Faculty Publications
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Item Transient behavioural modelling of Battery Energy Storage System supporting Microgrid(Institute of Electrical and Electronics Engineers Inc., 2020) Joshua, A.M.; Vittal, K.P.Energy storage is a vital component for a resilient microgrid. The high investment cost associated with storage is the major deterrent for its integration in a microgrid. But with the advent of Electric Vehicles and Smart Grids, battery technology and its mass production have got a huge thrust. Cost of the battery is anticipated to come down in future and battery storage customary in microgrids. Though storage will solve all problems related to power mismatches between generation and loads, it brings some additional challenges. Due to the bidirectional power flows, control and protection become complicated. For an effective microgrid protection design, there is a need to study the transient behaviour of its components. In this paper, a microgrid model with a centralised Battery Energy Storage System (BESS) is built. The control strategies automatically switch between grid connected and standalone modes of operation. The model is verified using PSCAD simulations for various operating scenarios. This paper emphasises the role of BESS in a microgrid and investigates the transient behaviour of Distributed Generators (DGs) under various faults in grid connected and islanded operation modes. © 2020 IEEE.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 Protection schemes for a battery energy storage system based microgrid(Elsevier Ltd, 2022) Joshua, A.M.; Vittal, K.P.This paper evaluates directional and adaptive overcurrent protection schemes in microgrids. A microgrid supported by a centralised Battery Energy Storage System (BESS) is chosen for the study. The stringent PQ controller of BESS will not allow it to dissipate into a fault, during its charging mode, causing the conventional directional schemes to mal-operate. A direction estimation scheme using magnitude and angle of superimposed positive sequence impedance is proposed to address this issue in BESS. Further, two fault detection techniques are proposed for BESS integrated feeders. The Main Protection Unit (MPU) detects an internal fault when there is a mismatch in the direction of relays at either end of a feeder. The second scheme uses adaptive overcurrent relay settings. Since the fault current is limited with PQ control, the pickup current is calculated dynamically with this control. Whereas a fixed pickup current is chosen, when the BESS inverter is voltage controlled. Simulations have been carried out using MATLAB/SIMULINK software. The proposed schemes work well for bidirectional power flows and in grid connected and standalone modes of microgrid operation. © 2021Item 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 LtdItem IMU-based segmental root mean square analysis of gait in individuals with cerebellar ataxia: a pilot cross-sectional study(Nature Research, 2025) Mendonca, J.; Joshua, A.M.; Shetty, S.; Chemmangat, K.; Krishnan, S.; Kumar, K.V.; Misri, Z.; Pai, R.; Pai, S.Cerebellar ataxia (CA) affects limb movement, balance, and gait. Subjective rating scales like Scale for the Assessment and Rating of Ataxia (SARA) may underestimate gait severity. Inertial measurement units (IMUs) offer an objective gait analysis. Impaired trunk control might compromise gait performance and stability in individuals with ataxia. This study quantified trunk kinematics and gait parameters using Root Mean Square (RMS) values, comparing CA to healthy individuals. Ten CA cases and twenty healthy controls were recruited. Six IMU sensors positioned at anatomical landmarks recorded data via two ESP32 microcontrollers using Wi-Fi. Participants walked a 10-meter path at a self-selected pace. RMS mean linear and angular velocity and angular deviation were calculated. Individuals with CA showed decreased mediolateral linear acceleration at the left shoulder (p = 0.001) and an increased vertical linear acceleration at the right ankle (p = 0.015), left shoulder (p = 0.028), and back (p = 0.019). Total angular velocity was lower at the right shoulder (p = 0.017), left shoulder (p = 0.005), back (p = 0.002), and both ankles (right: p = 0.001; left: p = 0.001). The correlation between IMU-derived features and SARA-gait score in the CA group was not statistically significant (all p > 0.05), except for the right shoulder’s mediolateral angular velocity (p = 0.046). Both ankle segments’ angular deviations (right: p = 0.001; left: p = 0.006) were reduced. The CA group revealed reduced RMS linear and angular velocities. IMU-based trunk and gait analysis provides a more objective method that would help in planning targeted rehabilitation treatments. Trial registration: The study was approved by the Institutional Ethics Committee (IEC), Kasturba Medical College, Mangalore, Manipal Academy of Higher Education (IEC KMC MLR 12/2023/483) on 21st December 2023 and the Clinical Trial Registration (CTRI/2024/07/070614) on July 15th, 2024. © The Author(s) 2025.