Abstract: Provided are an anti-islanding method for a distributed generator in a direct current distribution grid and an anti-islanding device therefor. The method includes: feeding an alternating voltage component into an output end of the AC/DC interface transverter, a frequency of the alternating voltage component being less than the power frequency; sampling a first voltage signal of an output end of the DC/DC transverter; extracting a first effective value of an alternating signal included in the first voltage signal; comparing the first effective value with a first preset voltage; and controlling the distributed generator to stop operation, in a case that it is determined that the first effective value is less than the first preset voltage, which indicates that islanding occurs for the distributed generator.
Type:
Grant
Filed:
September 27, 2015
Date of Patent:
March 20, 2018
Assignees:
State Grid Heibei Electic Power Research Institute, Hebei Electric Power Commissioning Institute
Inventors:
Wenping Hu, Jie Guo, Lei Wang, Xiaobo Duan
Abstract: A system for staring a large-scale power load in a micro grid comprises a PCC grid connection switch, a micro grid alternating-current bus, an active power filter (APF), an energy storage inverter, an energy storage battery, a current-limiting resistor R, contactors K1-K3, a time relay KT, a power supply relay board, a micro grid maser control system, a frequency converter rectifying circuit, a frequency converter filter circuit, and a frequency converter inverter circuit. There are the advantages: an output torque of a power load can be effectively improved by using a variable frequency starting apparatus, and a starting current is also small; the provided method can effectively reduce a harmonic current when a variable frequency starting apparatus starts a power load, the phenomenon that two power sources supply power on a direct-current side of the variable frequency starting apparatus at the same time is avoided, thereby improving the stability and the economy of a micro grid.
Type:
Grant
Filed:
June 24, 2014
Date of Patent:
January 30, 2018
Assignees:
STATE GRID HEBEI ELECTRIC POWER RESEARCH INSTITUTE, HEBEI ELECTRIC POWER COMMISSIONING INSTITUTE, STATE GRID CORPORATION OF CHINA
Abstract: A system for staring a large-scale power load in a micro grid comprises a PCC grid connection switch, a micro grid alternating-current bus, an active power filter (APF), an energy storage inverter, an energy storage battery, a current-limiting resistor R, contactors K1-K3, a time relay KT, a power supply relay board, a micro grid maser control system, a frequency converter rectifying circuit, a frequency converter filter circuit, and a frequency converter inverter circuit. There are the advantages: an output torque of a power load can be effectively improved by using a variable frequency starting apparatus, and a starting current is also small; the provided method can effectively reduce a harmonic current when a variable frequency starting apparatus starts a power load, the phenomenon that two power sources supply power on a direct-current side of the variable frequency starting apparatus at the same time is avoided, thereby improving the stability and the economy of a micro grid.
Type:
Application
Filed:
June 24, 2014
Publication date:
October 6, 2016
Applicants:
STATE GRID CORPORATION OF CHINA, STATE GRID HEBEI ELECTRIC POWER RESEARCH INSTITUTE, HEBEI ELECTRIC POWER COMMISSIONING INSTITUTE