Steady-State Characteristics of a Line-Commutated Converter-Based High-Voltage Direct Current Transmission System for Series-Connected Wind Power Plants

A line-commutated converter-based (LCC) high-voltage direct current (HVdc) transmission system without ac harmonic filters for series-connected wind power plants has been proposed. This type of wind power plant is expected as a next-generation offshore wind power plant due to offshore substation free. In the LCC-HVdc system, power compensators are connected to each receiving-end circuit instead of the conventional ac harmonic filters and static var compensators (SVC). In this article, steady-state characteristics of the system are investigated through theoretical and experimental investigations. A set of steady-state equations for the system is derived first. The steady-state characteristics of the system for changes in wind speed are discussed using experimental setup built in our laboratory, and the validity of the derived equations is confirmed. Also, it is shown that the output active power and reactive power of the system can be controlled independently. Finally, the steady-state characteristics of a practical-scale system are investigated using the steady-state equations.