Doubly-fed wind generator stator and rotor magnetic linkage synchronous flux-weakening control method under power grid failure

Abstract

The invention discloses a doubly-fed wind generator stator and rotor magnetic linkage synchronous flux-weakening control method under power grid failure. When the voltage of the power grid has faults, the high-control-frequency stator and rotor magnetic linkage synchronous flux-weakening control method is adopted by a doubly-fed wind generator rotor side converter. All of the variables of the control method are on the basis of a two-phase synchronous rotating coordinate, when faults occur, a rotor magnetic linkage can be adjusted through the control of the rotor side converter, the synchronous control of the rotor magnetic linkage and a stator magnetic linkage can be realized, the fault impact of the stator magnetic linkage to the rotor magnetic linkage can be weakened, and the rotor fault overcurrent can be reduced. The method can control the rotor fault current be 1.5-1.6 times of the rated current, reduces the electromagnetic torque ripple during the failure, the impact to a set during the failure, and the active power and reactive power fluctuation of the stator side, and can effectively improve the fault ride-through capability of the doubly-fed wind generator under power grid voltage failure.

Description

technical field [0001] The invention belongs to the technical field of doubly-fed wind power generator control, and in particular relates to a method for synchronous flux-weakening control of the stator-rotor flux linkage of a doubly-fed wind power generator under a grid voltage drop fault, which ensures that the grid does not run off-grid during a fault. Background technique [0002] As an inexhaustible, inexhaustible and non-polluting renewable energy in nature, wind energy is one of the best ways to solve the energy crisis by effectively utilizing it. In wind power generation technology, doubly-fed wind turbines can operate at variable speed and constant frequency, realizing the flexible connection between the unit and the power grid, and relieving the mechanical stress on the shafting of the unit to a certain extent. The stator winding of the double-fed wind turbine is connected to the power grid, and the rotor winding is supplied with three-phase excitation current by a...

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Problems solved by technology

[0003]When the power grid fails, the rotor short circuit protection is mainly used to maintain the uninterrupted operation of the doubly-fed wind power generation system, and the energy is released through the rotor bypass protection resistor to reduce the Rotor overcurrent, this method increases the hardware cost, the motor operates as an induction motor when a fault occurs, absorbs a large amount of reactive power from the grid, affects the stability of the grid, and is very harmful to the transient electromagnetic impact on the grid and the mechanical impact of the wind turbine. serious

At present, some literatures have reported the modeling and control research of doubly-fed wind turbine excitation frequency converter under grid fault conditions. Most of the main modeling methods are based on instantaneous power theory, and most of the control methods are positive and negative sequence double d q Vector control, this method can achieve a variety of optional control objectives in asymmetric fault ride-through, but the double PI closed-loop control greatly affects the dynamic performance of the control system, and the separation and control of positive and negative sequence power make the system The control structure is more complex, and more seriously, the time delay required for phase sequence separation reduces the response speed to grid faults. There is a danger of high voltage and high current damage at the moment of faults, and a small stator voltage imbalance will cause Large stator current unbalance and fluctuations in electromagnetic torque, active power and reactive power degrade the operation performance of the doubly-fed wind turbine generator. At present, most of the control methods are difficult to control the rotor current value within 2 times of its rated current during the fault period, and the electromagnetic torque fluctuation is relatively large, which has a great impact on the unit.

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