Implementation of Simplified Models of Local Controller for Multi-terminal HVDC Systems in DIgSILENT PowerFactory

Abstract

The North Sea has a vast potential for renewable energy generation: offshore wind power, tidal and wave energy. The voltage source converter (VSC) and high voltage direct current (HVDC) systems are more flexible than their AC counterparts. This offers distinct advantages for integrating offshore wind farms to inland grid system. It seems that advances on technologies open the door for VSC-HVDC systems at higher voltage and at higher power range, which is making multi-terminal HVDC (MTDC) system technically feasible. The control system for MTDC consists of a central master controller and local terminal controllers at the site of each converter station. The terminal controllers (outer controllers) are mainly responsible for active power control, reactive power control, DC voltage regulation and AC voltage regulation. Typical MTDC consists of several VSC-HVDC terminals connected together, and different operation mode and controllers allows them interact together. DC voltage controllers play a very important role on the DC network performance. There are several DC voltage control strategies possible: voltage margin, two-stage direct voltage controller, three-stage direct voltage controller, voltage droop, etc. The contribution of this book’s chapter is to present some of the main aspects regarding the modelling and simulation of two control strategies: voltage margin method (VMM) and standard voltage droop (SVD). To this end, theoretical aspects of controllers are presented and are used to develop DIgSILENT simulation language (DSL) models. The developed models are used to evaluate the performance a simple 3-terminal HVDC system.