BOSS – Installation, Operation and Maintenance Manual
A l e n c o n S y s t e m s L L C - P a g e
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12
Ground Leak Detection
Many installed PV systems are negatively grounded at the suggestion of the PV panel
manufacturer (though some PV panels do require positive grounding). Additionally, guidance
from the National Electrical Code (NEC) and certain AHJ rulings also encourage PV arrays to be
grounded, as opposed to being allowed to “float.”
By contrast, today’s large-scale battery energy storage systems are generally “floating” or
ungrounded. Alencon’s BOSS leverages the inherent properties of galvanic isolation to provide
the customers with a “
Ground leak Detection
” feature.
By continuously monitoring the system's differential voltage, BOSS ground-fault detectors can
provide early indication of ground faults before leakage becomes prominent. Galvanic isolation
of each battery rack allows each DCDC to measure the isolation resistance from a positive
battery terminal (BAT 1) and negative battery terminal (BAT2) to the earthed chasses and
compute the leakage current from these terminals.
If the leakage current becomes excessive the ESS may disconnect the DCDC and associated
rack from the system.
Communication
The DC units communicate among themselves and with the ESS controller via an industry
standard MODBUS RTU protocol. (An optional MODBUS TCP-IP is available via PODD
communication controller). The ESS controller collects the SOC and SOH information from the
BMS associated with batteries in the racks as well the power information from the inverter and
DC Bus. Based on this information ESS controller assigns the magnitude of the charge or
discharge current to each DCDC. The purpose is to keep the same SOC on each rack
regardless of its SOH. This way all battery racks can be fully charged and discharged at the
same time, thus assuring full utilization of battery capacity.
Parallel Operation
Each DCDC is designed for a specific maximum current. If a battery rack requires more current
than a DCDC can provide, two or more DCDC may be paralleled. Each DCDC should be
provided with a separate fuse and disconnect. The ESS controller should be programmed to
recognize BOSS configuration.
