Research Projects

This proposal addresses critical challenges in integrating renewable energy sources, specifically solar photovoltaics (PV) and battery energy storage systems (BESS), into power grids. Replacing conventional synchronous generators with inverter-based resources (IBR) has reduced system inertia and short circuit ratio (SCR), posing challenges for grid stability, particularly during faults and transient events. Grid-forming inverters (GFMIs) have emerged as potential solutions due to their ability to control voltage and frequency references and thereby maintain terminal voltage phasor during transient events. However, existing GFMI technologies face limitations, especially in handling fast grid transients where the inner current control loop saturates the inverter current, causing nonlinearity in voltage control. Also, due to characteristic differences between solar PV and BESS, their GFMI control philosophy needs to be different. The DC bus voltage dynamics during grid transients are tightly coupled to the control architecture of the GFMI and hence deserve a closer look for reliable operation of the inverter. The objectives of this project are to develop source-specific control architectures for GFMIs, tailored to the unique requirements of solar PV and BESS integration. The research aims to explore DC bus voltage dynamics during grid faults and develop control solutions that improve fault tolerance and voltage stability in low-inertia, low-SCR grids. A key investigation involves shifting the current control to the outer loop to enhance the GFMI's voltage and frequency regulation capabilities, addressing the limitations of traditional inner current control structures. A silicon carbide (SiC) MOSFET-based 20-kVA inverter prototype will be developed to implement and validate the proposed control strategies. Building the inverter in the lab will provide opportunities to optimise the switching frequency and bandwidth of control. Also, it will allow investigation into the sizing of the components like L-C-L and DC bus capacitor elements. The project will use a grid emulator to test the prototype's ability to handle real-world disturbances, evaluating the inverter's fault tolerance, transient response, and stability. A regenerative power source that can emulate battery and solar PV characteristics will be used for the testing. This design can be scalable to support larger PV and BESS systems, providing a foundation for practical applications in India’s evolving renewable energy grid. The success of this project is expected to lead to significant advancements in GFMI technology, offering improved resilience and reliability for renewable energy integration. It will contribute to the fundamental understanding of GFMI dynamics in weak grids, including insights into DC bus voltage behaviour under faults. The results will be disseminated in academic publications.