Grid Forming Energy Router: A utility interface for Renewable Energy Sources and Energy Storage Grid Integration Applications




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Large scale integration of Renewable Energy Sources (RES) (Solar/Photovoltaic (PV), Fuel Cells (FC), wind) with smart devices into the grid is becoming an attractive concept to meet increasing energy demand and to reduce stress on the conventional grid. Smart grid which is an advanced automated power grid is a fascinating idea of bringing RES closer to centralized generation with smart sensing devices, advanced control and integrated communications. This convergence provides more reliable and efficient renewable power while reducing the carbon footprint, with reduction in power transmission distance, cost and associated transmission losses. However, intermittent nature of RES impacts power quality, grid stability and reliability, which makes it imperative to integrate RES with Energy Storage (ES) for their widespread adoption. Also, real-time control of data, information exchange, and energy management in smart grid are crucial for a fast, reliable, and secure system. Thus, the design of a utility interface known as Energy router (ER) for RES, ES, and grid integration application, which is smart, intelligent, portable, resilient and easy to operate was the primary source of motivation for this research. This dissertation discusses the design and development of ER architecture and control for RES, ES, and grid integration application. To ensure seamless interaction and power transfer (bidirectional, if required) among the RES, ES, grid, and load, in ER a compact and efficient Multi-Port Converter (MPC) is required. Apart from selection of suitable MPC and hence, the structure for ER, the ER control also needs attention. Due to the presence of inverterbased RES with zero/low inertia, the ER does not respond dynamically to frequency changes and leads to frequency swings during load disturbances which can cause load tripping issues. This dissertation discusses the development of control for ER, which enables ER to synchronize autonomously with the grid and emulate the behavior of Synchronous Machine (SM) to stabilize and regulate the voltage and frequency of the system during disturbances. This is done by adding virtual inertia and damping into the system and the control is known as Grid Forming (GFM) droop control. To harvest maximum performance efficiency, real-time and dynamic control with energy management from ER in the smart-grid network this dissertation also explores the development of a dedicated communication module to be integrated with the ER. First, the proposed ER architecture and it’s control were simulated in MATLAB/Plecs and various operating scenarios were evaluated. Simulation results prove the viability of the ER, and its control algorithm for various operating scenarios involving RES and ES systems. Subsequently, the ER blocks were implemented using GaN devices and experimentally verified. Measurements indicate that this small-scale laboratory prototype is able to transfer around 1.2kW of power in both directions between battery and dc bus.



Engineering, Electronics and Electrical