Modern power systems equipped with a large amount of power electronic converters may suffer from small-signal instability due to the control interactions. The interoperability among different converter systems becomes even more challenging because of the confidentiality of converter control. This speech will introduce the frequency-domain stability analysis approach for electronic power systems based on impedance models. First, a unified impedance modeling framework for converter systems is introduced. Next, how to utilize the impedance models for the local-level and system-level stability analysis is presented, which brings different insights. The analyses are elaborated by several case studies in simulations and experiments.