A New Simulation and Control Model for a Variable Speed Variable Pitch Direct Drive Large Offshore Wind Turbine Generator With Integrated Energy Storage

Abstract

A comprehensive control and simulation model has been presented in this paper for a large multi-megawatt Variable Speed Variable Pitch Wind Turbine Generator (WTG) with Energy Storage System (ESS) integration. The generator is of a Permanent Magnet Synchronous Generator (PMSG) type which is then decoupled from the grid using a Fully-Rated back-to-back Converter (FRC) link. A Rotor Flux Oriented Control (RFOC) strategy has been adopted in order to extract the maximum output electromagnetic torque from the generator according to a Maximum Power Point Tracking (MPPT) profile for any wind speed lower than rated wind speed. The MPPT method presented in this paper relies on the turbine’s optimal output torque curve. The ESS makes provisions for enhanced performance especially during faults on the system. Dynamic performance of a super-capacitor makes it ideal as the integrated ESS in the WTG for satisfying such performance constraints. Results indicate that the WTG integrated with a super-capacitor ESS provides the required enhanced performance in terms of DC link voltage stability and limiting output power fluctuations during sudden variations in the wind speed as well as enhanced Fault Ride-Through (FRT) capability.