Review of control methods in HVDC system for protection purpose

• Main Author: Low, Guan Jie
• Other Authors: Abhisek Ukil
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Electric power; DRNTU::Engineering::Electrical and electronic engineering::Power electronics; DRNTU::Engineering::Electrical and electronic engineering::Control and instrumentation::Control engineering
• Online Access: http://hdl.handle.net/10356/63785
• Institution: Nanyang Technological University

This report on VSC-HVDC transmission is about the transmission of power using DC lines with control strategies. Many potential advantages can be reaped from using such transmission method. There are various combinations of outer controllers that can be used to control a VSC-HVDC system and this report hopes to explore into this area. A two-terminal VSC-HVDC model is used to study the responses of different combination of outer controllers. A direct control scheme of the VSC-HVDC system is first briefly discussed. In a direct control scheme, the power angle and the modulation index are used to perform the control of power flow in the system. It was discovered that in a direct control scheme, the parameters used for control are not decoupled. The real and reactive power flows are dependent on both the control parameters. As such, a more dynamic and decoupled control scheme is required. A vector-control scheme is next discussed and also adopted in the modelling of the system in this project. In a vector control scheme, the stationary three phase abc coordinate system is transformed into a rotating two phase dq reference frame. This transformation has enabled decoupled control of the system. The current in the d and q axes control the real and reactive power flow respectively. With this independent control of power, various combinations of outer controllers can then be designed to obtain a dynamic control of the system. At the end of the project, various simulation results of the different combinations of outer controllers are shown. Patterns were observed and recommendations are suggested to conclude this report.