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3. Battery bank
The battery bank consists of 240 Lead-Acid batteries each
of rating 2 volts, 1000 Ampere/hour. These batteries are
connected in series to create an output voltage of 480V.
Operation Mechanism
in order to provide uninterrupted power supply to the
domestic load of the estate, the backup power of Grid/DG
set was attached to the battery bank.
The idea is that, when solar radiation is high enough i.e. during
the day time, the solar modules will supply the load demand
and charge the battery as well.The DC supply will go through
a MPPT charge controller and be fed directly to the battery
bank, then go through one iGBT inverter to convert into AC
supply and feed the load as well. when the solar radiation is
not there i.e. at night, the battery bank will supply power to
load through the same iGBT inverter. if there is no sunshine
to charge the battery i.e. in case of rain, cloudy weather etc and
the battery gets discharged, it will take power automatically
from the Grid supply or DG set, whichever is available, through
a rectifier. This entire switching operation is automatic and
controlled by the PCU itself.
The following diagram shows how it works:
Battery Bank
Solar Panels
400 solar modules
2 Main Junction Boxes
25 strings (16 modules each)
6 Array Junction Boxes
DC supply from solar modules
MPPT based charge
controller
IGBT inverter
Bus bar
Grid /DG
set supply
DOMESTIC LOAD PANEL
NeoWatt Sunbird
3000 PCU inverter
Rectifier
480V AC supply
Battery
bank
JULY 2015 43
The plant comprises 3 main components:
1. Solar PV modules
Silicon Polycrystalline 250 watt Peak modules, each
consisting of 60 cells arranged in 10x6 patterns. Degree
of inclination: 25O; Total no. of modules: 400; Directional
Facing: South East
Dimension and rating of each module/panel:
Length – 1640 mm; Breadth: 982 mm; Thickness: 36 mm
Rated power: 250 watt (Peak)
Open Circuit Voltage: 37.08 Volts
Short Circuit Current: 8.53 Amps; Fill Factor: 79.17%
Arrangement: 16 solar modules are connected to create
one string and 25 strings are connected to six Array
Junction Boxes; these AJBs are then connected to two
Main Junction Boxes. The input supply from these
MJBs goes into the inverter PCU.
2.
NeoWatt Sunbird 3000 Inverter System
Neowatt Sunbird 3000 is a three phase bi-directional
MPPT based inverter/charge controller system which
can operate parallel to an
AC input source.
The main components of
this PCU are:
a) Maximum Power Point
Tracking based Charge
Controller
b) insulated Gate Bipolar
Transistor
c) Rectifier
d) Bus Bar
e) Dot Matrix Display
Sunbird Inverter System