FACTS-based Grid Interface with Embedded Energy Storage for Ocean Wave Power

This article presents the state-of-the-art application of a Unified Power Flow Controller (UPFC) to directly interface ocean wave energy converters (WEC) with the utility grid. It is shown that the transformer flux saturation problem at variable low-frequency operation poses no technical issue for the ocean power applications because a direct-proportionality relationship exists between frequency and amplitude of the WEC output voltages. We have proposed a direct interface of WEC with the utility grid using a series compensation transformer of the UPFC controller. The shunt input rectification segment of the UPFC acts not only as the DC bus for the UFPC operation but also as an embedded energy storage stage for the WEC. The mathematical formulation and simulation results are presented as a proof-of-concept for FACTS-based WEC-grid integration with the integrated energy storage capability.