Minh-Chau Dinh

Loss Characteristic Analysis of an HTS DC Model Cable Connected to a Model VSC-HVDC System

The purpose of high-temperature superconducting (HTS) cables as the transmission conductor in a high-voltage dc transmission system is mainly to reduce the Joule losses arising from the power transmission process. However, the harmonic currents generated from the switching behavior of the voltage source converters result in power loss in the HTS dc power cable. The cable loss characteristic should be analyzed in terms of its practical applications. In this paper, the harmonic currents characteristics were analyzed in both steady and transient state. An HTS dc cable model was also developed using the finite elements method to examine its loss characteristics. The results showed that the harmonic loss of the HTS dc model cable depends on the properties of the voltage source converters, the operating dc current level, and the ac system conditions. This work will be useful in studying the loss analysis of a real HTS dc power cable.

Transposition-Based Connection Scheme and Joint Box Concept for a Tri-Axial HTS Power Cable

Tri-axial high temperature superconducting (HTS) power cables are being developed to maximize their advantages, which include reducing amount of HTS wires, having a low-leakage magnetic field, and being compact compared to different types of HTS power cables. However, a drawback of HTS power cables is their inherent imbalance impedance, which is due to an asymmetrical structure on each phase. To solve this problem, the phases must be transposed. The authors designed a distribution class tri-axial HTS power cable, as well as a transposition-based connection scheme for the cable. The phases of the cable were connected to each other via transposition through their cross-connections. This was achieved with an insulated support structure with three walled-off areas for insulation between three the phases, as well as transposition conductors, including copper base and HTS wires. In this paper, a distribution class tri-axial HTS power cable and a connection scheme for it are designed. The results, including the transposition-based joint box design, are described in detail. The connection scheme will be applied to the joint box of the cable for high-capacity and long-distance transmission.

An Effective Control Scheme of a Back-to-Back Converter with Shunt-Connected HTS SMES for Frequency Regulation of an Islanded Microgrid

High temperature superconducting magnetic energy storage (HTS SMES) is known as an effective solution to significantly decrease the voltage and power fluctuations of grid connected wind power generation system (WPGS). This paper implements an effective control scheme of a back-to- back converter with shunt-connected HTS SMES for the frequency regulation of an islanded microgrid. The back-to-back converter is used to connect the WPGS to the grid. A large-scale HTS SMES is linked to the DC side of the back-to-back converter through a two-quadrant DC/DC chopper. An adaptive control strategy is implemented for the back-to-back converter and the two-quadrant DC/DC chopper to improve the efficiency of the whole system. The performance of the proposed control system was evaluated in a test power system using PSCAD/EMTDC. The simulation results clearly show that the back-to-back converter with shunt-connected HTS SMES operates effectively with the proposed control strategy for stabilizing the power system frequency fluctuations.

Suggestion of a novel PHILS method for operation analysis of a thyristror controlled series capacitor

A study on practical characteristics analysis of Thyristor Controlled Series Capacitor (TCSC) is needed before applying it to a practical grid. Generally, simulation tools are utilized to investigate the operating characteristics of TCSC with respect to steady-state, temporary and dynamic performance. In this paper, we introduce Real Time Digital Simulator (RTDS)-based power hardware in the loop simulation (PHILS) to examine the operation of TCSC. A laboratory scale TCSC which has the same reactance characteristic as a practical 345 kV TCSC is designed and fabricated. It is incorporated with a 345 kV model power system in RTDS through the interface card. RTDS-based PHILS of TCSC is conducted to verify the power control function of TCSC. Simulation results demonstrate the ability of the proposed method in verifying the design, control strategies and proper functionality of the TCSC and real-time performance of TCSC as well.