Abstract
This paper presents a vector current controller (in the synchronous reference, or the dq, frame) with negative-sequence current injection capability for three-phase grid-connected converters. This capability is desired for the operation of the converter during unbalanced conditions and also for a certain type of islanding detection. The proposed controller first determines the double-frequency current references and then uses a sixth-order two-input two-output proportional-integral-resonance (PIR) structure, which is optimally designed. Compared with the existing similar approaches, the proposed controller has a simpler structure and more robust performance, e.g., against system parameter uncertainties and weak grid conditions. The proposed controller is developed for converters with both the L-type and LCL-type filters. For the LCL-type converter, a suboptimal partial state feedback control is also proposed to achieve robust stability and active damping of resonance poles without requiring additional sensors. Detailed experimental results are presented to illustrate the properties and performances of the proposed controller.
Highlights
Grid-connected converters exchange positive-sequence balanced current with the grid during normal operation
During an asymmetrical grid fault, when the grid is unbalanced [1,2,3,4,5,6] or when they are equipped with an active islanding detection mechanism, which is based on injection of a small negative-sequence current [7,8]
This paper proposes a new controller for a voltage source converters (VSCs) based distributed energy resource (DER) unit with negative-sequence current injection capability
Summary
Citation: Karimi, H.; Haddadi, A.; Karimi-Ghartemani, M.; Sadabadi, M. Department of Electrical Engineering, Ploytechnique Montreal, Montreal, QC H3T 1J4, Canada Department of Automatic Control and Systems Engineering, University of Sheffield, Sheffield S1 3JD, UK;
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