A novel frequency control strategy for large scale marine current turbines based on Doubly Fed Induction Generator

This paper presents a novel frequency control strategy for Marine Current Turbines (MCTs) based Doubly-Fed Induction Generator. The proposed control strategy relies on the regular and highly predictable power extraction from the marine currents, which are essentially governed by astronomical forces. Therefore, the precise mathematical model for prediction of marine current speed is developed and validated with the recorded measurements at the specific location (Pentland Firth, Scotland). Additionally, the ancillary services of frequency control and inertial response have been deployed with large-scale implementation of MCTs to improve the dispatchability and compliance with grid code requirement. The main objective of the proposed control strategy is twofold: 1) achieve the primary frequency response and 2) mitigate power imbalances. This novel frequency management scheme is based on the combination of inertial response and a deloaded margin of 10%. The presented techniques are verified using a test power system at varying load levels and different marine speeds. The simulation results demonstrate the capability of the proposed frequency control strategy in satisfying the aforementioned objectives and improving frequency regulation and transient response.