Outcomes, Insights, and Best Practices from IIC Testbeds: Microgrid Testbed
R ESULTS to as the point of common coupling.
Many companies are putting work into
testbeds and they get to learn about
adjacent technologies. This in turn makes
vendors better suited to deliver technology
components that can fit into a complete
solution. For the eventual end user, the
testbeds are reducing integration risk and
speeding time-to-market for many of these
technologies – helping to drive business
results through innovation. The next three cabinets are the testbed’s
inverter cabinets. They have a 50-kilowatt
power stack from a company called
SEMIKRON®.
These
are
grid-scale
components though they are not pushing 50
kilowatts through them. Real equipment is
closer to grid ready and is important for both
development and demonstration to utility
professionals. Those power stacks are
controlled by a CompactRIO edge controller
from National Instruments. Because that
specific model of CompactRIO has TSN
capability, the testbed team can synchronize
the control routines across the three
cabinets. The controllers have an Intel®
multi-core Atom processor and a Xilinx®
field-programmable gate array (FPGA) that
form the processing base for the control
algorithm.
Lab Environment
In the lab, the testbed team can run a
functioning, low-voltage (for safety) grid that
can disconnect from the local three-phase
power outlet of the grid and run in island
mode with no synchronous generation. That
scenario is using the TSN technology, but it
also requires some control theory. Specific
resources, as mentioned earlier, are needed
here. Some of the in-house expertise
includes people who have worked on control
algorithms to run inverter controls, running
the insulated-gate bipolar transistors (IGBTs)
that are part of an inverter and
synchronizing with the adjacent inverters.
The final cabinet in the row of five is the
“load cabinet.” A microgrid requires load
and this cabinet was built to automatically or
remotely control the basic types of loads:
lights, a motor, resistive heaters, etc. The
testbed has all of those in the load cabinet to
be switched on or off as needed.
The testbed team worked with an
integration partner, Viewpoint Systems, to
build out what the team refers to as the five
“core cabinets.” These cabinets are
somewhat
portable
and
contain
instrumentation for microgrid setup.
Cisco switches connect all of the
CompactRIOs in all of the cabinets together.
TSN systems need compatible edge nodes
and IT infrastructure to work. It is easy to talk
about interoperability and being able to
have plug-and-play or interoperability
messages, but like the earlier conversation
about the network stack, it is not as easy as
plugging a cable into Box A and into Box B
and then they can talk. There are so many
layers of technologies involved that even
experts on the testbed are continuing to
learn.
The first in the line of daisy-chained cabinets
is the “Main Grid” cabinet that connects to
the 3-phase 208VAC in the lab and uses
transformers to drop the voltage to a safer
voltage below 24VAC. This cabinet also has a
built in switch/relay that is used to connect
or disconnect the microgrid from wall
power. On an actual microgrid connected to
a controlled network, this would be referred
- 36 -
September 2017