Abstract: [Objectives] Solar energy and wind energy are the main forces for China to achieve the "dual carbon" goal. The installation of solar energy is limited in the economically developed areas along the eastern coast of China, while offshore wind power has great development potential. The harmonic problem of large-scale offshore wind power needs to be solved. [Methods] Aiming at the problem of excessive 5th and 7th harmonics in a 300MW large offshore wind farm near the coast of Zhejiang, this paper proposes to use parallel high-voltage active power .filtering technology to suppress the harmonics in the grid. The filter system was comprehensively designed. A platform with complete protection functions integrated in the container was built. Hardware In the Loop (HIL) simulations were carried out to test its harmonic suppression performance. 31 operating conditions were tested, such as normal operating conditions, conditions with variation of grid operation mode, and the increase of grid background harmonic level. [Results] It was found that after the active filter was incorporated, under, the 5th and 7th harmonic voltage and harmonic current indicators of the wind power grid connection point can meet the national standard requirements. [Conclusions] The results demonstrated the effectiveness of the design method proposed in this paper. This work has important engineering reference significance for the harmonic control of large-scale offshore wind power.

Key words: offshore wind power, large-scale offshore wind power plant, active power filter, power quality, harmonic suppression system, design and application