Faculty Publications
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Item Control of CLLC Resonant Converter in Grid Connected Electric Bus charging station(Institute of Electrical and Electronics Engineers Inc., 2022) Bhanja, S.; Joshua, A.M.; Vittal K, K.Battery Energy Storage System(BESS) is essential for a resilient microgrid. Electric vehicle charging stations operating in vehicle to grid(V2G) can act as a portable power source in the microgrid. To regulate the power flow for both BESS and electric vehicle charging stations, a bi-directional converter is necessary. This paper presents a test case where the BESS system and electric bus(EB) charging station are connected in parallel with the utility grid and loads. The Capacitor- Inductor-Capacitor (CLLC) converter is utilized as a bi-directional DC-DC converter. The CLLC converter is widely used due to its simple symmetrical design and ability to achieve soft switching. A novel dual hysteresis band logic along with variable frequency control method has been implemented for the CLLC converter. The DC link voltage, battery current, ZVS, and ZCS operations have all been examined in MATLAB/SIMULINK environment with an appropriate controller. Findings show that the BESS and EB charging station works satisfactorily in both forward and reverse modes. © 2022 IEEE.Item Incremental transient power-based protection scheme for a DC microgrid(Springer Science and Business Media Deutschland GmbH, 2022) Joshua, A.M.; Vittal, K.P.A key step in the realisation of DC microgrids is the development of robust protection schemes. Bidirectional power flow in ring-type configurations makes protection design too complicated. This paper presents an algorithm for selective fault location and isolation of faulty parts in the transient stage itself. At the onset of a fault, the proposed scheme computes incremental transient power (Δ P) from initial changes in voltage and current. The sign of Δ P captured by different IEDs is compared to determine the fault location. Though the scheme is designed for the unit protection of feeders, it is also capable of locating and isolating external faults accurately. A backup scheme using local measurements is provided, in case of communication failure. The schemes are simulated using extensive simulations in MATLAB/SIMULINK platform. The results confirm that the proposed protection design operates within a few milliseconds and is highly selective and stable. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Item Superimposed current based differential protection scheme for AC microgrid feeders(Elsevier Ltd, 2023) Joshua, A.M.; Vittal, K.P.Legacy protection schemes face numerous challenges with the emergence of microgrids. Due to the complex controls, the fault responses in microgrids differ from conventional behaviour and vary with the operation mode. In this paper, a differential protection scheme based on fundamental frequency superimposed current phasors is proposed for microgrid feeders. The phasors are extracted using dq components instead of conventional Fourier algorithms. The performance of proposed method is tested for different fault scenarios by carrying out simulations in MATLAB/SIMULINK software. The results confirm that internal faults are detected in a few milliseconds. At the same time, the scheme remains insensitive to external faults with CT saturation and other system disturbances. The proposed scheme is unaffected by the microgrid mode of operation, direction of power flow and DG type. © 2023 Elsevier Ltd