A wavelet-based hybrid islanding detection system applied for distributed generators interconnected to AC microgrids

Review of Local Network Impedance Estimation Techniques

“…For example, [11], [13], [14] inject a noncharacteristic harmonic current of 75 Hz periodically. The settled values of current and voltage are recorded and converted into the frequency domain with Fourier transform analysis (or wavelet transform as per [11]). The voltage and current values at 75 Hz are extracted and the impedance is calculated with Z n (ω h ) = R n + jω h L n (where ω h is the nonharmonic frequency).…”

“…Park More recently, some researchers have explored using the Wavelet Transform (WT) as an alternative to FFT [11], [86].…”

“…With the advancement of microcontroller computational capabilities, online impedance estimators became increasingly common in the literature. Anti-islanding is a common motivation for impedance estimation literature [11]- [16], with the draft European standard EN50330-1 (or equivalent German standard VDE0126) usually cited as a justification. For completeness, EN50330-1 is now cancelled, and the current standard regarding islanding prevention is EN62116, Utility-interconnected photo-voltaic inverters -Test procedure of islanding prevention measures [17].…”

A Support Vector Machine Based Technique for Fault Detection in A Power Distribution Integrated System with Renewable Energy Distributed Generation

“…The passive methods including frequency variations [13,14], degree of alteration of power frequency [15], power and voltage variation ASTESJ ISSN: 2415-6698 [16], energy mismatch and harmonic content recognition [17] and the degree of variation of reactive power [18], these techniques were applied in power grid integrated network for fault diagnostic. Moreover, undetected faults have an undesirable effect on the overall performance of the power grid, the active algorithms used for fault diagnostic includes frequency signal injection [19], singular and dual harmonic current injection [20,21], output power variation [22], reactive power control [23,24], and the impedance measurement method [25,26], these methods were used to detect faults in power grid integrated network with REDGs.…”

An Islanding Detection Technique for Inverter-Based Distributed Generation in Microgrids

“…Passive schemes decide based on the local measurements and predefined thresholds without any changes in MGs, while active schemes usually inject perturbations to MGs to decide based on the consequent changes in local measurements [15,16]. A hybrid scheme is a combination of passive and active schemes [17,18]. Among the various local islanding detection schemes, passive schemes have the lowest cost, lowest complexity, and highest detection speed and, unlike active schemes, do not have negative effects on power quality [6].…”