Digital current-control schemes

IEEE Industrial Electronics Magazine (Impact Factor: 5.06). 04/2009; DOI: 10.1109/MIE.2009.931894
Source: IEEE Xplore

ABSTRACT The paper is about comparing the performance of digital signal processor-based current controllers for three-phase active power filters.

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    ABSTRACT: Instead of extracting every selected harmonic component, the current reference of selective active power filter (APF) can be also obtained by filtering out the fundamental component from distorted load current for computation efficiency. This type of mixed current reference contains kinds of harmonic components and easily involves noises. In this condition, selective harmonic compensation must be realized by the current controller. With regard that selectivity is the most significant feature of controller, this paper presents specific comparison analysis between two types of resonant controllers: proportional-resonant (PR) controller and vector-resonant (VR) controller. The comparison analysis covers the relations, performances, and stability of both controllers. Analysis results conclude that the poorer selectivity of the PR controller could be relatively improved, but limitations from system stability make the improvement hardly realized. By contrast, the VR controller exhibits excellent selectivity and is more suitable for selective APF with mixed current reference. Experimental results from laboratory prototype validate the reasonability of analysis. And the features of each resonant controller are concluded.
    Journal of power electronics 09/2013; 13(5). DOI:10.6113/JPE.2013.13.5.861 · 0.75 Impact Factor
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    ABSTRACT: Low-order odd current harmonics arise in practical multiphase drives due to machine and converter nonlinear behavior (e.g., deadtime and flux saturation). If the windings are distributed, some harmonics cause torque ripple, while others produce losses. The latter is aggravated by the small impedance in the no-torque subspaces. Current harmonics can be compensated without steady-state error by proportional-integral controllers in multiple synchronous frames (SFs); however, a heavy computational load is required. In three-phase systems, the computational burden of this multiple SF (MSF) scheme is often avoided by implementing instead resonant controllers (RCs) tuned at the harmonics that are multiples of six in an SF rotating with the fundamental frequency. A similar structure has been proposed for nonlinearities compensation in asymmetrical six-phase machines. This paper extends this multiple RC (MRC) strategy to symmetrical machines of any phase number. The optimum frequencies for the RCs and for the SF in each plane, so that the number of RCs is minimized, are established. Then, the computational load of the resulting generic MRC scheme is assessed and compared with that of the MSF structure. The conditions in which the former is particularly preferable over the latter are identified. Experimental results are provided.
    IEEE Transactions on Industrial Electronics 12/2015; DOI:10.1109/TIE.2014.2365155 · 6.50 Impact Factor
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    ABSTRACT: Repetitive control (RC), which can achieve zero steady-state error tracking of any periodic signal with known integer period, offers active power filters (APFs) a promising accurate current control scheme to compensate the harmonic distortion caused by nonlinear loads. However, classical RC cannot exactly compensate periodic signals of variable frequency and would lead to significant performance degradation of APFs. In this paper, a fractional-order RC (FORC) strategy at a fixed sampling rate is proposed to deal with any periodic signal of variable frequency, where a Lagrange-interpolation-based fractional delay (FD) filter is used to approximate the factional delay items. The synthesis and analysis of FORC systems are also presented. The proposed FORC offers fast online tuning of the FD and the fast update of the coefficients, and then provides APFs with a simple but very accurate real-time frequency-adaptive control solution to the elimination of harmonic distortions under grid frequency variations. A case study on a single-phase shunt APF is conducted. Experimental results are provided to demonstrate the validity of the proposed FORC.
    IEEE Transactions on Industrial Electronics 03/2015; 62(3):1659-1668. DOI:10.1109/TIE.2014.2363442 · 6.50 Impact Factor