Analysis and efficient control design for generator-side converters of PMSG-based wind and tidal stream turbines

Mitigation of climate change has stimulated an increased penetration of renewable generation into electricity grids. A substantial amount of the future energy mix is projected to come from renewable sources such as offshore wind, but marine energy may be an important contributor due to the great potential of wave and tidal stream generation. Wind and tidal stream turbines feature similarities: electric machines used, system configuration and control schemes-aiming to extract maximum power from the wind or flow. In this line, individual channel analysis and design (ICAD), a frequency domain framework with the help of which the investigation of the potential and limitations for control design of multivariable systems can be assessed, is employed for turbines based on permanent magnet synchronous generators. Through ICAD, a formal evaluation of the internal coupling of the turbine generator is performed. Results offer formal insight into control strategies based on vector control — with emphasis made on the generator-side of the full power converter. The analysis shows that the use of decoupling loops is not necessary to ensure a satisfactory performance. This is further examined through a simulation carried out in MATLAB/Simulink, showing the effectiveness of the approach.