Analysis of Overlap in Power Electronic Drives in Marine Networks

Isolated power networks such as those used in ships, submarines, oil rigs etc. have different source impedance characteristics as compared to shore based grid supplies meaning waveform quality is different when power electronic systems are used, for example there is a noticeable increase in notching caused by overlap. This paper examines notching and resulting non-characteristic distortion in marine power systems using analytical and simulation using PS-CAD software. The effect of notching at different locations in a ships power network changes with source inductance and examples are given which allow simulated result and theoretical results to be considered and compared. Calculated values and simulation results of notch width with changes in firing delay angles are presented and discussed in some detail. Existing methods of reducing the notch area is discussed using simulation results. Areas where improvement is required in order to minimise notch level have been identified and presented. Future research by the authors into wave disturbance in marine electrical systems has also been indicated.