Method for controlling double-fed wind driven generator in power grid faults

Abstract

The invention belongs to the field of controlling a wind driven generator power conversion device and relates to a method for controlling a double-fed wind driven generator in power grid faults. The method comprises the following steps of: calculating a rotation angular velocity, calculating a stator voltage, a stator current and a rotor current under two-phase static coordinates, calculating a stator magnetic flux linkage and calculating d, q shaft stators voltage and stators current under synchronous rotational coordinates, calculating a slip-frequency angle and a slip-frequency angular velocity, calculating d, q shaft stators current under rotational coordinates, calculating a stator reactive power, calculating a rotor decoupling compensatory voltage, acquiring the actual values of a double frequency component and a triple frequency component of the rotor current after guiding the d, q shaft rotors current under rotational coordinates to flow by two band-pass filters and advanced delaying rings, acquiring the compensatory items of the double frequency component and the triple frequency component by two PI controllers after subtracting the actual values from the preset values of the double frequency component and the triple frequency component, summing the two compensatory items, acquiring a preset value of the rotor q shaft current under rotational coordinates and the reference values of d, q shaft rotors voltages under rotational coordinates by calculating with the PI controller after subtracting a preset value of the rotate speed from the actual value of the rotation angular velocity, calculating a rotor voltage under the two-phase static coordinates, and generating a switching signal for controlling a power device. The invention can efficiently prevent DFIG rotor current oscillation caused by the power grid fault, realize the on-line running of the wind driven generator and promote the running performance of the DFIG in power grid faults.

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 failure, 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. Power grid faults will cause sudden changes 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 stator voltage will cause large fluctuations in the rotor current, whic...

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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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