The Journal of Engineering (May 2019)
Self-organising technique for carrier synchronisation and phase offset distribution in modular, fault-tolerant converters
Abstract
Carrier interleaved pulse width modulated modular multilevel converters provide multiple benefits including increased effective switching frequency, switching frequency harmonic elimination, and reduced filter requirements. For converters comprising high numbers of switching modules, control is often distributed across multiple controllers, making carrier-phase synchronisation challenging. This paper presents a technique for carrier-phase synchronisation and phase offset distribution for controllers in a ring network comprising duplex serial links. The proposed method is self-organising, with equal phase offset automatically achieved across connected nodes. A key advantage of the proposed technique is capacity to enable fault tolerance, through automatic phase offset redistribution in the case of switching modules being removed from the system. An experimental prototype is implemented and evaluated using three FPGA nodes connected via 6.25 Gbps full-duplex fibre-optic links, with phase offset accuracy to within 0.1 degrees demonstrated for 25 kHz pulse width modulation.
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