GFM
Grid-forming inverter
An inverter controlled as a voltage source that sets its own voltage and frequency, able to energise and hold up an island.
SLD
Functional block · MRAT
Microgrid reactive-control authority transfer
Functional block · Microgrids
An independently authored application reference. The drawing shows the named function or circuit relationship; use the project legend and selected equipment documentation for its drafting form and connections.
Browse this installation focusIn plain English
What this block does
Coordinates a documented change in ownership of the voltage-support objective.
A simple example
In an islanded microgrid, the assigned reference source supports bus voltage while other compatible resources share reactive demand according to the selected control method. Grid-connected operation can use a different objective at the PCC. For this reference, the drawing identifies “Old and new controller availability” at the input and “Selected reactive-control authority” at the output. A smooth transfer requires a validated control strategy.
What the drawings help you do
Start at the named input: Old and new controller availability. Identify its source device or document and the state represented on the drawing. Follow the named output: Selected reactive-control authority. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Old and new controller availability
- Output
- Selected reactive-control authority
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: Microgrid control systems
Schematic · MRAT
What it represents
Coordinates a documented change in ownership of the voltage-support objective. Voltage and reactive-power control coordinate the AC operating condition of the microgrid resources. A voltage target, reactive-power target and power-factor target represent different control objectives and should have explicit ownership.
In an islanded microgrid, the assigned reference source supports bus voltage while other compatible resources share reactive demand according to the selected control method. Grid-connected operation can use a different objective at the PCC. For this reference, the drawing identifies “Old and new controller availability” at the input and “Selected reactive-control authority” at the output. A smooth transfer requires a validated control strategy.
Show each measured quantity, target and resource capability limit. Control-loop tuning, equipment capability and parallel operation require a validated design rather than an assumed property of the symbol. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.
How to read it
- Start at the named input: Old and new controller availability. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Selected reactive-control authority. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- A smooth transfer requires a validated control strategy.
- Show each measured quantity, target and resource capability limit. Control-loop tuning, equipment capability and parallel operation require a validated design rather than an assumed property of the symbol.
Information to show or reference
- Label the source and connection reference for old and new controller availability.
- Identify the destination and defined state of selected reactive-control authority.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: A smooth transfer requires a validated control strategy.
A distinction that matters
A smooth transfer requires a validated control strategy. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Microgrid control systems
Public technical context for microgrid voltage and reactive-power controls. Active and reactive power, generation, load control, operating reserves and system supervision. The application text and educational graphic are independently authored; the publisher does not certify this representation.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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