Connection of renewable energy sources through grid constraint points using HVDC power transmission systems

The use of HVDC as an effective means of transmitting electrical energy now has a 50 year history since the first modern schemes were developed. Technological advances have resulted in HVDC becoming a reliable and efficient means of power transmission, both in competition with, and complementary to, AC transmission schemes. This paper will consider the opportunities and also some of the challenges involved in a range of HVDC scheme configurations. This will cover overhead transmission schemes, submarine cable schemes and back- to - back schemes. The paper also considers the specific issues involved in the design of a multi-terminal HVDC system. In each case the key issues in the planning, design and execution of the schemes are discussed. The paper will consider the most recent schemes in design and construction, such as the 1800 MW Al Fadhili station in Saudi Arabia, the long distance 3000 MW ±500 kV Three Gorges - Shanghai project and 4000 MW ±660 kV Ningdong - Shangdong projects in China. All of these projects bring new challenges to the design engineers and require considerable study of the interaction between the HVDC schemes and the AC transmission networks.