Grid Impedance Monitoring System for Distributed Power Generation Electronic Interfaces

Overview of Multi-functional Grid-connected Inverter and Its Application in Micro-grid

“…Therefore, the system impedance has important significance for the distributed renewable energy grid-connected unit. Some grid-connected technical standards from the Europe and Germany clearly demanded that the grid-connected inverter should check the system impedance and can halt work or convert into the islands operation pattern when the impedance of the system change dramatically [50][51]. Thus it can be seen that the detection of the system impedance should also become an important part of the distributed grid-connected power generation unit.…”

Online thevenin equivalent parameter estimation using nonlinear and linear recursive least square algorithm

“…The methods of equivalent impedance estimation can be broadly classified as active and passive type [14]. Passive methods utilize the existing disturbance present in power networks, for example detection of low order harmonic frequency impedance.…”

Islanding Detection Method of a Photovoltaic Power Generation System Based on a CMAC Neural Network

“…Conventional islanding detection methods can be divided into passive and active detection methods [4][5][6][7][8][9][10]. Passive detection methods primarily monitor the voltages, frequencies, and phases at the load-end to identify the occurrence of islanding operations, and include the phase jump detection method [5], voltage harmonic detection method [6], power changing rate detection method [7], and passive grid impedance measurement method [8]. However, when the difference between the power output of the photovoltaic power generation system and the total power consumption is limited, variations in the system voltage or frequency are not sufficiently apparent for relay detection.…”

“…However, when the difference between the power output of the photovoltaic power generation system and the total power consumption is limited, variations in the system voltage or frequency are not sufficiently apparent for relay detection. Therefore, the disadvantage of passive detection methods is that they possess a non-detection zone, which hinders the immediate and effective detection of islanding phenomena during utility grid outages [8].…”

“…Therefore, regardless of whether the total system output power and the total load power consumption are balanced, actively initiated interference upsets the balance and generates significant voltage and frequency variations to detect islanding operations. Active detection methods include the active frequency drift, slip mode frequency shift, active voltage drift, load variation methods [9], and active grid impedance measurement method [8]. Nonetheless, a number of external factors may generate interference in the power system.…”