Stability assessment of a system comprising a single machine and inverter with scalable ratings

• Published in: 2017 North American Power Symposium (NAPS) pp. 1 - 6
• Main Authors: Yashen Lin, Johnson, Brian, Gevorgian, Vahan, Purba, Victor, Dhople, Sairaj
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.09.2017
• Subjects: Analytical models; Inverters; Phase locked loops; Power system dynamics; Power system stability; Stability analysis; Voltage control
• DOI: 10.1109/NAPS.2017.8107365

Synchronous machines have traditionally acted as the foundation of large-scale electrical infrastructures and their physical properties have formed the cornerstone of system operations. However, with the increased integration of distributed renewable resources and energy-storage technologies, there is a need to systematically acknowledge the dynamics of power-electronics inverters - the primary energy-conversion interface in such systems - in all aspects of modeling, analysis, and control of the bulk power network. In this paper, we assess the properties of coupled machine-inverter systems by studying an elementary system comprised of a synchronous generator, three-phase inverter, and a load. The inverter model is formulated such that its power rating can be scaled continuously across power levels while preserving its closed-loop response. Accordingly, the properties of the machine-inverter system can be assessed for varying ratios of machine-to-inverter power ratings. After linearizing the model and assessing its eigenvalues, we show that system stability is highly dependent on the inverter current controller and machine exciter, thus uncovering a key concern with mixed machine-inverter systems and motivating the need for next-generation grid-stabilizing inverter controls.