Optimal Sizing of Converters for Hybridizing Conventional Pumped Storage Hydro with Floating PV Plants

Pumped storage hydro (PSH) now has an expanded portfolio including adjustable speed (AS) synchronous machines to provide pump-mode regulation. However, the application of this technology in the industry has been limited to two plants world-wide, mainly due to the capital investment required for large-scale inverters. Also, the fact that an AS-PSH plant is idle during most of the day discourages the application of such investments.

To encourage investors and industrial participants to investigate this option, a multi-use case has been developed by coupling floating photovoltaics (PVs) and AS-PSH. The presentation proposes that the use of the existing but converters of the AS-PSH system for hosting floating PV will increase the availability of the plant and thereby justify the capital investment. Synchronous machine-based AS-PSH have large converters which can be used to integrate floating PVs of equal capacity as an AS-PSH unit, given the availability of the large amount of unused reservoir surface area. The large number of existing conventional PSH (C-PSH) projects world-wide presents significant opportunities for this hybrid technology to be realized.

Converters required for the conversion of the C-PSH plant to the AS-PSH and to the hybrid AS-PSH + PV plant can be optimally sized, as will be presented. The problem is framed as a security constrained optimal scheduling problem that simultaneously reveals the optimal size of the required converters. Benefits of this conversion are examined from the point of view of operating cost, emissions, losses, voltage profile, curtailment and system congestion under different levels of renewable penetration.