Atec ETS User Manual
Elgar ETS TerraSAS
1kW-1MW
Standalone TerraSAS Photovoltaic Simulator
• Low output capacitance
• High bandwidth up to 30kHz
• High resolution I-V curve simulates static and
dynamic conditions
• Designed for high speed Maximum Power Point
Tracking (MPPT)
• Can be integrated into a multi-channel system for
higher power testing
• Energy Harvest and Oscilloscope measurements
built in. *
• Low voltage, high bandwidth version for DC Power
Optimizers
For microgrids, energy storage, and inverter test
applications, the TerraSAS™ series photovoltaic
(PV) simulators are specically designed to
emulate the dynamic electrical behavior of a
terrestrial PV solar array. They offer low output
capacitance and high closed loop bandwidth to
keep up with the advanced Maximum Power
Point Tracking (MPPT) algorithms used in today’s
grid-tied inverters.
The Embedded TerraSAS (ETS) is a high
performance solution in a small form factor
that combines an agile power supply with
an innovative I-V curve generator in a single
standalone unit.
• ETS 600 / 1000: For isolated and non-isolated
string inverters up to 1000Vdc Voc.
• ETS 60 / 80 / 150: For use with micro-inverters
or DC optimizers up to 150Vdc Voc
Application
Many solar inverters generate AC ripple on their
DC input, which is connected to the photovoltaic
array. For single phase inverters, the frequency
of this ripple is twice the line frequency (120 Hz
for US models). The simulator’s power supplies
must not suppress this ripple as a function of
their regulation loop. An increasing number
of inverters (and virtually all micro-inverters)
accurately measure amplitude and phase of the
ripple voltage and current to quickly track the
MPP of the array. This approach allows tracking
the MPP at a much higher speed when compared
to conventional dithering techniques (also called
perturbate-and-observe). Faster tracking of the
MPP results in a much higher overall efciency
in cloudy conditions, where the irradiance is
constantly changing. It is likely that all solar
inverters will use this approach in the near future,
since end users are very sensitive to the overall
efciency of their solar energy installations. To
satisfy this requirement, the PV simulator must
be capable of reproducing the voltage / current
behavior of a solar array at the ripple frequency.
Most standard switching power supplies employ
very large output capacitors and inductors in
their output circuits and are unable to deliver the
required performance - regardless of the response
speed of the I-V curve controller. Elgar’s TerraSAS
line of PV simulators are based on high speed
versions of our standard products, where output
capacitors and other speed-limiting components
have been adjusted. This results in a speed
improvement of 10 times or better.
Proprietary features built into the PV controller
hardware and rmware, combined with our
high speed power supplies, deliver the required
performance. This technology was extensively
tested on micro-inverters and is ready to test
the next generation of inverters. The required
performance is delivered by high speed switching
power supplies and advanced Digital Signal
Processing techniques. In some conditions
traditional DC power sources using IGBT
technology do not meet MPPT response speed
requirements, depending on the MPPT principles.
Our power supplies use Power MOSFETs,
which typically switch ten times as fast as the
most recent IGBTs. Higher switching frequency
translates to smaller output capacitors and
inductors - which is the key to a successful high
speed power supply design
60-1000 V
208 400 480
115
AMETEK
Programmable Power
9250 Brown Deer Road
San Diego, CA 92121-2267
USA
* - Available Q4 2013
858.458.0223
sales.ppd@ametek.com
10252013
291
ETS TerraSAS
Product Overview
The ETS series standalone TerraSAS consists
of a high performance, programmable DC
power supply with control software and GUI
interface, output isolation, and a unique PV
simulation engine that provides the I-V curve.
This combination of hardware, software, and
rmware allows the TerraSAS to simulate test
protocols or combinations of events that a realworld solar installation will be subjected to.
The included software allows modeling of a PV
panel without an extensive knowledge of solar
array parameters. The only parameters required
for a simulation are the open circuit voltage (Voc),
short circuit current (Isc), and the peak power
parameters Vmp and Imp. Changes to these
parameters allow the shape of the I-V curve to be
adapted to any ll factor between 0.5 and 0.95.
Once an I-V curve has been generated, changes
to the irradiation level or temperature can be
modied on the y to test the behavior of a
grid tied inverter under realistic conditions for
cloud shadowing and panel temperature rise.
Long term weather simulations can be loaded
and run to determine the amount of energy
harvest delivered in a given situation. Inverter
designers use these accuracy and efciency tests
to optimize real MPP search modes.
Scalability
Power supplies are available in 850W, 5kW,
10kW, and 15KW increments. The 80V units
are available in two power levels: 1200W
for microinverters and 850W for the latest
generation microinverters and DC power
optimizers. The bandwidth on the 850W version
has been improved to 30kHz by adding a linear
regulation output stage. 600V units are available
in 5kW, 10kW, and 15kW versions depending on
Isc requirements. 1000V units are rated 10kW.
All versions are easily connected in parallel to
scale output power up to handle microinverters,
string inverters, and even utility scale inverters.
Many models can also be connected in series to
handle higher voltage tests. Please refer to the
connection diagrams located in the User Manual
and follow appropriate wiring codes before
connecting ETS PV simulators in series or parallel.
Real time I-V curve display
The Elgar Real time I-V curve display is updated
20 times per second to illustrate dynamic inverter
behavior (operating point and sweep amplitude).
Compared to other commercially available solar
array simulators with an update rate of only 1Hz,
this allows more accurate analysis of the inverter’s
actual MPP tracking ability.
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