Novel control strategies for HVDC system with self‐contained converter

Abstract

This paper discusses newly developed control strategies of a self‐commutated converter applied to the HVDC system. An upper and lower power‐limited dc voltage control establishes high performance in a two‐terminal HVDC system. A voltage margin method to reverse dc transmission power also is introduced. Even when the communication system is shut down, if required, dc transmission power can be changed with the authors' proposed controls applied to the terminal control. Furthermore, the dc voltage control scheme with two‐stage voltage control characteristic is presented for multiterminal HVDC system use. When one terminal is collapsed, the multiterminal HVDC system can be operated because of the proposed control characteristics. Simulator studies were carried out to verify the proposed control performance in the two‐terminal HVDC system and successful test results such as power reversal and a terminal start‐up during other terminal operations are shown.

An Improved Droop-Based Control Strategy for MT-HVDC Systems

“…To overcome the dependency of high-speed communication infrastructure and improve the reliability of AC/DC grids, the voltage margin method and voltage droop-based control method are proposed. The voltage margin method is a modified version of the master-slave technique to tackle the N-1 security problem and control the voltage through the voltage and active power of different converters in MT-HVDC systems [33][34][35][36][37][38]. The main drawbacks of this method are the complexity in terms of controlling several parameters and the large oscillations of power flow due to the sudden changes in the DC voltage [18].…”

Review of the DC voltage coordinated control strategies for multi‐terminal VSC‐MVDC distribution network

“…The voltage margin was first proposed in 1999 by Nakajima et al ., for the Shin‐Shinano three‐terminal VSC system in Japan [47–49]. Typically, this control strategy is a modification of the master–slave scheme in which the constant power/current and constant DC voltage modes are combined in each converter terminal.…”

“…Since the DC voltage reference values for each terminal in an MTDC grid differ by a voltage margin, the DC voltage control is regulated by one terminal with the smallest reference towards those with the largest in a cascading way [37]. The voltage margin method is highly reliable as the DC voltage working point is fixed and it is possible to precisely control the power flow in the MTDC grid [34, 47, 50].…”

Operation and Power Flow Control of Multi-Terminal DC Networks for Grid Integration of Offshore Wind Farms Using Genetic Algorithms

“…Usually, the control of point-to-point HVDC transmission systems is arranged as follows: one terminal controls the dc network voltage, whereas the other operates in current or power regulation mode. This control philosophy-of having only one converter controlling the direct voltage-can also be extended to MTDC networks, as in the voltage margin method [25,39,40].…”