Application US20200006945

Anti-Islanding Systems and Methods Using Harmonics Injected in a Rotation Opposite the Natural Rotation
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US20200006945

1. A method of anti-islanding, comprising the actions of: (3) (3)

a) converting power to provide, at output terminals, a multi-phase AC current at a predetermined base frequency, while also

b) adding in a current component, on the output terminals, at the nth harmonic of the predetermined base frequency, with a distinctive phase sequence which is different from that normally present in the nth harmonic;

c) testing whether a voltage corresponding to said nth harmonic and said distinctive phase sequence exceeds a threshold value on the output terminals, and, if so, detecting an islanding condition.

2. The method of claim 1, wherein the nth harmonic is the 5th harmonic, and the distinctive phase sequence is a positive phase sequence. (0)

3. The method of claim 1, wherein the nth harmonic is the 7th harmonic, and the distinctive phase sequence is a negative phase sequence. (0)

4. The method of claim 1, wherein the converting and adding steps are performed by a power-packet switching converter. (0)

5. A system, comprising: (3) (3)

a) at least one local power source;

b) at least one power converter, connected to draw power from the local power source and to drive power onto multiple phase lines of a power bus which is at least sometimes connected to a utility power grid; wherein the power converter also operates to add in a current component, on the output terminals, at the nth harmonic of the predetermined base frequency, with a distinctive phase sequence which is different from that normally present in the nth harmonic; and

c) control circuitry which monitors the voltage on the multiple phase lines of the power bus, and controls the operation of the power converter accordingly; while also testing whether a voltage corresponding to said nth harmonic and said distinctive phase sequence exceeds a threshold value on the output terminals, and, if so, indicating an islanding condition.

6. The method of claim 5, wherein the nth harmonic is the 5th harmonic, and the distinctive phase sequence is a positive phase sequence. (0)

7. The method of claim 5, wherein the nth harmonic is the 7th harmonic, and the distinctive phase sequence is a negative phase sequence. (0)

8. The method of claim 5, wherein the converter is a power-packet switching converter. (0)

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Application US20200006945

Anti-Islanding Systems and Methods Using Harmonics Injected in a Rotation Opposite the Natural Rotation

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