DIgSILENT PowerFactory | HVDC Connected Offshore Wind Farm Fault Analysis

DIgSILENT PowerFactory | HVDC Connected Offshore Wind Farm Fault Analysis

MATLABSolutions demonstrate how to use the MATLAB software for simulation of a The wind turbine models used in this project are generic DFIG (doubly-fed induction generator) models which are provided with PowerFactory . These models can be found in the global templates folder.This document presents a model of a high voltage direct current (HVDC) system. Simulations are performed and the results are discussed. The simulations show the behaviour of the HVDC system in the case of onshore and offshore faults.

Abstract

This paper discusses the modelling of an HVDC link for a 400 MW offshore wind farm consisting of DFIG wind turbines. Voltage source converters (VSC) are used for the HVDC connection. The paper covers load flow calculation and time-domain simulation (RMS and EMT).

Introduction

In the Base Case of the HVDC Offshore Wind Farm example, a model of an offshore wind farm is represented. The wind farm consists of 80 wind turbines connected via a voltage source converter high voltage direct current system (VSC HVDC) to a 380 kV onshore transmission network. Each wind turbine has a nominal active power of 5 MW. The machines are equipped with doubly-fed induction generators (DFIG, wind turbine type 3). Only 10 of the 80 wind turbines are modelled as individual machines (these are represented in the “Detailed Feeder” single line diagram). The remaining 70 turbines are aggregated into four DFIG models: three models representing 20 parallel machines and one representing 10 parallel machines. This approach offers a compromise where detailed studies of the explicitly modelled feeder can be carried out but where the overall the size of the system is reduced.

The wind farm model was built using a Template of a wind turbine model from PowerFactory’s global library. The template includes models of the main elements of the wind turbine (Generator and Transformer), as well as the additional dynamic models which represent the controllers, PLL etc. during dynamic RMS and EMT simulations. The asynchronous generator model used for the DFIG contains the simulation equations for the frequency converter used on the rotor. Hence only one connection is needed to connect the generator to the network (the frequency converter is connected internally). The HVDC link was modelled using the VSC element in PowerFactory . The control structure is of a generic type. A description of the control structure used is given in chapter 4. A short description of the usage of the HVDC system in other projects is given in Section 5. The Base Case has been configured for a load flow calculation. For all other kinds of calculation or simulation, please refer to the other Study Cases.

HVDC Control The HVDC control is based on a generic structure. It consists of two separate composite models: one controls the onshore converter with its chopper resistors, the other one controls the offshore converter.