Control Strategy for a Grid-Connected Inverter under Unbalanced Network Conditions—A Disturbance Observer-Based Decoupled Current Approach

Emre Ozsoy, Sanjeevikumar Padmanaban, Lucian Mihet-Popa, Viliam Fedák, Fiaz Ahmad, Rasool Akhtar and Asif Sabanovic
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Emre Ozsoy: Department of Electrical and Electronics Engineering, University of Johannesburg, Auckland Park 2006, South Africa
Sanjeevikumar Padmanaban: Department of Electrical and Electronics Engineering, University of Johannesburg, Auckland Park 2006, South Africa
Lucian Mihet-Popa: Faculty of Engineering, Østfold University College, Kobberslagerstredet 5, 1671 Krakeroy-Fredrikstad, Norway
Viliam Fedák: Department of Electrical Engineering & Mechatronics, Technical University of Kosice, Rampová 1731/7, 040 01 Košice, Džung’a-Džung’a, Slovakia
Fiaz Ahmad: Mechatronics Engineering, Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul 34956, Turkey
Rasool Akhtar: Mechatronics Engineering, Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul 34956, Turkey
Asif Sabanovic: Mechatronics Engineering, Faculty of Engineering and Natural Sciences, Sabancı University, Istanbul 34956, Turkey

Energies, 2017, vol. 10, issue 7, 1-17

Abstract: This paper proposes a new approach on the novel current control strategy for grid-tied voltage-source inverters (VSIs) with circumstances of asymmetrical voltage conditions. A standard grid-connected inverter (GCI) allows the degree of freedom to integrate the renewable energy system to enhance the penetration of total utility power. However, restrictive grid codes require that renewable sources connected to the grid must support stability of the grid under grid faults. Conventional synchronously rotating frame dq current controllers are insufficient under grid faults due to the low bandwidth of proportional-integral (PI) controllers. Hence, this work proposes a proportional current controller with a first-order low-pass filter disturbance observer (DOb). The proposed controller establishes independent control on positive, as well as negative, sequence current components under asymmetrical grid voltage conditions. The approach is independent of parametric component values, as it estimates nonlinear feed-forward terms with the low-pass filter DOb. A numerical simulation model of the overall power system was implemented in a MATLAB/Simulink (2014B, MathWorks, Natick, MA, USA). Further, particular results show that double-frequency active power oscillations are suppressed by injecting appropriate negative-sequence currents. Moreover, a set of simulation results provided in the article matches the developed theoretical background for its feasibility.

Keywords: power control; power electronics; pulse width modulation inverters; disturbance observer; grid connected system; grid stability; distorted voltage (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2017
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (8)

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