What is the impact of PMS (Power Measurement System) switch operation on metering EMC (Electrical Measuring Control)?

The instantaneous operation of the internal switches (power switches, load switches) of the PMS generates strong transient electromagnetic fields and conducted interference. This interference can intrude into the metering circuit through spatial coupling, power line coupling, and ground line coupling, causing spikes or reference fluctuations in the sampled values of the metering chip. In severe cases, this may trigger metering protection or miscalibration. The main mechanisms of this influence include: the high dV/dt of the switching node is coupled to analog ground through parasitic capacitance; the di/dt of the switching loop generates noise voltage on the common ground impedance; and the radiation field of the switching arc is picked up by the sampling loop. To assess the impact, the analog input and reference voltage of the metering chip can be observed with an oscilloscope during switching operation. Solutions include: physically moving the metering circuit away from the switching devices; adding a two-stage filter and an LDO to the metering analog power supply; adding a common-mode inductor CMZ2012A-900T to the output of the switching power supply; and optimizing grounding to ensure a single-point connection between the metering ground and the power ground. After rectification, the instantaneous metering error caused by switching operation can be reduced from 5% to below 0.1%, ensuring that metering accuracy is not affected by switching operation.