Analysis of the interharmonics generated by a ship propulsion system

Current source inverters associated to rectifiers are used in variable speed drive for the propulsion system onboard ships. The complete structure will generate frequency perturbations in the entire supply system which could become undesirable. In a first part, the modulation theory is applied to the ideal structure and the design of the distribution transformers is considered in order to calculate the injected currents and their resultant voltages. Finally, those results are confronted to experimental results obtained onboard an electric cruise ship. Those results show a complete validation of the theoretical calculations.