Abstract
A doubly-fed induction generator(DFIG) based configuration is still preferred by wind turbine manufacturers due to the cost-effective power converter and independent control of the active power and reactive power. To cope with stricter grid codes(e.g. reactive power compensation, low voltage ride-through operation, as well as steady and safe operation during long-term distorted grid), control strategies are continuously evolving. This paper starts with a control strategy using the combined reactive power compensation from both the back-to-back power converters for their optimized lifetime distribution under normal grid conditions. Afterwards, an advanced demagnetizing control is proposed to keep the minimum thermal stress of the rotor-side converter in the case of the short-term grid fault. A modularized control strategy of the DFIG system under unbalanced and distorted grid voltage is discussed, with the control targets of the smooth active and reactive power or the balanced and sinusoidal current of the rotor-side converter and the grid-side converter. Finally, a bandwidth based repetitive controller is evaluated to improve the DFIG system's robustness against grid frequency deviation.
Highlights
A recent study by the Danish Energy Agency indicates that onshore wind power is the cheapest form of new electricity generation in Denmark[1]
To cope with the modern grid codes, this paper introduces a series of control strategies in cases of normal grid condition, short-term grid fault and longterm distorted grid
In order to remove the harmonic components of the stator current under generalized harmonic voltage, the repetitive control (RC) regulator can be adopted due to its advantage of controlling the multiple times of harmonic sequence at the same time
Summary
A recent study by the Danish Energy Agency indicates that onshore wind power is the cheapest form of new electricity generation in Denmark[1]. As one of the most vulnerable components of the wind turbine system, much effort has been devoted to the reliable behavior of the power electronic converter because of the increased cost and time for offshore maintenance[3]. A doubly-fed induction generator(DFIG) structure is still the most used concept by wind turbine manufacturers due to the cost-effective power converter and the independent control of the active power and reactive power[6,7,8]. In the case of short-term grid fault, hardware and software solutions of the DFIG system are addressed, and an advanced demagnetizing control is proposed to minimize thermal stress of the rotor-side converter.
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