Study on the start-up and fault-restart strategies and reactive power analysis of DC distribution systems

Abstract

The DC distribution network is becoming the basic supporting component of the urban distribution network. A variety of power supplies, loads, and energy storage devices can be directly integrated into a DC distribution network, which can improve the economical and energy efficiency of the power system. This study proposes two charging strategies, two-stage charging and one-by-one charging, to make the converter start up safely or quickly return to the normal operation state after the fault clearance. Owing to the existence of numerous DC capacitors in voltage source converters, the reactive power consumption in the start-up process needs to be explicitly calculated. Mathematical expressions of reactive power requirements for different charging strategies are investigated in detail, from where it can be seen that the current-limiting resistance can significantly affect the reactive power and the entire charging time. Simulation results show that the AC voltage can be seriously affected by the oscillation of the reactive power, which will lead to voltage drop and waveform distortion in mode switching.

Keywords

• power supply quality
• power grids
• reactive power control
• voltage control
• distribution networks
• distributed power generation
• power convertors
• reactive power
• energy storage
• power distribution control
• fault-restart strategies
• reactive power analysis
• dc distribution systems
• dc distribution network
• basic supporting component
• urban distribution network
• power supplies
• energy storage devices
• economical energy efficiency
• power system
• converter start
• fault clearance
• numerous dc capacitors
• voltage source converters
• reactive power consumption
• start-up process
• reactive power requirements
• different charging strategies
• entire charging time