IEEE Power Electronics Magazine - June 2022 - 64

1) Controlled power exchange between microgrids through
the SST as reverse power flow is possible.
2) High degree of controllability of voltages, currents,
power flows.
3) Power transfer between the phases within a microgrid is
possible as the SST has a dc interface.
4) SST has a much faster response compared to a transformer
and can be controlled to limit fault current and
for fault isolation. This leads to a robust smart LVDS.
5) The ability of SSTs to control power flow can be used to
implement energy budgeting between microgrids during
disasters and extreme events.
The SST can also facilitate ancillary grid services
such as reactive power support, harmonic mitigation,
sag mitigation and short-circuit protection, and dc
Dual Active Bridge
3 F
HV
HV Side
Converter
HF
DC-AC
HF Link
FIG 4 Basic block diagram of a solid-state transformer.
Microgrid #1
SST
Substation
Microgrid #2
SST
Microgrid #3
SST
FIG 5 SST as building blocks to make the existing LVDS smart.
HF
AC-DC
LV Side
Converter
3 F
LV
connectivity. However, the development of SST technology
is limited due to the unavailability of switching
devices in the voltage range of 13 kV. Issues such
as implementation, control, protection, reliability, and
isolation are still to be addressed. SST is an evolving
technology and its cost as well as operational comparison
to a commercially available power transformer is a
valid concern. Over the years, SST has seen significant
augmentations in features, operation, and efficiency.
For example, an SST from GE is reported to have 99.2%
peak efficiency at 60 kW power level [11]. With gradual
innovation and technological advancements, the cost of
SST will go down and performance will be better. Some
other challenges of SST in LVDS will include protection
co-ordination with existing relays.
SST: A Smart Homes Enabler
To enable the smart home compatible with
demand side management (DMS), some
non-essential loads can be interfaced to the
grid using solid-state relays (SSRs). This
will allow independent control of these
loads by a central microgrid controller,
which also dictates the operation of SST.
However, critical and essential loads can
still be interfaced to the LVDS/microgrid
using miniature circuit breakers (MCBs) or
fuses. Figure 6 shows a smart home architecture
supplied from an SST which
enables these features. Renewable power
can support critical loads. Apart from supplying
home loads, the power electronics
in the smart home will be responsible for
power exchange within the microgrid,
energy arbitrage, and reactive power support.
Instead of connecting the home
directly to the power lines, a power electronic
router such as PINE can be
employed [12]. The power electronic
SST
Microgrid
SSR
SSR
Microgrid
Controller
Critical
Loads
Non-Critical
Loads
Critical
Loads
: MCB SSR: Solid State Relay
FIG 6 Architecture of smart homes in SST interfaced smart LVDS.
64 IEEE POWER ELECTRONICS MAGAZINE z June 2022
Non-Critical
Loads
SSR
Non-Critical
Loads
Critical
Loads
Communication Link
m-Inverter
IEEE Power Electronics Magazine - June 2022

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