User Guide

Surplus Power in Off-Grid/Backup Mode
The most critical element of AC coupling is the use of the surplus power that the PV system
produces when operating in off-grid or backup mode. The surplus power is the power that is
not used by the loads. For instance, if the PV inverter produces 4 kW and the load is 1 kW,
there is a surplus of 3 kW.
Figure 2Grid Forming and Surplus Power
AC Critical Load
Panel
PV Inverters
tuptuO
PVtuptuO retrevnI
W+X
XW+ Inverter/Charger
If there is more power being generated than can be consumed by the loads, the surplus
power will flow to the Conext XW+ and will be converted to DC power which flows into the
battery. Once the battery reaches full charge, power generation by the PV inverter must be
curtailed to maintain the balance between generation and consumption. As the battery bank
reaches full charge, Conext XW+ curtails PV inverter generation by raising the AC output
frequency, causing compatible PV inverters to reduce their power output. This is called
Frequency Shift power curtailment.
NOTICE
RISK OF EQUIPMENT DAMAGE
Follow all instructions related to AC Coupled PV sizing, battery sizing, and charge settings in
the following sections of this document.
Failure to follow these instructions can result in equipment damage.
976-0240-01-01 Revision G This document is intended for use by qualified personnel 6
Conext XW+/SW Battery Inverters and PV Solutions Guide