Method for controlling voltage and frequency of the local offshore grid responsible for connecting large offshore commercial wind turbines with the rectifier diode-based HVDC-link applied to an external controller

摘要

This study introduces a method for controlling a system that rectifies electric current where power is transferred from several offshore wind power generation systems through a common offshore AC line, into a diode-based bridge. This modular rectifier comprises one or more uncontrolled modules (such as diode rectifiers). According to the study, the wind power supply systems receive a reactive power reference from a central external regulator to maintain the common AC-line frequency. Although there are other control methods for this topology, the proposed external control uses commercial wind turbine with no changes in their internal control. The power plant control systems use their own algorithm to select the active and reactive power reference, maintaining the original wind turbine control unaltered. This method for controlling the voltage and the frequency of local offshore grid allows the operation of the different rectifiers end of the HVDC link. PSCAD® simulations are used to prove the technical control and the design concept.