Grid integration and a power quality assessment of a wave‐energy park

• Published in: IET smart grid 2019-12, Vol.2 (4), p.625-634
• Main Authors: Parwal, Arvind, Fregelius, Martin, Leijon, Jennifer, Chatzigiannakou, Maria, Svensson, Olle, Strömstedt, Erland, Temiz, Irina, Oliveira, Janaina Goncalves, Boström, Cecilia, Leijon, Mats
• Format: Article
• Language: English
• Subjects: Aircraft launching devices; Annual reports; B1210 Power electronics, supply and supervisory circuits; B1250 Modulators, demodulators, discriminators and mixers; B8120L Power supply quality and harmonics; B8240B Wave power; B8360N DC‐AC power convertors (invertors); DC bus; Electric potential; electric power conversion system; Electric power grids; Electricity distribution; Energy; Energy conversion; Energy harvesting; Engineering Science with specialization in Science of Electricity; EPCS; Field programmable gate arrays; grid connection; grid integration; grid-code requirements; grid-current harmonics; grid-phase tracking; grid-voltage harmonics; Harmonic distortion; harmonic filter; harmonic orders; Heaving; higher-order harmonics; Inverters; invertors; lower-order harmonics; lower-order voltage harmonics; Lysekil; Ocean waves; phase locked loops; phase-locked loop; PI control; PLL transfer function; power grids; power quality assessment; power quality context; power supply quality; power system harmonics; proportional–integral gains; Quality assessment; rectifier; Sweden; Teknisk fysik med inriktning mot elektricitetslära; total harmonic distortion; Transfer functions; Voltage; voltage-source convertors; voltage-source inverter; Wave energy; WAVE ENERGY SMART GRID HARMONIC DISTORTION; Wave power; wave power generation; wave-energy harvesting; wave-energy park
• ISSN: 2515-2947; 2515-2947
• DOI: 10.1049/iet-stg.2019.0009

This study presents a step toward the grid connection of a wave‐energy park through an electric power conversion system (EPCS) developed and installed for the wave‐energy harvesting in Lysekil, Sweden. The EPCS comprises a rectifier, a DC bus, and an inverter followed by a harmonic filter (HF). The higher‐ and lower‐order harmonics injected by the inverter in a power quality context are investigated. The lower‐order voltage harmonics partially distort the voltage‐source inverter output grid current. A phase‐locked loop‐based (PLL) grid‐phase tracking is used to attenuate the lower‐order harmonics by reflecting the grid harmonics in the inverter output. An expression for the grid‐current harmonics as a function of the grid‐voltage harmonics has been derived and implemented. A mathematical model is derived to obtain a transfer function for the PLL, and finally, proportional–integral gains are tuned for stable system operation. An HF for mitigating the higher‐order harmonics has been implemented. The total harmonic distortion is evaluated experimentally, and the results fulfil the grid‐code requirements at various frequencies and harmonic orders.