Method for common mode voltage analysis in a system with multiple input noise sources

Power converters associated to inner triplet magnets of the Large Hadron Collider (LHC) are being updated. In this sense, conversion schemes with parallel association of H-bridge structures and integrated local energy storage systems are considered. Different topological structures, modulation techniques and interleaved operating modes are analyzed. A restrictive specification that these converters must satisfy on the load is the compliance of specific limits for each frequency component of the output common mode voltage; since they define Electromagnetic Compatibility (EMC) issues. The evaluation of the common mode voltage spectrum is not a simple operation, since these systems present multiple sources of input noise. The present work proposes a methodology to calculate a transfer function, from an equivalent single-input system, useful to determine the output common mode voltage spectrum. Simulations for a particular converter are presented.