Inverter control rooms

What an inverter control room is, how many the plant gets, where they are placed, the tables they clear, and how to move one by hand.

An inverter control room (ICR) is the building where the plant's collection cables terminate and its medium-voltage export begins. In a String Inverter plant the inverters stand out in the field and run their AC cables into it. In a Central Inverter plant the central inverters themselves stand inside it.

The application places the rooms for you. It works out how many the plant needs from the capacity block you set, groups the tables around them, and clears the tables each room stands on. You can then move any room by hand if the ground does not suit it.

The footprint

A control room is drawn and cleared as a rectangle with a height, and all three dimensions are yours to set in the Structures & Shadow group.

Dimension	Default	What it is
Length	10.0 m	The building's east–west extent
Width	4.0 m	The building's north–south extent
Height	5.0 m	Drives the shadow the building casts

Length is always the east–west side and width the north–south side, for the control room and for every other structure in that group. Enter the building you are actually going to build: the footprint is what clears tables, and the height is what casts the shadow. See Structures and shadow.

How many the plant gets

The count comes from one field. ICR Block on Site parameters is the capacity one control room serves, in MWp, and defaults to 18.0 MWp with a range of 0.1 to 500.

The number of rooms is the plant's capacity divided by the block size, rounded up. A plant of any capacity therefore gets at least one room, and a plant that overshoots a block boundary by a small margin gets a whole extra room — which is worth checking against your own single-line concept before you accept it.

Set the block size to the capacity your transformer and switchgear design actually serves. It is the single most consequential number on this page: it sets how many buildings the plant carries, how the tables are grouped around them, how far the AC runs are, and how many medium-voltage circuits leave the plant.

Where they go

The rooms are placed after the table grid, once the plant's capacity is known, and their positions come from where the tables actually are rather than from a geometric division of the site.

Tables are grouped spatially by position into blocks of roughly one block-size each. A control room is then placed at the centre of each group. The result is that every group of tables surrounds its own room, and the room sits near the middle of the load it serves — which is what keeps the AC runs from that group short.

Each room must fit entirely inside the usable area, the same rule the tables follow. A position that would put part of the building in the perimeter road band, in a water body, in a transmission line corridor or on excluded ground is not used. See How placement works.

Screenshot pendinglayout/icr-detail.png

A control room among the tables

What it shows: A zoomed view of a single control room, showing its label and the gap in the table grid where it sits.
How to get there: Generate a layout, then zoom into one control room.
Callouts to add: Outline the control room and label the cleared gap.

The tables a room clears

Any table overlapping a control room's footprint is removed. The building wins; the ground under it and the ground its footprint touches carry no structures.

That has a consequence the order of the pipeline has to deal with. Removing tables lowers the plant's capacity, and the number of rooms was worked out from the capacity before the removal. So the count is re-checked against the new, lower capacity once the footprints have been cleared. If the reduced capacity no longer justifies the last room, the plant does not carry it.

This is why the room count and the table count in the summary are consistent with each other rather than with a figure you would get by dividing the site area by the block size.

Moving a control room by hand

The automatic position is derived from the tables. It knows nothing about where the site road reaches, where the ground is firm enough for a building, where the existing site access is, or where the owner will allow a structure. When one of those decides the position, move the room.

Leave the pan and zoom tools inactive

Dragging a room only works when no navigation tool is holding the mouse. If pan or zoom is active, switch it off first — otherwise the click pans the plot instead of picking up the building.

Click and hold the room

Click the dark blue rectangle and keep the button down. Fit the view first with Home (⌂), then zoom into the room you want, so you are picking up a building and not a table beside it.

Drag it inside the perimeter road and release

Drop it anywhere the whole footprint stays inside the plant — inside the perimeter road, clear of the exclusions. On release the layout rebuilds around the new position.

Check what came back

An invalid drop snaps back to where the room started, so a room that returns to its original position was dropped somewhere it cannot stand. A valid drop rebuilds the layout, so the tables the room used to clear come back and the tables at the new position go away.

Screenshot pendinglayout/icr-drag.png

Dragging a control room

What it shows: The moment during a drag when the control room has left its original position — the cursor and the room's new position both visible.
How to get there: With no pan or zoom tool active, click and hold a control room and drag it. Capture during the drag.
Callouts to add: Arrow from the original position to the new one.

Moving a room away from the centre of its group of tables lengthens every AC run from that group. If cable lengths matter to your estimate, re-check the cable columns in the summary after the move rather than assuming they are unchanged.

In Central Inverter mode

The building's role changes with the electrical topology, and so does what it contains.

String inverters stand out in the field, in the gap bands between rows. DC string cables run from the tables to the inverters, and each inverter's AC cable runs to the nearest control room, where the medium-voltage circuit that leaves the plant begins.

Either way, the medium-voltage cables leave the control rooms and run to the main control room, sharing a trunk where their routes converge rather than running parallel lines. See Cable routing.

On a site with several plant boundaries, each plant's rooms route their medium-voltage cables to a unit substation in their own plot instead. See Multi-plot sites.

The shadow a control room casts

A 5 m building next to a row of modules shades it. The application computes the year-round shadow footprint of every control room, main control room and placed object over the Shadow Window — the band of solar hours you care about, 9.0 to 16.0 by default — and, with Clear tables inside shadows on, removes the tables that fall inside it.

That option is on by default, so a first run already keeps tables out of building shadows. Switching it off leaves shaded tables in place, which raises reported capacity and makes the yield estimate optimistic for those rows. Change the room's height and the shadow footprint changes with it.

The fields that decide a control room

Four fields, in two groups, decide everything about the rooms in a plant:

Field	Group	What it decides
ICR Block	Site Parameters	How many rooms the plant carries, and therefore how the tables are grouped around them
ICR length, width and height	Structures & Shadow	The footprint that clears tables, and the height that casts the shadow
Clear tables inside shadows	Structures & Shadow	Whether the tables inside a room's year-round shadow are removed
Shadow Window	Structures & Shadow	The band of solar hours the shadow footprint is accumulated over

Nothing else moves a room. In particular, the perimeter road width and the obstructions change where a room may stand, but never how many there are.

Checking the rooms after a run

Four things are worth a look before you accept a layout:

The count against your electrical concept. The ICR column is the number the capacity block produced. If it is one more than your single-line concept expects, the plant has overshot a block boundary — adjust the block size, or accept the extra building.
Where each room landed. Zoom into each one. A room at the centre of its group of tables is what you want; a room pushed to one side of its group is usually a room that had nowhere else to fit, and it is the first candidate for a hand move.
Whether the ground is buildable. The application knows the boundary, the exclusions and the slope limits. It does not know where the site access road will run, or where the ground is firm. Those are yours to check.
The gap the room left. Turn on ▢ Wireframe and look at the cleared footprint. If it is much larger than the building you intend, the length and width fields are set to something you did not mean.

What the summary reports

The ICR column carries the count of rooms for each plant, and the TOTAL row carries the count for the site. In String Inverter mode the AC cable column is the total length of the runs from the inverters into the rooms; in Central Inverter mode it is replaced by the DC trunk length into them. Every column is listed in Summary table columns.

The exported PDF report goes further than the summary table: its inverter and cable page breaks the cable lengths down per control room, which is the view to take to a cable schedule. See The PDF report.