Ac Coupling - Conext XW+ 6848 NA Owner's Manual

Introduction

AC Coupling

1–8
Off-grid AC Coupled system architecture is often used to create a stand-alone
grid. Commonly this means that PV inverters are connected to the output of a
battery-based inverter/charger putting both on the same AC bus along with the
AC loads. In this scenario, the battery powered inverter charger provides the
necessary frequency and voltage to enable the PV inverter to produce power.
This type of system must be able to maintain power generation in balance with
power consumption at all times. If there is more power being generated than can
be consumed by the loads, power will flow to the inverter/charger and be
converted to DC power which flows into the battery. Once the battery reaches
capacity, power generation by the PV inverter must be curtailed to maintain the
balance between generation and consumption. As the battery bank reaches
capacity, Conext XW+ curtails PV inverter generation by raising the AC line
frequency causing compatible PV inverters to reduce their power output in an
orderly manner. This is called Active Frequency Shift Power Curtailment.
During a grid outage even a home with a grid-tie PV inverter system will be
without power because PV inverters cannot produce power without the presence
of a reference voltage and frequency. To enable the PV inverter to provide power
during a grid outage the Conext XW+ is retrofitted in front of the PV inverter. The
PV inverter is rewired from the grid connection to a critical load (sub) panel and
the AC Couple is on the Conext XW+ AC Output port. When the grid is present,
PV inverter power feeds the loads and any excess is exported by Conext XW+ to
the grid using AC1 (where permitted by the local utility). During a grid outage,
Conext XW+ anti-islanding protection prevents power from being exported to
grid on AC1. Conext XW+ then uses Active Frequency Shift Power Curtailment to
reduce the power output of compatible PV inverters, maintaining the balance of
generation and consumption.
Consult the manufacturer's specifications to determine if your PV inverter is
compatible with Active Frequency Shift Power Curtailment. Conext XW+ AC
coupling function is enabled by default (Advanced Features Menu).
AC COUPLED PV INVERTER COMPATIBILITY
AC power generated by AC coupling PV inverters with Conext XW+ must be
consumed by AC loads or used to charge batteries. As an alternative, the
excess power produced from a PV inverter can be routed to dump loads. Do
not AC couple PV inverters with the Conext XW+ that are unable to reduce,
derate or cease the excess PV inverter power in response to the changes in
AC line frequency controlled by the Conext XW+. Consult the manufacturer's
specifications of your PV inverter and confirm compatibility.
Failure to follow these instructions can result in equipment damage.
The AC coupling advanced setting should remain enabled except in cases when
the DC voltage level is allowed to have large variations and the line frequency
needs to remain constant.
NOTICE
975-0240-01-01