This paper presents an output power smoothing method by a simple coordinated control of DC-link voltage and pitch angle of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG). The WECS adopts an AC-DC-AC converter system with voltage-source converters (VSC). The DC-link voltage command is determined according to output power fluctuations of the PMSG. The output power fluctuationsin low-and high-frequency domains are smoothed by the pitch angle control of the WECS, and the DClink voltage control, respectively. By using the proposed method, the wind turbine blade stress is mitigated as the pitch action in high-frequency domain is reduced. In addition, the DC-link capacitor size is reduced without the charge/discharge action in lowfrequency domain. A chopper circuit is used in the DC-link circuit for stable operation of the WECS under-line fault. Effectiveness of the proposed method is verified by the numerical simulations.Index Terms-Permanent magnet synchronous generator, pitch control, power smoothing, wind energy conversion system.

With the increasing trend of connecting high penetrations of wind energy conversion systems (WECSs) to the transmission networks comes the challenge of updating the grid code for the connection of megawatt-class wind turbines. Starting with each WECS entity in the wind farm, the specifications would require the ability to complement some of the power system control services-voltage and frequency control-currently carried out by conventional synchronous generation. This paper investigates output power stability of a WECS in a highly fluctuating wind environment. Based on a performability model, a control strategy is devised for maximizing energy conversion in low to medium winds, and maintaining rated output in above rated winds while keeping torsional torque fluctuations to a minimum. Control is exercised via collective blade pitch control as well as generator torque control. The fundamental philosophy behind the proposed control strategy for the wind turbine coupled to an asynchronous doubly fed induction generator is general and can be easily extended to other WECS configurations.Index Terms-Aerodynamic conversion, blade pitch regulation, doubly fed induction generator (DFIG), drive-train torsional torque, linear quadratic Gaussian (LQG), modeling, wind energy conversion system (WECS).

No abstract

No abstract

No abstract