Maximizing Synchronous Condensers' Capability to Stabilize Inverter-Based-Resource-Penetrated Grids
Bao Li, Lingling Fan, Zhixin Miao
Abstract
Synchronous condensers (SynCons) have been deployed in power grids penetrated by inverter-based resources (IBRs) worldwide to strengthen and stabilize the grids. This paper examines which machine parameters influence IBR weak grid stability and whether excitation systems also play a role. Four types of stability scenarios are examined, including transient stability, oscillations of a few Hz, oscillations near 9 Hz, and dynamic voltage stability. It is shown that the most influential machine parameter varies for the different types of stability issues. While minimization of field winding inductance (typically the major component of the machine transient reactance, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$X^{\prime }_{d}$</tex-math></inline-formula>) can significantly improve transient stability, voltage stability, and low-frequency oscillatory stability, this parameter has no influence on relatively rapid oscillations. On the other hand, minimizing rotor damper winding inductance (typically the major component of the machine subtransient reactance, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$X^{\prime \prime }_{d}$</tex-math></inline-formula>) improves the 9-Hz oscillation stability, but with insignificant influence on the other three types of stability. Furthermore, the excitation system characteristics show negligible influence for any of the scenarios. In addition to the simulation studies, we show how the operational reactances are associated with the machine's <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$dq$</tex-math></inline-formula> impedance viewed from the terminal bus and how a SynCon reduces the equivalent grid impedance, thereby improving weak grid stability. Finally, it is concluded that minimization of both transient and subtransient direct-axis reactances should help in a range of stability scenarios, while cautions should be taken when dealing with quadrature-axis transient reactances.