Optimal operation of variable speed pumped storage hydropower plants participating in secondary regulation reserve markets

Pumped-storage hydropower is seen as a promising solution for efficient, large-scale energy storage. One competitive technical solution is the variable-speed hydropower plant (VSHP) configured with a converter-fed synchronous machine (CFSM). These machines are operated with one extra degree of freedom that is not usually optimized, where the CFSM's rotor-side DC excitation interacts with the stator-side AC excitation. Depending on machine loading, the CFSM will be utilized in conditions far from its original design. In order to deal with this issue, this paper presents a stator flux control (SFC) method for regulating VSHPs in a more efficient way by adjusting the field current to prevent the machine from operating with over-magnetization independent of loading condition, as well as better utilizing the stator-fed converter current, maximizing the utilization of the CFSM. The derived first-principle analytical equations for the proposed SFC have been validated and analyzed in the Matlab/Simulink environment for a large 45 MVA, 375 rpm CFSM, with the measured saturation curve as input. Finally, dynamic transitions between different levels of pumping power reveal the SFC's ability to help to maintain a unity stator flux in the machine, enabling optimal operation independent of loading level.

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Stator Flux-Regulatory Excitation Control in Converter-Fed Synchronous Machines for Pumped-Storage Variable-Speed Hydropower

10.36227/techrxiv.16746310 ◽

2021 ◽

Author(s):

Jørgen Hagset Stavnesli ◽

Jonas Kristiansen Nøland

Keyword(s):

Large Scale ◽

Optimal Operation ◽

Hydropower Plant ◽

Technical Solution ◽

Saturation Curve ◽

Variable Speed ◽

Original Design ◽

Machine Loading ◽

Stator Flux ◽

Pumped Storage

Pumped-storage hydropower is seen as a promising solution for efficient, large-scale energy storage. One competitive technical solution is the variable-speed hydropower plant (VSHP) configured with a converter-fed synchronous machine (CFSM). These machines are operated with one extra degree of freedom that is not usually optimized, where the CFSM's rotor-side DC excitation interacts with the stator-side AC excitation. Depending on machine loading, the CFSM will be utilized in conditions far from its original design. In order to deal with this issue, this paper presents a stator flux control (SFC) method for regulating VSHPs in a more efficient way by adjusting the field current to prevent the machine from operating with over-magnetization independent of loading condition, as well as better utilizing the stator-fed converter current, maximizing the utilization of the CFSM. The derived first-principle analytical equations for the proposed SFC have been validated and analyzed in the Matlab/Simulink environment for a large 45 MVA, 375 rpm CFSM, with the measured saturation curve as input. Finally, dynamic transitions between different levels of pumping power reveal the SFC's ability to help to maintain a unity stator flux in the machine, enabling optimal operation independent of loading level.

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Stochastic Security Constrained Unit Commitment with variable-speed pumped-storage Hydropower Plants

2016 Power Systems Computation Conference (PSCC) ◽

10.1109/pscc.2016.7540845 ◽

2016 ◽

Cited By ~ 8

Author(s):

Omid Alizadeh-Mousavi ◽

Mostafa Nick

Keyword(s):

Unit Commitment ◽

Variable Speed ◽

Hydropower Plants ◽

Pumped Storage

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Small Hydropower Plants with Variable Speed Operation—An Optimal Operation Curve Determination

Energies ◽

10.3390/en13236230 ◽

2020 ◽

Vol 13 (23) ◽

pp. 6230

Author(s):

Dariusz Borkowski ◽

Marek Majdak

Keyword(s):

Energy Production ◽

Control Point ◽

Analytical Formula ◽

Optimal Operation ◽

Point Of View ◽

Variable Speed ◽

Small Hydropower ◽

Control Techniques ◽

Hydropower Plants ◽

Water Turbine

In recent times, much attention has been paid to small hydropower plants (SHPs) with variable speed operation and different control techniques. Control complexity in SHPs is mainly caused by specific steady-state features of the water turbine, the long time constants of the hydraulic system and significant seasonal and/or aging-related deterioration in the system performance. This paper presents the most important features of the turbine model from a control point of view. It classifies control techniques for SHPs with variable speed operation in terms of the turbine type and SHP function (run-of-the-river and reservoir). Furthermore, various control methods are analysed taking into account the complexity of the method, dynamics, adaptability and applicability. The novelty of this study is the proposal of a simple, universal analytical formula, which, based on the basic dimensions of the turbine, determines the optimal operating curve. The proposed formula is verified on a real SHP 150 kW by comparison with measurements in the form of operational characteristics. The analysis of the annual energy production confirms the effectiveness of the approximation precision, yielding only 1% production losses, and shows an advantage of variable speed over constant speed in annual energy production of 16%.

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