Projects

At UTK:

As a postdoctoral fellow at the University of Tennessee, I completed the following projects:

• Enhancement of Power Transmission Capacity: The growing deployment of renewable energy resources adds operations stress to the existing transmission corridors, making some of the transmission lines operate at or near their rated capacity. Building new transmission corridors or converting HVAC to HVDC to increase power transmission is often restricted by high implementation costs. In collaboration with the Oak Ridge National Laboratory (ORNL), we aim to address this challenge in this project. We developed a technique to increase the fundamental voltage component without increasing the operating voltage magnitude by injecting a zero sequence voltage. The proposed method enhances power transmission capacity at a remarkably low cost.

• Improving the Linear Modulation Range for 3-Phase AC Inverters: Improving DC bus voltage utilization is crucial for 3-phase or multiphase inverters, as it is cost-effective and provides fault-tolerant operation to some extent. To achieve this, we explored multiple zero-sequence harmonic injections with the fundamental modulation signal to improve the linear operating range of 3-phase AC systems. The proposed technique is better than the existing modulation technique in enhancing the linear modulation range. This technique is particularly useful for EV applications during sudden high torque requirements.

• Assessing Grid Requirements for Connecting Hydrogen PEM Electrolyzers: In collaboration with Bosch LLC, we conducted a comprehensive study of the various grid requirements necessary for connecting a proton exchange membrane (PEM) electrolyzer with the grid. This involves analyzing parameters such as current and voltage harmonics, power and voltage flicker, and through requirements with different grounding arrangements.

• Modular Multilevel Converter as Load Tester: As a part of the project team, I developed the sorting algorithm to balance the sub-module capacitor voltage in the MMC, soft start capability to reduce the high starting current and bypassing of submodules during a fault. Through this study we laid the initial groundwork for developing and testing a MMC from its inception.

Right now, I am involved in the following two projects:

• SiC-Based Ultrafast Switch Module: This project focuses on developing a SiC-based ultrafast, noise-immune, modular switch module (20 kV, 250 A), particularly for outdoor applications. As a part of the project, my responsibility is to develop application scenarios like bus transfer for naval shipboard and aviation applications, bypass switches for series and shunt compensating devices for power transmission, solid state protective devices for transmission and distribution applications, etc. Subsequently, for each of the applications, I am developing the design requirements like lightning and switching impulse withstand voltage, operating duty, insulation design, partial discharge requirements, etc.

• Bi-directional Resonant DC-DC Converter: This project focuses on developing an isolated bi-directional DC-DC converter for offboard EV charging applications. The objective of this project is to have a flat efficiency and tightly regulated output voltage profiles for widely varying input voltage and output power. Another objective is to optimize the weight of the designed converter. To meet these objectives, I am developing a design tool to find the minimum weight converter design considering all the design inputs and constraints. With the help of this tool I am comparing different resonant topologies based on their weight, magnetics and control feasibility.

At IITK:

At IIT Kanpur, I focused on:

• Harmonic Compensation by Single Renewable Energy Sources: The proliferation of non-linear loads, particularly at the distribution system, deteriorates the power quality. However, this situation presents an opportunity to employ installed RESs to mitigate harmonics by leveraging the available kVA rating of the interfacing power electronic (PE) converter. It is important to optimize the inverter's capacity utilization to prevent issues like inverter controller saturation or excessive current stress on the inverter switches. In one of the works, an adaptive load harmonic compensation technique compliant with the IEEE 519-2014 standard is proposed, aiming at both harmonic mitigations and minimizing the current stress on the inverter switches.

• Harmonic Compensation by Multiple Renewable Energy Sources: If multiple inverters are involved in harmonic compensation, it becomes essential to effectively distribute the harmonic power among them. Traditional droop control methods are not sufficient for this purpose. I used the virtual impedance emulation technique to address this challenge in one of my works. Furthermore, a harmonic voltage emulation method is proposed to compensate for the harmonic voltage drop across the virtual impedance. Consequently, this approach accomplishes two key objectives: ensuring proportional sharing of harmonic current between the inverters based on their ratings and maintaining a good voltage profile at the inverter terminal.

• Voltage Regulation by Renewable Energy Resources: In distribution networks, voltage regulation relies on the active and reactive power injected by RESs. Conventional reactive power compensation methods are not sufficient to address this problem for such a network. In my research, I develop a mathematical relationship between the node voltage of a grid-connected RES and its active and reactive power injections. Notably, the voltage demonstrates a non-monotonic correlation with the injected active and reactive power. To optimize voltage regulation without requiring additional sensors, I proposed a technique to track the maxima of this non-monotonic curve. This approach ensures the best possible voltage regulation across various operational scenarios, enhancing system performance without requiring extra sensors.

• Active Thermal Control of Converters: The intermittent power profile of RESs results in frequent thermal expansion and contraction cycles at the junction of the PE devices. This temperature cycle reduces the reliability of the PE converters. In one of my works, we developed a temperature-dependent power sharing technique to distribute the thermal stress between all the converters during the steady state. During the thermal transient, the proposed method reduces the magnitude of temperature ripple at the junction of PE devices, thus improving the reliability of the PE converters.