Energy-efficient dynamic drive control for wind power conversion with PMSG: Modeling and application of transfer function analysis

Abstract

A method for transfer function based modeling offering an in-depth insight into the systemic behavior of wind energy conversion systems (WECS) is developed. The originally nonlinear behavior of the drive system covering turbine, permanent magnet synchronous generator, and power electronic converter is rearranged and linearized resulting in a compact transfer function description. The locations of transfer function poles and zeros and related stability are readily identified as a function of WECS parameters and the operating point. Drive control design rules making use of the transfer functions for setting the compensation parameters depending on the wind speed are established. The behavioral differences between speed and power control loops can readily be appreciated. The synthesis of a power control loop to closely follow maximum available wind power is performed based on the design rules. In this context, the voltage sourced converter is operated in current mode control to contribute to fast adjustment of air-gap torque while maintaining currents within limits. The direct and quadrature current references are calculated to attain the desired torque at minimal stator current magnitude and so enhance energy efficiency. The dynamic performance of the design is evidenced by time-domain simulation and stochastic analysis.