IEEE Electrification - September 2020 - 94

These devices
accurately emulate
the effects of
switching transients
and electromagnetic
transients on a
microgrid.

decision-making architectures-centralized, decentralized, and distributed. The cyber layer also includes
equipment that emulates the topology and operations of a microgrid's
underlying communication infrastructure. The cyber-layer components monitor the states of the
microgrid, e.g., voltages, frequency,
and active and reactive power injections, and use this information to initiate appropriate coordination and
control actions within the physical
layer. Such a closed-loop operation
between the physical and cyber layer emulates the realtime behavior of a microgrid and allows for high-fidelity
testing of the various control architectures.

Physical-Layer Infrastructure
The physical layer in our testbed is composed of a
Typhoon HIL real-time simulator and Open Distribution
System Simulator (OpenDSS). The lower-level control
schemes for each generator source are synthesized on a

(a)

Texas Instruments (TI) hardware control platform.

Typhoon HIL Hardware

The Illinois C-HIL testbed is currently
equipped with three ultrahigh-fidelity
real-time simulation hardware devices: one Typhoon HIL 402 and two
Typhoon HIL 603s (see Figure 2). By
allowing real-time simulation step
sizes as low as 0.5 µs and pulsewidth
modulation sampling of 20 ns and
implementing very detailed models of
system components, these devices
accurately emulate the effects of switching transients and
electromagnetic transients on a microgrid. We have also
implemented reduced-order models of the DERs, loads,
and the network on the Typhoon HIL devices to reduce the
modeling complexity and, as a result, lower the computational cost of emulating a large system.

OpenDSS Software
The testbed also utilizes software developed by the Electric Power Research Institute called OpenDSS along with
the Typhoon HIL simulators. We utilize the OpenDSS
software in our C-HIL testbed because of its capacity to
emulate large distribution networks, adaptability for
cosimulation, high usability, and the large number of publicly available power distribution network models. In the
Illinois C-HIL testbed, the OpenDSS software is executed
on an off-the-shelf desktop computer.

Lower-Level Control Platform
(b)
Figure 2. The (a) Typhoon 402 and (b) Typhoon 604.

(a)

(b)

I E E E E l e c t r i f i cati o n M agaz ine / SEPTEMBER 2020

Based on the state of operations within the emulated
system, the cyber layer sends out the appropriate control actions for the controllable DERs and loads in the
physical layer. These control actions are then carried
out by the lower-level controllers. The Typhoon HIL realtime emulator can be used to model the lower-level
controllers for the generator sources. However, our
C-HIL testbed is also equipped with multiple TI MSPEXP432e401y Ethernet boards for the implementation
of lower-level DER control schemes. Such schemes
include governor control, frequency droop control, voltage droop control, and virtual oscillator control. The
C-HIL testbed consists of 100 such devices stacked up in
10 metal cabinets (see Figure 3).

Cyber-Layer Infrastructure
The cyber layer in our testbed is composed of microcontroller-based control nodes that allow the emulation of
centralized, decentralized, and distributed control architectures. In addition, the cyber layer includes the communication infrastructure needed for secure monitoring of
the system emulated in the physical layer as well as the
relaying of control commands to individual DERs.

IEEE Electrification - September 2020

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