Resource-induced voltage flicker for wave energy converters - assessment tools

For wave energy converters, the input resource has a typical period of 5-20 s depending on the site location and dominant seastates. Wave energy converters generally produce mechanical power twice per wave cycle and therefore depending on the storage available, the electrical power output has half the period of the input resource. These regular power changes induce a voltage change at the point of connection (POC) which is proportional to the amplitude of the power change and at the same frequency. Therefore the coupling of the input resource to the output power of a wave energy converter will cause voltage flicker at the POC, which may exceed the permitted limits under specific conditions. This study establishes the nature of the flicker issue from wave energy converters. Some practical tools for the evaluation of flicker from a device are introduced. These tools are suitable for early stage flicker assessment to assist in the design process only. They are not meant of substitutes for existing codes and standards which are outlined in this study. This study concludes that wave energy converters may exceed flicker emission limits as a result of the coupling of the resource to the output power, and this may be particularly severe when connected to weak grids. Some potential strategies for overcoming this problem are presented also.