Full operational regimes for SPMSG-based WECS using generation of active current references

Abstract

The intermittency of wind speed poses challenges to obtaining reliable power and integrating wind plants successfully with existing power infrastructure. Fast and efficient controls are required to cater to the transient nature of wind speed and simplify wind power control. This paper presents an efficient control mechanism for operating a wind energy conversion system (WECS) over its full operating range by incorporating a surface-mounted permanent magnet synchronous generator (SPMSG) to generate suitable active current references based on generator voltage and achieve the maximum power output from a wind turbine. In the partial-load state, the control scheme operates based on field-oriented control with a maximum power point tracking controller to maximize the energy harvested from the wind. In the full-load operating regime, the control swings towards maximum electrical torque by invoking a feedback-based flux-weakening strategy with voltage and current constraints. Furthermore, a nonlinear pitch angle controller is employed to ensure normal operation at high wind speeds. The proposed scheme is intended for a variable-speed variable-pitch WECS based on a direct-drive SPMSG for both underrated and overrated wind speeds, and can be connected to the utility grid. The validity and effectiveness of the proposed scheme are verified through numerical simulations performed on a 2.41 MW WECS. The results confirm the scheme’s ability to cope with WECS dynamics within safe operating limits.