Abstract : EMC testing was conducted on the power unit of a multi-level series voltage source inverter, and improvement requirements were proposed based on the test data. The structural factors and key points affecting electromagnetic compatibility performance were analyzed, and a basic model for passing high-level electrical fast transient/burst (EFT) tests was preliminarily developed. Modifications were made to the specific power unit structure to improve its EMC performance. After the structural modification, the EFT pass rate of the power unit improved from 3.0 kV, 5 kHz, 300 s to 4.0 kV, 2.5 kHz, 300 s, meeting the requirements for harsh industrial environments. The size and installation method of the power unit remained unchanged after the structural modification, so the internal structure of the inverter's power cabinet and the power unit bracket did not need to be altered. Furthermore, the complex rigid electrical connections of the main circuit inside the power unit remained unchanged; only the outer casing structure was modified to achieve the intended goal. Keywords : Frequency converter, electromagnetic compatibility, electrical fast transient pulse group, power unit structure. Abstract : As the power unit of frequency conversion equipment of voltage source of cell mid series of multi-level voltage being EMC testing, as test data was reformative requirement． it is analyzing framework and factor by touch ElectroMagnetic Compatibility capability, premeditate essential project on pass high level testing of Electrical Fast Transient, synthesis material framework of power unit running restructure, it heighten capability criterion of EMC． Power unit． As finished mstructure power unit, would it be 3.0KV-5KHz-300s ofcriterion to 4.0KV-2． SKHz-300s ofcriterion on pass electrical fast transient testing the power unit, arrive at asperity industrial locale of criterion． As the power unit is restructured, the bulk and build technique should not be changed. Therefore, the power unit framework and bracket do not need to be restructured. At the same time, the rigid connection of the main loop in the power unit should not be changed. Only the complex configuration has already fulfilled the objective. Keywords : Inverter, Electromagnetic compatibility, Electrical fast transmission, Power unit configuration. 1. Introduction In the topology of high-voltage, high-power frequency converters, the multi-level unit series voltage source type frequency converter adopts a topology of multi-level superposition, standard low-voltage power unit structure series connection, and internal capacitor array voltage regulation within the unit. Due to the characteristics of its topology, the system composition has numerous internal components and a complex structure. At the same time, due to the superposition characteristics of the topology, voltage and power upgrades can be achieved simply by increasing the number and series connection method of the standard low-voltage power units in the main topology, without redesigning the components of its power circuit. Its versatility and inheritance advantages are very prominent, giving it a natural advantage in high voltage and high power applications. Therefore, inverters with multi-level unit series voltage source structure are increasingly used in high-power, high-voltage environments. [b][align=center]For details, please click: The Impact of Changes in Inverter Power Unit Structure on Electromagnetic Compatibility Performance[/align][/b]