Solutions for Seamless Closed-Loop Load Transfer of Low-Voltage Distribution Network in Multiple Application Scenarios

doi:10.12204/j.issn.1000-7229.2022.07.013

Abstract

Abstract:

As an important network reconfiguration technology, the closed-loop load transfer (CLLT) is of great significance to improve the reliability and economic efficiency of the distribution network. The conventional CLLT has a loop closing impact and the selection of loop closing point is limited by the phase angle difference between two substations. In this paper, two solutions are proposed to solve the technical problems of CLLT with the large angle difference in the Guangzhou distribution network, which are based on series-parallel compensation and back-to-back topology, respectively. They can be applied to a variety of scenarios and provide AC and DC interfaces. The wiring modes of these schemes are given, and their structural characteristics, performance parameters, and operating principles are analyzed. To adapt to the condition of three-phase imbalance and harmonic pollution, the improvement measures of the two schemes are proposed from the structure and control perspective. Finally, the operating principle of the seamless CLLT device in several typical scenarios is verified by simulation, thus providing computational support for the actual development of seamless CLLT.

Key words: closed-loop load transfer, low-voltage distribution network, uninterrupted power supply, power supply reliability

CLC Number:

TM72

LI Junlin, HAN Jie, XIE Cong, LIU Xiao, ZHANG Xu, WANG Dan. Solutions for Seamless Closed-Loop Load Transfer of Low-Voltage Distribution Network in Multiple Application Scenarios[J]. ELECTRIC POWER CONSTRUCTION, 2022, 43(7): 113-120.

Figures/Tables 10

Fig.1 Typical load transfer scenarios

Fig.2 Basic loop closing modes

Fig.3 Topology of seamless closed-loop load transfer based on UPQC structure

Fig.4 Schematic structure of a VSC

Fig.5 Topology of seamless closed-loop load transfer based on back-to-back structure

Fig.6 Steady-state equivalent circuit of the topology based on UPQC

Fig.7 Relationship between capacity and phase angle difference of two topologies

Fig.8 Simulation results of operating condition 1

Fig.9 Simulation results of operating condition 2

Fig.10 Simulation results of grid-connection of mobile generator

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