A Fast DC Fault Detection Method for Multi-Terminal AC/DC Hybrid Distribution Network Based on Voltage Change Rate of DC Current-Limiting Inductor

Xiaomin Qi,Wei Pei,Luyang Li,Li Kong

doi:10.3390/en11071828

Abstract

The rapid detection of direct current (DC) faults is one of the key technologies for the development of multi-terminal alternating current (AC)/DC hybrid distribution networks. The DC fault current rises quickly and affects the whole network. Therefore, DC faults must be detected much faster than AC faults. This paper proposes a fast DC fault detection method based on the voltage change rate of the current-limiting inductor (CLI) for the multi-terminal AC/DC hybrid distribution network. Firstly, the characteristics of the fault voltages and currents and of the CLIs are studied in detail, and the feasibility of using the voltage change rate of the CLI to detect DC fault is analyzed. Based on this, a primary fault detection method is proposed to identify the faulty line, determine the fault type and the fault poles using the amplitudes of the single-ended CLI voltage change rates. For high-resistance DC faults, a backup detection method using the directions and amplitudes of the voltage change rates of the double-ended CLIs is proposed. Finally, the proposed method is verified by MATLAB simulations. The simulation results show that the proposed method can detect all DC faults accurately, and the faulty line, fault type and fault poles can be determined quickly. The proposed method is not affected by the fault location, current-limiting inductance, power reversal of the converters, AC fault and communication delay.

Highlights

In recent years, direct current (DC) distribution networks and alternating current (AC)/DC hybrid distribution networks are attracting increasing attention due to the increasing demand for distributed generation and the need for regional grid interconnection [1,2]
This paper proposes a method for the fast detection of DC faults in a multi-terminal AC/DC
The voltage change rates of the current-limiting inductor (CLI) on the non-faulty lines are less than 5.924 × 107 kV/ms

Summary

Introduction

DC distribution networks and AC/DC hybrid distribution networks are attracting increasing attention due to the increasing demand for distributed generation and the need for regional grid interconnection [1,2]. The AC/DC hybrid distribution network can satisfy the above requirements and achieve the interconnection and transition between the AC distribution network and the DC distribution network. The entire AC and DC network can be called a regional multi-terminal AC/DC hybrid distribution network [3]. Due to the low impedance of the DC distribution network, the fault currents will increase rapidly after a DC fault [4]. In the multi-terminal AC/DC hybrid distribution network, the fault currents of different converters are superimposed over each other, which results in the higher demands on the semiconductor devices in the system. If the fault cannot be detected as soon as possible and the faulty line is not isolated timely, Energies 2018, 11, 1828; doi:10.3390/en11071828 www.mdpi.com/journal/energies

Methods

Results

Conclusion