This is a report on the development of anti-islanding control for grid-connected inverters from distributed generation sources. Islanding occurs when a distributed generation source continues to provide electricity to a portion of the utility grid after the utility experiences a disruption in service. Since the utility no longer controls this part of the distribution system, islanding can pose problems for utility personnel safety, power quality, equipment damage, and restoration of service. This report proposes a new family of anti-islanding schemes that meet IEEE 1547 interconnection standards, that can detect all disruptions in service, have minimum power-quality impact, require low-cost implementation, work for multiple distributed generators, and work for any multi-phase inverters. It also provides design guidelines for the schemes, and evaluates and validates the proposed schemes for practical applications.

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Study and Development of Anti-Islanding Control for Grid-Connected Inverters

Recently there has been a resurgence of concern about islanding of grid-connected photovoltaic (PV) systems. This condition occurs when the PV system continues to energize a section of the grid after that section has been isolated from the main utility voltage source. Generally, islanding is undesirable because it poses a safety hazard to utility service personnel, and also because it can lead to asynchronous reclosure which can damage equipment. It is therefore important that PV systems incorporate methods to prevent islanding. The purpose of this paper is threefold: (1) to critically review the literature on islanding prevention methods for PV systems and discuss their strengths and shortcomings; (2) to review and analyze the islanding behavior of four converters which are prominent in the literature in order to demonstrate the implementation and effectiveness of some islanding prevention methods; and (3) to introduce a new islanding prevention scheme, active frequency drift with positive feedback, which overcomes many of the shortcomings of existing schemes. It is concluded that no ‘perfect’ islanding prevention method yet exists, but also that many existing methods or combinations thereof work very well in practical situations. Finally, it is noted than an investigation of what constitutes ‘sufficient’ islanding prevention is needed. Copyright © 1999 John Wiley & Sons, Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/%28SICI%291099-159X%28199901/02%297%3A1%3C39%3A%3AAID-PIP246%3E3.0.CO%3B2-J

Prevention of islanding in grid‐connected photovoltaic systems

Unintentional islanding protection of distributed generation is a key function for standards compliance. For those distributed generations that use an inverter as grid interface, the function can be implemented as part of the inverter control. Existing antiislanding schemes used in inverters have power quality and nondetection zone issues. This paper proposes a new family of schemes that have negligible power quality degradation and no nondetection zone. Design guidelines based on frequency-domain analysis is also provided. Finally, both simulation and experimental results validate the proposed schemes.

A new family of active antiislanding schemes based on DQ implementation for grid-connected inverters

Modeling anti-islanding protection devices for photovoltaic systems

Unintentional islanding of distributed generation (DG) cause negative impacts on distribution systems and must be detected within acceptable durations. To certify the anti-islanding performance of DG systems, IEEE Std. 929-2000 [1] issued a standardized test procedure to distinguish an inverter with an adequate anti-islanding technique from those without. Lab testing is an effective way to judge the anti-islanding performance, although the process is time costing and any little mistake (like poor tuned RLC load) may mislead the judgement. This makes anti-islanding schemes comparison difficult. Non-detection zone (NDZ) is an effective performance index to evaluate anti-islanding schemes. This paper proposes a novel NDZ mapping method that set up relations between NDZ and IEEE Std. 929-2000 testing requirement. It maps the NDZ into load space that characterized by "power quality" and load capacitance. Based on the NDZ plot, not only the dominate factors that influence anti-islanding protection performance can be identified, but also optimized parameter setting of the anti-islanding schemes can be deduced, that helps to achieve the "non-islanding inverter" as well as least potential adverse impact on power quality.

Analysis and optimization of active frequency drift islanding detection method

The authors have successfully developed and industrialized a new frequency-shift anti-islanding protection method using a twin-peak band-pass filter (BPF) for grid-interconnected photovoltaic (PV) power systems. In this method, the power conditioner has a twin-peak BPF in a current feedback loop in place of the normal BPF. This new method works perfectly for various kinds of loads such as resistance, inductive and capacitive loads connected to the PV system. Furthermore, because there are no mis-detections, the system enables the most effective generation of electric energy from solar cells. A power conditioner equipped with this protection was officially certified as suitable for grid-interconnection.

A. Takeoka

Papers

Anti-islanding protection using a twin-peak band-pass filter in interconnected PV systems, and substantiating evaluations