Abstract
This paper proposes a coordinated derived current control strategy of doubly fed induction generator (DFIG) system under unbalanced grid voltage conditions. The rotor-side converter (RSC) and the grid-side converter (GSC) are synchronized to the grid with a virtual phase angle of nominal frequency, which can be simply set as $\theta =\omega _{\mathrm {n}}t$ ( $\omega _{\mathrm {n}}= 100\pi$ ). Consequently, the proposed control strategy can implement in an arbitrary reference frame without phase-locked loop (PLL). The derived d-q axis currents are obtained from the DFIG stator and GSC currents with virtual angle-based Park Transformations. For a simple implementation, a reduced-order vector integrator with a voltage vector multiplier is used to directly regulate the measured powers/currents containing both the dc part and the oscillating part without sequence extractions. By this means, RSC achieves torque ripple reduction and then GSC can rebalance the currents and smooth the active/reactive powers. Finally, the experimental results on a small laboratory setup are presented to validate the effectiveness of the proposed control strategy.
Highlights
In decades, the transport electrification, especially the electrified train and the electric vehicles, has attracted more extensive attention due to lower carbon emissions and higher energy-efficiency than the fossil fuel-powered trains and vehicles
doubly fed induction generator (DFIG) is driven by a squirrel-cage induction motor and the unbalanced grid is simulated by a Chroma programmable ac source 61704
It synchronizes to the grid through virtual phase angle produced by nominal frequency and implements in an arbitrary reference frame without phase-locked loop (PLL)
Summary
The transport electrification, especially the electrified train and the electric vehicles, has attracted more extensive attention due to lower carbon emissions and higher energy-efficiency than the fossil fuel-powered trains and vehicles. This paper presents a coordinated derived current control of RSC and GSC without PLL under unbalanced grid voltage conditions. It refers to a novel derived current control approach of the grid-connected DFIG in the virtual phase angle-oriented (dq) reference frame.
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