Abstract
This paper aims to explore a viable solution for a doubly-fed induction generator (DFIG)-based wind farm to meet the reactive support requirement of the low voltage ride-through (LVRT) grid code with safe grid-connected operation during asymmetrical grid faults. First, the control scheme for the DFIG-based wind energy conversion system (WECS) is designed. Then, the controllability issue is analyzed by means of an optimal method, and the derived controllable regions indicate that the DFIG-based WECS can only remain controllable under mild asymmetrical fault situations. Afterwards, the static synchronous compensator (STATCOM) is introduced as extra equipment to ensure that the DFIG-based wind farm remains controllable under severe asymmetrical fault situations. For this purpose, a voltage compensation control scheme and a corresponding capacity matching method for the STATCOM are proposed. The simulation results verify that, with the proposed coordinated control between the DFIG-based wind farm and the STATCOM, the required positive-sequence reactive current can be supplied to support the power grid. The oscillations on the electromagnetic torque and direct current (DC)-link voltage of the DFIG-based WECS can also be eliminated. Therefore, the control scheme can be helpful to improve the reliability of both the wind farm and the power system during grid faults.
Highlights
With the increasing penetration of wind power energy in the power system, the capability of low voltage ride-through (LVRT) is becoming a requirement for grid-connected wind farms in the grid codes of more countries to ensure the reliable operation of the power system during grid faults [1,2,3]
After solving the optimization problem, the controllable regions represented by the unbalanced degree of grid voltage are given. These results indicate that a doubly-fed induction generator (DFIG)-based wind energy conversion system (WECS) can only achieve its control objectives under mild asymmetrical fault situations
This paper has discussed the coordinated control of a DFIG-based wind farm and a STATCOM for LVRT grid code compliance during asymmetrical grid faults
Summary
With the increasing penetration of wind power energy in the power system, the capability of low voltage ride-through (LVRT) is becoming a requirement for grid-connected wind farms in the grid codes of more countries to ensure the reliable operation of the power system during grid faults [1,2,3]. The effects of the control schemes in the second LVRT period are limited by the converter capacity of the DFIG-based WECS when the grid fault is severe. For the second period of an asymmetrical LVRT, there is a need for a viable solution for the DFIG-based wind farm to meet the reactive support requirement of the LVRT grid code with safe grid-connected operation. After solving the optimization problem, the controllable regions represented by the unbalanced degree of grid voltage are given These results indicate that a DFIG-based WECS can only achieve its control objectives under mild asymmetrical fault situations.
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