Engineer|Researcher|Innovator

Power & Energy Systems:

- Robust Combat Power and Energy Controls (RCPC) - Modeling, controls design and validation of grid-forming front- and back-end modular power electronic converter systems (average plus switched models) with battery charge/discharge controllers for both islanded and grid-supporting energy magazines (an enlarged and networked concept of energy modules), to ensure power quality throughout and to support distributed energy resources (DERs) if required.
[Financially Supported by The Office of Naval Research (ONR), USA]
- Power Electronics Power Distribution Systems (PEPDS) for Electric Ship Zonal Networks - Development, deployment and validation of state-of-the-art power electronic converter models of modular multilevel converter (MMC), dual active bridge (DAB), synchronous and inter-linking buck converters on high-speed Xilinx SoC-FPGA-based frameworks for medium- and high-power density energy routing applications.
[Financially Supported by The Office of Naval Research (ONR), USA]
- High-Performance Networked and Distributed Controls for Modular Power Electronic Converters - Monolithic and dispersed modeling of a power electronic building block (PEBB)-based modular converters' network associated with distributed multi-loop control interfaces for control hardware-in-the-loop (CHiL) testing through a Xilinx multi-FPGA (Kintex and Virtex) setup.
[Financially Supported by The Office of Naval Research (ONR), USA]

FPGA-Based High-Speed (ns-level simulation time-step) Models Development: Latency based linear multi-step compound (LB-LMC) solver algorithm is employed that ratifies exploitation of latency at each individual component level isolating their solution from the multi-physic system solution. LB-LMC is compatible for parallel computations for a dynamic power electronic system and is very similar to the classical electromagnetic transient (EMT) analysis methodology. The fundamental concept is to separate the solution of nonlinear or switched components of the system of interest from the linear constituents. In LB-LMC, the non-linear components are substituted with an equivalent voltage or current source while their dynamics are represented by a set of state-space equations. The state-space equations are solved applying an explicit integration method while the resistive companion network equations are solved by an implicit discretization in parallel. Thus, LB-LMC allows the system solution at every simulation time-step where the dynamics of the switched variables get embedded into the model solution.
Controls: Multi-Loop Proportional-Integral (PI), Synchronous Reference Frame (SRF), Proportional-Resonant (PR), Deadbeat or Model Predictive Control (MPC)

- Microgrid Building Block (MBB) Modeling and Simulations for Assessment of Marine Hydrokinetic-based Reliable and Resilient Electrification in Alaska (ORCA) - Building blocks for microgrids to enhance scalability, interoperability and reliability for remote community-based or off-shore medium-voltage DC distribution systems are proposed, designed and simulated in real-time for rapid control prototyping (RCP) & HIL implementation and to ensure flexible energy transfer, cooperative controls for nominal operations and event-triggered controls for any contingencies such as faults. The HIL environment is OPAL-RT/RT-LAB with ARTEMiS/State-Space Nodal (SSN) and non-SSN solvers with both switched mode and circuit average (mathematical) models of converters.
[Financially Supported by The Department of Energy (DOE), USA, and in Collaboration with National Renewable Energy Laboratory (NREL)]

Real-Time Fast (µs-level simulation time-step) Test Platform: OPAL-RT provides the opportunity to test switched and average (mathematically formed) models of power electronic systems for fast computations in HIL implementations. The real-time simulations are executed for a fixed time-step and it is expected that the simulator operations are all achieved within that pre-specified time-step for a particular system of interest. If this condition is not met, then the real-time simulation results are erroneous. In this case, the real-time measurements cannot be considered as correct and the controls might not involve stable regulations in the model operations. The practical delays which bring about this erroneous behavior of the real-time model are referred to as overruns. In reality, models can perform correctly if the overruns can be kept very low but not exactly zero in OPAL-RT provided that any range cannot be inferred as the most optimum and generic for all models and all simulation platforms and is subject to device and package limitations. This is a testing variable and the value in practical execution differs for other simulator packages and simulation models.
PEBB Fault Ride-Through Algorithm Development: A novel PEBB or sub-module (SM) fault tolerant method for modular MVDC power electronic systems is developed offering no requirement of extra device or hardware, complete suppression of circulating currents through the phase legs, no change or augmentation of the DC-link voltage, no increase in the original modulation index and no over-design & extra voltage stress on the capacitors during post-fault condition. (Doctoral dissertation focuses on this topic. More details will be provided after final defense.)

- Multi-Domain Real-Time Simulations of a Practical Unbalanced Utility Distribution Network (SITKA) for System Dynamics Analysis - An unbalanced utility network data in phasor domain and developed machine models (wind turbines and synchronous generators) with relevant controls in electro-magnetic transient (EMT) domain are implemented on OPAL-RT simulator packages RT-LAB/ePHASORsim to analyze bus and machine interactions and their impacts on dynamic stability of the power system.
[Financially Supported by The Department of Energy (DOE), USA, and in Collaboration with Pacific Northwest National Laboratory (PNNL)]

Multi-Rate Simulations & Dynamic Stability Tests: RT-LAB/ePHASORsim solver contains network data within a 60 Hz (phasor) domain for a simulation time-step of 0.1 - 1 ms. for static load flow solutions. Simulink EMT domain contains the Type-4 (DFIG) wind farms and synchronous generator models & respective detailed controls that are run for 50 µs simulation time-step. Serial communication interfaces make the data transfer between phasors (bus voltage magnitudes, angles, static load values) and EMT measurements (current injections, power transients, frequency) to execute the dynamics analysis. The limit of bus voltage stability ranges between 0.95 to 1.05 pu. Machine interactions for different practical sizing and siting, bus over- & under-voltage phenomena, frequency instability and automatic generation control have been investigated.

- Real-Time Testing of Low-Voltage Microgrid Model - OPAL-RT/RT-LAB/ARTEMiS/SSN solver-based real-time implementation and validation of a hybrid microgrid model with MMC-DSTATCOM, battery energy storage system (BESS), integrated renewable energy resources (RES) and associated switched mode power electronic converter units & controls with reduced practical delays (overruns) in execution.
- Custom Pulse Width Modulation (PWM) System Interfaced with Xilinx Microblaze Soft Processor - A PWM generation system on a Xilinx FPGA evaluation board is developed for power electronic switching modules which is interfaced and controlled by Microblaze through AXI-4 bus. The design takes user inputs – FPGA board clock frequency, desired PWM signal frequency, desired duty ratio control value and dead-band frequency. There is a feedback sensor interacting with an external block that enables the closed-loop regulation.
- Vector Control Motor Drive System for a 3-Phase Induction Machine with a 3-Phase Active Rectifier Consisted of an LCR Filter - Detailed analysis for designing a damped LCL filter for a front-end active rectifier regulated through a multi-loop PI controller (voltage regulation in outer loop and current regulation in inner loop) using phase margin and cross-over frequency-based design has been conducted to observe an induction motor's (asynchronous machine) dynamic operations. In the motor driver, power is supplied to the machine via a voltage source inverter (VSI).
- Design of a Switching Converter Using a Commercial Si IGBT Module and a SiC MOSFET Module with Relevant Thermal Circuit Considerations - A synchronous DC/DC buck converter which is a class of SMPS containing at least two semiconductor devices and at least one energy storage element has been designed and simulated for detailed investigation of energy efficiency and thermal losses regarding application of industrial Si IGBT and SiC MOSFET power switching modules such as Powerex CM200DY-24NF, Powerex QID1230015 and CAS325M12HM2. Characteristics and calculations have been determined for converter circuit design considering desired specifications of the gate driver and selection of the heat sink to reduce thermal losses.
- Non-Intrusive Load Monitoring (NILM) for Modern Smart and Sophisticated Energy Grids - Application of complex signal processing methods i.e. ensemble empirical mode decomposition (EEMD), statistical features extracted from devices' energy signatures, classical supervised machine learning algorithms i.e. random forest, robust computer science engineering techniques i.e. shapelets and device type classification and status monitoring via deep neural networks.
- Grid-Integrated or Off-Board Electric Vehicle (EV) Battery Chargers - Development and validation of EV battery chargers based on variable-width and inverse sinusoidal PWM switched converters (in discontinuous conduction mode) with power factor correction, energy efficiency and thermal analysis of Si and SiC-based bidirectional DC-DC converters for any transactive energy systems and internal model-based speed estimation and Lyapunov energy function-based control of a synchronous motor for EV applications.
- Scalable DC Microgrid Architectures - Design and performance investigations of switching converters-based power management units (PMUs) to model islanded and scalable microgrid structures with uni-lateral communication and time-slot based control interfaces to support domestic loads and battery chargers.
- Switching Converters-Based Power System for Regions Victim to Frequent Power Outage - Development of an unobtrusive grid-tied emergency back-up power supply for medium- and low-power utility applications wherein most relevant and extensive experimental tests have been conducted on the engineered samples to investigate and guarantee its robustness for different types of electric appliances.
-Analysis and Improvement of Stationary and Non-Stationary Power Quality (PQ) Disturbances - Redefining PQ disturbances employing time-frequency distribution (TFD) method is proposed. Reduced interference distribution (RID), which is a member of Cohen's class TFD, is studied to define and formulate PQ indices for electric power systems - use of dynamic voltage restorer (DVR) comprising phase locked loop (PLL), proportional integral (PI) compensator and super capacitor as the energy storage device in order to mitigate PQ disturbances like voltage sag, swell, short interruption, imbalance and fluctuation in three-phase distribution networks.
- Zone-Wise Load Forecasting -  A predictive model to compute regional power demand in Bangladesh on an hourly interval using regression decision tree machine learning algorithm is developed - time-series data analysis for long-term-load-forecasting (LTLF) is carried out employing annual load data recorded by ERCOT, Texas, USA.
- Rewinding of a 3-Phase Squirrel Cage Induction Motor -  Short- and open-circuit, nominal and reduced load laboratory testing, dynamics observation & measurement have been carried out.
- Load Flow Analysis of an IEEE-30 Bus System - CYME PSAF-based power flow study has been conducted using Newton-Raphson and Gauss-Seidel methods.
- An Efficient and Cost-Effective Low-Power LED Driver with Power Factor Correction, Soft-Switched Converters and Controllable PWM Units - (B.Sc. Thesis Work) An efficient design of an electrically isolated low power LED driver with active power factor controller (PFC) based on buck converter topology comprising a rectifier-fed-PFC unit which reduces the harmonic distortion of the mains line current by improving the sending-end power factor. There is a dc-link-inverter which consists of a soft switched buck converter and a parallel-loaded series L-C resonant inverter. At the receiving-end, there is a high frequency transformer provided isolation and a rectifier to feed appropriate voltage and current to a 12 W LED lighting load. The switching converters are controlled by pulse width modulation (PWM) signals of 20 kHz. The framework has been simulated on PLECS software. The total harmonic distortion (THD) of the mains line current is approximately 10.7904% at 0.9893 sending-end power factor whereas the third harmonic current is 6.1538% and the fifth harmonic current is 5.4557% of the fundamental current and these are less than the recommended values of IEC 61000-3-2. The voltage and current waveforms of every converter stage corroborate the reliability of the work.

Control Systems (Robotics & Automation):

- Digital Controllers for a Robot Arm Manipulator - Design and performance analysis of digital controllers in discrete (z-plane) and continuous-time (warped s-plane or w-plane) domains for a robot arm modeled as a single-joint or single degree of freedom (DOF) plant with a feedback sensor implying a closed-loop system. Four digital controllers - phase-lag, phase-lead, proportional-integral (PI) and proportional-integral-derivative (PID) are theoretically designed and implemented to achieve a desired phase margin for the compensated system. In addition, state feedback using pole-placement and observer are designed for the closed-loop system in discrete-time domain.
- PID Control Design for Water Bump Test Plant Using MicroLogix PLC - Bump test data of a water plant recorded through a LabView setup have been employed for developing a process control system comprising establishment of design level of operation (DLO), collection of controller output (CO), dynamic operation of the process variable (PV) and approximation of the process data behavior with a first-order plus dead time (FOPDT) dynamic model. Allen-Bradley MicroLogix 1100 Programmable Controller (Bulletin 1763 Controllers and 1762 Expansion I/O) containing a power supply and an isolated combination RS-232/485 communication port, and an Ethernet port has been utilized.
- A Cyber-Vigilance System for Anti-Terrorist Drives Based on an Unmanned Aerial Vehicular Networking Signal Jammer - A novel framework of an unmanned aerial vehicular networking signal jammer is developed which is oriented to block incoming and outgoing signals of all frequencies transmitted from a specifically marginalized territory scanned and explored by the aerial vehicle during sudden anti-terrorist drives conducted by the law enforcement agencies to avert the unprecedented fatalities.
- Low-Cost Braille Embosser -  An innovative design of a low-cost Braille printer is presented and implemented wherein major concentration is given to develop the actuators which emboss the impressions on the Braille paper to make dots to decode text language in Braille format. The printing system involves cost efficiently designed inter-dependent components, such as customized printing software, wireless communication system, sensing mechanisms, and compact mechanical setup.
- Aerial Landmine Detection System with Dynamic Path and Explosion Mode Identification Features -  A substantive design of an intelligible landmine detective system is proposed and tested based on precise control over aerial motion planning and metal detection. The developed mine detector is capable of providing virtual mapping of the traversed area and a concatenated map of the points of metal signatures, no matter whether it is a rough terrain or inclined surface.
- Dynamic Map Generating Rescuer Offering Surveillance Robotic System with Autonomous Path Feedback Capability -  Design and implementation of a map integrated surveillance-cum-rescue robotic system which can provide assistance during the accidental occurrences like earthquakes and structural collapses. The explicit design of the robot provides a definite map of the traversed area dynamically with consistent video feedback. The most unique feature of the system is if in any case the communication link with the host breaks down, the robot would return to the initial place following the traversed pathway which avoids the risk of losing the device.
- Human Computer Interactive System - Human machine interface (HMI), referred to as a correlated system of human activities and operation of a specific device, ratifies control mechanism of a targeted machine by execution of certain physical actions. An effective design and testing of an Android-based human computer interactive (HCI) system with voice command activation and gesture/motion recognition to control a computer are executed. The primary objective of this work was to deploy such applications in unmanned space/defense/security missions.

Signal Processing & Machine Learning:

- Location Forensics Analysis from Electrical Network Frequency (ENF) of Digital Recordings - ENF is a signature of a power distribution grid and ENF sequences are subject to fluctuations and are inherently located in a multimedia signal, which is recorded close to the grid or directly from the mains power line. Thus, the specific location of a recording can be identified by analyzing the ENF sequences of the multimedia signal in absence of the concurrent power signal. Location-stamp verification for forensics analysis is carried out through decomposing signals into low and high frequency segments, features extraction from them and development of classification models.
- Double Talk Detection System -  An autocorrelation-based double talk detection (DTD) system with a modified normalized least mean squares (NLMS) adaptive filter algorithm for acoustic echo cancellation (AEC) is developed. This project was developed for DSP processor.
- Portable Cardiac Activity Monitoring Device with an Associated Android Application -  A human machine interface (HMI) system to monitor and analyze heart issues and physiological activities by extracting and processing photoplethysmography (PPG) signal from a pulse sensor was designed and implemented. For data analysis, filters have been employed and for consistent monitoring, a custom Android app has been developed.
- Pitch and Formant Extraction of Vowel Sounds Using Autocorrelation and Frequency Domain Spectral Analysis -  A speech features extraction system implying pitch and first two-order formant estimation of different vowel sounds embedded in different speeches using autocorrelation and frequency domain spectral analysis is developed.
- *Non-Intrusive Load Monitoring (NILM) for Modern Smart and Sophisticated Energy Grids - Application of complex signal processing methods i.e. ensemble empirical mode decomposition (EEMD), statistical features extracted from devices' energy signatures, classical supervised machine learning algorithms i.e. random forest, robust computer science engineering techniques i.e. shapelets and device type classification and status monitoring via deep neural networks.
- *Zone-Wise Load Forecasting -  A predictive model to compute regional power demand in Bangladesh on an hourly interval using regression decision tree machine learning algorithm is developed - time-series data analysis for long-term-load-forecasting (LTLF) is carried out employing annual load data recorded by ERCOT, Texas, USA.
* - As explained in "Power & Energy Systems" section