DC Electrical Network Research Articles

Optimal power flow with storage in DC electrified railways

Purpose Due to the increase of the traffic, issues are appearing on DC electrified railway feeding systems. One candidate solution to solve these issues and to improve their performances is to add storage systems in the railway DC electrical network. The paper presents a method based on an Optimal Power Flow (OPF) for the analysis and design of DC railway feeding systems with storage. Design/methodology/approach The paper describes a new methodology based on optimization to study DC electrified railways, including storage systems. A load flow model of a DC 1500V railway electrification system is presented, including the mobility of the train sets. Then, an Optimal Power Flow model of the DC network, including energy storage systems and feeding substation rectifiers has been developed. Finally, the OPF model has been tested on a real application case showing its benefits while searching solutions in order to improve the network performances. Findings An OPF model suitable for analysis of DC networks with storage is presented. It shows its ability to solve large scale problems. Research limitations/implications The paper focuses on the physical model of the network. The optimization model will have to be extended with application constraints. Originality/value The hypothesis presented in this paper allows to remove the discontinuities of the system in order to use a continuous optimization approach.

Superconducting DC breaker

The scheme of a superconducting fault current limiter (SFCL) rated for operation in the DC electric networks at the maximum current of 300 A, is proposed. This device incorporates a module based on 2G high-temperature superconductors and a quick-action vacuum DC interrupter. Authors present the investigation results relating both to the current-limiting capacity of DC SFCL and to recovery time of the super-conducting state after current disconnection at the voltage of 3.5 kV.

Superconducting fault current limiter with fast vacuum commutation modulus

A new approach to a problem of creation of a resistive version of superconducting fault current limiters (FCL) on the basis of HTS materials has been considered. According to this approach, a scheme of FCL is added by a commutation modulus which contains a fast vacuum interrupter. This interrupter allows one to switch off the transport current as soon as 5 ms after transition of the HTS element to the normal state. The proposed scheme allows one to restrict more than an order in value a necessary operation time of FCL in a regime of a current limitation. As a result, a time of recovering the superconducting state can be significantly reduced that allows FCL to operate in automatic iterative regime. The considering device can operate not only in high voltage ac transmission lines but also in dc electrical networks. A numerical simulation of transit processes in a proposed scheme of FCL has been performed for different regimes and its features are analyzed with respect to other schemes of FCL. An experimental study of test mock-up commutation elements of FCL has been performed. This study demonstrates an efficiency of the proposed scheme. A test of a FCL model with the limiting current up to 15 kA has been realized.