Engineering Commons^™

Impedance-Based Stability Analysis And Controller Design Of Three-Phase Inverter-Based Ac Systems, Wenchao Cao

Doctoral Dissertations

Three-phase voltage-source power inverters are widely used for energy conversion in three-phase ac systems, such as renewable energy systems and microgrids. These three-phase inverter-based ac systems may suffer from small-signal instability issues due to the dynamic interactions among inverters and passive components in the systems. It is crucial for system integrators to analyze the system stability and design the inverter controller parameters during system planning and maintenance periods to guarantee stable system operation. The impedance-based approach can analyze the stability of source-load systems, by applying the Nyquist stability criterion or the generalized Nyquist stability criterion (GNC) to the impedance ratio …

Three-Phase Power Converter Based Real-Time Synchronous Generator Emulation, Liu Yang

Doctoral Dissertations

To bridge the gap between power system research and their real application in power grids, a Hardware Test-Bed (HTB) with modular three-phase power converters has been developed at the CURENT center, the University of Tennessee, Knoxville, to emulate transmission level power systems with actual power flowing.

This dissertation focuses on the development and verification of a real-time synchronous generator (SG) emulator in the HTB. The research involved in this dissertation aims at designing a proper control to achieve emulator performance goal and investigating the sources of error and its influence on interconnected SG-emulator networks.

First, different interface algorithms (IAs) are …

Small Signal Modeling And Analysis Of Microgrid Systems, Md. Rasheduzzaman

Doctoral Dissertations

This dissertation focuses on small-signal modeling and analysis of inverter based microgrid systems. The proposed microgrid consists of two microsources placed on two different buses. The buses are connected using a distribution feeder with some impedance. The proposed microgrid can operate with the grid support, or without the grid support. When operated without the grid support, the standalone system’s microsources participate in controlling the system voltage and frequency. For a non-inertia source, such as the inverter, the load perturbations play an important role in system dynamics. In paper-I, such complex system was studied.

In the grid-tied mode, the microsources share …