AC Coupling with Microinverter Systems

September 1, 2016
[GRID INTERACTIVE ADVANCED FEATURES]
The next step is to define the logical meters. This is most easily done by hitting ‘Auto-Setup Meter’. Logical meter
definitions are called ‘logical because they are not physical hardware but based on a mathematical expression
containing HEM reported valued. Logical meters are used to record and display the information gathered by the
HEMs. To set up, press the “Manage Power” button. This opens up the logical meter setup. The first UI object is a
pull down menu showing the list of defined logical meters. At first, there are none, so press the “New” button to
add a new logical meter. Typically, you will want to add two logical meter per HEM. One to measure the instant
power and one for the total energy harvested (the sum of powers over time).
EXAMPLE OF LOGICAL METERS FOR NET METERING
Let’s assume you have installed a HEM to measure the entire house consumption (a net meter). Let’s first setup a
power meter. For that, let’s called the new logical meter “Home Power”. Enter that in the appropriate box. Then
select the type as “Cons. Meter” for consumption meter.
Under expression, enter the expression that sums up the two clamp power values. For that, use the “node ID-
clamp-param” pull down box and select “N4-1-W” assuming the HEM node ID is 4. Then press “Insert Device”
and it will add the term in the expression box. Then click on the expression box and a keyboard will pop up. Press
the “+” key to add another term to the expression. Then add the second clamp power measurement by selecting
“N4-2-W” from the pull-down box and press “Insert Device” again. The expression is now complete. In order to
tell the Gateway this is the meter of the entire home (net meter), we check the box “The Net Meter”. Since the
power measurement is an instant measurement, we also check the “Show Gauge Needle” box so that it appears on
the large gauge display on the home page. In addition, we can plot it on the graph by checking the “Plot on Graph”
checkbox.
Now that the Home Power meter is setup, let’s setup the Home Energy meter that measures the total energy ever
consumed (or produced) as well as the daily usage (or production). Again, we press to add a new logical meter.
Under the name, enter “Home Energy”. The type is also “Cons. Meter”. Under expression, enter “(N4-1-kWh)+ (N4-
2-kWh)” to sum up the energy from both clamps. For the energy meter, check the “Energy Measurement” box and
the “The Net Meter” one as well for this example. No need to check the other boxes because the gauge display and
the graph are for displaying power.
VERIFYING THE INSTALLATION
There is a 50% chance that the power measurement for the two clamps will cancel each other leading to
unexpected power measurements. Also, it’s best to follow a consistent convention for export vs. consumption. At
Chilicon, we view (-) negative power as consumption and (+) positive power as production. This can be checked, by
traversing to the following screens, From the home screen, press the Menu button , the hold the UPPER LEFT
CORNER (shown with a green circle), and ENTER PASSWORD “revolution”