I work for a small utility company in the US. In the past, distributed generation (DG) interconnections have been rare on our system. Now, because of new customer incentives and direction from the Public Service Commission, DG installations are becoming much more prevalent in the area. These installations are most often small inverter-based PV installations; however, small synchronous or induction machines (such as wind turbines or cogeneration systems) have also been seen. We expect penetration of distributed resources to drastically increase within the next few years.

As we review customers' interconnection requests, the possibility of islanding has become a major concern. The inverter-based DG installations utilize various anti-islanding algorithms to mitigate this problem. Nevertheless, each method has a NDZ (non-detection zone)- a loading condition which could result in a sustained unintentional island. Furthermore, as DG penetration increases, there is concern that the anti-islanding methods may become ineffective or even work against each other in areas where multiple DG types are installed.

What methods are used to determine if unintentional islanding is possible with a DG system? Alternatively, are there conditions under which one can definitely conclude that islanding will not occur? What do you feel are the most effective anti-islanding algorithms for a highly penetrated system?

Thank you!

Current live consultation on this Here

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mikek