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1

An experimental study for the islanding detection by the harmonic distortion method and protection system of the inverter

Osmanaj Sabrije, Limani Myzafere, Sylejmani Bardhyl

Przegląd Elektrotechniczny

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2019

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R. 95, nr 4

232--236

EN

In this paper is analyzed is the passive technique of the voltage Harmonic Distortion (HD) for the protection and distribution of PV systems connected to the utility grid. We have made the measurement of the HD voltage in the PCC and the measured value is compared with a certain threshold if this threshold is exceeded inverter will be disconnected. During normal operation, the voltage at the PCC is the grid voltage, so distortion in most cases can be considered as negligible. However, when islanding condition happens, the current harmonics produced by the inverter are transmitted to the load and presents higher impedance than the grid. The interaction of the harmonic currents and the grid impedance generates voltage harmonics which can be measured. Therefore, the voltage HD variations beyond a certain threshold can be used to detect islanding. The technique in question is analyzed based on the non-detection area and based on the possibility of degradation of the output power quality, which is a known weak point of this method. The analysis focuses on the worst case of detecting when the energy produced by the photovoltaic system is the same energy that takes the load when there is no change to the parameters at the common point of connection to the utility grid. Results are obtained by monitoring a grid connected to the photovoltaic system with a power of 3.9 kWp installed on a flat roof of a laboratory building of FECE in Pristina. Simulations for the respective topology were made with Matlab Simulink.

PL

W artykule analizowany jest system fotowoltaiczny podłączony do sieci z pasywnym układem poprawy zawartości harmonicznych. W układzie moerzona jest zawartość harmonicznych I układ jest odłączany gdy ta wartość przekroczy dopuszczalny poziom. Jednocześnie przekraczanie zawartości harmonicznych może być sygnałem zjawiska wyspowania.

2

Research on islanding detection of solar distributed generation based on best wavelet packet and neural network

Xi Zhongmei, Zhao Faqi, Zhao Xiangyang, Peng Hong, Xi Chuanxin

Archives of Electrical Engineering

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2019

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Vol. 68, nr 4

703--717

EN

The active distribution network (ADN) represents the future development of distribution networks, whether the islanding phenomenon occurs or not determines the control strategy adopted by the ADN. The best wavelet packet has a better time-frequency characteristic than traditional wavelet analysis in the different signal processing, because it can extract better and more information from the signal effectively. Based on wavelet packet energy and the neural network, the islanding phenomenon of the ADN can be detected. Firstly, the wavelet packet is used to decompose current and voltage signals of the public coupling point between the distributed photovoltaic (PV) system and power grid, and calculate the energy value of each decomposed frequency band. Secondly, the network is trained using the constructed energy characteristic matrix as a neural network learning sample. At last, in order to achieve the function of identification for islanding detection, lots of samples are trained in the neural network. Based on the actual circumstance of PV operation in the ADN, the MATLAB/SIMULINK simulation model of the ADN is established. After the simulation, there are good output results, which show that the method has the characteristics of high identification accuracy and strong generalization ability.

3

An experimental study of passive methods for islanding detection and protection system of the inverter operation

Osmanaj S., Sylejmani B., Limani M., Selimaj R.

Przegląd Elektrotechniczny

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2018

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R. 94, nr 2

118--123

EN

In this paper, we analyze the method of passive over/under voltage for protection and distribution of PV systems connected to the utility grid. The method in question is analyzed by non-detection area and based on the possibility of degradation of output power quality, which is a known weak point of this method. The analysis focuses on the worst case detection when the energy produced by the photovoltaic system is the same energy that takes the load when there is no change to the parameters at the common point of connection to the utility grid. An algorithm is proposed to solve the problem of the creation of the so-called islanding of generators connected to the grid. Simulations were conducted with Matlab Simulink software.

PL

W artykule analizowano pasywną metodę detekcji pracy wyspowej z wykorzystaniem zabezpieczenia nad/pod napięciowego w przypadku systemu dystrybucyjnego zawierającego system PV. Analizowano obszary nie-wykrywania zagrożeń. Skoncentrowano się na najgorszym przypadku, w którym energia wytwarzana przez system fotowoltaiczny jest w całości pobierana przez odbiór, podczas gdy nie występują zmiany parametrów w punkcie wspólnego przyłączenia do sieci elektroenergetycznej. Przedstawiony algorytm rozwiązuje problem kryteriów dla detekcji pracy wyspowej jednostek wytwórczych przyłączonych do systemu elektroenergetycznego.

4

Synchrophasor based Islanding Detection method

Barczentewicz S., Borkowski D.

Przegląd Elektrotechniczny

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2015

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R. 91, nr 11

98-101

EN

Unintentional islanding is one of the most disturbing issues of distributed generation. It has serious consequences for electricity and it poses a threat to life and health of the personnel. This paper makes a comparison between two islanding detection methods. The first method is the well known over/under voltage and over/under frequency passive method. The second method is a synchrophasor based method. The simulations proved that the two studied methods have a good performance for parallel RLC.

PL

Nieoczekiwane występowanie pracy wyspowej jest jednym z głównych problemów generacji rozproszonej. Praca wyspowa może mieć wpływ na jakość energii elektrycznej i stwarza poważne zagrożenie dla życia i zdrowia personelu. Ten artykuł porównuje dwie metody detekcji pracy wyspowej. Pierwsza metoda to dobrze znana metoda pasywna OUV/OUF (over under voltage and over under frequency). Druga metoda oparta jest na pomiarze synchrofazora. Symulacje wykazały, że obie metody sprawdzają się dla równoległego obciążenia RLC.