A Hybrid Control Method for Output Power Smoothing of a PMSG-Based WECS

Abstract

This paper presents a smoothing method of output power by using pitch angle control, inertia of a wind turbine and DC-Link voltage control of a wind energy conversion system (WECS) using a permanent magnet synchronous generator (PMSG). The output power fluctuations in low and high frequency domains are smoothed by the pitch angle control of the WECS and the DC-Link voltage control, respectively. The remaining frequency, i.e., middle frequency is smoothed by the inertia of the wind turbine. The generator-side converter controls the generator torque of PMSG while the grid-side inverter controls the DC-Link voltage and grid voltage. From the proposed method, the generator torque is smoothed and kinetic energy generated by the inertia of the wind turbine is used to smooth the power fluctuations of the PMSG and wind turbine blade stress is mitigated as the pitch action in high frequency domain is reduced. Due to the DC-Link voltage in this paper by an appropriate operating region, the output power smoothing is achieved with stability and low cost. The effectiveness of the proposed method is validated by numerical simulations.