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All Journal International Journal of Power Electronics and Drive Systems (IJPEDS)
Kyeong-Hwa Kim
Department of Electrical and Information Engineering, Seoul National University of Science and Technology
Control & Systems Engineering Electrical & Electronics Engineering

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An Adaptive Virtual Impedance Based Droop Control Scheme for Parallel Inverter Operation in Low Voltage Microgrid Nguyen Tien Hai; Kyeong-Hwa Kim
International Journal of Power Electronics and Drive Systems (IJPEDS) Vol 7, No 4: December 2016
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (536.684 KB) | DOI: 10.11591/ijpeds.v7.i4.pp1309-1319

Abstract

This paper presents an adaptive virtual impedance based droop control scheme for parallel inverter operation in low voltage microgrid. Because it is essential to achieve power sharing between inverters in microgrid, various droop control schemes have been proposed. In practice, the line impedance between inverters and the point of common coupling (PCC) in microgrid are not always equal. This imbalance in line impedance often results in a reactive power mismatch among inverters. This problem has been solved by introducing a virtual impedance loop in the conventional droop control scheme. However, the reactive power sharing performance of this method is still deteriorated when the line impedances change during operation. To overcome such a problem, a new control scheme that is based on a virtual impedance loop and an impedance estimation scheme is proposed. To monitor the changes in line impedances, the impedance estimator is implemented by using the output voltages and currents of inverters as well as the voltages at the PCC. To compensate for the reactive power mismatch due to the line impedance changes, the estimated line impedance is fed to the virtual impedance loop in which it adjusts the virtual impedance value. Comparative simulation results with the conventional ones verify the effectiveness of the proposed adaptive virtual impedance based droop control scheme.
Open-Switch Fault-Tolerant Control of a Grid-Side Converter in a Wind Power Generation System Partha Sarati Das; Kyeong-Hwa Kim
International Journal of Power Electronics and Drive Systems (IJPEDS) Vol 6, No 2: June 2015
Publisher : Institute of Advanced Engineering and Science

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.11591/ijpeds.v6.i2.pp293-304

Abstract

A fault-tolerant technique of a grid-side converter (GSC) is a very important task because the unbalanced grid power endangers the overall system. Since the GSC is very sensitive to grid disturbance, the complete system needs to be stopped suddenly once an open-switch fault occurs. To improve the reliability of system, the continuous operation should be guaranteed. In this paper, a redundant topology based fault-tolerant algorithm is proposed for a GSC in a wind power generation system. The proposed scheme consists of the fault detection and fault-tolerant algorithms. The fault detection algorithm employs the durations of positive and negaitive cycles of three-phase grid currents as well as normalized root mean square (RMS) currents. Once a fault is detected, the corresponding faulty phase is identified and isolated to enable the fault-tolerant operation. The faulty phase is replaced by redundant one rapidly to recover the original shape of the grid currents, which ensures the continuity in operation. In contrast with the conventional methods, the proposed fault detection and fault-tolerant algorithms work effectively even in the presence of the open faults in multiple switches in the GSC. Simulation results verify the effectiveness of the proposed fault diagnosis and fault-tolerant control algorithms.
Co-Authors Nguyen Tien Hai Partha Sarati Das