A Series-Connected Topology of a Diode Rectifier and a Voltage-Source Converter for an HVDC Transmission System

In this letter, a novel converter topology of high-voltage direct current (HVDC) transmission for integrating the offshore wind farm (WF) with the grid is proposed, which consists of a series connection of the 12-pulse diode rectifiers and a voltage-source converter (VSC). For this topology, the PCC (point of common coupling) voltage of the offshore WF side is regulated at a constant magnitude and constant frequency by the WFVSC. Also, the current at the PCC becomes almost sinusoidal since the WFVSC functions as an active power filter for the 11th- and 13th-order harmonic current components. By virtue of the diode rectifier, the cost and power loss of HVDC converters is reduced compared with the case of the conventional fully rated VSC, whereas the performance is kept almost the same. The PSCAD/EMTDC simulation results for a 500-MW HVDC transmission system have been shown to verify the validity of the proposed scheme.