This paper presents the analysis and comparison of the main active techniques for islanding detection used in grid-connected single phase inverters. These techniques can be divided into two classes: techniques introducing positive feedback in the control of the inverter and techniques based on harmonic injection by the inverter. The algorithms mentioned in this work are simulated in PSIMTM in order to make a comparative analysis and to establish their advantages and disadvantages according to IEEE standards.
Single phase inverter
Active Islanding Detection Methods
Fig.1. Block diagram of the developed inverter
EXPECTED SIMULATION RESULTS:
Fig. 2. (a) Active power injection. PCC voltage, RMS Voltage and islanding detection. (b) Reactive power injection. PCC voltage, frequency and islanding detection.
Fig. 3. GEFS. PCC voltage, frequency and islanding detection.
Fig. 4. Impedance detection. PCC voltage and islanding detection.
In this paper was presented an analysis of various active methods resident in the inverter for islanding detection in single phase inverters. It became evident that for the same test conditions as established by the IEEE 929 all methods met, however the positive feedback based methods have a longer trip time that those based on harmonic injection because positive feedback methods should reach the threshold of UOV or UOF, whereas methods based on harmonic injection what is sought is to detect variations in the impedance of the grid, which allows to work with smaller detection thresholds. On the other hand, despite these methods are based on disturbing the system and degrading the power quality, their effect is not significant and they are within the harmonic distortion limits set by standards.
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