The extensive use of Distributed Generators in Electrical and power systems made it a must to explore its functionality and the issues related to their connection to the grid. One of the main issues is unintentional islanding, which has been considered and studied for many years since it has serious consequences on electric systems and line workers safety. Therefore, islanding detection methods is a motivating topic to be discussed by many scientists and engineers. Islanding detection methods can be divided into two main categories, remote methods and local methods; the later method is classified into passive techniques and active techniques. This paper represents two methods of the passive islanding techniques and a simple comparison between both of them. The selected two methods are the over/under voltage and over/under frequency detection method and the wavelet based method. These two were implemented and simulated using Matlab/Simulink toolboxes. The simulation results proved that the two studied methods have a good performance for parallel RLC loads having quality factor of 2.5. The simulated passive techniques have no negative impact on the power quality.

Matlab/Simulink implementation & simulation of islanding detection using passive methods

Island detection is the essential function of the distributed grid-connected power generation systems, and it is also the difficulty of the research. Active detection method such as frequency shift or sliding mode frequency disturbance, injecting harmonics to the grid, which influences the grid power quality, and there is a certain non-detection zone (NDZ). Therewith, a kind of island detection method based on reactive power disturbance has been put forward in this paper. Simulation and experimental results show that the reactive power of the disturbance of island detection method not only achieve detection with no non-detection zone, small harmonic content of output waveform, and closing a tiny change of reactive power, but also because the disturbances have little effect on the output power of photovoltaic power generation system.

Islanding detection method for PV grid-connected inverter based on dynamic reactive power disturbance

Aiming at the disadvantages of existing methods,a new passive islanding detection algorithm is proposed based on analyzing the basic principle of islanding detection.The value of Δf/ΔVL is regarded as the detection index and the identification of islanding is realized by comparing the evaluated value with the given threshold value.Simulation study with MATLAB is done with considering the impacts of several disturbances such as change of local load and voltage sag of grid on islanding detection.The results show that the algorithm is simple and feasible,fast and reliable,and the non-detection zone is very small.

Zhang Chao

Papers

Islanding Detection Method for Distributed Generation Systems