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 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 method and by 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 results´ and `theoretical results´ to be compared. Calculated values and simulation results of notch width with changes in firing delay angles are presented and discussed in some detail for typical marine drive units. Existing methods of reducing the notch area is discussed using simulation results.