Islanding is the condition in which a distributed generator continues to power a location even though electrical grid power is no longer present. Islanding can be dangerous to utility workers, who may not realize that a circuit is still powered, and it may prevent automatic re-connection of devices. Additionally, without strict frequency control the balance between load and generation in the islanded circuit is going to be violated, leading to abnormal frequencies and voltages. For those reasons, distributed generators must detect islanding and immediately disconnect from the circuit; this is referred to as anti-islanding. Microgrids are designed to allow for intentional islanding. In case of an outage, a microgrid controller disconnects the local circuit from the grid on a dedicated switch and forces the distributed generator(s) to power the entire local load. The microgrid controller must then synchronize generators and balance the generators and loads. Methods that detect islanding without a large number of false positives are an important aspect of this technology. Each detection method has some threshold that needs to be crossed before a condition is considered to be a signal of grid interruption, which leads to a "non-detection zone", the range of conditions where a real grid failure will be disregarded. For this reason, grid-interactive inverters are typically tested before field deployment by reproducing specific grid conditions and evaluating the effectiveness of the islanding methods.
| Corporation | Patents and Published Applications Count |
|---|---|
1.
ABB Schweiz
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2.
General Electric Company
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3.
Hitachi
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| 4. Enphase Energy Inc [us] |
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5.
Siemens
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6.
Schneider Electric
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7.
Virginia Tech Intellectual Properties, Inc.
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8.
Sma Solar Technology
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9.
Dynapower Company Llc
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10.
Kyocera Corporation
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| Categorization and Classification | Patents and Published Applications |
|---|---|
| 6 | |
| 6 Testing | |
| 232 | |
| 232 Detection | |
| 71 | |
| 71 Disconnect | |
| 86 | |
| 86 Microgrid Sync | |
| 12 | |
| 12 Protection | |
| 5 | |
| 5 Solar | |
| 12 | |
| 12 Wind | |
| 17 | |
| 17 Reclose | |
| 2 | |
| 2 Prevention | |
| 27 | |
| 27 Gen/Load | |
