How to suppress carrier interference in a concentrator?

Concentrator power line carrier communication is susceptible to high-frequency noise from the power grid and harmonic interference from its own switching power supply, leading to an increased bit error rate. This interference is mainly concentrated in the carrier frequency band (e.g., 100-500kHz) and harmonics. Suppression requires filtering the coupling path and isolating the circuit. A common-mode inductor CMZ3225A-510T (51μH) is connected in series in the carrier coupling loop to suppress common-mode noise, and two capacitors (0.1μF/275VAC) are connected in parallel to filter out differential-mode components.

The power supply pins of the carrier chip use a PBZ1608E600Z0T ferrite bead (60Ω@100MHz) with a 10μF+0.1μF capacitor for π-type filtering, reducing power supply noise by 30dB. Simultaneously, the carrier signal transformer winding process is optimized, using three wires wound in parallel to reduce leakage inductance, and a grounding shield is added between the primary and secondary windings of the transformer. In the PCB layout, the carrier coupling area is isolated from the ground plane of the digital circuit. Through the above measures, the signal-to-noise ratio of carrier communication can be improved by 20dB, and the bit error rate is less than 10^-6, meeting the requirements of the DL/T 645 communication protocol.