A Differential Protection Scheme Based on Improved DTW Algorithm for Distribution Networks With Highly-Penetrated Distributed Generation

Abstract

Differential protection has been introduced into the distribution network to address the ineffectiveness of traditional protection due to the uncertainties of power flow caused by the access of multiple inverter-interfaced distributed generation (IIDG). Designed for lower data synchronization costs, this paper proposes a novel differential protection scheme based on improved dynamic time warping (DTW) distance. The proposed algorithm can effectively alleviate the singularity caused by DTW's excessive X-axis distortion through relaxation search and derivative estimation and minimize the impact of data synchronization errors and data loss. Based on the proposed algorithm, the protection scheme combined with the feeder terminal unit (FTU) for fast fault isolation is designed, which can make full use of the existing equipment and reduce costs. Moreover, multiple influencing factors considered in this scheme, including transition resistance, penetration rate, and output intermittency of IIDG, variable network topology, underground cables, and hybrid lines. The test results demonstrate that the proposed protection scheme can effectively isolate short-circuit faults in various scenarios. INDEX TERMSDistribution network, improved DTW, differential current protection, inverter-interfaced distributed generation, positive sequence current, feeder terminal unit NOMENCLATURE Abbreviations IIDG Inverter-interfaced distributed generation DTW Dynamic time warping FTU Feeder terminal unit PSC Positive sequence current RS-DDTW The relaxed search derivative dynamic time warping DDTW Derivative dynamic time warping FDSS Fault data self-synchronization RDD The relaxed search derivative dynamic time warping distance RDDset The proposed protection threshold PSCDP Positive sequence current differential protection VSI Voltage source inverter PCC The point of common coupling TCDP Traditional current differential protection sx Protection device of each section cs Interconnection switch FtThe fault type RtThe transition resistance FLThe fault location I. INTRODUCTIONRecently, many countries have vigorously advocated new energy to relieve the energy crisis, improve the environment, and achieve the goal of "dual-carbon". Large numbers of Inverter-interfaced DG (IIDG) are permitted to be connected to the distribution network, making the grid structure flat, distributed and localized [1,2].However, the deployment of IIDG transforms the simple radial distribution network into a complicated decentralized multi-source network, hence, altering powerflow direction and voltage distribution [3]. Due to the access of IIDG, the fault current no longer exhibits a stepped distribution which can result in refusal operation and misoperation of traditional

Highly sensitive multifunction protection coordination scheme for improved reliability of power systems with distributed generation (PVs)

“…This connection is facilitated through a step-up transformer on the distribution side, ensuring a seamless power supply to the load. The VSI system regulates the conversion and transfer of power from the PV system to the grid, enabling efficient utilization of the generated electricity [37]. The solar cell is the primary component of the PV system.…”

“…A solar cell is capable of directly converting sunlight into electricity. Multiple solar cells are typically connected in series to form a PV module [37,38] to generate higher voltages and power levels. Commonly, the PV module's equivalent circuit, as shown in Figure 8, is used to depict its electrical behaviour.…”

“…The theoretical current source produces a current that is directly related to the amount of solar radiation it receives. The relationship between the output voltage and current based on the equivalent circuit is expressed in the following equation [37]:…”

“…This section provides the main parameter values for the PV module and inverter unit used in this work for a 1 MW PV unit, which is outlined in Tables 4 and 5. These values are utilized in the mathematical model of the PV module discussed earlier and in [37,38]. By incorporating these parameter values into the model, we can accurately simulate and analyse the behaviour and performance of the PV module under different operating conditions…”

Pilot Protection of a Distribution Network with Distributed Generators Based on 5G and Dynamic Time Warping Considering Cosine Transform

“…Reference [17] provided a practical solution for the application of 5G communication technology to the differential protection of a distribution network by improving DTW, which improved the reliability of the protection while at the same time maintaining good adaptability to the delay jitter and asynchronous errors. Reference [18] proposed a novel DTW protection scheme through a relaxation search and derivative estimation that minimized the impact of data synchronization errors and data loss on protection, and it was applicable in a distribution network containing distributed generators. Reference [19] introduced a weighted DTW algorithm that optimized the output values of DTW, mitigating the influence of edge effects and enhancing the algorithm's resilience to synchronization errors.…”