Interconnection of AES With The Grid And Its Considerations Emad-Eldin Mohamed-Ahmed Supervisor: Dr. Tan Chee Wei

AES: Alternative Energy Source EPS: Electrical Power Supply (Grid) Abbreviations AES: Alternative Energy Source EPS: Electrical Power Supply (Grid) PCC: Point of Common Coupling

Islanding AES continues to energize a portion of the area EPS that has been isolated fro the rest of the area EPS Up stream Breaker Fuse Automatic Sectionalizing Switch Manual

Islanding

Interconnection of AES with EPS The interconnection system is the means by which an AES unit connects electrically with the outside Electric Power System (EPS). It can also provide monitoring, control, metering, and dispatch of the AES unit.

Power conversion and conditioning Protection functions

Functions Autonomous and semiautonomous functions and operations AES and load controls. Ancillary services. voltage support, regulation, operating reserve, and backup supply. Communications. Communications allow the AES and local loads to interact and operate as part of a larger network of power systems or micro-grids. Metering. The metering function allows billing for AES energy production and local loads Net Metering FiT

Interconnection Technologies Synchronous Interconnection Induction Interconnection Inverter Interconnection

Standards And Codes IEEE 1547 NFPA 70 UL 1741, 1008, 2200

Considerations of Interconnection Voltage Regulation Maintain approximately constant voltage to users Machines Efficiency. Integration with Area EPS Grounding It is defined by its isolation or lack of isolation from adjacent grounding systems.

Considerations of Interconnection Synchronization To synchronize an AES with an area EPS. Isolation A readily accessible, lockable, visible-break isolation should be located between the area EPS and the AES. These switches provide visible isolation points to allow for safe work practices. Disconnect switches should be strategically installed to permit disconnection from all sources.

Considerations of Interconnection Response to Voltage Disturbance

Considerations of Interconnection Response to Frequency Disturbance When generation is matched inadequately with system load, the area EPS frequency will decline. System operator seeks to match load quickly with available generation. Under-frequency relays are installed on the distribution system to shed load automatically to stabilize operations.

Considerations of Interconnection Disconnection for Faults The AES should have, as a minimum, an interrupting device that is: Of sufficient capacity to interrupt maximum available fault current at its location Sized to meet all applicable ANSI and IEEE standards Installed to meet all local, state, and federal codes

Considerations of Interconnection Loss of Synchronism Result of islanding Transient during reclosing Phase angle separation magnitude across the isolation

Considerations of Interconnection Feeder Reclosing Coordination The AES is designed to cease energizing the area EPS before the reclosing event. The Re-closer is designed to delay reclosing event until AES has ceased energizing the area EPS The AES is controlled to ensure that the voltage phase-angle separation magnitude across the islation is less than one fourth of a cycle when the reclosing event occurs The The Re-closer is controlled to ensure that the voltage phase-angle separation magnitude across the islation is less than one fourth of a cycle when the reclosing event occurs The AES capacity is less than 33% of the minimum load in the feeder.

Considerations of Interconnection DC Injection Dc injection produces a dc offset in the basic power system waveform The increased half cycle voltage has the potential to increase saturation of magnetic components (transformers). This saturation causes increased power system distortion.

Considerations of Interconnection Voltage Flicker The AES has the potential of creating the flicker in voltage AES should not create objectionable flicker for other customers on the area EPS.

Considerations of Interconnection Harmonics

Considerations of Interconnection Unintentional Islanding Protection Undesired for an AES Safety and Power Quality Problems (area EPS and Local Loads) Repair Operations: Pose a threat Repair Operations: Delay of Service Restoration Prevention Limit AES installed capacity Reverse Power Protection at PCC Active anti islanding method (inverter based)

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