A wind turbine emulator that represents the dynamics of the wind turbine rotor and drive train

A wind turbine emulator (WTE) is an important equipment for developing wind energy conversion systems. It offers a controllable test environment that allows the evaluation and improvement of control schemes for electric generators what is hard to achieve with an actual wind turbine since the wind speed varies randomly. A WTE consists essentially of a torque controlled electric motor and a reference torque calculator. The latter usually reproduces only the average torque of the wind turbine. This paper presents an improved version that considers also the harmonic torques due to the gradient and tower shadow effects, inertia of the wind turbine and elasticity of the drive train. It is intended to be used for the analysis of remedial solutions for damping harmonic torques produced by the wind turbine and drive train resonances. Basic equations that represent the dynamic system are derived and used to implement the control scheme. A laboratory prototype was built with a permanent magnet de motor driven by either a three-phase thyristor rectifier or a pulse width modulated (PWM) dc-dc converter and a digital signal processing (DSP) system. The experimental results demonstrate the effectiveness of the reference torque calculator, identifies inherent limitations imposed by the phase-controlled thyristor rectifier and eliminates the problems using a dc-dc converter.