Islanding detection and control in distributed generators

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Despite the numerous environmental and economic benefits of the integration of renewable distributed generation (DG) into the distribution network of power systems, there are a number of technical challenges that come with it. Unintentional islanding is one of the critical issues regarding DGs integration into the distribution grid. Unintentional islanding occurs when DG suddenly becomes electrically isolated from the main grid but continues to energize the local loads it serves or portion of the power system. In the event of unintentional islanding, frequency voltage and the rest of parameters for power system may be completely out of the acceptable limits, as the island formation is unregulated. The unintentional islanding is undesirable in power system as it can severely damage loads, risk the life of utility line workers. It is, therefore, imperative to develop an islanding controls strategy that helps mitigate the unintentional islanding phenomenon in DGs. In this project work, Rate of change of voltage (ROCOV), Change in sine waveform at the output of inverter during islanding and, total harmonic distortion of voltage are the islanding detection methods designed and employed for detecting unintentional islanding. A 100- kW photovoltaic system was designed and modelled as the DG for the study, and hence the project considers only inverter-based DG. MATLAB Simulation was then carried out for the detection and control of unintentional islanding. After several iterations of the simulation, the desired results from the simulation were obtained. Based on the results from the project, certain recommendations were made, and the project design can be implemented on a live DG system.
Capstone Project submitted to the Department of Engineering, Ashesi University in partial fulfillment of the requirements for the award of Bachelor of Science degree in Electrical and Electronic Engineering, May 2021
power systems