IEEE PES T&D Conference & Exposition 2022 - 78

Smart Wires reviewed the model to verify that it offered an
equivalent representation of the M-SSSC device performance
during normal system loading variations and power-system
transient conditions. The team concurred that the model was
a valid representation of the characteristics of the devices
for the real-time simulator test environment. The simulation
validated the rapid bypass capability of the M-SSSC devices
to remove the deployment from the Leeds-Hurley line faster
than the Hurley Avenue relays could assert. This meant Central
Hudson would not require relay upgrades to support the
21% series compensation.
Central Hudson was also concerned with SSR and
SSCI, which occur when contingencies result in a generation
resource radially connected to a series compensated
line. This condition can result in severe oscillations at frequencies
below the fundamental (<60 Hz). However, various
system studies have verified that SSSC technology
avoids SSR. Results from a study completed by EnerNex,
a consulting firm, demonstrate the avoidance of SSR.
In the M-SSSC devices, a phase locked loop generates a
stepped pulse sinusoidal voltage signal mainly at the fundamental
frequency and independently from the line current.
This scheme, validated in multiple academic papers
and textbooks on flexible alternating current transmission
system devices, ensures that SSSCs do not impact SSR/
SSCI. Figure 3 shows how a simulated series of faults
results in an SSR event at a nearby generator unit using
an FSC solution and an M-SSSC solution. When simulating
the response with an M-SSSC solution, the system
responds to the events as expected.
The risk of damage to generators and control systems
via SSR with FSCs means that utilities typically expend
significant resources on studies and mitigation. The
M-SSSC solution provides series compensation without
SSR risk.
M-SSSC solutions offer granular, real-time power flow
control. These devices can change line reactance on a subsecond
basis, and there are no maintenance costs associated
with frequent switching. This feature allows M-SSSC solutions
to optimize power flows under various system conditions
that may require increasing line reactance. This level
of control is not possible with FSCs. It can be particularly
valuable to help integrate renewable generation, which is
relevant in New York State due to solar and wind generation
growth in the northern part of the state and upcoming
offshore wind projects in the southern part of the state.
As changes in generation and load occur at an increasing
rate, the need for flexible and rapidly deployable solutions
increases. The modular design of M-SSSC deployments
ensures an investment for Central Hudson that pays
for itself at the Leeds-Hurley site and provides outsized
return with potential use at future locations, representing
a highly efficient use of customer dollars. M-SSSC devices
can be commissioned less than one year from contract
execution, allowing utilities to capture benefits earlier,
thus improving the cost-benefit ratio. In contrast, FSCs are
custom-built for a specific voltage and MVA rating and are
rarely economically attractive to scale or move. They also
typically require more than 12 months from purchase
to installation.
Fixed Series Capacitor (FSC)
1,000
800
600
400
200
9.8
800
600
400
200
9.8
10
10.2
10.4
10.6
10.8
Time (s)
Modular Static Synchronous Series Compensator (M-SSSC)
Pe_SM2 at Machine
11
11.2
11.4
11.6
11.8
Pe_SM1 at Machine
10
10.2
10.4
10.6
10.8
Time (s)
figure 3. Response Showing FSC SSR Activity And Avoidance Of Such Activity With M-SSSC Device.
78
ieee power & energy magazine
April 2022 Show Issue
11
11.2
11.4
11.6
11.8
Power (MW)
SM1 Real Power (MW)

IEEE PES T&D Conference & Exposition 2022

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