Flicker mitigation in industrial systems

[摘要] This thesis investigates the compensation of voltage flicker in an industrial environment. Industrialloads draw progressively less sinusoidal currents. These currents cause non-sinusoidal voltagedrop over the line impedance, causing a distorted line voltage. The light output of incandescentelectric lighting systems is quadratically proportional to the line voltage, and thus variations in theline voltage cause irritating variations in the output of such systems.Two tools to analyse flicker problems are developed: A USB data logger is built to log measuredwaveforms to computer hard disk. These data are analysed using a MATLAB implementation of theIEC-specified flicker meter.A converter-based flicker compensator is found to be the only compensator capable ofcompensating general flicker loads. Such a compensator is developed using the synchronousreference frame filtering technique. Several aspects of the compensator are dealt with in detailincluding selection of a current control strategy, calculation and implementation of the converterduty cycles and compensation of the various non-idealities in such a controller.Full compensation is contrasted to reactive compensation – the second option being lessexpensive but also less effective in the compensation of certain loads. The effectiveness of reactivecompensation is found to be dependent not only on the type of load, but also on the type of linefeeding the flicker load.Three industrial flicker loads are measured and analysed: a three-phase welder, a sawmill and arock crusher. These loads are simulated, and the compensation proposed confirmed via thesesimulations. The compensation of the three-phase welder is tested using a hardware scale model.This verified the operation of the proposed flicker compensator in practice.

[发布机构] Stellenbosch University