Non-flux observation doubly-fed induction generator low voltage ride-through control method and system

Abstract

The invention discloses a non-flux observation doubly-fed induction generator low voltage ride-through control method and a system, which can be applied to excitation control on a rotor-side converter of the doubly-fed induction generator in the case of deep power grid fault. The specific implementation method comprises steps: once deep fault is detected to happen to the power grid, rotor current of the doubly-fed induction generator is instantly controlled to directly track stator current at a certain ratio, and a certain compensation term related to stator voltage is injected to a rotor current instruction for providing dynamic reactive support. The invention also provides a control system structure diagram for realizing the above principle. Compared with de-excitation control, flux tracking and other low voltage ride-through excitation control methods, no flux observation step is needed for generating a transient control instruction, the structure is simple, multiple control objectives such as electromagnetic torque ripple suppression or dynamic reactive power compensation can be realized, and the low voltage ride-through ability of the doubly-fed induction generator is greatly enhanced.

Description

technical field [0001] The invention belongs to the technical field of double-fed wind turbines, and more specifically relates to a control method and system for low-voltage ride-through of double-fed wind turbines without flux linkage observation. Background technique [0002] With the increase of wind power penetration in the grid, low voltage ride-through capability has become an essential requirement for wind turbines to be connected to the grid. Provide reactive support. Among various models, doubly fed induction generator (DFIG) has become the main model due to its advantages of variable speed and constant frequency operation and small capacity of excitation converter, but its low voltage ride-through difficulty is much higher than that of other wind turbines. unit. This is because the rotor-side induced electromotive force (Electromotive force, EMF) will be much higher than the DC bus voltage when the power grid fails, and the rotor-side converter (Rotor-side conver...

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Problems solved by technology

However, these methods all require stator flux observations to generate transient control commands, and de-excitation control also requires phase sequence separation.

The flux linkage observation requires accurate motor parameters, and the drastic changes in voltage and current after a power grid fault will cause the resistance and inductance to deviate from their normal operating value; It will filter out the transient DC component in the stator current, both of which will affect the accuracy of flux linkage observation

Because the above schemes use the flux linkage observations to generate control instructions, observation errors will directly affect the effectiveness of these methods; and if some special schemes are used to improve the observation accuracy, the complexity of the system will be further increased

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