Fault Detection And Protective Methods For AC/DC Distribution Network

New energy power generation technologies represented by photovoltaics and wind turbines are often connected to AC/DC distribution networks in the form of distributed generator(DG),which brings new challenges to fault detection,fault location and fault handling in distribution networks.From the perspective of the practicality of fault identification and protection methods for AC and DC distribution networks,this paper studies the principle of current differential protection of AC distribution lines based on data self-synchronization method and the principle of fast direction longitudinal protection for DC distribution lines.The main contents include:The paper first analyzes the performance advantages of Hankel matrix in signal singularity detection and noise reduction.Aiming at the problem of time delay in the conventional fault detection method,a fault detection method based on singular value decomposition of Hankel matrix is proposed,which can accurately detect faults.Combined with the synchronous communication means and the short distribution characteristics of the distribution network.This paper proposes to use the time of the fault as the alignment reference of data self-synchronization to realize the current differential protection,which reduces the protection requirements for real-time synchronization signals.Two new current differential protection criterions suitable for data self-synchronization are proposed,which provides reliable current differential protection for distribution lines connected with DG.In addition,in order to realize the rapid detection of DC distribution line faults,this paper analyzes the variation characteristics of DC fault current.Based on the singularity characteristics of fault current signals,this paper proposes a fault detection method for DC distribution lines based on singular value decomposition of Hankel matrix.Based on the difference of current component signal characteristics,fault detection criteria,fault identification criteria and fault pole selection criteria are proposed to form a fast direction longitudinal protection scheme suitable for DC distribution line.The protection scheme only needs to transmit the direction signal and does not need data synchronization,which reduces the difficulty of communication construction of the DC distribution network.The protection scheme has good quick action.