900-00277-01-001 Rev A
35
Operation
AC Coupling
NOTE:
This function is performed automatically when the conditions are met as described below.
It has no adjustable settings.
Many inverter products are “grid-direct” (GD), converting PV power to AC power and sending it
directly to the utility grid without the use of batteries. These products have no backup capability.
In systems with an existing GD inverter, the Mojave inverter can be added to “couple” the battery
backup ability to the grid-tied AC system.
Figure 22 AC Coupling
A standard GD system sees the inverter send PV-based power to its main connection
point, the main utility panel
B
. The power then travels back to the utility grid
A
.
If the grid fails, the GD inverter shuts down and is unable to function. Although PV
power may be available, it cannot be used.
In an AC-coupled system, the GD inverter’s main
connection point moves to the subpanel
E
. This is
the location of the Mojave inverter’s protected loads
F
during backup activity.
E
connects to the
inverter’s
L
OAD
terminals at
C
. This means that the
Mojave inverter serves as the GD inverter’s source.
During normal activity, the GD inverter sends power
to
F
and
C
. The inverter’s first priority is to charge
the batteries
D
. (The Mojave battery charger
settings will still apply. See page 44.)
If additional GD power is available, the grid relay
(see page 41) is still closed. Surplus power is sent
to the main panel
B
and on to the grid
A
.
NOTE
: AC coupling affects the inverter’s
performance during
Time of Use
. See page 37.
If the grid becomes unstable, fails, or is otherwise not present, the Mojave
inverter’s grid-protective function (see page 39) will force it to open the grid relay
and disconnect from the grid. With no grid power present:
o
As long as the Mojave inverter is active and providing backup power, the GD
inverter will receive that power and also remain active. It will
continue
producing PV-based power to run the subpanel
E
and any protected loads
F
.
If GD power is not sufficient to run the loads, the Mojave inverter will add
battery power to the production.
If more GD power is available than needed for the loads, the Mojave
inverter will route it to charge the batteries
D
.
If more GD power is available than is needed for either loads or
charging, the Mojave inverter will adjust its output to make the GD
inverter reduce its production. The GD inverter may be required to shut
down temporarily.
GD
A
B
A
GD
B
D
C
F
E
GD
D
C
E
F
