Detection of islanding state in electricity network

摘要

An exemplary method for detecting a three-phase islanding state in a three-phase electricity network includes supplying power to a three-phase electricity network via a power supply assembly, controlling an output frequency of the power supply assembly with a frequency reference signal adapted to deviate the output frequency of the power supply assembly from a grid frequency representing a frequency of a common electricity network whose portion of the three-phase electricity network is in normal operating conditions. The method also includes detecting a three-phase islanding state in the electricity network if the output frequency of the power supply assembly is outside an allowable value range. During a normal operating state of the electricity network, the frequency reference signal depends on an active output current of the power supply assembly.

主权项

1. A method for detecting a three-phase islanding state in a three-phase electricity network, the method comprising:
supplying power to a three-phase electricity network by a power supply assembly having an output frequency; controlling the output frequency of the power supply assembly with a frequency reference signal adapted to deviate the output frequency of the power supply assembly from a grid frequency representing a frequency of a common electricity network whose portion of the three-phase electricity network is in normal operating conditions; monitoring a magnitude of a frequency quantity obtainable from the output frequency of the power supply assembly; and detecting a three-phase islanding state in the electricity network if the magnitude of the frequency quantity is outside an allowable value range by forming a stimulus signal obtainable by multiplying a difference between the output frequency of the power supply assembly and the grid frequency by a stimulus coefficient, wherein forming of the frequency reference signal includes addition of the output frequency of the power supply assembly and the stimulus signal, and during a normal operating state of the electricity network the stimulus coefficient is a function of an active output current of the power supply assembly.