Active Frequency Drift Method for Islanding Detection Applied to Micro-inverter with Uncontrollable Reactive Power

Abstract

This paper proposes active frequency drift (AFD) as an anti-islanding method applied to micro-inverters with uncontrollable reactive power. When using ordinary inverter topologies, such as full bridge inverters in photovoltaic systems, the islanding phenomenon can be detected with reactive power-based methods, such as reactive power variation. However, when the inverter topology cannot control the reactive power, conventional anti-islanding methods with reactive power cannot be utilized. In this work, the topology used in this paper cannot control the reactive power. Thus, an anti-islanding method that can be used in topologies that cannot control the reactive power is proposed. The conventional anti-islanding method of the topology that cannot control reactive power is introduced and analyzed. Unlike the conventional AFD method, the proposed method extends a zero current interval every predetermined cycle. The proposed method offers certain advantages over conventional AFD methods, such as total harmonic distortion. The proposed method is validated through simulation and experiment.

Comparative study of active anti‐islanding schemes compatible with MICs in the prospect of high penetration levels and weak grid conditions

“…This is because very few of these works refer to the MIC technology, whereas only a limited number of the referenced methods are directly compatible with Pdc-MICs. The inherent unitary displacement power factor (DPF) of this technology (Pdc-MICs) is the main barrier for the implementation of most of the active schemes, not allowing the formation of harmonic currents and hindering the implementation of frequency drift techniques, such as the method in [14], active frequency drift (AFD) in [15], Sandia frequency shift (SFS) in [16], and SMS slipmode frequency shift (SMSFS) in [8]. Moreover, the unidirectional power flow nature of those topologies disallows the reactivevariation-based techniques, like the one in [17].…”

“…Rest of referenced works (i.e. [15,21,22]) that exclusively refer to the islanding protection of MICs consider only the category of MICs with dc-link. However, those kinds of MICs are easier to deal with, because they resemble a conventional two-stage voltage-source inverter with a front dc-dc converter to regulate the dc-link.…”

Islanding Detection of Synchronous Distributed Generator Based on the Active and Reactive Power Control Loops

“…In reference [16] a specific current harmonic is injected intentionally to the system which can be measured in islanding situation. Some of active methods which have been implemented for inverter-based generators include active frequency drift (AFD) [17][18][19][20][21], Sandia voltage/frequency shift (SVS and SFS) [22], and slip-mode frequency shift [23]. The active methods have high probability of interference with other devices and non-linear loads.…”