Current Source Converter series tapping of a LCC-HVDC transmission system for integration of offshore wind power plants

When using HVDC there are two available commercial possibilities: Transmissions based on Line Commutated Converters (LCC) and based on Voltage Source Converters (VSC). VSC-HVDC is more suitable for creating offshore grids. Despite this fact, many LCC transmission systems are in operation across the sea interconnecting mainlands or islands. This work addresses the concept of connecting wind power plants in series with an LCC-HVDC transmission link already built by means of a self-commutating Current Source Converter (CSC).

The idea is similar to series tapping stations which can extract power form the HVDC link. Nevertheless, a CSC can act as a rectifier or inverter, so power reversal is available and has the same advantages of a VSC. The coupling between LCC stations and the CSC is straightforward since both topologies are current source converters. The control and operation of the system under normal conditions is presented and verified by means of simulations using MATLAB Simulink.