3 HOW IT WORKS
The CS inverter is a grid connected photovoltaic power
inverter. It converts the high voltage DC power coming from
the photovoltaïc (PV) panels into AC power. The AC voltage
is fed back into the public utility grid.
A series of PV panels is called a string. One string can be
connected to one solar input of the inverter.
Figure 3-1: Schematic example of the CS inverter in a PV plant
3.1 PV MODULE, STRING, ARRAY AND COMBINER BOX
PhotoVoltaïc (PV) modules convert light into DC power. To
reduce cable losses, PV modules are connected in series: a
so-called “string”. A plane of PV modules is called a PV ar-
ray and consists of multiple strings of the same length, being
connected in parallel. PV strings can be paralleled in a string
(combiner) box. These boxes may provide over current
protection and/ or over voltage (surge) protection, DC
isolating switch and string monitoring functionality.
3.2 GRID CONNECTED INVERTER
See figure 3-1.
The SunMaster CS main task is to convert DC power
produced by the PV modules into AC power and to feed it
back into the public utility grid. The SunMaster CS is not
suitable to be operated in stand-alone mode (independently
from the utility grid). The SunMaster CS has two
independent DC inputs. The PV arrays connected to these
inputs are each operated at their optimum voltage for an
optimal yield (MPP tracking).
3.3 NON-ISOLATED (TRANSFORMERLESS)
The SunMaster CS is a non-isolated (transformerless)
inverter. During operation, it couples the PV array potential to
the utility grid. An optional isolating transformer is available
for applications where galvanic isolation is required
(functional grounding, see chapter 11).
3.4 GRID INTERFACE
The DC PV input is inverted to an AC output: 230/400V AC
(3-Ph/N/PE) output in Wye (Y) configuration. For the PV input
operating voltage range refer to the specifications.
Anti- islanding is provided according to national standards.
The grid interface contains numerous safety mechanisms to
guarantee a level of safety better than an isolated inverter.
Redundant relays isolate the inverter from the grid in case
one of the following circuits detects a fault:
Isolation resistance detection: monitors PV array isolation
resistance.
• RCMU (residual current monitoring unit): monitors and
protects against ground leakage currents.
• DC injection: Monitors DC current injection into the grid.
• Grid voltage- and frequency monitoring
• Anti islanding protection: loss of utility detection
• Low voltage ride through
• Reactive Power
08
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EN / SunMaster CS15TL RP / CS20TL RP / CS30TL RP
DC power
Stringbox CS Inverter
AC power
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