Frequency coupling matrices for multi‐stage conversion system analysis

A general approach for harmonic and interharmonic analysis of multi‐stage conversion systems is formalized. The approach is based on frequency coupling matrices (FCMs) relating voltage and current harmonics and interharmonics. Each component of the conversion system is classified as linear time—invariant or non‐linear time—invariant or non‐linear time variant and a systematic procedure to build up its FCM is presented. Then, according to the specific topology of the conversion system, single‐component FCMs are opportunely combined to deduce a whole‐system FCM. This matrix allows to estimate the absorbed current due to voltage interharmonics, to analyze the admittance of the conversion system and to investigate the current amplitude dependence on the supply voltage phase; such possibilities are shown with reference to a test system.