The world's largest "back-to-back" flexible direct current (DC) project was completed in the Guangdong-Hong Kong-Macao Greater Bay Area of China on Saturday. The construction of the project, with an investment of 9.9 billion yuan (about $1.48 billion), took two years, and led to an investment of about 8 billion yuan (about $1.2 billion) in the upstream and downstream industry chains.