Voltage Flicker Evaluation for Wave Energy Converters – Assessment Guidelines

Voltage flicker is a power quality problem caused by regularly oscillating active and reactive power either from a load or generator. The regular power oscillations induce a voltage change at the grid connection which is proportional to the amplitude of the power oscillation and at the same frequency. The impedance of the grid (grid strength) at the point of connection is a factor in the amplitude of the voltage oscillation. The frequency band of interest for flicker evaluation is from 0.01-20Hz, and is most severe at 8.8Hz. The frequency of the primary resource for wave energy converters lies within this range. Therefore the coupling of the input resource to the output power of a wave energy converter will cause voltage flicker at the point of connection. This is particularly true for ‘direct drive’ wave energy converters. This paper serves to establish the flicker effects of wave energy converters on the grid voltage. The paper outlines some working guidelines for the evaluation of flicker from a device. The paper concludes that wave energy converters may exceed flicker emission limits, particularly in weak grid areas and suggests some strategies for overcoming this problem.