation of systems dynamics developed by EPFL. It is widely used by the industrial partners of the consortium, for simulating the hydropower stations dynamics, including hydraulic machinery and system, electrical machines and power electronics and the control systems. Advanced dynamic models of the electrical machine and power electronics system need to be developed as well.
The third objective aims to demonstrate the benefits hydropower stations can provide to safely integrate NRE, based on real selected case studies. The enhancement of the operating range of Francis turbines and pump-turbines, as well as the capability of providing inertia emulation functionalities and primary and secondary control capabilities, together with new control strategies, will contribute to increase the penetration of NRE in power networks. As a result, the additional NRE connection capacity will be evaluated in a study case with respect to system stability, using state of the art power network simulation models.

Project Results:
In WP1, the second experimental campaign has been completed by investigating hydro-mechanical behaviour of the runner. A special solid runner has been manufactured and instrumented with pressure sensors and strain gauges. The range of operating conditions investigated spans from full load to deep part load.
A set of guide vanes has been developed to enable visualisation of cavitation inter-blades vortices corresponding to deep part load operation. These visualisations evidence an excellent correspondence with the results of the flow numerical simulations for the corresponding operating point
All the scheduled flow numerical investigations have been performed for both Francis turbine and reversible pump-turbine test cases. Simulations results are found to be in agreement with the experimental results, see for instance the comparisons of pressure values in the case of the transient mode change for the pump-turbine case.
In WP2, FEM simulations of the runner structural dynamics for the Francis turbine test case is delayed because of the delay of the flow numerical simulations scheduled in WP1. However, the mesh of the runner has been performed. The stress measurements performed during the hydro-mechanical tests of WP1 have been processed and analysed to enable the comparison with the further FEM simulations.
In WP3, pump-turbine test case is tested in transient operating conditions over the so-called 4 quadrants operating range. Fast mode changes, cycle of 8 s, between pumping, generating and, back, to pumping modes were investigated. Improved electrical model has been developed and implemented in SIMSEN software for the analysis of Francis turbine test case at part load and full load. Moreover, SIMSEN model of a Pumped Storage Power Plant is now available for fixed speed (synchronous machine) and variable speed, declined in both technologies Doubly Fed Induction Machines (DFIM) and Full Size Frequency Converter (FSFC).
In WP4, hydro-acoustics parameters have been further investigated. In particular, the mass flow gain factor (MFGF), representing the mass excitation source expressed as the rate of change of the cavitation volume as a function of the discharge, was modelled using a quasi-static method to estimate the mass flow gain factor in the draft tube. The methodology is based on an experimental identification of the natural frequency of the test rig hydraulic system for different values of Thoma number.
Full load for the Francis turbine test case was investigated with both experimental identification and numerical flow simulation. The experimental results of WP1 have been extensively analysed for the full operating range from full load to deep-part load.
The hydro-acoustic parameters corresponding to theses operating conditions have been transposed for developing a SIMSEN model of MICA Unit 2.
In WP5, instrumentation for the online monitoring of the 444 MW Francis generating unit corresponding to the reduced scale model investigated in WP1 and WP2 was achieved in October 2015. The analysis of the monitoring data is in progress and already enables to evidence cavitation vortex rope signature. Modal analysis of Unit 2 structure has been performed as well.
In WP6, comparison between detailed and reduced hydropower plant models has been achieved. Identification and development of reduced order dynamic simulation models for Pumped Storage Power (PSP) plants have been performed, regarding both pump and turbine operating modes, relying on the outputs that can be obtained from detailed simulations performed in SIMSEN.
Investigations of participation of reversible hydropower plants in electric power markets have started. These are based on an optimization problem for optimizing a complete bidding strategy for a PSP unit. It combines the benefits of price arbitrage (i.e. pump in low price periods and generate in high price periods) with the participation in the ancillary services market, more specifically by providing Frequency Restoration Reserve (FRR). The overall bidding strategy framework for the participation of a PSP unit in the day-ahead and frequency restoration reserve markets is divided into three main modules, i.e. i) Medium-term Optimization, ii) Short-term Optimization and iii) Evaluation Module.

Potential Impact:
NRE Development in Europe
European Union agenda to generate 20% of electricity from so called NRE, New Renewable Energy sources, by 2020 relies on a tremendous capacity increase of both wind and photovoltaic power stations. However, the intermittent nature and uneven localization of the NRE power stations are source of disturbances for the grid stability which may limit further development of NRE. This may be solved by extending the operating range of hydropower stations which provides frequency regulation capabilities as well as secondary reserves for the electrical power system. The technical capacity of extending the operating range of European hydropower station is a direct impact of the HYPERBOLE Project.
Existing economic studies of hydropower projects are mainly focused on evaluating the value of price difference between peak and valley operation, and the value of the provision of tertiary reserve, as it is already provided by the conventional on-off operation of hydropower units. If the important role of variable-speed pumped storage power stations is to be developed, their integration in the present economic system needs to be investigated. The HYPERBOLE project will provide a first economic study on how the profitability of variable-speed pumped storage power stations can be assured, taking into account their role in the provision of secondary reserve to the grid and in the primary frequency regulation.

European Hydro Equipment Industry
The installation of new capacity and the refurbishment of existing power stations in the course of the development of renewable energy sources and their integration into the grid hold a substantial business potential for the three main hydro equipment suppliers of the HYPERBOLE consortium, namely ALSTOM, ANDRITZ and VOITH. They presently hold over 50% of the global market share in hydroelectric equipment, which makes the European industry a world class key player in the future of hydropower.
An estimated capacity of 1’000 GW is to be installed until the year 2050, mainly in Africa, Asia and South America, representing a massive potential contract volume for the European players. It goes without saying that in this highly competitive area an important and continuous R&D effort is necessary to keep an advantage over the extra European competitors in the installation and refurbishing of hydropower stations.
Modernization of existing hydropower stations is usually an economically and technically interesting option. From the presented numbers it can be estimated that a total capacity of 1’000 GW is to be refurbished over the next decades, adding up to the potential business cases of the hydro equipment suppliers participating in the HYPERBOLE consortium.

Science and Technology
The large number of numerical and experimental investigations scheduled in the participating universities and research institutes generates a significant academic output on different levels. The scientific and technical publications in the fields related to the HYPERBOLE project will consolidate the leading position of European research institutions. In addition, the formation of PhD students is a key function of the involved educational institutions. This ensures at the same time a continuous supply of highly trained specialists needed in the industry.
The results of the project will be integrated in the SIMSEN software for the multi component modelling of hydropower station dynamics; yielding a powerful tool for a holistic analysis of the interaction of a hydropower station with the connected power system. The enhanced SIMSEN software will set a new advanced industry standard as a reference in the field.
An important result of the HYPERBOLE project is a detailed knowledge of the dynamic loads experienced by the hydro-electrical equipment. This knowledge contributes to the development of more resistant and longer living components, as well as to the development of resistant material, i.e. for use with sea-water.

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