Stability Analysis of Systems With High VSC Penetration: Where Is the Limit?

The paper addresses the stability of modern voltage-source-converter-dominated power systems, which are experiencing a progressive phase-out of conventional generation. An essential system model is used to capture the fundamental system dynamics, to conduct a thorough mathematical analysis and understand the principles governing network stability in converter-dominated power systems. A detailed analysis is developed to identify the stability limits of this system when voltage source converters operate in grid-following mode. A complete mathematical linear model including the dynamics of the network elements is used to identify these stability limits. Based on this model, a detailed assessment of the influence that the voltage source converter controllers have on the system stability is performed to identify potential instabilities and reveal the main mechanisms of interaction. Then, a study to identify the minimum synchronous generation to ensure system stability is developed, including analytical expressions of some critical system poles. The mathematical results obtained are validated with a complete non-linear simulation model of the system.