PHD-EE RESEARCH SEMINAR "SAMPLING ORDER-LIMITED SIGNALS ON THE SPHERE"
Date: March 04, 2026 Time: 10:00 AM Location: EE Reading Room
Speaker: Salaar Khan Supervisor: Dr. Zubair Khalid
Many important signals are naturally defined on spherical surfaces, such as global climate data or antenna radiation patterns. A standard tool for analyzing such data is the spherical harmonic transform (SHT), which enables accurate representation and reconstruction of signals that are band-limited at degree L. In many practical cases, spherical signals exhibit near rotational symmetry. For example, temperature variations often show similar behavior along lines of constant latitude. As a result, these signals have weak contributions from higher-order spherical harmonics. By exploiting this structure, the proposed framework presents a theoretical formulation for order-limited spherical signals that uses a sampling scheme based on Gauss-Legendre quadrature to accurately compute SHT and its inverse using only L(2M+1) samples. This reduces both the number of required measurements and the computational cost, while preserving reconstruction accuracy for order-limited signals. Numerical accuracy and computational complexity analysis demonstrate the efficiency of this approach, highlighting its practical relevance in applications such as antenna theory and spherical data processing at large.
PHD-EE SEMINAR - II "HYBRID NONLINEAR CONTROL OF CONSTANT POWER LOAD-FED CONVERTERS IN DC MICROGRIDS"
Date: March 04, 2026 Time: 03:30 PM Location: EE Reading Room
Speaker: Hafiz Mian Muhammad Adil Supervisor: Dr. Hassan Abbas Khan
The increasing penetration of renewable energy sources and fuel cells has accelerated the deployment of DC microgrids. However, the presence of tightly regulated electronic loads, operating as constant power loads (CPLs), introduces negative incremental impedance characteristics that can destabilize interfacing converter dynamics and compromise DC bus voltage regulation. Consequently, a key challenge in CPL-fed converter systems is achieving robust stabilization of converter dynamics and reliable DC bus voltage regulation under diverse operating conditions, including load variations and large-signal disturbances. Existing control approaches either rely on linearized models that sacrifice robustness beyond limited operating regions or exhibit degraded dynamic performance, thereby restricting their applicability in high-performance DC microgrids.
This work develops a hybrid nonlinear control framework for CPL-fed converter systems in DC microgrids. The proposed approach integrates synergetic control for fast dynamic convergence with the supertwisting sliding mode algorithm to enhance robustness while eliminating chattering. To avoid empirical parameter tuning, controller gains are optimally determined using metaheuristic algorithms, including Ant Lion Optimizer, Grey Wolf Optimizer, and Slime Mould Algorithm. The effectiveness of the proposed framework is validated across multiple converter topologies, including boost, buck, and four-switch buckâboost converters, under varying CPL penetration levels, resistive load changes, and input voltage fluctuations. Comparative evaluation against state-of-the-art controllers demonstrates fast settling times, minimal overshoot, negligible steady-state error, and strong robustness under large-signal load disturbances. Controller hardware-in-the-loop validation further confirms the practical feasibility of the proposed control framework.
Overall, the proposed approach significantly enhances dynamic robustness and voltage regulation in CPL-fed systems, thereby enabling more reliable renewable integration and supporting the advancement of resilient, next-generation DC microgrids.
04
Mar
Date: March 04, 2026
Time: 10:00 AM
Location: EE Reading Room
Speaker: Salaar Khan
Supervisor: Dr. Zubair Khalid
04
Mar
Date: March 04, 2026
Time: 03:30 PM
Location: EE Reading Room
Speaker: Hafiz Mian Muhammad Adil
Supervisor: Dr. Hassan Abbas Khan