Control method of double-fed induction generator under power grid voltage three-phase symmetrical drop fault

Abstract

The invention belongs to the field of control of power conversion devices of wind driven generators and relates to a control method of a double-fed induction generator (DFIG) under a power grid voltage three-phase symmetrical drop fault. The control method comprises the following steps of: calculating a stator voltage, a stator current and a rotor current under a two-phase static coordinate system; calculating the magnetic flux linkage as well as stator voltages and stator currents of a shaft d and a shaft q under synchronous rotation coordinates; calculating a slip frequency angle and a slip frequency angle velocity; calculating stator currents of the shaft d and the shaft q under the rotation coordinates; calculating active power, reactive power and electromagnetic torque of a stator; calculating a decoupling compensation voltage of a rotor; obtaining a primary component actual value of the rotor current after the rotor currents of the shaft d and the shaft q under the rotation coordinates pass through a band-pass filter and a lead lag link on the basis of a compensation target, obtaining a difference of the primary component actual value and a primary component set value and calculating through a PI (Proportional-Integral) controller to obtain a primary component compensation item; calculating a set value of the current of the rotor shaft d under the rotation coordinate system; obtaining a difference of a rotation speed set value and a rotation angular rotation speed actual value and calculating through the PI to obtain a set value of the current of the rotor shaft q under the rotation coordinate system; calculating to obtain a reference value of the rotor voltages of the shaft d and the shaft q under the rotation coordinate system; and calculating the rotor voltage under the two-phase static coordinate system and generating a switch signal for controlling a power device.

Description

technical field [0001] The invention relates to a control method for a rotor-side inverter of a doubly-fed wind power generator (DFIG) under a grid voltage three-phase symmetrical drop fault, and belongs to the field of wind power generator control. Background technique [0002] The variable-speed wind turbine based on the doubly-fed induction generator (DFIG) has become the mainstream model in the world wind power market due to its high energy conversion efficiency and independent adjustment of active and reactive power. The stator side of DFIG is directly connected to the grid and is very sensitive to grid faults. The three-phase symmetrical drop of the grid voltage will cause a sudden change in the stator voltage of the generator, and the stator current will oscillate. At the same time, the active and reactive power and electromagnetic torque of the generator stator will also oscillate. In addition, due to the strong coupling between the rotor and the stator, the abrupt ...

AI Technical Summary

Problems solved by technology

This method protects the excitation converter and the rotor winding when the power grid fails, but at this time the generator runs in the induction motor mode and needs to absorb a large amount of reactive power from the power grid, which will further deteriorate the power grid; second, the protection circuit The switching operation will have a transient impact on the system; in addition, adding a new protection device increases the system cost

Some scholars have introduced a new topology structure. The control of this scheme is complex, and because the scheme operates off-grid when the power transmission system fails, it does not actively support the restoration of normal operation of the power grid; similarly, this scheme needs to increase the cost of the system

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