Description Of The Inverter; Multiple-Inverter System; Notes On System Sizing; Inverter Block Diagram - ABB UNO-DM-TL-PLUS-US Product Manual

D
escription of the inverter
M
ultiple-inverter system
N
otes on system sizing
A setup program to help correctly size the photovoltaic system is available on the ABB web-
site (http://stringsizer.abb.com).
I
nverter block diagram
This string inverter converts the direct current from a single PV array into
alternating current, and feeds it into the elecrical distribution grid.
This conversion, known as inversion from DC to AC, is done in efficiently,
and electronically, without rotating machinery.
When connected in parallel with the grid, the alternating current from
the inverter flows directly into a domestic or industrial distribution circuit,
which is in turn connected to the public distribution grid.
The inverter automatically reduces the power fed into the grid under ad-
verse environmental conditions, such as high temperature, unsuitable
input voltages or grid instability.
Multiple inverters may be used at large-capacity sites. Each inverter must
have its own individual PV array input, and on the AC side, and its own
AC disconnect to the grid.
Each inverter will work independently from the others and will supply the
grid with the maximum power available from its section of photovoltaic
panels.
Decisions on how to design a photovoltaic system depend on a number
of factors, such as the type of panels, the space available, the location of
the system, energy production goals, choice of inverter, etc.
The diagram shows the internal structure of the inverter. It has two stages:
- DC/DC input converter (boost)
- DC-AC output inverter
The DC-DC converter and the DC-AC inverter work at high switching
frequencies, and are small and relatively light.
The converter input has maximum power point tracking (MPPT) to opti-
mize energy production.
The inverter has no internal isolation transformer (no gavlanic insula-
tion between input and output), which reduces weight and increases effi-
ciency. It has all protection necessary for safe operation and compliance
with safety stanards.
The inverter's operation and management of its protection features are
controlled by two independent digital signal processors (DSP) and a cen-
tral microprocessor. The connection to the grid is thus controlled by two
independent computers, in full compliance with requirements for connec-
tion to to the grid, and for safe and secure operation.
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2 - Characteristics