How to locate conducted noise on the AC side of a PCS (Power Control System) for energy storage?

Locating conducted noise on the AC side of a PCS is a systematic process.

First, based on conducted emission test data, analyze the frequencies exceeding the standard: the 150kHz-1MHz band is usually related to switching frequency harmonics; frequencies above 1MHz are mostly caused by diode reverse recovery and parasitic oscillations.

Second, use a near-field probe to scan the power board, detecting strong magnetic or electric fields at key nodes such as switching transistors, diodes, and filters to initially locate the noise source. Then, distinguish between common-mode and differential-mode noise-dominant frequency bands by plugging and unplugging LISN test leads or temporarily adding or removing filter components.

Finally, based on circuit principles, check whether filter parameters resonate at the noise frequency, causing failure. For example, temporarily connecting capacitors of different values in parallel and observing the spectrum changes can accurately pinpoint the root cause of the problem.