Faculty Publications
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Item Control of transformerless T-type DVR using multiple delayed signal cancellation PLL under unbalanced and distorted grid condition(Elsevier B.V., 2021) Rajkumar, K.; Parthiban, P.; Lokesh, N.In the near future, the power system network may experience severe voltage distortions due to association of renewable energy sources (RES), and the large penetration of power electronic based loads into the microgrid. To protect sensitive loads from these distorted and unbalanced grid conditions, the commonly used dynamic voltage restorer (DVR) requires effective control algorithms. The effective control algorithm comprises a controller, and accurate estimation of grid phase angle/frequency, and magnitude, thereby the reference DVR voltage is accurately estimated. The synchronous reference frame based phased locked loop (SRF-PLL) is commonly used for phase angle estimation. However, during unbalanced, distorted, and dc-offset conditions, the performance of SRF-PLL is unsatisfactory. To improve its performance, it is cascaded with prefilters such as dual second order generalized integrator (DSOGI), cascaded delayed signal cancellation (CDSC), and multiple delayed signal cancellation (MDSC). Among these prefilters, MDSC has superior performance under all grid conditions with less delay time and memory requirement. In addition to an effective control algorithm, the DVR system requires high power density converters. The power density of the system is increased using transformerless T-type converter. In this paper, the effectiveness of MDSC-PLL for the transformerless T-type converter based DVR is evaluated in MATLAB/Simulink for various grid conditions such as voltage sag/swell, unbalance voltage sag/swell, harmonics, and dc-offset. © 2021 Karabuk UniversityItem A finite control set model predictive controller for single-phase transformerless T-type dynamic voltage restorer(Springer Science and Business Media Deutschland GmbH, 2023) Rajkumar, K.; Grimm, F.; Parthiban, P.; Baghdadi, M.; Lokesh, N.This paper presents a five-level T-type multilevel inverter (MLI) with a finite control set model predictive control (FCS-MPC) scheme for a single-phase transformerless dynamic voltage restorer (DVR). Typical two-level voltage source inverters are not suitable for high-power and medium-voltage applications due to high dv/dt, large size, and high cost of the filter, as well as high voltage stress on all switches. To overcome these issues, a reduced switch count T-type MLI-based transformerless DVR is proposed. The literature does not yet describe an FCS-MPC control scheme for transformerless T-type DVR. The FCS-MPC controller predicts the future of the trajectory of the controlled variables based on a prediction model. The optimal state is then selected using a cost function that is formed by combining predicted and reference variables. The proposed control technique minimizes the total harmonic distortion to a very low value compared to a linear PI controller. In addition, this control scheme is not dependent on a modulation scheme and linear control technique. The proposed system is validated by both simulation and experimental results. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.