Online Monitoring of Network Impedances Using Digital Network Analyzer Techniques

This paper presents an extension to the cross-correlation method for switching power converter identification which allows monitoring of Thevenin source and load impedances. This information can be used for fault localization, converter health monitoring, and load estimation. Additional insight into performance degradation due to subsystem interaction can also be obtained. To verify the proposed approach, impedances of three commonly encountered loads and an undamped input filter are measured and compared to results from a conventional network analyzer. Some practical techniques for improved high-frequency measurements are given, and a method to measure the minor loop gain at an interface is proposed.