This paper investigates the reliability of 3-phase, 2×3-phase and 5-phase inverters for a marine propulsion application. Analytical formulae and thermal model are used to assess the junction temperature of the semiconductors. The overall failure rate of the inverter is calculated by using the individual failure rate of each semiconductor, which depends on its junction temperature. In case of open-phase fault, state transition diagrams show the reconfiguration capabilities and Markov models are used to quantify the reliability improvement of 5-phase system with respect to 2×3-phase and 3-phase systems. This enhancement obtained by changing the current control strategy makes the motor to operate with reduced but sufficient performances.

This paper presents a kW range marine tidal current power generation system consisting of a fixed pitch marine current turbine (MCT) with two permanent magnet synchronous generators in the turbine shaft, two diode rectifiers (each rectifier is associated with a permanent magnet synchronous generator) and a DC source voltage. This system is designed for a kW range robust power supply. The specificity of the proposed system is that the two generators have different numbers of turns in their windings and the two rectifiers are in parallel in the same DC source. It has been demonstrated that the proposed system is able to harness very efficiently the energy of the turbine in the whole tidal cycle. The proposed system is interesting because it does not need complex control system and it allows minimizing converter losses costs due to electronic devices as controlled IGBT PWM converters usually used in conventional power generation systems. The analytical results have been confirmed numerically using PSIM software for two kW range generators with the same magnetic circuit and different winding number of turns.

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