What is it about?
This paper presents a Matlab/Simulink study on islanding detection algorithms for a 100kW Grid-Connected Photovoltaic (PV) Array. The main focus is on the islanding phenomenon that occurs at the Point of Common Coupling (PCC) between Grid-Connected PV System and the rest of the electric power system (EPS) during various grid fault conditions. The Grid-Connected PV System is simulated under the conditions of islanding, and anti-islanding (AI) relay reaction times are measured through the simulation. Results are presented for Grid-Connected PV System equipped with various AI prevention schemes such as over-current and under-current (OI/UI), over-voltage and under-voltage (OV/UV), over-frequency and under-frequency (OF/UF), rate of change of frequency (ROCOF) and Vector Shift. These scenarios are used in order to evaluate and determine the performance of the AI detection methods and select the most appropriate AI detection algorithm and its corresponding settings for Grid-Connected PV Systems.
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Why is it important?
The anti-islanding (AI) protections was tested in case of complete disconnection of the photovoltaic (PV) system from the electric power grid and also in case of various grid faults. However, the detailed simulation results are presented only for the first study case. The theoretical simulation results are useful to design the AI protection devices for Grid-Connected PV Systems and select the points where islanding conditions may occur and the AI relays should to be inserted.
Perspectives
From the results provided by the performed Matlab and Simulink simulations, it was observed that using traditional relays for islanding detection such as the over-current (OC) or under-voltage (UV) resulted in significantly better performance in respect to detection time of islanding conditions. The rate of change of frequency (ROCOF) and Vector Shift relays have a detection time comparable with frequency relays. However, if the ROCOF threshold is exceeded, the formation of an island is quickly detected. The effects of unintentional islanding were observed from simulation of transient grid faults on a power distribution network. The protection equipment needs to distinguish between islanding event and grid faults. The Grid-Connected PV System protections should detect the fault and trip before islanding occurs as a result of the opening of the circuit breaker in response to a downstream fault.
Dr Ioan Viorel Banu
Universitatea Tehnica Gheorghe Asachi din Iasi
Read the Original
This page is a summary of: A study on anti-islanding detection algorithms for grid-tied photovoltaic systems, May 2014, Institute of Electrical & Electronics Engineers (IEEE),
DOI: 10.1109/optim.2014.6850940.
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